Antarctosuchus polyodon, a new Temnospondyl from the Middle Triassic of Antarctica and Evidence for the Provincialization of the Temnospondyl Assemblages of Gondwana

I've always been interested in the Triassic rocks of Antarctica since as a work-study student at the Museum of Northern Arizona in the 1990s, I was tasked with returning a loan back to the American Museum of Natural History. Turns out it was Edwin Colbert's collection of material from Antarctica.  I was spellbound handling and packing away leaves of Glossopteris and specimens of Thrinaxodon and Dicynodon. These were specimens I had read about when I was younger that helped nail down the theory of plate tectonics, and here I was handling them and packing them for shipment (I hope they made it OK). In graduate school in the late 1990s we were tasked with writing a mock NSF proposal.  Mine dealt with collecting fossils in the Transantarctic Mountains and I'm happy to say it was the only one 'funded' by the professor, but of course I did not really get to go. As a result I'm always envious when  I read about Antarctic work.

This is a paper in the new issue of the Journal of Vertebrate Paleontology describing a new temnospondyl from the Middle Triassic of Antarctica.  This new taxon, Antarctosuchus polyodon, is based on a well preserved skull and a reconstruction is provided below courtesy of Christian Sidor.

This new taxon and its phylogenetic relationships suggests that the Gonwanan temnospondyl faunal assemblages were more provincial than the synapsid assemblages.

Sidor, C. A., Steyer, J. S., and W. R. Hammer. 2014. A new capitosaurid temnospondyl from the Middle Triassic Upper Fremouw Formation of Antarctica. Journal of Vertebrate Paleontology 34(3):539-548. DOI:10.1080/02724634.2013.808205

Abstract - We describe a new capitosauroid temnospondyl, Antarctosuchus polyodon, gen. et sp. nov., on the basis of a large and relatively complete skull from the upper Fremouw Formation of Antarctica. The new species is characterized by its possession of numerous, extremely small maxillary, palatine, and ectopterygoid teeth, a dental pattern that suggests specialization on small prey items, possibly invertebrates. The taxon is also characterized by a parachoanal tooth row that extends far posterior to the choana and occipital condyles set close to the midline. A combination of features, including a flat skull and low occiput together with well-developed sensory canals, suggests an aquatic lifestyle. We address the phylogenetic relationships of Antarctosuchus by adding it to a recent cladistic analysis of Capitosauria. The revised data set includes 27 taxa and 53 characters. The results of this analysis place Antarctosuchus within a clade of derived Triassic stereospondyls as the sister taxon to Paracyclotosaurus crookshanki from the Triassic Denwai Formation of India. To date, the upper Fremouw Formation has yielded two endemic temnospondyl species (viz., Kryostega collinsoni and Antarctosuchus polyodon), although indeterminate remains referred to benthosuchids and a cranial fragment assigned to Parotosuchus sp. have also been noted. In contrast to the broadly distributed therapsid taxa recognized from the Middle Triassic of Antarctica (e.g., Cynognathus, Diademodon), the temnospondyl fauna suggests more limited interchange with other coeval southern Pangean basins (e.g., Karoo, Luangwa, Ruhuhu, Waterberg).

New Information on the Temnospondyl Calamops paludosus from the Upper Triassic of Pennsylvania

Sues, H.-D., and R. R. Schoch. 2013. Anatomy and phylogenetic relationships of Calamops paludosus (Temnospondyli, Stereospondyli) from the Triassic of the Newark Basin, Pennsylvania. Journal of Vertebrate Paleontology 33:1061-1070. DOI:10.1080/02724634.2013.759120

Abstract - The holotype of the large temnospondyl Calamops paludosus is the oldest known tetrapod fossil from the Triassic of the Newark basin in Pennsylvania. Although it is usually placed in Metoposauridae, its affinities have remained unknown since its original description because the unique specimen had never been prepared. Preparation and casting of the specimen, which comprises three pieces of a left mandibular ramus, now permits detailed anatomical description of the jaw and assessment of its affinities. Calamops paludosus is a valid taxon of trematosauroid temnospondyls that can be diagnosed by several autapomorphies. It represents one of the geologically youngest known records of long-snouted trematosaurs and the first record of these temnospondyls from the Late Triassic of North America.

High Environmental and Metabolic Plasticity as a Successful Evolutionary Strategy in a Long-lived Homeostatic Triassic Temnospondyl.

