Temnospondyli

Mehrere Meter große, entfernt an Krokodile erinnernde Lurche, die sogenann-ten Capitosaurier, beherrschten in der Trias die limnischen Ökosysteme in wei-ten Teilen der Welt. Ein Vertreter der Capitosaurier, der aufgrund seiner rund-um geschlossenen Ohröffnung zu den Rundohrlurchen (Cyclotosaurier) gezählt werden kann, wurde vor über 40 Jahren im Schilfsandstein der oberen Trias von Bielefeld entdeckt – ein Novum für Norddeutschland, findet man die Überreste solcher Riesen doch zumeist in triassischen Sedimenten Süddeutschlands. Der Fund wurde jetzt erstmals wissenschaftlich ausgewertet und es zeigte sich, dass es sich um eine neue Art der Gattung Cyclotosaurus handelt.

Abstract:  A partial skull recovered from conglomerates of the Permo-Triassic Buena Vista Formation in Uruguay belongs to a new species, Uruyiella liminea gen. et sp. nov. This species is characterized by a broadly triangular skull with laterally projecting posterior corners, rhytidosteid-like dermal sculpturing, and orbits positioned close to the skull margin. Uruyiella liminea is distinguished from other temnospondyls by a combination of primitive and derived character states, such as the anterior extent of the palatine ramus of the pterygoid, which excludes the ectopterygoid and most of the palatine from the lateral border of the interpterygoid vacuity, and the absence of both tabular horns and otic notches. A phylogenetic analysis places Uruyiella and the enigmatic Early Triassic Laidleria in a clade to which we attach the family name Laidleriidae. The Plagiosauridae and the Laidleriidae form a clade at the base of Dvinosauria, which is the sister group of a clade that includes Stereospondyli and Archegosauroidea. This result is unexpected because Laidleria and Plagiosauridae are nested deeply within Stereospondyli in most phylogenies. The sister-group relationship of Uruyiella and Laidleria suggests that a ghost lineage for the latter genus extends down into the earliest Triassic and perhaps even into the Late Permian, which in turn would suggest survivorship of the Laidleriidae through the Permo-Triassic extinction event.

A new species of the temnospondyl tetrapod, Sclerocephalus stambergi n. sp., is described from
the early Permian deposits of the Boskovice Basin in Moravia (Czech Republic). The length of the skull of the
only known specimen is about 50 mm. Characters including the well-ossified quadrate, septomaxilla and
scapulocoracoid, presence of the maxilla-nasal suture and a free posterolateral margin of the supratemporal suggest
an early adult age. This new species of Sclerocephalus is distinguished from the others on the basis of the following
characters: nasal and maxillary processes of the premaxilla of equal width; absence of the alary process of the
premaxilla; distinct pointed process on the lacrimal between the maxilla and jugal; narrow interclavicle; and very
peculiar tabular presenting a quadrangular, plate-like process extending from its posterolateral portion, an almost
right angle between its lateral and posterior margins, and a long posteromedial process. The new species represents
the smallest and possibly the most basal Sclerocephalus species. The specimen described here sheds new light on the
anatomy and taxonomy of Sclerocephalus. It completes the biodiversity of the tetrapod fauna from the Boskovice
Basin, and our knowledge on the evolution of the European Paleozoic temnospondyls.

The postcranial skeleton of a medium-sized rhinesuchid from the Late Permian Dicynodon Assemblage Zone of South Africa is described. The well-preserved, articulated specimen consists of a partial skull, vertebral column and ribs, pectoral girdle, proximal limb elements, and ventral scales. Interesting features rarely preserved in stereospondyls include the extensive ventral scales and the pectinate anterior border of the interclavicle. SAM-PK-K10021 is of an average size for a rhinesuchid, but possesses a poorly ossified postcranial skeleton in comparison to larger rhinesuchid specimens. The scapulocoracoid lacks an ossified coracoid plate, the humerus lacks a supinator process, and the femur lacks a well-developed internal trochanter and adductor blade. Despite its relatively large size, SAM-PK-K10021 is an immature stage of a large rhinesuchid, thus contributing to our knowledge of the changes to the postcranial skeleton that occur during ontogeny. The assessment of heterochronic processes, especially paedomorphism, in the postcranial skeleton of temnospondyls, and the implications for cladistic analysis, are discussed.

A new benthosuchid Benthosuchus lukyanovi sp. nov. is described from the Early Triassic deposits of the Bludnovo locality in the Vologda Oblast (Yug River Basin). The new species has the largest skull among the known Benthosuchus specimens. Morphological differences between B. lukaynovi and the other representatives of the genus mostly concern the trematosauroid features: the position of the supraorbital canals (sulci supraorbitales) is close to the sagittal suture in the internarial space, presence of weak angular bend, and the strongly elongated posterior Meckelian foramen. The data obtained expand our understanding of the morphological evolution of benthosuchids during the early stages of the formation of the trematosaurid body organization plan.

