An exceptionally well-preserved white shark fossil (Carcharodon sp.) is described here from the early Pliocene (ca. 4 Ma) Pisco Formation of southwestern Peru. This specimen preserves 222 teeth and 45 vertebrae as well as fragmentary jaws. The teeth show characters of Carcharodon, including weak serrations and a symmetrical first anterior tooth that is the largest in the tooth row. This dentition also shows a character of Isurus with a distally inclined but mesially slanted intermediate tooth. Although the Pisco specimen demonstrates characters of both Isurus, also known form the Pisco Formation, and modern Carcharodon carcharias, it is assigned to the genus Carcharodon and referred to herein as Carcharodon sp. While Carcharodon sp. From the Pisco Formation shows numerous diagnostic characteristics shared with C. carcharias, it differs from the extant species in having a distal inclination of the intermediate tooth. The precaudal vertebral centra of the Pisco Carcharodon preserve distinctive dark and light incremental bands that, based on calibration with oxygen isotopes, indicate annular growth couplets. The fossil shark was at least 20 (±1) years old at the time of its death. Based on measurements of teeth and vertebral centra, this specimen is estimated to have had a minimum total body length of 4.80–5.07 m, similar to estimates for modern older individuals of C. carcharias. Relative to the extant Carcharodon carcharias, the Pisco Carcharodon sp. grew at a slower rate. The fossil record of lamnoid sharks preserved in the Pisco Formation demonstrates that the modern white shark is more closely related to Isurus (I. hastalis) than it is to the species Carcharodon megalodon, and the latter is therefore best allocated to the genus Carcharocles.

A bizarre “spine-brush complex” is found only in extinct symmoriiform chondrichthyans (Order Symmoriiformes). Its structural complexity makes the spine-brush complex a rich source of morphological characters for phylogenetic analysis, and it has been used as a basis for their family-level subdivision. Development of the complex is sex-linked in one of the three symmoriiform families customarily recognized (Falcatidae), but its distribution within members of the other two families (Symmoriidae, Stethacanthidae) is poorly documented. Consequently, earlier family-level diagnoses (which were largely based on the presence or absence of the spine-brush complex) are probably misleading. Some features of the spine-brush complex can be homologized with structures found in “normal” shark dorsal fins, suggesting that the spine-brush complex is a highly specialized first dorsal fin. The spine-brush complex may have arisen by co-option of the first dorsal fin module, possibly involving its suppression in females and postdisplacement (delayed development) in males, plus acquisition of several apomorphic traits, unlike in chimaeroids and actinistians where co-option of the first dorsal fin module is not sex-linked or developmentally postdisplaced. The evolutionary history of dorsal fin modularity is examined. In gnathostomes, co-option is typically confined to the first module, whereas the second is more highly conserved, retaining its functional role in aquatic locomotion.

New, undescribed material of the hybodont shark Tribodus limae, from the Lower Cretaceous of northeastern Brazil, provides new information on the pectoral endoskeleton in this taxon. This allows for a revision of its pectoral morphology, which may be broadly applicable to other Hybodontoidei. Four new specimens of Tribodus with well-preserved pectoral girdles are described, including the first complete, three-dimensionally preserved hybodont scapulocoracoid and partial pectoral fin. These specimens permit examination of the posterior surface of the scapulocoracoid, not visible in previously described hybodonts. Overall pectoral morphology of Tribodus is similar to that of other hybodontiforms and neoselachians. However, the new material shows that the pectoral articulation in Tribodus comprises an oblique posterior ridge on the scapulocoracoid, unlike previous reconstructions of pectoral anatomy in Tribodus and other hybodonts based on two-dimensionally preserved specimens. However, other elasmobranchs, including many neoselachians, Orthacanthus, and ctenacanths, also have an oblique posterior articulation, indicating that this feature may be primitive for elasmobranchs. The pectoral articulation of Tribodus differs noticeably from that of Cladoselache and similar Paleozoic chondrichthyans, which have an elongated, laterally positioned articular process, and from the outgroup (osteichthyans, acanthodians and placoderms). Tribodus also differs from the Paleozoic hybodontiform Onychoselache in which the articular region comprises a laterally positioned glenoid fossa and posterior condyle. Tribodus has an additional diazonal foramen not found in other hybodonts. Other pectoral features of Tribodus are in agreement with previous phylogenetic hypotheses, supporting the position of Tribodus within Hybodontoidei.

