Complete Skull Research Articles

Descrição de um espécime juvenil de Baurusuchidae (Crocodyliformes: Mesoeucrocodylia) do Grupo Bauru (Neocretáceo): considerações preliminares sobre ontogenia

Entre os táxons de Crocodyliformes do Grupo Bauru (Neocretáceo), grande quantidade de morfótipos, incluindo materiais cranianos e pós-cranianos, vem sendo descrita em associação a Baurusuchus pachecoi. Porém, a falta de estudos ontogenéticos, como os realizados para Mariliasuchus amarali, levou à atribuição de novos gêneros e espécies aos poucos crânios completos encontrados. A presente contribuição traz a descrição de um espécime juvenil de Baurusuchidae depositado no acervo do Museu de Ciências da Terra no Rio de Janeiro sob o número MCT 1724 - R. Trata-se de um rostro e mandíbula associados e em oclusão, com o lado esquerdo melhor preservado que o direito, e dentição zifodonte extremamente reduzida. O fóssil possui 125,3 mm de comprimento preservado da porção anterior do pré-maxilar até a extremidade posterior do dentário; 117,5 mm de comprimento preservado do pré-maxilar aos palatinos e altura lateral de 51,4 mm. Entre as informações de caráter ontogenético identificadas destacam-se: ornamentação suave composta de estrias vermiformes muito espaçadas e largas, linha ventral do maxilar mais reta, dentário levemente inclinado dorsalmente na porção mediana e sínfise mandibular menos vertical que em outros baurussúquidos de tamanho maior. A maioria das características rostrais e dentárias, diagnósticas para Baurusuchus pachecoi, foi identificada no exemplar MCT 1724 - R: rostro alto e comprimido lateralmente, além de dentição zifodonte com forte redução dentária, que culmina em quatro dentes pré-maxilares e cinco maxilares. Portanto, como não pode ser separado morfologicamente da espécie-tipo do gênero e tendo sido encontrado em afloramentos da Formação Adamantina, é possível identificá-lo como um juvenil de Baurusuchus cf. pachecoi. Mudanças que podem ser observadas gradualmente dos morfótipos menores para os maiores, de caráter ontogenético, são: um aumento da ornamentação craniana; a porção mediana/posterior da linha ventral do maxilar passando de reta para côncava; e a verticalização da linha da sínfise mandibular para próximo de 45º.

Late Miocene large mammals from Ivand (Northwestern Iran)

Large mammalian fossil fauna of the Ivand locality in northwestern Iran is reported for the first time. This new locality is situated north of the city of Tabriz in the geographical proximity of the famous Maragheh fossil sites. A large hipparion, represented by an almost complete skull and mandibles, is recorded from this locality. The skull, most likely of Hipparion giganteum-Hipparion brachypus lineage, represents significant evidence of the presence of large hipparionine horses in northwestern Iran in the Late Miocene. A small number of horn-cores attributed to Oioceros atropatenes Rodler & Weithofer, 1890 and Gazella sp., in addition to some indeterminate dentition, represent the bovid material in the Ivand fossil assemblage. Postcranial evidence also points to the presence of Deinotherium giganteum Kaup, 1829 and Rhinocerotinae indet., while other material adds carnivorans, giraffes and large porcupine rodents to the list of the fauna. Based on the occurrence of these taxa, the Ivand locality can be correlated with the Middle and Upper Maragheh biostratigraphical intervals, thus demonstrating a middle Turolian age (c. 8–7 Ma).

A new ctenochasmatid pterosaur from the Lower Cretaceous, western Liaoning, China

A nearly complete skull of a new ctenochasmatid pterosaur, Pterofiltus qiui gen. et sp. nov., from the Lower Cretaceous deposits of Liaoning, China, is described here. The specimen (IVPP V12339), was collected from the shale of the lower Yixian Formation (125 Ma) at the Zhangjiagou locality. It has the following combination of characters: about 112 teeth in total (including the upper and lower jaws); the dentition occupies more than 50% of the skull length; the anterior teeth vary in size; the mandibular symphysis is longer than half of the whole mandible length; in ventral view, an apparent symphyseal trough in the median part of the symphysis.