Trematosaurs represent a peculiar and large clade of stereospondyl temnospondyls with a wide geographic distribution. However, they remain poorly known in Africa, where they are mainly recovered from South Africa (Trematosuchus and Microposaurus) and Madagascar (Wantzosaurus). We report a new and subcomplete skull of the longirostrine Aphaneramma from the Lower Triassic of Madagascar. With a skull length of about 40 cm, this new specimen may account for one of the largest known trematosaurians. It also enlarges the distribution of the genus, which was only known in Spitsbergen (A. rostratum) and Pakistan (A. kokeni) so far. A phylogenetic analysis of the trematosaurians suggests that Aphaneramma is closely related to the North American Cosgriffius. Because of its wide geographical distribution, Aphaneramma represents an important taxon for understanding the migration routes used by trematosaurs in general, and lonchorhynchines in particular. In this sense, the Malagasy occurrence of Aphaneramma provides new insights in the global distribution of the marine vertebrate fauna just after the great Permian-Triassic mass
extinction.

Located in Santa Fe County, New Mexico, USA, the Lamy amphibian quarry is a Late Triassic (Adamanian)
bonebed stratigraphically low in the Garita Creek Formation of the Chinle Group. Well known for its mass
accumulation of metoposaurid amphibians, it was initially interpreted as a drought-induced death
assemblage. Based on microstratigraphic and sedimentological studies, additional and extensive collecting
at the quarry and a revised understanding of the bonebed, we provide a detailed taphonomic analysis of the
Lamy amphibian quarry that identifies it as a low diversity multitaxic and monodominant bonebed in
pedogenically modified floodplain mudstone. The Lamy bonebed shows no evidence of drought and is
characterized by a high density of completely dissociated bones that show clear alignment by current and
sorting (enrichment of Voorhies Group II and III elements). The bones show no significant abrasion or
weathering (stage 0), preserve virtually no evidence of scavenging and show no evidence of trampling. Based
on skull lengths, the metoposaurid assemblage has a type I survivorship curve and lacks juveniles. We thus
posit that the following sequence of events formed the Lamy amphibian bonebed: (1) aggregation (cause
unknown) of a large number of metoposaurid amphibians at a site different from the location of the bonebed,
though not distant; (2) catastrophic mass mortality; (3) complete disarticulation and disassociation of the
skeletons; and (4) rapid transport of the disarticulated bones onto a floodplain surface that was undergoing
pedogenesis. The Lamy amphibian bonebed is representative of the Late Triassic metoposaurid bonebeds from
Morocco and the western USA, which are monodominant and nearly monotaxic. They indicate that
aggregation (probably of breeding populations) and mass death of metoposaurids were relatively common
across the riverine floodplains of Late Triassic Pangea.

ABSTRACT Temnospondyls from the Middle–Late Triassic of Madagascar are problematic and scarce: ‘Metoposaurus hoffmani’ was erected on the basis of poor material, and this taxon has never been revised. Other remains were also reported and assigned to Temnospondyli indet., but they have never been described, nor figured. Here, we (re)describe in detail this historical material from the Folakara area of Madagascar (Isalo Group, Morondava Basin): the specimens include cranial and postcranial remains, most of them being referred to Metoposauridae indet. and a few to Stereospondyli indet. We also confirm that ‘M. hoffmani’ is a nomen dubium owing to the absence of any clear autapomorphy of the fragmentary type material. The material referred here to Metoposauridae indet. is incorporated in an updated paleobiogeographic analysis of the group: interestingly, it suggests a connection with Indian metoposaurids during the Late Triassic.

"Temnospondyls are the most diverse, speciose, and long-lived
group of early tetrapods. Whereas their first record in the late
Paleozoic is restricted to Euramerica, during the early Mesozoic
they reached an almost worldwide distribution. The large,
crocodiliform stereospondyls in particular experienced a phase
of rapid dispersal across vast areas of the Pangean supercontinent
(Schoch, 2000). Rich deposits have been reported from the
Early and Middle Triassic of Arizona, Argentina, Brazil, Central
Europe, European Russia, South Africa, India, Madagascar,
and Australia (Schoch and Milner, 2000). However, in East Asia
their remains are still very rare and utterly fragmentary (Lucas
and Hunt, 1993; Liu and Wang, 2005). At the same time, the paleogeography
of the eastern Pangean margin is still rather poorly
understood, which hampers a clear picture of migratory patterns
of aquatic tetrapods during the early Mesozoic. In this paper, we
report the occurrence of a capitosauroid taxon in the Lower Triassic
of northeastern Honshu, Japan. This is not only the first
temnospondyl from the Japanese islands but also forms the first
non-marine vertebrate from the Triassic of Japan, which suggests
a migration of aquatic tetrapods across the land bridge between
the North China block and the ancient Japanese islands in pre-
Jurassic time."

