Witzmann, Florian and Scholz, Henning and Ruta, Marcello (2009) Morphospace occupation of temnospondyl growth series: a geometric morphometric approach. Alcheringa: An Australasian Journal of Palaeontology, 33 (3). pp. 237-255. ISSN 0311-5518

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Abstract

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 (Fric, 1876) 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.

Item Type:	Article
Additional Information:	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 (Fric, 1876) 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.
Keywords:	geometric morphometrics, heterochrony, Temnospondyli, ontogeny, skull shaoe, landmarks
Subjects:	C Biological Sciences > C182 Evolution C Biological Sciences > C300 Zoology C Biological Sciences > C191 Biometry F Physical Sciences > F641 Palaeontology
Divisions:	College of Sciences > Faculty of Science > School of Life Sciences
Depositing User:	Marcello Ruta
Date Deposited:	07 Oct 2012 09:40
Last Modified:	13 Mar 2013 09:16
URI:	http://eprints.lincoln.ac.uk/id/eprint/6450

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