Herein we report morphologically and histologically diagnostic trionychid specimens from the Barremian—Aptian (129.4–113.0 Ma) of Japan. One specimen (FPDM-V9487) is an associated skeleton that consists of a scapula, a humerus, an ischium, and hypoplastra. The limb and girdle bones are similar in morphology to those of modern trionychids. The hypoplastron also resembles that of modern trionychids; however, it is distinctive in that it completely lacks callosities. The other three new specimens are fragmentary costals that show a reduction in the shell bones and an absence of scute sulci. Two of the newly reported costals and FPDM-V0127 were examined histologically. Bone fiber bundles organized in a plywood-like structure, which is unique to trionychids, were identified. Fossil occurrence data indicate that morphologically and histologically typical trionychids already inhabited the coastal region of Asia (e.g., western Japan) as early as the Aptian. In contrast, the Hauterivian—Aptian stem trionychid Kappachelys okurai from Japan does not show a plywood-like shell microstructure, suggesting that K. okurai could be the earliest-branching taxon of known stem trionychids or a carettochelyid. Our paleobiogeographic compilation suggests that the spread of wetlands in the Northern Hemisphere and the high global temperature during the middle Cretaceous (Aptian—Turonian, 125.0–89.8 Ma) might have contributed to the dispersal of trionychids from Asia, allowing for the establishment of this modern freshwater reptilian fauna.

On the basis of an assigned specimen (USNM 526604, from the Plum Point Member of the Calvert Formation, Early Miocene, Maryland, U.S.A.), Araeodelphis natator Kellogg, 1957, is referred to the Platanistidae. A phylogenetic analysis identifies A. natator as the most stemward member of the family. By contrast, the extant river dolphin, Platanista gangetica (Platanistidae), is one of the most specialized odontocetes. Araeodelphis natator exhibits the following unique combination of characters: overall skull length (condylobasal length) estimated at about 50 cm; rostrum twice the length of the facial region; rostrum wider than deep throughout its entire length; approximately 50 teeth in each quadrant of rostrum; mesorostral canal closed dorsally through anterior half of rostrum by apposition of contralateral premaxillae; cranium with elevated orbits directed anterolaterally; maxillary crest (supraorbital process of frontal and overlapping maxilla) modestly thickened laterally and elevated above midline of skull; non-pneumatized supraorbital eminences; lobe of the pterygoid airsac sinus occupying orbital surface of frontal; zygomatic process compressed transversely; no postglenoid process; and glenoid facet faces medially. Araeodelphis provides new data about the definition and phylogenetic relationships of platanistids with other platanistoids, confirming the sister-group relationship with the extinct squalodelphinids and the ancestral platanistid skull morphology preceding the platanistine-pomatodelphinine split.

Plesiosauria is a diverse clade of marine reptiles that have been studied since the early 19th century. However, phylogenetic relationships within the group have been contentious due to limited taxon sampling and a misunderstanding of how ontogeny and interspecific and intraspecific variation affect character states. This is particularly true for elasmosaurids, a Cretaceous clade of long-necked plesiosaurians. In 2010, a new, nearly complete skeleton, MOR 3072, was collected from the Late Cretaceous (Campanian—Maastrichtian) Bearpaw Shale of northeast Montana. The specimen provides detailed morphological information rarely observed within Elasmosauridae, including a complete skull, the anterior 23 cervical vertebrae, a partial dorsal and caudal vertebral column, incomplete pectoral and pelvic girdles, elements of both fore- and hind limbs, ribs, and gastralia. Being early Maastrichtian in age, MOR 3072 is the stratigraphically youngest elasmosaurid known from the Western Interior Seaway and is recognized as a new genus and species, Nakonanectes bradti. We present a description of Nakonanectes bradti and conduct an extended phylogenetic analysis of Elasmosauridae. N. bradti is found to be deeply nested within the clade of large-bodied, long-necked, Western Interior Styxosaurinae. However, MOR 3072 is one of the smallest adult elasmosaurids ever recovered (5.1–5.6 m) and exhibits a reduced neck length compared with other North American elasmosaurids, resulting from a reduction in both centrum length and number of cervical vertebrae (39–42 were originally present). These features are convergent with the Southern Hemisphere clade of short-necked Maastrichtian elasmosaurids, Aristonectinae, and demonstrate multiple origins of short-necked body proportions from longer-necked ancestors within Elasmosauridae.