A rhinesuchid-like temnospondyl from the Permo-Triassic of Uruguay

A new temnospondyl species, Arachana nigra, from the Permo-Triassic Buena Vista Formation of Uruguay is described. The holotypic and only known specimen consists of an almost complete skull lacking most of the snout, the tabular horns and the posterolateral corners of the skull table. As with other specimens from the same unit, Arachana shows a transitional morphology. It shares several characters with rhinesuchids, such as the large size and the general shape of the skull, orbits positioned slightly posterior to the skull roof mid-length, a coarsely pitted dermal ornamentation lacking pustules, and a smoothly convex cheek contour. The palatal ramus of the pterygoid suturing with the vomer, and excluding the palatine and ectopterygoid from the margin of the interpterygoid vacuity, and the presence of a small basioccipital, visible in both occipital and ventral view, also resemble the conditions found in rhinesuchids and other basal temnospondyls. Other characters present in Arachana, however, are commonly found in lydekkerinids, but are absent in almost all rhinesuchids: supratemporal excluded from otic notch; supraorbital and infraorbital sensory sulci encroaching the lacrimal, although lacking a step-like lacrimal flexure; otic notch not deeply incised; post-temporal fenestra large and rounded; occipital condyles well-separated from each other; palatine tooth row behind the palatine tusk reduced; pterygoid corpus slightly ornamented; and presence of an interorbital depression. This combination of primitive and derived characters is consistently present in most components of the Buena Vista fauna, which could thus be transitional between typical Permian and Triassic tetrapod communities found elsewhere. The location of the PTB in the Uruguayan sequence is controversial, mainly due to the lack of clear faunal correlations with other well-known sequences, such as those of southern Africa and Russia. Moreover, the mosaic-like character combinations in most of the recorded tetrapods ally them to both Triassic and Paleozoic groups, and this has complicated even more the possibility of age assignment. Transitional faunas associated with the PTB, such as the Russian Uppermost Permian faunas, could be equivalent to the unique Colonia Orozco fauna. If true, this scenario will substantially change estimates about survivorship rates, suggesting a speciation rate increase in temnospondyls after the Permian-Triassic event. Based on taxonomic, phylogenetic, and geochronologic data, the Buena Vista fauna allows us to quantify faunal turnover across the PTB and in the aftermath of the end Permian extinction event.

Oldest known pantherine skull and evolution of the tiger.

The tiger is one of the most iconic extant animals, and its origin and evolution have been intensely debated. Fossils attributable to extant pantherine species-lineages are less than 2 MYA and the earliest tiger fossils are from the Calabrian, Lower Pleistocene. Molecular studies predict a much younger age for the divergence of modern tiger subspecies at <100 KYA, although their cranial morphology is readily distinguishable, indicating that early Pleistocene tigers would likely have differed markedly anatomically from extant tigers. Such inferences are hampered by the fact that well-known fossil tiger material is middle to late Pleistocene in age. Here we describe a new species of pantherine cat from Longdan, Gansu Province, China, Panthera zdanskyi sp. nov. With an estimated age of 2.55–2.16 MYA it represents the oldest complete skull of a pantherine cat hitherto found. Although smaller, it appears morphologically to be surprisingly similar to modern tigers considering its age. Morphological, morphometric, and cladistic analyses are congruent in confirming its very close affinity to the tiger, and it may be regarded as the most primitive species of the tiger lineage, demonstrating the first unequivocal presence of a modern pantherine species-lineage in the basal stage of the Pleistocene (Gelasian; traditionally considered to be Late Pliocene). This find supports a north-central Chinese origin of the tiger lineage, and demonstrates that various parts of the cranium, mandible, and dentition evolved at different rates. An increase in size and a reduction in the relative size of parts of the dentition appear to have been prominent features of tiger evolution, whereas the distinctive cranial morphology of modern tigers was established very early in their evolutionary history. The evolutionary trend of increasing size in the tiger lineage is likely coupled to the evolution of its primary prey species.

Palaeolithic dog skulls at the Gravettian Předmostí site, the Czech Republic

Whether or not the wolf was domesticated during the early Upper Palaeolithic remains a controversial issue. We carried out detailed analyses of the skull material from the Gravettian Předmostí site, Czech Republic, to investigate the issue. Three complete skulls from Předmostí were identified as Palaeolithic dogs, characterized by short skull lengths, short snouts, and wide palates and braincases relative to wolves. One complete skull could be assigned to the group of Pleistocene wolves. Three other skulls could not be assigned to a reference group; these might be remains from hybrids or captive wolves. Modifications by humans of the skull and canine remains from the large canids of Předmostí indicate a specific relationship between humans and large canids.

