We report a new early–middle Eocene cylindrodontid rodent, Gobiocylindrodon ulausuensis, gen. et sp. nov., from the Ula Usu West locality, Erlian Basin, Nei Mongol, China. Gobiocylindrodon ulausuensis is morphologically more primitive than known later cylindrodontids in having lower-crowned molars, less-rounded upper molars in occlusal view, a more oblique hypolophid on p4, a slightly anterolabially extended hypoconid on m1–3, and a narrow posterosinusid posteriorly and a broad mesosinusid anteriorly on the lower cheek teeth. The lower incisor enamel of G. ulausuensis is pauciserial. Our phylogenetic analysis of a data matrix including 14 taxa and 40 morphological characters reveals that G. ulausuensis is a basal cylindrodontid. Gobiocylindrodon ulausuensis casts new light on early cylindrodontid evolution in Asia and provides new evidence for mammalian dispersals between Asia and North America during the early–middle Eocene. Gobiocylindrodon-bearing strata are probably Arshantan in age.

The holotype of the elasmosaurid Aphrosaurus furlongi from the Maastrichtian levels of the Moreno Formation is redescribed and considered a valid species based on one autapomorphy, a deep trough in the ventral surface of vertebral centra of the posterior cervicals, and the following combination of features: wide and short clavicle-interclavicle complex with concave anterior border and without posterior medial process or medial ventral keel, humerus with anterior depression, and posterior limb with accessory element on the posterior margin. The phylogenetic analysis recovered A. furlongi as an elasmosaurid within Weddellonectia. The phylogenetic analysis generated a new topology of Elasmosauridae. A new clade, Euelasmosaurida, is recovered, including all post-Cenomanian elasmosaurids other than Zarafasaura oceanis. Euelasmosaurida is composed of two main clades: Elasmosaurinae and Weddellonectia. The latter includes mostly Weddellian elasmosaurids, including Aristonectinae. Based on the new phylogenetic results, the evolution of key cranial and postcranial characters is discussed. Two key intervals of elasmosaurid evolutionary history are recognized: the Cenomanian, with the appearance of Euelasmosaurida, and the Santonian, with the differentiation of Weddellonectia and Elasmosaurinae.

Ornithosuchidae is a group of terrestrial quadrupedal pseudosuchian archosaurs from the Late Triassic of South America and Europe. Riojasuchus tenuisceps is arguably one of the best representative species of this clade because it comprises very well-preserved three-dimensional, almost complete skeletons. However, R. tenuisceps was originally described 50 years ago and compared then only with Ornithosuchus woodwardi and their affinities were discussed in detail. Here, we provide a detailed description of the postcranial skeleton of R. tenuisceps, which exhibits several remarkable features within pseudosuchians. When a wide spectrum of pseudosuchian archosaurs are considered, the alleged character that linked ornithosuchids with dinosaurs resulted in convergences and some were registered in other pseudosuchian groups as well. Riojasuchus tenuisceps also provided crucial information about the ‘crocodile-reversed’ tarsus, which is a unique feature of ornithosuchids, but it is not completely preserved in O. woodwardi and it is unknown in Venaticosuchus rusconii. In addition, the first histological analysis of cervical and dorsal osteoderms of R. tenuisceps was carried out as well, in order to test the utility of these structures as skeletochronological tools. Finally, the phylogenetic context of Ornithosuchidae is discussed based on the latest phylogenetic studies, which show a close affinity with Erpetosuchidae.

