I review the fossil felid literature, researching the early history of the genus Pseudaelurus in Europe. I examine type Pseudaelurus specimens from Europe, Asia, and North America and emend the generic diagnosis. A large body of new material from the Frick Collection of the American Museum is described and specimens are assigned to one of six species. One species is new and one is transferred from Lynx. New material includes two partial skeletons assigned to two separate species, several skulls, one skull with associated lower jaws and intact basicranium, numerous maxillary and lower jaw specimens, and isolated postcranial items. Cranial, basicranial, and postcranial material of the Frick specimens is compared to that of European taxa as well as to modern felids. A cladistic analysis of 10 taxa and 23 characters produces hypotheses of felid relationships.
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22 May 2003
Phylogenetic Systematics of North American Pseudaelurus (Carnivora: Felidae)
TOM ROTHWELL
Author Affiliations +
TOM ROTHWELL*
*Collections Assistant, Division of Paleontology, American Museum of Natural History. rothwell@amnh.org
*Collections Assistant, Division of Paleontology, American Museum of Natural History. rothwell@amnh.org
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ARTICLE - INTRODUCTION
- Institutional Abbreviations
- Early Taxonomic History of the Genus Pseudaelurus
- Review of the genus Pseudaelurus in Europe, Asia, and Africa
- North American Review
- SYSTEMATIC PALEONTOLOGY
- CLASS MAMMALIA LINNAEUS, 1758
- Genus Pseudaelurus Gervais, 1850
- Type Species: Pseudaelurus quadridentatus (Blainville, 1843) (= Felis quadridenta Blainville, 1843)
- Included Species: Type species and Pseudaelurus intrepidus Leidy, 1858; Pseudaelurus turnauensis Hoernes, 1882; Pseudaelurus lorteti Gaillard, 1899; Pseudaelurus marshi Thorpe, 1922; Pseudaelurus romieviensis Roman and Viret, 1934; Pseudaelurus aeluroides Macdonald, 1954; Pseudaelurus guangheensis Cao et al.1990; and Pseudaelurus cuspidatus Wang et al., 1998; Pseudaelurus validus, Rothwell, 2001.
- Distribution: Early to middle (MN3 to MN9) Miocene of Europe; early to middle (late Hemingfordian to late Barstovian) Miocene of North America; early to middle (Xiejian to Shangwangian) Miocene of Asia; early Miocene of Africa.
- Generic Diagnosis: Members of Felidae with the following derived characters: absence of p1 and m2, m1 with reduced metaconid and talonid, P2 with one root, paroccipital process cupped about the posterior surface of an enlarged caudal entotympanic, tall coronoid process, hypoglossal foramen sharing a common depression with the posterior lacerate foramen, and a blunt and rectangular-shaped metacarpal 1. These derived characters are seen in combination with the primitive characters of presence of p2 and alisphenoid canal. Pseudaelurus differs from extant felid genera in c cross section showing flattened inner surface and posterior trenchant edge, presence of p2, m1 with variable metaconid and reduced talonid, and alisphenoid canal present. Differs from Metailurus in presence of alisphenoid canal and p2, absence of enlargement of mental ridge. Differs from Nimravides in smaller size and absence of any ventral mandibular mental ridge enlargement. Differs from Proailurus in absence of p1 and m2.
- Pseudaelurus validus Rothwell, 2001
- Holotype: F:AM 62128, skull with left and right I3, left C, broken right C, single-rooted alveoli for P1 and P2, left and right P3–M1. Articulated lower jaws with left i3, left and right c, left and right single-rooted alveoli for p2, left and right p3–m1. Postcrania: right and left humeri, right and left radii, right and left ulnae, left manus, articulated right manus, distal fragment of left femur with patella, left tibia, right tibial fragment, left and right fibular fragments, right pes, articulated left pes, partially prepared elements in plaster jacket, including exposed scapulae, ribs, vertebrae.
- Referred Specimens: Sheep Creek Fauna, Sheep Creek Formation (late Hemingfordian), Sioux County, Nebraska: F:AM 61827, right ramus with c, alveolus p2, p3, p4, broken m1, Greenside Quarry; F:AM 61837, left maxillary fragment with I3, C–M1, right tibia and fibula, partial right radius, partial right ulna, astragalus, vertebrae and right fourth metatarsal, Head of Pliohippus Draw.
- Lower Snake Creek Fauna, Olcott Formation (early Barstovian), Sioux County, Nebraska: F:AM 61834, complete skull with upper dentition, zygomatic arches, intact basicranium and associated lower jaws (F:AM 61829), Humbug Quarry; F:AM 61803, left maxilla with I3 alveolus, C, alveolus P1 and P2, P3–M1, Humbug Quarry; F:AM 61833, partial skull with upper dentition and partial right zygomatic arch, Quarry 3 (Far Surface Quarry); F:AM 61832, left ramus with i3, c, p2, broken p3, p4 and broken m1, East Wall Quarry; F:AM 61830, partial left ramus with p4, m1, Quarry 3 (Far Surface Quarry); F:AM 61828, left and right rami with left and right c, p2 alveoli, p3–m1, right humerus, left radius, left and right tibiae, Echo Quarry; F:AM 61835, a nearly complete skull with upper dentition and intact basicranium, Echo Quarry; F:AM 61836, skull fragment with left P4, left and right partial rami with partial dentitions, maxillary fragment with canine tooth, left radius, Echo Quarry.
- Distribution: Late Hemingfordian of New Mexico, late Hemingfordian and early Barstovian of Nebraska.
- Diagnosis: Differs from other species of Pseudaelurus by the combination of large size, long distance between c and p3, extremely reduced or absent metaconid on m1, and robust dentary with large and erect rectangular-shaped coronoid process. P. validus overlaps in size with P. intrepidus and P. marshi in North America and P. quadridentatus in Europe but can be differentiated from these species by the longer c–p3 length in P. validus, which exceeds the length of its m1, and by its large, erect, and rectangular coronoid process.
- Description and Comparisons: The holotype has been previously described in detail (Rothwell, 2001). The dentary bone of P. validus is taller and wider than similar-sized specimens of P. marshi or P. intrepidus. The coronoid process is wider and more erect than P. marshi or P. intrepidus and is much taller than in the earlier European taxon Proailurus lemanensis (fig. 10). The size and erectness of the coronoid process of P. validus resembles more the temporally equivalent P. skinneri.
- F:AM 61829 (fig. 11) has the large distance between c and p3 that is distinctive of P. validus. In every observed lower jaw of P. validus, except for the crushed and restored holotype, the c–p3 distance exceeds the length of m1. Lower jaws assigned to P. intrepidus have c–p3 length ranging from 68% to 98% of the m1 measurement. In P. marshi, the type lower jaw (YPM 12865) has a c–p3 length 54% of the m1 length, and in the paratype (YPM 12815) it is 66%. In my study of modern felids, both male and female lions (Panthera leo) have an average c–p3 length that measured 110% of the m1 length (see tables 4, 5), a proportion similar to P. validus. In the puma, Felis concolor, the average c–p3 length was 66% of the m1 length in females, and 69% in males, corresponding more to the condition in P. intrepidus and P. marshi.
- The lower dentition of P. validus is similar to that in other species within the genus. None of the specimens has p1. The p2 is usually indicated by a single-rooted alveolus positioned medial of the line of tooth row, as in the type. The left lower jaw of F:AM 61829 (fig. 11) has a two-rooted p2. This is the earliest example of a two-rooted p2 in North America. The number of roots of p2 varied in early European felid specimens (Dehm, 1950). A two-rooted p2 is routinely seen in the European taxon Proailurus (Filhol, 1888; Peigné, 1999), generally accepted as the earliest member of Felidae (Hunt, 1989).
