Holotype—CM 963, two vertebrae, cervical rib, dorsal rib, fragments of dorsal ribs, pubis, 27 complete or nearly complete osteoderms, and several dozen fragments likely from the vertebrae, ribs, and skull (Figs. 2–4).

Occurrence—Judith River Formation, middle Campanian, Late Cretaceous, three miles west of Nolan and Archer's ranch along the Willow Creek, Fergus County, Montana, U.S.A.

Referable Specimens—None.

Diagnosis—“Great size, exceeding that of any other representative of the Crocodilia thus far described from North America. Scutes massive and possessing great vertical height in comparison with their breadth, many of the smaller scutes being almost hemispherical, and some of the smallest subglobose. Pubis straighter and less deeply excavated posteriorly than in recent Crocodilia Extremities of dorsal spines of vertebrae broad transversely and thickened for attachments, much more than in existing genera. The postzygapophyses of the vertebrae more nearly on the same plane as the transverse processes and not looking outwardly as much as in other crocodiles” (Holland, 1909:282). Additionally, the osteoderms of the lateral margin of the dorsal shield preserve indentations along a single edge.

Description—Some elements indicated by Holland (1909) are missing. Historically, the atlantal rib, pubis, and several hundred indeterminate fragments were preserved. Missing elements were coded into the matrix using figures from Holland (1909). Currently, the atlantal rib, pubis, and most of the indeterminate fragments are missing. The collections manager at CM (A. Henrici, pers. comm.) indicates that they were lost long ago.

The most striking feature of the specimen is its incredible size. Preserved elements shared with other species of Deinosuchus may be compared to indicate relative sizes. Osteoderms and vertebrae indicate that CM 963 is among the largest individuals of all species previously attributed to Deinosuchus, although some of the largest D. riograndensis specimens approach or equal its immense size.

Two very large dorsal vertebrae are preserved; they are procoelous and preserve long transverse processes and neural spines (Fig. 2). The neural spines end in a dorsally flat, mediolaterally expanded tuberosity, likely for the attachment of epaxial musculature. As indicated by Holland (1909), the postzygapophyses are nearly on the same plane as the transverse processes.

The most complete vertebra was determined by Holland (1909) to be the seventh in the dorsal series. Comparison with modern taxa indicates that the vertebra was likely between positions 6 and 10 in the thoracic series. The element is nearly complete save the right transverse process. The left transverse process bears attachment sites for the dorsal ribs and establishes the identity of the vertebra as belonging to the dorsal series. The neural spine is very long and ends in a large flattened tuberosity. The less complete of the two vertebrae was tentatively assigned by Holland (1909) as the last vertebra of the lumbar series. The authors agree that the vertebra is part of the lumbar series but do not assign a position. This vertebra preserves a left transverse process; the right side is missing. Both the transverse process and neural spines are shorter than those of the thoracic vertebra. In addition, the transverse process is narrow relative to the thoracic vertebra. The extremity of the neural spine is largely incomplete, but proportions of preserved bone indicate that it was mediolaterally expanded.

A complete left dorsal rib is preserved (Fig. 3). Additionally, one midshaft, three proximal, and four distal rib fragments are present; they likely represent dorsal ribs as indicated by size, proportion, and preserved morphology.

Thirty-seven osteoderms, in various states of completeness, are preserved (Fig. 4). Elements of the nuchal, dorsal, and sacrocaudal shields are preserved. Most osteoderms are deeply pitted with inflated parasagittal keels—the result is an osteoderm that is lumpy in appearance when viewed anteriorly or posteriorly. Some osteoderms, presumably postoccipitals or the superior-most osteoderms of the lateral shield along the animal's flank, are subglobose—pitting is highly reduced in these elements, with one preserving no pitting whatsoever. Striations intersecting at 45° angles and approximating the shape of a chevron cover the ventral surfaces; this morphology is especially evident in dorsal shield osteoderms. Comparison with Alligator mississippiensis indicates that the striations are surface markings for tendinous deep fascia connecting to the underlying epaxial musculature (Seidel, 1979). Some osteoderms show indentations along a single margin, presumably indicating contact with a neighboring osteoderm. These osteoderms are tentatively identified as belonging to the lateral margin of the dorsal shield.

Holotype—AMNH 3073 (Figs. 7–11), premaxillae and part of a right maxilla, portions of the left articular, angular, and surangular, left and right splenials and dentaries, six loose teeth, one thoracic vertebra (tentatively the 12th vertebra of the presacral series), right scapula, a possible portion of a superior right ilium, as well as osteoderms and other indeterminate fragments. The International Commission of Zoological Nomenclature will be petitioned to change the type species of Deinosuchus to Deinosuchus riograndensis.

Occurrence—Campanian, Late Cretaceous, Aguja Formation west of Glenn Spring, Big Bend National Park, Brewster County, Texas, U.S.A.

Referable Specimens—TMM 40571-1 (Fig. S2) consists of the left side of an upper jaw and left hemimandible from Brewster County, Texas, U.S.A. TMM 43538-1 (Fig. S3) consists of the left side of a skull from Brewster County, Texas, U.S.A. TMM 43620-1 (Figs. 12, 13A, 16, 18, S4, S5) consists of a skull, mandible, and postcranial elements from Brewster County, Texas, U.S.A. TMM 43632-1 (Figs. 13C, 14, 15, 17, 19) consists of a skull, lower jaw, and postcranial elements from Brewster County, Texas, U.S.A.

Diagnosis—“A eusuchian crocodile of tremendous size, the lower jaw being about 1800 mm (approximately 6 feet) in length. The bones of the skull and lower jaw are heavy and the teeth are robust. In each premaxilla there is a large fenestra lateral to the external narial opening—a distinctive feature not seen in any other known crocodilian. The single known vertebra is strongly procoelous. The broad scapula indicates that the limbs may have been comparatively heavy. Scutes very heavy” (Colbert and Bird, 1954:13).

Amended Diagnosis—Bulbous premaxillae bear large, dorsally displaced fenestrae anterolateral to the bony narial aperture; bony narial aperture opens posterodorsally and is wider than long; shallow occlusal marks present on the premaxilla between the first and second alveoli and lingual to the third and fourth alveoli; premaxilla-maxilla notch is posteromedial to the fifth premaxillary tooth; anterior margin of suborbital fenestra acute and extends to the posterior margin of the 12th maxillary alveolus from the end of the tooth row; ophthalmic groove trends anteroposteriorly; osteoderms are very large and bear inflated parasagittal keels.

Description

Deinosuchus riograndensis AMNH 3073 represents a very large alligatoroid from the Campanian Aguja Formation of the Big Bend region of Texas. It was discovered in 1940 by an expedition of the American Museum of Natural History and excavated by Barnum Brown and Roland Bird.

Many bones are adequately preserved, but others such as the premaxillae are composed of many cracked pieces held together by plaster. Often, bones that are proximal to one another, such as the articular and the surangular, do not fit together. The intervening bone is missing either as a product of diagenesis or a result of the fossil preparation process.

Premaxilla—The premaxillae are very large and particularly deep relative to their length and width (Fig. 7). AMNH 3073 has the largest and most bulbous premaxillae of all specimens referred to species of Deinosuchus. The elements do not fit together; it is unknown whether this is due to diagenesis or as a result of preparation. The edges of the premaxillae, especially along the dorsal midline and the dorsal premaxillary processes, are smooth and indicate that the polished edges may have been created via preparation of the specimen.

The anterior and anterolateral margins of the external naris are formed by the premaxillae. The margins of the bony narial aperture are smooth; considerable breakage and reconstruction is present along the margins formed by the premaxilla. Preserved portions of the bony narial aperture on the premaxillae and the maxillary fragment suggest that the aperture opened posterodorsally.

The dorsal processes of the premaxillae are short relative to the large size of the elements. Their posterior extent comes to a blunt point when viewed from a lateral aspect. Colbert and Bird (1954:6) describe the dorsal processes of the premaxillae as “… barely reaching back to the level of the space between the first and second maxillary teeth, for which reason they embrace only the anterior border of the external nares.” Additional D. riograndensis specimens from Texas agree with this assertion, but at the time of their description this could not be verified; the right premaxilla does not fit with the maxillary fragment because there is bone missing between the elements. Laterally, the dorsal processes would have wrapped around the posterior of the dome-like anterior-most snout. However, as isolated elements, this interpretation is dependent on how the premaxillae are posed; comparisons with more complete specimens indicate that this is the case.

Undocumented among eusuchians is the presence of large fenestrae anterolateral to the bony narial aperture. The extreme depth of the premaxillae, dorsal placement of the fenestrae, and lack of holes in the palatal processes of the premaxillae suggest that they were not for receiving the first dentary teeth as is found in modern forms such as Caiman crocodilus. This feature is preserved in both premaxillae, but the margins of the fenestrae are incomplete; in life, they were likely somewhat smaller than currently preserved.

The fenestrae lead to an internal hollow space within the premaxillae and appear to have connected with a paranasal air sinus in the interior of the element. The anterior wall of the premaxilla bears a dorsoventrally oriented, mediolaterally thin ridge extending from the roof of the element to the middle of the anterior wall (Fig. 7I). It is approximately 3 cm long and projects posteriorly into the hollow of the premaxilla. Although likely, it is unknown whether the feature extended further to the posterior to form a wall separating the nasal passage from the paranasal air sinus.

There are large bumps on the floor of the premaxillary cavity where the roots of the premaxillary teeth are encased in bone. The bone forming the floor of the external naris is not preserved; the incisive foramen is missing.

Each premaxilla preserves five closely spaced alveoli. Alveoli 1–3 get progressively larger from mesial to distal, the third and fourth are large, and the fifth is the smallest among the premaxillary arcade. The largest alveolus in the left premaxilla is the third, but the third and fourth alveoli are approximately the same size on the right side. A pronounced difference in the amount of bone separating the third and fourth alveoli among the premaxillae is present; the left side preserves more intervening bone. It is unknown whether these differences are pathological, taphonomic, normal morphological variation, or the result of preparation. The fifth alveolar position of the left premaxilla preserves a partially broken crown of an erupting tooth. Posterior to the fifth alveolus is a large notch for receiving the third and fourth dentary teeth, as is present in the alligatoroid Leidyosuchus canadensis Lambe, 1907.

