Data from: Evolutionary origins of teeth in jawed vertebrates: conflicting data from acanthothoracid dental plates (‘Placodermi’)

Placoderms (Devonian fossil fishes) are resolved phylogenetically to the
base of jawed vertebrates and provide important evidence for evolutionary
origins of teeth, particularly with respect to the Arthrodira. The
arthrodires represent a derived group of placoderms; the dentition of
other more primitive placoderms such as the acanthothoracids is less well
known. Articulated acanthothoracid dental plates are rare; x-ray computed
tomography of a single, unique specimen, along with 3D segmentation of
bone, oral denticles and vascular spaces, provides intrinsic developmental
and topological information relevant to tooth origins. Recently, a
disarticulated element was identified as a dental plate of the
acanthothoracid Romundina stellina, with synchrotron microtomography
providing characters to comment on ongoing debates regarding the evolution
of teeth. We used segmental quantitative methods to re-analyse this data,
for comparison to the articulated and unquestionable acanthothoracid
dental plates above. We demonstrate substantial differences between these,
disputing the identity of the isolated plate of R. stellina as a dental
plate, and thus its relevance to questions of tooth evolution.