Skull Roof Research Articles

New findings of the coelacanth Mawsonia Woodward (Actinistia, Latimerioidei) from the Late Jurassic – Early Cretaceous of Uruguay: Novel anatomical and taxonomic considerations and an emended diagnosis for the genus

New findings of Mawsonia from the Juro-Cretaceous Tacuarembó Formation (Uruguay) are presented. The new materials have taphonomic and anatomic significance, considering the biofabric and state of preservation of most of the bones. The most complete specimen studied is represented by several cranial and postcranial remains found in spatial association, including skull roof, cheek bones and opercula, neurocranium, palate, lower jaw, branchial and hyoid apparatuses; and also part of the shoulder and pelvic girdles. The present record is also complemented through the finding of several isolated bones from other individuals. General morphology of the bones, postparietal shield configuration and external ornamentation of dermic bones, allow to refer all the specimens to the species Mawsonia gigas. It is considered that the most complete specimen studied in this work constitutes one of the anatomically most informative records referable to this species, and to the genus, considering the following arguments: The presence of complete bones scarcely represented in previous records due to its delicate configuration, and the fact that all the remains are three-dimensionally preserved (being completely released from their sedimentary matrix). The new information provided by the comparative analyses is used for the following purposes: Bring a critical anatomical description, complement the diagnosis of the genus, and discuss previous taxonomic and ontogenetic hypotheses. The comparative analyses support previous taxonomic proposals, regarding the existence of morphological, size and ornamental variabilities, which as a whole characterize M. gigas and place it as the only recognizable species referable to this genus in South America.

The first record of a pterothrissin (Albuliformes, Albulidae) from the Muhi Quarry, mid-Cretaceous (Albian-Cenomanian) of Hidalgo, central Mexico

A new albuliform fish Nunaneichthys mexicanus gen. et sp. nov. is described from the Muhi Quarry, Albian-Cenomanian of Hidalgo, central Mexico. This species is a member of the subfamily Pterothrissinae, which is distinguished by having the following diagnostic combination of characters: skull roof bones ornamented with fine longitudinal striations, parasphenoid with conical teeth and a rounded tip, mandibles with denticles aligned in a single row, mandibular-quadrate articulation at the level of the posterior half of the orbit, subinferior mouth, preopercle somewhat expanded posteroventrally, and a long dorsal fin starting at the level of the 14th vertebra. The phylogenetic analysis indicates that this new species is closely related to the genus Pterothrissus on the basis of sharing a parietal pierced by a supraorbital sensory canal and crossed by anterior pit line, a parietal shorter than it is wide, and supratemporal commissure that runs for at least part of the trajectory trough parietals and/or supraoccipital. The new species is the earliest reported occurrence of a Pterothrissinae from the mid-Cretaceous of North America. The fossil record indicates that these bonefishes inhabited the Western Tethys sea during the Albian-Cenomanian.

An unusual historic dicynodont specimen (Therapsida: Dicynodontia) from the Dinodontosaurus Assemblage Zone of the Santa Maria Formation (Middle Triassic) of Rio Grande do Sul, Brazil

An unusual dicynodont specimen from the historical collection of von Huene and Stahlecker (1928/1929) is described from the Middle Triassic Dinodontosaurus Assemblage Zone of the Santa Maria Formation of Chiniqua, Rio Grande do Sul, Brazil. Hitherto only two dicynodont species, the stahleckeriid Stahleckeria potens and the more basal kannemeyeriiform Dinodontosaurus turpior, were recorded from this faunal assemblage. The specimen consists of an isolated partial brain case and intertemporal skull roof, a left nasal and a preparietal. In contrast to Stahleckeria, a preparietal is present, the intertemporal skull roof is extremely narrow and the postorbitals are short posteriorly. In contrast to Dinodontosaurus, the interparietal is narrow and intrudes far onto the intertemporal skull roof, the tabular is separately ossified and the entire intertemporal region is extremely narrow. The form represents a rare, hitherto unrecorded component of the fauna. Comparison to other known Middle Triassic dicynodonts shows that it cannot be referred to any known taxon, showing a unique combination of characters. Close resemblance is found to some other South American taxa, particularly to Jachaleria candelariensis from the Riograndia Assemblage Zone of the Caturrita Formation.

