Metoposaurids are a group of temnospondyl amphibians that filled crocodile-like predatory niches in fluvial and lacustrine environments during the Late Triassic. Metoposaurids are common in the Upper Triassic sediments of North Africa, Europe, India, and North America, but many questions about their systematics and phylogeny remain unresolved.We here erect Metoposaurus algarvensis, sp. nov., the first Metoposaurus species from the Iberian Peninsula, based on several new specimens from a Late Triassic bonebed in Algarve, southern Portugal. We describe the cranial and pectoral anatomy of M. algarvensis and compare it with other metoposaurids (particularly other specimens of Metoposaurus from Germany and Poland). We provide a revised diagnosis and species-level taxonomy for the genus Metoposaurus, which is currently represented with certainty by three European species (M. diagnosticus, M. krasiejowensis, M. algarvensis). We also identify cranial characters that differentiate these three species, and may have phylogenetic significance. These include features of the braincase and mandible, which indicate that metoposaurid skulls are more variable than previously thought. The new Portuguese bonebed provides further evidence that metoposaurids congregated in fluvial and lacustrine settings across their geographic range and often succumbed to mass death events. We provide an updated paleogeographic map depicting all known metoposaurid occurrences, which shows that these temnospondyls were globally distributed in low latitudes during the Late Triassic and had a similar, but not identical, paleogeographic range as phytosaurs.

Disarticulated elements in a large, uncompressed regurgitate from Tillywhandland Quarry (Lochkovian), as well as serial sections of an articulated specimen, reveal the three-dimensional shape and structure of fin spines, scapulocoracoid and dermal plates, and the histological structure of dermal and endoskeletal hard tissues of the climatiid acanthodian Climatius reticulatus. Globular calcified cartilage is the only form of mineralization of the head endoskeleton, with the jaws preserved as double-layered globular calcified cartilage. Tooth whorls are borne on both the upper and lower jaws and comprise a vascularized bone base and tooth cusps composed of a vascular network and mesodentine, without a central pulp cavity. The short admedian spine is the only strongly laterally compressed spine; the anterior dorsal fin spine has a wide, splayed base. No evidence was found of large dermal plates between the pectoral fin spine and the median lorical plates, with the prepectoral pinnal plates with spines being the only large paired dermal components of the shoulder girdle. The anterior lorical plate, pinnal plates, and tesserae on the scapulocoracoid bear ornament comparable to the postbranchial apronic ornament in acanthothoracid placoderms. Branchiostegal plates have a thin, dense inner bone layer and an outer dentinous ornament layer but lack a middle osteodentine layer; other postcranial plates and fin spines have a smoothsurfaced inner layer of bone and a thick middle osteodentine layer. Body scales have a crown with areal growth zones formed of Stranggewebe and syncitial mesodentine on a cellular bone base.

A new aulopiform, Ursichthys longiparietalis, gen. et sp. nov., preserved within and around the body cavity of a mosasaur, Mosasaurus missouriensis, is described from the Bearpaw Formation (upper Campanian, ca. 74.8 Ma) of Alberta, Canada (paleolatitude = 57°N). The partial skeleton consists of a partial skull associated with other isolated bones, including parasphenoid, hyomandibula, cleithrum, caudal peduncle centrum, scale, and many disarticulated fin rays. Many of those elements show evidence of bite damage considered to have been inflicted by the mosasaur. This taxon can be differentiated from other aulopiforms in having a dorsoventrally compressed neurocranium; short frontals; large, long, rectangular parietals that contact at the midline and are situated anterior to the supraoccipital; triangular epiotics, with the facet for the dorsal arm of posttemporal centered over the epiotic; hyomandibula head articulating anteriorly with only the pterotic and sphenotic; cleithrum with a long, narrow, straight vertical shaft; mesacoracoid present; and centra with two lateral, elongate fossa. Total length is estimated at 100 cm and age is estimated at 7 years old. We also emend the diagnosis for Apateodus to include more cranial characteristics. Among 37 known genera of Cretaceous aulopiforms, the diversity at the K-Pg boundary is probably underrepresented. Fish skeletons have rarely been recovered from the Bearpaw Formation in Alberta, likely due to a preservational bias. This report, however, shows promise for additional fish material preserved in mosasaur skeletons because they are relatively more commonly preserved than fish skeletons.

