The early Eocene fossil assemblage of the London Clay (Southeastern England) is a key window to the early Paleogene diversification of teleost fishes in the open ocean. Despite their three-dimensional preservation that offers unique insight into skeletal anatomy, the London Clay fossils are still poorly described for the most part. †Whitephippus tamensis is a fossil teleost from this assemblage, known by several well-preserved specimens. Based on a complete description of the known material, including previously hidden structures (braincase, hyoid, and branchial arches) revealed through 3D microtomography, we reinterpret †Whitephippus as an early member of the teleost group Lampriformes. More specifically, the anatomy of †Whitephippus indicates that it is likely a member of the so-called ‘pelagic clade’ including modern opahs and oarfishes. This redescription of †Whitephippus provides the earliest definitive evidence of lampriforms conquering the pelagic environment, alongside numerous other teleost lineages.

Remote Devonian exposures in central Australia have produced significant but highly fragmentary remains of fish-grade tetrapodomorphs. We describe a new tetrapodomorph from the Middle–Late Devonian (Givetian–Frasnian) Harajica Sandstone Member of the Amadeus Basin, Northern Territory, which is represented by several nearly complete skulls along with much of the body and postcranial skeleton. The new form has a posteriorly broad postparietal shield, broad, triangular extratemporal bones, and a lanceolate parasphenoid. The spiracular openings are particularly large, a character also recorded in elpistostegalians and Gogonasus, demonstrating that these structures, suggestive of spiracular surface air-breathing, appeared independently in widely differing nodes of the stem-tetrapod radiation. A phylogenetic analysis resolves the new form within a cluster of osteolepidid-grade taxa, either as part of a polytomy or as the most basally branching representative of a clade containing ‘osteolepidids,’ canowindrids, and megalichthyids.

Small-bodied theropod dinosaurs are rare on southern landmasses but have been known from India for a century. Excavations by Charles Matley and Durgansankar Bhattacharji in uppermost Cretaceous sediments at Bara Simla, central India in 1917–1919 recovered small theropod vertebral and limb elements originally interpreted as coelurosaurians and separated into at least three species (Compsosuchus solus, Laevisuchus indicus, Jubbulpuria tenuis) based on features that can now be attributed to their serial position in the vertebral column. The comparatively recent discoveries of Noasaurus leali and Masiakasaurus knopfleri from similar-aged rocks in South America and Madagascar, respectively, and advances in basal theropod systematics led to a revised interpretation of most small-bodied Indian theropods as noasaurid abelisauroids. Here we review and redescribe Laevisuchus, Jubbulpuria, and Compsosuchus, including several elements that until now were thought lost, and describe a new partial noasaurid dentary from central India. The dentary bears the characteristic procumbent dentition of Masiakasaurus, which apparently is absent in Noasaurus. Likewise, cervical vertebrae of Laevisuchus more closely resemble those of Masiakasaurus than those of Noasaurus. Despite these similarities, phylogenetic analyses indicate that the balance of character data supports the Indian noasaurid species outside the sister-taxon pairing of South American and Malagasy species. Bones of small-bodied theropods have been recovered exclusively from the youngest Mesozoic localities in India (e.g., Pisdura, Bara Simla); to date they have not been reported from the slightly older localities in western and central India, from southern Indian sites in the Cauvery Basin, nor from the Vitakri Formation of Pakistan.

A new species of the paromomyid genus Arcius was recently described from the early Eocene locality of Masia de l'Hereuet in northeastern Spain. Reassessment of the holotype of this species reveals that it belongs to the apatemyid genus Heterohyus. Heterohyus ilerdensis, comb. nov., is the earliest record of Apatemyidae from Spain and the oldest species of Heterohyus described to date. Heterohyus radiated in the middle and late Eocene of western Europe before succumbing to extinction around the time of the Grande Coupure. Arcius is documented at Masia de l'Hereuet, but the three specimens currently known from the site are inadequate to be confidently assigned at the species level.

We describe a hemimandible of a medium-sized feline from the Middle Miocene (middle Aragonian, MN 5, local biozone Dc, around 15.5 Ma) site of Príncipe Pío-2, a recently discovered fossil locality placed in the urban limits of Madrid city (Spain), within an area previously known for its rich paleontological findings. The specimen is very well preserved, showing the complete hemimandible, as well as all the teeth except the incisors. Some characters, such as the missing talonid in m1, the high p3, the large mesial cuspid in p4, and the presence of a vestigial m2, prevent its adscription to other known feline taxa such as Styriofelis turnauensis or Miopanthera lorteti, previously recorded in the Middle Miocene faunas from Europe, but absent in the central basins of Spain. The hemimandible has robust mandibular corpus and ramus compared with these latter and to extant felines of similar size, and exhibits a relatively stronger ridged masseteric line, which points towards the existence of a proportionally larger and more powerful m. masseter that generated a strong bite when hunting. These characters suggest that the Príncipe Pío-2 feline could have preyed upon relatively larger prey than those of extant, similarly sized felines. We propose the new genus and species Magerifelis peignei for the studied specimen, a species that would also include the material from the French Middle Miocene localities of Bézian and Artenay.