Endochondral bone in an Early Devonian 'placoderm' from Mongolia.

Endochondral bone is the main internal skeletal tissue of nearly all osteichthyans-the group comprising more than 60,000 living species of bony fishes and tetrapods. Chondrichthyans (sharks and their kin) are the living sister group of osteichthyans and have primarily cartilaginous endoskeletons, long considered the ancestral condition for all jawed vertebrates (gnathostomes). The absence of bone in modern jawless fishes and the absence of endochondral ossification in early fossil gnathostomes appear to lend support to this conclusion. Here we report the discovery of extensive endochondral bone in Minjinia turgenensis, a new genus and species of 'placoderm'-like fish from the Early Devonian (Pragian) of western Mongolia described using X-ray computed microtomography. The fossil consists of a partial skull roof and braincase with anatomical details providing strong evidence of placement in the gnathostome stem group. However, its endochondral space is filled with an extensive network of fine trabeculae resembling the endochondral bone of osteichthyans. Phylogenetic analyses place this new taxon as a proximate sister group of the gnathostome crown. These results provide direct support for theories of generalized bone loss in chondrichthyans. Furthermore, they revive theories of a phylogenetically deeper origin of endochondral bone and its absence in chondrichthyans as a secondary condition.

A review of the stem amnioteEldeceeon rolfeifrom the Viséan of East Kirkton, Scotland

ABSTRACTThe late Viséan anthracosauroidEldeceeon rolfeifrom the East Kirkton Limestone of Scotland is re-described. Information from two originally described and two newly identified specimens broadens our knowledge of this tetrapod. A detailed account of individual skull bones and a revision of key axial and appendicular features are provided, alongside the first complete reconstructions of the skull and lower jaw and a revised reconstruction of the postcranial skeleton. In comparison toSilvanerpeton, the only other anthracosauroid from East Kirkton,Eldeceeonis characterised by a proportionally wider semi-elliptical skull, comparatively smaller nostrils set farther apart, smaller and more rounded orbits, a shorter skull table with gently convex lateral margins, and a deeper suspensorium with a straight posterior margin and a small dorsal embayment. The remarkably large hind feet and elongate toes ofEldeceeonpresumably represent an adaptation for attaining high locomotory speed through increased stride length and reduced stride frequency. This would necessitate great muscle force but few muscle contractions. At the beginning of a new stride cycle, repositioning the pes anteriorly and lifting the toes off the ground would require a strong and large muscle to pull the femur upward and rotate it inward and forward. It is hypothesised that such muscle might correspond to thepuboischiofemoralis internus 2, which would extend along the posterior half of the vertebral column, consistent with the occurrence of long, curved ribs in the anterior half of the trunk. Using maximum parsimony and Bayesian inference, cladistic analyses of all major groups of stem amniotes retrieve a sister group relationship betweenEldeceeonandSilvanerpeton, either as the most plesiomorphic stem amniote clade or as a clade immediately crownward of anthracosauroids.

Cranial morphology of the tanystropheid Macrocnemus bassanii unveiled using synchrotron microtomography

The genus Macrocnemus is a member of the Tanystropheidae, a clade of non-archosauriform archosauromorphs well known for their very characteristic, elongated cervical vertebrae. Articulated specimens are known from the Middle Triassic of Alpine Europe and China. Although multiple articulated specimens are known, description of the cranial morphology has proven challenging due to the crushed preservation of the specimens. Here we use synchrotron micro computed tomography to analyse the cranial morphology of a specimen of the type species Macrocnemus bassanii from the Besano Formation of Monte San Giorgio, Ticino, Switzerland. The skull is virtually complete and we identify and describe the braincase and palatal elements as well the atlas-axis complex for the first time. Moreover, we add to the knowledge of the morphology of the skull roof, rostrum and hemimandible, and reconstruct the cranium of M. bassanii in 3D using the rendered models of the elements. The circumorbital bones were found to be similar in morphology to those of the archosauromorphs Prolacerta broomi and Protorosaurus speneri. In addition, we confirm the palatine, vomer and pterygoid to be tooth-bearing palatal bones, but also observed heterodonty on the pterygoid and the palatine.