Temnospondyl amphibians are a large and diverse group of early tetrapods, whose paleohistology has been incompletely studied. Here, humeri of Micropholis stowi and Lydekkerina huxleyi from the Karoo Basin of South Africa (Katberg Formation) were thin-sectioned for paleohistological analysis. Diaphyseal bone histology of both taxa exhibits a convergence to fibrolamellar tissue and an absence of lines of arrested growth; additionally, medullary cavities free of
trabeculae support terrestrial lifestyles in both Micropholis and Lydekkerina. The presence of azonal tissue in Micropholis is unlike that of other dissorophoids or extant caudatans, suggesting an adaptation to local conditions in the Early Triassic of the Karoo Basin, as well as a complicated and incompletely studied pattern of histological evolution in dissorophoids. Additionally, the propodial histology of these and 12 other taxa were assessed through different broad-scale phylogenetic hypotheses for Temnospondyli. Results reveal convergence towards sustained, non-cyclical growth and an absence of lines of arrested growth in the diaphyses of Early Triassic temnospondyls. The optimization of histological traits on to existing phylogenetic hypotheses is equally parsimonious between the different topologies. Homoplasy among histological characters suggests that evolutionary history in this group is overshadowed by  evelopmental plasticity in bone microstructure, potentially due to environmental and biomechanical constraints. However, the interpretation of these data is limited by small
sample size, and increased sampling is required to validate the patterns revealed in this study.

Description of the postcranial skeleton of the basal stereospondyl amphibian Lydekkerina huxleyi from new material shows it to be heavily ossified with large processes for muscle attachment and well-developed articulation surfaces. The structure of the postcranial skeleton implies a substantial capability for terrestrial locomotion, rather than a primarily aquatic existence as has been suggested for most other stereospondyls. The postcranial skeleton is most similar to that of Uranocentrodon and the Archegosauroidea, and is unlike that of the poorly ossified, more derived stereospondyls and Dvinosauria. The postcranial skeleton does not display any of the particular apomorphies of the fully ossified Permian terrestrial temnospondyls. Cladistic analysis using the postcranial data obtained in this study indicates that within the Stereospondyli Lydekkerina huxleyi is neither a member of the Rhinesuchidae nor the Mastodonsauroidea, rather the Lydekkerinidae are a separate taxon.

Capitosaurs were the largest and homogeneous group of Triassic temnospondyl amphibians with cosmopolitan distribution. However, their interrelationships are debated. The first capitosaur cranial remains found in the Iberian Peninsula were assigned to Parotosuchus; herein, a re−description of this material, together with information on other remains re−
covered from the same site, enables us to classify them as a new genus: Calmasuchus acri gen. et sp. nov. (Amphibia: Temnospondyli) from the early−to−middle Anisian (early Middle Triassic). This capitosaur had a combination of plesiomorphic and non−plesiomorphic characters, such as posterolaterally directed tabular horns, paired anterior palatal vacuities, and unique morphology of the lower jaw. By cladistic analysis, we propose a new phylogeny for the monophyletic capitosaurs. In the analysis, Capitosauria is supported by seven synapomorphies. Wetlugasaurus is the most basal member of the clade. The score of the Russian taxon Vladlenosaurus alexeyevi resulted in a clade including Odenwaldia and the latter taxa. The Madagascarian Edingerella is the sister taxon of Watsonisuchus. Finally, Calmasuchus acri, the new taxon described here, appears as a more derived form than Parotosuchus. The new genus is the sister taxon of the Cyclotosaurus–Tatrasuchus and Eryosuchus Mastodonsaurus clades.

Located in Santa Fe County, New Mexico, USA, the Lamy amphibian quarry is a Late Triassic (Adamanian) bonebed stratigraphically low in the Garita Creek Formation of the Chinle Group. Well known for its mass accumulation of metoposaurid amphibians, it was initially interpreted as a drought-induced death assemblage. Based on microstratigraphic and sedimentological studies, additional and extensive collecting at the quarry and a revised understanding of the bonebed, we provide a detailed taphonomic analysis of the Lamy amphibian quarry that identifies it as a low diversity multitaxic and monodominant bonebed in pedogenically modified floodplain mudstone. The Lamy bonebed shows no evidence of drought and is characterized by a high density of completely dissociated bones that show clear alignment by current and sorting (enrichment of Voorhies Group II and III elements). The bones show no significant abrasion or weathering (stage 0), preserve virtually no evidence of scavenging and show n...