Maxilla—The anterior portion of the right maxilla is preserved (Fig. 8). Its lateral margin is complete; the medial margin is damaged. Sutural contacts between the right premaxilla and maxilla fragments are missing. However, the outline of their margins in dorsal and lateral views suggests that they were nearly contiguous. The anterior end of the maxillary fragment bears a large dorsal inflation. Medial to the inflation, the bone has been destroyed; preserved portions indicate that the maxilla contributes to the nasal canal and the posterolateral margin of the bony narial aperture.

Six alveoli and part of a seventh are preserved on the maxillary fragment (Fig. 8E). The identities of the alveoli are unknown, but comparison with referred specimen TMM 43620-1, a nearly complete D. riograndensis skull from the holotype locality, suggests that the fragment preserves maxillary alveoli 1–7. Alveoli in positions 3, 4, and 6 preserve teeth. The tooth in the third alveolus is very large and robust; it is anteroposteriorly compressed and bears a lengthwise groove on its distal side. The fourth and sixth alveoli contain partially erupted teeth. The maxilla is laterally expanded in the region of the first to seventh alveoli. Lingual to the sixth alveolus are indentations for receiving the teeth of the mandible. The taxon had an overbite in this region.

Colbert and Bird (1954) suggest that a fragment of the right nasal is attached to the maxillary fragment and the nasals are broad. However, the nasal fragment is not evident. Comparison with more complete specimens indicates that a nasal may be present in this region.

When viewed from a posterior aspect, the maxilla fragment preserves a matrix-filled cavity lateral to the nasal passage interpreted as a paranasal air sinus. Additionally, a moderately deep, ‘U'-shaped indentation is present ventral to the paranasal sinus. Colbert and Bird (1954) suggest that this indentation is the anterior-most margin of the suborbital fenestra and that it is unexpectedly positioned to the extreme anterior of what is usually encountered in crocodylians. However, when viewed ventrally, the anterior margins of most crocodylian suborbital fenestrae give way to an open space occupied by the adductor muscles. In AMNH 3073, the anterior of the proposed suborbital fenestra has a bony floor. Comparison with more complete specimens (TMM 40571-1, TMM 43538-1, TMM 43620-1, TMM 45973-1) indicates that this feature cannot be related to the suborbital fenestra due to its unusual morphology and its extreme anterior placement.

Dentary—The anterior-most portions of the dentaries are preserved (Fig. 9). The right dentary preserves alveoli 1–7. Alveoli 1–6 are complete and preserve teeth. The floor of the first alveolus, along with the deeper walls of the second alveolus, is preserved. Apically, the first tooth curves toward the midline, likely as a result of deformation during burial; preserved alveolar margins suggest that in life the tooth projected somewhat laterally away from the midline. Along the midline is a space separating the first teeth of the hemimandibles; these teeth would have occluded with the premaxillae behind the space for the first and second premaxillary teeth. The alveoli for teeth 3 and 4 are confluent on the right side; the teeth themselves lie next to one another with moderate and slight anteroposterior compression of teeth 3 and 4, respectively. This condition is not present on the left side where the alveoli are widely spaced, and no teeth are present (Fig. 9A). Differences in morphology may be a product of taphonomy, pathology, or normal variation. When present, enamel on the teeth is thick. The mandibular symphysis extends posteriorly to the space between the fourth and fifth dentary teeth when viewed dorsally.

The left dentary fragment has spaces for seven alveoli; the posterior portion of the seventh alveolus is missing. Teeth are present in alveoli 3, 6, and 7. The left fragment shows that the splenial reaches the symphysis. The sutural portion of the dentary symphysis encloses an anterior projection of the splenial that cannot be viewed unless the hemimandibles are separated (Fig. 9E). The anterior projection of the splenial extends for no more than one alveolus length (stops before the position of the third alveolus). The left side suggests a splenial that thins dorsoventrally as it proceeds to its anterior-most extent.

A large left dentary fragment preserves two teeth (Fig. 10L–N). Curvature of the lateral side of the fragment suggests that it came from the mid-jaw region of the mandible. The medial portion is not preserved. The fragment is contiguous with the left dentary fragment containing the symphysis. There are large, deep pits on the lateral side for the passage of nerves and blood vessels. No discernible alveoli are present save one that bears a tooth that is missing its crown, is nearly round in cross-section, and has very thick enamel. Deep in the mandible, ventral to the erupted tooth, is a developing tooth.

Colbert and Bird (1954) suggest that nine alveoli are preserved on the left side of the mandible, but there is no evidence for discernible alveoli beyond the anterior portion of the seventh in the anterior fragment and a single alveolus in the mid-jaw fragment.

Angular—Both angulars are preserved (Fig. 10I–K). Medially, the mandibular fossa and posterior margin of the foramen intermandibularis caudalis are preserved. The mandibular fossa is extensive anteroposteriorly and mediolaterally for the accommodation of presumably large m. adductor mandibulae externus posterior and m. intramandibularis necessary in order to close the massive jaws. The medial side of the left angular preserves sutural scars where the element likely contacted the splenial, which itself may have extended posteriorly to the anterior margin of the foramen intermandibularis caudalis.

Surangular—The posterior portion of the left mandible preserves the surangular (Fig. 10 D–H). At the point of the glenoid fossa, there is a lateral expansion of the surangular, producing a swelling along the dorsolateral portion of the posterior mandible. An anteroposteriorly oriented groove is present on the dorsal side, confluent with the swollen region of the surangular (Fig. 10F). This portion of the element does not contact the articular fragment bearing the posterior wall of the glenoid fossa. The ascending ramus of the left surangular, forming the lateral face of the retroarticular process, is preserved and fits into a groove on the lateral side of the left articular.

Articular—A partial left articular preserves the retroarticular process and the posterior wall of the glenoid fossa; anteroventral portions of the articular are not preserved (Fig. 10A–C). The ridge forming the posterior wall of the glenoid fossa does not bear signs of the foramen aereum. Although incompletely preserved, sutural scars on the lateral side of the articular suggest that the surangular and angular may have extended to the dorsal-most tip of the retroarticular process.

Teeth—Six loose teeth are preserved (Fig. 10O), but it is of note that seven teeth are figured by Colbert and Bird (1954). Associated notes from the AMNH reconstruction suggest that they are left dentary teeth 2, 3, 5, and 6 as well as right dentary teeth 2 and 8, but this suggestion cannot be verified. The best-preserved teeth demonstrate modest mesiodistal carinae. Distal to the second and third teeth, crowns get progressively lower and less dagger-like. The dagger-like and low-crowned teeth likely functioned for holding (or tearing) and crushing, respectively (Erickson et al., 2003, 2012).

Postcrania—Postcranial elements consist of a single dorsal vertebra, right scapula, a possible fragment of a dorsal right ilium (Fig. 11), and osteoderms. Colbert and Bird (1954) suggest that the strongly procoelous dorsal vertebra is the 12th or 13th in the presacral series because both rib articulations are present on the transverse process, articular surfaces on the centrum are absent, and the centrum has a ventral keel (Fig. 11D–G). The vertebra is well preserved save the right transverse process and neural spine, which are missing. The left transverse process has been displaced by crushing and is bent superiorly where it contacts the intersection of the left pedicle and lamina. The scapula is shorter than expected for such a large animal and is very robust (Fig. 11B, C). The articular end of the element is less flared, and constriction of the neck is reduced relative to extant alligatorids. The result of this morphology is an articular end that gently grades into the inferior portion of the scapular blade. The margins of the inferior two-thirds of the blade are nearly parallel. The superior third of the blade is strongly flared. A partial right ilium demonstrates that the element was very robust (Fig. 11A).

TMM 43620-1 and Associated Material

This specimen (Figs. 12, 13A, 16, 18, S4, S5) represents a very large individual from the Big Bend region of western Texas. It is similar in size to the AMNH holotype specimen and is the most complete cranial specimen known for any species of Deinosuchus. Preservation is via calcium carbonate salts (Schwimmer, 2002); extensive cracking is present, and sutures are difficult to discern.

Premaxilla—Both premaxillae are preserved (Figs. 12A, B, 13A, S4). Although some dorsoventral crushing is present, the amount of compressed bone in the region suggests that they were as bulbous as the AMNH holotype specimen. When viewed laterally, the premaxillary region is the deepest portion of the anterior snout. The anterior margin of the bony narial aperture, formed by the premaxilla, would have been situated dorsal to the posterior margin formed by the maxilla and nasals; the bony narial aperture opens posterodorsally and is mediolaterally wider than it is anteroposteriorly long.

Premaxillary fenestrae are preserved (Fig. 12F). Relative to the holotype (AMNH 3073), they are more immediately proximal to the tooth row. This variation in morphology is likely due to crushing in TMM 43620-1. The dorsal processes of the premaxillae are poorly preserved. However, the anterodorsal maxilla preserves marks where it contacts the dorsal processes of the premaxillae and indicates that they are short and extend to the posterior margin of the bony narial aperture. The dorsolateral margins of the bony narial aperture are formed by the premaxillae.

Ventrally, the premaxillae each preserve five alveoli—the first two alveolar positions are small and nearly equal in size, the third position is the largest, the fourth position is nearly as large as the third, and the fifth is the smallest among the premaxillary dental arcade. All premaxillary teeth are preserved, although the crowns are missing. The first and second premaxillary alveoli are separated by marks that were likely formed through occlusal contact with the first dentary teeth. These features are relatively shallow and are nearly equal to the diameters of the alveoli they separate.

