Vintana sertichi is a sudamericid gondwanatherian mammal known only from the Upper Cretaceous (Maastrichtian) Maevarano Formation in the Mahajanga Basin of northwestern Madagascar. It is based on a single specimen, a well-preserved and virtually complete cranium discovered in 2010 near Lac Kinkony. The cranium is superficially bizarre and constitutes the only cranial remains of the poorly known, phylogenetically enigmatic Gondwanatheria, which are otherwise known only from isolated teeth and fragmentary dentaries. Gondwanatheria are represented by seven other monotypic genera assigned to two families (Ferugliotheriidae and Sudamericidae). Historically, this clade was assigned to Xenarthra, Paratheria (as a sister group to Xenarthra), Multituberculata, Allotheria (as a sister group to Multituberculata), Mammalia incertae sedis, and, most recently, back to Multituberculata or a close relative of Multituberculata. The craniodental evidence provided by Vintana supports inclusion in Sudamericidae, the monophyly of Gondwanatheria, and the position of Gondwanatheria as nested within or sister to Multituberculata. In addition to briefly reviewing the taxonomic composition and phylogenetic history of Gondwanatheria, this introductory chapter sets the stage for the other chapters in the volume by (1) briefly summarizing the inferred life habits of gondwanatherians; (2) reviewing the systematic paleontology of V. sertichi; and (3) providing overviews of the discovery of the holotypic specimen, its preservation, its preparation, and the imaging and measurement techniques used to study it. The chapter closes with an overview of the geological context of V. sertichi, which indicates that the species lived in a coastal floodplain environment and in a highly seasonal, semiarid climate.

The Gondwanatheria are an enigmatic clade of Cretaceous and Paleogene mammals known from South America, Africa, Madagascar, India, and the Antarctic Peninsula. The eight valid species—each belonging to a monotypic genus and the first of which was described only 30 years ago—are represented almost exclusively by isolated teeth, in addition to fragmentary dentaries attributed to Sudamerica, Gondwanatherium, Ferugliotherium, and an unnamed taxon from Tanzania. No cranial (skull exclusive of lower jaw) or postcranial material has heretofore been assigned to the Gondwanatheria, a severe limitation that has precluded a comprehensive assessment of phylogenetic affinities. Here we describe, in detail, the first cranial specimen of a gondwanatherian mammal. This material consists of a complete and wellpreserved cranium of the sudamericid Vintana sertichi, recovered from the Upper Cretaceous (Maastrichtian) Maevarano Formation in the Mahajanga Basin of northwestern Madagascar. Salient features of the cranium include elongate, scimitarlike jugal flanges, huge orbits, strong klinorhynchy, and a vaulted nuchal region. Micro-computed tomography greatly facilitated the delineation of sutures and the description of internal morphology. The cranial features of Vintana are compared with those of a broad range of synapsids, with particular concentration on other Mesozoic mammaliaforms. The cranium of Vintana exhibits a mosaic of extremely primitive and extremely derived features. It is the second largest known for a Mesozoic mammaliaform, superseded only by that of the eutriconodontan Repenomamus giganticus from the Early Cretaceous of China. Vintana is the largest known Late Cretaceous mammaliaform; it is also the largest known Mesozoic mammaliaform from Gondwana.

We present the first digital reconstruction of the endocranial cavity and endosseous labyrinth of the Late Cretaceous gondwanatherian mammal Vintana sertichi from the Maevarano Formation of Madagascar. The Malagasy specimen is exceptionally well preserved and represents the only described cranium known for Gondwanatheria, an enigmatic clade from the Late Cretaceous and Paleogene of Gondwana. The endocranial cast of Vintana is relatively small for an animal of its estimated body mass. Its encephalization quotient is 0.28–0.56 for a range of body mass estimates, which is similar to that of basal mammaliaforms. The olfactory bulbs are very large, occupying over 14% of the endocranial volume. The cerebral hemispheres are only slightly expanded, more similar to the condition in Morganucodon than to that in multituberculates and monotremes. Unlike the condition in other Mesozoic mammaliaforms, the endocast is greatly flexed at the circular fissure. The osseous labyrinth displays a mixture of derived and primitive features. The cochlear canal is only slightly curved and short compared with that of extant therians. The ratio between total cochlear canal length and maximum cranial length is smaller than in basal mammaliaforms and approximates that of non-mammaliaform cynodonts. By contrast, the presence of both primary and secondary osseous laminae, the tractus foraminosus, and Rosenthal's canal represent derived characteristics of the mammalian inner ear typical of cladotherians. A modern innervation of the cochlea has either evolved independently in Vintana and cladotherians or was already present in the last common ancestor of both clades.

