A new kannemeyeriiform dicynodont is described from the Upper Triassic Tecovas Formation (Dockum Group) of west Texas, U.S.A. The taxon, Argodicynodon boreni gen. et sp. nov., is diagnosed by numerous cranial characters including: squamosal-interparietal sutural contact broad and interdigitating; tall, narrow intertemporal region formed by the parietals with long postorbitals forming the lateral face of the dorsal platform; interparietal forms knobby, bilobed exostoses that wedge between the parietals to form a W-shaped outline in dorsal view; basioccipital and exoccipital contributions to the occipital condyle are distinct, and the dorsal fossa separating the exoccipitals is deeply incised and dorsoventrally deep; caniniform process of the maxilla is dorsoventrally deep and well developed; and an elongated tab-like medial process of the articular exceeds the width of the quadrate roller. A phylogenetic analysis based on 23 continuous and 176 discrete (numeric) morphological characters and 120 taxa finds Argodicynodon conservatively to be a placeriine near the Placerias + Moghreberia group, representing the oldest placeriine in the southwestern U.S.A. and the first named dicynodont genus from the Dockum Group of Texas. A review of Euramerican dicynodont records exposes their hidden diversity and abundance in Laurasia during the Late Triassic. The records of Argodicynodon and other previously undescribed dicynodont fossils from nearby localities underscores the diversity of non-Placerias dicynodonts in the North American Upper Triassic.

Isolated fossil bones from freshwater Upper Cretaceous (Maastrichtian) deposits in the Mahajanga Basin of northwestern Madagascar are identified as belonging to a gonorynchiform fish. Multiple elements representing the same bone, including opercles, hyomandibulae, frontals, and basioccipitals, indicate that only a single gonorynchiform species is present. The most diagnostic element is here named as a new genus and species, †Vango fahiny; the other elements likely belong to the same taxon. The Madagascan gonorynchiform material shares features with members of the subfamily Chaninae and is assigned to that group. It is similar to the extant milkfish Chanos chanos but can be easily distinguished from that species by numerous features, such as the basioccipital and maxilla being relatively shorter than those of C. chanos, and the opercle being overall rounder and having a shorter auricular process. The presence of a chanid in Madagascar in the Maastrichtian most likely represents an invasion of a marine lineage into fresh waters. The previously known Cretaceous fossils of gonorynchiforms are spread throughout the Tethys Sea in mid-latitude to northern regions from the east (e.g., Lebanon, Europe) through to the southwest (e.g., Mexico, Brazil). †Vango faniny gen. et sp. nov. represents the first Mesozoic/Paleogene record of gonorynchiforms in East Gondwana, comprising primarily Antarctica, Australia, Madagascar, and the Indian subcontinent.

Sediments of the Woodbine Group exposed in northeastern Texas were deposited along the southwestern margin of Appalachia as a series of near-shore, shoreline, distal lowland swamp, lake, and fluvial deposits during a regression of the Western Interior Seaway in early and middle Cenomanian time. The Lewisville Formation (upper Woodbine Group) of north Texas preserves the most diverse terrestrial fossil assemblage known from Appalachia, but remains of small ornithischian dinosaurs have been conspicuously absent from it. An almost complete left dentary from the Lewisville Formation represents a new, small-bodied ornithopod taxon, Ampelognathus coheni gen. et sp. nov. The dentary is generally similar to those in non-iguanodontian ornithopods such as Hypsilophodon, Changchunsaurus, Haya, and Convolosaurus. Ampelognathus occupied an expected but previously missing component of the ‘mid’ Cretaceous terrestrial fauna of southwestern Appalachia. The growing diversity of fossil vertebrates and renewed paleobotanical study in the Lewisville Formation reinforces the importance of the unit’s fossil record for understanding eastern North American terrestrial ecosystems during an important transitional period in the earliest Late Cretaceous.