A fish-eating enantiornithine bird with a gastric pellet composed of fish bones has recently been reported from the Lower Cretaceous Jiufotang Formation of Liaoning Province, northeastern China. Along with other discoveries, this specimen reveals that distinct features of modern avian digestive system were well established in those early birds. On the basis of a detailed anatomical study presented here, we show that this fish-eating enantiornithine bird represents a new taxon, Piscivorenantiornis inusitatus, gen. et sp. nov. The well-preserved elements of the skull, neck, sternum, and pelvis further enrich our understanding of the morphological diversity in early enantiornithines. Most notably, the cranial articular facet of the caudal cervical vertebra is dorsoventrally concave and mediolaterally convex, a feature otherwise unknown among other birds and with unclear functional significance.

A new specimen of Lariosaurus xingyiensis is described and provides new information on the dermal palate of the skull and the postcranial skeleton. Based on a comprehensive comparison with the holotype specimen, an amended diagnosis of L. xingyiensis is given on the basis of the following features: a medium-sized species of Lariosaurus with jugal absent, longitudinal diameter of upper temporal fenestra about 1.7 times longitudinal diameter of orbit, retroarticular process elongate, clavicles without anterolaterally expanded corners, posterior scapular process (blade) slender and elongate, humerus distinctly shorter than femur, and dorsal process of ilium with distinct tubercular ornamentation. Two phylogenetic analyses of Nothosauridae demonstrate that Nothosaurus as previously conceived is not monophyletic whereas Lariosaurus is a monophylum. Three species previously referred to Nothosaurus are more closely related to Lariosaurus and are hereby reassigned to Lariosaurus, namely, L. juvenilis, L. youngi, and L. winkelhorsti.

Incisor enamel microstructures of three euharamyidans, Shenshou lui, Xianshou linglong, and X. songae, from the early Late Jurassic Yanliao Biota, Liaoning Province, China, are reported. The enamel of the three species consists of columnar divergence units that are delimited by planes of crystallite convergence and have irregular shapes and sizes, but there is no distinct line or plane along the divergent axis of crystallites in the unit. Of the three species, the enamel of S. lui is most primitive in having simpler enamel units that are roughly perpendicular to the enamel dentine junction. In Xianshou, the enamel units are oblique apically, and crystallites in the inner zone of enamel show greater differentiation to form erratically spaced clusters that resemble incipient prism-like; seam-like and sheath-like structures are also present. This enamel type may represent a transitional stage between prismless and prismatic enamel. Mapping enamel types from selected taxa of basal mammaliaforms on a simplified phylogeny, the columnar enamel in Thomasia, Shenshou, and some ‘plagiaulacoid’ multituberculates is interpreted as the plesiomorphic condition for allotherians, from which evolved the transitional enamel, as represented by Xianshou and the ‘plagiaulacoid’ Paulchoffatia, and the plesiomorphic prismatic enamel as in some post-‘plagiaulacoid’ multituberculates and gondwanatherians. The prismatic enamel in advanced multituberculates and other gondwanatherians may have evolved independently. Despite the new enamel morphologies revealed in euharamiyidans, the amelogenesis mechanism of how prisms, seams, and sheaths evolved within mammals remains unclear.

