Milosaurus mccordi was described in 1970 as a large, pelycosaurian-grade synapsid from the latest Carboniferous of Illinois but has since received little attention. Here, the holotype and referred material of Milosaurus are reexamined and incorporated into a phylogenetic analysis. Milosaurus is resolved within Haptodontiformes, sharing with this clade a posterodorsally expanded ischium and a calcaneum with greater length than width. The more plesiomorphic ischium indicates a basal position within this clade. Most of the referred material shows very little overlap with the holotype and so most was not included in the cladistic analysis. However, what was originally described as a dorsal rib is here judged to be a femur that shares a highly distinctive morphology with the holotype. With its mass estimated as 41 kg, Milosaurus represents one of the largest Carboniferous synapsids. Large size evolved at least twice independently in Haptodontiformes during the Pennsylvanian: once in Sphenacodontidae and once in Edaphosauridae. Using phylogenetic comparative methods, Milosaurus is found to have evolved a large size independently of these two clades. As one of the largest Carboniferous amniotes, and the outgroup to one of the most diverse Paleozoic synapsid lineages, Milosaurus represents a crucial taxon for understanding early terrestrial ecosystems.

The Proteidae represent a small group of perennibranchiate salamanders with a disjunct distribution in North America and southeastern Europe. Herein, we describe a new species of proteid salamander from the early Oligocene of Romania representing the geologically oldest member reported from the Cenozoic of Eurasia. Mioproteus gardneri, sp. nov., based on features of the vomers, dentaries, atlas, and vertebrae, appears to be closely allied with M. caucasicus and M. wezei, standing altogether as the sister group of Proteus, the only living European proteid. The apomorphies of the European clade, shared with the American members Necturus and Paranecturus, include the presence of dorsoventrally flattened anterior cotyles and alar-like processes, whereas a few other characters appear to be more derived in the European forms, such as the diverging anterior cotyles of the atlas enclosing an angle of 225°, the trunk vertebrae with strongly bifurcated neural spines, and unicipitate transverse processes. Peculiarly, the proteid remains from the early Oligocene locality of Suceag 1, Romania, were accompanied by the palaeobatrachid frog Albionbatrachus, a form closely linked to aquatic environments and having a limited fossil record in the Paleogene (upper Eocene of southern England, lower Oligocene of Romania, and upper Oligocene of Germany), suggesting that these fully aquatic groups probably used similar freshwater corridors to reach more southerly European territories.

Eorubeta nevadensis was originally based on a poorly preserved specimen from a well core in Member B of the Late Cretaceous–Eocene Sheep Pass Formation, White Pine County, Nevada. Originally thought to be a member of Leptodactylidae, E. nevadensis was later determined to have uncertain affinities with other anurans. Additional specimens of E. nevadensis recently collected from the outcrop from Members B and C of the Sheep Pass Formation in the Sheep Pass Canyon area, White Pine County, fill many gaps in knowledge about this poorly understood anuran. The new information allows for the first time a phylogenetic analysis of Eorubeta using parsimony. This analysis places E. nevadensis as the sister taxon of Acosmanura. Eorubeta nevadensis was originally reported as early Eocene but is now considered to be ?latest Cretaceous–Paleocene, based on invertebrates and pollen. Thus, although it is uncertain if E. nevadensis spans the Cretaceous–Paleogene boundary, it was at least part of the recovery fauna. The anuran fossil record from this time interval in North America is based on very fragmentary material of mostly uncertain relationships, making E. nevadensis the only nearly complete, well-preserved anuran fossil known. Eorubeta nevadensis, one of the larger fossil anurans recorded, is remarkable for being the only fossil anuran documented from a high-elevation environment, which has been compared to the modern Puna-Altiplano or the Tibetan Plateau.

