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Hipparionyx minor shirleyi
Phylum: Brachiopod
Genus: Hipparionyx Species: Hipparionyx minor shirleyi Location found: Baton River |
Hipparonyx minor was first identified in the Devonian rocks in the Baton River area by Shirley in 1938; the additional element 'shirleyi' was added more recently by Gratsianova et al. (2001). It is a reasonably distinctive species with a more-or-less semi-circular outline, that extends beyond the half-cirle, so that it narrows again towards the hinge. The profile is rather flat and the ribs are numerous and very fine. A full description, from Shirley (1938) is given to the right.
In the Reefton area, the same genus has also been noted, though identification to species level has not been achieved, and no specimens are yet included in this collection. Further Reading: Shirley, J. 1938 The fauna of the Baton River beds (Devonian), New Zealand. Quarterly Journal of the Geological Society 94, 459-506. |
Description by Shirley (1938): Outline subcircular; ventral va]ve convex only near the umbo, slightly concave over the rest of the valve, hinge-line somewhat shorter than the greatest width; dorsal valve very convex. Ornament of fine ribs generally radial, but those near the hinge bend back to meet it at an angle, increasing by intercalation, spaced at about 18 in 10 mm. at the periphery. The ribs are crossed by fine concentric lines which are absent from the interspaces . . . Interior ventral valve: teeth supported by strong dental plates diverging at about a right angle and continued anteriorly into ridges completely surrounding the muscle impressions; in old-age specimens this ridge can be very pronounced. Adductor impressions relatively small, surrounded by the flabellate divaricator impressions which end at about the half- length of the shell. In the gerontic stage the divaricator impressions are striate with a crenulate border. A very short but stout median septum is developed in the umbonal cavity. Interior dorsal valve: cardinal process bilobed, very prominent, the two prongs passing well down into the ventral umbonal cavity; the process passes forward into a septum about one-third the length of the shell; crural bases almost parallel with the hinge, medianly joining ridges which enclose the dental sockets. |