Dietary analyses of herbivorous mammals are important for paleoecological reconstruction. Several methods applicable to fossil teeth have been developed lately. The mesowear method based on wear-induced occlusal shape and relief of ungulate molars has proven to be a robust method for dietary analysis. In its original form it can only be used for selenodont, plagiolophodont, and ectolophodont ungulate molars, but the principle can be extended to other kinds of tooth morphology. We introduce a new method of dietary analysis for proboscideans similar to the mesowear method, based on angle measurements from worn dentin valleys reflecting the relief of enamel ridges. The enamel ridges should be heavily worn when the abrasiveness of diet increases, resulting in lower occlusal relief and larger angles. For testing this, we compared the mesowear angles with stable carbon isotope values from dental enamel from populations of extant and fossil species from localities from Kenya and India. This enables us to compare diet and tooth wear in proboscideans, because the stable carbon isotope ratios in tropical environments provide a reliable standard for assessing the relative amounts of C4 and C3 plants in diet, and most of the C4 plants are grasses, which should be reflected in the mesowear signal.

The genus Mirounga is the largest living member of the Phocidae family (true seals) and includes two species: M. angustirostris and M. leonina. These species exhibit a noticeable antitropical distribution in the Northern and Southern hemispheres, respectively. The evolutionary history of elephant seals, especially in regard to establishing this antitropical pattern, is poorly known. Nearly all fossils of the genus are isolated remains from the Pleistocene of California (M. angustirostris) and South Africa (M. leonina). Here, we describe new fossil material of Mirounga sp. (incomplete maxilla, dentary, and humerus), from the middle to late Pleistocene of Antofagasta Region, northern Chile. This material constitutes the first fossil occurrence of this species in South America and suggests that during part of the Pleistocene, phocids coexisted with otariids along the eastern edge of the South Pacific Ocean, which contrasts with the current biogeographic pattern in this ocean basin, providing new information about the structure of the pinniped community during the Pleistocene of South America.

Captorhinids are inherently interesting Paleozoic reptiles because they include the first terrestrial vertebrates to have multiple tooth rows on the maxilla and dentary. This may have been a key innovation that allowed captorhinids to diversify and disperse throughout the Permian Period of Pangea. We provide the first comparison of tooth development in captorhinids to determine how multiple rows of marginal teeth evolved within this clade. By comparing thin sections of multiple-rowed Captorhinus aguti from the Lower Permian of Oklahoma with the contemporaneous, single-rowed Captorhinus magnus, we provide evidence for variation in jaw growth, which establishes the number of tooth rows. Comparisons with the basal captorhinid Concordia cunninghami from the Upper Carboniferous of Kansas demonstrate that early captorhinids retained the typical amniote condition of replacing teeth in a manner similar to modern iguanian lizards. By comparing tooth development in C. aguti with other single-rowed captorhinids, we also demonstrate that the shedding of old teeth and the development of new teeth are not linked developmental processes in captorhinids. Instead, the fates of older generations of teeth are entirely dependent on their proximity to the lingual surface of the dentary where the toothproducing organ, the dental lamina, would have been present. These peculiar features of the dentitions of captorhinids make them model taxa for examining patterns of tooth development and replacement.