Hispaniola once had a large and diverse endemic rodent community. Today, a single species, Plagiodontia aedium, survives alongside invasive murids. Ecological adaptations and resource competition among species have not been previously studied. Here, we undertake the first investigation of the foraging ecology of the endemic taxa using estimated body mass and carbon and oxygen isotope values in incisor enamel. Our sample includes nine endemic taxa, eight of which are extinct, from two Holocene cave assemblages in southern Haiti. We also measured isotopic signatures for the invasive genus Rattus to explore potential niche overlap and competition between introduced and endemic fauna. We expected to detect isotopic evidence for niche partitioning among phylogenetically related rodents with similar morphological adaptations. We find clear differences in body mass and isotope values among rodent taxa. The combination of carbon and oxygen isotopes suggests that some taxa lived in the forest understory, whereas others likely frequented the canopy or open habitats. We may also be able to distinguish dietary preferences (e.g., folivory, frugivory, and potentially trophic omnivory). Small individuals attributed to an undescribed species of Isolobodon are isotopically distinct from their congeners, I. montanus and I. portoricensis, and appear to have relied to a modest degree on C₄ foods. Rattus had a broad generalist niche, which coincided with several endemics, including extant P. aedium. Although preliminary, these data shed light on how a closely related community of island rodents partitions resources and provide context for understanding the ecological role that invasive species may play in extinction processes and future conservation efforts.

We here report on the smallest-known, neonate-sized Tylosaurus specimen, FHSM VP-14845, recovered from the lower Santonian portion of the Niobrara Chalk exposed in Kansas, U.S.A. Lacking any associated adult-sized material, FHSM VP-14845 comprises fragmentary and associated cranial bones, here considered to represent a single neonatal individual with an estimated skull length of 30 cm. Despite its small size, a suite of cranial characters diagnoses FHSM VP-14845 as a species of Tylosaurus, including the elongate basisphenoid morphology. At the same time, FHSM VP-14845 unexpectedly lacks a conical predental rostrum on the premaxilla, generally regarded as diagnostic of this genus. Further, the first and the second premaxillary teeth are closely spaced, with the second set positioned posterolateral to the first, contributing to the overall shortness of the dentigerous premaxilla. Because a conical predental rostrum is already present in ontogenetically young specimens of T. nepaeolicus and T. proriger with respective skull lengths of approximately 40 and 60 cm, formation of such a rostrum must have taken place very early in postnatal ontogeny. Our recognition of a neonate-sized Tylosaurus specimen without an elongate predental rostrum of the premaxilla suggests hypermorphosis as a likely heterochronic process behind the evolution of this iconic tylosaurine feature.

The complete mandible of the brachauchenine thalassophonean pliosaurid Kronosaurus queenslandicus Longman, 1924, is described for the first time from specimen KK F0630, discovered from the late Albian Allaru Mudstone, Rolling Downs Group, near Julia Creek, northwest Queensland. Previously undescribed anatomy results in several new features used to diagnose the taxon, including a mandibular symphysis exhibiting lateral embayments to accommodate overhanging premaxillary fangs and severe postsymphysis dentary constriction carrying embayments to accommodate large overhanging maxillary fangs. The presence of these embayments in specific areas on the lateral surface of the dentary and medial surface of the coronoid is a reflection of strongly developed anisodont dentition. The extension of a ventral dentary lamina posterior to a dorsal dentary lamina on the posterior margin of the dentary may represent a new character differentiating K. queenslandicus from K. boyacensis. Several differences are present between the mandible of KK F0630 and a previous composite reconstruction of the mandible of K. queenslandicus. The presence of six and a half pairs of functional alveoli within the mandibular symphysis in KK F0630 refutes prior research suggesting that K. queenslandicus bore three to four pairs of functional alveoli within the mandibular symphysis. A pathology exhibiting elongate grooves on the ventral surface of the right dentary is interpreted as a healed injury inflicted from the bite of a cretoxyrhinid lamniform shark. The discovery of KK F0630 further supports the notion that the late Albian Toolebuc Formation and Allaru Mudstone share similar fossil faunas.

Postcranial anatomical studies on non-mammaliaform cynodonts are essential for understanding postural and locomotor advances in mammalian evolution and provide information about the transition from the sprawling posture of basal synapsids to a more erect posture. Nevertheless, the number of functional analyses of this group remains small because little postcranial material has been discovered and the articular surfaces of bones are rarely preserved. Here, we present a detailed description of the postcranial skeleton of Prozostrodon brasiliensis (Probainognathia, Prozostrodontia), a non-mammaliaform cynodont from the Upper Triassic of Brazil (Hyperodapedon Assemblage Zone, Candelária Sequence), closely related to Mammaliaformes. The study adds new information on postcranial morphology, and functional implications are investigated. Prozostrodon brasiliensis had a semisprawling forelimb and a more therian-like erect hind limb. These results confirm that the evolution of an erect posture and a new muscular orientation of the hind limb occurred within Cynodontia before the appearance of the clade Mammaliaformes.