Skull reconstruction and ecology of Urmiatherium polaki (Bovidae, Mammalia) from the upper Miocene deposits of Maragheh, Iran

Study of a newly discovered cranial specimen of Urmiatherium polaki from Karaj Abad site in Maragheh, Iran, allows us to describe the complete skull and present a new diagnosis for this late Miocene mammal species. In the comparative study of the specimen we propose the relative position of the upper teeth as a reliable metrical method for discriminating bovids of similar size. Based on the available information, a skull reconstruction of Urmiatherium polaki is provided and its ecological profile is outlined. Both the cranial and dental features of U. polaki indicate a gregarious grazing bovid of medium size, adapted to uneven ground and exhibiting ramming as the predominant fighting behavior.

A new ctenochasmatoid pterosaur from the Early Cretaceous Yixian Formation of western Liaoning, China

A new ctenochasmatoid pterosaur, Gladocephaloideus jingangshanensis gen. et sp. nov. from the Yixian Formation of western Laioning Province is erected based on a complete skull and partial postcranial skeleton. It is characterized by following features: about 50 total teeth with sharp tips; small nasoantorbital opening, occupying approximately 13% of the skull length; ratio of prenarial length to skull length approximately 0.63. The diagnoses of the Ctenochasmatoidea and Gallodactylidae are amended based on the new taxon. Gladocephaloideus jingangshanensis is the first gallodactylid pterosaur found in Asia. Its discovery not only provides much more osteological information about the Gallodactylidae but also indicates that the ctenochasmatoid pterosaurs were highly diverse in the Early Cretaceous. The filamentous structures preserved near the dorsal and posterior margins of the posterior portion of the skull and around the neck indicate that it had an epidermal covering and may have been a warm-blooded animal.

Griphotherion peiranoi, gen. et sp. nov., a new Eocene Notoungulata (Mammalia, Meridiungulata) from northwestern Argentina

ABSTRACT Griphotherion peiranoi, a new genus and species of notoungulate from northwestern Argentina, is presented here. The material studied consists of a nearly complete skull and part of the postcranial skeleton, recovered in the Lumbrera Formation (Eocene) at the locality of El Simbolar (Salta Province, northwestern Argentina). The specimen was evaluated in terms of a matrix of 28 craniodental characters and compared with 11 typotherian genera. Additionally, characters of the new taxon were compared to those included in a previously published data matrix that includes several native South American ungulates. The particular features present in the specimen indicate unequivocally that this is a new notoungulate taxon; nevertheless, due to its distinctiveness, we opted not to place the novel taxon in any of the known families of Notoungulata. The results of the analyses performed indicate that G. peiranoi is closely related to Mesotheriidae, Hegetotheriidae, and Archaeohyracidae. These families represent the ‘rodent-like’ notoungulates that evolved during the Late Paleogene and the Neogene. This new record contributes to our knowledge of the Eocene notoungulate fauna of northwerstern Argentina. It also supports the broader perspective that this region played an important role as an area of origin and diversification for several lineages of this remarkable order of endemic South American ungulates.

Iberian mastodonts: Geographic and stratigraphic distribution

The Iberian Peninsula has a complete Mio-Pliocene fossil record in which all biostratigraphic units are represented. As a consequence, there is an exceptional proboscidean record including deinotheres, mastodonts and elephants, which has increased significantly in recent years. Many of the older localities are not known in the common paleontological literature because only or mainly proboscidean remains were collected. This paper presents an overview of the localities yielding mastodont remains.Gomphotherium angustidens dispersed into Europe during late MN3. The oldest Spanish record is possibly from early MN4 (zone B of the Aragonian). There are over 125 Iberian localities. The material includes skulls and more or less complete skeletons. The youngest localities are from the lower part of MN7+8.Tetralophodon longirostris replaced Gomphotherium during the latest Aragonian. This event is well reflected in the Spanish record and the first Tetralophodon appears in localities that belong to the upper part of MN7+8. Together with other faunal changes, this event strengthens the idea that MN7 and MN8 can be recognized as separate units. The species is known from over 70 Iberian localities, some of which yielded complete skulls and relatively complete skeletons. At Crevillente II (MN11) a tetralophodont form is found with morphometric similarities to Stegotetrabelodon.Anancus arvernensis replaced Tetralophodon during the Latest Miocene (MN12). This event is well documented in the Iberian Peninsula. This species is found at over 20 localities and is particularly well represented at Las Higueruelas (MN 16; 3.1‑2.9Ma) with many skulls and abundant remains of the different parts of the skeleton. The last Iberian record is in Villarroya (MN 16) and La Florida (E Pleistocene).Zygolophodon turicensis dispersed late in MN3 into Europe, but in Spain it is known from few localities from the Middle Miocene (MN5–7). It evolved into Mammut borsoni, which in Spain is known from some Upper Miocene to Lower Pliocene localities.Overall, the Iberian mastodont record is similar to that of the rest of Europe. The bunodont and zygodont mastodonts overlapped during many millions of years, but at any moment the zygodont species were much less abundant in the Iberian record. Proboscidean dispersals from Africa towards Western and central Europe show a peculiar pattern: several dispersals occurred during the Mid-Miocene Climatic Optimum and again during the Pleistocene, but not during the long time interval between. After the optimum came the Mid-Miocene Crisis, when global temperatures dropped, which probably did not favor northward proboscidean dispersals. When, during the Late Miocene C4 grasslands spread at low latitudes, most Proboscideans adapted to grazing and may have become pre-adapted for living in the seasonal climates of the higher latitudes, and dispersed again to the north. This mirrors the hominoid dispersals from Africa to Europe, which occurred also during the Mid-Miocene and Pleistocene.

