Description
{{{3}}} {{{3}}} {{{3}}} {{{3}}} {{{3}}} {{{3}}} {{{3}}} {{{3}}} {{{3}}} Diagrammatic reconstruction of Odontogriphus: top at left, underside at right.Odontogriphus was apparently a very rare species, accounting for less than 0.5% of the individual organisms found in the same fossil beds. Most of the fossils consist of two parts of a split block of rock, the upper part giving a "casting" of the animal's upper surface and the lower giving one of its underside.
Odontogriphus was a flat-bodied animal ranging from 3.3 millimetres (0.13 in) to 125 millimetres (4.9 in) in length, with parallel sides and semi-circular ends. The specimens examined by Caron, Scheltema et al. (2006) had the same ratio of length to width irrespective of size. The body outlines are bilaterally symmetrical in all fairly complete specimens, even those in which internal features were preserved asymmetrically. 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. Relatively broad wrinkles, parallel to each other and usually straight, run across the central region of the body in some specimens.
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. Odontogriphus’s feeding apparatus was located on the midline, about 15% of the total body length from the front edge of the fossils. The mouthparts comprised two to three rows, each comprising about two dozen carbonaceous teeth arranged symmetrically about a medial tooth, with one or two lateral teeth substantially smaller than the central teeth. The teeth operated by passing around an underlying "tongue", with the tooth rows deforming as they did so. The teeth probably scooped through the sea-floor mud, feeding on any detritus within it.
On either side of the feeding apparatus there is a circular structure that Caron, Scheltema et al. (2006) interpreted as salivary glands. They also found evidence of other parts of the digestive tract: a gullet connecting to the rear of the mouth; a relatively short stomach; and a straight much longer intestine, ending at an anus near the rear of the underside. A pair of structures on either side of the intestine and a little behind the stomach may have been gonads or digestive organs.
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. It was U-shaped, with the "open" end behind the mouth and the rounded end a little forward of the animal's rear edge. The anus apparently was slightly ahead of the rounded end. All the edges of the "foot" except the front were surrounded by darker patches, which are sometimes separated from the rest of the body by a thin layer of sediment.
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