Seymouriamorphs are a group of Permo-Carboniferous tetrapods with both terrestrial and aquatic members. Since their initial discovery, they have been proposed as phylogenetic intermediates on the amniote stem between temnospondyl amphibians and crown amniotes and are thus frequently used in phylogenetic analyses of both early amniotes and, more broadly, Paleozoic tetrapods. We utilized neutron computed tomography (nCT) to study the morphology of the first cranial material of Seymouria from the early Permian karst deposits found at the Dolese Brothers Limestone Quarry near Richards Spur, Oklahoma. The presence of a mixture of purported autapomorphies of both of the better-known species of Seymouria, S. baylorensis and S. sanjuanensis, prevents referral to either species; the potential for ontogenetic variation in many of these characters highlights the need to reevaluate the taxonomy of these species. Our description of the tomographic data focuses on the braincase and otic capsule and helps to clarify details of previously poorly known neurocranial anatomy, such as an orbitosphenoid that expands dorsally to abut the overlying frontals. The prootic and the opisthotic are complex structures that preserve clear impressions of all three semicircular canals and that frame the laterally extensive otic tube and possibly the perilymphatic duct. Our analysis provides additional details regarding a previously described but poorly known ossification of the synotic tectum and highlights the ongoing uncertainty regarding the homology of such ossifications across Paleozoic tetrapods.

Although the North Pacific has been a key area for investigations into seabird ecology and evolution, the seabird fossil record has been scarce on the western North Pacific. This study describes new seabird remains from the Pleistocene Kazusa and Shimosa groups, central Honshu Island, Japan, adding new insight into the Pleistocene seabird fauna in the region. Avian materials from four formations (the Hirayama, Ichijiku, and Mandano formations in the Kazusa Group and the Kiyokawa Formation in the Shimosa Group) include at least nine species of seabirds and other waterbirds: Melanitta fusca, Clangula hyemalis, Anatidae? gen. et sp. indet., Gavia stellata?, Phoebastria cf. albatrus, Puffinus cf. puffinus complex, Phalacrocoracidae gen. et sp. indet., Alle cf. alle, and Mancalla sp. Most of these occurrences represent the oldest records for the respective taxa in the western North Pacific. The occurrence of Alle from the Ichijiku Formation (∼0.7 Ma) is especially noteworthy, because modern Alle alle, the sole recognized member of the genus, is rarely recorded in the Pacific today. This record suggests that in the middle Pleistocene, the taxon was probably more widespread in the North Pacific than it is today. Therefore, the present-day distribution of these seabirds is likely a relict of past ones, as has also been documented in some other seabird lineages.

The genus Trichechus (Mammalia, Sirenia, Trichechidae) harbors a modest diversity, comprising only three living species of manatees, and no species currently recognized as fossil. Herein, we report a new extinct species of manatee from the late Pleistocene of the Brazilian Amazonia, Trichechus hesperamazonicus, sp. nov. It comes from the alluvial deposits of the Rio Madeira Formation along the Madeira River, state of Rondônia, western Brazil, and is represented by a partial palate with both molar series and two partial right dentaries. The new taxon shows a mosaic of characteristics resembling those of other manatee species, as well as some unique characters. It differs from all other Trichechus species by possessing a wide space between the posterior lower tooth row and ascending ramus of dentary, and by having the anterior border of the ascending ramus covering the posterior end of the tooth row in lateral view. The results of morphometric analyses (principal component analysis and discriminant analysis) further support the distinctiveness of the new species. A phylogenetic analysis recovers the new species in a polytomy with T. inunguis and the clade formed by T. senegalensis and T. manatus. The levels from which the remains were recovered produced a radiocarbon date of 44,710 ± 880 years before present; together with molecular clock estimates, this date suggests that until recently at least two species of manatees coexisted in the fluvial systems of western Amazonia.

We here report the first documented occurrence of a gonorynchiform from the Mesozoic of Canada, represented by disarticulated material recovered from multiple localities in the Lethbridge Coal Zone, in the Late Cretaceous Campanian upper Dinosaur Park Formation of southern Alberta. Despite the preservation of these specimens as disarticulated and isolated microvertebrate material, we can identify this fish as the gonorynchid Notogoneus. Although this material was recovered from estuarine settings, the local environment was freshwater, and this occurrence does not constitute evidence that this species of Notogoneus was amphidromous, as has previously been hypothesized for early gonorynchids. We offer suggestions regarding the whole-body anatomy of the fish represented in our sample through comparisons with articulated specimens of Notogoneus osculus from the Green River Formation as well as with modern comparative material. Such details include a narrow mouth in a ventral position and probable possession of branchial tooth plates, from which aspects of the ecology of this fish can be deduced, such as durophagy and a probable demersal environmental preference. Additionally, these comparisons highlight the mosaic evolution of early gonorynchids, combining a primitively chanid-like vertebral anatomy and a more derived, Gonorynchus-like jaw.