- The height of p3 in P. validus is consistently lower than p4. The primitive condition of equal-sized p3 and p4 can be seen in the European aeluroid taxa Stenogale and Haplogale (Peigné, 1999). The derived condition of p3 smaller than p4 is present in Proailurus, Pseudaelurus, and modern felids. The p4 of P. validus has a large posterior accessory cusp. The m1 metaconid is more reduced than in other early and middle Miocene felids. In seven lower jaw specimens assigned to P. validus that have m1 present, four have a greatly reduced (for Pseudaelurus) metaconid (fig. 12) and three have no detectable metaconid. The derived condition of a reduced metaconid contrasts with the m1 of Pseudaelurus skinneri, n. sp. which has a very distinct metaconid accompanied by an abridged talonid. The reduced metaconid morphology also differs from the later P. intrepidus, P. marshi and P. stouti, species whose m1 have a varying incidence of a more distinct metaconid.
- The upper dentition of P. validus has been described for the type specimen, but is better preserved in many of the referred specimens (figs. 13–15). P3 of P. validus is large, with a primary cusp that is approximately the same size as the paracone of P4 (fig. 15). The posterior accessory cusp of P3 is also large and distinct and is approximately the same height and size as the parastyle of P4. Posterolateral to the posterior accessory cusp of P3 is a prominent cingular cusp. This cingular cusp is at the same level and of the same height and size as the anterior accessory cusp of the adjacent P4. These corresponding cusps of P3 and P4 can be seen in the lateral view of figure 15. The P4 of P. validus is wide, not compressed mediolaterally, as in modern felids. The P4 has a prominent protocone that projects anterolingually from the lingual surface of the paracone of P4 (fig. 14). In all referred specimens that have M1, the parastyle blade is contiguous with the metastyle blade of P4. This morphology elongates the upper carnassial blade in this species.
- The ventral aspect of the skull of F:AM 61835 is in excellent state of preservation (fig. 16). Portions of the basicranium of this specimen have been described and illustrated previously (Neff, 1983; Hunt, 1998). The ectotympanic is thick and massive. The anterior crus have two components. There is a large anterolateral attachment to the squamosal and a thick and wide medial articulation with the lateral margins of the basioccipital and basisphenoid. The suture between the basioccipital and basisphenoid cannot be identified. The left auditory bulla has been dissected (fig. 17). The course of the septum bullae can be seen to run diagonally, along the posterior wall of the ectotympanic, across the crest of the promontorium, from a point just medial to the vagina processus hyoideus, anteromedially to a position considerably posterior to the anteromedial process of the auditory bulla. The course of the septum bullae demonstrates the level of anterior expansion of the caudal entotympanic in P. validus. The caudal entotympanic has advanced anteriorly to a level slightly posterior to the most anterior limit of the ectotympanic chamber. The caudal entotympanic chamber terminates posterior to the anteromedial process. This morphology is similar to the condition seen in Proailurus lemanensis (Hunt, 1998), but contrasts with modern felids whose thin-walled caudal entotympanic has advanced farther anteriorly. Posteriorly, the caudal entotympanic has invaded and emarginated the paroccipital process to a degree seen only in modern felids. For a more in-depth analysis of the structures of the auditory region of this specimen, see Hunt (1998: 46).
- On the ventral surface of the basioccipital of F:AM 61835, between the two bullae, are two round rugose areas of attachment for the paired rectus capitus ventralis muscles (fig. 16). These two muscle insertion areas are much larger and more expanded than on skulls of other species of Pseudaelurus. This increased area of attachment is seen also in F:AM 61834 skull (fig. 18). There is no evidence of a postglenoid foramen in either F:AM 61834 or F:AM 61835. The postglenoid foramen is present in the type skull of the earlier European felid Proailurus lemanensis (MNHN 1903–20). In the skulls of four species of extant felid that I studied (Panthera leo, Felis concolor, Lynx canadensis, Lynx rufus), the postglenoid foramen was variably present, although minute.
- The foramen ovale in F:AM 61834 and F:AM 61835 is located at the level of the anteroventrally facing glenoid fossa (figs. 19, 20). This agrees with the location of this foramen in the type specimen (F:AM 62128) and does not differ from modern species. The three skulls assigned to P. validus (F:AM 61834, 61835, 62128) have distinct anterior and posterior alisphenoid foramina, with the anterior alisphenoid foramen positioned anterodorsally to the posterior alisphenoid foramen. Careful examination of F:AM 61834 and F:AM 61835 reveals a patent foramen rotundum within the alisphenoid canal. The foramen rotundum opens in the general direction of the anterior alisphenoid foramen. This contrasts with the condition in modern felid skulls, in which the alisphenoid canal is absent. In extant felid species, the foramen ovale retains its position medial to the glenoid fossa, while the foramen rotundum is positioned farther anteriorly.
- In both F:AM 61834 and F:AM 61835, a well-developed external pterygoid fossa can be seen immediately ventral to the alisphenoid canal. Both of these skulls also have well-preserved palatine and pterygoid bones. The paired vertical plates of the palatine bones are parallel to each other when viewed from the ventral aspect. However, the paired pterygoid bones are not parallel, but rather reflect medially toward each other posteriorly, thus giving an oval shape to the area between the corresponding plates.
- Some extremely well-preserved postcranial bones from the early Barstovian Echo Quarry are referred to P. validus (F:AM 61828 and F:AM 61828-A). However, they do not differ in size or morphology from the type specimen (see Rothwell, 2001).
- Discussion: P. validus has a dentition that is for the most part primitive for felids, but some states are derived relative to Proailurus. P1, P2, and p2 of P. validus are vestigial and peglike. These teeth do not occlude. There is a great difference in size between the upper and lower second and third premolars. The third premolars (p3, P3) are robust and possess accessory cusps that assist in mastication. The well-preserved F:AM 61834 skull and its associated lower jaws (F:AM 61829) (figs. 11, 18) provide insight into early felid occlusion. The carnassial activity is centered at the carnassial notches of P4 and m1, as in all Carnivora. The shear activity of F:AM 61834 extends anteriorly to the anterior surface of P3, which occludes with the posterior surface of p3. This morphology is identical to the condition in modern felids. Posteriorly, the upper carnassial activity continues to the parastyle blade of M1 (M1 missing in F:AM 61834 skull, present in F:AM 61835 skull), which occludes with the reduced metaconid and talonid of m1. Modern felids, in which M1 is vestigial and the metaconid and talonid of m1 are absent, have lost the occlusal ability of M1. The erect coronoid process of P. validus agrees with the condition in the smaller, but temporally equivalent species, P. skinneri. Outgroup comparison to earlier fossil aeluroids such as Proailurus, Stenogale, Haplogale, and Stenoplesictis establishes this erect morphology of the ascending ramus as a plesiomorphic condition for the family Felidae.
- In both F:AM 61834 and F:AM 61835 the alisphenoid foramina are nearly perfectly preserved. Both skulls show evidence of the alisphenoid canal, foramen rotundum, and foramen ovale (figs. 19, 20). The primitive eutherian condition for these foramina (Novacek, 1986; Rougier, Wible et al. 1992) and their role in circulation (Davis and Story, 1943) have been previously described and illustrated. In a hypothetical primitive aeluroid, the mandibular branch of cranial nerve V exits the cranium via the foramen ovale. Entering the foramen ovale from outside of the skull is a branch of the carotid circulation via the maxillary artery. This branch of the maxillary artery enters the cranium and forms an anastomosis with the internal carotid circulation (Davis and Story, 1943). In this hypothetical aeluroid, the maxillary branch of cranial nerve V exits the cranial cavity via the neomorph foramen rotundum and enters the alisphenoid canal. The maxillary branch of the trigeminal nerve (V) then proceeds anteriorly in the alisphenoid canal and exits the skull via the anterior alisphenoid foramen. As it leaves the anterior alisphenoid foramen, the nerve branch is accompanied by the maxillary artery, which has just traversed the alisphenoid canal after entering the posterior alisphenoid foramen. This is the condition in Pseudaelurus validus. On the floor of the cranial cavity in F:AM 61835 (fig. 21) are seen three separate grooves associated with the three branches of the trigeminal nerve (ophthalmic, maxillary, and mandibular) as they exit the braincase via separate foramina.
