In this paper we re-examine the taxonomy and systematic position of the Eocene stingrays from Bolca Lagerstätte which are traditionally assigned to Urolophus crassicaudatus (Blainville). The analysis of their tooth morphology supports an assignment to the Eocene stingray genus Arechia Cappetta, a taxon known from isolated teeth from the Ypresian-Lutetian of northern and western Africa. The teeth of the Bolca specimens differ from the type species A. arambourgi in some characters (i.e., labial face with concave profile just below the crest, convex lower down; lingual face slightly more developed than the labial, with convex profile in its upper part and a concave profile in its mid-lower region) that justify the recognition of a second species within the genus, i.e., A. crassicaudata. This taxon also shows a unique combination of features (e.g., pectoral disc large and rhomboid; tail short, 44–52% of total length; ca. 238 vertebral centra; distal segment of propterygia located between mouth and antorbital cartilage; mesopterygium single, not fused to radials; 100–117 pectoral radials; 15–17 pelvic-fin radials; elongated caudal fin of aplesodic type) that supports its sister-group relationship with the living urolophids Urolophus and Trygonoptera. Arechia was a typical inhabitant of the near coastal and warm habitats that characterize the Monte Postale paleoenvironment.

The African Cichlidae Oreochromis (Alcolapia) and Oreochromis amphimelas can survive in extremely alkaline environments and represent the only known modern alkaliphilic cichlid fish found in Africa. The presence of fossil cichlids from the Miocene of central Kenya (Tugen Hills) that are morphologically similar to Oreochromis (Alcolapia) has been noted in previous works, but the conclusions remained tentative. The purpose of this study is to examine newly discovered fossil cichlids from the Tugen Hills and to compare their osteology with that of extant Oreochromis (Alcolapia). This is performed based on a comprehensive collection of comparative material, using microscopy and computed microtomography (µCT). We provide a revised diagnosis for the genus †Rebekkachromis, and revise its systematic relationships by assigning it to the Oreochromini (rather than to the Etiini). Two new species of †Rebekkachromis are described, i.e., †R. valyricus, sp. nov., and †R. vancouveringae, sp. nov., and a morphologically diverse assemblage of co-occurring †Rebekkachromis specimens is documented. Moreover, we found that †Rebekkachromis had three sensory canal pores (instead of four) on the lower arm of the preopercle, a feature that distinguishes both the modern Oreochromis (Alcolapia) and our fossil specimens from almost all other modern African cichlid fish. Our new data indicate that alkaliphile cichlids similar to Oreochromis (Alcolapia) were present in Central Kenya about 10–13 Ma ago and that the ability of African cichlid fishes to thrive in highly alkaline waters had already developed by that time.

The temnospondyl ‘Dissorophus’ angustus from the lower Permian (Archer City Formation) of Texas is one of several neglected taxa assigned to Dissorophidae. It shares with other dissorophids the presence of median osteoderms along the tips of the vertebral neural spines, but in a unique arrangement of an anterior set of external and internal osteoderms from vertebrae 5–9 followed by a transition at vertebra 10 to a single series ending at vertebra 17. This pattern has been interpreted as either an evolutionary intermediate between dissorophids with a single row of osteoderms and those with a double set or a growth stage from a juvenile with a single row to an adult with a full series of external and internal osteoderms. Restudy of the holotype indicates it is a relatively mature individual, confirms the unique arrangement of the osteoderms, and expands the list of autapomorphies to include additional features of the osteoderms, otic notch, stapes, and pelvic girdle. The holotype is redescribed as Diploseira angusta gen. et comb. nov. Phylogenetic analysis supports Diploseira as a dissorophid, but fails to resolve its placement among those dissorophids with osteoderms other than it is not likely a eucacopine. Removal of wildcard taxa provides support for Diploseira as a dissorophine. Incorporation of additional characters of osteoderms into the phylogenetic analysis has revealed no apparent pattern, suggesting a species-specific evolution of dissorophid osteoderms.

The European Paleocene terrestrial and freshwater turtle fauna is radically different from that in the Upper Cretaceous. This Paleocene fauna is largely formed by groups of turtles not found in the Mesozoic record of the continent. However, European Paleocene sites have produced several lineages that dispersed from other continents, including basal turtles (i.e., stem Testudines) and compsemydids (i.e., Paracryptodira). Both groups are well represented at the French upper Paleocene site of Mont de Berru, Marne Department. A new taxon from this locality, Gallica lapparentiana, gen. et sp. nov., is described here and attributed to the eucryptodiran lineage ‘Macrobaenidae.' Heretofore, no ‘macrobaenid' has yet been identified in the Cenozoic record of Europe. ‘Macrobaenids' have their origin in the Upper Jurassic of Asia. In fact, they represent the most diverse group of turtles currently known for the Lower Cretaceous record in that continent. They reach North America in the Upper Cretaceous, where they continue to diversify during the Upper Cretaceous and lower Paleocene. The first justified identification of ‘Macrobaenidae’ from the upper Paleocene of Europe, both in France and in Belgium, provides new data on the replacement process of European Late Cretaceous turtle fauna by new groups from other continents.