An exceptional neurovascular system in abelisaurid theropod skull: New evidence from Skorpiovenator bustingorryi.

Abelisaurids were one of the most successful theropod dinosaurs during Cretaceous times. They are featured by numerous derived skull traits, such as heavily ornamented bones, short and tall snout, and a strongly thickened cranial roof. Furthermore, nasals are distinctive on having two distinct nasal patterns: strongly transversely convex and heavily sculptured (e.g., Carnotaurus), and transversely concave, with marked bilateral crests and poorly sculptured surfaces (e.g., Rugops). Independently of the pattern, some abelisaurid nasals (e.g., Rugops) show a distinctive row of large foramina on the dorsal surface, which were in general associated to skin structures (scales). Skorpiovenator bustingorryi is a derived abelisaurid coming from the upper Cretaceous beds of northwestern Patagonia, represented by an almost complete skeleton including a well-preserved skull. Particularly, the skull of Skorpiovenator shows nasal bones characterized by being transversely concave, rimmed by lateral crests and with a conspicuous row of foramina on the dorsal surface. But more interesting is that the skull roof also exhibits a row of large foramina that seem to be continuous with the previous nasal foramina. CT scans made on the skull corroborates a novel feature within theropods: the nasal foramina on the external surface are linked to an internal canal that runs across the nasal bones. We compared this feature with CT scans of Carnotaurus and revealed that it also possess an internal system as in Skorpiovenator, but being notably smaller. The symmetry and disposition of the foramina in the nasal and skull roof bones of Skorpiovenator would indicate a neurovascular correlate (i.e., blood vessels and nerves), probably to the lateral nasal and supraorbital vessels and the trigeminal nerve. The biological significance of such neurovascular system can be conjectured from several hypotheses. A possible one involves an enhanced blood volume in these bones linked to a zone of thermal exchange, which may help avoid overheat of encephalic tissues. Another plausible hypothesis takes into account the presence of display skin structures in which blood volume nourished the mineralized skin, which would have a role in intraspecific communication. However, other more speculative explanations should not be discarded such as a correlation with integumentary sensory organs.

Neuroanatomy of the spinosaurid Irritator challengeri (Dinosauria: Theropoda) indicates potential adaptations for piscivory

Spinosauridae, a theropod group characterized by elongated snouts, conical teeth, enlarged forelimbs, and often elongated neural spines, show evidence for semiaquatic adaptations and piscivory. It is currently debated if these animals represent terrestrial carnivores with adaptations for a piscivorous diet, or if they largely lived and foraged in aquatic habitats. The holotype of Irritator challengeri, a nearly complete skull from the late Early Cretaceous Santana Formation of northeastern Brazil, includes one of the few preserved spinosaurid braincases and can provide insights into neuroanatomical structures that might be expected to reflect ecological affinities. We generated digital models of the neuroanatomical cavities within the braincase, using computer tomography (CT) data. The cranial endocast of Irritator is generally similar to that of other non-maniraptoriform theropods, with weakly developed distinctions of hindbrain and midbrain features, relatively pronounced cranial flexures and relatively long olfactory tracts. The endosseous labyrinth has a long anterior semicircular canal, a posteriorly inclined common crus and a very large floccular recess fills the area between the semicircular canals. These features indicate that Irritator had the ability for fast and well-controlled pitch-down head movements. The skull table and lateral semicircular canal plane are strongly angled to one another, suggesting a downward angling of approximately 45° of the snout, which reduces interference of the snout with the field of vision of Irritator. These neuroanatomical features are consistent with fast, downward snatching movements in the act of predation, such as are needed for piscivory.