The sternum is a functionally important but poorly understood component of the pectoral girdle in both living and extinct dinosaurs. When ossified, the dinosaur sternum consists of paired plates situated just posterior to the clavicles and scapulocoracoid. In Avialae, the sternal plates are fused at the midline to form a single element, aiding in powered flight. Our understanding of the early evolutionary history of the theropod sternum is complicated by a lack of fossil material, especially outside Maniraptoriformes, both because of taphonomic biases and incomplete ossification. Here, we report the oldest-known dinosaur sternal plates from the Late Triassic taxon Tawa hallae recovered from the Hayden Quarry at Ghost Ranch, New Mexico, as well as an isolated sternal plate from just south of Petrified Forest National Park, Arizona. These specimens expand the fossil record and allow for reconstruction of early theropod sternal musculature. They bear morphological features that are surprisingly similar to sternal traits in avialans, including a sternocoracoidal process, costal processes, and possible homologs to the ‘coracoid facet’ and pila coracoidea. The presence of these features in T. hallae pushes their appearance back to the Late Triassic, well before the development of the modern avian sternum. The variable distribution of sternal character states across avemetatarsalians was previously recognized in later Cretaceous avialans and can now be shown to also characterize the early evolution of the theropod sternum.

The domestic cat-sized marsupial lion Priscileo roskellyae (Thylacoleonidae) from the Oligocene–Miocene of Australia was originally allocated to the genus PriscileoRauscher, 1987, on the basis of its plesiomorphic upper dental formula of three premolars and four molars and its relatively small size. Recent reassignment of the Priscileo type species P. pitikantensis to the genus Wakaleo has now necessitated establishment of a new generic name for the species roskellyaeGillespie, 1997. In contrast to W. pitikantensis, which is only known from a fragmented palate and associated postcranial elements, the skull and lower dentition of P. roskellyae, described here, exhibit features that support its generic distinction within Thylacoleonidae. It is renamed here Lekaneleo roskellyae, comb. nov. Distinctive craniodental features include small sagittal and nuchal crests, lack of a prominent rostral tympanic process on the periotic, lack of alisphenopalatine pterygoid processes, a stylomastoid sulcus that courses through the mastoid, three teeth between i1 and p3, and very broad talonid basins on the lower molars. In contrast to species of Wakaleo, which appear to form a morphocline during the late Oligocene and early Miocene, L. roskellyae is a relatively conservative taxon, exhibiting no discernible change over the same interval of time.

‘Partanosaurus zitteli’ is an obscure and doubtful sauropterygian taxon from the Ladinian (Middle Triassic) of the Austrian Alps, described at the end of the 19th century and based on isolated axial and pectoral remains belonging to a single individual. For more than 20 years, it has been considered an invalid species, belonging to the much better known sauropterygian genus Simosaurus, also from the European Ladinian record. The revision of the type species of Simosaurus (i.e., Simosaurus gaillardoti, considered to be the only representative of the monospecific clade Simosauridae until recent times), the recent definition of a new simosaurid taxon (i.e., Paludidraco multidentatus), and the discovery in the past decade of new European Upper Triassic simosaurid remains not attributable to any of those two species permit a better understanding of the Simosauridae clade. The validity of ‘P. zitteli’ is revised based on these new findings. Its previous proposal as a junior synonym of S. gaillardoti cannot be justified here, but we opt to declare it a nomen dubium, considering the scarce material currently attributed to it and the absence of autapomorphies. We recognize a higher diversity for the clade Simosauridae than previously expected. Emended diagnoses for S. gaillardoti and Pa. multidentatus are provided, based on the review of the known simosaurid specimens, including the holotype of ‘P. zitteli.'

