The structure and relationships of the paracanthopterygian fishes. Bulletin of the AMNH ; v. 141, article 3

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New York : [American Museum of Natural History]
"The aim of this work has been to discover whether the superorder Paracanthopterygii is a monophyletic group, and, if so, to find its limits and relationships. The supposed members of this superorder are the Percopsiformes, Gadiformes, Batrachoidiformes, Lophiiformes, and Gobiesociformes. The paper contains illustrated anatomical accounts of the living and fossil members of these groups, and detailed descriptions of the fossil percopsiforms Trichophanes (Oligocene, Aphredoderidae), Amphiplaga, Erismatopterus (both Eocene, Percopsidae), and Sphenocephalus (Upper Cretaceous, Sphenocephalidae), and the possibly related Asineops (Eocene). 2. Although no single character or combination of characters can be found which occurs in all paracanthopterygians and in no other fish, the conjunction of a distinctive type of jaw musculature and caudal skeleton in all living percopsiforms (percopsids, aphredoderids, amblyopsids), most gadiform suborders (gadoids, muraenolepoids, ophidioids), and batrachoidiforms (batrachoidids) justifies the hypothesis that these three orders are members of a monophyletic group distinct from the acanthopterygians. 3. The most distinctive feature of the paracanthopterygian jaw is the presence of a levator maxillae superioris muscle, which seems to be derived in phylogeny from the upper part of the outer division of the adductor mandibulae. The levator maxillae superioris originates on the palatoquadrate and inserts near the head of the maxilla, serving as a tensor which positions and restrains the maxilla during opening of the mouth. The presence of this muscle limits the degree of jaw protrusion; rather than a truly protrusile mouth paracanthopterygians tend to develop a large, circular gape by pivoting the maxilla and premaxilla. 4. Correlated with the presence of the levator maxillae superioris are a number of features of the skull and jaws, especially the tendency to develop a broad, shallow head, with consequent modifications of the skull roof, occipital condyle, and operculum. 5. A levator maxillae superioris muscle and jaws of paracanthopterygian type also occur in macrouroids and zoarcoids (the remaining gadiform suborders) and in antennarioid and some ceratioid lophiiforms. The remaining lophiiforms and the gobiesocids are without a levator maxillae superioris. Outside the Paracanthopterygii, a levator maxillae superioris is known to occur only in myctophid myctophoids and in some cyclopterid scorpaeniforms. 6. The paracanthopterygian caudal skeleton is characterized by the presence of a second ural centrum which is fused with the upper hypurals, two or fewer epurals, and a full neural spine on the second pre-ural centrum. This neural spine appears to be a primary structure, not the result of fusion between an epural and a neural arch. In addition to the percopsiforms, gadoids, muraenolepoids, ophidioids, and batrachoidids, a caudal skeleton of this type also occurs in at least one zoarcoid, although most zoarcoids and the macrouroids have the caudal skeleton reduced beyond recognition. It does not occur in lophiiforms or gobiesociforms, in which the caudal supports are fused in such a way that they resemble those of some advanced acanthopterygians. In Eocene and Cretaceous percopsiforms and in a few living gadoids the caudal skeleton is more primitive, having the upper hypurals autogenous (four upper hypurals in percopsiforms, three in gadoids). 7. Lophiids and gobiesocids, which lack the paracanthopterygian pattern both in the jaw musculature and the caudal skeleton, are linked with batrachoidids and more generalized lophiiforms by a large number of specializations, especially in the skull and shoulder girdle. 8. Apart from the primary specializations of the jaw musculature and caudal skeleton, other paracanthopterygian group trends is include: reduction in the bony cover of the cephalic sensory canals, the development of large, well-separated, exoccipital condyles, crowding of the anterior vertebrae, loss of supramaxillae, development of a deep notch behind the postmaxillary process of the premaxilla, shortening of the basibranchials so that the gill arches converge ventrally, development of projections on the heads of the posterior branchiostegals, increase in the number of pectoral radials, extension of the median fins, and reduction of the squamation. 