- Modern felids have greatly increased the degree of anastomosis of the external and internal carotid circulations over the primitive condition, decreased the role and size of the internal carotid artery, and incorporated the maxillary artery into a complicated rete externum. However, in the area of the alisphenoid foramina, modern felids differ from P. validus only by lacking external evidence of passage of the maxillary artery—the alisphenoid canal. The primitive condition of an alisphenoid canal present in Pseudaelurus validus, and the derived state of absence of alisphenoid canal in Felis, supports the hypothesis that loss of the alisphenoid canal developed in parallel in the family Hyaenidae (Werdelin, 1996). Loss of the alisphenoid canal is another example of a character that should not be considered a synapomorphy for these two aeluroid families, as previously suggested (Wyss and Flynn, 1993).
- In the auditory region of Pseudaelurus validus, the caudal entotympanic chamber has expanded slightly beyond that seen in Proailurus (see Hunt, 1998: 35). This anterior expansion of the caudal entotympanic can be monitored by the emargination of the adjacent basioccipital (Hunt, 1998). Although the emarginated basioccipital ridge in P. validus and Proailurus lemanensis is similar, a greater percentage of the caudal entotympanic lies anterior to the petrosal in P. validus (fig. 17). In P. validus, the anteromedial process is formed by robust medial crus of the ectotympanic. This area of the basicranium in P. lemanensis is unknown. In modern felids, the caudal entotympanic has advanced farther anteriorly, invading the medial crus of the ectotympanic and leaving the anteromedial process to be formed mostly of thin-walled caudal entotympanic.
- Pseudaelurus skinneri, new species
- Holotype: F:AM 61812, left ramus with c, p2 alveolus, p3, p4 alveolus and m1.
- Type Locality: Hilltop Quarry, Sheep Creek Formation, Sioux Co., Nebraska.
- Referred Specimens: Sheep Creek Fauna, Sheep Creek Formation (late Hemingfordian), Sioux County, Nebraska: F:AM 61814, left partial ramus with c, alveolus of p2, p3–m1, Thistle Quarry; F:AM 61816, left partial ramus with broken c, alveolus of p2, p3–m1,Thistle Quarry; F:AM 61818, left partial ramus with broken alveolus c, alveolus of p2, p3, p4, broken m1, Hilltop Quarry; F:AM 61817, right partial ramus with broken alveolus of c, p3–m1, Long Quarry; F:AM 61810, left partial ramus with broken alveolus of c, alveolus of p2, p3–m1, Greenside Quarry; F:AM 61819, left partial ramus with broken alveolus of c, alveolus of p2, p3–m1, Buck Quarry; and F:AM 61813, maxillary fragment with alveolus of P2, P3–P4, Ashbrook Quarry.
- Age: Late Hemingfordian (Galusha, 1975; Skinner et al., 1977; Tedford et al., 1987).
- Distribution: Late Hemingfordian of Nebraska.
- Etymology: Species name in honor of Morris Skinner, a charter member of the Society of Vertebrate Paleontology who worked for the Frick Laboratory from 1927 to 1973 as a field worker, preparator, and curator.
- Diagnosis: Differs from all North American species by its unique size. P. skinneri has an m1 length range of 11.5–13.8 mm, larger than P. stouti. The next largest North American species, P. aeluroides, known only by the type specimen, has an m1 length of 15.6 mm. In size, P. skinneri overlaps only the European species P. lorteti and the Asian species P. cuspidatus and P. guangheensis. Pseudaelurus skinneri can be differentiated from these species by the following combination of characters: shorter c–p3 length, m1 with tall protoconid and reduced metaconid and talonid, P4 protocone projecting at an obtuse angle anterolingually. P. skinneri differs from the European species P. lorteti by a taller m1 protoconid which is consistently much taller than the paraconid. P. skinneri differs from the Asian P. cuspidatus by a shorter c–p3 length, lacking the pronounced anterior cingular cusps on p3 and p4, and by presence of a gently sloping posterior edge of m1. P. skinneri differs from the Asian P. guangheensis by P4 protocone projecting at an obtuse angle anterolingually.
- Description and Comparisons of Holotype: F:AM 61812, the type specimen of P. skinneri, has a dentary that is a well preserved (figs. 22–24). It is slender and gracile. Medially, fine details of a small mandibular symphysis can be seen along the anterior border of the ramus. A large mandibular foramen is positioned medially, beneath the origin of a slender, yet erect, coronoid process (fig. 23). This upright morphology of the coronoid compares favorably with the much larger P. validus, but contrasts with the more sloping processes seen in the later P. intrepidus and P. marshi. The lower canine has a posterior ridge, but the cross section is more elliptical and symmetrical than the medially flattened canine of P. validus. There is no evidence of a p1 as in the specimen of P. cuspidatus (Wang et al., 1998). A large single-rooted alveolus for p2 is between c and p3. The alveolus of p2 is slightly closer to p3 than it is to c, and is situated lingual of an axis between c and p3. The distance between c and p3 is short. A short c–p3 length is also seen in P. marshi and P. aeluroides, but contrasts with the long c–p3 length seen in P. validus. The p3 of F:AM 61812 has a fractured crown, but the anterior and posterior cingular cusps are present. The anterior cingular cusp is minute, which differs from the more prominent anterior cusp described in P. cuspidatus but agrees with other species of Pseudaelurus. The large two-rooted p4 alveolus has a posterior root that is much larger than the anterior. Three mental foramina are present on the lateral surface. The largest and most anterior of these is at the level of the p2 alveolus.
- The m1 is well preserved, missing only a sliver of the anterior border of the paraconid. The carnassial notch is deep, narrow, and open to a level that is even with the reduced talonid. The protoconid is much taller than the paraconid, which agrees with the condition in P. cuspidatus. This degree of disparity in the height of paraconid and protoconid is not seen in other North American species. On the posterior margin of the paraconid is a reduced but distinct metaconid, aligned with the axis of the protoconid (fig. 22). The reduced metaconid is not lingually positioned as in P. cuspidatus, and it blends into a reduced but prominent talonid.
- Description and Comparisons of Referred Material: The greater height of m1 protoconid described in the type specimen (F:AM 61812) is seen also in F:AM 61816 (fig. 25) and F:AM 61817 (fig. 26). All of the m1s have a prominent metaconid and distinct talonid. The presence of a metaconid in other North American species of Pseudaelurus is variable. F:AM 61813, the maxillary fragment, is the only upper dentition known for the species (fig. 27). P3 has a prominent posterior accessory cusp as well as a basal cingular cusp. On the labial side of P4 there is a small accessory cusp at the base of the parastyle. This morphology of P3 and P4 agrees with P. validus. The P4 of F:AM 61813 has a prominent protocone (fig. 28). The slenderness and the angle of the P4 protocone are similar to the P4 in the type skull of Proailurus lemanensis (MNHN1903–20) (fig. 29). The protocone lies at a more obtuse angle anterolingually than is seen in P. intrepidus and P. marshi. This less acute angle formed by the protocone of P4 compares well with P. validus. M1 of F:AM 61813 is fragmented. Only the lingual half of the tooth remains. However, it is obvious that this M1 was multicusped. This agrees with the condition in P. validus, in contrast to the vestigial M1 seen in modern felids.