We report a diverse assemblage of tribosphenidan mammals from several localities in the Cloverly Formation (Lower Cretaceous, Albian) of Montana and Wyoming. This unit is of historical significance for yielding well-known dinosaurs (e.g., Deinonychus antirrhopus, Tenontosaurus tilletti) and early mammals (e.g., Gobiconodon ostromi, Montanalestes keeblerorum). We provisionally identify 13 taxa (five of which are formally recognized), including Pappotherium pattersoni, a new species of the deltatheroidan Oklatheridium (O. wiblei, sp. nov.), a eutherian (Montanalestes, previously named), and two new basal tribosphenidans (Argaliatherium robustum, gen. et sp. nov., and Carinalestes murensis, gen. et sp. nov.). An unnamed taxon, represented by associated but almost edentulous dentaries, is interpreted to have had four incisors, a single-rooted canine, three premolars, and four molars, indicating that the metatherian tooth formula was established by the Albian. In addition, an indeterminate lower molar fragment preserving twinned talonid cusps and a buccal postcingulid provides the earliest evidence for Marsupialiformes. We also provide a more detailed description of the associated dentaries (holotype) of Montanalestes keeblerorum. The mammalian fauna from the Cloverly Formation shares several taxa with the roughly contemporaneous Trinity Group of Oklahoma and Texas, an observation that also applies to the dinosaur fauna, suggesting some degree of latitudinal homogeneity among described terrestrial vertebrates in this part of the North American Early Cretaceous.

MOR 1062 is a plioplatecarpine mosasaur that is represented by a nearly complete skull, complete cervical series, and partial dorsal vertebral column. The specimen, collected from Upper Cretaceous (Campanian) deposits of northeast Montana, exhibits a pristine level of preservation, yielding morphological details not typically observed. Phylogenetic analysis recovers MOR 1062 within an unresolved trichotomy with Plioplatecarpus marshi and P. houzeaui. However, based on the following autapomorphies, a new taxon, Plioplatecarpus peckensis, sp. nov., is erected to accommodate this suite of features exhibited by MOR 1062: a narrow, elongate prenarial portion of the premaxilla that is constricted at midlength; a maxilla with a nearly straight narial margin in lateral view; a short prefrontal lamina of maxilla that contributes to a very low profile of the snout immediately anterior to orbits; a suspensorial ramus of parietal that does not rotate into horizontal plane distally; nine or 10 pterygoid teeth; an otosphenoidal crest that covers the exit for cranial nerve VII in lateral view; jugular and condylar (= hypoglossal) foramina that exit separately; axial spine with a distinctly notched dorsal border; hypapophyseal peduncles on postcranial vertebrae 2–7; and hypapophyses 2–5 bearing paired, anteriorly projecting knobs.

Bonitasaura salgadoi, from the Bajo de la Carpa Formation (Santonian), Río Negro, Argentina, is a wellpreserved titanosaur. Previously described cranial material of Bonitasaura demonstrated the presence of square jaws in titanosaurs, but the nearly complete postcranium of the holotype specimen remains mostly undescribed. We present an osteological description of this material, which includes cervical, dorsal, and caudal vertebrae, elements of the pectoral and pelvic girdles, as well as forelimbs and hind limbs. Characteristics of the axial skeleton suggest that the holotype represents an immature individual. The base of the neck was likely robust, based on the broad, rhomboidal neural spines in the vertebrae across the cervicodorsal transition. Bonitasaura is assigned to Titanosauria based on lateral constriction of the neural canal in the anterior cervical vertebrae, presence of anterior and posterior spinodiapophyseal laminae in the middle to posterior dorsal vertebrae, distolateral expansions of the middle dorsal vertebral neural spines, absence of hyposphene-hypantrum articulations in posterior dorsal vertebrae, anterior and middle caudal vertebrae with strongly procoelous centra, anterior caudal vertebrae with transverse processes extending beyond the posterior margin of the centrum, and other axial features. The appendicular anatomy of Bonitasaura also supports referral to Titanosauria based on characters such as the semilunar sternal plates, flat and rugose distal surfaces of the metacarpals, medial curvature of the proximal femur, posterior shallow fossa of the astagalus undivided, and mediolaterally expanded distal tibia. The gracile long bones further support placement within non-saltasaurine titanosaurs. Bonitasaura provides additional osteological data that will contribute to a better resolution of titanosaur phylogeny.

