New dental and postcranial specimens of Pantolestes from the Uinta Basin, Utah, are described, and species-level diversity of Pantolestes from the Bridgerian and Uintan North American Land Mammal Ages is assessed. Because few morphological features can be found to distinguish species, we use size as the primary criterion for species membership. We recognize two species from the Bridgerian, P. longicaudus and P. natans. We consider P. elegans a junior synonym of P. longicaudus based on essentially identical size and dental morphology and include P. phocipes within P. natans based on the same criteria. Pantolestes intermedius is problematic, because the only known specimens are postcranial and pantolestids as a group show significant postcranial growth even after dental eruption is complete. However, its extremely reduced size relative to P. natans suggests that it is distinct from this species, and, although larger, it is closer in size to a referred specimen of P. longicaudus. We place all specimens of Uintan Pantolestes within either P. longicaudus or P. natans based on overall similarity in size and morphology. The postcranial remains of Uintan Pantolestes are fragmentary but show little morphological difference from earlier pantolestids. This suggests that Uintan pantolestids maintained an aquatic lifestyle despite the recession of ancient lakes in the continental interior occurring during that time. It is possible that the extreme rarity of Uintan pantolestids compared with earlier relatives is linked to the shrinking of aquatic habitats.

In contrast to the suction-feeding, predominantly teuthophagous extant sperm whale, several Miocene physeteroids display proportionally larger teeth, deeply embedded in both upper and lower jaws. Together with other osteological features, these differences lead to the functional interpretation of these taxa as macroraptorial predators, using their teeth to capture and process large marine vertebrates. However, the assumption that strong forces applied to macroraptorial physeteroid teeth during powerful bites and contacts with bone material should result in major dental damage has not yet been tested. In the present work, we analyzed a large collection of physeteroid teeth with an enameled crown from the Miocene of the North Sea Basin. We especially focused on a set of 45 teeth of Scaldicetus caretti discovered in Antwerp (Belgium, southern North Sea Basin) and tentatively dated to the Tortonian (early late Miocene). Visual inspection and computed tomography (CT) scans revealed dental damage, including wear and breaks. The latter could be interpreted as chipping fractures, occurring along the crown, and vertical root fractures, observed along the apical part of the massive root. Chipping fractures are most likely due to contacts with hard material, whereas vertical root fractures may result from the application of strong and repetitive bite forces and/or contacts with hard material. Such results further support the interpretation of a series of Miocene physeteroids with proportionally large teeth as macroraptorial (rather than suction-feeding) top predators. Considering the size of the teeth of S. caretti, its most likely prey items were other large marine vertebrates.

The uppermost Cretaceous (Maastrichtian) Hell Creek Formation in North America has yielded a diverse assemblage of fossil turtles dominated by baenids. A population of over 30 individual skeletons from the Hell Creek Formation of North Dakota comprises a new baenid turtle, Saxochelys gilberti, increasing the number of recognized Hell Creek turtles to at least 26, 11 of which are baenids. Saxochelys gilberti is differentiated from all other baenids based on the presence of a nuchal scale, finely sculptured shell, absence of an omega-shaped femoral-anal sulcus, presence of an omega-shaped extragular-humeral sulcus, a cavum tympani that is relatively smaller than the diameter of the orbit, presence of a robust single scale on the posteromedial portion of the parietals, and jugal exclusion from the orbital margin. Two distinct plastral morphologies, concave (N = 8) and flat (N = 9), are interpreted as representing male and female individuals, respectively. A ca. 10% size difference between the sexes indicates that S. gilberti is a sexually size-dimorphic turtle with larger females. This suggests female mate choice in this baenid turtle. A referred S. gilberti skeleton from above the Cretaceous–Paleogene boundary provides evidence for the survival of yet another species of turtle across this extinction event. The type locality of S. gilberti is close both stratigraphically and geographically to another locality consisting of a completely different assortment of baenid species, suggesting a fine degree of spatial niche partitioning in baenid turtles that may help explain the extremely high diversity of the group within the Hell Creek Formation.