Within the notoungulate family Hegetotheriidae, some species have not been analyzed since their original publication more than a century ago. Here we present the first re-evaluation of Tegehotherium burmeisteri, including a detailed description of its holotype in an updated comparative framework, a species presumably coming from the Trelew Member of the Sarmiento Formation (Chubut Province, Argentina). Tegehotherium burmeisteri is included for the first time in a phylogenetic analysis centered in the interrelationships of hegetotheriids and defining clades according to the PhyloCode. Tegehotherium burmeisteri is recovered as a hegetotheriine closely related to Sallatherium and Hegetotherium; Hegetotheriopsis sulcatus is the earliest branch of the clade Hegetotheriidae, whereas Prohegetotherium and Paedotherium turn out to be paraphyletic, reinforcing results obtained in recent studies. The family Hegetotheriidae and both subfamilies, Hegetotheriinae and Pachyrukhinae, are recovered as monophyletic groups and defined phylogenetically, as well as two new clades: Pachyrukhini and Hemihegetotheriomorpha.

Many sauropod dinosaurs exhibit extensive postcranial skeletal pneumaticity that may have facilitated the evolution of extreme body sizes. Among titanosauriforms, complex, irregularly branching camellate chambers are found throughout the presacral vertebral column, often invading the ribs and ilium as well. To explore the function of these camellae, including reduction in bone volume, pneumaticity was examined in a titanosaur sauropod from the Upper Cretaceous Black Peaks Formation of Big Bend National Park, Texas, that includes pneumatic dorsal ribs and ilia. Using natural breaks to non-destructively observe the internal structure, patterns of camellate pneumaticity are described for the dorsal vertebrae, ribs, and ilium. The space occupied by camellae is quantified as the airspace proportion, which is reported here in a sauropod ilium for the first time. Airspace proportions exceed 70% in parts of the dorsal vertebrae and ilium, with lower values near the cotyles of the vertebral centra and the acetabulum. Values in the ribs decrease distally. These values are not appreciably different from those of sauropods with simpler camerate pneumaticity. If camellae did not offer greater weight reduction than camerae, they may have enhanced structural strength, as the chambers appear to align with stress in the vertebral centra and ilium. Apneumatic trabecular bone around the acetabulum, preacetabular process, and postzygapophyses, however, may indicate stresses too great for camellate bone to bear, although an ontogenetic influence cannot be ruled out.

The Pontils fossil site (middle Eocene, Ebro Basin, Spain) includes several vertebrate-bearing levels situated in a sequence recording a continental to marine transition. Although the locality has been known since the 1980s and scarce mammal remains have been already documented, an intensive sampling has not been developed until now. This work presents the first results of the recent field campaigns carried out at this site. Seven levels have yielded significant vertebrate remains, revealing a diverse assemblage which includes chondrichthyans, actinopterygians, amphibians, crocodilians, squamates, metatherians, eulipotyphlans, apatotherians, chiropterans, rodents, artiodactyls, perissodactyls, and primates, besides other non-vertebrate fossils. The Pontils assemblage indicates a mangrove swamp environment with warm and humid conditions and increasing marine influence towards the top of the sequence. Among mammals, primates are particularly diverse, including abundant remains of a minuscule, still undetermined omomyiform, and scarce teeth of Pseudoloris, Necrolemur, and an undetermined anchomomyin. The occurrence of larger benthic foraminifera allows the assignment of Pontils to Shallow Benthic Zone 17 (Bartonian), solving the debate about the age of the locality, previously assigned either to the Bartonian or the Lutetian. These data, together with previous magnetostratigraphic analyses, allow correlation to chrons C18r or C18n.1r, constraining the age of Pontils to between 39.58 and 41 Ma. Therefore, the Pontils site represents a new reference section for the correlation of marine and continental biostratigraphy during the middle Eocene.

