Morphometrical distinction between sheep ( Ovis aries ) and goat ( Capra hircus ) using the petrosal bone: Application on French Protohistoric sites
Résumé
Often present in the archaeological record but rarely studied in archaeozoology, the petrosal part of the temporal bone provides important distinctive features allowing specific determination, despite a confusing morphological variability. Here, we propose to use this bone to untangle the question of the distinction between sheep and goat-two close taxa that are usually difficult to distinguish in the fossil record. We evaluated our method on Neolithic and Protohistoric specimens found in sites from Southwestern France in addition to a modern reference sample. Anatomical description and diameter measurements defined on the medial side proved to be relevant to discriminate those caprines, even on the fossil record, characterised by a high frequency of breakage. Our results highlighted the importance of reducing the size effect by transforming the data because of the great variability of the petrosal. The use of log-shape ratios transformation allowed us to visualise the shape variation of this bone for both modern and ancient specimens. The k-nearest neighbours method proved the efficiency of our measurements to classify these species. This study interrogates the origin of intraspecific morphological variation, probably due to ontogenetic development and breeds. It also raises questions on the identification of the domestication processes through the use of the petrosal bone.