The Haplolepidae, a new family of late Carboniferous bony fishes : a study in taxonomy and evolution. Bulletin of the AMNH ; v. 83, article 1

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New York : [American Museum of Natural History]
"A group of late Carboniferous actinopterygian fishes is described and referred to the genera Haplolepis Miller, 1892 (syn. Mecolepis Newberry, 1856, Eurylepis Newberry, 1857 - both preoccupied), and Pyritocephalus Fritsch, 1893 (syn. Teleopterina Berg, 1936). They are from six localities, of which the stratigraphical horizons can be stated by reference to Dix's succession of Coal-Measures floras. Haplolepis is divided into two new subgenera, Haplolepis (sensu stricto) and Parahaplolepis. The following species are described: Haplolepis (Haplolepis) ovoidea (Newberry), Linton, Ohio, Zone H-I (Syn. Mecolepis ornatissimus Newberry, Eurylepis minimus Newberry, Eurylepis macrops Newberry MS, ?Mecolepis serratus Newberry); Haplolepis (Haplolepis) cf. ovoidea (Newberry), Mazon Creek, Illinois, Zone H; Haplolepis (Haplolepis) aff. ovoidea (Newberry), Cannelton, Pennsylvania, Zone H; Haplolepis (Haplolepis) corrugata (Newberry), Linton, Ohio, Zone H-I (Syn. ?Eurylepis striolatus Newberry); Haplolepis (Haplolepis) attheyi, new species, Newsham, Northumberland, Zone E; Haplolepis (Parahaplolepis) tuberculata (Newberry), Linton, Ohio, Zone H-I (Syn. Mecolepis granulatus Newberry, Mecolepis insculptus Newberry); Haplolepis (Parahaplolepis) cf. tuberculata (Newberry), Mazon Creek, Illinois, Zone H; Haplolepis (Parahaplolepis) anglica (Traquair), Longton, Staffordshire, Zone F; Haplolepis (Parahaplolepis) aff. anglica (Traquair), Newsham, Northumberland, Zone E; Pyritocephalus sculptus Fritsch, Nýrany, Bohemia, Zone H-I; Pyritocephalus lineatus (Newberry), Linton, Ohio, Zone H-I; Pyritocephalus gracilis (Newberry and Worthen), Mazon Creek, Illinois, Zone H (Syn. Teleopterina improvisa Berg); Pyritocephalus comptus, new species, Mazon Creek, Illinois, Zone H; Pyritocephalus rudis, new species, Newsham, Northumberland, Zone E. In several cases it has been possible to make very detailed reconstructions of the dermal bones and the body, but remains of the endoskeleton are too bad for description. The fishes are shown to be closely related and sharply marked off from all other known Carboniferous Actinopterygii; the new family, Haplolepidae, is set up for their reception. It is shown that the family was probably derived from the lower Carboniferous Canobius, which in turn is derived through Mesopoma from a series of 'normal' palaeoniscoids allied to Rhadinichthys. The family was thus well separated from most Carboniferous evolutionary lines within the palaeoniscoids. It is shown that Aeduella Westoll is not a close relative of the Haplolepidae and that the resemblances are largely due to parallel evolution; and that Trissolepis Fritsch, of which the skull roof has been described as fenestrated in a manner similar to that of Pyritocephalus, is probably of normal palaeoniscoid structure with an entire skull roof. The subgenera of Haplolepis and Pyritocephalus are separate throughout their known range, but Pyritocephalus was certainly derived from an early Parahaplolepis. The comparative anatomy of the dermal bones, the body, and the fins is discussed in detail. Peculiar modifications of the skull roof and cheek, some of them independently undergone in different members of the group, are demonstrated. The development and significance of the paired fenestrations in the skull roof of Pyritocephalus are discussed. Attention is given also to the remarkable modifications of the snout, external nares, and opercular apparatus; to the presence of a flattened venter between the paired fins, associated with a modified course of the scale rows of the body; to the frequent development of very deep scales on the anterior flank; to the modifications leading to the extreme thinness of the scales; to the latero-sensory system, which is very fully developed, and includes main and accessory, together with dorsal and ventral, lateral lines, the last described for the first time in an actinopterygian; and to the significance of the structure and nature of the dermal fin rays and of the relative positions of the fins. Many of the characters demonstrated in Haplolepidae are to be found also in some members of the 'Holostei' and 'Sub-Holostei.' A critical discussion of the status of these unnatural groups leads to a general statement of a new hypothesis of the evolution of the 'holostean' condition, in which it is shown that the characteristic modification of the tail fin has happened independently in different lineages and is correlated with a great change in habitat and environment. This section is based largely on a consideration of the fish as a swimming organism. The geographical distribution of the Haplolepidae is remarkably extensive for so specialized a family. In particular, the highly specialized Pyritocephalus sculptus from Bohemia is extremely similar in all details to the contemporaneous P. lineatus from Ohio. An analysis of the probable conditions of deposition of the rocks yielding the fossils leads to the conclusion that the Haplolepidae were fresh-water fishes thoroughly adapted to life in stagnant swamps, and almost certainly incapable of migration by sea. The implications of such conclusions in the understanding of the distribution and nature of Coal-Measures swamps and on the theory of continental drift are considered. The faunas associated with Haplolepidae are shown to include certain peculiar Amphibia, the distribution of which is extremely closely correlated with that of the fishes. The fate of this 'facies fauna' is described, and the food relations of the various members are briefly noted"--P. 111-112.
121 p., 10 p. of plates : ill. ; 27 cm.
Includes bibliographical references (p. 115-120).