Iowa Geological Survey (Volume 18) (Paperback)

This historic book may have numerous typos or missing text. Not indexed. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. 1908. Not illustrated. Excerpt: ... ter of the superficial ornamentation. The suture lines, however, are less undulating than in Coccosteus, the articulation with the abdominal armor is much stronger, the pineal is partly in contact-with the centrals, and the dentition is characteristically Dinichthyid, with strongly developed vomerine teeth. The anterior margin of the lower dental plates is developed into a prominent beak, and the superior or functional margin is strongly denticulated; the posterior extremity of the splenial is broad and spatulate. The suborbitals are unusually wide and massive, and the rostral seems to have been laterally expanded in front. The dorsomedian bears the usual inferior keel, its terminal process being given off at a slight distance in advance of the posterior margin. FlQ. 27. Pig. 27. Dinichthys halmodeus (Clarke). Marcellus shale (Erian); New York. Restoration of headshield and dorsal armoring of trunk, x 4. ADL, anter-odorso-lateral; DM, dorso-median; EO, external occipital; M, marginal; MO, median occipital; P, pineal; PDL, postero-dorso-lateral; R, rostral; SO, suborbital. Original in New York State Museum. In the detailed and in most respects very accurate description of the holotype given by the original author, it is stated that the dentition presents "an aspect highly similar" to that of Dinichthys, and comparisons are instituted between it and D. herzeri, which also has the functional margin of upper and lower plates denticulated. This resemblance of jaw-parts is of sufficient weight, in our opinion, to justify the transfer of the species from Coccosteus, where it was doubtfully placed by Ur. Clarke, to Dinichthys. Of special significance from a taxonomic standpoint are the vomerine teeth, which are described as follows by the same author: "Each is con...