Reaching as much as 12.5 centimetres (4.9 in) in length, Odontogriphus is a flat, oval bilaterian which apparently had a single muscular foot and a "shell" on its back that was moderately rigid but of a material unsuited to fossilization.
It is thought that Odontogriphus's feeding apparatus, which is "nearly identical" to Wiwaxia's, is an early version of the molluscan radula, a chitinous "tongue" that bears multiple rows of rasping teeth.
In the 1970s Simon Conway Morris re-examined the specimen and tentatively concluded that it was a swimming lophophorate, in other words related to the ancestors of molluscs, annelid worms and brachiopods.
Caron, Scheltema et al. (2006) interpreted this as evidence that the animals had on their backs "shells" that were rigid enough to resist whatever stresses distorted the internal features, but were not tough enough to be preserved by fossilization – similar, for example, to finger nails.
[4] Caron, Scheltema et al. (2006) found evidence of a circular mouth on the underside, with two and occasionally three tooth-bearing structures that they interpreted as a feeding apparatus and very similar to that of Wiwaxia.
[2] The fossils showed signs of a thickened central structure that Caron, Scheltema et al. (2006) thought was on the underside and probably represents a muscular sole that was a little over half as wide as the whole animal.
Kimberella Odontogriphus Wiwaxia Halkieriids Neomeniomorpha / Solenogasters(Aplacophora) Polyplacophora Other crown group molluscs In line with this classification they interpreted the dark patches round the foot as gill-like ctenidia, another feature of some molluscs; and the sediment that sometimes appeared in the fossils between the foot and supposed ctenidia suggested the presence of a mantle cavity.
He also doubted whether the two tooth-rows of Odontogriphus and Wiwaxia could perform all the functions of the multi-row radula – rasping, capturing scraped food, sorting it and transporting it to the gullet.
[13] While Butterfield agreed that the dark patches round the foot served as gills, he denied that they were similar in structure and mode of development to molluscan ctenidia.
In his opinion the flattened remains of Odontogriphus were formed by relatively tough extracellular secretions, such as jaws, bristles and toughened skin, and do not include purely or primarily cellular tissues, such as muscles or gonads.
He therefore thought the respiratory organs round the edge of Odontogriphus' foot could not be molluscan ctenidia, since these are covered by purely cellular tissue.
[13] Caron, Scheltema, et al. (2006) had suggested that the wrinkles on the top surfaces of Odontogriphus specimens were caused by the rippling contractions of a mollusc-like muscular foot.
In answer to Butterfield's claim that the respiratory organs round the foot could not be molluscan ctenidia because these mainly cellular structures would not have fossilized in the Burgess Shale conditions, they wrote that: fairly soft cellular tissue belonging to the stomach is fossilized in many Odontogriphus specimens; some molluscan gills are stiffened by non-cellular material, for example in polyplacophorans.
They pointed out that the wrinkles that appear across the body in views from the top occur only in the mid-section, and there is no sign that the tough "shell" plate on the animal's back was segmented; hence in their opinion Odontogriphus could not have been an annelid.
They criticized Butterfield's main argument for "shoehorning" Wiwaxia into the polychaetes, that its sclerites were secreted by microvillae; such structures, they wrote, were also found in several groups of molluscs.