The Gondwanan hadrosaurid dinosaur record is relatively poorly known and very complicated. A new hadrosaurid, Bonapartesaurus rionegrensis, gen. et sp. nov., from the late Campanian—early Maastrichtian of the Salitral Moreno site, Argentina, is characterized by the following combination of characters: the ratio between the height of the neural spines and that of the centrum of the sacral vertebrae greater than 3.5; neural spines of the anterior section of the caudal vertebrae extremely long and evenly expanding distally; a preacetabular process of the ilium slightly deflected ventrally, with the angle greater than 150°; the ratio between the maximum dorsoventral depth of the posterior end of the preacetabular process and the dorsoventral distance from the pubic peduncle to the dorsal margin of the ilium less than 0.50; the ratio between the dorsoventral height and anteroposterior length of the iliac blade 0.8 or greater; asymmetrical lateral profile of the supraacetabular process; the posterior portion of the postacetabular process markedly thicker mediolaterally as a result of the dorsomedial twist of the postacetabular process; an anteriorly expanded cnemial crest restricted to the proximal end of the tibia; and articular surface of the astragalus for the internal malleolus of the tibia moderately expanded medially, articulating with only part of the ventral surface of the tibial internal malleolus. Our phylogenetic analysis indicates that Bonapartesaurus is located within the Tribe Saurolophini. Paleobiogeographically, its presence suggests at least two saurolophine dispersal events from North America, one toward South America and another toward Asia, no later than the late Campanian.

One new species of ailurid and two new genera and species of oligobunine mustelids are recognized from the early Hemingfordian (He1) Miller Local Fauna, Dixie/Levy County, Florida (U.S.A.). The ailurid is congeneric with the European early Miocene Amphictis but is smaller than the Old World species. One new oligobunine is a small hypercarnivore with a reduced metaconid and talonid on m1 and is related to Promartes and Oligobunis. The second is a small hypocarnivore with an enlarged metaconid on m1 and a relatively large m2 and is is related to Brachypsalis. Four other mustelids new to the Miller Local Fauna are the oligobunines cf. Brachypsalis sp. and cf. Oligobunis sp. and the leptarctines Craterogale cf. simus and Leptarctus ancipidens. These small carnivorans most closely resemble those of the early Hemingfordian Runningwater Formation of the better known northern Great Plains faunas and add further support that the Miller Local Fauna is older than the late early or early late Hemingfordian Thomas Farm.

Baidabatyr clivosus, gen. et sp. nov. (Multituberculata incertae sedis), is described on the basis of an ultimate upper premolar (P5) from the Lower Cretaceous Ilek Formation at Bol'shoi Kemchug 3 locality in Krasnoyarsk Territory, Russia. The new taxon differs from all known multituberculates by the cusp formula of the ultimate upper premolar (4:5:5), cusps well separated by valleys of flat crown surface, and three roots. It shares with a few non-cimolodontan multituberculates such rare characters of the ultimate upper premolar as elongated crown with length to width ratio of 2.0 and smooth enamel. Baidabatyr, gen. nov., is plesiomorphically similar to Paulchoffatiidae in having a horizontal profile of the ultimate upper premolar in lateral view. It likely represents a late survival of the Jurassic paulchoffatiid radiation of multitituberculates. Baidabatyr, gen. nov., is another relict taxon in the Early Cretaceous mammal fauna of the Ilek Formation, otherwise dominated by docodontans, eutriconodontans, and symmetrodontans.