Very shallow occlusal marks are present medial to the junction of the third and fourth alveoli; they were likely formed by the second dentary tooth. TMM 40571-1 (Fig. S2), a smaller individual from the same unit, may demonstrate similar morphology. The incisive foramen is small, mediolaterally narrow, shaped like a teardrop, and extends anteroposteriorly from the fourth premaxillary alveolus to the level of the posterior margin of the premaxillary-maxillary notch (Fig. 12B). Ventrally, the premaxilla is mediolaterally constricted at the point of the notch. The posterior premaxillary margin on the ventral surface of the snout is suggested by faint sutures and separation of bone—it extends to the anterior margin of the third maxillary tooth.

A large notch for reception of the third and fourth dentary teeth during occlusion is present at the point of premaxillomaxillary contact. The effect of this morphology is a mediolateral constriction of the snout at the juncture of the premaxilla and maxilla. The anterior and medial margins, as well as the anterior roof of the notch, are composed of the premaxilla. The posterior margin and roof are formed by the maxilla. Tooth crowns would have been covered by the roof of the notch formed by the maxilla.

Nasal—Nasals are broad along the length of the snout and are particularly wide at their anterior-most extent. Sutural margins are obscured at points, but the general outline is confidently determined (Fig. 12A). As preserved, the anterior tips of the nasals form a blunt point along the midline where they contribute to the posterior margin of the bony narial aperture, but it is unknown whether they continued anteriorly to bisect it as in Alligator. Laterally, the anterior nasals expand and form the posterior and posterolateral margins of the bony narial aperture. TMM 40571-1 appears to share this morphology. At midsnout, deformation of the right side has caused the medial margin of the maxilla to fold over the lateral margin of the nasals. Tentatively it is interpreted that the posterior extent of the nasals separates the anterior processes of the prefrontals from contacting the frontals; sutures are faint and cross-cut by many cracks.

Maxilla—Viewed through the bony narial aperture, the lateral walls of the nasal canal are formed by the maxilla (Fig. 12A). In dorsal view, the outline of the maxilla demonstrates pronounced mediolateral constriction at the first maxillary tooth, immediately behind the notch for receiving the third and fourth dentary teeth. Conversely, there are two associated areas of mediolateral expansion along the tooth row. The first corresponds to the area between the first and seventh alveoli, and the second corresponds to the area between the 10th and 14th alveoli. In the expanded regions, the diameter of the teeth increases from the anterior-most alveolus to the alveoli at the midpoint of the swelling and then decreases toward the posterior. There are 23 teeth in the maxillary tooth row; including the five premaxillary teeth, there are 28 teeth per side of the upper jaw. The largest maxillary tooth is in the fourth position; the fifth maxillary tooth is nearly as large. Lingual to the maxillary tooth row are depressions caused by the occlusion of the dentary tooth row; the taxon had an overbite.

The posterodorsal portion of the maxilla bears two posterior projections; the first separates the anterior-most jugal from the lacrimal, and the second separates the anterior-most lacrimal from the nasals. In palatal view, the maxilla terminates anterior to the lower temporal bar.

Suborbital Fenestra—The left suborbital fenestra is preserved (Fig. 12B); its posterior margin is missing. The anterior-most, anteromedial, and much of the lateral margin is formed by the maxilla. The anterior margin ends in an acute point roughly equal to the posterior margin of the 12th maxillary alveolus from the end of the tooth row. Although some breakage is present along the medial margin of the fenestra, the anterior margin appears to be smooth and unbroken.

The shape of the fenestra is reconstructed as teardrop-like. The medial and lateral margins are linear and traverse diagonally toward the anterior margin, which ends in an acute point. Although missing, preserved proportions suggest that the fenestra is widest at its posterior.

TMM 43632-1 (Fig. 14O, P) also preserves the anterior margin of the suborbital fenestra. Cracking is present, and the element has been split and folded at the tooth row. The reconstruction indicates that the anterior margin may not have been as acute as suggested by TMM 43620-1. Because the tooth row is incomplete in TMM 43632-1, the anterior extent of the fenestra cannot be determined. TMM 43538-1 demonstrates that posterior processes of the maxillae extend along the lateral margins of the palatines and form much of the medial margin of the fenestra.

Palatine—Palatines, save the posterior-most margins, are preserved (Fig. 12B). Additionally, TMM 43538-1 also preserves an anterior left palatine (Fig. S3). Extensive cracking obscures their morphology. At the midline, the anterior-most palatine forms a blunt projection. The palatines are interpreted to form the anterior and medial margins of the suborbital fenestrae; the medial margin of the left suborbital fenestra, formed by the lateral portion of the palatine, is incomplete. The lateral edges of the elements appear to be parallel from anterior to posterior. It is unlikely that they produced a shelf extending into the suborbital fenestra; this character (Char. 112) was left as uncoded in the phylogenetic analysis.

Pterygoid and Ectopterygoid—TMM 43620-1 does not preserve pterygoids or ectopterygoids, but TMM 43632-1 (Fig. 14A–C, I, J), a very large individual from the same unit, does. Left and right ectopterygoids are preserved; the left is complete. The posterior flange of a right pterygoid is preserved. The elements are extremely robust. Sutural marks on the right pterygoid suggest that the ectopterygoid did not extend to the posterior tip of the lateral pterygoid flange. The pterygoid ramus of the ectopterygoid is bowed; the posterolateral margin of the suborbital fenestra formed by the ectopterygoid would have been concave. TMM 40571-1 demonstrates that the maxilla broadly separates the ectopterygoid from contacting the maxillary tooth row (Fig. S2).

Frontal—The anterior extent of the frontal terminates in a broad sutural contact with the nasals posterior to the anterior extent of the prefrontals (Fig. 12A). The lateral edges of the anterior process of the frontal are linear. The medial margin of the left prefrontal is broken, giving the left lateral portion of the frontal an asymmetrical appearance relative to the right. The lateral edge of the frontal, forming the medial margin of the orbit, is upturned and confluent with the upturned portion of the prefrontal. The frontoparietal suture is curved, the concave side facing anteriorly. Posteriorly, the lateral extent of the frontoparietal suture participates in the supratemporal fenestrae where it likely prevents the parietal from contacting the postorbital.

Prefrontal—In dorsal view, the anterior margins of the prefrontals are obscured, although the most likely position of the sutures is indicated (Fig. 12A). Anteriorly, the prefrontals end in a moderately blunt point. Dorsoventrally oriented swellings are present on the prefrontal and form the medial orbital margin. The swelling of the prefrontal forms the anterolateral extent of a continuous ridge that forms the medial margin of the orbit. On the ventral side of the skull, the dorsal-most prefrontal pillars are preserved; the medial processes of the pillars are anteroposteriorly expanded. Anterior to the pillars lie anteroposteriorly oriented elliptical recesses on the ventral side of the prefrontal.

Lacrimal—Lacrimals are incomplete. A composite morphology is known using information from both sides (Fig. 12A). The anterior-most portions of both lacrimals are obscured due to cracking but likely extended slightly to the anterior of the jugals; the anterior extent of the lacrimals is much greater than that of the frontal and prefrontals. The medial and lateral margins are linear for much of their length. The posteromedial margin makes a lateral excursion starting just posterior to the anterior extent of the frontal and continues to the orbital margin—along this length, the lacrimal makes broad contact with the lateral margin of the prefrontal. The posterior extent of the lacrimal forms the anterior margin of the orbit. A dorsoventrally oriented, ‘V'-shaped notch is present on the lacrimal along the anterior border of the orbit.

Jugal—The left jugal is preserved in its entirety; the right jugal is largely absent (Fig. 12A, B). Laterally, the maxillojugal suture trends anteromedially from the lateral margin of the posterior snout toward the midline where it ends in a point. When viewed laterally, the anterior ramus of the element is widest immediately rostral to the orbit. The jugal forms a dorsoventral inflation along the lateral margin of the orbit.

The ventral and ventrolateral portions of the postorbital bar are formed by the jugal. The bar is relatively robust and is inset from the external lamina of the jugal. When viewed from an anterior aspect, the bar is ‘L'-shaped and bows toward the midline at the midpoint of its body.

The lower temporal bar is formed entirely by the posterior ramus of the jugal. The posterior ramus of the jugal flattens dorsoventrally. The posterior-most left jugal is missing; a plaster reconstruction is in its place. Remaining margins suggest that the posterior-most portion of the ramus likely tapered to a point lateral to the lateral condyle of the quadrate. When viewed ventrally, the medial jugal foramen cannot be located due to poor preservation and the presence of matrix.

Orbit—The margins of the orbits are partially ‘telescoped,' or elevated above the dorsal surface of the rostrum. Elements contributing to this morphology are the prefrontals, lacrimals, and jugals. The medial margins of the orbits, formed by the frontal, are gently upturned and are confluent with the ‘telescoped’ anterior and lateral margins formed by the prefrontal, lacrimal, and jugal. At the anterior-most margin lies a ventrally displaced ‘V'-shaped depression of the lacrimal. The result is a cup-like morphology formed by the anterior and medial margins of the orbit due to contributions of the frontal, prefrontal, lacrimal, and jugal.

Skull Table—Skull table and otic region sutures are obscured on the right side but obvious on the left (Fig. 12A). The skull table slopes ventromedially toward the sagittal axis. The frontals, parietals, and supraoccipital form the floor of a midline furrow, the lateral margins of these elements raised relative to the midline. Elements forming the lateral margins of the skull table, the postorbitals and squamosals, are on a single plane dorsal to the midline furrow. The effect of this morphology is a skull table the midline of which is ventrally depressed relative to the lateral margins.