The cranium of Vintana sertichi preserves the first associated upper dentition of a gondwanatherian mammal. Gondwanatherians are known almost exclusively from isolated teeth, particularly molariforms. As such, referral of V. sertichi to the Gondwanatheria, differentiation of V. sertichi from other gondwanatherians, and determination of the relationships of V. sertichi to other gondwanatherians must rely heavily on dental morphology. The hypsodont nature, gross morphology, enamel microstructure, and wear pattern of its molariform teeth serve to unequivocally identify the cranium of V. sertichi as that of a sudamericid gondwanatherian. Based on available morphology, V. sertichi appears to have had an upper dental formula of 2.0.1.4. There are two long, curved alveoli in each premaxilla for enlarged, buccolingually compressed, procumbent incisors that were well separated from the cheek teeth by a long diastema. There is no evidence of a canine. The single premolariform tooth appears to have been small and two-rooted, but neither the left nor the right crowns are preserved. Of the eight upper molariform alveoli, four are preserved with teeth in situ, three in the left maxilla (antepenultimate, penultimate, and ultimate) and one in the right (penultimate). The molariform cheek teeth have several salient characteristics: large size, hypsodont crowns, roughly quadrangular outlines, occlusal surfaces worn essentially flat, numerous cementum-filled infundibula, cementum-filled furrows that invaginate from the buccal side but do not extend to the base of the crown, and multiple, short root apices. The relative amounts of wear on the molariform cheek teeth of V. sertichi indicate a mesial-to-distal eruption sequence.

The enamel microstructure of the molariform cheek teeth of Vintana sertichi (Gondwanatheria, Mammalia) from the Late Cretaceous of Madagascar retains many of the plesiomorphic characteristics of mammalian prismatic enamel (e.g., single-layered schmelzmuster; non-decussating, small prisms). However, V. sertichi exhibits a relatively derived condition and resembles Lavanify miolaka (Late Cretaceous, Madagascar), Bharattherium bonapartei (Late Cretaceous, India), and an indeterminate sudamericid (Late Cretaceous, Madagascar) in possessing modified radial enamel, consisting of prisms separated by prominent interrow sheets of interprismatic matrix. A second group of gondwanatherians (Ferugliotherium windhauseni, Gondwanatherium patagonicum, Sudamerica ameghinoi, Greniodon sylvaticus), all from the Late Cretaceous and Paleogene of Argentina, retains relatively primitive, ‘normal’ radial enamel, in which the interprismatic matrix anastomoses around the prisms and does not form interrow sheets. The prisms of gondwanatherian molariforms generally become wider from the enamel-dentine junction to the outer enamel surface, dramatically so in Gondwanatherium. Seams are very rare; tubules are more common. Prism decussation has not been found in any gondwanatherian enamel. Gondwanatherian molariforms lack or have only a thin layer of external prismless enamel, although it is thick in the incisors of Sudamerica. Despite their apparent utility in differentiating among gondwanatherian taxa, or gondwanatherians as a whole from other clades, many of the derived characteristics of gondwanatherian enamel microstructure are found in other mammalian groups and may reflect a high degree of homoplasy.

