Discriminant function analysis of atlas and axis vertebrae of the toothed whale to facilitate species identification in zooarchaeological specimens

Abstract

Cetaceans have long been exploited as a key marine resource for subsistence in many parts of the world. The bones of cetaceans in archaeological deposits tend to be highly fragmented but can be distinguished from other mammals by their unique cancellous texture. However, distinguishing species of cetaceans from one another is difficult because of their high morphological similarity. The current study establishes taxonomic identification criteria based on the atlas and axis vertebrae of modern toothed whale species, using discriminant function analysis (DFA). Canonical DFA was effective at classifying the atlas and axis vertebrae of modern toothed whales in a hierarchical classification system, with a successful classification rate in the superfamily of 97.1%, the family of 89.6% and subfamily of 78.9%. Of the 18 modern, toothed whale species, six scored the highest correct identification rate for each species (100.0%), whereas four other species had reasonably correct identification rates (80.0-99.0%), suggesting that species level identification of these species is sufficiently reliable. Application of the canonical DFA to identify the atlas and axis vertebrate of a zooarchaeological toothed whale from the Kafukai-1 site, Rebun Island, Japan, resulted in a successful hierarchical classification at the species level. This paper demonstrates that the DFA approach is effective for identifying the atlas and axis vertebrate of toothed whales from archaeological sites. Further trials including the selection and reduction of further measurements are required for application to incomplete zooarchaeological materials to obtain correct classifications. K E Y W O R D S archaeofauna, atlas/axis vertebra, canonical discriminant function analysis, marine mammal, toothed whale 1 | INTRODUCTION Cetaceans (baleen and toothed whales) have long been exploited as a key marine resource for subsistence by coastal communities in many parts of the world since prehistoric times (Bernal-Casasola