The interrelationships of Placodontia
1997; Taylor & Francis; Volume: 12; Issue: 3-4 Linguagem: Inglês
10.1080/08912969709386564
ISSN1029-2381
AutoresOlivier Rieppel, Robert T. Zanon,
Tópico(s)Genomics and Phylogenetic Studies
ResumoFive terminal taxa (at the generic level) of Placodontia are recognized; the status of Psephosaurus remains problematical. A cladistic analysis of the interrelationships of Placodontia, based on 30 characters, results in two equally parsimonious trees. The Placodontia comprise two major subclades, the Placodontoidea and the Cyamodontoidea. Within the Placodontoidea, Paraplacodus is the sister‐taxon of Placodus. Within the Cyamodontoidea, Henodus is the most basal clade in one tree, a crown‐group cyamodontoid (the sister‐taxon of Placochelys) in the second tree. Cyamodus is the sister‐taxon of a clade comprising Placochelys and Psephoderma in the first tree, and is the most basal cyamodontoid clade in the second tree. The second tree is provisionally accepted because of the late appearance of Henodus in the fossil record of placodonts. The significance of these findings for the reconstruction of the paleobiogeographical history of the group is discussed. Key words: PlacodontiaTriassicPhylogenetic analysisPaleobiogeography
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