Browsing by Author "Nelson, Gareth J."
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Item Cephalic sensory canals, pitlines, and the classification of esocoid fishes, with notes on galaxiids and other teleosts. American Museum novitates ; no. 2492(New York, N.Y. : American Museum of Natural History, 1972) Nelson, Gareth J."In both the Esocidae and the Umbridae, phyletic rends involve reduction of cephalic sensory canals and elaboration of pitlines. Advanced characters of this sensory system indicate interrelationships among Recent species, most notably a close relationship between Dallia and Umbra. The Eocene Palaeoesox and the Oligocene Proumbra are attributable to the Umbridae and are probably closely related to Umbra. The historical biogeography of the Umbridae may involve a secondary distribution (Umbra limi, U. pygmaea) in east North America. A relationship between esocoids and galaxiids is unsupported, but a relationship between clupeomorphs and elapomorphs is supported by the structure of the cephalic canal system"--P [1].Item Gill arches and the phylogeny of fishes : with notes on the classification of vertebrates. Bulletin of the AMNH ; v. 141, article 4(New York : [American Museum of Natural History], 1969) Nelson, Gareth J."Study of adult gill-arch dentition of Recent and some fossil fishes suggested that the condition primitive for gnathostomes included numerous dermal elements, initially small but capable of growth. During evolution these small units apparently were organized into specialized structures of several types, through processes involving fusion between initially separate dermal elements, and in some cases fusion between the dermal skeleton and visceral endoskeleton. Advanced types of gill-arch dentition were found to characterize most of the major groups of fishes. These types, combined with characters of the gill-arch endoskeleton and related muscles, provided a basis for discussion of the phyletic interrelationships of all major fish groups represented in the Recent fauna. Concerning relationships, conclusions reached are in essential agreement with those of earlier workers. In addition, the basic branching of the gnathostomes appears to be consistent with the sister-group model of Hennig. On the basis of this agreement and consistency it was possible to propose a revised higher classification of fishes, proceeding from the assumption that sister-group relationships among Recent organisms must be expressed in the main outlines of a phyletic classification. Because it is generally agreed that tetrapods are related to rhipidistian fishes, it was possible to extend the classification to include the major groups of Recent tetrapods. The final result was a revised higher classification of the superclass Gnathostomata in which the major groups are arranged not arbitrarily but according to their probable phyletic interrelationships"--P. 535.Item The hyobranchial apparatus of teleostean fishes of the families Engraulidae and Chirocentridae. American Museum novitates ; no. 2410(New York, N.Y. : American Museum of Natural History, 1970) Nelson, Gareth J."This study completes a review of hyobranchial structure for Recent fishes of the order Clupeifromes. Its results support previously suggested phyletic trends involving reduction in number of branchiostegal rays, reduction and loss of gill-arch dentition, and elaboration of epibranchial organs within clupeiform fishes. Certain advanced characters of the gill arches characterize some of the major groups of Cluepiformes. On this basis it has been possible to arrive at a more precise conception of the interrelationships of these major groups. One result has been the splitting off of the Pristigasteridae from the Clupeidae. The problem of subdividing the families Engraulidae and Clupeidae is discussed from the standpoint of gill-arch structure"--P. 27.Item Infraorbital bones and their bearing on the phylogeny and geography of osteoglossomorph fishes. American Museum novitates ; no. 2394(New York, N.Y. : American Museum of Natural History, 1969) Nelson, Gareth J."The primitive condition of the teleostean infraorbital series probably included seven separate bones from the antiorbital to the dermosphenotic. The anterior four bones probably enclosed more than one neuromast each, but the posterior three bones probably enclosed only one neuromast each. Reduction both of bone and neuromast numbers seems to have occurred during the evolution of most teleostean groups. The primitive