Ramsay Heatley Traquair

“ The genus Palæoniscus has been made to include an immense number of species, which are, indeed, referable to more than one generic type, some of them actually not being Palæoniscidæ at all. Authors have, in point of fact, been only too apt to refer nearly every small rhombic-scaled fusiform-shaped ganoid fish from Upper Palæozoic rocks to Palæoniscus, without inquiring too narrowly into how far its structure agrees with that of the original type of the genus, and have even sometimes overlooked distinctions of more than generic importance. ”

“ The caudal fin, however, is not the only one which shows a marked deviation from the Palæoniscus type. It at once strikes the eye that the fulcra in front of the dorsal and anal fins are fewer in number, set at lower angles, and very much larger and stronger than in any of the Paæeoniscidæ—that they are, in fact, proportionally nearly as powerfully developed as in Ischypterus, though they diminish in size more gradually, from the origin to the apex of the fin, than in the latter genus. Behind the margin of strong fulcra only about ten rays are counted in the dorsal, and eight in the anal ”

“ I. Type of Palæoniscus Freieslebeni, Ag. (Genus Palæoniscus restricted) . The body is elegantly fusiform; the scales moderate, sculptured; the fins of comparatively small size; the dorsal situated opposite the interval between the ventrals and the anal; the rays of the pectoral are articulated; the fin-fulcra are small but easily recognizable. The suspensorium is very oblique, the operculum and interoperculum broad; the mandible is slender. The teeth are small, conical, sharp, and of different sizes, the smaller ones being more externally placed, but without specially prominent laniaries. ”

“ But although Giebel's conceptions of its relationship to other Palæoniscoid forms were thus somewhat imperfect, I have convinced myself, by a careful examination of the type specimens in the museum of the University of Halle, that the genus Elonichthys is quite tenable, and that to it the Amblypterus nemopterus of Agassiz and the other forms referred to above as specially allied to that species are properly referable. Though closely resembling Rhabdolepis, it differs in the absence of the subopercular plate; the operculum is also usually more largely developed ”

“ In one specimen I have seen similar teeth, apparently in more than one row, in the upper part of the mouth; but, from defective preservation, it is hardly possible to tell on what bone they are situated. The orbit has not the remarkably anterior position characteristic of the Palæoniscidæ, but is situated nearly right above the articulation of the lower jaw. Beyond pretty distinct indications of frontals and parietals, and of a powerfully developed parasphenoid, no further details of the osteology of the head are revealed by such specimens of Ischypterus as I have had at my disposal. ”

“ The nearest approach to Pygopterus in general form is made by some of the much smaller Carboniferous fishes which I include in the genus Rhadinichthys; but in all of these the scales are proportionally larger and thicker, the caudal body-prolongation is not so powerfully developed, and the anal fin, though considerably "échancrée," is not prolonged backwards in the same manner. ”

“ Gyrolepis tenuistriatus, Ag., on the other hand, was referred by Giebel to Amblypterus. He therefore proposed the total abolition of the genus Gyrolepis, uniting and renaming the species G. Albertii and biplicatus as Colobodus varians, Giebel [30] , and in like manner the species G. tenuistriatus and maximus as Amblypterus decipiens, Giebel [31] , and in each case apparently without the smallest regard to priority of specific nomenclature. The accuracy of Giebel's reference of the two former species to Colobodus was questioned by Eck [32] . ”

“ In Ischypterus the body is rather deep, and strongly arcuated in front of the dorsal fin; the scales are rhomboidal and smooth; but along the middle line of the back, from the occiput to the dorsal fin, there extends a row of peculiarly shaped median scales, like those in Semionotus Bergeri, Ag., and Lepidotus minor, Ag., these being somewhat spur-shaped, with posteriorly directed points, and imbricating over each other from before backwards. ”

“ III. Type of P. striolatus, Ag. (Genus Elonichthys, Giebel) . Here are included P. striolatus, Robisoni, and Egertoni, fishes with large median fins, sculptured scales, powerful tail, very oblique suspensorium, and, as regards the dentition, possessed of a row of distinct conical laniaries internal to a series of smaller teeth. It is difficult to conceive why Agassiz placed these species in the genus Palæoniscus, while at the same time he described, as has been already shown, certain closely allied forms from the Wardie shales as Amblypteri. ”

“ The scales of the body are smooth ; and those of the flank remind us, in their form, more of the scales of Pholidophorus than of Palæoniscus.
These details render it sufficiently evident that the fishes entitled, by Mr. Kirkby, Palæoniscus varians, Abbsii, and altus belong neither to the genus Palæoniscus, nor even to the family of Palæoniscidæ. ”