The braincase of <em>Bissektipelta archibaldi</em> — new insights into endocranial osteology, vasculature, and paleoneurobiology of ankylosaurian dinosaurs

We describe in detail three braincases of the ankylosaur Bissektipelta archibaldi from the Late Cretaceous (Turonian) of Uzbekistan with the aid of computed tomography, segmentation, and 3D modeling. Bissektipelta archibaldi is confirmed as a valid taxon and attributed to Ankylosaurinae based on the results of a phylogenetic analysis. The topographic relationships between the elements forming the braincase are determined using a newly referred specimen with preserved sutures, which is an exceedingly rare condition for ankylosaurs. The mesethmoid appears to be a separate ossification in the newly referred specimen ZIN PH 281/16. We revise and discuss features of the neurocranial osteology in Ankylosauria and propose new diagnostic characters for a number of its subclades. We present a 3D model of the braincase vasculature of Bissektipelta and comment on vascular patterns of armored dinosaurs. A complex vascular network piercing the skull roof and the wall of the braincase is reported for ankylosaurs for the first time. We imply the presence of a lepidosaur-like dorsal head vein and the venous parietal sinus in the adductor cavity of Bissektipelta. We suggest that the presence of the dorsal head vein in dinosaurs is a plesiomorphic diapsid trait, and extant archosaur groups independently lost the vessel. A study of two complete endocranial casts of Bissektipelta allowed us to compare endocranial anatomy within Ankylosauria and infer an extremely developed sense of smell, a keen sense of hearing at lower frequencies (100–3000 Hz), and the presence of physiological mechanisms for precise temperature control of neurosensory tissues at least in derived ankylosaurids.

STUDIES ON PYCNODONT FISHES (II): REVISION OF THE SUBFAMILY PYCNODONTINAE, WITH SPECIAL REFERENCE TO ITALIAN FORMS

The diagnosis, composition, and phylogenetic relationships of the European subfamily Pycnodontinae are revised; its record is pushed back from the Cenozoic into the Mesozoic. The Pycnodontinae is confirmed as a monophyletic group. It is diagnosed by: thin, laminar supraoccipital exposed all along the posterior border of the skull roof; cleithrum with two posterior expansions framing the notch for the pectoral fin; reduction in the ossification of the flank scales (clathrate pattern); reduction of the preopercular into a very low bone, never higher than the exposed, ornamented portion of the dermohyomandibular; and presence of a bifid cloacal scale. The subfamily includes the tribe Pycnodontini (Pycnodus + Oropycnodus), Polazzodus, Sylvienodus, and Tergestinia. The former “Coelodus” gridellii is moved to Polazzodus gridellii n. comb. The Italian genera, Pycnodus, Polazzodus, and Tergestinia, form a monophyletic group together with the French Oropycnodus. The present analysis shows that Polazzodus, Sylvienodus, and Tergestinia are pycnodontin fishes, but. Haqelpycnodus, Libanopycnodus, Scalacurvichthys, and Sigmapycnodus do not belong to the Pycnodontinae. “Pseudopycnodus” and “P. nardoensis” are considered nomina dubia. This revision has revealed new aspects of the last known diversification in the evolutionary history of the Pycnodontiformes, showing that the group was still thriving in the Western Tethys during the Late Cretaceous. For the present analysis, additional arguments involving ontogenetic restrictions are provided to favour ordering multistate characters in pycnodonts.

Redescription and Phylogenetic Assessment of ‘Prognathodon’ Stadtmani: Implications for Globidensini Monophyly and Character Homology in Mosasaurinae

ABSTRACT Prognathodon stadtmani was discovered in the Campanian portion of the Upper Cretaceous Mancos Shale in western Colorado in 1975. Following its original description almost two decades ago, more material of the holotype was prepared. Those new elements include a quadrate, often considered one of the most critical bones for understanding mosasaur systematics, portions of the skull roof, posterior mandible, and braincase. Prognathodon stadtmani exhibits a suite of features that include both derived character states observed in later mosasaurines and primitive features present in earlier members of the clade, such as Clidastes. Although the quadrate resembles those of Prognathodon and Globidens in some respects, it lacks fusion between the suprastapedial process and ascending tympanic rim observed in those taxa. I ran a series of phylogenetic analyses using parsimony and Bayesian inference to understand the relationships of this taxon. Regardless of character selection or methodology, ‘Prognathodon’ stadtmani was not found to be monophyletic with the rest of the genus Prognathodon. Depending on method, it was recovered as the sister taxon to the rest of Globidensini, the sister taxon to Mosasaurini + Globidens, or an early diverging mosasaurine outside of both Globidensini and Mosasaurini. Owing to these results, I assign the type to a new genus, Gnathomortis, gen. nov., yielding the species Gnathomortis stadtmani, comb. nov. Furthermore, the rest of the genus Prognathodon and the clade Globidensini more broadly were not consistently recovered as monophyletic. Many characters of the quadrate and the dentition that typically united those clades are optimized as homoplastic based on my resulting topologies.