A new specimen of Stenorhynchosaurus munoziPáramo-Fonseca et al., 2016 (Plesiosauria, Pliosauridae), found at Sáchica (Boyacá, Colombia) in upper Barremian beds of the Arcillolitas Abigarradas Member of the Paja Formation, is described herein. It consists of a complete skull and 10 cervical vertebrae of an adult individual and provides valuable new morphological information on the species: the presence of nasals covering a subsurface circular cavity where salt glands were probably lodged (new autapomorphy), the presence of a high sagittal crest on the parietal, a very elongated pineal foramen enclosed entirely within the parietals, and unfused neural arches in the cervical vertebrae. A phylogenetic analysis supports the inclusion of Stenorhynchosaurus munozi within the pliosaurid clade Brachaucheninae. A morphological comparison between the juvenile and adult stages of S. munozi shows that in the adult stage, the margins of the internal nares and the anterior part of the anterior interpterygoid vacuity are well ossified, the medial joints of the pterygoids and the mandibular symphysis are closed, and the atlas and the axis are fused, but the cervical neural arches remain unfused to the centra. The growth pattern of the skull dorsal bones differs from that of the palatal elements, but the relative distance between the external and internal nares remains the same. A greater longitudinal growth in the skull and a negative allometric orbital growth pattern results in a proportionally longer skull and relatively smaller orbits in the adult.

A new, diminutive species of dromaiine casuariid, Dromaius arleyekweke, is described from dispersed skeletal elements from the late Miocene Waite Formation of the Northern Territory, Australia. Remains of D. arleyekweke, sp. nov., have been found from the Ongeva Local Fauna in the Alcoota Scientific Reserve, but most remains come from the stratigraphically lower Alcoota Local Fauna where they form part of a densely fossiliferous series of mingled bone beds. Previously, remains of the new species had been referred to the basal dromaiine genus, Emuarius, but phylogenetic appraisal of new specimens indicates that the species shared a more recent common ancestor with the extant Dromaius novaehollandiae than it did with the type species of Emuarius, E. gidju. Consequently, the new species is placed in the genus Dromaius as its oldest known member. Derived characters of D. arleyekweke that are shared with D. novaehollandiae to the exclusion of E. gidju include a distally flattened external condyle of the distal end of the tibiotarsus and a more elongate tarsometatarsus, with marked transverse compression of the midshaft and a weakly impressed median sulcus on trochlea metatarsi II. Casuariid evolution shows a trend of increasingly cursorial hind limb proportions on the emu lineage, but D. arleyekweke has a tarsometatarsus that is more elongate than that of D. novaehollandiae. This implies nonlinear evolution of cursoriality in dromaiines and that D. arleyekweke evolved extreme cursorial proportions independently of D. novaehollandiae, or that a high degree of cursoriality evolved early in Dromaius and was reversed in the Pliocene D. ocypus.

Megaraptorid theropods thrived in South America and Australia during the mid-Cretaceous. Their Australian record is currently limited to the upper Barremian–lower Aptian upper Strzelecki Group and the upper Aptian–lower Albian Eumeralla Formation of Victoria, the Cenomanian Griman Creek Formation of New South Wales, and the Cenomanian–lowermost Turonian Winton Formation of Queensland. The latter has produced Australovenator wintonensis, the stratigraphically youngest and most complete Australian megaraptorid. The Eric the Red West (ETRW) site on Cape Otway, Victoria (Eumeralla Formation; lower Albian), has yielded two teeth, two manual unguals, and a right astragalus that are almost identical to the corresponding elements in Australovenator. Herein, we classify these as Megaraptoridae cf. Australovenator wintonensis. We also reappraise the ‘spinosaurid’ cervical vertebra from ETRW and suggest that it pertains to Megaraptoridae. Three other theropod elements from ETRW—a cervical rib (preserving a bite mark), a caudal vertebra, and a non-ungual manual phalanx—are also described, although it is not possible to determine their phylogenetic position more precisely than Tetanurae (non-Maniraptoriformes). All elements were found in a fluvial deposit, associated with isolated bones of other theropods, ornithopods, and turtles, amongst others; consequently, no two can be unequivocally assigned to the same theropod individual. The new specimens from ETRW demonstrate that a megaraptorid theropod morphologically similar to Australovenator lived during the late Early Cretaceous in Victoria, at a higher paleolatitude than its northern counterpart. Moreover, they attest to the success of megaraptorids in late Barremian–early Turonian faunas throughout eastern Australia.

