Diclonius pentagonus, Cope, 1876

Cope, E. D., 1876, Descriptions of some vertebrate remains from the Fort Union beds of Montana, Proceedings of the Academy of Natural Sciences of Philadelphia 28, pp. 248-261 : 253-254

Diclonius pentagonus , gen. et sp. nov.

Char. Gen. - Herbivorous dinosaurians, in which the teeth are elongate and witlhout distinct root, and present dense material only on one side of the crown (the " front "), whose section produces a cutting edge. The other face of the tooth (the " back ") is coated with cementum, and is absorbed during the protrusion of the successional tooth from below, which thus rises from "behind. " In the antero-posterior direction the teeth are protruded alternately, and the lower parts of the crowns are contracted to give space for the apices of the adjacent young teeth. In the type of the genus there is but a single series of teeth .

In the known species of this genus, the denise face ("front ") of the crown presents a longitudinal keel, but this is not necessarily a generic character. The terms " front " and " back " are not intended to be accurate, as the faces so termed are either external or internal,the direction being probably reversed in the two jaws.

This genus is allied to Hadrosaurus and Cionodon . From the former it differs in the mode of succession of the teeth, which, as determined by Prof. Leidy in that genus, is from the " front " of the base of the tooth, whereas, in Diclonius , the succession is as in Cionodon, from the "posterior " base of the tooth. This arrangement allows of a more continuous use of the dense face than in Hadrosaurus , where that face terminates as the young crown rises into functional position. A species from the Fort Union bad lands of the Judith River was described by Dr. Leidy as Trachodon mirabilis . Specimens of this species from the locality furnishing those of Diclonius , present the mode of succession ascribed by that author to Hadrosaurus , to which genus he afterwards referred the species under the name of H. mirabilis .

The dentition of species of this genus shows that but one tooth in mature functionial use existed in a line transverse to the axis of the jaw at one time, and that alternating with these, one partially protruded crown, and one stump of a crown, present masticating surfaces in transverse relation. The formula for this genus should then be written 2 -1, while in Cionodon it is 3 -3- 2.

The type of this genus exhibits a mode of nutrition of the young teeth similar to that seen in the genus Saurocephalus among fishes. The bone is perforated by a series of foramina, each of which conveyed an artery directly into the base of the growing crown.

Char. Specif. - The front of the crown is divided longitudlinally by a prominent median keel and the borders are not serrate. Thie keel is only moderately prominient at the lower part of the crown. The back of the crown is divided inito three faces by two straight longitudinal parallel solid angles, and the crown is contracted near the base by the lateral bevels for the adjacent growing teeth, All these faces are covered by cementum,whose roughness is granular in character. The external surface of the jaw-bone has precisely the same clharacter, so that the apices of the teeth only appear as prominences of its border.

The typical specimen is that of an individiual of moderate dimensions; measurements of a tooth of a gigantic individual are given below.