Understanding the origin and evolution of unique mammalian respiratory system hinges on our knowledge osteological changes in pectoral apparatus (i.e., scapulocoracoid, cleithrum, clavicle, interclavicle, sternum) throughout synapsid fossil record. Among non-mammalian therapsids, documentation this anatomy is woefully incomplete, with groups such as dinocephalians gorgonopsians remaining poorly documented. Here we provide a detailed anatomical description an articulated sternum interclavicle...

Abstract Recumbirostra is a clade of heavily modified, superficially lizard‐like tetrapods that were originally interpreted as ‘microsaurian lepospondyls’ unrelated to the amniote crown. However, recent work has placed within Reptilia, based on many similarities between braincase and postcranium recumbirostrans with early reptiles. Here, Permian hapsidopareiid recumbirostran Hapsidopareion lepton re‐described using high‐resolution μCT data three individuals across distinct ontogenetic...

Redescription of the holotype specimen Cephalerpeton ventriarmatum Moodie, 1912, from Middle Pennsylvanian (Moscovian) Francis Creek Shale Mazon Creek, Illinois, confirms that it is a basal eureptile with close postcranial similarities to other protorothyridids, such as Anthracodromeus and Paleothyris. The skull long lightly built, large orbits dorsoventrally short mandible similar most eureptiles. Two specimens referred previously cf. C. approximately coeval Linton, Ohio, locality differ...

Abstract ‘Microsaurs’ are traditionally considered to be lepospondyl non‐amniotes, but recent analyses have recovered a subset of ‘microsaurs’, the fossorially adapted Recumbirostra, within Amniota. This novel conclusion highlights need for additional work evaluate these competing hypotheses with aim refining phylogenetic position ‘microsaurs’. Of particular importance in this regard is placement potential close relatives recumbirostrans determine whether they support an early, stepwise...

Abstract The group of Permo-Carboniferous tetrapods known as Recumbirostra have recently been hypothesized to represent the earliest radiation fossorial reptiles. Therefore, understanding anatomy and diversity this clade is essential origin early evolution amniotes. Here, we redescribe diminutive ‘microsaur’ Odonterpeton triangulare from Moscovian-age deposit Linton, Ohio, revealing new details on structure cranium palate, including presence a conspicuous transverse flange pterygoid, which...

Abstract The Carboniferous (Pennsylvanian; 309–307 Mya) ‘Mazon Creek’ Lagerstätte produces some of the earliest tetrapod fossils major Palaeozoic lineages. Previously, Mazon Creek record lysorophians was known from a single poorly preserved specimen consisting only partial vertebral column. Here we describe new, virtually complete lysorophian genus and species, Infernovenator steenae gen. & sp. nov. on basis unique combination characters, including near circumorbital series retention...

Abstract The Carboniferous (Pennsylvanian; 309–307 Mya) ‘Mazon Creek’ Lagerstätte produces some of the earliest tetrapod fossils major Palaeozoic lineages. Previously, Mazon Creek record ‘microsaurs’ was known from a single specimen. However, lack key anatomy, such as skull, precluded confident taxonomic assignment, thus only suggested affinity to microbrachimorph ‘microsaur’ Hyloplesion determined. Recently several new specimens collected have come light, which recumbirostran affinity. Here...

The Carboniferous Pennsylvanian-aged (309–307 Ma) Mazon Creek Lagerstätte produces some of the earliest fossils major Palaeozoic tetrapod lineages. Recently, several new specimens collected from have come to light, including fossorially adapted recumbirostrans. Here, we describe a long-bodied recumbirostran, Joermungandr bolti gen. et sp. nov., known single part and counterpart concretion bearing virtually complete skeleton. Uniquely, preserves full suite dorsal, flank ventral dermal scales,...

A new skeleton of the exceedingly rare, late Carboniferous eureptile Anthracodromeus longipes ( Carroll and Baird, 1972 ), reveals presence a reduced phalangeal count in manus pedes uniquely recurved unguals. With these data, we quantitatively evaluate locomotor ecology using morphometric analyses proportions, ungual curvature, shape. Our findings indicate that anatomy likely facilitated scansorial clinging to some degree via distally unguals increased surface area large pes. This suggests...

Herbivory evolved independently in several tetrapod lineages during the Late Carboniferous and became more widespread throughout Permian Period, eventually leading to basic structure of modern terrestrial ecosystems. Here we report a new taxon edaphosaurid synapsid based on two fossils recovered from Moscovian-age cannel coal Linton, Ohio, which interpret as an omnivore-low-fibre herbivore. Melanedaphodon hovaneci gen. et sp. nov. provides earliest record date is one oldest known synapsids....