The monospecific genera Eothyris (Petrolia Formation, Leonardian, Archer County, Texas) and Oedaleops (Abo/Cutler Formation, Wolfcampian, Rio Arriba County, New Mexico), known solely from cranial remains, are confidently assigned to the monophyletic Caseasauria based on cranial and dental characters. In addition, Eothyris and Oedaleops comprise the monophyletic Eothyrididae based on nine cranial and dental characters. In contrast to the medium to large sized herbivorous caseids, the small eothyridids exhibit dental features that indicate that they were faunivores. The presence of well-developed caniniform teeth suggests that they were predators. Both Eothyris parkeyi Romer and Oedaleops campi Langsten exhibit a suite of plesiomorphic cranial characters that identify them as basal synapsids. Thus, the eothyridids are better representatives of the primitive synapsid cranial morphotype than the oftenused ophiacodontids. Although they appear relatively late in synapsid evolution, both eothyridids are significantly older than all other caseasaurs, forcing the establishment of a long unrecorded lineage for caseids.

Recent field work in the Bighorn Basin, Wyoming has recovered significant new material of the plesiosaur Tatenectes laramiensis. The majority of cryptocleidoid plesiosaurs have been recovered from Middle and Upper Jurassic units (Oxford and Kimmeridge Clays, respectively) in the United Kingdom, but Tatenectes laramiensis is one of at least two cryptocleidoids known from the Upper Sundance Member of the Sundance Formation (Oxfordian) of North America. Although poorly known, they bear directly on both the phylogeny and biogeography of the cryptocleidoid plesiosaurs. Here we describe new fossil material of Tatenectes, and reevaluate the phylogenetic position of this genus based on all known material. New material includes a partial skeleton comprising cranial elements, axial column, and a partial pectoral girdle, as well as an isolated humerus and vertebrae. The pectoral girdle closely resembles that of Muraenosaurus belodis from the Oxford Clay, but is even shorter anteriorly. The cervical vertebrae are more compressed antero-posteriorly than in other Jurassic cryptocleidoids. The humerus is less derived, resembling that of Tricleidus seeleyi. Two most parsimonious trees were obtained, and the consensus tree solidifies the phylogenetic position of Tatenectes as being most closely related to the Oxford Clay taxon Kimmerosaurus.

A detailed redescription of the Late Triassic archosauromorph reptile Doswellia kaltenbachi Weems, 1980 from the Poor Farm Member of the Falling Creek Formation in the Taylorsville basin (Newark Supergroup) in Virginia is presented based upon additional preparation of the holotype. The euryapsid skull has a distinctive occiput with a prominent supraoccipital process that is flanked by posterior “horn-like” projections of the squamosals. Postfrontals, tabulars, and postparietals are absent. Plesiomorphic features of the palate and braincase include a plate-like horizontal parabasisphenoid, a pair of foramina for the internal carotid arteries on the ventral surface of the basisphenoid, and two fields of teeth on the palatal surface of the pterygoid. A sharp angle along the cervical and anterior dorsal ribs clearly separates the dorsal and lateral sides of the neck and anterior thoracic region. The posterior thoracic region has shorter ribs that project laterally with only a slight curvature. The ilium has a laterally deflected blade with numerous deep grooves along its distal edge. The laterally extensive set of osteoderms includes a nuchal element that is composed of several interlocking osteoderms that lack the arrangement in distinct transverse rows that characterizes the remainder of the osteoderms. A phylogenetic analysis of basal archosauriforms incorporates new data of Doswellia and the taxa Turfanosuchus, Yonghesuchus, and Qianosuchus that have not previously been combined in a single study. Results include a sister-group relationship between Doswellia and proterochampsids, placement of Qianosuchus as a crurotarsan archosaur, and Yonghesuchus and Turfanosuchus as successive sister taxa to Archosauria.