Since its first description, only a single undisputed specimen, an isolated, highly abraded m1, was known from the enigmatic amphicyonid Agnotherium antiquum Kaup, 1833. Here, we describe the second specimen of A. antiquum from the type locality of Eppelsheim (early late Miocene, MN 9/10 of Germany), unearthed 184 years after the first description of A. antiquum. The specimen consists of a partial left juvenile mandible with dp3, m1 in eruption, i3, canine, p4, and a highly reduced m2 still in crypt. The p1–3 and m3 are completely reduced, as are the metaconids of m1 and m2. We confirm previous assignments of late Miocene specimens from the localities of Charmoille, Switzerland, and Pedregueras 2A, Spain, to A. antiquum, whereas a maxilla from Bled Douarah, Tunisia, can only tentatively be assigned to the species. We confirm that the monotypic genus Agnotherium is a thaumastocyonine amphicyonid, discuss other supposed thaumastocyonine specimens, and briefly review the evolutionary history of the subfamily. Agnotherium was a 275 kg, extremely powerful, strictly carnivorous ambush hunter that represents the apex of amphicyonid evolution toward carnivory. Its tooth eruption pattern resembles recent Ursus more than recent Canis, but it shows a considerable delay of eruption timing like in the ursid Agriotherium. Agnotherium antiquum is one of six carnivoran species from the Eppelsheim Formation that is heavier than 200 kg. The co-occurrence of Agnotherium (or its relatives Tomocyon and Thaumastocyon), Machairodus, and a smaller saber-toothed carnivoran is typical for early late Miocene faunas of Europe and tentatively North Africa.

This article deals with the fossil tortoises of one of the most iconic fossil localities of the Neogene of the Old World, the upper Miocene locality of Pikermi, near Athens, Greece. We describe the type, previously published, and new material of the fossil tortoises from Pikermi, along with new material from the coeval Azmaka 6 locality in Bulgaria. This combined information results in the complete revision of the ‘marble tortoise' Testudo marmorum, which is the first turtle species ever named from Greece. Besides the challenges and difficulties of working with material from the old collections of Pikermi, we present a complete revision of this species and identify its presence outside its type locality in the South Balkan Peninsula. The presence of numerous shells of the ‘marble tortoise’ allows us to discuss the observed variation and attempt to interpret it as the result of intraspecific variation, ontogenetic changes, or sexual dimorphism. For the first time, we observe the absence of the characteristic hypo-xiphiplastral hinge in female individuals of Testudo marmorum, which in turn challenges the traditional phylogenetic position of this species. We further describe previously published and new material of the giant tortoise Titanochelon from Pikermi. Based on the updated information, we can suggest that the Pikermian giant tortoise probably represents a distinct taxon. Our results signal Pikermi as one of the most important localities to understand the evolution of tortoises in the eastern Mediterranean during the last parts of the Neogene.

The locality of Udabno, Georgia, preserves material referred to the hominoid primate Dryopithecus. In this study, we describe the microvertebrate fauna from the site, which includes fishes (Scardinius sp., Carassius sp.), anurans (Pelophylax sp.), squamates (Lacertidae indet., Ophidia indet.), insectivores (Schizogalerix sinapensis, Turiasorex cf. pierremeini), and rodents (Byzantinia pikermiensis, Hansdebruijnia erksinae, Vasseuromys pannonicus). The association of two rodents, the cricetid B. pikermiensis and the murid H. erksinae, constrains the age of the Udabno fauna more precisely than previous studies. Byzantinia pikermiensis was first recognized at the site of Pikermi, Chomateri, and later recovered in other sites from Turkey, including the hominid-bearing site of Çorakyerler. The murid H. erksinae was also described from Çorakyerler in Turkey. Therefore, the presence of these rodents at Udabno indicates that the fauna postdates late Vallesian faunas such as Biodrak, Greece, and Bayraktepe II, Turkey, which are characterized by the association of the more archaic species Byzantinia nikosi and Progonomys cathalai. This study demonstrates that Udabno is temporally equivalent to typical Turolian sites from the Mediterranean area, such as Pikermi, Çorakyerler, and Crevillente 2.