Partial skeleton of Theropithecus brumpti (Primates, Cercopithecidae) from the Chemeron Formation of the Tugen Hills, Kenya

Here we describe a complete skull and partial skeleton of a large cercopithecoid monkey (KNM-TH 46700) discovered in the Chemeron Formation of the Tugen Hills at BPRP Site #152 (2.63 Ma). Associated with the skeleton was a mandible of an infant cercopithecoid (KNM-TH 48364), also described here. KNM-TH 46700 represents an aged adult female of Theropithecus brumpti, a successful Pliocene papionin taxon better known from the Omo Shungura Formation in Ethiopia and sites east and west of Lake Turkana, Kenya. While the morphology of male T. brumpti is well-documented, including a partial skeleton with both cranial and postcranial material, the female T. brumpti morphotype is not well-known. This skeleton represents some of the first associated evidence of cranial and postcranial female T. brumpti remains. In addition to the complete skull, postcranial material includes elements of the axial skeleton and lower limb. While aspects of the skeleton conform to those of specimens previously assigned to T. brumpti, other features on the femur and tibia appear to differ from those previously described for this species. It is unclear whether these differences represent general variation within the T. brumpti population, variation between the sexes in T. brumpti, or the incorrect assignment of previous isolated hindlimb specimens. In total, the observable morphological features of the hindlimb suggest that KNM-TH 46700 was a terrestrial quadruped similar to modern savannah baboons ( Papio). From the available evidence, it is difficult to assess whether or not KNM-TH 46700 frequently engaged in the specialized squatting and shuffling behavior observed in extant geladas ( Theropithecus gelada).

First complete skull of an octodontoid (Rodentia, Caviomorpha) from the Early Miocene of South America and its bearing in the early evolution of Octodontoidea

Octodontoidea is the most diverse group of caviomorph rodents. The systematics of most of the fossil representatives has been essentially based upon dental characters. Described here is an almost complete skull with dentition assigned to Prospaniomys Ameghino based upon its dental morphology. The specimen comes from the Sarmiento Formation at Pampa de Gan Gan (central Patagonia, Argentina), assigned to the Colhuehuapian SALMA (early Miocene). The most remarkable features are in the posterior portion of the skull, some of them shared with the modern octodontids and interpreted as specialized by previous authors, which contrast with the generalized dental morphology. These combined features were not previously known in other octodontoids. The comparisons with other fossil and extant members of the superfamily suggest that the characters traditionally used to associate Prospaniomys with the echimyids are very probably plesiomorphies. Prospaniomys would represent an early diverging lineage more closely related to modern octodontids than to echimyids, in which cranial structures evolved more rapidly than dental and mandibular ones.

A new baurusuchid (Crocodyliformes, Mesoeucrocodylia) from the late cretaceous of Brazil and the phylogeny of Baurusuchidae.