Computed tomographic analysis of the cranium of the early Permian recumbirostran ‘microsaur’ Euryodus dalyae reveals new details of the braincase and mandible

AbstractRecumbirostran ‘microsaurs’ are a clade of Palaeozoic tetrapods that possess numerous morphological adaptations for fossorial ecologies. Re‐study of many ‘microsaurs’ using tomographic methods has provided substantial new data on poorly known anatomy that informs their debated phylogenetic position. Recent studies have identified suites of features among recumbirostrans that place the group within crown Amniota, contrary to hypothesized positions on the amniote stem or the lissamphibian stem. Herein we describe the cranial anatomy of the early Permian gymnarthrid Euryodus dalyae through tomographic analysis of the holotype from South Grandfield, Oklahoma and new specimens from karst deposits near Richards Spur. The braincase of E. dalyae is composed of well‐ossified pleurosphenoids, orbitosphenoids that brace against the skull roof, and unpaired median ossifications. The otic capsules are well‐ossified, and the occiput is unconsolidated. Analysis of the mandibles, typically obscured in articulated specimens, reveals a second tooth row on the dentary, a feature previously unknown in ‘microsaurs’ that is reminiscent of the condition of the co‐occurring captorhinid Captorhinus aguti. The Richards Spur specimens share many of these features, including the second tooth row, but the neurocranium of the scanned specimen (OMNH 53519) differs from that of the holotype of E. dalyae (e.g. absence of unpaired median ossifications), and these specimens are referred to Euryodus sp. These data add to the growing neurocranial dataset of ‘microsaurs’, which is essential for iterative reevaluation of early tetrapod phylogeny. This discovery of multiple tooth rows in ‘microsaurs’ provides further support for the hypothesized close relationships between ‘microsaurs’ and reptiles.

Captorhinid reptiles from the lower Permian Pedra de Fogo Formation, Piauí, Brazil: the earliest herbivorous tetrapods in Gondwana.

The Pedra de Fogo Formation in the Parnaíba Basin of northeastern Brazil hosts a recently discovered lacustrine fauna and provides the only known record of the Captorhinidae in South America. Here, new captorhinid remains from this unit are described. Two partial mandibles, including one formerly ascribed to the genus Captorhinus, are here referred to Captorhinikos sp. a genus previously described from North America. The natural mould of a large mandible probably represents a new taxon within the captorhinid subclade Moradisaurinae, and a small skull roof is regarded as Captorhinidae indet. Captorhinids are generally considered to have been herbivores or omnivores. The Pedra de Fogo captorhinids likely played an important ecological role as primary consumers in the palaeoenvironment of this geological unit, which is also known for its extensive record of petrified forests. The new finds reinforce the close relationships between the continental faunas of palaeotropical western Gondwana and palaeoequatorial North America during the Cisuralian.

The anatomy of the dermatocranium and mandible of Cacops aspidephorus Williston, 1910 (Temnospondyli: Dissorophidae), from the Lower Permian of Texas

ABSTRACT For the first time, the cranial suture pattern for the type species of Cacops, C. aspidephorus, is described in detail. A majority of sutures, including the lower jaw, the skull roof, and the palate, are now known in detail, although details are still lacking for the posterior skull table. Notable new information about C. aspidephorus includes the presence of a lateral exposure of the palatine (LEP), a lateral exposure of the ectopterygoid (LEE) that fuses with the jugal with growth, and a subtympanic flange composed mostly of the supratemporal. Cacops aspidephorus is very similar to C. morrisi, but differences, including a fully closed otic notch in C. aspidephorus, are sufficient to maintain both as distinct species. Uniquely, C. aspidephorus shows palatal dentition of the same size as the marginal dentition, but it remains to be seen whether this is a widespread feature or ontogenetically transient. These new data will finally permit the inclusion of this iconic taxon, described over 100 years ago, into larger-scale phylogenies of dissorophoid and temnospondyl relationships.