Two new ctenacanthiform sharks representing two families, Ctenacanthidae and Heslerodidae, have been identified from the Middle to Late Mississippian marine sediments from Mammoth Cave National Park, Kentucky, and two Late Mississippian marine horizons in northern Alabama. The ctenacanthid, Troglocladodus trimblei, gen. et sp. nov., is known from isolated teeth from the Middle Mississippian St. Louis Formation and Ste. Genevieve Formation of Mammoth Cave and the Late Mississippian Bangor Limestone of northern Alabama. Troglocladodus gen. nov. is characterized by broad median cusps, pronounced longitudinal cristae, multiple intermediate cusps, and labiolingually shortened tooth bases. The heslerodid, Glikmanius careforum sp. nov., is known from isolated teeth and visceral arches from the Middle Mississippian St. Louis Formation and Ste. Genevieve Formation and the Late Mississippian Haney Formation, a Hartselle Sandstone-equivalent shale interval, and Bangor Limestone. Glikmanius careforum sp. nov. has proportionately distinct teeth among species of Glikmanius, with more robust and shorter cusps. The palatoquadrate of G. careforum has a short palatine ramus, otic process that is dorsoventrally deep and less expanded antero-posteriorly similar to Heslerodus and Dracopristis, and an elongated quadrate process like Heslerodus. The Meckel's cartilage is less dorsoventrally deep than Dracopristis. These two new ctenacanth taxa add important information on the diversity of Ctenacanthiformes suggesting three major lineages within the order. Ctenacanths have a rich fossil history from the Late Devonian to the Middle Permian evolving a variety of tooth types and small to large body sizes.

The detailed morphological description of the skull of the stem turtle Heckerochelys romani from the Middle Jurassic (Bathonian) of the Peski locality, Moscow Region, Russia, is provided herein. All cranial structures of Heckerochelys romani prove to be more advanced than in the Triassic and Early Jurassic stem turtles, but more primitive than in crown turtles; its morphology can be basic for both Cryptodira and Pleurodira. Only a few insignificant differences in skull morphology could be found between Heckerochelys romani and Eileanchelys waldmani, except for the size. Several cranial characters of Heckerochelys romani, such as architecture of the feeding apparatus and geometry of the cavum tympani, may indicate the aquatic habitat preference for this turtle, which is supported by taphonomic conditions.

Cannibalism (conspecific predation) is a surprisingly common and widespread behavior in modern ecosystems; however, direct evidence for cannibalism is strongly lacking in the fossil record. Identifying cannibalism is important to help better understand recondite trophic interactions between extinct species, as well as to detect potential resource pressures and competition in their ecosystems. Here, I describe the first direct evidence for a cannibalistic diet in a pachycormiform fish, based on three exceptionally well-preserved specimens of Pachycormus macropterus (de Blainville, 1818) with conspecific gut contents from the Early Jurassic (Toarcian) of Normandy (France). The generalist diet of Pachycormus is proven to be more complex than previously considered, which has recently been shown to include vampyropod squids, belemnoteuthids, ammonites, and small teleosts. All of the prey fishes were ingested whole in a longitudinal orientation, revealing that Pachycormus actively hunted juveniles of its own kind and was an indiscriminate opportunistic predator. The cannibal individuals themselves are also juveniles, further supporting previous findings for a dietary shift in Pachycormus from piscivorous to teuthophagous over ontogeny. Despite a widespread European distribution of Pachycormus, only specimens from the Normandy area show evidence for cannibalism, suggesting that the more conventional prey resources were either scarce or restricted at the site, prompting Pachycormus juveniles to indiscriminately predate on one another.