The nearly complete and well-preserved cranium of Vintana sertichi provides an opportunity to investigate its dietary adaptations. We used a combination of comparative morphological and biomechanical analyses to reveal the direction of its power stroke during mastication, reconstruct the positions and relative sizes of its muscles of mastication, and predict its capacity to produce bite forces during incision and molariform occlusion. The orientation of dental wear striations on the upper molariform teeth of Vintana, in combination with the orientation of the enamel islets and synclines and the position of leading and trailing edges, demonstrates that the power stroke was primarily palinal (distally directed), with a significant buccally directed component that is absent in multituberculates, haramiyidans, and other gondwanatherians. The large palinal component of jaw movement was corroborated by biomechanical analyses of the moments generated by the primary jaw adductors around the dentary-squamosal joint axis. Similar analyses also confirmed the previously documented proal (mesially directed) power stroke of the extant rodent Myocastor. Finite element analyses predict that Vintana was capable of producing bite forces that were more than twice as high as the similarly sized Myocastor. Vintana was almost certainly an herbivore, as claimed previously for other sudamericid gondwanatherians. Its size and capacity to generate high bite forces at both the incisors and the molariform teeth suggest that it was a mixed feeder whose diet may have included relatively large, hard food items such as roots, seeds, twigs, or nut-like fruits.

Living mammals are distinguished from other extant tetrapods by adaptations for improved senses of hearing, touch, and smell. These adaptations, and concomitant reductions in visual anatomy, evolved during the Mesozoic in the mammalian and therian stem lineages. Here, we present a comparative study of the sensory anatomy of the Late Cretaceous gondwanatherian mammaliaform Vintana sertichi in order to draw inferences regarding its sensory abilities and sensory ecology. Our analyses demonstrate that Vintana has relatively large orbits that may have accommodated large eyes. Vintana also possessed cochlear primary and secondary osseous laminae and a cochlear canal that was relatively longer than in non-mammaliaform cynodonts but shorter than in extant therians. These features suggest that Vintana had some capacity for high-frequency hearing (i.e., >20 kHz), but that its cochlea may have encoded a more limited range of frequencies than the cochleas of most extant therians. The semicircular canals of Vintana have large radii of curvature and are nearly orthogonal, suggesting high sensitivity to angular head accelerations. These vestibular features may have evolved in order to stabilize large eyes during rapid and/or agile locomotion. Combined with evidence for large olfactory bulbs and a large trigeminal endocast, these data reveal that Vintana possessed a unique suite of sensory adaptations that distinguish it from other Mesozoic mammaliaforms. If these inferences are correct, then Vintana was probably a large-eyed and agile species, with a keen sense of smell and better high-frequency hearing than most other Mesozoic mammaliaforms.

The skull of Erlikosaurus andrewsi from the Upper Cretaceous Baishin Tsav locality of Mongolia represents the only known three-dimensionally preserved and nearly complete skull of a therizinosaurian. Computed tomographic (CT) scanning of the original specimen and three-dimensional visualization techniques allow the cranial skeleton to be digitally prepared, disarticulated, and restored. Here, we present a detailed description of the restored skull morphology and the individual cranial elements, including visualization of the internal neurovascular and pneumatic structures. Information gained from this study is used in a revised and emended diagnosis for E. andrewsi. A reappraisal of the evolutionary and functional changes in the cranial skeleton as provided by this study supports prior proposals that a keratinous sheath or rhamphotheca was developed early in the evolution of Therizinosauria. Paralleled by the reduction of functional and replacement teeth, this development indicates a shift in the manner of food processing/procurement at the tip of the snout. Extensive pneumatization of the braincase, most evidently developed in E. andrewsi in comparison with other known therizinosaurians, appears to have led to a reduction of the adductor musculature and thus the potential bite force in derived therizinosaurians. In addition, the application of digital data, as presented in this study, introduces a novel way to document fossil data that will allow for morphological and anatomical data to be made widely accessible.

Detailed analyses of the dentition of the single preserved holomorphic specimen and isolated teeth of the extinct Late Jurassic hexanchiform shark, Notidanoides muensteri, support previous interpretations that all Jurassic cow sharks belong to the family Crassonotidae, which represents stem-group hexanchoids. The reconstruction of its dentition has enabled the identification of important congruencies (comb-like lateral teeth, presence of a lower (?) symphyseal tooth row) and differences (very weak dignathic and monognathic heterodonties, with anterior teeth being of the same general morphology as laterals). Although the general tooth morphology does not change significantly, ontogenetic trajectories are identifiable, including development of lateral cusplets in symphyseal teeth, reduction of labial tooth crown ornamentation, and more pronounced dignathic heterodonty pattern in adults. The general root morphology is identical to that of Crassodontidanus and represents the plesiomorphic condition within hexanchoids. The Jurassic hexanchoids Notidanus wagneri, N. huegeliae, N. eximius, and N. nikitiini, which are known from isolated teeth only, are synonymized with Notidanoides muensteri based on the dental analyses presented here. The distribution pattern and scarcity of fossil remains indicate that this crassonotid was a typical Tethyan element of Late Jurassic neoselachian faunas and inhabited open-marine environments, probably on the outer shelves and upper continental slopes. Notidanoides appears later in the fossil record than Crassodontidanus and survives into the early Tithonian. By the end of the Jurassic, both seemingly went extinct and were replaced by other plesiomorphic hexanchoids (e.g., Pachyhexanchus) in the Early Cretaceous.