A tetrapod-based biochronologic framework for the terrestrial Triassic, which subdivides the Triassic into eight ‘Land Vertebrate Faunachrons’ (LVFs), has been proposed and developed by Lucas and coworkers. In a recent article, these authors reiterated their support for this scheme and used this opportunity to respond to criticisms dealing with the validity and utility of Triassic LVFs. This article is a reply to Lucas and colleagues and demonstrates that many aspects of this Triassic biochronology are dependent on: (1) subjective opinions regarding the taxonomic assignments of key specimens; and (2) unjustified extrapolation of correlations on the basis of geographically restricted endemics. Furthermore, it is suggested that the methodological basis for recognizing the onset of a particular LVF, the identification of the ‘first appearance datum’ for those taxa deemed to be biochronologically significant, leads to imprecision in correlation and potential ambiguity in dating. Finally, it is argued that geographic information systems are ideal tools for testing biostratigraphic hypotheses.

Several Teleosaurus skulls were described during the nineteenth century. Unfortunately, all skulls from this genus were destroyed during World War II. The only available skull is currently preserved in the MNHN. Thanks to a new preparation, new anatomical features can be seen, such as the morphology of the nasal cavity, the external otic recess, and the distribution of the foramina for the cranial nerves. A phylogenetic analysis is presented, including 14 thalattosuchian taxa. This analysis has generated four equally most parsimonious trees, where the thalattosuchians are closely related to the pholidosaurids and dyrosaurids, forming a longirostrine taxa. These relationships have been often considered to be based on homoplasies, related to the longirostrine morphology. This is also suggested herein, as the deletion of the longirostrine dependant characters or of the most longirostrine thalattosuchians in the analysis provide a consensus tree where thalattosuchians are basal crocodyliforms, a result more generally accepted. As the deletion of the most longirostrine thalattosuchians precludes the longirostrine problem in the phylogenetic analysis of Crocodyliformes, this deletion seems to be the less unsatisfactory solution to assess the crocodyliform relationships. The phylogenetic analysis also provides interesting information on the thalattosuchian relationships: Teleosaurus is the basal-most thalattosuchian, Teleosauridae is paraphyletic and Pelagosaurus is neither the basal-most thalattosuchian nor the basal-most metriorhynchid. The metriorhynchid relationships support previous works, as ‘Teleidosaurus’ is paraphyletic and the basal-most metriorhynchid, Metriorhynchus is more closely related to other metriorhynchid than ‘Teleidosaurus,’ and Enaliosuchus, for which the relationships are tested for the first time, is the sister taxon of Dakosaurus. Geosaurus is the sister taxon of the clade Dakosaurus Enaliosuchus.

Batrachotomus kupferzellensis is an upper Middle Triassic (Late Ladinian) rauisuchian archosaur. The postcranial skeleton of this species is well-represented by fossil material, including the holotype, from the localities of Kupferzell, Crailsheim and Vellberg-Eschenau in southern Germany, and is described here in detail for the first time. All postcranial elements are known except the interclavicle and parts of the carpus, manus, tarsus, pes and some osteoderm and axial elements. B. kupferzellensis is now one of the best-known rauisuchians and will be important in advancing understanding of the group's biology. A period of new anatomical and taxonomic work since 2000 has improved understanding of rauisuchians. Renewed effort in rauisuchian phylogenetics will benefit from these new data, but will also require a careful and detailed approach to character formulation.