An isolated dorsal osteoderm of a chroniosuchian from a late Permian fissure filling in the lower Zechstein (Z1) of central Germany represents the first Permian-age record of this enigmatic tetrapod clade outside Russia and China. Based on a number of features, the specimen is designated the holotype of a new taxon, Hassiacoscutum munki, and referred to the chroniosuchian clade Bystrowianidae. Phylogenetic analysis based on a recently published data set with addition of Hassiacoscutum and other recently described bystrowianids (Yumenerpeton, Jiyuanitectum, and Vyushkoviana) found good support for the clade Chroniosuchia and its subclades Chroniosuchidae and Bystrowianidae, but with little internal resolution for the latter. A second phylogenetic analysis of all known bystrowianid genera based solely on osteoderm characters yielded a well-supported and well-resolved clade Bystrowianidae with two subclades: (Yumenerpeton + (Synesuchus + Bystrowiella)) and (Jiyuanitectum + (Bystrowiana + (Hassiacoscutum + (Vyushkoviana + (Dromotectum + Axitectum))))). Hassiacoscutum provides a paleobiogeographic link to other middle and late Permian assemblages of Laurasian continental tetrapods. To date, chroniosuchians are known only from Laurasia, and their apparent absence in Gondwana hints at faunal provincialism across Pangaea.

Neuryurus is a Neogene–Quaternary glyptodont known heretofore only by dermal skeleton remains from Argentina, Uruguay, and Brazil. Herein, new material of Neuryurus is reported, including associated remains of carapace and endoskeletal bones, recorded from the Sopas Formation (late Pleistocene) of Uruguay. The material described here probably corresponds to an adult female associated with a neonate or an unborn individual. The studied endoskeletal bones allow us to extend the diagnosis of the genus, which shows morphological similarities to Panochthus, Neosclerocalyptus, and Hoplophorus. The body mass estimations obtained on the basis of the described material of Neuryurus suggest that it had a less robust constitution than other quaternary glyptodonts such as Glyptodon reticulatus, Panochthus tuberculatus, and Doedicurus clavicaudatus, for which estimates of more than 1,000 kg body mass were previously given.

Whereas aplodontiid rodents are represented today by a single living species, their fossil record is diverse in number of species (>100), in morphology, and in ecology. Recent phylogenetic efforts are beginning to make sense of the relationships among diverse members of the clade, but there is still much to learn about the relationships within the morphologically coherent subfamilies of this large group. The subfamily Aplodontiinae, including the extant Aplodontia, ranges from the mid-Miocene through recent, including only eight described species. This is the least diverse clade of aplodontiids, even though it is the only extant group. This study describes three new species, increasing the diversity of described fossil aplodontiids by more than a third. The description herein of Liodontia bathypotamos, n. sp., from the late Hemingfordian of Montana, Liodontia dailyi, n. sp., from the late Hemingfordian of Nevada, and Aplodontia minor, n. sp., from the late Hemphillian of Oregon extends the geographic and temporal range of the subfamily. A phylogenetic analysis of all known aplodontiines finds support for slow diversification and possible anagenetic change within lineages while also suggesting substantial missing time in the aplodontiine fossil record. However, the morphological changes, including rapid increases in hypsodonty, along the aplodontiine lineage yield an extant species, Aplodontia rufa, that, despite its early divergence from the rest of crown group Rodentia, is not at all representative of the ‘primitive’ rodent it is commonly assumed to be.

Three new euharamiyidan taxa are described based on isolated teeth from the Middle Jurassic (Bathonian) Itat Formation of the Berezovsk coal mine in Krasnoyarsk Territory, Western Siberia, Russia. The newly erected Sharypovoia, gen. nov., is referred to the Shenshouidae based on a premolariform p4, in which the main cusp and basined heel are surrounded by two rows of cusps. Attributed upper molars have the main labial cusps A1 and A2 connected by a ridge that lacks small additional cusps. In the smaller species S. arimasporum, sp. nov., there are one to two additional cusps mesial to cusp A2, whereas the larger S. magna, sp. nov., lacks these additional cusps. Maiopatagium sibiricum, sp. nov. (Euharamiyida incertae sedis), is similar to M. furculiferum from the Late Jurassic Yanliao Biota of northeastern China in having coalesced crest-like lingual cusps and an open occlusal furrow medially on the upper cheek teeth. Sineleutherus uyguricus from the Upper Jurassic (Oxfordian) Qigu Formation in Xinjiang, China, is restricted to the holotype only, a lower molar, and referred to the Arboroharamiyidae. The previously published sample of ‘Sineleutherus’ issedonicus from the Itat Formation represents a mixture of shenshouid and arboroharamiyid euharamiyidan taxa, and the holotype of that species, a lower molar, should be referred to a new genus of Arboroharamiyidae. The Asiatic euharamiyidan taxa are referable either to Shenshouidae or Arboroharamiyidae, but not to Eleutherodontidae.