BackgroundBaurusuchidae is a group of extinct Crocodyliformes with peculiar, dog-faced skulls, hypertrophied canines, and terrestrial, cursorial limb morphologies. Their importance for crocodyliform evolution and biogeography is widely recognized, and many new taxa have been recently described. In most phylogenetic analyses of Mesoeucrocodylia, the entire clade is represented only by Baurusuchus pachecoi, and no work has attempted to study the internal relationships of the group or diagnose the clade and its members.Methodology/Principal FindingsBased on a nearly complete skull and a referred partial skull and lower jaw, we describe a new baurusuchid from the Vale do Rio do Peixe Formation (Bauru Group), Late Cretaceous of Brazil. The taxon is diagnosed by a suite of characters that include: four maxillary teeth, supratemporal fenestra with equally developed medial and anterior rims, four laterally visible quadrate fenestrae, lateral Eustachian foramina larger than medial Eustachian foramen, deep depression on the dorsal surface of pterygoid wing. The new taxon was compared to all other baurusuchids and their internal relationships were examined based on the maximum parsimony analysis of a discrete morphological data matrix.ConclusionThe monophyly of Baurusuchidae is supported by a large number of unique characters implying an equally large morphological gap between the clade and its immediate outgroups. A complex phylogeny of baurusuchids was recovered. The internal branch pattern suggests two main lineages, one with a relatively broad geographical range between Argentina and Brazil (Pissarrachampsinae), which includes the new taxon, and an endemic clade of the Bauru Group in Brazil (Baurusuchinae).

A new specimen of Chasmosaurus belli (Ornithischia: Ceratopsidae), a revision of the genus, and the utility of postcrania in the taxonomy and systematics of ceratopsid dinosaurs

A previously undescribed chasmosaurine specimen excavated in 1919-1920 by William Cutler from the Dinosaur Park Formation of Alberta, Canada is referable to Chasmosaurus belli. The specimen comprises an almost complete skull in which, uniquely among Chasmosaurus, the cranial elements are disarticulated, allowing detailed examination of their morphology for the first time. The complete braincase is present and allows comparison with the braincase of other ceratopsians. The specimen also preserves an uncrushed and undistorted postcranium, including cervical, dorsal and sacral vertebrae and limb elements. The vertebral column of Chasmosaurus has never previously been described in detail, and NHMUK R4948 affords the opportunity to examine it because of the unparalleled state of vertebral preservation. A proliferation of new chasmosaurine genera has recently been described; many of them differ from each other only in details of frill and epiparietal morphology. Several of these are based on specimens previously referred to Chasmosaurus. As a result, the characters that distinguish Chasmosaurus from other Campanian chasmosaurines are unclear. However, the genus Chasmosaurus and species within the genus are diagnosable and valid based on unique combinations of characters and frill morphology. Detailed examination of the postcranial morphology of a variety of centrosaurines and chasmosaurines has highlighted previously undescribed synapomorphies for the two major ceratopsid clades, concentrated in the pectoral girdle and forelimb. Inconsistencies in the vertebral formula of specimens referred to Chasmosaurus belli suggests that the postcrania of ceratopsids may vary between species and genera far more than previously thought, and that postcranial characters should be incorporated into phylogenetic and taxonomic studies.

The first Choerolophodon (Proboscidea, Gomphotheriidae) skull from China

Here we report the first discovery of a relatively complete skull of Choerolophodon from the late early Miocene Dalanggou quarry of Linxia Basin, Gansu Province in China. The skull is low and elongated, with two enamel-less and outward-and-upward curved incisors and the choerolophodont molars. These characters indicate that the new specimen can be assigned to the genus Choerolophodon, as it is quite distinct from other common gomphotheres in northern China such as Gomphotherium, Platybelodon, and Sinomastodon. The skull is also primitive in possessing laterally-expanded zygomatic arches, anteriorly-positioned orbits, weakly-developed cheek teeth cement, and retention of a P4. Prior to this discovery, Choerolophodon was found primarily from the middle-late Miocene of Africa, Eastern Europe, and western and southern Asia. The discovery of this new material expands the known temporal and spatial distributions of this taxon and helps us better understand the phylogeny, evolution, and adaptive radiation of gomphotheres in early Miocene of China.