The teleosts of the Late Jurassic Almada Fauna (Cañadón Calcáreo Formation) from Patagonia have been known for decades, but their taxonomic assignment has remained problematic. Two teleost species were thought to be represented in these lacustrine deposits: †‘Tharrhias' feruglioi and †Luisiella inexcutata. In recent years, numerous complete and excellently preserved specimens have been collected, justifying revision of all available material. After a detailed anatomical study, we conclude that only one species of teleost is present in this fauna. †‘Tharrhias' feruglioi and †L. inexcutata are synonyms and represent a single species, and due to the erroneous referral to the genus †Tharrhias, which designates a different fish, the new combination †Luisiella feruglioi is proposed. This study has revealed great morphological variability, which can be explained as intraspecific variability (ontogenetic and individual) as discussed herein. The overall morphology of †L. feruglioi resembles that of basal teleosts. In particular, †L. feruglioi is intriguingly similar to †Cavenderichthys talbragarensis from the continental Late Jurassic Talbragar Beds in Australia, owing to the presence of features not commonly found in known basal teleosts (hyomandibular bone with preopercular process, lower jaw with deep coronoid process and lacking a ‘leptolepid' notch in the dentary, and first uroneural anteriorly reaching the second preural centrum) and probably derived features such as a preopercular canal with few simple tubules. The resemblance between the Almada and Talbragar faunas has been recently proposed in reference to the coccolepidid species present in both Gondwanan faunas and is here discussed regarding the anatomical similarities shown by teleosts.

Here we describe the first known skull and associated postcrania of the small bothriodontine anthracotheriid Sivameryx africanus, which fills an important gap in the current knowledge of morphological diversity within the Anthracotheriidae of Africa. The skull was recovered from the latest early Miocene sediments of the Kalodirr Member in the Turkana Basin of Northern Kenya, and the age is well constrained between two tephra dated to 17.5 ± 0.2 and 16.8 ± 0.2 Ma. A partial mandible of Sivameryx from Kalodirr is also described because it may belong to the same individual. The new anatomical data were incorporated into a genus-level phylogenetic analysis of Bothriodontinae that reveals that Sivameryx is the sister taxon to Hemimeryx and belongs to a clade of advanced bothriodontine anthracotheriids alongside the genera Merycopotamus, Libycosaurus, and Afromeryx. The new material of Sivameryx from Kalodirr greatly expands our knowledge of the cranial anatomy of the genus, because the skull of Sivameryx does not reveal any specializations for aquatic habitats, such as those seen in Libycosaurus. Here we suggest, based on the preserved cranial and postcranial evidence, that Sivameryx may have been a small browser that inhabited denser stands of vegetation at Kalodirr based on evidence from its narrow snout and well-developed labial musculature. However, its masticatory muscles were also relatively well developed, suggesting repetitive loading of the jaw when chewing tough vegetation.

Three new species of anthracotheres (one Anthracokeryx and two Bothriogenys) are described from the Na Duong coal deposits in northeastern Vietnam. These are the first representatives of the genera ever recorded from Vietnam, and they are morphologically close to species known in China, Thailand, Myanmar, and Egypt (Fayum). The material recently described from Na Duong is probably misattributed to Bakalovia and likely belongs to Elomeryx. The association in Na Duong of the three new species suggests an early late Eocene to middle late Eocene age for the fossiliferous sediments, which corresponds to a somewhat more precise and restricted time interval than the latest middle to early late Eocene age recently proposed. This also demonstrates that faunal exchanges were possible throughout South Asia and likely between South Asia and Africa during the Eocene period, and it questions the Miocene time of origination of the Na Duong Basin suggested by geological data.