Sanchez S., and R. R. Schoch. 2013. Bone histology reveals a high environmental and metabolic plasticity as a successful evolutionary strategy in a long-lived homeostatic Triassic temnospondyl. Evolutionary Biology (early online) DOI: 10.1007/s11692-013-9238-3

Abstract - Evolutionary stasis (long-term stability of morphology in an evolving lineage) is a pattern for which explanations are usually elusive. The Triassic tetrapod Gerrothorax pulcherrimus, a gill-bearing temnospondyl, survived for 35 million years in the Germanic Basin of Central Europe persisting throughout the dinosaur-dominated Late Triassic Period. This evolutionary stasis coincides with the occurrence of this species in a wide range of habitats and environmental conditions. By the combination of palaeoecological and palaeohistological analyses, we found great ecological flexibility in G. pulcherrimus and present substantial evidence of developmental and
metabolic plasticity despite the morphological stasis. We conclude that G. pulcherrimus could show the capacity to settle in water bodies too harsh or unpredictable for most other tetrapods. This would have been made possible by a unique life history strategy that involved a wide reaction norm, permitting adjustment to fluctuating conditions such as salinity and level of nutrients. Growth rate, duration of juvenile period, age at maturity, and life span were all subject to broad variation within specimens of G. pulcherrimus in one single lake and in between different lakes. In addition to providing a better understanding of fossil ecosystems, this study shows the potential of such a methodology to encourage palaeobiologists and evolutionary biologists to consider the mechanisms of variation in extant and fossil organisms by using a similar time-scope reference.

Two New Temnospondyl Papers - Phylogeny of Major Clades and Suction Feeding in Gerrothorax

Schoch, R. R. 2013. The evolution of major temnospondyl clades: an inclusive phylogenetic analysis. Journal of Systematic Palaeontology DOI:10.1080/14772019.2012.699006http://www.tandfonline.com/doi/full/10.1080/14772019.2012.699006

Abstract - Phylogenetic analysis of a large dataset (72 taxa, 212 characters) focuses on the in-group relationships of temnospondyls, the largest lower tetrapod clade. Representatives of all clades and grades were considered, spanning the entire stratigraphical range of temnospondyls from the Early Carboniferous through to the Early Cretaceous. Several major groups are defined phylogenetically (node or branch-based) rather than by apomorphies. The following groups were unequivocally found to be monophyletic: Edopoidea (node), Dvinosauria (stem, excl. Brachyopidae), Dissorophoidea (node), Eryopidae (stem), and Stereospondyli (node). The latter encompass three well-defined, branch-based taxa: Rhinesuchidae, Trematosauria and Capitosauria. Trematosauria (stem) contain Trematosauroidea (node), which includes the classic trematosaurids, metoposaurids, and possibly part of the rhytidosteids (Peltostega) but their in-group relationships remain unsettled; most other short-snouted stereospondyls (chigutisaurids, brachyopids, Laidleria and the plagiosaurids) are probably monophyletic and likely nest in some form with trematosauroids. Capitosauria (stem) include the Capitosauroidea (node) spanned by Parotosuchus and Mastodonsaurus, with the successive stem taxa Edingerella, Benthosuchus, Wetlugasaurus and Watsonisuchus. In all variant analyses, edopoids form the basalmost temnospondyl clade, followed by a potential clade (or grade) of small terrestrial taxa containing Balanerpeton and Dendrerpeton (‘Dendrerpetontidae’). All taxa higher than Edopoidea are suggested to form the monophyletic stem taxon Eutemnospondyli, tax. nov. The remainder of Temnospondyli fall into four robust and undisputed clades: (1) Dvinosauria; (2) Zatracheidae plus Dissorophoidea; (3) Eryopidae; and (4) Stereospondyli. These taxa are together referred to as Rhachitomi (node). Eryopidae and Stereospondylomorpha are probably monophyletic, here referred to as Eryopiformes (tax. nov.). The position of Dissorophoidea + Zatracheidae is still ambiguous; it may either form the sister taxon of Dvinosauria, or nest between Dvinosauria and Eryopiformes, whereas there is no support for Euskelia (Dissorophoidea + Eryopidae) after basal taxa of each clade are better understood.



Witzmann, F. and R. R. Schoch. 2012. Reconstruction of cranial and hyobranchial muscles in the Triassic temnospondyl Gerrothorax provides evidence for akinetic suction feeding. Journal of Morphology DOI: 10.1002/jmor.20113 http://onlinelibrary.wiley.com/doi/10.1002/jmor.20113/abstract