- Discussion: Material referred to P. skinneri is restricted to lower and upper jaw specimens from late Hemingfordian localities of North America. Without cranial and postcranial information, it is difficult to hypothesize the relationship of P. skinneri with other felids. One possibility is that it is most closely related to the other similar-sized species found on other continents. Fossils of P. lorteti of Europe are similar in size and morphology and are temporally equivalent to P. skinneri. This is not unlike the situation seen today with Lynx lynx of Europe and Lynx canadensis of North America. In Asia, Pseudaelurus cuspidatus, P. guangheensis, and P. lorteti are all similar in size to P. skinneri and all have been reported from middle Miocene localities. Conversely, there is no reason to expect the diversity of early felids in North America to reflect the situation in Europe or Asia. P. skinneri along with P. validus are among the earliest felids to arrive in North America. It is possible that P. skinneri is more closely related to P. validus than to Eurasian species. Perhaps P. skinneri and P. validus represent part of an early North American radiation of felids. Without additional material (e.g., basicrania and postcrania) however, it will be difficult to determine the relationship of P. skinneri to other Miocene felids.
- Pseudaelurus intrepidus Leidy, 1858
- Holotype: USNM 124 (AMNH cast 10396), left ramus with i3, alveolus p2, p3–m1 from the Valentine Sands, Bed F, “Loup Fork”, Valentine Formation (late Barstovian (Webb, 1969), Cherry County, Nebraska (fig. 5).
- Referred Specimens: Lower Snake Creek Fauna, Olcott Formation (early Barstovian), Sioux and Dawes counties, Nebraska: YPM PU 12081, right partial ramus with broken c, alveolus p2, p3–broken m1, Sinclair Draw; AMNH 17212, right partial ramus with broken c alveolus, alveoli of p2 and p3, p4–m1, Sinclair Draw; F:AM 61806, left ramus with broken c, p2 alveolus, p3–m1, Humbug Quarry; F:AM 61804, right ramus with alveolus of I3, broken canine, and p2–m1, Quarry 2; F:AM 61805, right ramus with alveolus of canine and p3–m1, Quarry 2; F:AM 61831, right ramus with alveolus of canine, alveolus of p2, broken p3, and p4–m1, Echo Quarry; F:AM 61564, left partial ramus with p3–broken m1, Version Quarry; AMNH 18271, with broken c, alveolus of p2, broken p3–m1, East Surface Quarry.
- Trinity River Local Fauna, Fleming Formation (early Barstovian), San Jacinto County, Texas: AMNH 18271, right partial ramus with alveolus of c, alveolus of p2–p4 and m1, pit no. 1.
- Tonopah Local Fauna, Siebert Formation (early Barstovian), San Antonio Mountains, Nye County, Nevada: LACM (CIT) 791, partially restored skull with upper dentition and basicranium, locality 172; LACM (CIT) 1233, maxillary fragment with C–M1, and right ramus with i3–c, p2–m1, locality 172; LACM (CIT) 772, left partial ramus with p3–m1, locality 172; LACM (CIT) 1234, left partial ramus with p3–m1, locality 172.
- Green Hills Fauna (early Barstovian), Barstow Formation, San Bernardino County, California: F:AM 61923, right partial ramus with broken c, p2–p3, broken p4, and m1, Upper Steepside Quarry; F:AM 27331, right crushed ramus with c, p2–m1 and left ramus with broken c, p2–m1, “Green Hills, Box 72, 1926”; F:AM 27327, left partial ramus with c, p2–m1, “Green Hills, Box 59, 1925”.
- Pawnee Creek Formation (early Barstovian), Big Springs Pit, Weld County, Colorado: F:AM 61842, left partial ramus with alveolus p3, p4–m1.
- Second Division Fauna, Barstow Formation (early Barstovian), San Bernardino County, California: F:AM 61933, left and right rami with i3–c, p2–m1, Mayday Quarry.
- First Division Fauna, Barstow Formation (late Barstovian), San Bernardino County, California: F:AM 61910, partial skeleton with left and right rami with i3, c, p2–m1, right humerus, radius, tibia, and partial femur, left articulated forearm (radius, ulna, and manus) with prepared metapodials, left tibia, left partial humerus and femur, partial axis, metatarsal fragments, unprepared vertebrae, and partial scapulae, 6 ft under New Year Quarry; SBCM L1816–5224, crushed skull with broken I1–M1, and left and right rami with broken I–c, p2–m1, Robbins Quarry.
- Valentine Formation (late Barstovian), Elliot Place, Brown County, Nebraska: AMNH 25209, right partial ramus with alveoli of i1–i3, c, alveolus of p2, p3–m1;
- Valentine Formation (late Barstovian), Cherry County, Nebraska: ANSP 11297, right ramus with i2, broken i3 and c, alveolus of p2, p3–m1 (paratype), “Valentine Sands, Bed F, Loup Fork” (Webb, 1969).
- Distribution: Early Barstovian of Texas, Colorado, and Nevada, early and late Barstovian of Nebraska and California.
- Diagnosis: Differs from similar-sized species of Pseudaelurus by the c–p3 length and coronoid process morphology. P. intrepidus has an m1 length range of 15–20 mm, overlapping only with P. validus and P. marshi in North America and P. quadridentatus in Europe. P. intrepidus can be differentiated from P. validus by its shorter c–p3 length and by its slender and sloping coronoid process. P. intrepidus can be differentiated from P. marshi by its longer c–p3 length and by a taller and wider dentary. P. intrepidus can be differentiated from P. quadridentatus by its longer c–p3 length, and by having an m1 with larger talonid and a better developed, larger metaconid.
- Description and Comparisons: In Leidy's (1858) original description, he described the type lower jaw ramus (USMN 124, AMNH 10396) (fig. 5) as being “intermediate in size to the Panther (Felis concolor) and the Lynx (Felix canadensis).” This specimen is longer, wider, and deeper than a modern lynx (Lynx canadensis). Its dentition is closer in size to that of the puma (Felis concolor). The dentary is wide and deep below the tooth row. The lower dentition of P. intrepidus is similar to that of other species within the genus. The c is flattened medially and has a distinct posterior trenchant edge. The p2 alveolus was single-rooted and was positioned midway in the diastema between c and p3 (fig. 5). The distance between c and p3 is long, measuring 76% of the m1 length. This is in contrast to P. marshi, which has a shorter c–p3 length that measures 54% of its m1 length in the type specimen, and P. validus, which has a c–p3 length that exceeds the length of m1. The slender coronoid process extends posterodorsally from a deep masseteric fossa. This contrasts with the larger, wider, and more erect coronoid process in P. validus, but is indistinguishable from P. marshi specimens.
- The earliest specimens of P. intrepidus are seven rami from various early Barstovian localities of the Lower Snake Creek Fauna of Nebraska. F:AM 61804 (fig. 30) is a right ramus from East Surface Quarry in Sioux County from this early group. These early Barstovian P. intrepidus differ from the late Barstovian holotype in lacking the pronounced chin or thickening of the dentary below the canine. Matthew's ramus of P. intrepidus sinclairi (AMNH 17212) (fig. 31) is another early Barstovian lower jaw of Pseudaelurus intrepidus. In spite of its historical status and “variety” designation, it does not differ appreciably from the type specimen.
- I am unable to differentiate P. intrepidus and P. marshi material that is unaccompanied by a lower jaw. Therefore, diagnosed upper dentitions of P. intrepidus are not common. I am aware of only three. The earliest is from the Tonopah locality reported by Stock (1934): a maxillary fragment with an associated partial ramus (LACM CIT 1233) (fig. 32). P1 and P2 are both single-rooted. The P4 has a prominent protocone that projects anterolingually. As in P. validus and P. skinneri, the anterior surface of P4 has a prominent parastyle with a small but distinct accessory cusp. The P4 morphology of P. intrepidus is better seen in F:AM 61910 (fig. 33), but this crushed specimen lacks M1. The third Pseudaelurus intrepidus specimen with upper dentition is SBCM L1816–5224, a late Barstovian partial skull from the Barstow Formation. It does not differ from the other two P. intrepidus skulls.