The highly diverse tropical freshwater fish family Cichlidae is sparsely represented in the fossil record. Here we describe the new cichlid †Tugenchromis pickfordi, gen. et sp. nov., from the Upper Miocene (9–10 Ma) of central Kenya. The new taxon possesses a unique combination of characters, including six lateral line foramina on the lacrimal, three lateral line segments, cycloid scales, and a low number of vertebrae (29), dorsal fin spines (13), and dorsal soft rays (9). Its lacrimal morphology and tripartite lateral line suggest an affinity with the present-day Lake Tanganyika tribes Ectodini and Limnochromini, and thus with members of the ‘East African Radiation’ among the African cichlids. To further elucidate the relationships of †T. pickfordi, we used a comprehensive comparative data set comprising meristic data from all present-day tribes of the ‘East African Radiation.’ Principal coordinates analyses support links between the fossil and Ectodini Limnochromini, and additionally with modern Haplochromini. We conclude that †T. pickfordi could be an extinct lineage within the ‘most ancient Tanganyika tribes,’ or a stem lineage of the ‘ancient Tanganyika mouthbrooders.’ A direct relationship to the Haplochromini is unlikely because its members do not exhibit the derived characteristics of the lacrimal as seen in †T. pickfordi. Because Lake Tanganyika is located in the western branch of the East African Rift System, †T. pickfordi from the eastern branch supports the ‘melting-pot Tanganyika hypothesis,’ which posits that the cichlids of modern Lake Tanganyika are derived from riverine lineages that had already diversified prior to the lake formation.

Specimen NHMUK 28966 is a part of the skull of a crocodyliform from the Lower Cretaceous of the Isle of Wight. It was first described as Pholidosaurus meyeri but was attributed recently to a new genus and species, Leiokarinosuchus brookensis. The specimen is highly eroded, and most of the characters considered as diagnostic are likely the result of its poor state of preservation. All the observations are biased by the strong erosion of the skull, and consequently, no diagnostic character can be retained for this species. A review of the goniopholidid Anteophthalmosuchus hooleyi, also from the English Wealden, shows that NHMUK 28966 can be attributed to this species. Leiokarinosuchus brookensis is therefore a junior synonym of Anteophthalmosuchus hooleyi. In extant crocodylians, the growth of the occipital condyle is isometric whereas the growth of the foramen magnum is allometric relative to the skull table width. The slopes of the log-transformed data obtained for the holotype of A. hooleyi and BGS GSM 119453, a small specimen previously assigned to cf. Anteophthalmosuchus, are similar to those obtained for two extant species. This confirms observations of anatomical similarities and the attribution of BGS GSM 119453 to A. hooleyi. The new attributions clarify the taxonomic composition of the crocodylomorph assemblage from the Wessex Formation. It is clearly dominated by the large generalist goniopholidid A. hooleyi; the long-snouted morphology was represented by the medium-sized Vectisuchus leptognathus, whereas Theriosuchus sp., Koumpiodontosuchus aprosdokiti, and Hylaeochampsa vectiana are small dietary specialists.

Fossil sirenian specimens collected in 1964 by the late R. J. G. Savage's expeditions in north-central Libya are described. They come from early middle Eocene (lower Lutetian, 47.8–43.6 Ma) deposits at the locality of Bu el Haderait and represent a new genus and species, Libysiren sickenbergi. This animal is the largest known protosirenid, and the largest Eocene sirenian known to date (condylobasal length >420 mm). Its dental formula was apparently 3.1.5.3, with five premolar loci as in all other Eocene sirenians, but the teeth are mostly not preserved. Its postcranial skeleton is unknown except for the atlas, a thoracic vertebra, and rib fragments. Stable isotopes indicate a mostly seagrass diet and a habitat of fully marine salinity. The Protosirenidae presently comprise the genera Protosiren, Ashokia, and Libysiren, with their interrelationships unresolved. Together, they are most parsimoniously regarded as a paraphyletic group basal to both Trichechidae and Dugongidae. However, as more of their morphology and diversity are revealed, they may prove to be more closely allied to the former and may shed crucial light on the still-mysterious origins of the trichechids (manatees).

Remains of a varanid lizard from the middle Pleistocene of the Tourkobounia 5 locality near Athens, Greece are described. The new material comprises cranial elements only (one maxilla, one dentary, and one tooth) and is attributed to Varanus, the genus to which all European Neogene varanid occurrences have been assigned. Previously, the youngest undisputed varanid from Europe had been recovered from upper Pliocene sediments. The new Greek fossils therefore constitute the youngest records of this clade from the continent. Despite being fragmentary, this new material enhances our understanding of the cranial anatomy of the last European monitor lizards and is clearly not referable to the extant Varanus griseus or Varanus niloticus, the only species that could be taken into consideration on a present-day geographic basis. However, these fossils could represent a survivor of the monitor lizards of Asian origin that inhabited Europe during the Neogene.