Stegosaurus has unique plate- and spike-shaped osteoderms. Previous studies have focused on the function of the osteoderms; however, ontogenetic development and maturity of these osteoderms with respect to Stegosaurus body growth are little known. In this study, the bone growth of both the skeleton and osteoderms was assessed using thin sections from small to large-sized individuals. In the small individual, the bone histology shows a fibro-lamellar tissue with a radial and/or reticular vascular network in both a body element and an osteoderm. In the medium-sized individual, the cortex shows a longitudinal vascular network and a few lines of arrested growth (LAG) in the skeleton, whereas the osteoderms still retain fibro-lamellar bone and show a reticular vascular network without LAGs. In large individuals, both body elements and osteoderms have fibro-lamellar tissue and multiple LAGs. However, bone tissues from body elements possess external fundamental systems (EFS) at their periphery, whereas osteoderms from the large individual lack EFS. Four histological stages are observed in both the skeleton and the osteoderms in the growth series of Stegosaurus sections: (1) a fibro-lamellar tissue with a radial and/or reticular vascular network, (2) fibro-lamellar tissue with a longitudinal vascular network, (3) with LAGs, and (4) with EFS. The timing of histological changes of osteoderms was delayed from those of the skeleton. This delay indicates that osteoderms might have maintained faster growth rates than the body elements after the maturity of the skeleton.

Distinct textures have been observed on the surface of the parietals and squamosals of centrosaurine dinosaurs. It is widely held that they exhibit an ontogenetic succession and can be used as an index of progressive agerelated changes. To date, the pattern of texture expression across the parietals and squamosals has not been traced. The pattern of transition from long-grained to subsequent textures on centrosaurine parietals is investigated by mapping their distribution on a size series hypothesized to represent an ontogenetic series. These data reveal a distinct and conservative pattern of texture occurrence and transition across all examined centrosaurine taxa. Small (putatively juvenile) specimens exhibit striated or long-grained texture, whereas the largest elements (presumed adult) demonstrate the complete absence of this texture. The transition from exclusively long-grained to total absence of long-grained texture is characterized by surficial changes in two regions: (1) the long-grained texture regresses along a front situated lateral and posterior to the parietal fenestrae, and (2) an anterior to posterior series of point source ‘islands’ forms along the dorsal midline of the parietal, associated with the midline undulations. Our findings are consistent with the interpretation that the surface texture change is associated with growth and aging, and have implications for the taxonomy of both immature individuals and small-bodied taxa. Investigation of texture transitions subsequent to the long-grained to mottled transition (the mottled to adult transition) await the assembly of suitable series of nearly full grown conspecific individuals and cannot be reliably assessed employing the methodology used herein.

Prosauropods are basal sauropodomorphs that were the major terrestrial faunal components from the Norian until their extinction during the Toarcian. Their status as a natural group is debatable. In the present work I describe Adeopapposaurus mognai, a new sauropodomorph from the Cañón del Colorado Formation, in northwestern Argentina. Diagnostic autapomorphies and combination of characters of Adeopapposaurus include a series of large foramina in a sub-vertical row on the lateral surface of the premaxilla; strongly rugose depression bordered by a protuberance with a series of foramina in a sub-vertical row, on the lateral surface of the anterior end of the dentary; eleven anteroposteriorly elongated cervical vertebrae and thirteen dorsal vertebrae with neural arches taller than the respective centra. Phylogenetically Adeopapposaurus is resolved as the sister group to Massospondylus; differing from the latter based on differences in mandible and premaxilla and addition of one dorsal vertebra to the neck. The specimens described here reveal numerous herbivorous adaptations, including the presence of a highly vascularized bony plate in the premaxilla and dentary, which indicates that it had a horny beak.