“ As already stated, it is quite evident that the fish to which these remains belonged is a member of the family Palæoniscidæ; and the form and thickness of the scales, with their very large anterior covered area, and the nature of their sculpture, along with the peculiar tubercular ornamentation of the cephalic and shoulder-bones, point out, as it seems to me, that Acrolepis is the genus to which it should be referred. The scales of the Permian A. Sedgwickii are quite similar in shape, though proportionally smaller and with fewer ridges. ”

“ Body large, elongate ovate; fins very large, with fulcral scales, anal fin of moderate depth and very long, dorsal of moderate length, nearly opposite or a little in front of the anal fin; ventrals small, slightly in front of the middle of the body; pectorals moderately small, falcate caudal very large, deeply notched; upper jaw a little longer than the lower; endoskeleton strong, vertebræ usually wider than long ”

“ Although the original examples of this species, collected by Lord Greenock, and now in the Museum of the Royal Society of Edinburgh, were thus imperfect, there is hardly any Carboniferous fish concerning whose structure I have been able to acquire more complete information, my own collection being especially rich in its remains, and many other specimens being in the Edinburgh Museum of Science and Art. ”

“ Until therefore the cranial osteology and the dentition of these forms is better known, I would propose that the Palæoniscus catopterus of Agassiz be included in the genus Dictyopyge of Sir Philip Grey-Egerton. Of the closeness of the alliance there can be hardly a doubt ”

“ VII. Type of Palæoniscus catopterus, Ag. (? Genus Dictyopyge, Egerton) . This little species, from the Triassic Red Sandstone of Phone Hill, co. Tyrone, was originally named by Agassiz, but was not described by him. Sir Charles Lyell, however, in referring to it in connexion with certain American Triassic forms, says concerning it:—"The Irish Palæoniscus catopterus of Roan or Rhone Hill, referred by Col. Portlock to the Trias, is a true Palæoniscus, and not allied generically either to the Ischypterus of Egerton or the Catopterus of Redfield" [26] . ”

“ The pectoral fin is of considerable but not excessive size; its principal rays are, like those of Oxygnathus and Rhadinichthys, unarticulated till towards their terminations; the ventral is rather small. The anal commences rather remote from the caudal; it is high and acuminate in front ”

“ But, unfortunately for this diagnosis, the fins of Palæoniscus are no more covered with scales than those of any other genus belonging to the family, nor are the fulcra wanting in any of the species which have been classed under Amblypterus [12] , and, finally, it has been shown that more than one of Agassiz's "Amblypteri" possess large laniary teeth quite similar to those of Elonichthys. ”

“ The rays are comparatively few in number, those of the upper lobe gradually diminishing in length towards its extremity; and the fulcra, which run along the margin of the lower lobe, are nearly as strong as the V scales, usually also called fulcra, which border the upper one above. ”

“ The anterior covered area overlapped by the scale in front is extensive, being 3/16 inch in breadth; its lower margin is more oblique than that of the sculptured portion, with which it consequently forms an obtuse angle; above it is produced into a prominent pointed process, where it coalesces with the narrower covered area of the upper margin, overlapped by the scale next above. ”

“ Quenstedt, in his 'Handbuch der Petrefactenkunde.' agrees with Giebel as to the reference of G. Albertii and G. maximus to Colobodus; Tholodus, v. Meyer, he also considers as belonging to the same type, but is inclined to consider these forms as related, not to the Pycnodonts nor to the heterocercal Ganoids, but to Lepidotus [33] . In the same work he expresses himself in a rather guarded manner regarding the reference of G. tenuistriatus to Amblypterus [34] . ”

“ D. opposée à l'espace entre les V. et l'A. Ecailles médiocres; quelques espèces en ont d'assez grandes, et le corps plus large et plus court que les autres. Il y a toujours de grosses écailles impaires en avant de la D. et de l'A" [2] .
Both genera are elsewhere stated to have the teeth "en brosse extrêmement fine" or "en brosse" [3] . The statement as to the absence of fulcra on the fins of Amblypterus, save on the caudal, was corrected a few pages further on, though they are here said to be "si extraordinairenient petits qu'on peut à peine les entrevoir à l'œil nu" [4] . ”

“ These specimens, some of them entire, confirm the doubts which Agassiz himself entertained regarding its generic position; and accordingly in 1875 [53] I proposed for its reception the new genus Nematoptychius. The configuration of the scales is alone sufficient to demand its separation from Pygopterus. Those of the flanks are much higher than broad ”