Earliest evidence of mammalian social behaviour in the basal Tertiary of Bolivia

The vast majority of Mesozoic and early Cenozoic metatherian mammals (extinct relatives of modern marsupials) are known only from partial jaws or isolated teeth, which give insight into their probable diets and phylogenetic relationships but little else. The few skulls known are generally crushed, incomplete or both, and associated postcranial material is extremely rare. Here we report the discovery of an exceptionally large number of almost undistorted, nearly complete skulls and skeletons of a stem-metatherian, Pucadelphys andinus, in the early Palaeocene epoch of Tiupampa in Bolivia. These give an unprecedented glimpse into early metatherian morphology, evolutionary relationships and, especially, ecology. The remains of 35 individuals have been collected, with 22 of these represented by nearly complete skulls and associated postcrania. These individuals were probably buried in a single catastrophic event, and so almost certainly belong to the same population. The preservation of multiple adult, sub-adult and juvenile individuals in close proximity (<1 m(2)) is indicative of gregarious social behaviour or at least a high degree of social tolerance and frequent interaction. Such behaviour is unknown in living didelphids, which are highly solitary and have been regarded, perhaps wrongly, as the most generalized living marsupials. The Tiupampan P. andinus population also exhibits strong sexual dimorphism, which, in combination with gregariousness, suggests strong male-male competition and polygyny. Our study shows that social interactions occurred in metatherians as early as the basal Palaeocene and that solitary behaviour may not be plesiomorphic for Metatheria as a whole.

An extinct map turtle Graptemys (Testudines, Emydidae) from the late Pleistocene of Florida

ABSTRACT Graptemys kerneri, n. sp., from the Suwannee River drainage of north-central Florida, represents the most southeastern occurrence of the genus. This species is morphologically and geographically most similar to the extant Barbour's map turtle, Graptemys barbouri. G. kerneri exhibits sexual dimorphism similar to extant G. barbouri, G. ernsti, G. pulchra, and G. gibbonsi, with females being megacephalic and attaining a much larger size than males. The new species possesses a very wide skull and mandible, making it the most blunt-headed member of its clade. Specimens described here include a nearly complete skull, eight mandibles, two epiplastra, 34 neural bones, and an assortment of other shell fragments. Previously reported fossil material from Florida was collected in the 1960s along the Santa Fe River and referred to both the Pliocene and Pleistocene. Rare earth element (REE) analysis of this material is reinterpreted here as being Rancholabrean in age.

Associated skeletons of a new middle Triassic “Rauisuchia” from Brazil

For more than 30 million years, in early Mesozoic Pangea, "rauisuchian" archosaurs were the apex predators in most terrestrial ecosystems, but their biology and evolutionary history remain poorly understood. We describe a new "rauisuchian" based on ten individuals found in a single locality from the Middle Triassic (Ladinian) Santa Maria Formation of southern Brazil. Nine articulated and associated skeletons were discovered, three of which have nearly complete skulls. Along with sedimentological and taphonomic data, this suggests that those highly successful predators exhibited some kind of intraspecific interaction. Other monotaxic assemblages of Triassic archosaurs are Late Triassic (Norian-Rhaetian) in age, approximately 10 million years younger than the material described here. Indeed, the studied assemblage may represent the earliest evidence of gregariousness among archosaurs, adding to our knowledge on the origin of a behavior pattern typical of extant taxa.

On a new peirosaurid crocodyliform from the Upper Cretaceous, Bauru Group, southeastern Brazil

A new crocodyliform from the Upper Cretaceous (Campanian-Maastrichtian) Presidente Prudente Formation of the Bauru Group is described based on two almost complete skulls and mandibles. The material comes from the "Tartaruguito" site, situated at an old railroad between the cities of Pirapozinho and Presidente Prudente, state of São Paulo, Brazil. The new species, Pepesuchus deiseae gen. et sp. nov., is classified in the clade Peirosauridae on the basis of three synapomorphies: the presence of five premaxillary teeth, the anterior two premaxillary alveoli nearly confluent, and the oval cross-section of the jugal along the lower temporal bar. The new taxon increases the outstanding crocodyliform diversity of the Bauru Group, particularly of the Peirosauridae, which might turn out to be one of the most representative clades of gondwanan mesoeucrocodylians.

NewTapirusspecies (Mammalia: Perissodactyla: Tapiridae) from the upper Pleistocene of Amazonia, Brazil

A new species of Tapirus (Perissodactyla: Tapiridae) is described from the upper Pleistocene of the Rio Madeira Formation in Araras, Nova Mamore Municipality, Rondonia State, Brazil. Tapirus rondoniensis sp. nov. is represented by a nearly complete skull with a unique combination of characters that differ from those of extant and fossil species of Tapirus described from South America. It is diagnosed mainly by its broad frontals that bear a pneumatization extending to the frontoparietal suture, a high sagittal crest, a weakly molarized P2 lacking a protoloph, and a metaloph that merely reaches the base of the ectoloph. T. rondoniensis sp. nov. is similar in some respects to T. terrestris, but it retains some primitive dental and cranial character states in common with T. pinchaque, such as broad frontals and a weakly molarized P2.