Abstract - The cranial and hyobranchial muscles of the Triassic temnospondyl Gerrothorax have been reconstructed based on direct evidence (spatial limitations, ossified muscle insertion sites on skull, mandible, and hyobranchium) and on phylogenetic reasoning (with extant basal actinopterygians and caudates as bracketing taxa). The skeletal and soft-anatomical data allow the reconstruction of the feeding strike of this bottom-dwelling, aquatic temnospondyl. The orientation of the muscle scars on the postglenoid area of the mandible indicates that the depressor mandibulae was indeed used for lowering the mandible and not to raise the skull as supposed previously and implies that the skull including the mandible must have been lifted off the ground during prey capture. It can thus be assumed that Gerrothorax raised the head toward the prey with the jaws still closed. Analogous to the bracketing taxa, subsequent mouth opening was caused by action of the strong epaxial muscles (further elevation of the head) and the depressor mandibulae and rectus cervicis (lowering of the mandible). During mouth opening, the action of the rectus cervicis muscle also rotated the hyobranchial apparatus ventrally and caudally, thus expanding the buccal cavity and causing the inflow of water with the prey through the mouth opening. The strongly developed depressor mandibulae and rectus cervicis, and the well ossified, large quadrate-articular joint suggest that this action occurred rapidly and that powerful suction was generated. Also, the jaw adductors were well developed and enabled a rapid mouth closure. In contrast to extant caudate larvae and most extant actinopterygians (teleosts), no cranial kinesis was possible in the Gerrothorax skull, and therefore suction feeding was not as elaborate as in these extant forms. This reconstruction may guide future studies of feeding in extinct aquatic tetrapods with ossified hyobranchial apparatus.

Skull Mechanics of Capitosaurs (Amphibia: Temnospondyli)

Fortuny, J., Marcé-Nogué, J., Gil, L. and Galobart, À. 2012. Skull Mechanics and the Evolutionary Patterns of the Otic Notch Closure in Capitosaurs (Amphibia: Temnospondyli). The Anatomical Record (advance online publication) doi: 10.1002/ar.22486 http://onlinelibrary.wiley.com/doi/10.1002/ar.22486/abstract

Abstract - Capitosaurs were among the largest amphibians that have ever lived. Their members displayed an amphibious lifestyle. We provide new information on functional morphology data, using finite element analysis (FEA) which has palaeoecological implications for the group. Our analyses included 17 taxa using (2D) plate models to test four loading cases (bilateral, unilateral and lateral bitings and skull raising system simulation). Our results demonstrates that, when feeding, capitosaurs concentrated the stress at the circumorbital region of the capitosaur skull and cranial sutures probably played a key role in dissipating and absorbing the stress generated during biting. Basal members (as Wetlugasaurus) were probably less specialized forms, while during Middle- and Late Triassic the group radiated into different ecomorphotypes with closed otic notch forms (as Cyclotosaurus) resulting in the strongest skulls during biting. Previous interpretations discussed a trend from an open to closed otic notch associated with lateral repositioning of the tabular horns, but the analysis of the skull-raising system reveals that taxa exhibiting posteriorly directed tabular horns display similar results during skull raising to those of closed otic notch taxa. Our results suggest that various constraints besides otic notch morphology, such as the elongation of the tabular horns, snout length, skull width and position, and size of the orbits affect the function of the skull. On the light of our results, capitosaur skull showed a trend to reduce the stresses and deformation during biting. Capitosaurs could be considered crocodilian analogues as they were top-level predators in fluvial and brackish Triassic ecosystems.

Arachana nigra, a New Temnospondyl from the Permo-Triassic of Uruguay

Piñeiro, G., Ramos, A., and C. Marsicano. 2012. A rhinesuchid-like temnospondyl from the Permo-Triassic of Uruguay. Compte Rendus Palevol 11:65-78. http://dx.doi.org/10.1016/j.crpv.2011.07.007

 

Abstract - A new temnospondyl species, Arachana nigra, from the Permo-Triassic Buena Vista Formation of Uruguay is described. The holotypic and only known specimen consists of an almost complete skull lacking most of the snout, the tabular horns and the posterolateral corners of the skull table. As with other specimens from the same unit, Arachana shows a transitional morphology. It shares several characters with rhinesuchids, such as the large size and the general shape of the skull, orbits positioned slightly posterior to the skull roof mid-length, a coarsely pitted dermal ornamentation lacking pustules, and a smoothly convex cheek contour. The palatal ramus of the pterygoid suturing with the vomer, and excluding the palatine and ectopterygoid from the margin of the interpterygoid vacuity, and the presence of a small basioccipital, visible in both occipital and ventral view, also resemble the conditions found in rhinesuchids and other basal temnospondyls. Other characters present in Arachana, however, are commonly found in lydekkerinids, but are absent in almost all rhinesuchids: supratemporal excluded from otic notch; supraorbital and infraorbital sensory sulci encroaching the lacrimal, although lacking a step-like lacrimal flexure; otic notch not deeply incised; post-temporal fenestra large and rounded; occipital condyles well-separated from each other; palatine tooth row behind the palatine tusk reduced; pterygoid corpus slightly ornamented; and presence of an interorbital depression. This combination of primitive and derived characters is consistently present in most components of the Buena Vista fauna, which could thus be transitional between typical Permian and Triassic tetrapod communities found elsewhere. The location of the PTB in the Uruguayan sequence is controversial, mainly due to the lack of clear faunal correlations with other well-known sequences, such as those of southern Africa and Russia. Moreover, the mosaic-like character combinations in most of the recorded tetrapods ally them to both Triassic and Paleozoic groups, and this has complicated even more the possibility of age assignment. Transitional faunas associated with the PTB, such as the Russian Uppermost Permian faunas, could be equivalent to the unique Colonia Orozco fauna. If true, this scenario will substantially change estimates about survivorship rates, suggesting a speciation rate increase in temnospondyls after the Permian-Triassic event. Based on taxonomic, phylogenetic, and geochronologic data, the Buena Vista fauna allows us to quantify faunal turnover across the PTB and in the aftermath of the end Permian extinction event.

