Taxonomy, morphometry and morphospace of cranial bones of Panthasaurus gen. nov. maleriensis from the Late Triassic of India

Abstract

Metoposaurids are an important Late Triassic temnospondyl family known from nonmarine sediments of Europe, North-America, North Africa and India. Indian taxon Metoposaurus maleriensis became Buettneria maleriensis. “Metoposaurus” was thereafter restricted to encompass only M. diagnosticus from Germany and M. bakeri from North America, whose lacrimals are excluded from the orbital margin. However, some specimens of M. diagnosticus also exhibit lacrimals contributing to the orbital margins, as in Buettneria. Also, the generic name Buettneria was preoccupied, and Koskinonodon represents the senior synonym. Hence, the taxonomic status of the Indian metoposaurids became questionable. Metoposaurids being extremely conservative in nature, no single character could be assigned to distinguish them at the species level and there is no alpha level taxonomy available. Assigning a taxonomic status of the Indian taxon along with alpha taxonomy of all the other metoposaurids viewed through the lights of morphometry and morphospace is the main purpose of this paper. All genera were studied first hand from different museums of the world. Detailed measurements of skull bones and morphological properties are critically appraised. Biometric studies were done to analyse the variation between different taxa. Morphospace of different bones are constructed after conducting elliptical Fourier analysis and PCA using R. Cladogram using TNT and comparison of the cranial morphology is provided. Fourteen parsimonious trees, 50% majority rule consensus, Bremer support value and bootstrap resampling all reveals that Indian taxon occupies a distinct position somewhere between the European Metoposaurus and North American Koskinonodon. This fact corroborates with the morphospace analysis. There is also a strong bio geographic correlation in the fact that the Indian taxon was widely separated from the main cluster of the European and the North American taxa. Panthasaurus gen. nov. maleriensis is erected for the Indian taxon of metoposaurids. Biometry and morphospace studies supports Indian Metoposaurus to be a separate taxon.