9. Primitive features of paracanthopterygians that distinguish the group from the acanthopterygians include the presence of an adipose fin, pelvic splint (both in percopsiforms only), basibranchial teeth and second ural centrum, and the absence of a subocular shelf, predorsal bones, and a pelvic spine (a spinelet, questionably homologous with the acanthopterygian spine, present in some ophidioids, batrachoidids, lophiiforms, and gobiesocids). 10. Morphological and paleontological analysis of the paracanthopterygians indicates that the Percopsiformes, which existed in Cretaceous seas, stand near the origin of the group, occupying much the same position as do the Beryciformes among acanthopterygians. The closest relatives of the percopsiforms are the gadiforms, especially the merlucciid gadoids, with which they share many specializations. Within the Gadiformes, two main lineages are recognizable, the gadoid lineage and the ophidioid-zoarcoid lineage. These two lines must have separated in the Cretaceous. The position of the macrouroids and muraenolepoids in relation to these two lineages is still obscure: the Macrouroidei may contain convergently modified gadoid and ophidioid derivatives. The batrachoidiforms, lophiiforms, and gobiesociforms, the precise interrelationships of which remain to be discovered, form a separate lineage which must have diverged from the percopsiform-gadiform line during the Cretaceous or Paleocene. 11. The fossil record of the percopsiforms shows that some trends followed during the evolution of this group (and probably also in the gadiform and batrachoidiform-lophiiform-gobiesociform lineages) are the reverse of those typical of acanthopterygian evolution, notably reduction in the depth of head and trunk and reduction in fin spines and in spination of the skull bones and scales. A corollary of these trends is that the paracanthopterygians must have shared a closer common ancestry with the acanthopterygians than with the myctophoids. 12. The higher euteleosteans are envisaged as comprising three main radiations, the myctophoid radiation, stemming from aulopid-like ancestors, the paracanthopterygians stemming from percopsiform-like ancestors, and the acanthopterygians from berycoid-like ancestors. The distinctions between these are blurred by parallelism and convergence among the three (e.g., development of a subocular shelf, levator maxillae superioris, and fin spines in myctophid myctophoids; convergent resemblance between ophidioids and blennies and between batrachoidids and some scorpaeniforms) and by the existence of groups that appear to be equally ancient but do not fit easily into any of the three radiations, being in many ways intermediate between them (ctenothrissoids intermediate between myctophoids and acanthopterygians; polymixioids, lampridiforms, and Asineops intermediate between paracanthopterygians and acanthopterygians; atherinomorphs resembling but clearly distinct from acanthopterygians). 13. Some groups, previously placed in the protacanthopterygian order Cetomimiformes, seem to belong with these higher euteleosteans; the kasidoroids and cetomimoids are beryciforms, the ateleopoids, mirapinnids, and eutaeniophorids may be lampridiforms. 14. These conclusions are expressed in a new classification (p. 460) which incorporates a new category, 'series,' between order and superorder. 15. New taxa proposed are as follows: Sphenocephalus brachypterygius, new species; suborder Sphenocephaloidei (Percopsiformes); order Polymixiiformes (= Polymixioidei); series Polymixiomorpha, Salmopercomorpha, Atherinomorpha, Percomorpha; superorder Scopelomorpha (= Myctophiformes). 16. Erismatopterus endlichi Cope and E. rickseckeri Cope are synonyms of Amphiplaga brachyptera Cope and E. levatus (Cope), respectively. The family Trichophanidae Cockerell is synonymous with the Aphredoderidae; the family Erismatopteridae Jordan is synonymous with the Percopsidae; the family Kasidoroidae Robins and De Sylva is synonymous with the Gibberichthyidae. The suborder Amblyopsoidei is merged with the Aphredoderoidei; the members of the Cretaceous beryciform suborder Dinopterygoidei are distributed between the Lampridiformes and the Polymixiiformes"--P. 462-463.
p. 359-474, [27] p. of plates : ill. ; 27 cm.
Includes bibliographical references (p. 469-474).