The skin of the rachitomous amphibian Eryops

Abstract

ABSTRACT. The skin of a “mummified” Specimen of Eryo‘ps is described; its surface consists of a pattern of oval elevations which are scales ossified incompletely in a series of concentric rings. N most instances little is known of the dermal covering of fossil amphibians. In this class of vertebrates the continu- ous bony armor of the ancestral crossopterygians has been greatly reduced. In the living orders bony scales have been completely lost, apart from deeply-buried vestiges in the coe— cilians and occasional secondary ossifications, and the skin is typically smooth except for accretions of horny material in the more terrestrial anurans. In fossil members of the class the ventral bony scales were retained, and transmitted to the rep- tiles, in the reduced form of gastralia or abdominal ribs. In a few of the smaller Carboniferous types, such as Ophz'derpeton (Steen, 1931, p. 876; 1938, p. 222) impressions of presumed dorsal scales have been preserved. In general, however, we have no data concerning skin texture or composition in fossil amphibians. Such a common form as Eryops has been restored with the skin shown in variable fashion from a smooth condition to a rough and warty one. ' In recent months one of us (R. V. has been engage-d in the preparation of a nearly complete articulated skeleton of Eryops C. Z. 1539) collected by L. I. Price in the Belle Plains Formation near Fulda, Baylor Co., Texas. The speci- men was found, as is commonly the case, in a variegated clay. Over much of the axial skeleton, there was further present close to the bone a thin layer of yellow—brown grainy matrix of a resistant nature. This covered nearly the entire surface of the neural spines and the outer surfaces of the ribs but (signifi- cantly, it now appears) was absent from the inner surfaces of the ribs. No particular attention was paid to this material during preparation of the trunk elements. However, while cleaning the tail (found complete and articulated) it was dis- covered that when the matrix was given a routine treatment by hydrochloric acid followed by vigorous brushing with a fine