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Leidy, J., 1870. [Remarks on ichthyodorulites and on certain fossil Mammalia].

Proc. Acad. Nat. Sci. Phil. 22:12-13.

Copyright 2002-2012 by Mike Everhart;  ePage created 01/26/2002; Updated 11/16/2012


LEFT: Type specimen of Xiphactinus audax (USNM V52),  a pectoral fin ray collected by Dr. George Miller Sternberg, Asst. Surgeon, U. S. Army, adapted from Leidy (1873, pl. XVII, figs. 9-10)

Webster's Dictionary, 1913 edition, defines an ichthyodorulite as "one of the spiny plates found on the back and tail of certain skates." It is otherwise defined as "fossil spine, plate, tooth or denticle in Elasmobranchii."]Figs. 9, 10. Xiphactinus audax. A pectoral spine, one half natural size. Fig 9. Inferior view. Fig. 10. Superior view.

USNM V52-1a.jpg (27961 bytes) Wherein, Professor Leidy describes the pectoral fin of a very large fish from Kansas and names it Xiphactinus audax. All things considered, this was probably a very poor type specimen to use as the basis of naming a new species. From this single spine, Leidy mistakenly identified Xiphactinus as a giant catfish. (See E. D. Cope's remarks below). In spite of such criticisms, Leidy's name had precedence over the one (Portheus molossus) proposed by Cope the following year (and published in 1872) after several, more complete specimens of this fish were discovered in the Smoky Hill Chalk of Kansas near Fort Wallace. This was one of the first vertebrate taxa to be described from the Kansas chalk (following Elasmosaurus platyurus Cope and Tylosaurus proriger Cope.  Note that Leidy also describes a specimen found by Dr. George M. Sternberg that almost certainly has to be a part of the pectoral fin of Protosphyraena perniciosa, but does not name it (Pers. comm., Manning, 2002).  

12                                       PROCEEDINGS OF THE ACADEMY OF

     "Descriptions of Fossils collected during the U. S. Geol. Survey under the charge of Clarence King." by F. B. Meek.   

     PROF. LEIDY exhibited specimens of ichthyodorulites, upon which he made the following remarks:

     XIPHACTINUS AUDAX. The genus and species are founded on an interesting specimen belonging to the collection of the Smithsonian Institution, and obtained from the cretaceous formation of Kansas by Dr. [George Miller] Sternberg. From the want of symmetry in the base of the specimen, I suppose it to have been the pectoral spine of some huge siluroid fish.

     It is a broad sabre-shaped weapon, in its present condition sixteen inches long, which is near its original length, if one may judge from the thinness and rounding of the border at the broken end. At its middle it is nearly two inches broad and almost seven and a half lines thick. It slightly narrows and becomes thinner towards the outer end, and becomes thicker and more narrow approaching the base. An inch and a half from the latter it is thirteen and a half lines thick and seventeen lines wide; and the same distance from the outer end it is the fourth of an inch thick and twenty lines wide. The anterior convex border is rounded at first, but becomes subacute at its outer part. The posterior concave border is rather more obtuse.

     A large groove commences back of the root, extending outwardly, becoming contracted and deeper, and opening to its bottom along the under part of the spine to its outer extremity. The bottom of the groove is irregularly pitted, and its upper surface formed by the overhanging posterior portion of the spine is transversely corrugated or striated. A similar but shallower groove commences in front of the root, and extending outwardly opens beneath the spine at the anterior half of its surface.

The upper surface of the spine is nearly flat and longitudinally striated, except at the outer part of the anterior border, where the striation is finer and curves forward. The root of the spine turns up into a sort of hook-like process, broken at the end. It has been about two and a half inches in height from a level with the inferior surface of the spine. The inner part of the root forms a vertical oblong convexity, the lower half of which is occurred by a raised facet, apparently an articular surface, upon which the spine moved.

[Ed. note: Earl Manning (pers. comm. 12/2002) has suggested that the following text in Prof. Leidy's remarks is probably the first description of Protosphyraena perniciosa, even though he erroneously associated the distinctive fin ray with the teeth of Ptychodus. Click here to see a photograph of a similar fragment.]

     Prof. Agassiz, in his Poissons Fossiles, has described specimens of ichthyodorulites from the chalk of Lewes, England, "which he referred to placoid fishes of the genus Ptychodus, "from the circumstance of their constant occurrence in the same localities " as teeth upon "which the genus was first established, These rays are especially remarkable for their segmented character, "Instead of being composed of a single piece, as in other genera, they consist of flat rods, or rather broad, thick plates intimately united but rendered distinct on the surface of the ray by longitudinal grooves." Without question as to the reference of these rays, I exhibit several similar specimens from the cretaceous formation of Kansas, submitted to my examination by the Smithsonian Institution. The same collection of fossils, of which the rays were part, also contained many teeth of Ptychodus mortoni, but I am uninformed whether they were found in association.

     The specimens are probably two fragments of the same ray, but an intermediate piece is wanting, and they are imperfect at the opposite ends. They also appear to be somewhat compressed from pressure. As a whole the ray is flat at the sides, with a thickened, convex, posterior border, and an acute dentated or festooned anterior border. The dentate processes are composed of a denser tissue than the rest of the ray, and are thickened in a line from the point to the base, The body of the ray is composed of longitudinally oblique bars ascending from the posterior border to the bases of the dentate processes in which they are merged. The longer and broader fragment is four and three-


                              NATURAL SCIENCES OF PHILADELPHIA.                                  13

quarter inches long and three-quarters of an inch wide, gradually tapering to seven lines, and is provided, with about seven and a half dentate processes. The other fragment is three and three-quarter inches long, seven lines wide below, and four lines at the broken apex; and is provided with nine dentate processes.

     The segmented condition of the ray recalls to mind a singular fossil specimen formerly described by me as the portion of a jaw of a fish to which the name of Edestus vorax (Journ. Acad. Nat. Sci. iii, 159, p I. 15) was given, and which also exhibits a segmented condition. This fossil, notwithstanding its jaw-like appearance furnished with shark-like teeth, I have always suspected was an ichthyodorulite (Proc. 1856, 301), and this suspicion is increased by an examination of the rays supposed to pertain to Ptychodus.

(remainder of article removed)



A Scientific Disagreement

An excerpt from page 175 of: Cope, E. D., 1871. On the fossil reptiles and fishes of the Cretaceous rocks of Kansas. Art. 6, pp. 385-424 (no figs.) of Pt. 4, Special Reports, 4th Ann. Rpt., U.S. Geol. Surv. Terr. (Hayden), 511 p.

Wherein Professor Cope disagreed with Leidy's identification of the pectoral spine and re-assigned Xiphactinus audax to the genus Saurocephalus on the basis of what he considered to be similar characters. In this case, Cope was using Saurocephalus incorrectly by attempting to lump Xiphactinus into an already existing genus. Saurocephalus Harlan 1824 is actually much smaller than Xiphactinus (and not at all closely related). Over the space of several years, Cope kept adding species to the genus Saurocephalus and Leidy kept removing them.




(Xiphactinus audax, Leidy. Proc. A. N. Sci. Phil., 1870, 12.)

     Established on a pectoral spine, supposed by Leidy to be that of a siluroid [catfish].  According to the description, it does not differ from that of  S. prognathus in more than specific characters. Thus the anterior margin is weakly serrate in the latter, a feature not described by Leidy in the former.   In S. audax the posterior portions of both sides are said to be grooved;  in that part of the spine of S. prognathus preserved, one surface only exhibits the groove in question, one of whose edges is obliquely ridged, as in S. audax.  From Kansas; museum Smithsonian.