On the status of the ichnotaxon Mandaodonites coxii Cruickshank, 1986

Abstract

Three ichnotaxa have been established for putative bite marks on fossil bone: Mandaodonites, Heterodontichnites and Nihilichnus. The first of these ichnotaxa was established for a sigmoidal trend of 17 shallow impressions on the dorsal surface and 16 deeper impressions on the ventral surface of a Middle Triassic kannemeyeriid dicynodont femur from southern Tanzania. To date the only referred material remains the holotype. The diagnosis of this ichnogenus is problematic in that it is over-specific in its scope rendering it unlikely that additional material will be assigned to this taxon. Close analysis of the holotype reveals several flaws in the interpretation of this material as a trace fossil. Evidence of bone crushing features such as concentric or radial fractures associated with the impressions and compressed or splintered bone in the vicinity of the impressions are lacking. The impressions occur in a position on the femur that would have necessitated placement of either the ball of the femur or the distal femur in the esophagus of a predator/scavenger, which is an unlikely scenario. Other evidences of predation or scavenging are lacking on the femur and on associated skeletal material. The impressions occur in a long fracture that offsets the bottom half and top half of the femur. It is the position of this contribution that the ichnotaxonomic name Mandaodonites coxii identifies a combination of non-biogenic, fracture-related pits and impressions inadvertently enhanced during fossil preparation. It is thus nomen erratum and should be abandoned.

Keywords:

• Mandaodonites
• Heterodontichnites
• Nihilichnus
• bite mark
• osteic

Acknowledgements

I am grateful to Spencer Lucas, an anonymous reviewer, Ichnos Associate Editor Hendrik Klein and Editor Murray Gingras for thorough reviews and note that the opinions expressed herein do not necessarily reflect their views. Travel to Cambridge was supported by an NSERC Discovery grant.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Natural Sciences and Engineering Research Council of Canada.