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.
Showing posts with label capitosauria. Show all posts
Showing posts with label capitosauria. Show all posts
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
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.
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.
Relaunch of Stuttgarter Beiträge zur Naturkunde Serie B as the open access journal Palaeodiversity
Thanks to Randy Irmis for bringing this to my attention. The journal Stuttgarter Beiträge zur Naturkunde Serie B has been relaunched as a new open access journal Palaeodiversity. The first issue was released in late 2008 and contains a new paper by Rainer Schoch on the phylogeny of the Capitosauria (the amount of temnospondyl work pubished in 2008 is just amazing!).
Also of great interest is that the journal site is offering free downloads of articles (including some Triassic articles) from back issues of Stuttgarter Beiträge zur Naturkunde Serie from 1999 with a promise that more will follow (www.palaeodiversity.org/backissues.htm).
Schoch, R. R. 2008. The Capitosauria (Amphibia): characters, phylogeny, and stratigraphy. Palaeodiversity 1:189-226.
Abstract - The phylogeny of the largest amphibians, the Triassic capitosaurs, is still much debated. One key taxon for the understanding of their relationships, Odenwaldia heidelbergensis from the Buntsandstein of Waldkatzenbach, is restudied here. A phylogenetic analysis performed on the basis of 66 characters and 25 taxa gives a new hypothesis of relationships. It rests to a large degree on previous data matrices, but many character codings have been changed with respect to new observations as well as the discovery of new taxa. The present data indicate that all classic capitosaur taxa do form a clade. The Capitosauria (all taxa more closely related to Parotosuchus than to Trematosaurus) excludes Benthosuchus and Edingerella but includes Wetlugasaurus, Sclerothorax, Watsonisuchus, Parotosuchus, and all other capitosaurs. All capitosaurs above Watsonisuchus are referred to as the Capitosauroidea, which includes Parotosuchus, Cherninia + Odenwaldia, Eryosuchus, Xenotosuchus, and a vast capitosaur crown clade. The crown includes two main branches: (1) the “Eucyclotosauria” (Cyclotosaurus, Kupferzellia, Procyclotosaurus, Stanocephalosaurus pronus) and (2) the “Paracyclotosauria” (Stanocephalosaurus birdi, Paracyclotosaurus, Mastodonsaurus, and the heylerosaurids Eocyclotosaurus and Quasicyclotosaurus). Stratigraphically, capitosaur phylogeny still reveals a rather poor match. However, the present phylogenetic hypothesis matches the stratigraphic ranges more precisely than the previous ones. The early branching between the “Eucyclotosauria” and “Paracyclotosauria” is more consistent with the fossil record than an alternative concept, in which Cyclotosaurus and the heylerosaurids form sister taxa (“Pancyclotosauria”). In any case, the otic fenestra and several other probably correlated features in the palate must have evolved two times independently within the crown capitosauroids.
Also of great interest is that the journal site is offering free downloads of articles (including some Triassic articles) from back issues of Stuttgarter Beiträge zur Naturkunde Serie from 1999 with a promise that more will follow (www.palaeodiversity.org/backissues.htm).
Schoch, R. R. 2008. The Capitosauria (Amphibia): characters, phylogeny, and stratigraphy. Palaeodiversity 1:189-226.
Abstract - The phylogeny of the largest amphibians, the Triassic capitosaurs, is still much debated. One key taxon for the understanding of their relationships, Odenwaldia heidelbergensis from the Buntsandstein of Waldkatzenbach, is restudied here. A phylogenetic analysis performed on the basis of 66 characters and 25 taxa gives a new hypothesis of relationships. It rests to a large degree on previous data matrices, but many character codings have been changed with respect to new observations as well as the discovery of new taxa. The present data indicate that all classic capitosaur taxa do form a clade. The Capitosauria (all taxa more closely related to Parotosuchus than to Trematosaurus) excludes Benthosuchus and Edingerella but includes Wetlugasaurus, Sclerothorax, Watsonisuchus, Parotosuchus, and all other capitosaurs. All capitosaurs above Watsonisuchus are referred to as the Capitosauroidea, which includes Parotosuchus, Cherninia + Odenwaldia, Eryosuchus, Xenotosuchus, and a vast capitosaur crown clade. The crown includes two main branches: (1) the “Eucyclotosauria” (Cyclotosaurus, Kupferzellia, Procyclotosaurus, Stanocephalosaurus pronus) and (2) the “Paracyclotosauria” (Stanocephalosaurus birdi, Paracyclotosaurus, Mastodonsaurus, and the heylerosaurids Eocyclotosaurus and Quasicyclotosaurus). Stratigraphically, capitosaur phylogeny still reveals a rather poor match. However, the present phylogenetic hypothesis matches the stratigraphic ranges more precisely than the previous ones. The early branching between the “Eucyclotosauria” and “Paracyclotosauria” is more consistent with the fossil record than an alternative concept, in which Cyclotosaurus and the heylerosaurids form sister taxa (“Pancyclotosauria”). In any case, the otic fenestra and several other probably correlated features in the palate must have evolved two times independently within the crown capitosauroids.
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