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Two New Triassic Temnospondyl Papers in the Journal Palaeontology

Witzmann, F., Schoch, R. R., Hilger, A., and N. Kardjilov. 2012. Braincase, palatoquadrate and ear region of the plagiosaurid Gerrothorax pulcherrimus from the Middle Triassic of Germany. Palaeontology 55:31-50. DOI: 10.1111/j.1475-4983.2011.01116.x

Abstract - The complete neurocranium plus palatoquadrate of the plagiosaurid temnospondyl Gerrothorax pulcherrimus from the Middle Triassic of Germany is described for the first time, based on outer morphological observations and micro-CT scanning. The exoccipitals are strong elements with paroccipital processes and well-separated occipital condyles. Anterolaterally, the exoccipitals contact the otics, which are mediolaterally elongated and have massive lateral walls. The otics contact the basisphenoid, which shows well-developed sellar processes. Anteriorly, the basisphenoid is continuous with the sphenethmoid region. In its posterior portion, the sphenethmoid gives rise to robust, laterally directed laterosphenoid walls, a unique morphology among basal tetrapods. The palatoquadrate is extensively ossified. The quadrate portion overlaps the descending lamina of squamosal and ascending lamina of pterygoid anteriorly, almost contacting the epipterygoid laterally. The epipterygoid is a complex element and may be co-ossified with otics and laterosphenoid walls. It has a broad, sheet-like footplate and a horizontally aligned ascending process that contacts the laterosphenoid walls. The degree of ossification of the epipterygoid, however, is subject to individual variation obviously independent from ontogenetic changes. The stapes of Gerrothorax is a large, blade-like element that differs conspicuously from the plesiomorphic temnospondyl condition. It has a prominent anterolateral projection which has not been observed in other basal tetrapods. Morphology of neurocranium and palatoquadratum of Gerrothorax most closely resembles that of the Russian plagiosaurid Plagiosternum danilovi, although the elements are less ossified in the latter. The extensive endocranial ossification of Gerrothorax is consistent with the general high degree of ossification in the exo- and endoskeleton of this temnospondyl and supports the view that a strong endocranial ossification cannot be evaluated as a plesiomorphic character in basal tetrapods.

Dias-da-Silva, S., Sengupta, D. P., Cabriera, S. F., and L. R. Da Silva. 2012. The presence of Compsocerops (Brachyopoidea: Chigutisauridae) (Late Triassic) in southern Brazil with comments on chigutisaurid palaeobiogeography. Palaeontology 55:163-172. DOI: 10.1111/j.1475-4983.2011.01120.x

Abstract - Chigutisauridae is the longest-lived trematosaurian clade (from early Triassic to early Cretaceous). They were reported in Argentina, Australia, India and South Africa. This contribution reports a putative chigutisaurid specimen in the Carnian of southern Brazil (Santa Maria Formation, Paraná Basin). The material comprises two skull fragments, a mandibular fragment, a clavicular blade and a humerus. Ontogenetic features point to an early development stage of the specimen. The presence of a long, straight and pointed tabular horn, which runs parallel to the skull midline towards its tip, and a distinctive projection in the posterior border of the postparietal indicates a close relationship of the Brazilian chigutisaurid with the Indian Compsocerops cosgriffi. Three distinctive and combined characters suggest that the Brazilian chigutisaurid is a distinctive specimen: the presence of an alar process of the jugal in the ventral margin of the orbit; jugal does not extend well beyond the anterior margin of the orbit; and tabular does not contact the parietal. These characters could justify the erection of a new taxon; however, they might reflect its immature ontogenetic stage as well. Accordingly, we attribute this new specimen to Compsocerops sp. Argentinean and Indian occurrences are dated as Norian, so the presence of a Carnian chigutisaurid in southern Brazil indicates that western Gondwana chigutisaurids have first occupied the Paraná Basin and later migrated towards west (to Argentina) and east (India). However, the presence of ghost chigutisaurid taxa cannot be dismissed, because their long temporal range contrasts with their still short (in comparison with other temnospondyl groups) geographic distribution. Hence, they might have been more geographically widespread than their fossil record suggests.