Titanosaurs are the only sauropods that possessed osteoderms, although the phylogenetic distribution of this feature within Titanosauria is not yet resolved. Whereas the majority of titanosaur osteoderms are from South America, several have been found in Cretaceous rocks in Africa, Madagascar, and Europe. Here we describe a titanosaur osteoderm from the Maastrichtian of India that extends the geographic range of these armored sauropods. The known spatiotemporal distribution of titanosaurs is broader than the distribution of titanosaur osteoderms. This discrepancy can be explained by one or more of several factors: (1) few titanosaur genera had osteoderms; (2) titanosaurs were not heavily armored; (3) there are strong collection and/or (4) taphonomic biases against these elements. Almost 90 individual titanosaur osteoderms have been reported and can be assigned to ten of the 40 currently recognized titanosaur genera. Although they are not divisible into discrete size classes, titanosaur osteoderms are here shown to fall into four morphotypes: “ellipsoid,” “keeled,” “cylindrical,” and “mosaic.” No morphotype is unique to any one taxonomic group, geographic area, or time period. Despite the relative scarcity of osteoderms, it appears that armored titanosaurs are relatively diminutive in body size, with average femoral and humeral lengths of about 60 and 70% those of unarmored taxa, respectively. An apparent exception to this relationship is the titanosaur osteoderm from India, which likely pertains to one of the two relatively large-bodied titanosaur species that are known from the Lameta Formation.

Two partial theropod braincases recovered from the Upper Cretaceous Prince Creek Formation confirm the presence of Troodon formosus in Alaska. Characters that distinguish one specimen as Troodon formosus include; a very strongly developed sagittal crest on fused parietals, details of pneumatic spaces within the skull bones, and the size and location of the nervous and venous foramina. The second specimen has the distinct lateral depression diagnostic of a troodontid braincase. The recovery of these specimens, coupled with the absence of non-dental material from other small theropod taxa in these deposits, is significant. It corroborates the conclusion based on dental remains that T. formosus was the most abundant theropod in northern Alaska, thus supporting the model of the adaptability of this taxon to the highly seasonal, low-light conditions that existed in the region during the Late Cretaceous.

A new species of enantiornithine bird from the Lower Cretaceous Yixian Formation of northeastern China is reported. The new taxon, Shanweiniao cooperorum, possesses several enantiornithine synapomorphies as well as the elongate rostral morphology (rostrum equal to or exceeding 60% the total length of the skull) of the Chinese early Cretaceous enantiornithines, Longipteryx chaoyangensis and Longirostravis hani. The discovery of this new specimen highlights the existence of a diverse clade of trophically specialized enantiornithines, Longipterygidae, for which we present phylogenetic support in a new comprehensive cladistic analysis of Mesozoic birds. Shanweiniao provides new information on the anatomy of longipterygids, and preserves a rectricial morphology previously unknown to enantiornithines, with at least four tail feathers closely arranged. This supports the hypothesis that enantiornithines were strong fliers and adds to the diversity of known tail morphologies of these Cretaceous birds.

The magpie goose Anseranas semipalmata (Aves: Anseranatidae), the sole modern representative of the family, is endemic to Australia. The fossil record of Anseranatidae in Australia was until now restricted to Pliocene and younger sediments. Here we describe an anseranatid from the Oligo-Miocene Carl Creek Limestone in the Riversleigh World Heritage Property, Boodjamulla (Lawn Hill) National Park, in northwestern Queensland, as a new species and genus, based on a coracoid and two scapulae. These fossils extend the known age of the Anseranatidae lineage in Australia to about 25 million years ago. The fossil distribution of Anseranatidae now includes the Paleocene in North America, Eocene and Late Oligocene of Europe, and the Late Oligocene to earliest Miocene in Australia, indicating a globally widespread distribution of the family during the early-mid Tertiary.

