The brachyopoid Hadrokkosaurus bradyi from the early Middle Triassic of Arizona, and a phylogenetic analysis of lower jaw characters in temnospondyl amphibians

Ruta, Marcello and Bolt, John R. (2008) The brachyopoid Hadrokkosaurus bradyi from the early Middle Triassic of Arizona, and a phylogenetic analysis of lower jaw characters in temnospondyl amphibians. Acta Palaeontologica Polonica, 53 (4). pp. 579-592. ISSN 0567-7920

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Abstract

The holotype of the brachyopoid temnospondyl Hadrokkosaurus bradyi, represented by a right lower jaw ramus, is re−ex−
amined based upon new data and revision of various morphological features. Additional fragmentary jaw material re−
ferred to this species is briefly described. Prominent features are a large postsymphyseal foramen that is anteriorly open,
and prearticular and surangular buttresses for support of the articular. Brachyopoid characters include a long and robust
postglenoid area formed by surangular and prearticular, anterior and posterior keels on at least some marginal dentary
teeth, and subtriangular outline of the adductor fossa in dorsal view. Five features of the holotype ramus, long thought to
be at odds with its brachyopoid or temnospondyl nature, are critically re−evaluated. A phylogenetic analysis of lower jaw
characters in temnospondyls retrieves most of the clades found in more comprehensive data sets, but the statistical node
support is low. Brachyopoids are monophyletic, with Hadrokkosaurus emerging as their most basal taxon.

Item Type:Article
Additional Information:The holotype of the brachyopoid temnospondyl Hadrokkosaurus bradyi, represented by a right lower jaw ramus, is re−ex− amined based upon new data and revision of various morphological features. Additional fragmentary jaw material re− ferred to this species is briefly described. Prominent features are a large postsymphyseal foramen that is anteriorly open, and prearticular and surangular buttresses for support of the articular. Brachyopoid characters include a long and robust postglenoid area formed by surangular and prearticular, anterior and posterior keels on at least some marginal dentary teeth, and subtriangular outline of the adductor fossa in dorsal view. Five features of the holotype ramus, long thought to be at odds with its brachyopoid or temnospondyl nature, are critically re−evaluated. A phylogenetic analysis of lower jaw characters in temnospondyls retrieves most of the clades found in more comprehensive data sets, but the statistical node support is low. Brachyopoids are monophyletic, with Hadrokkosaurus emerging as their most basal taxon.
Keywords:Temnospondyli, Brachyopidae, Chigutisauridae, lowe jaw, phylogeny, characters, evolution
Subjects:C Biological Sciences > C300 Zoology
C Biological Sciences > C182 Evolution
F Physical Sciences > F641 Palaeontology
C Biological Sciences > C181 Biodiversity
Divisions:College of Science > School of Life Sciences
ID Code:6400
Deposited By: Marcello Ruta
Deposited On:02 Oct 2012 12:05
Last Modified:21 Jul 2014 08:20

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