- In addition to the maxillary fragment, Stock (1934) described a partially restored skull (LACM (CIT) 791) (fig. 34). This was the first skull of the genus Pseudaelurus described. It was also the only Pseudaelurus skull described until the description of the Nambé felid, P. validus (Rothwell, 2001). Other felid skulls in the Frick-AMNH collection have been featured in a basicranial study (Hunt, 1998), but there was no attempt at assigning genera and species. There is considerable plaster repair and replacement in the area of hard palate, zygomatic arches, and frontal bones of LACM (CIT) 791. There is no accompanying lower jaw. The upper dentition of the Tonopah skull (LACM (CIT) 791) agrees with the Tonopah maxillary fragment (LACM (CIT) 1233) in size and morphology. The occlusal surface of M1 is contiguous with the P4 carnassial blade (fig. 35). This characteristic of the upper carnassial apparatus in specimens of P. intrepidus agrees with the P. validus skulls.
- The paroccipital process of the Tonopah skull, assigned to P. intrepidus, is cupped about the posterior surface of the caudal entotympanic, pointing caudoventrally away from the posterior surface of the bulla as a distinct process. The anterior portion of the sagittal crest has been estimated in plaster by a preparator, but the caudal portion and the nuchal crest resemble P. validus. The alisphenoid canal can be seen on both sides of the Tonopah skull. The size and location of these foramina do not differ from those seen in other skulls assigned to Pseudaelurus. The other two skulls that I assign to P. intrepidus are F:AM 61910 and SBCM L1816–5224. The size, dentition, and cranial foramina of these crushed specimens do not differ from the skull described by Stock (1934).
- Postcranial information on Pseudaelurus intrepidus is provided by F:AM 61910. The postcranial elements do not differ morphologically from F:AM 62128, the partial skeleton from the Nambé Member in New Mexico assigned to P. validus (Rothwell, 2001). However, the metacarpal measurements of the P. intrepidus skeleton are relatively longer than those of P. validus specimen (table 1). The occurrence of longer metacarpals is similar to modern felids and differs from the shorter metacarpal form seen in Proailurus lemanensis and P. validus (figs. 36–38).
- Discussion: Pseudaelurus intrepidus is the only species of Pseudaelurus in North America that has been described in the literature more than once (Sinclair, 1915; Matthew, 1918; Stock, 1934). Lower jaw specimens of P. intrepidus are abundant in the Frick-AMNH collection and come from Barstovian localities of Texas, Colorado, Nevada, Nebraska and California. I studied 22 lower jaws that I assigned to P. intrepidus. Only three of these lower jaws are associated with other material (e.g., cranial, maxillary, postcranial).
- The dentition of P. intrepidus does not differ significantly from other North American species of Pseudaelurus. However, P. intrepidus is among the earliest felids to display the derived condition of a sloping and slender vertical ramus of the lower jaw. The Lower Snake Creek Fauna, in the early Barstovian of North America, has felids with the primitive coronoid process (P. validus) as well as three species with vertical rami that display the derived condition (P. intrepidus, P. marshi and P. stouti). In the late Barstovian, all felids studied have the derived sloping coronoid process seen today in modern felids (fig. 10).
- The prominent chin seen in late Barstovian specimens of P. intrepidus leads to speculation that this species could be ancestral to one or more of the many machairodont felid forms seen in the late Miocene. This prominent chin, seen also in late Barstovian P. marshi, is a thickening of the dentary on the ventral surface below the lower canines. The ventral thickening of the dentary is associated with an elongation of the mandibular symphysis. It is well demonstrated in the type specimens of P. intrepidus and P. marshi (figs. 5, 6). Early specimens of these two species lack these characters (fig. 30). Numerous authors have included early specimens of machairodont felids in the genus Pseudaelurus (Andrews, 1914; MacDonald, 1948b, 1948a; Ginsburg, 1978). Indeed, Pseudaelurus has been designated as a likely ancestor of the machairodont North American felid Nimravides (fig. 8) (Baskin, 1981; de Beaumont, 1990).
- None of the three P. intrepidus skulls (LACM (CIT) 791, SBCM L1816–5224, F:AM 61910) is well preserved. Cranial and basicranial information on P. intrepidus is limited. However, the postcranium of P. intrepidus (F:AM 61910) does allow comparison with other taxa. Although conclusions made from one skeleton must be provisional, it appears that late Barstovian P. intrepidus had different proportions of its limb bones. In figure 36, I have contrasted the P. intrepidus data with the earlier P. validus postcranium. The y-axis or standard specimen is the Proailurus lemanensis skeleton described by Filhol (1888). The P. validus data are reasonably vertical and therefore similar to P. lemanensis. Thus, their limb proportions are comparable. The P. intrepidus skeleton (F:AM 61910) is different. In the front limb, the metacarpal bone is relatively larger. In the hind limb, the femur has decreased in relative size, while the tibia has increased. This form compares favorably with modern felid skeletons. In figure 37, data from L. issiodorensis (Kurtén, 1978), the suspected ancestor of Lynx lynx and Lynx canadensis (Werdelin, 1981), is added for comparison. In figure 38, modern taxa are also included for comparison. P. intrepidus shares the modern skeletal form of greater relative metacarpal length in the front limb and increased tibial length in the hind limb.
- Pseudaelurus stouti, new combination
- Lynx stouti Schultz and Martin, 1972
- Type Specimen: UNSM 25490, partial skull including articulated maxillae and premaxillae with upper dentition, articulated mandible with left and right i1–c, left p2, right alveolus of p2, left and right p3–m1, left petrosal, atlas.
- Type Locality: W2, 6 miles west and 2 miles north of Chimney Rock, SW;q1, T12N, R55W, from a buff very fine sandstone just below a prominent concretionary zone, Ogallala Group (late Barstovian), Logan County, Colorado.
- Age: Late Barstovian.
- Associated Fauna: Sand Canyon Fauna.
- Referred Specimens: Lower Snake Creek Fauna, Olcott Formation (early Barstovian), Sioux County, Nebraska: F:AM 61801, partial left ramus with broken c, alveolus p2, p3–m1, Quarry 2; F:AM 25471, partial left ramus with alveolus i3, c, alveolus p2, p3–m1, West Sinclair Draw.
- Sand Canyon Formation, Dawes County, Nebraska: AMNH 140227, partial radius, Observation Quarry.
- Skull Ridge Member, Tesuque Formation (early Barstovian; Tedford and Barghoorn, 1997)), Santa Fé County, Española Basin, New Mexico: F:AM 61931, left partial ramus with c, p2–broken m1; AMNH 140228, right partial ramus with broken c, alveolus of p2, broken p3–p4, broken alveolus of m1, Joe Rak Wash.
- Santa Cruz sites, Tesuque Formation (late Barstovian; Tedford, 1981; Tedford and Barghoorn, 1997), Española Basin, Santa Fé County, New Mexico: F:AM 27456-A, articulated lower jaw fragment with left i1–i3, left c, broken right c, alveolus of left p2, right p2, left and right p3–broken m1, Red layer, 2nd wash locality, F:AM 27455, right partial ramus with alveoli i1–i3, broken c, p2 and p3 alveolus, p4–m1, no locality.
- Cerro Conejo Member, Zia Formation (late Barstovian; Tedford and Barghoorn, 1997), Sandoval County, northern Albuquerque Basin, New Mexico: F:AM 61901, left partial ramus with c, p2–m1, Rincon Quarry.
- Distribution: Early Barstovian of Nebraska, late Barstovian of Colorado, and early and late Barstovian of New Mexico.
- Diagnosis: Differs from all other species of Pseudaelurus by its small size. P. stouti has an m1 length range of 8–9 mm, distinctly smaller than the next largest North American species, P. skinneri, with an m1 range of 11.5–13.5 mm. P. stouti is approximated in size only by the smallest and earliest European species, P. turnauensis, with its m1 range of 9.3–12.8 mm.