†Serrivomer glehni, a new species of the Neogene saw-toothed eel (Anguilliformes, Serrivomeridae) is described based on the 55 specimens from the Middle–Upper Miocene Kurasi Formation of Sakhalin Island, Russia. This is the third record of fossil saw-toothed eels since the recovery of partial skeletons from the Miocene of Japan and Italy. The new species demonstrates close similarity to the extant Serrivomer species in overall body form and shape of separate bones and their complexes. The new species is characterized by the “longidentatus” type of vomerine dentition and by a single branchiostegal ray protruding beyond the hyoid bar, which suggests a close affinity to the modern S. sector. It can be reliably distinguished from all other species of Serrivomer by its lower number of vertebrae (134 vs. 140–172) and its larger cleithrum, which is positioned under the seventh instead of the eighth vertebral centrum.

A new, exceptionally well-preserved articulated skull roof and braincase of Melvius chauliodous, from the Kirtland Formation of New Mexico, reveals new features that provide detailed osteological information for Melvius, thus allowing for a reassessment of characters that defines the genus, its two recognized species M. chauliodous and M. thomasi, and its phylogenetic relationships within Vidalamiinae. The new features include the presence of dermopterotic rays (‘ribs’) and parietal ray bundles, previously unknown for both species of Melvius. The presence of elongated dermopterotic rays, a feature previously considered to be distinctive for the genus Calamopleurus, and tribe Calamopleurini, is now documented in Melvius, but these rays differ in their point of origination at the posteromedial corners of both dermopterotics. Bundles of short fan-shaped rays emanating from below the posterolateral corners of the parietals are also documented in both species of Melvius. Melvius was previously placed in the tribe Vidalamiini (Subfamily Vidalamiinae), but because it shares some unique features with members of the tribe Calamopleurini and the genus Calamopleurus, its placement within Vidalamiini, and the recognition of these two distinct clades (tribes) within Vidalamiinae, are not supported in our phylogenetic analysis. Previous characters distinguishing Melvius species, particularly differences in postinfraorbital ornamentation between M. chauliodous and M. thomasi, are considered dubious. However, other features may serve to determine interspecific variation or differences. For the present, we retain both species until more definitive material of M. thomasi is described.

The Middle Triassic remains a poorly understood time in the evolution of land vertebrates. Here, we report a new Ladinian-age vertebrate assemblage from Miedary (southern Poland). It consists of more than 20 taxa including fish (four species of Hybodontiformes, cf. Gyrolepis, Redfieldiiformes, ‘Thelodus’, Saurichthys, Serrolepis, Prohalecites, Ptychoceratodus), amphibians (Mastodonsaurus, Gerrothorax, Plagiosternum, chroniosuchian Bystrowiella), and reptiles (Owenettidae, Blezingeria, Nothosaurus, Tanystropheus, an additional, yet unidentified tanystropheid, the doswelliid Jaxtasuchus, and another archosauromorph, as well as eight archosauriform tooth morphotypes). Preliminary comparisons suggest biogeographic and environmental similarities with roughly contemporaneous localities known from the southwestern part of the Germanic Basin. Among differences in these two areas are the presence of a new armored archosauromorph and a surprising abundance of Tanystropheus remains in the new Polish site. Miedary is currently the richest source of three-dimensionally preserved Tanystropheus material in the world, which will be crucial for a better understanding of the preferred environment and lifestyle of this highly specialized reptile.

The ecological context of early vertebrate evolution has been characterized as a gradual shift from passive to more active feeding modes. This evolutionary scenario has been based largely on poorly constrained inferences of the feeding ecology of extinct stem-gnathostomes, among which heterostracans are the earliest. Pteraspidiform heterostracans possessed a feeding apparatus composed of rod-like oral plates with rows of rostrally facing denticles, previously interpreted as an adaptation for suspension feeding. Here, we test this hypothesis using computational fluid dynamics. We simulate water flow around 2D models consisting of rows of denticles both rostrally facing and reversed, to assess whether these orientations create recirculation patterns that are a hydrodynamic adaptation to suspension feeding. All tested models, independent of denticle orientation, show similar flow, velocity, and vorticity patterns. Recirculation patterns, highest velocity, and vorticity develop directly on top of the denticles and in spaces between the denticles. Therefore, we reject the hypothesis that denticle orientation is an adaptation for recirculation linked to suspension feeding. The denticles may instead have served to prevent material from lodging between the plates.