condition of seven infraorbital bones occurs in at least some members of all major teleostean groups except the Osteoglossomorpha. It is suggested that the osteoglossomorph condition, typically of six or fewer bones, has resulted from secondary fusion between two of the middle bones of the series. Infraorbital and other evidence, primarily the structure of the caudal fin, indicate that the Recent Osteoglossomorpha constitute a monophyletic group, and suggest certain interrelationships among the members of that group. Nevertheless, some interrelationships remain problematical. For this reason a satisfactory phyletic classification of the Osteoglossomorpha and a comprehensive theory of their geographic history are not yet attainable"--P. 31-32.Item Notes on the structure and relationships of certain Cretaceous and Eocene teleostean fishes. American Museum novitates ; no. 2524(New York, N.Y. : American Museum of Natural History, 1973) Nelson, Gareth J."Advanced characters of the lower jaw suggest that the Eocene Phareodus is an osteoglossine, the Cretaceous Ichthyodectiformes (Ichthyodectidae and Saurodontidae) are taeniopaedians, the Cretaceous Pachyrhizodontidae are clupeomorphs or euteleosteans, the Cretaceous Bananogmiidae are taeniopaedians, and the Cretaceous and Eocene Diplomystus agree with Recent Clupeidae and Chirocentridae. It is suggested that Phareodus (as Phareodontini) be included in the Osteoglossinae, and that the Ichthyodectiformes, Pachyrhizodontidae, and Bananogmiidae be classed as Teleostei, taxa incertae sedis. Advanced characters of the caudal skeleton of Pachyrhizodus and Bananogmius may prove useful in recognizing related forms"--P. [1].Item Paralogy in cladistic biogeography and analysis of paralogy-free subtrees. American Museum novitates ; no. 3167(New York, N.Y. : American Museum of Natural History, 1996) Nelson, Gareth J.; Ladiges, P. Y. (Pauline Y.)Item Pharyngeal denticles (placoid scales) of sharks, with notes on the dermal skeleton of vertebrates. American Museum novitates ; no. 2415(New York, N.Y. : American Museum of Natural History, 1970) Nelson, Gareth J."Within the buccopharyngeal cavity of many Recent sharks, there occurs a well-developed dermal skeleton, consisting of numerous, independent, non-growing denticles (placoid scales). It is apparent that the extent of this dermal skeleton, from the jaw margin to the pharyngo-esophogeal boundary, is a feature primitive for the Gnathostomata. Secondary reductions in the extent of this dermal skeleton are apparent in some Recent sharks. In others, pharyngeal denticles participate in the formation of specialized structures (pharyngeal pads), apparently analogous to the consolidated pharyngeal tooth plates of teleostomes. These observations lead to the hypothesis that the dermal skeleton of modern elasmobranchs is primitively subdivided, that is, in a primary micromeric condition. The relevance of this hypothesis is discussed in the context of a comparative theory of the dermal skeleton of vertebrates"--P. 24.Item The species of gizzard shads (Dorosomatinae) with particular reference to the Indo-Pacific region. Bulletin of the AMNH ; v. 150, article 2(New York : [American Museum of Natural History], 1973) Nelson, Gareth J.; Rothman, M. Norma."The Indo-Pacific fishes commonly called gizzard shads include two tribes (the Anodontostomatini and Clupanodontini) and at least 12 species (Anodontostoma chacunda, Gonialosa manmina, G. modesta, Nematalosa arabica, N. come, N. erebi, N. galatheae, new species, N. japonica, N. nasus, N. vlaminghi, new combination, Clupanodon punctatus and C. thrissa). These species are generally better defined and more easily recognized by nonmeristic characters than by counts of scales, fin rays, vertebrae, ventral scutes, and predorsal bones. The North American gizzard shads include one tribe (Dorosomatini) and, as currently recognized, five species (Dorosoma anale, D. cepedianum, D. chavesi, D. smithi, and D. (Signalosa) petenense), defined primarily on the basis of meristic characters. This paper reviews the taxonomy of the Indo-Pacific species and provides a key for their identification, an account of their variation and distribution, and an analysis of their scientific literature. For North American species, references to recent literature are included. The gut of the gizzard shads differs from that of other clupeoids in having a third primary flexure. The tribes recognized are based partly on the variations of the third flexure"--P. 135.