We describe a new shark fauna from Canada's westernmost Arctic island, Banks Island, Northwest Territories, based upon thousands of shark teeth recovered from lower—middle Eocene sediments of the Cyclic Member (Eureka Sound Formation) on northern Banks Island, Northwest Territories (∼74°N latitude). Based upon palynology, the sediments preserving the shark teeth are late early to middle Eocene in age and likely span the Early Eocene Climatic Optimum (EECO). The low-diversity faunal assemblage is dominated by the sand tiger sharks Striatolamia and Carcharias, but also includes relatively rare teeth of the carcharhinid Physogaleus (extinct relative of sharpnose and tiger sharks) and very rare teeth of the odontaspidid Odontaspis winkleri. We also report the occurrence of the ray Myliobatis. Based upon analogy with extant Carcharias taurus and Myliobatis, the presence of Carcharias and Myliobatis on northern Banks Island corroborates the relatively warm sea surface temperatures estimated by others for the Eocene Arctic Ocean. We hypothesize that the low diversity of the Banks Island shark fauna, in comparison with other early Eocene brackish, shallow-marine chondrichthyan assemblages such as the Abbey Wood (U.K.) fauna, is probably due to environmental factors, including reduced salinity.

Eurysternum wagleri is one of the first named, yet most poorly understood turtles from the Late Jurassic of Europe. Over the years, many specimens have been referred to and many species synonymized with E. wagleri, but little consensus is apparent, and the taxonomy is therefore highly confusing. Based on the rare, only known illustration of the lost holotype and on the reassessment of select individuals, the species E. wagleri is recharacterized herein. Eurysternum wagleri is diagnosed by a deep pygal notch, a carapace with a pentagonal outline, a contribution of vertebral 5 to the posterior carapace margin, three cervical scales, very wide vertebral scales with a well-developed radiating pattern, well-developed costoperipheral fontanelles in medium-sized individuals, a plastron connected to the carapace by ligaments, gracile, peg-like bony projections of the hyo- and hypoplastra, and large, oval-to-quadrangular lateral plastral fontanelles. A lectotype is designated for Acichelys redenbacheri, and this taxon is interpreted as the junior subjective synonym of Eurysternum wagleri. All other, previously proposed synonymies are rejected, because they lack characters that would allow diagnosing them as E. wagleri.

A new continental turtle, Tacuarembemys kusterae, gen. et sp. nov., is described on the basis of a partial external mold of the carapace and associated shell bone fragments recovered from the Batovi Member (Late Jurassic—? earliest Cretaceous) of the Tacuarembó Formation, Paraná Basin, Uruguay. The estimated length of the carapace is 18 cm. This new genus and species shows a unique combination of characters: a large nuchal notch, a pair of anterior supernumerary scales, the absence of a cervical scale, and an external surface ornamentation that is macroscopically smooth with some thin linear ridges perpendicular to the margins of the plates and microscopically composed of small, randomly distributed pits. The first two characters resemble those seen in the solemydid Naomichelys speciosa from the Cretaceous of North America, although the ornamentation is markedly different. Although this combination of characters—some shared with other taxa (including cryptodires and pleurodires) and some others that are autapomorphic—allows the recognition of a new genus and species, additional remains are yet needed in order to clarify its phylogenetic relationships. Tacuarembemys kusterae is part of the Priohybodus arambourgi Assemblage Zone, which is of Late Jurassic—?earliest Cretaceous age. This is the first turtle to be discovered in South American continental deposits of that age and thus increases the knowledge on the regional evolution of Mesozoic turtles. The paleoenvironment for this species includes lakes and permanent and ephemeral rivers in arid-to-semiarid climatic conditions.