Cranial Morphology of the Plagiosaurid Gerrothorax pulcherrimus as an Extreme Example of Evolutionary Stasis

Schoch, R. R. and F. Witzmann. 2011. Cranial morphology of the plagiosaurid Gerrothorax pulcherrimus as an extreme example of evolutionary stasis. Lethaia, DOI: 10.1111/j.1502-3931.2011.00290.x

Abstract - The plagiosaurid Gerrothorax pulcherrimus from the Triassic of Greenland and Germany is represented by skulls ranging from 4 to 12 cm in length and sheds light on ontogeny, individual variation, and variation in time and space. Ontogeny was remarkably stable in G. pulcherrimus, with the smallest known specimens resembling the adults closely in most features. A true ontogenetic change is evident in the ornament of dermal bones, in that the smallest specimens have ridges whereas in the successively larger ones, pustules spread over increasingly larger areas. The skull becomes proportionally longer, and the adductor chambers relatively narrower. The positive allometry of both the orbits and the interpterygoid vacuities suggests that the eye supporting musculature – rather than the jaw adductors – increased proportionally during growth. Individual, not age-related variation in the dermal skull roof affects partial fusion of parietals, presence and extent of the interfrontoparietal, and the morphological pattern of the posterior skull table. The ventral surface of the basal plate of the parasphenoid ranges from smooth over poorly to heavily ornamented or dentigerous. Considering the impressive longevity of more than 35 Myr, the morphological changes of G. pulcherrimus are minor. Our ecological interpretation for G. pulcherrimus is that it relied on the permanent presence of water, but was flexible with respect to the size and nature of the water body as well as to changes in salinity. The unparalleled extent of evolutionary stasis may therefore be based on the ecological flexibility of this morphologically so tightly constrained temnospondyl.

New Capitosaur from the Early Triassic of Poland

Sulej, T., and G. Niedźwiedzki. in press. A new large capitosaur temnospondyl amphibian from the Early Triassic of Poland. Acta Palaeontologica Polonica available online 09 Sep 2011 doi:10.4202/app.2011.0025

 

Abstract - The Early Triassic record of the large capitosaur amphibian genus Parotosuchus is supplemented by new material from fluvial deposits of Wióry, southern Poland, corresponding in age to the Detfurth Formation (Spathian; late Olenekian) of the Germanic Basin. The skull of the new capitosaur shows an “intermediate” morphology between that of Parotosuchus helgolandicus from the Volpriehausen - Detfurth Formation (Smithian; early Olenekian) of Germany and the slightly younger P. orenburgensis from European Russia. These three species may represent an evolutionary lineage that underwent a progressive shifting of the jaw articulation anteriorly. The morphology of the Polish form is distinct enough from other species of Parotosuchus to warrant erection of a new species. The very large mandible of [new taxon name removed until formal publication] indicates that this was one of the largest tetrapods of the Early Triassic. Its prominent anatomical features include a triangular retroarticular process and an elongated base of the hamate process.

Middle Triassic Tetrapod from the Dead Sea Region of the Middle East

Schoch, R. R. 2011. A trematosauroid temnospondyl from the Middle Triassic of Jordan. Fossil Record 14:119–127 DOI: 10.1002/mmng.201100002

Abstract - A well-preserved mandible from the Lower Anisian Mukheiris Formation from near the Dead Sea (Jordan) proves the presence of tetrapods in the region. It is identified as a stereospondyl lower jaw sharing synapomorphies with the Trematosauroidea. It has the following combination of features: (1)Meckelian fenestra almost one-third the length of the ramus, (2) postglenoid area posterodorsally rising and robust, as long as glenoid facet, (3) preglenoid process substantially higher than medial margin of adductor chamber, (4) all teeth anteriorly and posteriorly carinate, and (5) symphysis without additional tooth rows, with a pair of unequal fangs as part of the dentary arcade, which contains unusually large teeth. The Jordan specimen shares most character-states with South African Microposaurus (size of teeth, bicarinate structure) and the Russian Inflectosaurus (preglenoid process, PGA). Phylogenetic analysis finds it to nest with Microposaurus, whereas Inflectosaurus forms an unresolved polytomy with other trematosauroids.

