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1 December 2006 CRANIAL ANATOMY OF THE EARLY TRIASSIC STEREOSPONDYL LYDEKKERINA HUXLEYI (TETRAPODA: TEMNOSPONDYLI) AND THE TAXONOMY OF SOUTH AFRICAN LYDEKKERINIDS
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Abstract

The cranial anatomy of Lydekkerina huxleyi, a lydekkerinid stereospondyl from the Lower Triassic Lystrosaurus Assemblage Zone (Beaufort Group; Karoo Basin) of South Africa, is redescribed in detail following additional preparation of the poorly known holotype specimen. Whereas previous studies failed to identify any uniquely derived characteristics of L. huxleyi, three autapomorphies are identified herein: the presence of paired, anterodorsal projections within the anterior palatal vacuity, vomerine shagreen, and a series of thickened ridges on the ventral surface of the skull roof. The low ridge on the quadrate ramus of the pterygoid in L. huxleyi, previously identified as the crista obliqua homologous to that of mastodonsauroids, is reinterpreted in light of new observations on rhinesuchids. The mandible is described in detail for the first time and is shown to possess an extensive denticle shagreen on all three coronoid elements (as in primitive stereospondyls), and a distinctly elongated, prong-like arcadian process of the postglenoid area. Characters that show intraspecific variation in L. huxleyi include the contribution of the lacrimal to the narial margin, the presence of an ectopterygoid tusk, the degree of development of the transverse flange of the pterygoid, and the number of anterior meckelian foramina on the mandible. Redescription of L. huxleyi permits a reassessment of lydekkerinid species diversity in the Karoo Basin: ‘Broomulus dutoiti’ and ‘Limnoiketes paludinatans’ are regarded as subjective junior synonyms of L. huxleyi. Morphologically, Eolydekkerina magna resembles L. huxleyi more closely than had been initially suggested, and is cautiously regarded as a distinct taxon.

ASHLEIGH M. JEANNOT, ROSS DAMIANI, and BRUCE S. RUBIDGE "CRANIAL ANATOMY OF THE EARLY TRIASSIC STEREOSPONDYL LYDEKKERINA HUXLEYI (TETRAPODA: TEMNOSPONDYLI) AND THE TAXONOMY OF SOUTH AFRICAN LYDEKKERINIDS," Journal of Vertebrate Paleontology 26(4), 822-838, (1 December 2006). https://doi.org/10.1671/0272-4634(2006)26[822:CAOTET]2.0.CO;2
Accepted: 24 June 2006; Published: 1 December 2006
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