In this contribution, we re-describe the holotype (i.e., the posterior fragment of a left dentary with dentition) of Cargninia enigmatica from the Riograndia Assemblage Zone, Candelária Sequence, Santa Maria Supersequence (Upper Triassic, Brazil), originally considered a member of the Lepidosauria. In addition, two other specimens of lepidosauromorphs from the same locality are described and compared. Broad comparisons suggest that C. enigmatica possesses a unique combination of features, but several key features are widely distributed among basal non-rhynchocephalian lepidosauromorphs and kuehneosaurids. Thus, two possible scenarios are proposed: (1) Cargninia is a basal non-lepidosaurian lepidosauromorph, or (2) it is a basal lepidosaurian. The new specimens are a portion of a right maxilla with teeth (in two fragments) and a fragment of a dentary with teeth. The first specimen is identified as a lepidosauromorph because the maxilla cannot be directly compared with the holotype of C. enigmatica and it is difficult to evaluate if the differences in the dentition (upper versus lower teeth) are the result of intra- or interspecific variation. The dentary, on the other hand, is tentatively referred to C. enigmatica. These specimens together add new clues to understanding the early evolution of Lepidosauromorpha.

Acaenasuchus geoffreyi is a diminutive armored archosaur from the Upper Triassic Chinle Formation of northern Arizona, U.S.A., with uncertain evolutionary relationships and skeletal maturity. Known only from osteoderms, the taxon has been considered a valid taxon of aetosaur, juvenile specimens synonymous with the aetosaur Desmatosuchus spurensis, or a non-aetosaurian pseudosuchian archosaur. Here, we describe new fossils of Acaenasuchus geoffreyi that represent cranial, vertebral, and appendicular elements as well as previously unknown variations in the dorsal carapace and ventral shield. The skull bones are ornamented with the same anastomosing complex of ridges and grooves found on the paramedian and lateral osteoderms, and the appendicular skeleton resembles that of Revueltosaurus callenderi, Euscolosuchus olseni, aetosaurs, and other armored archosaurs such as erpetosuchids. Histology of osteoderms from the hypodigm of Acaenasuchus geoffreyi shows multiple growth lines, laminar tissue, and low vascularity, evidence that the individuals were close to skeletal maturity and not young juveniles. A revised phylogenetic analysis of early archosaurs recovers Acaenasuchus geoffreyi and Euscolosuchus olseni as sister taxa and members of a new clade that is the sister taxon of Aetosauria. This new phylogeny depicts a broader distribution of osteoderm character states previously thought to only occur in aetosaurs, demonstrating the danger of using only armor character states in aetosaur taxonomy and phylogeny. Acaenasuchus geoffreyi is also a good example of how new fossils can stabilize ‘wild card’ taxa in phylogenetic analyses and contributes to our understanding of the evolution of the aetosaur carapace.

We describe new specimens of the ornithischian dinosaur Scutellosaurus lawleriColbert, 1981, from the Lower Jurassic Kayenta Formation of Arizona and discuss their systematic importance. The new specimens represent at least 46 individuals and include two associated skeletons that preserve regions that were poorly known until now, including the skull and pelvis. Computed tomography (CT) assisted our interpretation of these specimens. Using an ornithischian data matrix, we first tested whether the two associated skeletons were justifiably assigned to Scutellosaurus lawleri and found that they group unequivocally with the holotype and paratype specimens. This enabled scoring of 35 character states that were previously unknown, raising the scoring completeness of Scutellosaurus lawleri from 52% to 67%. The results recovered Lesothosaurus diagnosticus as the basal-most member of Neornithischia, while corroborating the monophyly of Thyreophora and Scutellosaurus lawleri as its most basally branching member. In terms of numbers of specimens, Scutellosaurus lawleri is now the most abundant dinosaur known in any Early Jurassic vertebrate fauna. The presence of a second thyreophoran in the Kayenta Formation, along with the presence of Early Jurassic thyreophorans in Europe and Asia, suggests that Thyreophora may have originated in the northern hemisphere. The ornithischians from the Kayenta Formation support a pattern of dinosaurian diversification after the end-Triassic extinction in North America, if not a broader area, that was fueled by independent northward dispersals from the southern hemisphere, supporting dispersal as an early driver of dinosaurian evolution.