- Description and Comparisons of Type Specimen: UNSM 25490 (figs. 39–42). This is a very small and slender felid. The lower canine is flattened on the inner surface, and the posterior surface is rounded. This differs from the sharper rear edge seen in the lower canines of larger species. A single-rooted p2 can be seen on the left lower jaw (fig. 39). There is a single-rooted alveolus on the right side. The left p2 is closer to p3 than to c and is lingual of midline, typical of the genus. The p3 is as tall as p4, with a small posterior cingular cusp. The distance between c and p3 is 5.74 mm, which is relatively short, similar to the condition in P. marshi and P. aeluroides. A reduced metaconid is present on the posterior surface of the protoconid of m1, above a prominent talonid. The protoconid is taller than the paraconid, and the carnassial notch is open and deep to a level above that of the talonid. There is no evidence of m2 on either ramus. The dentary is convex below the tooth row. Posteriorly, the horizontal ramus terminates in a slender and pointed angular process.
- The left and right maxillary bones contain a full complement of four upper premolars (fig. 40). Present also are the zygomatic arches and the squamosal fragments that contain the jaw articulations (Schultz and Martin, 1972). The upper incisors are aligned in a tight row with a slight arc (fig. 40). The third upper incisors are significantly larger than the equal-sized I1 and I2. This upper incisor morphology agrees with earlier Pseudaelurus skulls as well as modern felids. The left C has a fractured crown. The right C is complete. P1 and P2 are single-rooted. In occlusal view P4 has a low protocone projecting at an acute, anterolingual angle (fig. 41). In this respect, P4 is similar to modern felids, but contrasts with the condition seen in P. skinneri and P. validus, where the P4 protocone is robust and positioned at a more obtuse angle.
- The left petrosal of UNSM 25490 (fig. 42) is not as long as in modern felids (fig. 43). Its anterior portion ends more abruptly, affording a rectangular appearance. Medially, there is no evidence of a petrosal flange to rest upon the basioccipital, as is seen in Proailurus lemanensis and Pseudaelurus validus. Posteriorly, there is little or no apron caudal to the fenestra rotunda, as is seen in some primitive aeluroids such as Stenogale julieni (Hunt, 1998). However, a vestigial ventral process of the promontorium is present, but does not contain a facet to indicate where the ectotympanic rested. In this respect, it agrees with the condition of modern felids.
- Description and Comparisons of Referred Specimens: In addition to their small size, the seven P. stouti lower jaws from the American Museum are distinguished by characters that are considered primitive for fossil felids. F:AM 27456A has a prominent metaconid and talonid on the m1 (figs. 44, 45). F:AM 27456a has a p3 that is tall, close in height to p4. This is a primitive state for p3 and p4 and can be seen in the holotype (UNSM 25490), F:AM 61931 (fig. 46), as well as in the early aeluroids Stenoplesictis, Stenogale, and Haplogale (Peigné, 1999). The advanced state of a p4 that is larger than p3 is seen in Proailurus as well as in modern felids. I have not seen this condition of similar-sized p3 and p4 in other North American species of Pseudaelurus.
- None of the specimens of P. stouti has evidence of p1. Of 18 lower jaws from Wintershof-West (early Miocene, MN3) assigned to P. transitorius Depéret (= P. turnauensis Hoernes), only 2 displayed evidence of p1 (Dehm,1950). The only other reference to a p1 of Pseudaelurus of which I am aware is a partial right ramus from the Northern Junggar Basin, China (Wang et al., 1998). This specimen also displayed the unusual combination of presence of p1 (alveolus) and lack of p2. AMNH 140228 has a p2 alveolus with two roots (fig. 47). This is uncommon in North American felids. While studying over 100 felid lower jaw specimens of early and middle Miocene age, this is only the second North American specimen with evidence of a two-rooted p2. The type specimen of Proailurus lemanensis (MNHN S.G. 3509a), from the early Miocene of France, has a p2 with 2 roots. In the 18 felid lower jaws from Wintershof-West, 4 had a p2 with 2 roots and 4 had alveoli with an “hourglass” configuration (Dehm, 1950) (fig. 48).
- Discussion: P. stouti is distinguished by its small size and primitive felid characters. It is the smallest species of Pseudaelurus described (fig. 49). This small felid, with the authors acknowledging similarities to Pseudaelurus, was originally assigned to the genus Lynx (Schultz and Martin, 1972). This was reasonable considering that the occasional appearance of primitive dental characters (m1 with metaconid and talonid, presence of m2) in modern Lynx lynx has created controversy concerning the phylogenetic position of that species (Kurtén, 1963; Werdelin, 1987). However, the earliest fossil evidence of the genus Lynx is the early or middle Pliocene appearance of L. issiodorensis throughout the northern hemisphere. Lynx issiodorensis is the suspected ancestor of L. lynx, L. canadensis, L. rufus, and L. pardina (Werdelin, 1981). Early L. issiodorensis lower carnassials do not have a talonid-metaconid complex or m2 (Kurtén, 1978). There is no mention of any p1, p2, or m2 in L. issiodorensis. The dentition of L. issiodorensis is therefore more similar to modern Felis, as is the postcranial skeleton. Also, L. issiodorensis is a large felid. Kurtén (1978) reported m1 measurements of L. issiodorensis ranging from 14.6–16.3 mm in length, comparable in size to P. intrepidus and P. marshi, or the modern taxon Felis concolor. L. issiodorensis is much larger than modern L. lynx or L. canadensis specimens that I examined at the American Museum. Although the type specimen of Lynx stouti was originally described as “a felid the size of Lynx issiodorensis” (Schultz and Martin, 1972), it is much smaller with m1 length of 8–9 mm. A felid specimen with P1, P2, and m1 with a metaconid and talonid is characteristic of the genus Pseudaelurus. I therefore assign the type, UNSM 25490, and other specimens to the genus Pseudaelurus as Pseudaelurus stouti.
- The presence of equal-sized p3 and p4 in P. stouti may indicate adaptation to a food source. An elongated p3 crown was considered an autapomorphy for the extant black-footed cat, Felis nigripes (Salles, 1992). A study of the black-footed cat revealed a diet consisting of 43% arachnids (Kitchner, 1991). P. stouti is the sixth species of Pseudaelurus to be recognized in North America. P. stouti increases the diversity of felids in the Barstovian of North America to five species (P. validus, P. intrepidus, P. marshi, P. aeluroides and P. stouti) The diversity of North American early and middle Miocene felids now resembles the more continuous fossil felid record of Europe. In Europe, four different-sized species of Pseudaelurus (Heizmann, 1973; Ginsburg, 1983) are found throughout the early and middle Miocene.
- Pseudaelurus marshi Thorpe, 1922
- Holotype: YPM 12865 (AMNH 13506 cast), articulated left and right rami with left i2, i3, left and right c, left alveolus of p2, right p2, left and right p3–m1, from Valentine Formation, Niobrara River, near mouth of Minnechaduza Creek (late Barstovian) (Webb, 1969), Cherry County, Nebraska.
- Paratype: YPM 12815 (AMNH 133505 cast), left ramus with broken c, alveolus of p2, p3–p4, broken m1, from Gerry's Ranch, Ogallala Group (early Barstovian), Weld County, Colorado.
- Referred Specimens: Lower Snake Creek Fauna, Olcott Formation (early Barstovian), Sioux County, Nebraska: F:AM 61808, left ramus with c, alveolus of p2, p3–m1, Echo Quarry; AMNH 22401, left partial ramus with alveolus of c, p3–broken m1, Ashbrook Pasture; AMNH 22404, right partial ramus with alveolus c and alveolus p2, broken p3–m1, Ashbrook Pasture; F:AM 61807, left partial ramus with alveolus of c, p2, p3–m1, Quarry 2; F:AM 61809, left partial ramus with alveoli of c and p2, p3–m1, Quarry 2; AMNH 22398, partial right ramus with alveoli of i1–p4, m1, Ashbrook Pasture.
