A taxonomic revision of the genus Procolophon and the phylogenetic relationships of Procolophonoid reptiles
Date
2008-03-18T08:54:02Z
Authors
Martinez, Juan Carlos Cisneros
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Abstract
ABSTRACT
This study presents a taxonomic revision of some procolophonoid parareptiles and
a detailed, global analysis of procolophonid intrarelationships. The poorly known
genus Candelaria, from the Middle Triassic of Brazil, is identified on the basis of
new material as an owenettid, rather than a procolophonid as previously thought.
Thus, Candelaria represents the youngest owenettid and the first member of this
group from South America. The cranium of Candelaria is also remarkable for
having temporal fenestrae, and the significance of this character within the
Parareptilia is discussed. Based on a comprehensive review of specimens referred
to different Procolophon species, it is proposed that only the type species,
Procolophon trigoniceps, is valid. Thus, Procolophon specimens from Brazil,
South Africa, and Antarctica are all referable to P. trigoniceps. Consequently, P.
trigoniceps has one of the broadest known geographic ranges among Triassic
tetrapod species.
A comprehensive cladistic analysis of procolophonids more firmly resolves the
relationships within that group. The analysis reveals that Procolophoninae and
Leptopleuroninae are valid monophyletic groups, whereas Spondylolestinae is
paraphyletic. The species formerly assigned to the genus ‘Thelegnathus’ from the
Middle Triassic of South Africa, and those assigned to ‘Eumetabolodon’ from the
Lower-Middle Triassic of China, are paraphyletic.
The poorly known Spondylolestes from the Dicynodon Assemblage Zone of South
Africa is considered valid and possibly represents the only Permian procolophonid
in Gondwana. A new species, Kitchingnathus untabeni, is identified in the
Lystrosaurus Assemblage Zone of South Africa. It is a basal member of the
Procolophonidae and co-occurs with Procolophon in the Upper Katberg
Formation. The new taxon is characterized by the presence of a large number of
thin, bicuspid teeth. Character optimisation indicates that bicuspid teeth were
acquired independently in K. untabeni, and hence originated twice during
procolophonid evolution. A review of procolophonid records worldwide reveals a
fossil hiatus for members of this group in the Ladinian and most of the Carnian.
Description
Keywords
Procolophon, parareptiles, phylogeny, Gondwana, Triassic