Eocene artiodactyls from Asia were considered less diverse and abundant than the contemporary perissodactyls, especially in the Eocene faunas from the Mongolia Plateau and Central Asia. By contrast, artiodactyls are highly diverse and endemic from the Eocene deposits of Europe and North America. Here we report two new genera and three new species of small- to medium-sized artiodactyls preserved by fragmentary materials from the Early and Middle Eocene of the Erlian Basin, Inner Mongolia, China. Paraphenacodus gabuniai sp. nov. represents the first record of artiodactyls from Arshantan Asian Land Mammal Age, and shows some more primitive characters than Paraphenacodus solivagus from the Middle Eocene of the Zaysan Depression of Kazakhstan. Although Paraphenacodus with generally bunodont teeth shows some similarities with both Early Eocene Tsaganohyus from Mongolia and early cebochoerid Gervachoerus from Europe, its affinities with other artiodactyls remain obscure. Two new genera and species, Irdinodon bicuspidata gen. et sp. nov. and Aliusuellus laolii gen. et sp. nov., from the Irdinmanhan ALMA represent new taxa of Lantianiinae and Tapirulidae, respectively. Irdinodon is characterized by twinned metaconules and entoconids on the upper and lower molars in lantianiines. Aliusuellus is characterized by a large size and a distinct ridge raised along the posterolingual side of the paracone to its apex on M2. These new artiodactyl materials from the Erlian Basin, as well as recently reported tapirulids and bunodont Erlianhyus, increase the diversity of the Eocene artiodactyls from the Mongolia Plateau, and provide new clues on the origin and dispersal of some early artiodactyls.

Vision is one of the most important senses for animals, allowing them to interact with their environment and with further implications for evolutionary histories. However, relevant soft tissues, such as the eye and associated structures, are not preserved in fossil vertebrates, limiting our knowledge of their visual capabilities. Here, we quantified absolute and relative orbit size for 400 species of dinosaurs and other extinct archosaurs using linear measurements of the preserved skeletal elements as a proxy for visual capabilities. Our results demonstrate that the orbit makes up on average 20% of skull size with a strong and consistent correlation across all sampled groups. This trend is largely independent of temporal distribution, species richness, and phylogeny. In fact, relative orbit size is narrowly constrained and did not surpass 45% of skull size, suggesting physiological and functional controls. Estimated eye size was found to be absolutely larger in herbivores, whereas carnivores tended to have smaller eyes absolutely and compared with skull size. Relatively large eyes only occurred in small-bodied species and vice versa. However, eye size alone was not sufficient to discriminate between different activity patterns or to characterize visual capabilities in detail.

Currently limited to cold climates near the Arctic circle, living walruses are the sole survivors of a previously much more diverse clade that occupied coastal waters throughout the northern hemisphere during the Mio–Pliocene. Though pinniped faunas have the highest diversity of walruses in the Miocene, the Purisima Formation of California records a moderately diverse assemblage of four walrus species. We report new specimens of tusked walruses (Odobeninae) including the oldest known members of Odobeninae, and Odobenini, and fossils of the specialized toothless odobenine walrus Valenictus Mitchell, 1961. Among these is the new species Valenictus sheperdi sp. nov., represented by a complete skull and referred post-crania from lower Pliocene strata within the Purisima Formation (5.33–4.89 Ma). Additionally, we report a geochronologically younger skull of Valenictus chulavistensis Deméré, 1994 from further up section (4.89–3.59 Ma). Expanded phylogenetic analysis recovers Odobeninae including Ontocetus Leidy, 1859 as the earliest diverging lineage in the Odobenini, and places a monophyletic Valenictus as the sister taxon to Pliopedia, Kellogg, 1921 which is included in a phylogeny for the first time; Odobenus is sister to the Valenictus + Pliopedia clade. Discovery of an isolated metacarpal near the base of the formation provides the oldest known well-dated evidence of odobenines. A diverse assemblage of molluskivores characterized the Neogene eastern North Pacific and their extinction around the Pliocene–Pleistocene boundary coincided with tectonically driven paleogeographic changes on the Pacific coast. The loss of temperate walruses may have provided opportunities for both new molluskivores and the otariid and phocid pinnipeds that make up present North Pacific pinniped communities.

Theropods comprise a successful group of mostly predatory dinosaurs with varied growth rates that colonized all continents. Much research has addressed the histology of the Global North's Mesozoic populations, especially coelurosaurians and allosauroids. However, little has been done to understand the histological patterns of the Gondwanan populations, especially abelisauroids. Previous studies detected disparate (parallel-fibered or fibrolamellar) bone profiles between noasaurids and abelisaurids but did not include broader quantitative analyses. Here we describe the femoral histology of a mid-sized abelisaurid from the Upper Cretaceous Serra da Galga Formation, Bauru Group, Southeast Brazil. Despite the harsh semiarid paleotropical context, our specimen shows a growth rate more similar to the Patagonian abelisaurids, challenging a previous hypothesis on environmental pressure selecting taxa with lower growth rates and parallel-fibered bone tissue. We also bring data to bear from several taxa to test the hypothesis of tissue differentiation within abelisauroid clades. Our logistic regression and correlation analyses show that the variation in histology in noasaurids and abelisaurids can be explained by body size and phylogeny when considering fibrolamellar tissue, but not parallel-fibered tissue. A decrease in growth rate through the deposition of parallel-fibered bone tissue may be an example of evolutionary convergence between noasaurids and some small-bodied sauropods.