The morphology of the mandibular coronoid process does not indicate that Canis lupus chanco is the progenitor to dogs

Abstract

The domestication of wolves is currently under debate. Where, when and from which wolf sub-species dogs originated are being investigated both by osteoarchaeologists and geneticists. While DNA research is rapidly becoming more active and popular, morphological methods have been the gold standard in the past. But even today morphological details are routinely employed to discern archaeological wolves from dogs. One such morphological similarity between Canis lupus chanco and dogs was published in 1977 by Olsen and Olsen. This concerns the "turned back" anatomy of the dorsal part of the vertical ramus of the mandible that was claimed to be specific to domestic dogs and Chinese wolves C. lupus chanco, and "absent from other canids". Based on this characteristic, C. lupus chanco was said to be the progenitor of Asian and American dogs, and this specific morphology has been continuously used as an argument to assign archaeological specimens, including non-Asian and non-American, to the dog clade. We challenged this statement by examining 384 dog skulls of 72 breeds and 60 skulls of four wolf sub-species. Only 20 % of dog mandibles and 80 % of C. lupus chanco showed the specific anatomy. In addition, 12 % of Canis lupus pallipes mandibles showed the "turned back" morphology. It can be concluded that the shape of the coronoid process of the mandible cannot be used as a morphological trait to determine whether a specimen belongs to a dog or as an argument in favour of chanco as the progenitor to dogs.

Keywords: Canis lupus chanco; Coronoid process; Dog; Domestication; Mandible; Morphology; Wolf.

Fig. 1

Category 1: Straight caudal border of the vertical ramus. The vertical line that coincides with the ventral part of the caudal border of the vertical ramus of the mandible does not cut through the dorsal caudal ramus

Fig. 2

Category 2: Straight caudal border with minimal tip curvature. The vertical line that coincides with the ventral part of the caudal border of the vertical ramus of the mandible coincides with the caudal border and does only cut through the tip of dorsal caudal ramus

Fig. 3

Turned back morphology. The vertical line at the caudal border of the vertical ramus of the mandible does not coincide with the border and cuts through a large part of the dorsal ramus

Fig. 4

A Canis lupus pallipes mandibular specimen with “turned back” morphology. Accession number ZMTAU1110 (George Wise faculty of Life Sciences, Israel)

Fig. 5

The Canis lupus chanco mandibular specimen without the “turned back” morphology. Accession number 18B458- NHB 2015- USNM00610 (Smithsonian Institution, USA). Photo: D. E. Hurlbert

Fig. 6

A mandibular specimen of an Asian/American dog without the “turned back” morphology. Top Alaskan Malamute specimen. Accession number 1051378-313/78 (Museum of Natural History, Bern, Switzerland). Bottom Akita Inu specimen. Accession number 1051382-523/82 (Museum of Natural History, Bern, Switzerland)