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Book Chapter

Phytosauria

By
Michelle R. Stocker
Michelle R. Stocker
Department of Geological Sciences, Jackson School of Geosciences, 1 University Station, C1100, The University of Texas at Austin, Austin, Texas 78712, USA
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Richard J. Butler
Richard J. Butler
GeoBio-Center, Ludwig-Maximilians-Universität München, Richard-Wagner-Straße 10, D-80333 Munich, Germany
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Published:
January 01, 2013

Abstract

Phytosauria is a nearly cosmopolitan clade of large, quadrupedal, carnivorous archosauriforms. They are known unambiguously from Late Triassic deposits, although the clade’s ghost lineage extends at least to the late Early Triassic. Their nares are uniquely located close to the orbits rather than anteriorly in the rostrum as in modern crocodylians, and the rostrum is formed by elongated premaxillae bearing many teeth. Phytosaurs have roughly triangular, ornamented paramedian osteoderms, rounder appendicular osteoderms, and a unique ‘gular shield’ assembled from multiple, irregular osteoderms under the throat. Phytosaurs are reconstructed as semi-aquatic because of their general similarity to modern crocodylians and common preservation in fluvial and shallow-marine deposits. Currently, over thirty species are recognized. New specimens continue to be collected, some representing new taxa. The taxonomic status of other named taxa is uncertain and requires re-investigation. Since their discovery, phytosaurs have been used as biostratigraphic and biochronological index taxa for correlating Late Triassic sediments worldwide. Recent systematic and taxonomic revisions cast doubt on some of those correlations. Our understanding of the evolution of Phytosauria is far from complete. With reevaluation of well-known specimens, rigorous and comparative morphological descriptions, and robust phylogenetic hypotheses of ingroup relationships, studies of phytosaurs can address larger palaeobiological questions.

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Contents

Geological Society, London, Special Publications

Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and their Kin

S. J. Nesbitt
S. J. Nesbitt
University of Washington, USA
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J. B. Desojo
J. B. Desojo
Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’, Argentina
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R. B. Irmis
R. B. Irmis
Natural History Museum of Utah, USA
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Geological Society of London
Volume
379
ISBN electronic:
9781862396395
Publication date:
January 01, 2013

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