Postorbital—The postorbital is boomerang-shaped in dorsal view, its anterolateral corner approximating a 90° angle (Fig. 12A). The element forms the posterior margins of the orbits and the anterolateral margins of the large supratemporal fenestrae. Along the dorsal angle of the infratemporal fenestra, the postorbital contacts the quadrate and the quadratojugal. The element forms much of the postorbital bar; the postorbital process of the postorbital extends along the dorsolateral face of the bar. Although broken on the right side, the anterolateral side of the postorbital, immediately ventral to the skull table, bears a shallow, pit-like indentation for a foramen, allowing for the passage of the postorbital vein (Porter et al., 2016). The anteroventral portion of the postorbital, when viewed laterally, bears an anteroposteriorly oriented groove near the suture with the anterior process of the squamosal; posteroventral to the groove on the postorbital is a confluent groove on the squamosal for attachment of a muscular ear flap (Iordansky, 1973).

Parietal—In dorsal view, the parietal is hourglass-shaped between the supratemporal fenestrae, the constriction present at the point of the medial margin of the supratemporal fenestra (Fig. 12A). The parietal possesses ventral processes in the supratemporal fenestra. However, sutural margins are difficult to interpret and appear to differ bilaterally. The parietal sends posterior processes to each side of the supraoccipital, reaching the posterior margin of the skull table. When viewed from the posterior aspect, the parietal comprises the dorsomedial margin of the left posttemporal fenestra, which is preserved in its entirety.

Supraoccipital—The supraoccipital is incompletely preserved; the posterior portion of the element is missing (Fig. 12A). However, other specimens (TMM 43538-1, TMM 43632-1) from the same unit preserve the element in its entirety (Fig. 15). The element is broadly exposed on the dorsal skull table; its anteroposterior length is abbreviated. The result is a half-moon-shaped exposure that culminates in a blunt point at its anterior extent. When viewed posteriorly, the supraoccipital is shaped like a cut diamond gemstone; its dorsolateral extent on the posterior skull forms the ventromedial margin of the posttemporal fenestrae. Posteriorly, the body of the supraoccipital bears mediolaterally trending indentations separated by a dorsoventrally oriented medial ridge.

Squamosal—The squamosal forms the posterolateral corner of the skull table (Fig. 12A). The postorbital-squamosal suture is concave anteriorly when viewed from a dorsal perspective and is located at the midpoint of the lateral margin of the supratemporal fenestra. The parietal-squamosal suture trends anteromedially from the posterior margin of the skull table and intersects the supratemporal fenestra at the midpoint of its posterior margin. Along the posterior wall of the supratemporal fenestra, the parietal-squamosal suture makes a lateral excursion and intersects the anterior opening of the posttemporal fenestra within the supratemporal fenestra. Laterally, the squamosal forms the roof of the otic aperture and the dorsal-most margin of the infratemporal fenestra. Along the dorsolateral surface of the element, the dorsal and ventral rims of the squamosal groove flare anteriorly. The posterolateral ramus of the squamosal is short and at its posterior-most extent contacts the paroccipital process of the exoccipital (Fig. 12D). When viewed posteriorly, the squamosal forms the dorsolateral margin of the posttemporal fenestra.

Quadratojugal—The left quadratojugal is incompletely preserved; the posterior-most extent has been reconstructed with clay; the right quadratojugal is missing entirely (Fig. 12A, B). The dorsal exposure of the quadratojugal is approximately twice the mediolateral width of the ventral exposure. The quadratojugal forms the posterior margin of the infratemporal fenestra. The suture joining the jugal and quadratojugal lies at the posterior angle of the infratemporal fenestra. TMM 43538-1 demonstrates that a quadratojugal spine projects into the infratemporal fenestra along the posterior wall between the posterior and superior angles. A dorsal process of the quadratojugal reaches the dorsal corner of the infratemporal fenestra and contacts the squamosal.

Quadrate—The left quadrate is mostly complete (Fig. 12A, B). The dorsal-most portions of the quadrate underlying the skull table are preserved, but the ventral portions in this area have been lost. Like the left quadratojugal, the posterior-most extent has been reconstructed. The quadrate forms the floor of the otic aperture and the ventral portion of the anterior wall along the external auditory meatus. Ventrally, the quadrate bears modest anteroposteriorly oriented crests for the attachment of the posterior adductor mandibulae muscle. Although incompletely preserved, the anterodorsal-most extent of the left quadrate underlying the supratemporal fenestra approaches the capitate process of the laterosphenoid; the elements may have contacted in life. Along the lateral braincase wall, the quadrate forms the posterior roof of the trigeminal foramen. TMM 43632-1 preserves an incomplete ventromedial portion of the quadrate. The quadrate forms the floor of the cranioquadrate passage and recess; the roof is formed by the paroccipital process of the exoccipital. TMM 43632-1 preserves both hemicondyles; the medial hemicondyle is smaller than its lateral counterpart (Fig. 14).

Laterosphenoid—The laterosphenoids are incompletely preserved in TMM 43620-1; the ventral-most portions are missing (Fig. 12B). The laterosphenoid forms the anterior margin of the trigeminal foramen. TMM 43632-1 also preserves dorsal portions; less bone is missing relative to TMM 43620-1, but sutures separating braincase elements are obscured. A pronounced anteroposteriorly trending ophthalmic groove is present on the laterosphenoid anterior to the roof of the trigeminal foramen.

Exoccipital—The exoccipital forms the ventrolateral margin of the posttemporal fenestra. Posteriorly, the paroccipital process of the exoccipital is laterally expansive and dorsoventrally deep. The lateral-most extension of the paroccipital process lies posteroventral to the posterior squamosal prong and forms an extensive sutural contact with the quadrate. Ventrally, the roof of the cranioquadrate recess is preserved on the posterolateral exoccipital. The ventral-most portion along the midline preserves the roof of the foramen magnum. When viewed from a ventral aspect, this region is posteriorly expanded. TMM 43632-1 preserves an unaltered foramen magnum (Fig. 15A). The dorsal and lateral walls are formed by the exoccipital. The floor is formed by the basioccipital. The foramen is heart-shaped in outline when viewed posteriorly.

TMM 43632-1 preserves the ventral exoccipital (Fig. 15). The robust ventral process of the element terminates dorsal to the basioccipital tubera and preserves openings for cranial nerves and blood vessels. Four depressions, likely representing infilled foramina for the passage of cranial nerves, are present on each ventral process of the exoccipital. The dorsal-most depression, presumably for the passage of cranial nerve XII, is lateral to the foramen magnum and is separated from the other depressions by a short distance. The other depressions are separated by mediolaterally trending ridges. The dorsal-most and deepest of the contiguous depressions, ventral to the depression for the conveyance of cranial nerve XII, is roughly triangular in shape. This depression is lateral to the ventral margin of the foramen magnum, has what appear to be small foramina inside its margins, and conveyed branches of cranial nerves IX, X, and XI as well as the jugular vein. Below it is the smallest depression, whose sides are nearly parallel and bordered by pronounced mediolaterally trending ridges. This depression likely corresponds to the carotid foramen. The ventral-most opening is nearly the same size as the dorsal-most opening but is very shallow. No obvious foramina are present within its borders; its function is unknown.

Basioccipital—TMM 43620-1 does not preserve a basioccipital, although it is preserved in TMM 43538-1 and TMM 43632-1. Preservation is best in TMM 43632-1 (Fig. 15). The element forms the floor of the foramen magnum and the occipital condyle. TMM 43632-1 best preserves the occipital condyle. The articular surface of the structure is bulbous and resembles a half sphere. A pronounced indention, separating the articular surface from the anterior portion of the structure, is present on all surfaces save the dorsal margin. Ventrally, the occipital condyle bears a large depression separating the articular surface from the basioccipital tubera.

Ventral to the occipital condyle, the external surface of the basioccipital is posteriorly oriented. Along the midline, directly below the condyle, lies a relatively large, unpaired foramen. Ventral to the midline foramen, an acute ridge separates dorsoventrally trending depressions of the posterior basioccipital tubera. The edges of the ventral and ventrolateral basioccipital tubera have been chipped away; the external openings of the medial and lateral eustachian foramina are not preserved. A pronounced wing-like ridge lies lateral to the ventral-most occipital condyle. The ridge trends dorsoventrally and is expanded anteroposteriorly, resulting in a structure that projects outward from the posterolateral surface of the basioccipital tubera. TMM 43632-1 likely preserves the posteroventral basisphenoid, but sutures are obscured, and the morphology cannot be determined.

Mandible—A complete mandible is preserved for TMM 43620-1 (Fig. 16); it is separated at the mandibular symphysis, but the left side is largely intact and shows little to no evidence of deformation. The mandible is robustly built and nearly 1.5 m in length. The mandibular symphysis is short and does not extend posteriorly beyond the fourth dentary alveoli. The anterior-most alveoli lateral to the mandibular symphysis are oriented sub-parallel to one another. Posterior to the mandibular symphysis, the mid-dentary alveoli gradually curve medially. When viewed laterally, the dentary forms the anterior margin of the mandibular fenestra. Two posterior projections of the dentary are present. The dorsal-most of the two projects between the anterior processes of the surangular, whereas the ventral one projects into the anterior angular. The dorsal projection bears the anterior portion of a longitudinal depression that is confluent with a posterior depression on the surangular that forms the posterior portion of this depression. The longitudinal depression spans the distance from the juncture of the 17th and 18th alveoli to a point nearly in line with the dorsal projection of the anterior angular.

The third and fourth dentary alveoli are confluent; their shared margin is ovoid in dorsal view and raised relative to the body of the anterior dentary. Anterior teeth appear to project somewhat more buccally than teeth further posteriorly. The left hemimandible preserves a complete lower tooth row; there are spaces for 23 alveoli. The posterior-most alveoli are incompletely preserved on the right side. The right dentary preserves teeth in alveoli 2, 4, 12, 13, 15, and a posterior alveolus of unknown identity. Teeth are present in alveoli 1 and 4 on the left side; the first tooth is complete; the fourth tooth is missing its crown. The first tooth projects anterodorsally and would have occluded into a space between the first and second teeth of the premaxilla. Although missing in both dentaries, the margin of the third alveolus suggests that the third tooth was the largest in the mandible; the fourth dentary tooth was nearly as large as the third.