Herein, we describe a new early Miocene dugongine from marine deposits of the Culebra Cut (Gaillard Cut) of the Panama Canal. The new taxon, Culebratherium alemani, gen. et sp. nov., represents one of the few records of late Aquitanian–early Burdigalian sirenians and the oldest sirenian from Central America. A phylogenetic analysis places Culebratherium in a clade with Dioplotherium cf. D. allisoni (Miocene of Brazil), Dioplotherium allisoni (Miocene of Baja California Sur, Mexico, and California, U.S.A.), and Dioplotherium sp. (Pliocene of Yucatan, Mexico). Similar to these taxa, Culebratherium is characterized by the presence of large incisor tusks, a premaxillary symphysis without a boss, a premaxilla-frontal suture forming a butt joint, and a moderately downturned rostrum. In addition, Culebratherium exhibits prominent occipital-cervical attachment sites for enlarged neck musculature. These features taken together are interpreted as adaptations for uprooting large, deeply buried seagrass rhizomes. Other dugongines with similar, yet convergent, dental and facial adaptations are known from earlier or coeval deposits in Puerto Rico, Florida, South Carolina, California, Baja California Sur, Brazil, and India and were constituents of sympatric paleocommunities of sirenians. Only fragmentary evidence of a second smaller and unidentifiable sirenian species is known from the Culebra Formation, but future discoveries may reveal a similar sympatric paleocommunity during the early Miocene of Panama. Finally, we used the results of the phylogenetic analysis to propose the new clade Pan-Sirenia as the most inclusive group consisting of stem and crown groups and redefine the Sirenia, Dugongidae, and Dugonginae clades.

Fishes of the family Scopelarchidae, commonly known as pearleyes, are basal alepisauroids that occur worldwide at depths between 300 and 1,000 m. A new pearleye species, Benthalbella praecessor, sp. nov., is described from the middle Miocene (late Langhian–early Serravallian; 14.6–13.1 Ma) deposits of the Kurasi Formation, Sakhalin Island, Russia, based on 24 well-preserved specimens. These specimens consist primarily of articulated skeletons and represent the first fossil skeletal remains for the family Scopelarchidae. Benthalbella praecessor appears to be closely related to the extant B. dentata and is characterized by a unique combination of morphological and meristic features, including 54–56 vertebrae, dorsal fin with 8–9 rays, anal fin with about 19–22 rays, very short pectoral fin containing 26–28 rays, elongate pelvic fin, enlarged second infraorbital, subopercle larger than the opercle, and urohyal with a posterodorsally directed hook-like process along its anterodorsal margin. Paleoecological considerations suggest that Benthalbella praecessor was a deep-sea fish that inhabited the cold-temperate waters of the northwestern Pacific about 14 Ma.

Forelimb posture in sauropod dinosaurs is still poorly understood. Although a laterally directed (semisupinated) manus is the plesiomorphic condition in sauropodomorphs, the sauropod track record prevailingly shows anterolateral to anterior manus orientations, suggesting a high degree of manus pronation. The ?Middle Jurassic Tafaytour tracksites described herein preserve at least 10 trackways, nine of which show laterally oriented, and in two examples even posterolaterally oriented, manual impressions. Located in the Argana Basin of the Western High Atlas, Morocco, the tracksite yields hundreds of footprints on a highly bioturbated surface, including examples with well-preserved digit and claw impressions. Footprint morphology and trackway configuration vary greatly between trackways. A literature review indicates that laterally directed manual impressions are restricted to small- and medium-sized trackmakers. Statistical analysis was performed on a larger sample (n = 79) of small sauropod trackways from around the world, indicating that lateral manual orientations are correlated with low locomotion speeds and narrow trackway gauges. Manus pronation in sauropods is hypothesized to occur when the forelimb is actively contributing to the propulsion of the animal, which would be the case at faster speeds or at wider trackway gauges where the center of mass is located more anteriorly. We present new approaches to the quantitative analysis of trackway data. Mean configuration plots allow for direct graphical comparisons of different trackways. Two types of trackway asymmetries are defined and quantified. The apparent glenoacetabular distance (GAD) represents a feasible proxy for body size, at least for the smaller sauropod trackmakers analyzed herein.

