A new temnospondyl amphibian from the Lower Triassic of South America

A new temnospondyl from the Early Triassic Buena Vista Formation (Paraná Basin) in Uruguay is described. The specimen is represented by a skull table fragment which includes the left orbit, and, although fairly incomplete, shows close affinities with the basal temnospondyl clade (Dvinosaurus + Tupilakosauridae). Previously, members of this clade were only known from Upper Permian and Lower Triassic deposits from the Northern Hemisphere. The new specimen described herein together with a recent record from the Lower Triassic of South Africa (Karoo Basin), support the hypothesis of an invasion of members of the basal (Dvinosaurus + Tupilakosauridae) clade into Gondwana as early as the Late Permian.     

A short-snouted trematosauroid (Tetrapoda,Temnospondyli) from the Early Triassic of Australia: the oldest known trematosaurine

The trematosauroid temnospondyl Tirraturhinus smisseni gen. et sp. nov. from the Arcadia Formation of central Queensland, Australia, is described on the basis of its rostrum. This is the first trematosaurine (short-snouted) trematosauroid from Australia, and is considered to be most closely related to Tertrema acuta from Spitzbergen. Tirraturhinus smisseni occurs alongside lonchorhynchine (long-snouted) trematosauroids in the Arcadia Formation; the co-occurrence of both trematosauroid morphotypes in that fauna is repeated in a number of non-marine Early Triassic faunas elsewhere in Pangaea. The Arcadia Formation is probably Griesbachian (earliest Triassic), so that T. smisseni is the oldest known trematosaurine.     

Morphospace occupation of temnospondyl growth series: a geometric morphometric approach

A morphometric analysis based on 16 landmarks (specific geometric points) identified on the skull roof of different growth stages of various temnospondyls revealed patterns of shape change during ontogeny. Data from 50 individuals from 12 taxa, encompassing euskelians (dissorophoids, eryopids and zatracheids) and stereospondylomorphs were plotted in a morphospace diagram defined by two principal-component axes (PC 1 and PC 2) of a principal-component analysis of the shape variables. The morphospace occupation reflects phylogenetic relationships of the main clades of temnospondyls. All stereospondylomorphs investigated here have similar ontogenetic trajectories with long intervals on PC 1. Eryopids and zatracheids have shortened their trajectories on PC 1 and are separated in morphospace relative to the stereospondylomorphs and dissorophoids. Outgroup comparison with Cochleosaurus bohemicus (Fri?, 1876 Fri?, A. 1876. Über die Fauna der Gaskohle des Pilsner und Rakonitzer Beckens. Sitzungsberichte der Königlichen Böhmischen Gesellschaft der Wissenschaften, 1875: 70–79.  [Google Scholar]) suggests that a long ontogenetic trajectory with gradual development represents the plesiomorphic condition for temnospondyls. More derived stereospondylomorphs (among the taxa considered here, but excluding groups such as derived rhytidosteids and brachyopoids) increased the length of their trajectories on PC 1 and show a peramorphic pattern, resulting in the long and slender skull of piscivorous predators. Dissorophoids exhibit truncated ontogenetic trajectories and occupy the morphospace region of larval stereospondylomorphs, thus attaining a paedomorphic appearance probably by hypomorphosis. Amphibamid and branchiosaurid dissorophoids have clearly distinguishable larval and postlarval developments, indicating that these forms had evolved a lissamphibian-like type of metamorphosis.