Mesoclemmys is the most diverse extant genus of South American pleurodires or side-necked turtles, with at least 10 species inhabiting fluvial to littoral environments. Despite this high extant diversity and extensive geographic distribution, the evolutionary history and fossil record of this genus are completely unknown. Here, we describe the first fossil record of this genus, which supports a previous molecular-based hypothesis that indicates a minimum split time of 13.5 Ma between this and other genera of South American chelids. Mesoclemmys vanegasorum, sp. nov., is represented by a nearly complete shell (carapace and plastron) and some postcranial bones found in the middle Miocene (13.6 ± 0.2 Ma), La Victoria Formation, Tatacoa Desert, Colombia, increasing the turtle paleodiversity of La Venta Fauna. It differs from all extant species of Mesoclemmys by vertebral scute 1 reaching the sutural boundary between peripherals 1 and 2; shorter cervical and marginal scutes 1 to 3; pleurals 1 very advanced over the peripherals; pygal bone with a posteromedial shallow notch; vertebral 5 covering half of the pygal bone; small extragulars reaching only half of the epiplastra length; and a fine microvermiculation of the shell. Our phylogenetic results show a close relationship between M. vanegasorum, sp. nov., and the extant M. hogei. The overall morphology and size of Mesoclemmys genus have remained relatively constant for at least the last 13.6 million years. However, its geographic distribution has decreased drastically in northwestern South America, being restricted today to the lower region of the Magdalena River Basin.

Recent molecular analyses suggest that the evolutionary history of Cingulata (Xenarthra) could be more complex than believed previously. An ancient divergence was proposed for armadillos, recognizing two large monophyletic groups: Dasypodidae (including Dasypodinae) and Chlamyphoridae (including Euphractinae, Tolypeutinae, and Chlamyphorinae). Extant Chlamyphorinae (fairy armadillos) are among the most bizarre, elusive, and unknown mammals of the world. Here, we report the first accurate fossil record of this enigmatic xenarthran from the upper Miocene of the Argentine Pampas in southern South America, which represents a new genus and species (Chlamyphractus dimartinoi, gen. et sp. nov.). The phylogenetic analysis reflects the monophyly of the chlamyphorines. It is well supported by several unambiguous synapomorphies and includes the new fossil taxon as a sister group of the two extant species. This new taxon represents the most basal lineage among Chlamyphorinae and increases its diversity. The morphology of the forelimb suggests that it would have been a good digger, although, unlike extant species, it would not have had ‘fully’ subterranean habits.

The Hemingfordian North American Land Mammal Age is a poorly known time period, although recently discovered sites in central Oregon have begun to cast light on a diverse mammalian fauna. Here, we describe four small carnivorans new to this region, one of which is a new species. Cryptailurus tinaynakti, sp. nov., is a hypercarnivorous feliform. UOMNH F-70218 is the dp4 of a diminutive mustelid similar in morphology to that of extant martens, but likely of a new species based upon discussed patterns in mustelid deciduous dentition. The occurrence of two additional species, Leptocyon leidyi and Bassariscus antiquus, increases both their geographic and temporal ranges. The early to middle Miocene was a time of transition from sparse woodland to grassland ecosystems in much of North America. The Hemingfordian fauna of the Pacific Northwest inhabited a diverse wet woodland ecosystem, surprisingly rich in carnivorans. With the description of these additional small taxa, we can now get a clearer picture of what must have been a diverse assemblage of mammals with a variety of ecological roles in an undersampled period of time.