A new species of redfieldiiform fishes, Lasalichthys otischalkensis, sp. nov., is described based on new, threedimensionally preserved specimens from the Upper Triassic Dockum Group of Howard County, western Texas. Lasalichthys otischalkensis is diagnosed by a combination of unique traits found in the skull, including shape of maxilla, shape of preoperculum and associated cheek bones, pattern and articulation of bones in the snout, and patterns of sensory line canals in the dermal skull bones. Specimens of this new species display novel patterns in the sensory line canals of the skull that have never been observed in any other redfieldiiform. Examination and comparison of specimens of Lasalichthys and Synorichthys from the Upper Triassic Chinle Formation and Dockum Group indicates that these taxa are only distinguishable at the species level, and Synorichthys is placed into synonymy with Lasalichthys, based on comparison of diagnostic morphological characters. Lasalichthys otischalkensis represents one of the oldest redfieldiiform taxa in North America.

Dissorophidae are terrestrial temnospondyls with conspicuous armor. All known Guadalupian dissorophid species, including Anakamacops petrolicus, are established based on incomplete materials. Here two new dissorophid specimens from the Guadalupian Dashankou Fauna of China are described and referred to A. petrolicus. They provide much more new osteological information of this species. Anakamacops petrolicus has the largest skull among all known dissorophid species. It exhibits knobby exostoses on the skull roof and mandible, a high suborbital bar that is greater than half of the skull height, a triangular, posteriorly closed otic notch with the anteroposterior length greater than the width, relatively smooth vomer with a few denticles on the lateral margin, two nuchal (occipital) ridges with short overlap where the right one is anterior to the left one, the interpterygoid vacuity far from the choana, low coronoid process, the medial ridge of the adductor fossa close to the ventral margin of the mandible, and the first inner osteoderm nearly triangular with concave margins in dorsal view. The Guadalupian dissorophid species form a monophyletic clade, Kamacopini, which was distributed in northeastern Pangaea, with the following synapomorphies to differentiate it from other dissorophids: suborbital bar high (subequal to or greater than the orbital height) and the interpterygoid vacuities far from the choanae.

The Yolomécatl area, northwestern Oaxaca, Sierra Madre del Sur Morphotectonic Province, Mexico, lies between 17°25′N and 17°30′N latitude, 97°29′W and 97°36′W longitude, at 2200–2500 m above sea level, and includes ∼90km2 of rugged territory, where lithostratigraphic units of Late Jurassic to Quaternary age crop out. The Tertiary succession, which unconformably overlies Mesozoic formations, includes the Nduayaco ‘Group,’ a stack of intermediate lava flows, and the Yolomécatl Formation, a lacustrine/fluvial sequence ∼650 m thick, sparsely interbedded by tuff sheets. One tuff with an ⁴⁰Ar/³⁹Ar date of 40.3 ± 1.0Ma places this formation and the southernmost Eocene local fauna from North America in the late middle Eocene (Bartonian). The volcanic Nicananduta ‘Group’ (°27 Ma) overlies the Yolomécatl Formation. The Yolomécatl local fauna includes, among others, two new taxa: Douglassciurus oaxacaensis, sp. nov., so far the oldest sciurid in the world, and the enigmatic Protozetamys mixtecus, gen. et sp. nov., which despite its early age (late middle Eocene), already shows adaptations to process fibrous or abrasive food. If the caviomorph affinities of Protozetamys are correct, they would suggest dispersal northward of a South American rodent lineage. These finds strengthen the hypothesis that this region (southeastern Mexico) was a center of diversification and extend the record of Paleogene mammals southward °553 km (∼3°30′ latitude), i.e., from Marfíl, Guanajuato (in central Mexico), to Yolomécatl, Oaxaca (in southeastern Mexico).