Cyclotosaurus naraserluki, sp. nov., is a new Late Triassic capitosaurid amphibian from lacustrine deposits in the Fleming Fjord Formation of the Jameson Land Basin in Greenland. It is based on a fairly complete and well-preserved skull associated with two vertebral intercentra. Previously reported as Cyclotosaurus cf. posthumus, C. naraserluki is unique among cyclotosaurs for having the postorbitals embaying the supratemporals posteromedially. The anterior palatal vacuity presents an autapomorphic complete subdivision by a wide medial premaxillary-vomerine bony connection. The parasphenoid projects between the pterygoids and the exoccipitals, preventing a suture between the two, a primitive condition shared with Rhinesuchidae, Eryosuchus, and Kupferzellia. Within Cyclotosaurus, the Greenlandic skull has a distinctive combination of circular choanae (shared with C. ebrachensis, C. posthumus, and C. robustus) and a convex posteromedial margin of the tabulars (also present in C. ebrachensis and C. intermedius). A phylogenetic analysis indicates that C. naraserluki is the sister taxon of the middle Norian C. mordax from southern Germany, with which it shares a pair of premaxillary foramina. Cyclotosaurus is one of the most successful and diverse genera of Late Triassic temnospondyls, with at least eight species reported from middle Carnian to late Norian. Cyclotosaurus naraserluki is the largest amphibian ever reported from Greenland and one of the Late Triassic vertebrates with the highest northern paleolatitude currently known.

The skull roof of the species Szelepis yunnanensis (Liu, 1979) from the Early Devonian of Yunnan is redescribed, as well as other Szelepis material previously published. It appears that only the holotype of S. yunnanensis can be confidently assigned to this genus. The fusion of the preorbital plates into one plate strongly suggests the assignment of Szelepis yunnanensis to the monophyletic family Actinolepididae Gross, 1940, sensu stricto (comprising Actinolepis Agassiz, 1884, and Bollandaspis Schmidt, 1979). This is confirmed by a phylogenetic analysis. Hence, Szelepis constitutes the most ancient occurrence of the family but not the sister group to the remaining members.

This study provides new evidence of the diversity of Middle—Late Triassic teleosts with the description of new pholidophorids from Italy. The results of the phylogenetic analysis confirm the sister-group relationship [†Aspidorhynchiformes †Pachycormiformes] as members of Teleosteomorpha and †Prohalecites as the oldest teleosteomorph. The apomorphy-based Teleostei includes a new interpretation of †Pholidophoriformes as a monophyletic group supported by numerous synapomorphies and comprising two families, †Pholidophoridae and †Eurycormidae, fam. nov. The latter is only known from the Upper Jurassic of Europe. The monophyletic family †Pholidophoridae is known by about a dozen European taxa and a Middle Triassic genus (†Malingichthys) from southern Asia, which is the oldest member of the family. The addition of new pholidophorids provides a new interpretation of the possible relationships and taxonomic arrangements within the family †Pholidophoridae. The genera †Pholidorhynchodon and †Eopholidophorus stand as pholidophorids with a unique morphology of the upper oral margin, including a median rostral bone bearing a few large conical teeth, laterodermethmoids armed with large teeth, and the premaxillae displaced from the middle region of the oral margin. This study confirms previous hypotheses of character evolution among basal members of Teleostei, with implications for holostean character evolution. The synapomorphies shared by crown-group Teleostei appeared stepwise more than 140 million years ago over many speciation events and did not arise in a single ancestral species. The analyses of character distribution reflect the gradual accumulation of features that diagnose the crown group.