Histology of the preparietal: a neomorphic cranial element in dicynodont therapsids

ABSTRACT The preparietal, a neomorphic midline ossification on the skull roof, is thought to have evolved three times in therapsids, but its development and homology remain poorly understood. Here, we provide preliminary data on the histology of this element in specimens referred to Diictodon feliceps and an indeterminate species of Lystrosaurus. The preparietal has previously been noted to vary substantially in its shape on the dorsal surface of the skull in several dicynodonts, and we found similar variation in thin section. In Diictodon, the preparietal forms a prong that embeds itself entirely within the frontals and shows evidence of a midline suture anteriorly. The sectioned specimen of Lystrosaurus shows histological evidence of immaturity and features a well-defined midline suture at the posterior end of the preparietal, although an anterior prong was not present. In both taxa, the anteroventral portion of the preparietal forms a strongly interdigitating suture with the underlying frontals and parietals. More posteriorly, the preparietal is composed of fibrolamellar bone suggestive of rapid posteroventral growth. In large dicynodont species, the dorsal expression of the preparietal appears to show negative allometry compared with other cranial roofing elements during ontogeny, but the significance of this geometry is unclear. In addition, histological work is needed on the preparietal in gorgonopsians and biarmosuchians to determine whether the features characterizing dicynodonts are also seen in the other two groups of therapsids that evolved a preparietal. The therapsid preparietal provides a rare opportunity to study the development and evolution of a neomorphic cranial element in the vertebrate fossil record.

A New Species of Megalichthys (Sarcopterygii, Megalichthyidae) from the Upper Devonian (Famennian) of Pennsylvania, U.S.A., and a Report on the Cosmine-Covered Osteolepiform Fossils of the Catskill Formation

ABSTRACT New material from the Upper Devonian (Famennian) Catskill Formation of Pennsylvania, U.S.A., indicates the presence of a new species of Megalichthys. A large collection of complete and well-preserved fossil material from the Red Hill field locality enables a thorough anatomical description that is not commonly available in Megalichthyidae. The cranial material includes skull roof, partial cheek, lower jaw, opercular-gular elements, palatoquadrate, and dermal palatal elements. The postcranial material includes pectoral fin elements including cleithrum, mesomeres, and lepidotrichia; pelvic fin including lepidotrichia; and body scales in articulation. The new species is distinguished from other species of Megalichthys by the presence of a pineal series of bones, a triangular-shaped principal gular, and a lack of sensory canal pores on the postparietal. We review the taxonomic history and status of Megalichthyidae and Megalichthys and provide revised diagnoses for each that include only discrete features demonstrated to be sufficient for taxonomic assignment. We discuss additional cosmine-covered osteolepiform fossils from other Catskill Formation exposures. These include the type and only specimen of Sterropterygion brandei and seven new specimens (including a partial snout, a partial parietal shield, a partial postparietal shield, a partial cheek, and complete lower jaws) that potentially represent megalichthyid species in addition to the one at the focus of this study. With this description of new megalichthyid material, the Catskill Formation continues to produce, in some cases, the only known Devonian occurrence of otherwise younger taxa.

Chip off the outer table of skull

Chip off the outer table of skull

Cranial anatomy of Allosaurus jimmadseni, a new species from the lower part of the Morrison Formation (Upper Jurassic) of Western North America.