- Sand Canyon Formation (Early Barstovian), Dawes County, Nebraska: F:AM 61846, partial left ramus with alveolus of i3, c, alveolus of p2, p3–broken m1, Observation Quarry.
- Green Hills Fauna, Barstow Formation (early Barstovian), San Bernardino County, California: F:AM 61926, partial left ramus with p3–m1, Upper Steepside Quarry; F:AM 61921, right ramus with c, alveolus of p2, p3–m1, Upper Steepside Quarry; F:AM 61924, partial left ramus with broken c, p2 alveolus, p3–m1, Upper Steepside Quarry; F:AM 61918, partial left ramus with broken c, p3–m1, Upper Steepside Quarry; F:AM 61938, partial left ramus with i3–c, p3–m1, Turbin Quarry; F:AM 27337, left and right rami with c, p2–m1, Rak Division.
- Second Division Fauna, Barstow Formation (early Barstovian), San Bernardino County, California: F:AM 18008, crushed partial skull with upper dentition, occipital fragment, left partial ramus with c, alveolus of p2, p3–m1 and partial right ramus with c, p2–m1,Valley View Quarry.
- Trinity River Local Fauna, Fleming Formation (early Barstovian), San Jacinto County, Texas: F:AM 69331, partial left ramus with broken alveolus of c, alveolus p2, p3 and p4, m1, pit no. 1.
- First Division Fauna, Barstow Formation (late Barstovian), San Bernardino County, California: F:AM 61934, articulated lower jaw fragment with i3, alveolus of p2, p3–m1, Leader Quarry; F:AM 61916, partial right ramus with broken c, p3–m1, Leader Quarry; F:AM 61936, partial right ramus with c, alveolus of p2, p3–m1, Black Hill Quarry; F:AM 27317, left and right partial rami with left and right c, left and right alveolus of p2, broken p3–m1, White Layer, 0.5 mile below cabin; F:AM 61940, crushed skull with left and right I1–M1 and right ramus with i1–c, alveoli p2–p4, broken m1, Hidden Hollow Quarry.
- Pawnee Creek Formation, Big Springs Pit, Weld County, Colorado: F:AM 61841, partial right ramus with c, alveolus of p2, p3–m1.
- Cerro Conejo Member, Zia Formation (late Barstovian; Tedford and Barghoorn, 1997), Sandoval County, northern Albuquerque Basin, New Mexico: F:AM 62144, partial skeleton with crushed skull with I1–C, alveolus of P2, P3–M1, partial left ramus with c, alveolus of p2, p3–m1, left and right humerus, radius, ulna, femur and tibia, partial scapulae, vertebrae, articulated pelvis, left and right calcaneus, assorted left and right metatarsal bones, and assorted phalanges, Rincon Quarry.
- Pojoaque Member, Tesuque Formation (late Barstovian), Santa Fé and Rio Arriba counties, NM: F:AM 27457, partial articulated lower jaw with left and right lower dentition, left and right maxillary fragments with I3, C, P1, P2–M1, right calcaneus, partial humerus, Santa Cruz; F:AM 62135, skull fragment, left ramus with i2–c, p2 alveolus–m1, right partial ramus with separated c and p3–m1, vertebrae in matrix, partial femur, and assorted metapodials, south side of the Lobato branch of the South Fork of 3 Sand Hills Wash; F:AM 27453, partial skeleton, skull with upper dentition and intact basicranium, left dentary with i3, c, alveolus of p2, p3–m1, vertebrae, one rib, partial left articulated tarsus and metatarsus, Santa Cruz, field no. 13.
- Distribution: Early Barstovian of Texas, early and late Barstovian of Nebraska, California, and Colorado, late Barstovian of New Mexico.
- Diagnosis: Differs from all other species by combination of large size, short c–p3 length and slender and sloping coronoid process. P. marshi has m1 length that ranges from 14–19 mm, overlapping only with P. validus and P. intrepidus in North America and P. quadridentatus in Europe. P. marshi can be differentiated from P. validus by its much shorter c–p3 length and a slender and sloping coronoid process. P. marshi can be differentiated from P. intrepidus by shorter c–p3 length and dentary that is narrower and shallower below the tooth row. P. marshi can be differentiated from the European P. quadridentatus by its shorter c–p3 length and m1 with larger talonid and greater incidence of metaconid.
- Description and Comparisons: Thorpe's (1922) description of the type lower jaw (YPM 12865) listed most characters that differentiate P. marshi from other large species in the genus: smaller size and a more slender and shallower dentary below the tooth row. However, he did not mention the shorter c–p3 length that differentiates P. marshi from other large species of Pseudaelurus (fig. 50). There is no evidence of p1 on either ramus. A single-rooted p2 can be seen on the right ramus, an alveolus on the left ramus. The p3 is smaller and shorter than p4, and both p3 and p4 have prominent posterior accessory cusps. The m1 has a reduced, yet distinct metaconid and talonid. The paratype partial left ramus (YPM 12815) was originally described as having an m2 alveolus. I examined this specimen and a cast (AMNH 133505) (fig. 51). The posterior root of the broken m1 is exposed, forming a triangular area posterior to the broken m1 crown. I suggest that the supposed m2 alveolus is this cavity formed behind the exposed portion of the m1 root.
- The upper dentition of P. marshi does not differ appreciably from that of P. intrepidus. The best preserved specimen is F:AM 27453, from the late Barstovian Cerro Conejo Member of New Mexico (figs. 52–54). This skull has only three pairs of upper premolars. The Frick-AMNH collection has five specimens of P. marshi with upper dentitions. F:AM 27453 is the only specimen not having evidence of four upper premolars. I think that the most anterior premolar present in F:AM 27453 is P2. The crushed skull was reconstructed by Frick Laboratory preparators who located this P2 anterior to a point midway between C and P3. The suspected P2 is long, peglike and single-rooted in F:AM 27453. P3 is large, with a primary cusp that is similar in size to the paracone of P4. The width of P3 is greater in the posterior half of the tooth. P4 is similar to that of P. intrepidus. There is a prominent protocone that projects anterolingually. Anteriorly, at the base of the paracone of P4, a distinct parastyle is present, forming a deep secondary carnassial notch. On the anterolateral surface of the parastyle, a small accessory cusp is present. All of this P4 morphology resembles other species of North American Pseudaelurus. M1 is compressed anteroposteriorly. M1 of P. marshi is nonvestigial. All North American specimens of Pseudaelurus studied have a functional, occluding, nonvestigial M1. In modern felids, however, M1 is vestigial. The upper component of the carnassial apparatus includes P3 and P4 in extant felids, but does not involve M1.
- F:AM 27453 provides well-preserved information about the skull of P. marshi (figs. 52–55). However, the dorsum of the cranium has been crushed, thus losing information on the sagittal and nuchal crests. The basicranium is better preserved. The left auditory bulla was prepared (fig. 54). Anteriorly, the septum bullae can be seen at the anterior margin of the petrosal, forming the lateral wall of the most anterior portion of the caudal entotympanic chamber. Posterolaterally, a sliver of the septum bullae can be seen arching toward the petrosal promontorium. This morphology of the septum bullae and its relationship to the petrosal promontorium agrees with that of P. validus (Hunt, 1998; Rothwell, 2001). However, the caudal entotympanic of the P. marshi skull has expanded more anteriorly when compared to the P. validus skull. The anterior expansion of the caudal entotympanic of P. marshi has reached the level of the most anterior margin of the ectotympanic chamber. The caudal entotympanic chamber terminates only slightly posterior to the anteromedial process of the auditory bulla. The caudal entotympanic has invaded, emarginated, and thinned out the ectotympanic, where it articulates with the basioccipital and basisphenoid. This differs from the much thicker, less invaded ectotympanic attachment seen in P. validus. The most anterior point of the P. validus caudal entotympanic is slightly posterior to the anterior apex of the ectotympanic chamber. This degree of anterior expansion in the P. marshi auditory region approaches the level seen in modern felids. On the medial surface of the petrosal, a medial extension or process of the promontorium can be seen. It rests upon the edge of the basioccipital. This process is smaller than the one described in a skull assigned to P. validus (Hunt, 1998). Possible correlation of depth of an expanding caudal entotympanic with disappearance of the medial process of the petrosal promontorium in modern felids has been suggested (Hunt, 1998).