Melissiodon is a plesiomorphic cricetid genus characterized by its unique molar morphology, defined by many pits surrounded by thin and high ridges. This genus is endemic to Europe and ranges from the early Oligocene to the early Miocene. However, it is generally rare in rodent assemblages, particularly during the Miocene, rich samples only being available from a few German sites. Here we review all the Melissiodon material from the Vallès-Penedès Basin (Catalonia, Spain). This genus is present in several early Miocene sites ranging from biozone MN3 to MN4, but the scarcity of the material has precluded confident taxonomic assignments. Furthermore, the validity of Melissiodon arambourgi, a species based on a single specimen from the Vallès-Penedès site of el Fallol, has been questioned. After recent field campaigns, the available material has increased significantly, which allows for more robust taxonomic conclusions. All the Vallès-Penedès specimens are here referred to Melissiodon dominans, a widely dispersed species in the European early Miocene. After a revision of the holotype of M. arambourgi, we confirm that the original description and figures do not agree with it and conclude that it is a junior subjective synonym of M. dominans. The last occurrence of Melissiodon in the area is in the Sant Mamet site, located just a few meters below middle Miocene marine deposits, and represents one of the youngest records of this long-ranging genus.

We describe osteichthyan remains from the Upper Jurassic of the Ameghino (= Nordenskjöld) Formation of the Antarctic Peninsula. The fossils are referred to a suspension-feeding pachycormid based on the shape, morphology, and presence of acus fanunculi (needle teeth) on their gill rakers. Due to the fragmentary condition of the Antarctic material, we refer it to aff. Asthenocormus. The remains described here represent the first record of a suspension-feeding pachycormid from the Upper Jurassic of the Antarctic Peninsula and the oldest pachycormid yet recovered from Antarctica. The new fossil fish supports a possible early dispersal route through the Mozambique Corridor (= Trans-Gondwana or South African Seaway). We also describe the weathering produced by modern lichens, which might be misinterpreted as original bone structure.

Glyptodon Owen is one of the most frequently recorded glyptodonts in the Pleistocene of South America, especially between 20°S and 38°S. A high specific diversity has traditionally been proposed for the genus, including some species of assumed biostratigraphic importance (e.g., G. perforatus and G. clavipes). However, most of these species are poorly characterized, and the morphological variability in the different regions of the dorsal carapace has not been considered. Recent reviews have indicated that its diversity was lower than previously supposed, particularly in the late Pleistocene. In this scenario, this contribution aims to (1) review the late Pleistocene Glyptodon species from southern South America and (2) discuss the primary aspects of the geographic and chronological distribution of the species that are deemed as valid. Morphological and morphometric analyses indicate that the diversity in the late Pleistocene of southern South America is reduced to a single well-characterized species, G. reticulatus Owen. This species is recorded in MIS 3 and MIS 2 and is distributed in the Pampean, Mesopotamian, and north-central regions of Argentina, southern Bolivia, and Uruguay (∼20°S–38°S). In summary, the diversity of Glyptodontinae in the Pleistocene of southern South America was limited to two well-characterized species: G. munizi in the early–middle Pleistocene and G. reticulatus in the late Pleistocene–early Holocene.

The Miocene deposits of South America are notable for their diverse crocodyliform fauna, of which the giant caimanine Purussaurus is a well-known example. This contribution describes a new caimanine, Acresuchus pachytemporalis, gen. et sp. nov., based on an almost complete skull and mandible from the late Miocene Solimões Formation of the southwestern Brazilian Amazonia. This new taxon is based on a unique combination of characters, of which the presence of an upturned posterolateral margin of the squamosal throughout the entire lateral margin of the bone (a ‘horn’), with a dorsoventral expansion in the posterior portion of the eminence, stands out. We conducted a phylogenetic analysis of Eusuchia, which showed the new taxon as sister to Purussaurus. This placement allows discussion about the evolution of gigantism in the Acresuchus-Purussaurus clade, which reveals several characters that may be related to gigantism. Additionally, Acresuchus was probably a medium-sized generalist caimanine that had an ecological niche similar to the extant Melanosuchus niger. Until now, crocodyliforms that had such niches were unknown from the Solimões Formation.