Ornithosuchidae is a group of Late Triassic pseudosuchian archosaurs of controversial phylogeneticaffinities. This clade currently comprises three taxa: Venaticosuchus rusconii and Riojasuchus tenuisceps, both from Argentina, and Ornithosuchus longidens, from Scotland. V. rusconii was erected on the basis of an incomplete skull with articulated lower jaws and some elements of the postcranium that are currently lost. Venaticosuchus rusconii is redescribed here and included for the first time in a phylogenetic analysis to test its affinities with ornithosuchids. The bizarre morphology of V. rusconii has a unique combination of traits that distinguishes it from the other ornithosuchids, such as basipterygoid processes directed ventrally, dentary with the dorsal margin of the anterior end dorsally expanded, articular without a foramen on its medial side, and the absence of a surangular foramen, corroborating the validity of this taxon. V. rusconii is recovered as an ornithosuchid more closely related to R. tenuisceps than to O. longidens, based on the presence of a nearly pointed anterior margin of the antorbital fenestra, and a vertical bony strut of the jugal that separates the antorbital fenestra from the infratemporal fenestra.

The presence of early pseudosuchians and avemetatarsalians in Anisian beds of Africa demonstrates that the archosaur radiation was well underway by the beginning of the Middle Triassic. The rapid radiation produced a variety of forms, but many of the unique, well-diagnosed Late Triassic clades (e.g., Aetosauria, Ornithosuchidae) lack diagnosable members from the Middle Triassic. Here, we introduce a new Middle Triassic archosaur, Nundasuchus songeaensis, gen. et sp. nov., with an unusual mix of apomorphic character states found within Pseudosuchia and just outside Archosauria. The holotype consists of partial skeleton, including representative postcranial elements and parts of the skull. We added Nundasuchus songeaensis, gen. et sp. nov., into the two most comprehensive early archosaur phylogenetic data sets available, and in both analyses the new taxon falls within Pseudosuchia. However, a number of plesiomorphic archosaurian character states (e.g., posterolaterally directed tuber of the calcaneum) optimize as local autapomorphies of the new taxon within Pseudosuchia in our analyses. Therefore, we tested alternative hypotheses of relationships for the new taxon by utilizing constraint trees. The analyses resulted in little change in the relationships and structure of other Triassic archosaur clades, but changed optimizations of certain character states and character support at the base of Pseudosuchia and Archosauria. Our analyses suggest that the complex evolution of character-state changes at the base of Archosauria is inhibiting our understanding of the relationships of early Pseudosuchia and, in turn, Archosauria.

A principal component analysis (PCA) performed for a set of 24 measurements on 33 femora and 15 measurements on 20 ilia of Silesaurus opolensis from the early Late Triassic of Krasiejów, southern Poland, shows that this sample is highly variable but probably monospecific. Most of the morphological variation is concentrated in the muscle attachments and proportions of bones, which significantly change in both size and position during ontogeny. Despite the small sample size, femora of smaller individuals have less flattened shafts and a more sinusoidal appearance. In many large specimens, proximal parts of muscle tendons are ossified at their attachment site on femora and remain attached to the bone in the largest specimens. The specimens with attached ossifications are interpreted as mature females that were statistically larger than proposed males. It is suggested that ossifications developed in females under calcitonin control. The intrapopulation variability of ilia is high, but less dependant on ontogeny. The population represented by a few specimens from the lower level at Krasiejów may represent a different stage in the evolution of the species than that from the upper horizon.