Review of the Lower Triassic Temnospondyl Fauna of Germany

Schoch, R. R. 2011. How diverse is the temnospondyl fauna in the Lower Triassic of southern Germany? Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 261:49-60. DOI: 10.1127/0077-7749/2011/0147

Abstract - Among the few fossiliferous Lower Triassic deposits in Europe, the Lower to Middle Buntsandstein of the German southwest has yielded a range of interesting finds. A review of the published and new material gives the following results: (1) The oldest identified remain is a mandible of a small stereospondyl from the Bernburg Formation (Induan); (2) A new palate from the early Olenekian (Badischer Bausandstein) stems from a basal capitosaur similar to Wetlugasaurus; (3) In the late Olenekian (Hardegsen Formation), two well-defined temnospondyl genera are present: the basal capitosauroids Meyerosuchus fuerstenbergianus and Odenwaldia heidelbergensis. Large remains formerly referred to Mastodonsaurus either pertain to a different family or are undiagnostic, pushing the first occurrence of mastodonsaurids into the Anisian. These finds highlight the presence of large aquatic predators by early Triassic time, revealing an increasing diversity of aquatic predators from the Induan to the Anisian. The documented faunal changes involved patterns of immigration and extinction/emigration rather than endemic evolution within the basin. In contrast to the northern parts of the basin, the genera Trematosaurus, Parotosuchus, and Sclerothorax are absent in the southern part, where Meyerosuchus and Odenwaldia existed.

Calmasuchus acri, a new Capitosaur from the Middle Triassic of Spain

Just when I had been thinking that things had been rather slow this year regarding Triassic temnospondyl studies:

Fortuny, J., Galobart, À, and C. De Santisteban. In  press. A new capitosaur from the Middle Triassic of Spain and the relationships within the Capitosauria. Acta Palaeontologica Polonica, available online 29 Dec 2010 doi:10.4202/app.2010.0025
Abstract - 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 recovered 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.

Temnospondyl Paleoenvironmental Adaptations: Evidence from Bone Histology

Sanchez, S., Germain, D., De Ricqles, A., Abourachid, A., Goussard, F. and Tafforeau, P. 2010. Limb-bone histology of temnospondyls: implications for understanding the diversification of palaeoecologies and patterns of locomotion of Permo-Triassic tetrapods. Journal of Evolutionary Biology, early online. doi:10.1111/j.1420-9101.2010.02081.x

Abstract - The locomotion of early tetrapods has long been a subject of great interest in the evolutionary history of vertebrates. However, we still do not have a precise understanding of the evolutionary radiation of their locomotory strategies. We present here the first palaeohistological study based on theoretical biomechanical considerations among a highly diversified group of early tetrapods, the temnospondyls. Based on the quantification of microanatomical and histological parameters in the humerus and femur of nine genera, this multivariate analysis provides new insights concerning the adaptations of temnospondyls to their palaeoenvironments during the Early Permian, and clearly after the Permo-Triassic crisis. This study therefore presents a methodology that, if based on a bigger sample, could contribute towards a characterization of the behaviour of species during great evolutionary events.

Functional Implications of Dermal Bone Ornamentation in Basal Tetrapods

Metoposaurs are a very common component of the Chinle Formation fauna, especially the lower portions.  I often get questions on the function of the ornament of metoposaur dermal bones (skull, clavicles, interclavicle) and finally some of those questions can be answered. 

Witzmann, F., Scholz, H., Mueller, J., and N. Kardjilov. 2010. Sculpture and vascularization of dermal bones, and the implications for the physiology of basal tetrapods. Zoological Journal of the Linnean Society, early online. doi: 10.1111/j.1096-3642.2009.00599.x

Abstract - Sculpture of dermal bones and their vascularization in basal tetrapods are closely connected. Ontogenetic data suggest that the large vessels that coursed to the superficial bone surface induced the formation of sculptural ridges and tubercles around their openings. Imprints show that the vessels continued on the bone surface and coursed within furrows or pits, where they were protected by the sculpture from mechanical damage. Dermal bone histology indicates a consolidation of the integument in basal tetrapods by strong, mineralized Sharpey’s fibres in the sculptural ridges and tubercles, and by the presence of metaplastic tissue in several taxa. Because of the tight integration of bone and dermis, the large vessels were not able to spread over the sculptural elements, but instead had to pass interosseously. The diverse sculptural morphologies depend on the variation in height and width of the ‘nodal points’ and their connecting ridges, and in the size and shape of the enclosed cells and furrows. A principal component analysis (PCA) and discriminant function analysis (DFA) of 47 basal tetrapod taxa with 12 discrete characters shows that dermal sculpture is suited for distinguishing some main basal tetrapod lineages. Taxa that are interpreted as being largely aquatic have generally a more regular sculpture than presumably terrestrial ones.

Investigating the Non-Marine TR/J Boundary in Portugal

Dr. Richard Butler (Bayerische Staatssammlung für Paläontologie und Geologie, Munich), Dr. Octavio Mateus (University of Lisbon) and Steven Brusatte (American Museum of Natural History) have initiated a new field project to study terrestrial strata (Grès de Silves Formation) spanning the Triassic-Jurassic boundary in Portugal in hopes of recovering late surviving temnospondyls and possibly other Late Triassic vertebrates. Preliminary results are encouraging and you can read about them here.