A paleobiological reconstruction of the last hours of life of an exceptionally well-preserved fossil tadpole is carried out through morphological and taphonomic analyses, allowing inferences to be made about its identification, developmental stage, physical condition, health, behavior, death, and burial. The tadpole was recovered from an upper Miocene (Turolian, MN13) diatomaceous konservat-lagerstätte deposit near Tresjuncos (Cuenca Province, Spain). The specimen belongs to an unnamed species of Pelobates (Pelobatidae) of the westernmost Palearctic phylogenetic clade. Its gigantic size was due neither to metabolic (hypothyroidism) nor to ecological (overwintering) causes but merely reflects an optimum living environment. Dying at Gosner developmental stage 41, the ossification pattern of the tadpole is slightly discordant with that of extant Pelobates cultripes, a greater degree for the skull and vertebral column in the fossil. The tadpole, seemingly in excellent health, had an intestine containing abundant remains of an epiphytic/epipelic diatom, different from the planktonic species surrounding the fossilized body. Death was probably violent, as revealed by a fossil hollow trace similar to hematomas made by egret beak strikes. Rapid burial coincided with an occurrence of massive planktonic diatom sedimentation distant from the lakeshore.

A new specimen of Pucatherium parvum from the lower levels of the Upper Lumbrera Formation of Salta Province is reported. An almost complete dorsal carapace and several postcranial remains were preserved, providing important information about this particular taxon. The specimen is comparable in size to Dasypus novemcinctus, although the osteoderms are very small. The dorsal carapace seems to be completely integrated by movable osteoderms, providing a high degree of mobility in the anteroposterior axis. There is no evidence of pseudoshield, scapular shield, or pelvic shield. The dating of 39.9 ± 0.4 Ma (U-Pb zircon), taken from a tuff close to the top of the Upper Lumbrera Formation, allows us to refer this record of P. parvum to the middle Eocene (Bartonian). This, together with its broad geographic distribution, allows correlating the Upper Lumbrera Formation with the Quebrada de los Colorados Formation in Salta Province and with the Casa Grande Formation in Jujuy Province. On the other hand, the estimated depositional age of 37.3–35.4 Ma for the Geste Formation in Salta Province extends the biocron of P. parvum to the late Eocene.

Isolated astragali and calcanei of one of the smallest known living or extinct mammals, the geolabidid lipotyphlan Batodonoides powayensis, are identified and described from early and late Uintan (middle Eocene) strata in San Diego County, California. The morphology of the tarsus of Batodonoides appears to be most consistent with arboreal or scansorial locomotion. Prior assessments of geolabidid relationships have allied the group with lipotyphlans, particularly soricids and Solenodon, but the tarsus of Batodonoides shows no particular similarity to any extant lipotyphlan family. Instead, there are unexpected tarsal similarities to the extinct Nyctitheriidae, suggesting that geolabidids may have their origins among Paleocene and Eocene nyctitheres. Results of a phylogenetic analysis are consistent with a relationship either to Solenodon or to Nyctitheriidae. When geolabidids and nyctitheres are allied, the latter group shifts from the euarchontan stem to the lipotyphlan stem, potentially reconciling two divergent views on the relationships of nyctitheres. Batodonoides provides an additional example of the impact of nondental material in challenging established views of the affinities of early Cenozoic ‘insectivores.’