Fossil remains of at least seven individuals of a new species of Aegypius vulture from the Upper Varswater Formation at Langebaanweg, South Africa (early Pliocene), represent the earliest, unequivocal, and most substantial evidence for crown-group Aegypiinae in the world. Evaluation of available data on previously described vulture species from the Miocene of Africa and China such as Gansugyps linxiaensis, Mioaegypius gui, and Qiluornis taishanensis indicate that the corresponding fossils either lack any diagnostic characters of aegypiine vultures or are referable to the stem lineage of Aegypiinae. Aegypiine vultures, nevertheless, might be of Asian origin, and the extension of the range of this taxon into Africa south of the Sahara might be correlated with the spread of gregarious herbivores such as bovids and equids from Eurasia to Africa during the Miocene. The holotype of the new vulture species, an associated partial skeleton with elements of the pectoral girdle, the wing, and the hind limb preserved, is comparable in size to smaller individuals of A. monachus and A. tracheliotos. Evidence for an Aegypius vulture at Langebaanweg further indicates that open woodlands were an important component of the early Pliocene paleoenvironments at this particular site.

Permian tetrapod fossils were discovered in the Tanzanian Ruhuhu Formation in 1963, but they have received far less attention than the tetrapods of the overlying Usili (formerly Kawinga) Formation. Here, we describe two dicynodonts collected in the Ruhuhu Formation in 2008. Abajudon kaayai, gen. et sp. nov., is represented by a partial skull and mandible and is characterized by autapomorphic upper teeth that are triangular in cross-section, have procurved tips, and bear a deep groove on the mesial surface. Although it shows similarities to taxa such as Endothiodon and Chelydontops, the exact relationships between A. kaayai and other dicynodonts are uncertain. The second specimen also consists of a partial skull and mandible. We refer it to cf. Endothiodontia based on the medial placement of the long maxillary tooth rows, the presence of depressions on the palatine pad, a long posterior dentary sulcus, and similarities of the mandibular dentition. Tetrapods occur in three fossiliferous horizons in the Ruhuhu Formation. The likely Middle Permian lower horizon includes dinocephalians, temnospondyls, and the dicynodonts described here. The middle horizon includes a new, tusked species of Endothiodon and at least one other dicynodont. The upper horizon appears to sample an assemblage similar to that of the Usili Formation and therefore may be of Late Permian age. The discovery of Middle Permian fossils in Tanzania and Zambia provides the opportunity to test whether southern Gondwana was characterized by a cosmopolitan tetrapod fauna for an extended period of time before the biogeographic restructuring caused by the end-Permian mass extinction.

Spalacotheriids, basal trechnotheres with an acutely angled, reversed-triangle pattern of major molar cusps, are relatively rare pan-Laurasian mammals that ranged through much of the Cretaceous but are generally not well represented in the fossil record. Herein we describe newly collected specimens from the Molino Alto 1 locality, Teruel Province, Spain, and review previously described materials from the nearby locality of Galve; the sites lie in the same horizon in the upper El Castellar Formation and are of early Barremian age. On this basis, we recognize and name Aliaga molinensis, gen. et sp. nov., and provisionally place in the same genus a previously described species, cf. Aliaga henkeli, comb. nov., which appears to be the largest known spalacotheriid. The two species are characterized by a distinctive, multicuspate cingulid on lower cheek teeth. Based on acuteness of molar cusp triangulation and other features (e.g., planar molar shearing surfaces, elongation and cusp pattern of penultimate premolar, reduction of last molar, simplification of upper molar crown pattern), the species are referred to the Spalacolestinae. This subfamily is most diverse in North America, where it ranged from Albian—Campanian, but first appears in the Barremian of Western Europe, supporting the hypothesis that the group had a Eurasian origin and later dispersed to North America.

Presented here are the tetralophodont proboscidean remains from the late Miocene locality Pikermi (Attica, Greece). The study of the Pikermi tetralophodons and their comparison with other relevant specimens revealed that the late Miocene species ‘Tetralophodon’ atticus and ‘Mastodon’ grandincisivus are synonymous. The morphological characters of the Pikermi specimens, as well as of those attributed to ‘Mastodon’ grandincisivus, are consistent with the North American shovel-tusker Amebelodon (Konobelodon). However, generic rank revision of Konobelodon at generic rank is deemed appropriate. The observed differences between the type species Konobelodon britti and the Pikermi tetralophodon indicate that the latter belongs to a distinct species, Konobelodon atticus. This species encompasses the Turolian tetralophodont shovel-tuskers from eastern Europe—western Asia. The paleogeographic distribution and biostratigraphy of Konobelodon atticus are discussed, as well as the evolution and the possible migrational scenarios of Konobelodon.