Allosaurus is one of the best known theropod dinosaurs from the Jurassic and a crucial taxon in phylogenetic analyses. On the basis of an in-depth, firsthand study of the bulk of Allosaurus specimens housed in North American institutions, we describe here a new theropod dinosaur from the Upper Jurassic Morrison Formation of Western North America, Allosaurus jimmadseni sp. nov., based upon a remarkably complete articulated skeleton and skull and a second specimen with an articulated skull and associated skeleton. The present study also assigns several other specimens to this new species, Allosaurus jimmadseni, which is characterized by a number of autapomorphies present on the dermal skull roof and additional characters present in the postcrania. In particular, whereas the ventral margin of the jugal of Allosaurus fragilis has pronounced sigmoidal convexity, the ventral margin is virtually straight in Allosaurus jimmadseni. The paired nasals of Allosaurus jimmadseni possess bilateral, blade-like crests along the lateral margin, forming a pronounced nasolacrimal crest that is absent in Allosaurus fragilis.

A new stereospondylomorph, Korkonterpeton kalnense gen. et sp. nov., from lower Permian of the Czech Krkonoše Piedmont Basin and a redescription of Intasuchus silvicola from the lower Permian of Russia (Temnospondyli, Amphibia)

A new temnospondyl, Korkonterpeton kalnense gen. et sp. nov., is described on the basis of an almost complete specimen from the lover Permian Prosečné Formation of the Czech Krkonoše Piedmont Basin. The exceptional preservation of the holotype allows a detailed description of the cranial and postcranial characters: Korkonterpeton kalnense gen. et sp. nov. is characterized by the presence of vomerine fangs located anteriorly to the posterior choana, much longer than wide tabulars – as long as the supratemporals, a deeply concave posterior margin of the skull table, extraordinarily elongated exoccipitals, anteriorly widened pterygoids and a parasphenoid cultriform process swollen at its mid-length. In order to clarify the relationship between this new taxon and Intasuchus silvicola Konzhukova, 1956 from the lower Permian (late Kungurian) of the Russian Inta Basin, the latter is also redescribed here: Intasuchus silvicola exhibits a lacrimal entering the septomaxilla, a widened jugal, a posterolaterally widened interpterygoid vacuity, a subtemporal window elongated anteriorly up to the anterior orbital region, an elongated basipterygoid ramus which is as long as the orbit width, a vomer with a parachoanal tooth row, and an ectopterygoid of about the same length as the palatine. The description of Korkonterpeton kalnense gen. et sp. nov. and the revision of Intasuchus silvicola complete our knowledge on the origin and evolution of early stereospondylomorph temnospondyls during the lower Permian.

Cranial morphology of a new phytosaur (Diapsida, Archosauria) from the Upper Triassic of India: implications for phytosaur phylogeny and biostratigraphy

AbstractDetailed description and phylogenetic assessment of a phytosaur skull collected from the Tiki Formation of the Rewa Gondwana Basin of India and earlier diagnosed asParasuchus hislopi, show that it pertains to a new genus and species,Volcanosuchus statisticae. The new taxon is characterized by marginal overlapping of the nostrils by the antorbital fenestrae, external nares situated on a bulbous and raised dome, the lateral surface of the jugal ornamented by a prominent ridge defined by multiple tubercles and radiating thread‐like structures, and distinct ornamentation patterns on the rostrum and skull table. Phylogenetic analysis nestsVolcanosuchuswithin Mystriosuchinae, where it forms a sister taxon to (Rutiodon + Leptosuchomorpha) and marks the transition between the basal Parasuchidae and more derived Mystriosuchinae phytosaurs. Evolution of the phytosaur skulls resulted in changes from non‐overlapping nostril and antorbital fenestra to an overlapping state, anteroposterior elongation of the exoccipital–supraoccipital shelf, appearance of a median ridge on the basioccipital, and reduction of the supratemporal fenestra. Considerable faunal overlap of the Tiki Formation is evident with the lower Maleri Formation, which is late Carnian based on the occurrence ofHyperodapedon,ParasuchusandExaeretodon. The Tiki Formation correlates with the Ischigualasto Formation of Argentina, the upper part of the Santa Maria Formation, and the overlying lower Caturrita Formation of Brazil, the Isalo II Beds of Madagascar, Lossiemouth Sandstone of Scotland, and the lower Tecovas Formation of the Chinle Group of North America, and ranges from late Carnian to early/middle Norian.