A new paraclupeid fish, Tunisiaclupea speratus, gen. et sp. nov., is described from the Upper Barremian (Early Cretaceous) of the Chotts Basin, southern Tunisia. With a series of predorsal scutes of different size and shape, it is distinguished from other paraclupeids by the following combination of characters: anterior neural spines unfused; first uroneural bearing a dorsal laminar expansion and extending anteriorly nearly to third preural centrum; and hypural diastema present. The results of a phylogenetic analysis reconfirmed the monophyly of Ellimmichthyiformes and resolved Sorbinichthyoidei (Gasteroclupeidae +Sorbinichthyidae) as the most basal clade, with the Diplomystus clade the next, Armigatidae more derived than Diplomystus clade but with few diagnostic features, and Paraclupeidae with well-supported monophyly. Tunisiaclupea was resolved as a basal paraclupeid and an intermediate lineage between Ellimma branneri from the Lower Cretaceous of Brazil and Tycheroichthys dunveganensis from the Upper Cretaceous of North America. Tunisiaclupea is among the oldest ellimmichthyiforms known so far and extends the distribution of Paraclupeidae to the southern Mediterranean Tethys in the Early Cretaceous. Ellimmichthyiform diversity reached its peak in the Mediterranean region during the early Late Cretaceous, which might have resulted from allopatric speciation promoted by the sea-level highstand and the consequential land-sea distribution with increased food input, dispersal routes, and habitat fragmentation for these fishes.

The Late Triassic (Carnian) upper Santa Maria Formation of south Brazil has yielded some of the oldest unequivocal records of dinosaurs. Here, we describe a new saurischian dinosaur from this formation, Nhandumirim waldsangae, gen. et sp. nov., based on a semiarticulated skeleton, including trunk, sacral, and caudal vertebrae, one chevron, right ilium, femur, partial tibia, fibula, and metatarsals II and IV, as well as ungual and non-ungual phalanges. The new taxon differs from all other Carnian dinosauromorphs through a unique combination of characters, some of which are autapomorphic: caudal centra with sharp longitudinal ventral keels; brevis fossa extending for less than three-quarters of the ventral surface of the postacetabular ala of the ilium; dorsolateral trochanter ending well distal to the level of the femoral head; distal part of the tibia with a mediolaterally extending tuberosity on its cranial surface and a tabular caudolateral flange; conspicuous, craniomedially oriented semicircular articular facet on the distal fibula; and a straight metatarsal IV. This clearly distinguishes Nhandumirim waldsangae from both Saturnalia tupiniquim and Staurikosaurus pricei, which were collected nearby and at a similar stratigraphic level. Despite not being fully grown, the differences between Nhandumirim waldsangae and those saurischians cannot be attributed to ontogeny. The phylogenetic position of Nhandumirim waldsangae suggests that it represents one of the earliest members of Theropoda. Nhandumirim waldsangae shows that some typical theropod characters were already present early in dinosaur evolution, and it represents possibly the oldest record of the group known in Brazil.

The braincase anatomy of the sauropodomorph dinosaur Saturnalia tupiniquim from the Upper Triassic (Carnian) Santa Maria Formation of Brazil is described for the first time using computed tomography (CT). The braincase is characterized by a semilunar depression on the lateral surface of the basisphenoid, an occipital condyle whose ventral margin lies dorsal to the ventral margin of the cultriform process of the parabasisphenoid, a poorly developed preotic pendant, and anteriorly oriented basipterygoid processes. The comparative description improves our understanding of the early dinosaur braincase, which is poorly known relative to that of later representatives of the group. In addition, we discuss braincase features recently employed to investigate the phylogenetic relationships of dinosauromorphs, especially the pneumatic recesses of the braincase. Our study indicates that the semilunar depression and basioccipital recess are more widespread among dinosaurs and their closest archosauriform relatives than previously suggested. These structures are present in the three main dinosaurian lineages and also in non-dinosaurian dinosauromorphs, indicating that they might be plesiomorphic for Dinosauria. Likewise, the subsellar and basisphenoid recesses were observed in all examined dinosauromorph taxa, with variation observed in the relative development of these structures but not in their presence/absence. Our character reassessments and discussion of morphological variation as parts of transformation series strengthen the basis for integrating braincase features in future studies of dinosauromorph phylogeny.