Ankylosaurs, dinosaurs possessing extensive body armor, were significant components of terrestrial ecosystems from the Middle Jurassic–latest Cretaceous. They diversified during the Early Cretaceous, becoming globally widespread. The Lower Cretaceous Wealden Supergroup (Berriasian–Aptian) of Britain has produced abundant ankylosaur material, with three currently recognized taxa: Hylaeosaurus armatus (Grinstead Clay Formation, West Sussex); Polacanthus foxii (Wessex Formation, Isle of Wight); and Horshamosaurus rudgwickensis (Weald Clay Group, West Sussex). However, these taxa are poorly understood; the initial descriptions of Hylaeosaurus and Polacanthus date from the 1800s and subsequent referrals of specimens have been based largely on provenance rather than morphological comparisons. This has led to uncertainty over the definitions of these taxa and the compositions of their hypodigms. Here, we redescribe the holotypes of Hylaeosaurus and Polacanthus, provide comparisons between these taxa, and use this information to assess the taxonomy of all ankylosaur specimens from the British Wealden Supergroup. We conclude that Hylaeosaurus and Polacanthus are valid, distinct taxa, which can be diagnosed by a combination of autapomorphies and a unique combination of characters. However, in both cases, we restrict their hypodigms to the holotypes. ‘Horshamosaurus rudgwickensis’ is a nomen dubium (an indeterminate nodosaurid dinosaur) and the majority of ankylosaur specimens from the Wealden Supergroup are taxonomically indeterminate. Hylaeosaurus and Polacanthus are separated stratigraphically, with Hylaeosaurus from the Valanginian of the Weald Sub-basin and Polacanthus from the Barremian of the Wessex Sub-basin. This separation supports the hypothesis of distinct lower and upper dinosaur faunas in the Wealden Supergroup of Britain.

Its huge size, excellent preservation, and completeness make Patagotitan mayorum a unique opportunity to explore the anatomy, paleobiological, and phylogenetic aspects linked to gigantism within Sauropoda. In this regard, we describe the appendicular skeleton of this titanosaurian species from the late Albian-aged Cerro Barcino Formation of Chubut Province, Argentina. The diagnosis of Patagotitan mayorum is revised, increasing the number of identified autapomorphies (i.e., lateral surface of the scapular blade with two divergent crests; anterior surface of proximal humerus with paired muscle scars; combined bulges on the deltopectoral area of the humerus; ischium with well-developed and sharp ridge projecting from the ischial tuberosity to the distal blade). Several diagnostic characters of this species correspond to osteological correlates associated to appendicular musculature (e.g., Mm. deltoideus scapularis, deltoideus clavicularis, and teres major; M. coracobrachialis; Mm. supracoracoideus/deltoideus clavicularis and latissimus dorsi; Mm. flexor tibialis 3 and adductor femoris 2), which we discuss in the context of sauropod evolution. In the light of a modification of the scaling equation previously proposed and adjusting the long bone circumference for the humeri of Patagotitan, a new body mass estimate of this species ranges between 42–71 tons, with a mean value of 57 tons. Although considerably less than the value obtained by the original linear equation, the corrected quadratic equation used here provides a mean body mass estimate that is more consistent with those derived from volumetric reconstructions of Patagotitan.

We describe abundant new remains of the medium-sized mustelid Mellivora benfieldi from the early Pliocene site of Langebaanweg (South Africa). The specimens are from the Muishond Fontein Pelletal Phosphorite Member (MPPM) and the Langeberg Quartz Sand Member (LQSM). Novel dentognathic—upper dentition, alveolus for m2—and postcranial—humerus, metacarpal V, femur and calcaneus—information is provided. This sample enables us to review the taxonomic status of Mio–Pliocene African mellivorines. Mellivora benfieldi is distinguished from the middle–late Miocene ‘Eomellivora’ tugenensis from Ngorora Kenya by its smaller size, and a M1 protocone messially placed; from the late Miocene Howellictis valentini from Chad by greater dental size with more crowded lower premolars, and p3 with distal accessory cuspid; and from the late Miocene Erokomellivora lothagamensis from Kenya, by shorter p4 and buccolingually shorter m1 protoconid. It also differs from H. valentini and Er. lothagamensis in absence or residual presence of the m2 alveolus. We infer M. benfieldi was an opportunistic, medium-sized carnivoran with semifossorial abilities, comparable to its living relative Mellivora capensis. A cladistic analysis was performed and our phylogenetic results place M. benfieldi as the sister species of M. capensis. Mellivorini contains M. benfieldi, M. capensis, and H. valentini. Additionally, we also include Er. lothagamensis and the Indian Promellivora punjabiensis. We propose the creation of one new tribe within Mellivorinae: Eomellivorini (Eomellivora spp. + Ekorus). It shares a common ancestor with Mellivorini and is characterized by large size, a robust and sharp dentition, as well as a skeleton with cursorial adaptations.

Desmatophocidae (Mammalia, Carnivora) represents the first of the four major pinniped clades to appear in the fossil record. However, the majority of its known diversity consists of derived species and little is known about the nascence of this early pinniped lineage. Here we report the discovery of Eodesmus condoni, gen. et sp. nov., represented by a nearly complete cranium from the Burdigalian Iron Mountain Bed of the Astoria Formation from the central coast of Oregon, U.S.A. Notably, this specimen possesses nasolabialis fossae, a plesiomorphic trait shared with stem pinnipedimorphs and the basal phocid Devinophoca sp., but not with any other desmatophocid. Phylogenetic analysis (98 characters, 27 taxa) resolved Eodesmus condoni as the most basal desmatophocid yet described. Poor support for the monophyly of Otarioidea, Odobenidae, and Phocoidea demonstrate that high-level relationships within Pinnipedia have yet to be conclusively resolved. The identification of another desmatophocid species at the already pinniped-rich Iron Mountain Bed suggests that the approximately synchronous mid-Miocene Climatic Optimum played a role in this increase in pinnipedimorph species diversity.