A new species of cyclotosaurid amphibian, Eocyclotosaurus appetolatus, is based on excellent, three-dimensionally preserved material from New Mexico Museum of Natural History locality 5193 in the Middle Triassic (Perovkan) Anton Chico Member of the Moenkopi Formation near Tecolotito, New Mexico, U.S.A. The locality is a monodominant bonebed, with E. appetolatus representing the vast majority of the fossil material. E. appetolatus shares a long, narrow snout and slightly concave lateral skull margin with other members of the genus, but differs from all others in that the skull is relatively narrower at its widest point and the orbits are larger, more elliptical, and placed more anteriorly. The snout is relatively broader and more robust, the choana shorter and more rounded, and the palatal tusks are proportionately larger than in other species. Premaxillary apertures, larger than those of E. woschmidti, penetrate the skull roof anterior to and separate from the external nares. E. appetolatus forms the sister taxon of the more gracile E. wellesi from Arizona, with which it shares the wide separation of postorbital and prefrontal. The size range of material from the locality is represented by skulls 227–472 mm in midline length. Preliminary allometric study indicates that the preorbital snout grows relatively longer and the orbits migrate posteriorly throughout ontogeny. The snout is relatively slender in young animals and grows wider and more robust throughout life. Application of beam mechanics shows mediolateral strengthening of the anterior teeth, which probably implies a preference for side-strike prey capture.

Coelacanths form a clade of sarcopterygian fishes (lobe-finned vertebrates) that today is represented by a single genus, Latimeria. This genus belongs to a lineage of marine coelacanths, the latimeriids, whose fossils are common in the Jurassic and the Cretaceous deposits of Europe and North America. During the same periods, another lineage of fresh/ brackish water coelacanths, the mawsoniids, occurred in South America, Africa, and Madagascar. Mawsoniids are supposed to have originated during the Triassic in North America and were assumed to have subsequently dispersed to South America during the Jurassic, before reaching western Africa during the Early Cretaceous. Previous hypotheses advocated that mawsoniid coelacanths reached Europe during the Late Cretaceous, suggesting the dispersal of freshwater organisms from Africa to Europe during this period. We here reevaluate this scenario based on the reexamination of the coelacanth Trachymetopon from the Early Jurassic of Germany. Although this genus is known from remarkably well-preserved material, its relationships to other Mesozoic coelacanths remained unsolved. An anatomical investigation shows that Trachymetopon shares many common features with the Late Jurassic—Late Cretaceous mawsoniids Mawsonia and Axelrodichthys from western Gondwana, such as the absence of a descending process of the supratemporal, the presence of ossified ribs, and the skull roof and cheek bones ornamented by conspicuous coarse rugosities and ridges. A phylogenetic analysis of morphological characters places Trachymetopon within Mawsoniidae. We suggest that mawsoniid coelacanths were already present in Europe from the Early Jurassic onwards, challenging previous paleobiogeographic scenarios.

Plesiorycteropus (Malagasy aardvarks) is the sole genus belonging to an extinct mammalian order, the Bibymalagasia, that lived in Madagascar in the Quaternary. Its systematic and phylogenetic position is controversial because Plesiorycteropus morphologically resembles aardvarks (Tubulidentata), whereas a recent molecular analysis proposed that it belongs to Tenrecoidea, along with Tenrecidae (tenrecs and otter shrews) and Chrysochloridae (golden moles). This context of competing phylogenetic hypotheses is stimulating for the investigation of new characters for phylogenetic inferences. Here we used the noninvasive methods of micro-computed tomography scanning, digital reconstruction, and three-dimensional geometric-morphometric analysis of shape to investigate the morphology of the bony labyrinth (osseous inner ear) of the holotype skulls of both known species of Bibymalagasia: Plesiorycteropus madagascariensis and P. germainepetterae. Firstly, by comparisons with their extant relatives, we find that the characters of the bony labyrinth that distinguish P. madagascariensis and P. germainepetterae could only represent intraspecific variation. Secondly, we find that the bony labyrinth of Bibymalagasia is distinctive from those of other Afrotherians examined, supporting their ordinal distinctiveness. Indeed, the principal component analysis on labyrinthine shape data shows that the bony labyrinths of both Plesiorycteropus species are in fact intermediate between those of tubulidentates and other Afrotherian insectivores. Finally, we investigated the evolution of the secondary common crus (partial fusion of the lateral and posterior semicircular canals) in Afrotherians and found that this character is present in tubulidentates and potamogaline tenrecs, supporting the hypothesis that its presence is primitive for Afrotherians. In contrast, Plesiorycteropus displays the derived condition (i.e., loss of the secondary common crus).