Hupehsuchia, an enigmatic group of marine reptiles from the Lower Triassic of South China, is characterized by a suite of features including polydactyly in either or both fore and hind limbs. Particularly, one parahupehsuchine specimen shows seven-digited forelimbs and a six-digited hind limb. However, questions remain as to what sequence manus configuration evolved in hupehsuchians. Here, we describe a new hupehsuchian with seven manual digits associated with extra carpals and digits. Our new phylogeny revealed the evolutionary sequence of extra carpals, metacarpals, and phalanges in hupehsuchians through preaxial and central polydactyly and suggested that the polydactyly of the manus evolved stepwise in hupehsuchians.

Bayshinoryctes shuvalovi gen. et sp. nov. is based on a fragmentary skull including right maxilla associated with right and left dentaries with partially preserved dentition from the Upper Cretaceous (Turonian–Santonian) Bayinshire Formation at Bayshin Tsav locality in Gobi Desert, Mongolia. Undated Bayesian analyses of two different data matrices recover the new taxon as a stem placental mammal within the clade containing also Maelestes from the Upper Cretaceous (Campanian) of Mongolia and Batodon from the Upper Cretaceous (Maastrichtian) of North America. Bayshinoryctes gen. nov. differs from Maelestes by a few dental characters, including three-rooted P4, double-rooted p3, and p5 with metaconid swelling.

We report the oldest fossil record of Istiophoridae from the Northern Alpine Foreland Basin (Western Paratethys) in Pucking, Austria (Lower Miocene, lower Aquitanian, ∼22.4 Ma). The studied specimen consists of fragments of five articulated vertebrae and a partially preserved second dorsal fin. We found that the Pucking specimen is only surpassed in age by an isolated vertebra from the Chandler Bridge Formation (South Carolina, U.S.A.), with ∼24.7–23.5 Ma. Pucking and the Chandler Bridge Formation differ in age by ∼1.1–2.6 Ma. The fossil istiophorid from the Chandler Bridge Formation was considered controversial due to the large gap in the fossil record between the first appearance of Istiophoridae and the last appearance of any other extinct billfish clade. Here we report that Pucking (Lower Miocene) and South Carolina (Oligocene) share the occurrence of Istiophoridae, †Xiphiorhynchinae (Xiphiidae), and †Aglyptorhynchinae (†Palaeorhynchidae). Our finding demonstrates that the coexistence of different groups of billfishes is maintained over time and that the Chandler Bridge specimen is a reliable record. Our work closes a temporal gap of ∼4.4 Ma between the previously recognized oldest Istiophoridae (∼18 Ma) and the last appearance of †Xiphiorhynchinae and †Aglyptorhynchinae. This result supports a longer evolutionary history for Istiophoridae, establishes continuity in the billfish fossil record, and is significant for future time calibrated phylogenies.

Ironstone surrounds many fossils and has a hardness that provides a significant challenge to fossil conservators globally. There are various forms of ironstone, with the carbonate forms of siderite and silicates most often containing vertebrate fossils and potentially preserved soft tissues. The ironstone itself is much harder than the fossils preserved within, leading to the mechanical preparation of the fossils––typically using pin vises or airscribes––being time-consuming and presenting the risk of damage. Existing chemical methods for softening ironstone to prepare the fossils have varied success and also pose a risk of damaging the fossil itself. Here we show that carbonic acid can soften ironstone without damaging permineralized bone or potentially preserved soft tissues. Carbonic acid treatments reduced the hardness of ironstone without causing any significant change in hardness, color, chemical composition, or weight to permineralized ceratopsian bones or a modern cervid bone that retained nonmineralized internal tissues. In addition, we found that solutions of sodium hydroxide and hydrogen peroxide were viable for softening ironstone to remove from the permineralized bone when preserved soft tissue recovery is not a priority. The treatments proposed in this study are important as they are applicable to a range of preparation scenarios, are cost-efficient, are relatively safe to handle, and cause no damage to permineralized fossil bones. Putting these methods into practice can lead to more efficient and safe preparation of fossils in ironstone.