Teeth are large in two regions of the mandible. Anteriorly, the third and fourth alveoli are large; in the mid-dentary, the 11th and 12th alveoli are large. The 12th and 15th teeth have depressions on the medial sides near the base of the crown. These depressions were likely caused by replacement teeth growing under the teeth. Because the maxilla preserves evidence of an overbite in this region, the depressions were not caused by occlusion of the upper jaw dentition.

Splenial—The left splenial is nearly complete (Fig. 16). Anteriorly, it tapers along the body of the mandible where it reaches the mandibular symphysis but does not touch its counterpart. The splenial overlies the medial side of the anterior dentary until the space between dentary alveoli 11 and 12 where it then contributes to the dorsal exposure of the mandible and follows medially along the tooth row. The posterodorsal portion of the element extends past the tooth row and continues to the anterodorsal margin of the coronoid. The splenial bounds the anterior half of the foramen intermandibularis medius. Although the sutures with the angular and coronoid are indistinct, the splenial likely formed part of the anterior margin of foramen intermandibularis caudalis.

Coronoid—The coronoid is preserved; its anterior margin is somewhat damaged (Fig. 16). The superior margin of the element slopes anteriorly. The coronoid bounds the posterior half of the foramen intermandibularis medius and forms the dorsal margin of the foramen intermandibularis caudalis. The two short, blunt projections of the coronoid extend anterior to the foramen intermandibularis caudalis. They are positioned dorsal and ventral to the foramen.

Surangular—The anterior processes of the surangular extend along the medial margin of the 23rd alveolus but are incompletely preserved on both sides of the mandible (Fig. 16). Preservation is best for the left element, which preserves both processes save the anterior-most portion of the ventral process. Sutural marks on the dentary suggest that they were equal to subequal—this is confirmed by TMM 40571-1, which preserves the anterior processes. The notch between the two anterior projections bears a foramen. This structure is the posterior-most feature in a lengthwise groove that trends anteriorly along the dentary to the space between the 17th and 18th alveoli. The surangular forms the dorsal and posterior margins of the external mandibular fenestra. The lateral wall of the glenoid fossa is formed by the surangular. The lateral portion of the element, ventral to the glenoid, bears a mediolaterally oriented swelling as seen in AMNH 3073. Posteriorly, sutural marks on the articular indicate that the surangular extended to the dorsal tip of the retroarticular process.

Angular—When viewed medially, the angular forms the posterior, ventral, and dorsal margins of the foramen intermandibularis caudalis (Fig. 16). From a lateral aspect, the angulosurangular suture makes broad contact with the external mandibular fenestra along its ventral margin. Laterally, the element sends two processes anterior to the external mandibular fenestra. The dorsal process is short and is exposed along the lateral face of the element. The ventral process is long and continues along the ventral mandible to a point nearly equal to the anterior processes of the surangular. Posteriorly, the angular continues to the dorsal tip of the retroarticular process.

Articular—The glenoid fossa, save the lateral wall, is formed by the articular (Fig. 16). The retroarticular process is relatively short but broad. TMM 43620-1 preserves a depression on the articular posterior to the glenoid fossa that may represent remnants of the foramen aerum—it is inset medially from the lingual margin of the retroarticular process. Unfortunately, no specimens referable to this species preserve structures that may be confidently identified as the articular foramen aerum. Along the point of contact with the medial surangular and angular, there is cracking and matrix present; no other specimens adequately preserve this area, and characters representing this region's morphology were not coded.

Postcrania—Referred specimen TMM 43620-1 preserves portions of the axial skeleton and both limb girdles. Numerous osteoderms are present, some in association (Fig. S5) and all have inflated keels with lumpy, deeply pockmarked ornamentation. No osteoderm bears straight margins when viewed from the dorsal perspective. Many osteoderms are presumably from the midline of the dorsal shield—width greatly exceeds length, and keels are large, lumpy, and symmetrical when viewed from the posterior or anterior perspective. A few are from the dorsal shield but would have been separated from the midline by one or more osteoderms—width greatly exceeds length, and keels are pronounced, large, and lumpy from the posterior or anterior perspective but are not symmetrical; they demonstrate a lean toward their lateral margin. Comparison with Alligator indicates that TMM 43632-1 preserves an osteoderm from the dorsal shield presumably just to the posterior of the hind limbs (Fig. 17I, J). The element is likely from the lateral-most margin and is approximately as wide as it is long. The inflated keel is asymmetrical when viewed from the anterior or posterior—one side of the keel demonstrates a nearly linear slope from the margin to the apex, whereas the other demonstrates a strong concavity.

TMM 43620-1 preserves a second cervical rib; it is approximately 10 cm in length and is missing both rib heads (Fig. 18I). The body of the rib tapers from anterior to posterior and ends in a blunt tip. A large dorsal rib is preserved; portions of the mid-body have been reconstructed using clay. The rib head is missing. The body of the rib is nearly equal in diameter along its length—the site of articulation with the costal cartilage is slightly greater in diameter, and more robust, relative to the mid-body of the element.

TMM 43632-1 preserves a cervical rib and three large thoracic ribs (Fig. 17A–E). The cervical rib is a right anterior cervical rib located no further forward than the third cervical vertebra. Its body is short and tapers anteriorly and posteriorly to a blunt tip. Of the thoracic ribs, the first is from immediately posterior to the forelimb girdle (Fig. 17C). The rib is reconstructed using plaster or clay; only the anterior portion of the rib remains. The dorsal rib head is missing; the ventral is mostly preserved. The second rib is the best preserved of the three and is a thoracic rib from the anterior of the thoracic series (Fig. 17D). The body is robust and nearly equal in diameter throughout. The body gradually expands to accommodate the wider diameter of the posteroventral end of the rib for articulation with the costal cartilages. The ventral rib head is preserved; the dorsal is missing. The third rib is from the posterior of the thoracic series of ribs (Fig. 17E). The ventral rib head is preserved, but the dorsal head is missing.

TMM 43620-1 preserves four vertebrae from the dorsal series. These vertebrae are likely from the lumbar region because the long transverse processes do not bear articular surfaces for rib capitula. The vertebrae were discovered in association, and proportions suggest that they were contiguous in series. When present, dorsal-most neural spines demonstrate a mediolateral swelling for the attachment of epaxial musculature. The dorsal-most extent of this feature is flat. The mediolateral swelling differs among the sample, and some are larger than others.

TMM 43632-1 preserves 14 vertebrae, four cervical and 10 dorsal. Ventral keels are short for the anterior-most cervical vertebrae and increase in length to the posterior of the cervical series. Not all cervical vertebrae are preserved—the four (Fig. 19A–D) here likely represent the anterior-most elements in the cervical series. Two anterior thoracic vertebrae (Fig. 19E, F) are preserved. They bear pronounced ventral keels, have facet attachments for two rib heads, and have dorsally displaced transverse processes that attach high on the neural arch. Five of the dorsal vertebrae are from the thoracic series (Fig. 19G–K). They are too incomplete to determine their position but have vertebral bodies that do not bear articular facets for ribs as well as transverse processes that are located high on the neural arch. Two of the vertebrae likely belong to the lumbar series (Fig. 19L, M). They are robustly built, do not have attachments for ribs, and have their transverse processes located low on the neural arch. One vertebra has an uncertain placement among the vertebral series (Fig. 19N). It preserves the vertebral body and portions of both pedicles. The body does not preserve articular facets for the attachment of rib heads—in life, it was posterior to the cervical series.

TMM 43620-1 preserves forelimb and girdle elements consisting of a coracoid, radius, ulna, humerus, and indeterminate phalanges (Fig. 18). A complete left coracoid preserves the ventral portion of the glenoid fossa (Fig. 18B). A foramen is present immediately anterior to the posterolaterally flaring glenoid fossa, and the blade flares ventrally. The ventrally flaring blade preserves an anteroventral corner bearing a blunt projection that grades dorsally into the blade via a concave angle. A right humerus is preserved (Fig. 18A). The deltopectoral crest is missing; no characters could be coded for this structure. Sutural scars for M. teres major and M. dorsalis scapulae are not clear. Both the proximal and distal articular ends of the bone are incompletely preserved. The anterolateral side of the shaft preserves a strong concave curve, whereas the posteromedial side preserves a strong convex curve. The left radius and ulna are preserved (Fig. 18D). The distal epiphysis of the ulna is complete; the proximal epiphysis is missing. The radius does not preserve either epiphysis. TMM 43620-1 preserves three phalanges. One is missing the distal end (Fig. 18F), one is missing the proximal end, and the third is complete (Fig. 18G). A right proximal radiale is preserved (Fig. 18H).

TMM 43620-1 hind limb girdle elements consist of an ilium and pubis (Fig. 18). The anterodorsal portion of the right ilium is poorly preserved—morphology is enigmatic (Fig. 18E). The left pubis is preserved; its blade flares anteriorly (Fig. 18C). The anteromedial corner ends in a blunt point whose dorsomedial margin gently grades via a concave curve into the dorsal blade. The shaft is broadly curved to the anterior, but cracking is present at the juncture of the blade and shaft; extent of the curvature may be taphonomic. TMM 43632-1 preserves a femur, a calcaneum, and a metatarsal (Fig. 17). A left femur is preserved; a portion of the midshaft is not preserved (Fig. 17K). The proximal epiphysis is bulbous and nearly featureless. The lateral condyle of the distal epiphysis is much larger and anteroposteriorly more expansive than the medial counterpart. The fourth trochanter is preserved; it is visible on the posteromedial side of the shaft ventral to the proximal epiphysis. A distal end of a calcaneum is preserved (Fig. 17G, H). TMM 43632-1 preserves a distal metatarsal (Fig. 17F).

Holotype—MMNS VP-256 (Figs. 20–22).

Referable Specimens—TMM 45973-1 consists of an upper jaw and mandible from the lower Campanian Mooreville Formation of Lowndes County, Alabama, U.S.A. (Figs. 23, 24). ALMNH 1002 consists of a postcranial skeleton from the lower Campanian Mooreville Formation of West Greene, Greene County, Alabama, U.S.A. (Fig. 25).

