Exceptional endocranium and middle ear of Stanocephalosaurus (Temnospondyli: Capitosauria) from the Triassic of Algeria revealed by micro-CT scan, with new functional interpretations of the hearing system

Arbez, Thomas; Dahoumane, Anissa; Steyer, Jean‐Sébastien

doi:10.1093/zoolinnean/zlw007

Cited by 11 publications

(9 citation statements)

References 42 publications

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“…Below this ventral extension of the tabular and dorsolaterally to the exoccipital column, a shallow (1-2 mm) and small ovoid (3 x 4 mm) depression is visible: this post-temporal depression may be homologous to the post-temporal fenestra observed in other stegocephalians, such as temnospondyls (e.g. Arbez et al, 2017).…”

Section: Palate (Fig 4 5 6b)mentioning

confidence: 81%

Laosuchus nagagen. et sp. nov., a new chroniosuchian from South-East Asia (Laos) with internal structures revealed by micro-CT scan and discussion of its palaeobiology

Arbez¹,

Sidor

Steyer³

2018

Journal of Systematic Palaeontology

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Chroniosuchians were a clade of non-amniotic tetrapods known from the Guadalupian (middle Permian) to Late Triassic, mainly from Russia and China. The rarity of complete or articulated remains means that relatively little is known about this group in terms of its anatomy, palaeobiology, or evolutionary history. Based on a nearly complete skull with a left hemimandible, we describe the first chroniosuchian from Laos from rocks preserving the Permian-Triassic boundary in the Luang Prabang Basin, which is located on the tectonic Indochina Block. This specimen is referred to a new genus and species, Laosuchus naga, based on numerous diagnostic features, including an extremely reduced pineal foramen; absence of palatal dentition; well-developed transverse flange of the pterygoid that contacts the maxilla; internal crest on and above the dorsal side the palate; otic notch closed by the tabular horn and the posterior part of the squamosal, forming a continuous wall; thin and high ventromedial ridge on parasphenoid. A phylogenetic analysis of 51 characters and 25 taxa reveals a basal position for Laosuchus naga among Chroniosuchia. In addition, CT scan data reveal internal structures and provide new insights about the anatomy and palaeobiology of chroniosuchians. Laosuchus naga was likely amphibious and spent most of its time in water, rather than in terrestrial environments. As chroniosuchians are nonmarine tetrapods previously known on the North China Block, South China Block, and Laurussia, the occurrence of Laosuchus naga on the Indochina Block supports the hypothesis of physical connections between all these tectonic plates by the time of the Permo-Triassic boundary.

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Section: Palate (Fig 4 5 6b)mentioning

confidence: 81%

Laosuchus nagagen. et sp. nov., a new chroniosuchian from South-East Asia (Laos) with internal structures revealed by micro-CT scan and discussion of its palaeobiology

Arbez¹,

Sidor

Steyer³

2018

Journal of Systematic Palaeontology

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“…On the anterior side of the exoccipital, between the base of the processus lamellosus and paroticus, there is a weak rounded depression. Due to this emplacement and by comparison with Stanocephalosaurus amenasensis (Arbez et al 2017), it could represent the opisthotic bone.…”

Section: Occipital Regionmentioning

confidence: 95%

“…Moreover, in species where the stapes, the otic capsule and the epipterygoid are preserved, these bones possess few and slight contacts with surrounding bones. For example, in S. amenasensis the epipterygoid is only linked to the pterygoid and likely by a cartilaginous contact (Arbez et al 2017). As explained above, because of their weak ossification these elements are easily lost during fossilisation.…”

Section: Preservation Of Internal Structuresmentioning

confidence: 99%

Cranial anatomy of the Early Triassic trematosaurine Angusaurus (Temnospondyli: Stereospondyli): 3D endocranial insights and phylogenetic implications

et al. 2018

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Background Trematosaurines are a widespread group of early tetrapods (Temnospondyli, Stereospondyli) known from all continents except South America and Antarctica. They radiated rapidly during the Early Triassic just after the End Permian mass extinction and are of interest to understand the recovery of the ecosystems just after extinction. Trematosaurines disappeared during the Late Triassic. Objective Herein, a re-description of the genus Angusaurus is presented based on a new specimen. This genus is known from the Early Olenekian (Early Triassic) of Russia and comprises four valid species, although the diagnostic characters that deine some of them are vague and controversial. Methods The new specimen described, using MicroCT scanner and 3D digital modeling, sheds light on the anatomical details of the external and inner cranial structure, and provides new details of the neurocranium as well as the ontogeny of this genus. Results and Discussion A cladistic analysis of trematosaurines (including most trematosauroids) confirms the problematic nature of some Angusaurus species and provides a basis for detailed discussion about the phylogeny of trematosaurines.

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“…However, in contrast to all other known specimens of Sclerocephalus spp., both stapes of the holotype of S. concordiae are firmly attached to the parasphenoid, which is well exposed on both sides, and the tight suturing is also revealed by micro-CT data. An articulation of the stapes with the parasphenoid is reported for various stereospondyls (Schoch and Milner, 2000;Arbez et al, 2017). Sutured or fused stapes (to the parasphenoid) have been reported in Lyrocephalus euri Wiman, 1913(Säve-Söderbergh, 1936, and arguably Eryops megacephalus (Sawin, 1941) and Tersomius texensis Case, 1910(Carroll, 1964.…”

Section: Sclerocephalus Concordiae New Speciesmentioning

confidence: 99%

A new species of Sclerocephalus with a fully ossified endocranium gives insight into braincase evolution in temnospondyls

Schoch¹,

Sobral²

2021

J. Paleontol.

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The late Paleozoic temnospondyl Sclerocephalus formed an aquatic top predator in various central European lakes of the late Carboniferous and early Permian. Despite hundreds of specimens spanning a wide range of sizes, knowledge of the endocranium (braincase and palatoquadrate) remained very insufficient in Sclerocephalus and other stereospondylomorphs because even large skulls had unossified endocrania. A new specimen from a stratigraphically ancient deposit at St. Wendel in southwestern Germany is recognized as representing a new taxon, S. concordiae new species, and reveals a completely ossified endocranium. The sphenethmoid was completely ossified from the basisphenoid to the anterior ethmoid region, co-ossified with the parasphenoid, and the basipterygoid joint was fully established. The pterygoid bears a slender, S-shaped epipterygoid, which formed a robust pillar lateral to the braincase. The massive stapes was firmly sutured to the parasphenoid. In the temnospondyl endocranium, character evolution involved various changes in the epipterygoid region, which evolved distinct morphologies in each of the major clades. UUID: http://zoobank.org/5e6d2078-eacf-4467-84cf-a12efcae7c0b

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Exceptional endocranium and middle ear of Stanocephalosaurus (Temnospondyli: Capitosauria) from the Triassic of Algeria revealed by micro-CT scan, with new functional interpretations of the hearing system

Cited by 11 publications

References 42 publications

Laosuchus nagagen. et sp. nov., a new chroniosuchian from South-East Asia (Laos) with internal structures revealed by micro-CT scan and discussion of its palaeobiology

Laosuchus nagagen. et sp. nov., a new chroniosuchian from South-East Asia (Laos) with internal structures revealed by micro-CT scan and discussion of its palaeobiology

Cranial anatomy of the Early Triassic trematosaurine Angusaurus (Temnospondyli: Stereospondyli): 3D endocranial insights and phylogenetic implications

A new species of Sclerocephalus with a fully ossified endocranium gives insight into braincase evolution in temnospondyls

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