Given that many Late Triassic Laurasian faunal assemblages appear very similar in content despite their stratigraphic position (e.g., Placerias Quarry vs. Coelophysis Quarry in the Chinle Formation), these types of studies are crucial to our understanding of exactly what is happening with the Triassic-Jurassic non-marine extinctions. Unfortunately many places that preserve this boundary and are accessible are non-fossiliferous (e.g., Newark Supergroup); whereas other places that may be very fossiliferous (e.g., Moenave and Kayenta Formations of Arizona) are not easily accessible.

Latest Literature

Some new papers, one on the phylogeny of the Parareptilia and two on the Permian branchisaurid Apateon. I know that the last two are not Triassic but they are close enough! Plus, more papers on temnospondyls.

Tsuji L. A. and J. Muller. 2009. Assembling the history of the Parareptilia: phylogeny, diversification, and a new definition of the clade. Fossil Record 12:71-81. DOI 10.1002/mmng.200800011

ABSTRACT - In the present study, the historical development of Parareptilia as a phylogenetically valid clade is summarized, and for the first time a modern phylogenetic definition of both Parareptilia as well as Eureptilia is presented, which will facilitate the study of problems of early amniote classification. Furthermore, a preliminary study of the rates of diversification in parareptiles is performed on the basis of topological information on species diversity. While acknowledging that the bias of the fossil record also needs to be considered for a more definitive statement on parareptile diversification, our results show that a significant increase in diversification rate could be recorded only among Triassic procolophonoids, making it difficult to interpret evolutionary novelties such as herbivory or impedance-matching hearing as being key innovations that might have driven diversification.

Witzmann, F. 2009. Cannibalism in a small growth stage of the Early Permian branchiosaurid Apateon gracilis (Credner, 1881) from Saxony. Fossil Record 12:7-11. DOI 10.1002/mmng.200800006

ABSTRACT - An almost complete specimen of the branchiosaurid temnospondyl Apateon gracilis (Credner, 1881) with a skull length of approximately 7 mm from the Early Permian Dohlen Basin in Saxony is described that possesses a nearly complete conspecific specimen of approximately 4 mm skull length in its digestive tract. This is the first evidence of cannibalistic behaviour in small growth stages of branchiosaurids, whose dentition and hyobranchial morphology suggest adaptations to the capture of small invertebrates and feeding on small phyto- and zooplankton by filtering from the water. Therefore, cannibalism in small branchiosaurids certainly represents an exceptional case, possibly triggered by unfavourable environmental conditions.

Frobisch, N.B., and R.R. Schoch. 2009. The largest specimen of Apateon and the life history pathway of neoteny in the Paleozoic temnospondyl family Branchiosauridae. Fossil Record 12:83-90. DOI 10.1002/mmng.200800012

ABSTRACT - Two distinct developmental trajectories, metamorphosis and neoteny (the retention of larval somatic features in adult animals), have been reported for the small gill-bearing branchiosaurids of the Late Carboniferous and Early Permian of central Europe. Based on a very large specimen of the species Apateon caducus (Ammon, 1889), anatomical features characteristic for the neotenic phenotype of branchiosaurids are described. Large neotenes lack changes that occur during a short phase of transformation into terrestrial adults (metamorphosis), such as ossification of the braincase and palatoquadrate and intercentra, further ossification of the girdles and formation of muscle attachment scars and processes on the limb bones. They also lack a distinct sculpturing of the dermal skull roofing elements with deep polygonal ridges and grooves. Instead, larval somatic features are retained including ossified branchial denticles indicative of open gill slits and accentuated larval-type sculpturing of the dermal skull roof. Large size, high degree of ossification as compared to the larvae, and the presence of uncinate processes on the ribs clearly demonstrate an adult ontogenetic stage. Neotenes remained in the aquatic environment throughout their life and were most likely not capable of effective terrestrial locomotion. The frequency distribution of the two phenotypes in modern salamander populations and the environmental cues that influence the development of them provide a comparative framework for the discussion of the evolution of the two life history pathways in branchiosaurids.

Another One!

I promise that I will write a real post soon, but here is another new Triassic temnospondyl paper! We just cannot seem to get enough temnospondyl papers these days...

Maganuco, S., and G. Pasini. 2009. A new specimen of trematosaurian temnospondyl from the Lower Triassic of NW Madagascar, with remarks on palatal anatomy and taxonomic affinities. Atti della Societtaliana di scienze naturali e del Museo civico di storia naturale di Milano 150:91-112.