Diagnosis—Deep occlusal marks present on the premaxilla between the first and second alveoli and lingual to the third and fourth alveoli; premaxillary-maxillary notch is lateral to the fifth premaxillary tooth; angular, posterior to external mandibular fenestra, is dorsoventrally expanded so as to form a hump on the dorsal margin; anterior margin of suborbital fenestra blunt and extends no further than the 10th maxillary alveolus from the end of the tooth row; ophthalmic groove trends dorsoventrally.

Occurrence—Middle Campanian, Late Cretaceous, Coffee Sand Formation, along Tulip Creek near Tupelo, Lee County, Mississippi, U.S.A.

Etymology—The specific epithet is named in honor of David R. Schwimmer for his tireless work on the Late Cretaceous paleontology of the Southeast and Eastern Seaboard, U.S.A.

Description

Deinosuchus schwimmeri MMNS VP-256 represents a beautifully preserved posterior skull and partial mandible (Figs. 20–22) from the Coffee Sand Formation of Lee County, Mississippi. The right side of the skull preserves a greater number of complete elements and clearer sutural contacts than the left side.

Nasals—The posterior half of the nasals are preserved (Fig. 20A). Anterior to the prefrontals, their lateral margins are nearly linear. The posterior processes of the nasals bound the anterior projection of the prefrontal; it does not contact the lacrimals. The posterior-most nasals contact the anterior margin of the frontal.

Maxilla—The anterior maxilla, along with the rest of the anterior rostrum, is not preserved (Fig. 20A). Posteriorly, a short acute process of the maxilla extends between the lacrimal and the nasal, and a blunt posterior process extends between the anterior lacrimal and the jugal. A posterolateral process of the maxilla separates the anterolateral jugal from contacting the lateral margin of the snout.

Ventrally, the maxilla preserves spaces for 13 posterior alveoli. Preserved teeth are missing their crowns. Assigning positions from the posterior of the tooth row, teeth are preserved in alveoli 3–6 and 8–13. Tooth diameter increases from posterior to anterior. Preserved portions indicate that enamel and dentin are thick; posterior teeth have very small pulp cavities.

The maxillary foramen for the palatine ramus of cranial nerve V is relatively small and is situated medial to the junction of the 12th and 13th alveoli from the posterior. The maxilla separates the ectopterygoid from the posterior tooth row. The maxilla forms the anterior, anteromedial, and anterolateral margins of the anteroposteriorly expansive suborbital fenestrae. The right suborbital fenestra is better preserved than the left; its posterior margins are missing. Anteriorly, the fenestra ends in a blunt point approximately in line with the junction of the 10th and 11th alveoli from the posterior. The posterior process of the maxilla extends into the lateral palatine along the medial margin of the suborbital fenestra where it extends with the level of the eighth alveolus from the posterior.

Palatine—Ventrally, the anterior portion of the right palatine is preserved (Fig. 20B). The anterior maxillopalatine suture is nearly linear and is mediolaterally oriented; the sutural contact is complex. The lateral portion of the anterior suture is nearly linear and ends as a small, blunt anterior projection. Preserved portions indicate that the palatines contributed to the medial margins of the suborbital fenestrae.

Ectopterygoid—Dorsal portions of the ectopterygoids are preserved; ventral portions along the pterygoid wings have been lost (Fig. 20B). Ventrally, at the juncture of the postorbital bar and the jugal, the ectopterygoid sends a blunt, broadly curved process medially along the ventral base of the bar. The posterodorsal portion of the element in contact with the jugal is separated from the ventrolateral margin of the skull by a short distance. Anteriorly, the maxillary face of the element extends parallel to the posterior maxillary tooth row and ends in an acute point at the anterior margin of the sixth maxillary tooth from the posterior. The ectopterygoid is separated from contacting the posterior tooth row by the maxilla.

Jugal—The jugals are long and broad (Fig. 20A). The maxillojugal suture trends anteromedially from the lateral margin of the posterior snout toward the midline. The anterior extent of the jugal ends in a blunt point where it approaches within 3–4 cm of the anterior margin of the lacrimal. The jugolacrimal suture is nearly linear. The anterior ramus of the jugal is widest and deepest immediately anterior to the orbit. The jugal forms an upturned lateral margin of the orbit.

The ventral portion of the postorbital bar is formed by the jugal; the bar is inset from the lateral jugal surface. The bar is large in diameter and when viewed from an anterior aspect; the bar is ‘L'-shaped and at the midpoint of its body bows toward the midline of the skull. When viewed ventrally, the medial jugal foramen cannot be located due to poor preservation, but a small unrelated foramen is present posterior to the confluence of the posttemporal bar and the lower temporal bar. The lower temporal bar is formed by the posterior ramus of the jugal. Posteriorly, the jugal tapers to a point where it meets the quadratojugal at a suture that trends posterolaterally from the posterolateral corner of the infratemporal fenestra to the lateral margin of the skull.

Lacrimal—Both lacrimals are preserved; the right element demonstrates clear sutural contacts (Fig. 20A). The anterior lacrimal ends in a blunt point. Sutural contacts with the jugals, nasals, and prefrontals are broad, nearly linear, and trend anteroposteriorly. The lacrimal extends slightly farther to the anterior and much farther to the anterior than the jugal and the prefrontal, respectively. The posterior lacrimal is somewhat mediolaterally constricted compared with the anterior. A dorsoventrally oriented, ‘V'-shaped notch is present along the anterior margin of the orbit, which is formed by the lacrimal.

Prefrontal—Both prefrontals are preserved; the anterior margins end in an acute point bounded anteriorly by the nasals (Fig. 20A). The prefrontals exceed the frontal in their anterior extent. Along much of its length, the prefrontofrontal suture is anteroposteriorly oriented and nearly linear; at the posterior-most extent, the suture forms a nearly right angle and trends mediolaterally to the medial margin of the orbit. The prefrontal forms the upturned anteromedial margin of the orbit. Ventrally, the dorsal prefrontal pillars are preserved; the medial processes are expanded anteroposteriorly. Anterolateral to the pillars lie anteroposteriorly oriented elliptical recesses of the prefrontal.

Frontal—Anteriorly, the frontal ends in a blunt point where it contacts the nasals (Fig. 20A). The lateral edges of the anterior process of the frontal are linear. Posteriorly, the frontal forms the upturned medial margin of the orbit, confluent with the upturned anteromedial margin formed by the prefrontal. The frontal contacts the postorbital anteriorly at the posteromedial corner of the orbit. The frontoparietal suture is concave anteriorly. Posterolaterally, processes of the frontal form part of the anterior margin of the supratemporal fenestrae. When viewed internally, the projection that forms the anterior margin also forms the anterior wall of the fenestra and prevents the parietal from contacting the postorbital.

Orbit—The orbits are ‘telescoped' or elevated above the dorsal surface of the rostrum, along the anterior and lateral margins and gently upturned along the medial margin (Figs. 20A, 21C). The prefrontals, lacrimals, and jugals contribute to this morphology. The gently upturned medial margins formed by the frontal are confluent with the ‘telescoped’ anterior and lateral margins formed by the prefrontal, lacrimal, and jugal. At the anterior-most margin lies a ventrally displaced ‘V'shaped depression (Fig. 21C). The result is that the anterior and medial margins of the orbit are cup-like and are formed in part by contributions of the frontal, prefrontal, lacrimal, and jugal.

Skull Table—The skull table slopes ventromedially toward the sagittal axis, forming a midline furrow contributed to in part by the frontals, parietals, and supraoccipital (Figs. 20A, 21C). The lateral margins of these elements are raised relative to their midline. Elements forming the lateral margins of the skull table, the postorbital, and the squamosal, are on a single plane dorsal to the midline furrow. The result is a skull table the midline of which is ventrally depressed relative to the lateral margins (Fig. 21C).

Postorbital—The postorbital forms the posterior margins of the orbits and the anterolateral margins of the large supratemporal fenestrae (Fig. 20A). The postorbitosquamosal suture trends diagonally from the lateral margin of the skull table to the point where it intersects the supratemporal fenestra along the midpoint of its lateral margin. The postorbital contacts the quadrate and the quadratojugal along the dorsal angle of the infratemporal fenestra. The postorbital process is moderately inset from the anterolateral margin of the skull table and extends along the dorsolateral face of the postorbital bar, forming much of the structure. When viewed laterally, the anterodorsal portion of the postorbital bears an anteroposteriorly oriented groove near the suture with the anterior projection of the squamosal. This groove is confluent with a groove on the squamosal and in life formed the attachment site for the muscular ear flap.

Parietal—The parietal is hourglass-shaped in dorsal view (Fig. 20A). Dorsally, the element forms the medial margins of the supratemporal fenestrae and, within the fenestrae, the medial walls. The anterior margin of the parietal enters the supratemporal fenestrae via lateral processes; these processes form the anteromedial walls of the fenestrae. The parietal extends laterally, relative to the supraoccipital, to the posterior margin of the skull table. Sutural contact with the squamosal is nearly linear and trends posterolaterally from the posterior margin of the supratemporal fenestrae to the posterior skull table. Along the posterior wall of the supratemporal fenestrae, the parietosquamosal suture makes a lateral excursion where it intersects the medial margin of the anterior opening of the temporal canal. When viewed from a posterior aspect, the parietal-squamosal suture intersects the posttemporal fenestrae midway along the dorsal margin. The parietal comprises the dorsomedial margins of the posttemporal fenestrae.