Lophiodon is the best-known member of the Lophiodontidae, a family of Eocene Eurasian perissodactyls, in terms of its skull and postcranial skeleton. Previous studies have allied Lophiodontidae with either Tapiroidea or Chalicotherioidea. This study describes the cranial and postcranial osteology of Lophiodon with an emphasis on characters pertaining to the phylogenetic position of lophiodontids. Although cranial and postcranial remains of Lophiodon are known from European faunas, the skull and postcranial skeleton have not been well studied, and few non-dental characters have been used to investigate the relationships of this genus to other perissodactyls. Lophiodon displays a mosaic of cranial and postcranial features that could be interpreted as possible synapomorphies uniting it with either tapiroids or chalicotherioids. Data collected from these studies were incorporated into a phylogenetic analysis of a variety of perissodactyl taxa scored for characters of the skull, postcranial skeleton, and dentition. These data indicate that lophiodontids, as represented by Lophiodon, are the sister-taxon to Ceratomorpha (Tapiroidea plus Rhinocerotoidea). Chalicotherioids are paraphyletic and placed in a clade with palaeotheriids and brontotheres, a result that may be due to superficial similarities of the dentition. Thus, lophiodontids still belong in the Tapiromorpha, but cranial and postcranial evidence does not support a special relationship with either tapiroids or chalicotherioids. Unlike previous studies, the results also do not support a monophyletic Equoidea (Palaeotheriidae plus Equidae).

A new assemblage of ruminants from Paali in the lower Chitarwata Formation, Bugti Hills, Balochistan, central Pakistan, includes two lophiomerycids, Lophiomeryx, and Nalameryx gen. nov., allowing revision of ruminants previously reported from the Oligocene of the Indian Subcontinent. Two species are referred to Nalameryx: N. savagei (formerly Iberomeryx savagei), and N. sulaimani nov. sp. The middle Oligocene age previously assigned to the lower unit of the Chitarwata Formation in the Bugti area, mostly based on the rodent fauna from Paali, is supported by the composition of the ruminant fauna, which consists of taxa exclusively known in the Oligocene of Eurasia. The new ruminant fauna from Paali is clearly distinct from the early Miocene assemblages known in the Bugti hills, and suggests the existence of densely forested habitat probably mixed with more open areas in central Pakistan during the middle Oligocene.

A new fossiliferous locality is reported from southwestern France (Moissac III) that yielded two skulls referred to the anthracotheriid Elomeryx crispus and the rhinocerotid Protaceratherium albigense, and an isolated rodent tooth. The anthracotheriid skull indicates a close relationship with E. borbonicus based on its cranial morphology. The rhinocerotid skull improves our knowledge concerning its anterior dentition, cranial morphology and proportions, and enables a more precise specific diagnosis. We suggest an early late Oligocene biochronological age (Mammal Paleogene European reference level MP25–26) for Moissac III, which is substantiated by the co-occurrence of P. albigense and of the theridomyid rodent Issiodoromys cf. paufflensis. The European stratigraphic range of E. crispus, so far restricted to the late Eocene-early Oligocene interval (MP18-MP22), extends up to the MP25–26, which in turn supports an origination of ‘Miocene bothriodontines’ from a European ancestor.

In the late Oligocene and early Miocene of North America, beavers (Castoridae) diversified into two lineages of burrowing specialists, the Palaeocastorinae and Migmacastorinae. Although common in the fossil record, artefactual evidence of burrowing beaver habits is rare and thus the ecology of most species is unknown. Living fossorial rodents display three distinct digging modes: scratch, chisel-tooth, and head-lift digging. We used a geometric morphometric approach to examine how digging behaviors are reflected in the craniodental shape of a broad sample of extant rodents, and then used the results to infer the digging modes of 18 extinct beaver species. Ecomorphological analyses revealed differences in skull shape related to digging habits, which can be used to discriminate the digging modes of extant rodents. Extant rodents with similar digging habits show convergent morphology, suggesting this method could be applied to extinct rodents, regardless of ancestry, to accurately infer their locomotor ecologies. The Oligocene to Miocene radiation of burrowing beavers included specialized chisel-tooth and head-lift digging species, which likely filled similar roles to living fossorial and subterranean species. Climate changes toward cooler, drier, and more open habitats correspond with the diversification of burrowing beavers. The subsequent radiation of other fossorially adapted rodent species likely led to competition with, and the extinction of, burrowing beavers.