We describe a partial skeleton of the Late Cretaceous shark, Cretodus, collected from the Blue Hill Shale (middle Turonian) in north-central Kansas, U.S.A. It consists of 134 disarticulated teeth, 61 vertebrae, 23 placoid scales, and fragments of calcified cartilage. The scale morphology suggests that Cretodus was a rather sluggish shark, and the vertebral morphology affirms its placement into Lamniformes. With a strong tendency towards monognathic heterodonty, the dental morphology indicates that the specimen belongs to a new species, C. houghtonorum, sp. nov., increasing the total known species of Cretodus to five. The five species can be divided into three distinct groups: the longiplicatus/semiplicatus-grade, gigantea/houghtonorum-grade, and crassidens-grade. Cretodus, that successively evolved by broadening the tooth crown. The individual of C. houghtonorum, sp. nov., is estimated to be about 515 cm in total length (TL). Our vertebra-based growth analysis suggests that the shark was about 118 cm TL at birth and that the species had an estimated maximum growth length of 684 cm TL. The large size at birth indicates that the intrauterine cannibalism behavior of embryos seen in extant lamniforms had already evolved by the Late Cretaceous. Where C. houghtonorum, sp. nov., preferred nearshore environments, the specimen co-occurred with isolated teeth of Squalicorax and fragments of two dorsal fin spines of a hybodont shark, circumstantially indicating that the individual of Cretodus fed on the much smaller hybodont and was scavenged by Squalicorax.

The diversity reached by the mylodontids during the Pleistocene has been underestimated in the past. Oreomylodon wegneri, the endemic mylodontid of Ecuador, has been considered both a species of Glossotherium and a synonym of Glossotherium robustum. In this work, we provide a detailed description of abundant O. wegneri material and compare it with material of G. robustum from Argentina and other mylodontids. The study presented here shows that O. wegneri was a mylodontid with a singular cranial morphology, especially in the palate and nasal region and is possibly closer evolutionarily to Paramylodon harlani than to the more southern G. robustum.

The fossil record of the ichthyosaur genus Stenopterygius comprises a large number of specimens of all ontogenetic stages. This makes the taxon a good model for ontogenetic studies in a Mesozoic marine reptile. Here, we describe the morphology of the braincase elements of Stenopterygius over ontogeny and compare it with that of other known ichthyosaur braincases. Substantial ontogenetic changes were observed in most elements. These included negative allometry of the exoccipitals relative to the basioccipital, changes in the morphology of the parabasisphenoid and proportional reduction of the ridge separating the right and left internal carotid arteries, variable relative length of the paroccipital process of the opisthotic in juvenile specimens, and relative ossification of the basioccipital peg. Furthermore, we observed variability in relative braincase ossification between embryos within a single gravid female.

The fossil record of ‘phractocephaline' catfishes in South America is relatively rich. The extinct species Phractocephalus ivyAzpelicueta and Cione, 2016, was named on the basis of diverse material coming from late Miocene beds of Paraná City, Argentina. A review of the holotype specimen described by those authors allows us to recognize that the individual may be referred to the extant genus Steindachneridion; thus, we propose the new taxonomic combination Steindachneridion ivy. Furthermore, part of the material described by previous authors may be effectively included within Phractocephalus. In this sense, the finding of new specimens in paleontological collections allows us to refer all these specimens to a new, previously unrecognized Phractocephalus species. The fossil record of ‘phractocephalines’ in the Paraná paleobasin indicates that the area played an important role in the evolution of this clade of basal pimelodids.

The tetrapod trace fossil record of Australia has, until recently, been poorly studied relative to records on other continents. In the last few decades, a series of studies have revealed that these traces are more common than was previously thought. They have provided fossil evidence of taxa for which no skeletal fossils are known and have been found in areas of the country where no skeletal fossils occur. We describe a series of footprints from the Main Body Tirari Formation in the Lake Eyre Basin representing the first avian footprints published from the Australian Pliocene. Skeletal fossils from this member of the Tirari Formation are rare and are restricted to a few mammalian taxa. Three avian ichnotaxa are identified here, including Anatipeda alfi, Phoenicopterichnum isp., and Koreanaornis sirin (hamanensis), with several prints potentially belonging to a second species of Koreanaornis. We also clarify several contradictions relating to the relevant avian ichnotaxonomy and propose an unambiguous method for measuring digit divarication in avian footprints with curved digital traces. The footprints described here indicate that flamingos, a variety of waders, and swans or pelicans were present when the lacustrine sediments of the Main Body Tirari Formation were laid down. These prints highlight the potential for more trace fossils to be found in the region, from a time period poorly represented by body fossils.