Squamosal—The squamosal forms the posterolateral corner of the skull table (Fig. 20A). The posterolateral margins of the supratemporal fenestrae are formed by the element. Within the fenestra, the squamosal forms the posterolateral wall. All margins, save the medial, of the anterior opening of the temporal canal are formed by the squamosal. Laterally, the squamosal forms the roof of the otic aperture, the posterior margin of the external auditory meatus, and the dorsal-most margin of the infratemporal fenestra. The huge squamosal groove, for attachment of the external ear valve musculature, is dorsoventrally expansive (Fig. 20D). The dorsal and ventral rims of the groove flare anteriorly then slightly contract at their anterior-most extent. The posterolateral ramus of the squamosal is relatively short. The ventral portion of the ramus contacts the lateral extent of the paroccipital process of the exoccipital. When viewed from a posterior aspect, the squamosal forms much of the dorsal margin of the posttemporal fenestra.

Supraoccipital—The supraoccipital is crescent-shaped; the mediolateral breadth of the element exposed on the dorsal skull table greatly exceeds the length (Fig. 20A). A blunt point is present at its anterior extent. When viewed posteriorly, the supraoccipital is shaped like a cut gemstone the dorsal margin of which is ventrally indented. Posteriorly, the medial margins of the posttemporal fenestrae are formed by the dorsolateral margins of the element. The posterior body of the supraoccipital bears mediolaterally trending indentations separated by a medial ridge that extends from the dorsal skull table to the ventral margin of the element.

Exoccipital—The exoccipitals are complete (Fig. 20D) and form the ventral margins and floor of the posttemporal fenestra; the floor of the fenestra is visible when the skull is viewed dorsally (Fig. 20A). Anteriorly, very little of the exoccipital is preserved on the lateral braincase; ventral portions are missing. The paroccipital process is wide and makes extensive contact with the quadrate. The element extends further laterally than the posterior squamosal prong that contacts the paroccipital process of the exoccipital posteriorly. Ventrally, and somewhat medial to the lateral-most extent of the paroccipital process, the exoccipital forms the roof of the cranioquadrate recess; the floor of the recess is formed by the quadrate. The dorsal and lateral margins of the foramen magnum are formed by the exoccipitals. Lateral to the occipital condyle, the element preserves openings for cranial nerves and blood vessels. These features are clearest on the left side. Three openings are preserved; they are separated by slight ridges. The dorsal and ventral foramina are roughly the same size and are deeper than the opening in the middle position. The dorsal foramen, presumably for the passage of cranial nerve XII, is lateral to the dorsal-most extent of the occipital condyle and bears foramina within its margins. The middle depression is presumably for the passage of cranial nerves IX-XI and the jugular vein while the ventral depression is presumably for the passage of the carotid artery. Neither depression bears obvious foramina within their margins.

Basioccipital—The dorsal basioccipital remains, but ventral portions have been lost (Fig. 20E). The floor of the foramen magnum is formed by the element. The occipital condyle is formed by the basioccipital; some breakage is present on the right ventral margin of the condyle. When viewed laterally, the dorsal margin of the occipital condyle slopes slightly ventrally from anterior to posterior.

Laterosphenoid—Much of the anterior and ventral laterosphenoids are missing (Fig. 20B, C). Sutures separating braincase elements are difficult to discern. The anterior margin of the trigeminal foramen is formed by the element. Laterally, the capitate process is oriented anteroposteriorly toward the midline. The laterosphenoid makes a robust contact with the quadrate ventral to the postorbital. The element preserves the ophthalmic groove, which trends dorsally as it moves from the trigeminal foramen to the anterior.

Quadratojugal—Both quadratojugals are preserved; the right side is complete (Fig. 20A, B). The posterior margin of the infratemporal fenestra is formed by the element. The jugoquadratojugal suture is linear and intersects the posterior angle of the infratemporal fenestra anteriorly. The element preserves a quadratojugal spine that projects into the infratemporal fenestra along the posterior wall between the posterior and superior angles. A dorsal process of the element reaches the dorsal corner of the infratemporal fenestra where it contacts the squamosal.

Quadrate—Both quadrates are preserved; the right side is complete (Fig. 20A, B). Dorsally, the element forms the floor of the otic aperture. The anterior and ventral walls of the external auditory meatus are formed by the quadrate. The squamosal-quadrate suture extends to the posterodorsal corner of the external auditory meatus. Posteroventrally, modest crests for the attachment of the posterior m. adductor mandibulae are present; they are oriented anteroposteriorly along the posterior ramus. The anterodorsal-most extent of the quadrate, ventral to the supratemporal fenestra, contacts the capitate process of the laterosphenoid. The ventral process of the quadrate is significant and forms much of the lateral braincase wall. The posterior half of the trigeminal foramen is formed by the quadrate. The floor of the cranioquadrate recess is formed by the quadrate. The medial hemicondyle is incompletely preserved; it is unknown which hemicondyle was larger in the species. The quadrate foramen aerum could not be located.

Mandible—A partial mandible is preserved (Fig. 22). Portions of the left dentary, splenial, surangular, angular, and articular are preserved, along with a more complete right articular and right coronoid. The splenial is very fragmentary; no characters were coded for the element. The posterior-most dentary maintains the anterior, anterodorsal, and anteroventral margins of the external mandibular fenestra. All margins of the fenestra are chipped, but proportions and contribution of elements are clear. Posteroventrally, the dentary stops anterior to the external mandibular fenestra, but possible sutural marks on the angular may attest to the dentary extending along the ventral margin of the external mandibular fenestra.

Surangular—The surangular is poorly preserved anteriorly, medially, and posterodorsally, making description difficult (Fig. 22C–E). The posterior and posterodorsal margins of the external mandibular fenestra are formed by the surangular. The suranguloangular suture contacts the external mandibular fenestra along its ventral margin. Sutural marks on the right articular suggests that the surangular formed the lateral margin of the glenoid fossa. Characters near the juncture of the surangular, angular, and articular were not coded due to poor preservation. Sutural marks on the retroarticular process suggest that the surangular reached the dorsal tip of the articular.

Angular—The angular is incompletely preserved; the anterior and posterior-most margins are missing (Fig. 22C–E). The element forms the posteroventral margin of the external mandibular fenestra. Posterior to the fenestra, the element expands dorsoventrally such that the dorsal margin has a pronounced hump when in lateral view. Sutural marks on the articular suggest that the posterior margin of the angular extended to the dorsal tip of the retroarticular process. Although incompletely preserved, the angular forms the posterior and ventral margins of the foramen intermandibularis caudalis. An anterior process of the angular possibly formed part of the dorsal margin as well. Posterior to the foramen, the angular becomes dorsoventrally more expansive, resulting in a hump-like morphology of the dorsal margin on the medial side of the element.

Coronoid—A right coronoid is preserved; the anterior margin is damaged in places (Fig. 22B). The element appears to form the posterior margin of the foramen intermandibularis medius. Because it is disassociated from the mandible, the extent of its contribution to the margins of the foramen intermandibularis caudalis is unknown. Although disassociated, the superior margin of the element appears to slope anteriorly; this character was left uncoded in the matrix.

Articular—The left hemimandible portion preserves a fragment of the ventral articular (Fig. 22C, D). A right articular is present but is disassociated from other mandibular elements. The left fragment does not preserve any codable morphology. The right fragment preserves the glenoid fossa and the retroarticular process (Fig. 22A). A depression likely representing the foramen aerum of the articular is inset from the lingual margin of the posterodorsally projecting retroarticular process.

Teeth—Five partial loose teeth are associated with MMNS VP-256 (Fig. 22F). Enamel is thick and in the best-preserved teeth demonstrate apicobasal striations. Three are small posterior teeth, one of which preserves a complete crown that is roughly conical; the crown is short. Two are larger anterior dentary or maxillary teeth; one preserves a tall conical crown. The largest and most complete of the crowns demonstrates a slight carina on the mesial and distal sides.

TMM 45973-1

This specimen consists of a complete snout and mandible (Figs. 23, 24) from the lower Campanian Mooreville Formation of Lowndes County, Alabama, U.S.A. It is approximately the same size as the D. schwimmeri holotype. The specimen was found on the west bank of the Alabama River approximately 200 m upstream from the Army Corps of Engineers Lock and Dam.

Surficial bone is deteriorating from moisture-induced destruction via geochemical processes or ‘pyrite disease'; a gray powdery substance has replaced fossilized bone in affected areas. The bone has two textures: one is powdery, light tan in color, and feels slightly rough to the touch; the other texture is dark tan in color and smooth to the touch. Powdery tan areas obscure sutures, likely as a result of ‘pyrite disease.’ The posterior of the snout near the right orbit and along the posterolateral margin of the left side has been reconstructed with a dark tan clay.

The skull has experienced dorsoventral crushing. Reconstruction efforts were made to separate the palatal portions from the roof of the snout, but palatal elements are largely in a single plane. Some of the three-dimensional morphology is obscured, but spatial relationships are maintained. The anterior portion of the snout bearing the premaxillae is in a poor state of preservation. The anteroventral portion bearing the premaxillary alveoli suggests that the anterior snout was moderately deep; it is not likely that the depth equaled that of D. riograndensis.

Premaxilla—The premaxilla is preserved, but the anterior portion is disassociated from the rest of the skull; dorsal margins are largely destroyed (Fig. 23A, B). The premaxilla has five alveoli per side. The left side preserves five alveoli with five broken teeth. The right side of the element preserves the first and second alveolar positions and the anterior margin of position the fourth; the first position bears a broken tooth. Where the third alveolus is predicted to be, there is either bone overgrowth or the products of ‘pyrite disease.’ Proportions of the teeth can be determined from the left side. Teeth in positions 1 and 2 are small; teeth in positions 3 and 4 are large; the fifth tooth is small. Among the premaxillary teeth, the third tooth is the largest and the fifth is the smallest.

Posterior to the space between the first and second teeth, there is a groove produced by the occlusion of the first dentary tooth with the premaxilla. A second groove is present between the third and fourth premaxillary teeth. This groove was likely produced by occlusion with the second dentary tooth. Posterior to the fourth alveolus and posteromedial to the fifth is a large groove for receiving the third and fourth dentary teeth. When viewed from the anterior, the mesial-most and distal-most premaxillary tooth row is dorsally displaced relative to the third and fourth premaxillary teeth. The effect is a ventral bulge of the premaxilla at the point of the third and fourth alveoli. Posteroventral margins of the element are preserved. Sutures with the maxilla are mediolaterally oriented and trend anteriorly toward the midline. Anteroventrally, the element may bear remnants of the incisive foramen.