Abstract - A new partial skull (preserved as a natural mould) of a trematosaurid temnospondyl from the Lower Triassic of the Ankitokazo Basin, Diégo Suarez Province, NW Madagascar, is described. It provides new information on the palatal anatomy, poorly known in the Malagasy trematosaurids, the more important concerning the morphology of the cultriform process, which is squared in cross section and comparatively wide. The new specimen represents a taxon well distinct from both Malagasy lonchorhynchine trematosaurid Wantzosaurus elongatus and other trematosaurid genera known out of Madagascar. The taxonomic and phylogenetic affi nities found between the new skull and all the Malagasy non-lonchorhynchine specimens so far described suggest that the material may belong to a single species, closely related to the German species Trematolestes hagdorni, and more similar to Tertrema acuta than to Trematosaurus brauni. The new skull is therefore tentatively referred to cf. Tertremoides madagascariensis, the only non-lonchorhynchine trematosaurid species from Madagascar that we regard as valid, following the systematic review by Schoch & Milner (2000).

This paper also cites an in press publication....

Maganuco S., Steyer J. S., Pasini G., Boulay M., Lorrain S., Bénéteau A. & Auditore M., in press – An exquisite specimen of Edingerella madagascariensis (Temnospondyli) from the Lower Triassic of NW Madagascar; cranial anatomy, phylogeny and restorations. Memorie della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano.

Both of these papers are from Simone Maganuco's PhD dissertation.

Reconstruction is Trematosaurus from Wikipedia commons.

Another New Reference and Amazingly Productive Publishing Paleontologists

This one just missed my "Latest Literature" post a few days back. I had commented earlier how 2008 was an amazing year for new temnospondyl papers (and basal turtles) and here is another in early 2009 (although it had been in press since 2007!).

By the way...I am often just blown away by the productivity of some vertebrate paleontologists. I recently linked to Richard Butler's webpage and here now is Rainer Schoch's. Just look at his upcoming output which includes the new paper featured here. Not only do these individuals produce so many papers, but they are all consistantly excellent. Hat's off to Drs. Schoch and Butler!

Damiani, R., Schoch, R.R., Hellrung, H., Werneburg, R., and S. Gastou. 2009. The plagiosaurid temnospondyl Plagiosuchus pustuliferus (Amphibia: Temnospondyli) from the Middle Triassic of Germany: anatomy and functional morphology of the skull. Zoological Journal of the Linnaean Society 155:348-373. doi:10.1111/j.1096-3642.2008.00444.x

Abstract: The cranial anatomy of the plagiosaurid temnospondyl Plagiosuchus pustuliferus, from the Middle Triassic of Germany, is described in detail on the basis of a newly discovered skull and mandibular material. The highly derived skull is characterized by huge orbitotemporal fenestrae, a reduction of the circumorbital bones – the prefrontal, postfrontal and (probably) postorbital are lost – and the expansion of the jugal to occupy most of the lateral skull margin. Ventrally the extremely long subtemporal vacuities correlate with the elongate adductor fossa of the mandible. The dentition is feebly developed on both skull and mandible. Ossified
?ceratobranchials and 'branchial denticles' indicate the presence of open gills clefts in life. The remarkably divergent cranial morphology of P. pustuliferus highlights the extraordinary cranial diversity within the Plagiosauridae, probably unsurpassed within the Temnospondyli. Specific structural aspects of the skull – including an extremely short marginal tooth row, feeble dentition and an elongated chamber for adductor musculature – together with evidence for a hyobranchial skeleton, suggests that P. pustuliferus utilized directed suction feeding for prey capture.

I have always wondered why temnospondyls are often given names that end with -saurus and suchus?

First record of stereospondyls from the Upper Triassic of Brazil

Dias-da-Silva, S., Dias, E.V., and C.L. Schultz. 2009. First record of stereospondyls (Tetrapoda, Temnospondyli) in the Upper Triassic of Southern Brazil. Gondwana Research 15:131-136. doi:10.1016/j.gr.2008.07.002

Abstract - Stereospondyls survived the Permo-Triassic extinctions in a refuge probably located in the landmass that nowadays comprises Australia. Subsequently, they radiated to other parts of Pangaea, reaching their highest distribution and diversification during the Early Triassic. An incomplete interclavicle from the Caturrita Formation represents their first record in the Upper Triassic of Brazil. Previously, Upper Triassic South American stereospondyls were restricted to Argentina. This new record reinforces a former hypothesis that suggests the presence of a more diverse stereospondyl fauna in South America during the Late Triassic than previously assumed. Additionally, the presence of a stereospondyl and a phytosaur in the Caturrita Formation reinforces the hypothesis of a change to more humid climatic conditions in the Paraná Basin during the Upper Triassic. The record of Early Triassic stereospondyls in South America suggests that they first colonized Brazil and/or Uruguay, spreading from South Africa during the Early Triassic, subsequently reaching Argentina. Up till now, there is no record of Middle Triassic stereospondyls in either Argentina and Brazil, probably due to either taphonomic bias or insufficient prospecting. Despite the lack of direct evidence, one should not dismiss an earlier stereospondyl colonization of Argentina still during the Early or Middle Triassic.