- The close relationships of the bullae of F:AM 27453 with the mastoid and paroccipital processes are similar to those described in the P. validus skeleton from the Nambé Member of the Tesuque Formation (Rothwell, 2001). Medial to each bulla, the ridge formed by the expanded caudal entotympanic indents the basioccipital. Posteromedial to each bulla, the hypoglossal foramen is visible within the same depression as the posterior lacerate foramen (figs. 54, 55). In F:AM 27453, the hypoglossal foramen is at the posteromedial border of the depression that it shares with the posterior lacerate foramen. Because of its position on the rim of a depression, the hypoglossal foramen does not open in a ventral direction as in Proailurus lemanensis (fig. 29). The hypoglossal canal in P. marshi has shifted toward the horizontal, opening in an anteroventral direction, similar to modern felids. The alisphenoid canal is present on both sides of the P. marshi skull. However, crushing of this specimen prevents documentation of the presence of a foramen rotundum.
- Postcranial information on P. marshi is provided by F:AM 62144, a partial skeleton from the late Barstovian Cerro Coñejo Formation (table 2). The limb elements do not differ from those previously referred to P. validus and P. intrepidus. Unfortunately, F:AM 62144 does not include any metacarpal bones. This hinders comparison of the front limb elements of P. marshi with Proailurus lemanensis, Pseudaelurus validus, Pseudaelurus intrepidus, and modern felids (Rothwell, 2001).
- Discussion: P. marshi is the most abundant Miocene felid in the Frick-AMNH collection. I have studied 80 Pseudaelurus lower jaws that I have been able to assign to one of six North American species. Twenty-eight specimens, or 35%, are referred to P. marshi. Twenty-two are assigned to the similar-sized and temporally equivalent species P. intrepidus. Specimens of P. marshi are found in virtually every felid-producing locality in the early and late Barstovian of North America. P. marshi and P. intrepidus account for 75% of the felid lower jaws from North American Barstovian localities. Pseudaelurus marshi, similar in size to P. intrepidus, differs primarily in the c–p3 length and the height of the dentary.
- The possibility that these two fossil taxa are sexually dimorphic members of the same species must be considered. One definition of sexual dimorphism is “when the means for fully developed males and females differ in a statistically significant way. The dimorphism is partial when the standard ranges of males and females overlap, and complete when they do not” (Kurtén, 1955: 7). One hypothesis is that lower jaw specimens assigned to P. marshi, based primarily on the character of short c–p3 length and dentary height, are female members of P. intrepidus. To test this hypothesis, I studied modern felids. I examined modern skulls of four felid species in the Department of Mammology at the American Museum. Skeletons of Lynx canadensis, Lynx rufus, Felis concolor, and Panthera leo, killed in the wild and labeled as either male or female, were examined, measured, and scored for 40 dental and cranial characters (table 6). The limited number of skeletons labeled as to sex did not make it possible to select specimens in a random manner. To facilitate comparison of c–p3 length in different-sized felids, I calculated the mean of a c–p3 index for extinct and modern felids (table 4). To compute the c–p3 index, I divided the c–p3 length by the m1 length for each specimen studied (table 5). The length of the lower carnassial tooth has been demonstrated to be a good proxy for body size in felids (Legendre and Roth, 1988).
- Panthera leo and Lynx canadensis displayed sexual dimorphism with respect to the c–p3 length; Felis concolor and Lynx rufus did not (table 3). I then grouped P. intrepidus and P. marshi into one hypothetical extinct species. I treated the data from these two taxa as partitions of the same species. The P. marshi and P. intrepidus data present as either two separate species or as sexually dimorphic members of the same species (table 3). In other words, the data of P. intrepidus and P. marshi present as either male and female felids whose c–p3 length resembles somewhat the lion or the lynx, or as two similar-sized but separate species which have the c–p3 length form of the mountain lion or bobcat.
- To further compare P. intrepidus and P. marshi with modern felids, I plotted the dentary height versus m1 length (fig. 56). The height of the dentary below the carnassial tooth differs significantly (p = 0.0004) in P. intrepidus and P. marshi. Again, the length of m1 was used as an analog for body size. These data can be compared to the same information from modern specimens of F. concolor killed in the wild (fig. 57). The male and female F. concolor data resemble the P. intrepidus and P. marshi chart. Data from figures 56 and 57 are combined in figure 58. Felis concolor does display sexual dimorphism with respect to height of the dentary (p = 0.0475). This felid does not display sexual dimorphism in the c–p3 length (p = 0.28).
- In summary, there are arguments for and against sexual dimorphism being the explanation for character differences between P. intrepidus and P. marshi. Supporting arguments include: (1) Sexual dimorphism is seen in modern felid species, at the very least in body size and skull length in small felids (Dayan and Simberloff, 1996). (2) P. skinneri and P. stouti display differences in c–p3 length that could also be interpreted as sexual dimorphism. (3) P. intrepidus and P. marshi are size and temporally equivalent. Specimens of the two species are sometimes found in the same localities. Counter arguments include: (1) A similar range in c–p3 length and dentary height and width is not seen in P. validus. P. validus and some modern species do not exhibit sexual dimorphism in the lower jaw. (2) Modern assemblages of felids sometimes contain at least two species that are indistinguishable in jaw length (Kiltie, 1988). (3) The p error for the hypothetical P. intrepidus–P. marshi species (0.0001) is far outside the range of p error seen in the four modern species studied (0.28–0.008).
- The results appear inconclusive, primarily because of the variability of the sexual dimorphism displayed by different species of living felids. However, if P. intrepidus and P. marshi were indeed sexually dimorphic members of the same species, the males and females differed far more than any of the four living felids. For this reason, I choose to consider these two samples as separate species.
- Pseudaelurus aeluroides Macdonald, 1954
- Holotype: SDSM 3248, right ramus with c, p3, p4 and m1 from northeast rim of Sinclair Draw (early Barstovian), Sioux Co., Nebraska.
- Referred Specimens: None.
- Distribution: Type locality only.
- Description and Comparisons: I have not been able to examine either this specimen or a cast of this taxon. From the illustration provided by Macdonald (1954), it may be a juvenile with erupting teeth. The m1 is 15.6 mm long and the distance between the lower canine and p3 is 7.3 mm. I have examined 21 lower jaws referred to Pseudaelurus from the Lower Snake Creek Fauna. I have assigned seven of these specimens to P. marshi Thorpe (1922). None of the characters or dimensions mentioned by Macdonald would distinguish SDSM 3248 from this group of fossils. I hesitate to reassign a specimen without seeing it, but Pseudaelurus aeluroides (SDSM 3248) may be synonymous with P. marshi.
- CHARACTER ANALYSIS
- Dentition
- Mandible
- Basicranium
- Postcranium
- PHYLOGENY
- BIOGEOGRAPHY
- DISCUSSION
-
FIGURES & TABLES -
REFERENCES -
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TOM ROTHWELL "Phylogenetic Systematics of North American Pseudaelurus (Carnivora: Felidae)," American Museum Novitates, 2003(3403), 1-64, (22 May 2003)
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