Earliest Pennsylvanian (Bashkirian) vertebrate fossil assemblages of the Joggins Formation (Cumberland Group) Nova Scotia, Canada, have long been noted for unique representation earliest known crown amniotes, but overall fauna remains poorly understood. The vast majority vertebrates historically assigned to Microsauria, a group originally established by Dawson specifically accommodate abundant, diminutive fossils Formation. As Microsauria concept has evolved, some taxa (e.g. eureptile...

The Pennsylvanian-aged (309–307 Ma) Lagerstatte in the Francis Creek Shale at Mazon Creek, Illinois, has produced some of most exceptional metazoan fossils, including numerous invertebrate clad...

Neural spine hyper-elongation in tetrapods is a unique morphological adaptation that creates dorsal sail. While this extreme morphology has appeared several times the evolutionary history of tetrapods, it was first experimented with by non-mammalian synapsid group known as ‘Pelycosaurs’, famously represented Permian apex predator Dimetrodon. Here we provide new fossil data tracing back evolution innovation to initial Carboniferous radiation clade. We describe hyper-elongated neural belonging...

ABSTRACTFossils referable to the gorgonopsian Gorgonops sp. and dicynodont Endothiodon are described from Permian Madumabisa Mudstone Formation of Mid-Zambezi Basin southern Zambia. Specimens former taxon conform recent diagnoses genus (e.g., five postcanine teeth, transverse flange pterygoid backswept, postorbital bar rugose moderately expanded), but differ slightly South African material in some respects reduced dentition on pterygoid). Fossils latter less complete, show diagnostic...

Although the cranial anatomy of lysorophian tetrapod Brachydectes has been reported in detail recently, many attributes group are inadequately known, and systematics remain unclear. One under-described aspect genus is development variation ornamentation. Whereas smallest skulls (< 5 mm length) lack sculpturing, ornamentation increases progressively larger specimens conspicuous largest (> 30 skull individuals. It includes rugose ornament on anterior roof elements (frontals parietals)...

A new specimen of Batrachichnus salamandroides was recovered from a recently discovered fossil-bearingsite situated along the southern shore Grand Lake, New Brunswick, among diverse ichnofaunal assemblagefrom Middle Pennsylvanian (upper Bolsovian; lower Moscovian), upper Minto Formation. The identity ofthe tracemaker this ichnogenus is reinterpreted as composite various late Paleozoic tetrapod taxa, basedon similarities postcranial skeletons, notably that manus and pes, both temnospondyls...

The Devonian marine strata of southwestern Ontario, Canada, have been well documented geologically, but their vertebrate fossils are poorly studied. Here we report a new onychodontiform (Osteichthyes, Sarcopterygii) Onychodus eriensis n. sp. from the Dundee Formation (Eifelian–Givetian boundary, 390–387 Ma) Ontario represented by two well-preserved lower jaws. most complete specimen consists large (28 cm), right jaw with dentition present. dentary has 50 teeth, not including parasymphysial...

Abstract Amphibamiform temnospondyls are at the forefront of discourse surrounding modern amphibian evolutionary origins. Here we present a new amphibamiform, Kermitops gratus gen. et sp. nov., from Lower Clear Fork Formation Early Permian Texas. reveals mosaic features shared with other amphibamiforms and possesses unique characteristics, including an internarial fontanelle formed by premaxillae without contribution nasals. It possibly basioccipital that contributes to occipital condyle,...

Brachyopoids represent a diverse and late surviving temnospondyl group, lasting until the Early Cretaceous. Here, we report on brachyopoid material previously assigned to Hadrokkosaurus bradyi that represents distinct taxon, characterised by smaller number of large, robust mandibular teeth, feature rarely observed in other temnospondyls. We also revisit an angular referred potentially belonging taxa present Middle Triassic North America. In light abundance possible from , express need...

Abstract One of the earliest discoveries Permo-Carboniferous terrestrial vertebrates in North America occurred 1875 along Horseshoe Bend, a cutbank on Salt Fork Vermilion River west Danville, County, east-central Illinois. The discovery was soon eclipsed by description similar but much more complete remains from Lower Permian Texas 1878. deposit itself obliterated slumping and erosion 1900s has not been collected since despite repeated efforts. Previously unreported outcrop records...

Embolomerous tetrapods, moderately-sized to large aquatic predators, form a major faunal constituent of Permo-Carboniferous tetrapod communities. Embolomeres are recognized by their distinct circular, bipartite vertebrae. Although traditionally classified as stem amniotes, the inclusion embolomeres within crown group has recently been challenged. Despite group’s phylogenetic uncertainty, provide an important record long-lived lineage, spanning “Romer’s Gap” through early Permian. Here, we...