A large traversodontid cynodont Ruberodon roychowdhurii, gen et. sp. nov., is described from the Late Triassic Tiki Formation of the Rewa Gondwana Basin, India, based on an ontogenetic series of five partial lower jaws. Ruberodon is characterized by a robust and deep dentary symphysis, lower dental formula of i3-c1-pc9, procumbent and hypertrophied first lower incisor, a large canine, long diastema between the lower canine and first postcanine, and a high coronoid process at 60° to the horizontal tooth row. With growth, the symphyseal region became relatively more slender with lengthening of the diastema. Phylogenetic analysis based on 19 taxa and 35 craniodental characters places Ruberodon within the clade containing Gomphodontosuchus, Menadon, Protuberum, Scalenodontoides, and the multispecific Exaeretodon. The new genus forms a sister taxon to E. statisticae and is more advanced than E. riograndensis and E. argentinus based on the presence of a strong coronoid ridge anterior to the masseteric fossa. Based on its tetrapod assemblage, the Tiki Formation may be globally correlated with other formations such as the lower part of the Maleri Formation of India, the Isalo II Beds of Madagascar, and the upper part of the Santa Maria Formation of Brazil. An early Carnian age is proposed for the Tiki Formation.

A new elasmosaurid, Vegasaurus molyi, gen. et sp. nov., from Vega Island, James Ross Archipelago, Antarctica, is described. The holotype and only specimen of this species (MLP 93-I-5-1) was collected from the lower Maastrichtian Cape Lamb Member of the Snow Hill Island Formation. Vegasaurus molyi is the only Antarctic elasmosaurid and one of only a few Late Cretaceous elasmosaurids from the Southern Hemisphere whose postcranial anatomy is well known. Vegasaurus molyi is distinguished from other elasmosaurids by the following combination of characters: cervical region with 54 vertebrae with elongated centra, dumbbell-shaped articular faces and lateral ridge present in the anterior and middle parts of the neck but absent in the posterior-most cervical vertebrae; scapula with ventral ramus bearing a strong ridge in the anteromedial corner of its dorsal surface; ilium shaft with expanded distal end, divided into two parts forming an angle of 140° opening anteriorly; and humerus with anterior knee and prominent posterior projection with accessory posterior articular facet. Preliminary phylogenetic analysis places V. molyi within a clade that includes the Late Cretaceous Wedellian aristonectine elasmosaurids, Aristonectes and Kaiwhekea. This indicates a close relationship between Aristonectinae and non-Aristonectinae Late Cretaceous Weddellian elasmosaurids and suggests a Weddellian origin for the Aristonectinae.

Whereas ‘biological site fidelity’ refers to the regular reuse of a favored locale (e.g., breeding ground or nest) by an individual animal, ‘paleontological site fidelity’ typically refers to repeated use of a nesting locality by a herd or species over geologic time scales. Two new Cretaceous specimens from the Two Medicine Formation of Montana, U.S.A., and the Liantoutang Formation of Zhejiang, China, each preserve two closely superimposed clutches of the egg form Prismatoolithus. These eggs belong to the Troodontidae, small theropod dinosaurs sharing a close ancestry with Aves. In both specimens, eggs of a lower clutch are truncated at a level below what would normally preserve in an undisturbed hatched clutch. These traces differ from past examples of dinosaur site fidelity in (1) the close or cross-cutting relationship of the clutches, (2) the precise overlay of clutch atop clutch, and (3) the implication of nest reuse and, thus, site fidelity on an ecologic rather than geologic scale and at approximately the individual rather than species level. Given the likely extended occupation of troodontid nesting sites by attending adults, factors such as nesting success and territoriality may, in addition to favorable substrates, have influenced the behaviors recorded by these specimens. The arrangements of eggs as clutches within the geologic record represent trace fossils. Thus, they record past in situ behavior, providing important insight into dinosaur nesting. In addition, they can serve as independent indicators of substrate conditions and sedimentary history, potentially refining our understanding of paleoenvironments.