Nasal—The sutural contacts between the nasals and other elements are clearest in the anterior snout (Fig. 23A). The anterior nasals are laterally expanded and form the posterior margin of the bony narial aperture. Along the midline, the nasals project into the aperture at the midline. There is evidence of broken bone; in life, the projection may have extended further forward, but proportions suggest that it would not have extended far enough to bisect the large bony narial aperture. Preserved margins suggest that the aperture was very wide.

Posterior to the bony narial aperture, sutures with the maxilla are mediolaterally oriented and trend anteriorly toward the midline where the nasals proceed posteriorly and whose margins are nearly parallel. At midsnout, anterior to the frontals and prefrontals, the sutures are obscured due to the effects of ‘pyrite disease.'

Maxilla—The maxillae are preserved; the right side is nearly complete save its ventral surface (Fig. 23A, B). Due to ‘pyrite disease’ and the powdery texture of surficial bone, sutures on the dorsal side of the snout are very difficult to determine. The element's contribution to the bony narial aperture is unknown. However, the maxillary tooth row appears to be complete on the right side, suggesting that the anterior maxilla is known and was excluded from the posterior and posterolateral apertures.

There are 28 teeth in the upper jaw: 23 maxillary, five premaxillary (Fig. 23B). The right side has the best preservation of the tooth row, and comparison with MMNS VP-256 suggests that the posterior-most alveoli are preserved. The animal had an overbite, as suggested by occlusal marks lingual to the maxillary tooth row.

Two mediolateral expansions are present along the maxillary tooth row. The anterior expansion occurs in the area between the first and seventh alveoli, and the posterior expansion corresponds to the area between the 10th and 14th alveoli. The former expansion is pronounced, and the latter is minimal. The diameter of the teeth increases from the anterior-most alveolus to the alveoli at the midpoint of the anterior expansion and then gets progressively smaller toward the posterior—the fourth maxillary alveolus is the largest; the fifth appears to have been nearly as large.

Posterodorsally, the posterior process of the maxilla extends between the anterior processes of the lacrimal and jugal. Additional processes separating posterior snout elements are impossible to determine due to ‘pyrite disease.’

The suborbital fenestrae are large. Their posterior margins are missing; the anterior margin is best preserved on the right side. The anterior margin ends in a blunt point at the ninth alveolus from the end of the maxillary tooth row. The maxilla forms the anterior margin and much of the medial and lateral margins. The posterior process of the maxilla separates the palatines from the anteromedial margin of the fenestra.

Palatine—The sutures uniting the left and right palatines are present between the suborbital fenestrae (Fig. 23B). The skull is dorsoventrally compressed in this area, and the posterior-most margins of the element are missing. Much of the anterior palatines are obscured or missing. The palatines make up part of the medial margins of the suborbital fenestrae.

Lacrimal and Jugal—The dorsal side of the posterior snout is poorly preserved; bone is missing, and remaining bone is affected by ‘pyrite disease’ (Fig. 23A). Some regions are reconstructed from clay. The sutural contacts between the lacrimals and the maxillae are clearest on the right side. The lacrimals are long and wide. Their anterior extent ends in an acute point beyond the anterior-most extent of the jugal. The sutural contact with the broad jugal is nearly linear. The jugal is best preserved on the right side and ends in a blunt point.

Ectopterygoid—The ectopterygoids are preserved; the right element is more complete (Fig. 23B). The maxillary face of the ectopterygoid extends along the maxilla to an acute point medial to the anterior margin of the fifth alveolus from the posterior. The maxillary face is broadly separated from the posterior tooth row by the maxilla. Posterior to the maxillary face, a fraction of the jugal face of the ectopterygoid is preserved. Ventral-most portions of the element are missing.

Mandible—A complete right mandible is preserved (Fig. 24); the mandible has been twisted during burial, and elements have been offset. Along the lingual margin of the mandible, ‘pyrite disease’ has replaced fossilized bone with iron sulfide minerals. The number of teeth in the mandible is unknown; the posterior tooth row is very fragmentary.

Dentary—The dentary is nearly complete (Fig. 24). Anteriorly, the mandibular symphysis is missing along its medial margin; the lingual margins of some anterior teeth are preserved. It is impossible to determine whether the third and fourth dentary alveoli were confluent. Dorsoventral crushing is present at the point of the external mandibular fenestra; it is likely that the dentary contributed to the anterior and dorsal margins of the fenestra.

Splenial—A disassociated, partial splenial is present. The medial side of the element preserves the Meckelian groove. No characters were coded for the element.

Surangular—The surangular is preserved (Fig. 24A, B, D). The anterior processes of the surangular are subequal. A process of the surangular extends anteriorly along the medial margin of the final alveolus; the anterior-most tip of the process is missing. The suranguloangular suture appears to pass broadly along the ventral margin of the dorsoventrally crushed external mandibular fenestra. It appears that the surangular forms the posterodorsal margin of the external mandibular fenestra. The lateral margin of the glenoid fossa is composed of the surangular; the articular forms the remaining margins of the fossa. Characters near the juncture of the surangular, angular, and articular were not coded due to poor preservation. Sutural marks on the retroarticular process of the articular suggest that the surangular and angular reached the tip of the retroarticular process.

Angular—The angular is preserved, but some crushing is present anteriorly (Fig. 24A, B, D). The element likely forms the posteroventral margin of the external mandibular fenestra. Posterior to the fenestra, the element expands dorsoventrally; the dorsal margin has a pronounced hump in lateral view. The posterior margin of the angular extended to the dorsal tip of the retroarticular process, as evidenced from sutures on the articular. The entire ventral margin and part of the posterior margin of the foramen intermandibularis caudalis are preserved; they are formed by the angular. Posterior to the foramen, the medial side of the angular becomes dorsoventrally expansive.

Articular—A nearly complete articular is preserved (Fig. 24A, B, D). The element preserves the glenoid fossa and the retroarticular process. The foramen aerum of the articular cannot be located. Poor preservation and ‘pyrite disease’ make morphology of the medial mandible, where the articular, surangular, and angular meet, impossible to interpret; morphology in this region was not included in the phylogenetic analysis.

ALMNH 1002

This specimen is tentatively assigned to D. schwimmeri and represents the most complete postcranial skeleton attributable to the species (Fig. 25). The specimen represents a small, immature individual from the lower Campanian Mooreville Formation near West Greene, Greene County, Alabama, U.S.A. Hind limbs, vertebrae, chevrons, and numerous osteoderms are preserved.

Limbs and Limb Girdles—Hind limbs and limb girdles are mostly complete. Left and right ilia are present (Fig. 25B). The iliac anterior process is virtually absent, and the dorsal margin of the iliac blade is rounded with modest dorsal indentation. The supraacetabular crest is narrow. Fragmentary pubes are present; blades flare anteriorly (Fig. 25B). Shafts are short and curve to the anterior. Ischia are complete (Fig. 25B). The limbs are represented by both femora (Fig. 25C), a complete left tibia and fibula (Fig. 25D, E), and a distal right tibia and fibula. A left astragalus and calcaneum (Fig. 25G) and two tarsals of unknown identity are present (Fig. 25G). Metatarsals I–III and V are present on the right side; the left side preserves metatarsals I–IV (Fig. 25F). Seven phalanges are preserved and likely represent hind limb elements (Fig. 25I).

Vertebrae—Twenty-nine vertebrae are preserved from the dorsal through caudal series (Fig. 25A). Some neural arches are fully coossified with the vertebral centra, indicating that this specimen represents a nearly mature individual. Ten dorsal vertebrae, both sacral vertebrae, and 17 caudal vertebrae are preserved. Dorsal vertebrae possess mediolaterally broad terminal neural spines and transverse processes that are nearly on the same plane as the postzygapophyses. The anterior sacral rib capitulum projects anteriorly of the tuberculum and is visible in dorsal view.

Osteoderms—Numerous osteoderms are preserved, representing most parts of the dorsal and nuchal shields (Fig. 25J). Dorsal surfaces are deeply pitted. Smaller osteoderms, presumably from the nuchal shield, are oval in shape and bear inflated keels. Larger osteoderms, likely from the dorsal shield, are rectangular in shape. Some are nearly flat in anterior or posterior view with small keels. Others bear inflated keels.

Referral of Material to Deinosuchus schwimmeri

TMM 45973-1 was found in a similar geological context to the holotype specimen from the Coffee Sand Formation of Lee County, Mississippi, U.S.A. The Mooreville Formation is a facies equivalent of the Coffee Sand Formation (Cushing et al., 1964). In addition to their similarity in proportions, size, and geological context, TMM 45973-1 may be referred to D. schwimmeri based on a similar angular morphology. Like the holotype, the angular of TMM 45973-1, posterior to the external mandibular fenestra, is dorsoventrally expanded so as to form a hump on the dorsal margin. Additionally, the anterior margin of the suborbital fenestra is blunt in both the holotype specimen and TMM 45973-1; it extends no further than the 10th maxillary alveolus from the end of the tooth row.

ALMNH 1002 does not share elements with the holotype and thus cannot be definitively referred to D. schwimmeri. This specimen has been tentatively referred to the species based on possession of mediolaterally broad terminal neural spines, transverse processes are nearly on the same plane as the postzygapophyses, and some osteoderms have moderately inflated keels. Additionally, its large size is shared with the holotype and TMM 45973-1. Geological context also unites both ALMNH 1002 and the most complete skull and lower jaw referable to D. schwimmeri (TMM 43973-1). They are both from the Mooreville Formation, which underlies the Coffee Sand Formation in Mississippi (Dockery and Jennings, 1988), which preserves the D. schwimmeri holotype (MMNS VP-256).