Browsing by Author "Gould, Stephen Jay."
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Item Asiatic Mesonychidae (Mammalia, Condylarthra). Bulletin of the AMNH ; v. 132, article 2(New York : [American Museum of Natural History], 1966) Szalay, Frederick S.; Gould, Stephen Jay.; Central Asiatic Expeditions (1921-1930)"The subfamily Mesonychinae is rediagnosed. Two new genera and species are described: Mongolonyx dolichognathus from the 'Irdin Manha' beds and Mongolestes hadrodens from the 'Ulan Gochu' Formation of Inner Mongolia. Harpagolestes was probably represented in Asia. ?Harpagolestes orientalis, new species, is described, and the published literature and most of the known specimens of this probably holarctic genus are re-evaluated. This is not, however, a substitute for a systematic revision of Harpagolestes. 'Mesonyx obtusidens,' reported by Gromova (1952), from the Naran Bulak beds of Mongolia, is a species of Pachyaena. Olsenia, a mesonychid described by Matthew and Granger (1925a) based solely on astragali, is not comparable to most of the known genera because of the scarcity of associations between mesonychid teeth and foot bones. The name 'Olsenia' is suggested to be a nomen dubium. A new subfamily, the Hapalodectinae, is erected and is based on Hapalodectes. 'Hapalodectes auctus,' described by Matthew and Granger (1925b), is not a mesonychid but a didymaconid. A new subfamily, the Andrewsarchinae, is diagnosed and is based on Andrewsarchus. Several unallocated Asiatic mesonychids are described. Studying the feeding mechanism of mesonychids led to a re-examination of the previous ideas of Boule, Matthew, and others, who maintained that the Mesonychidae had a very weak jaw musculature and that therefore these mammals could not fill a carnivore or scavenger niche. On the basis of the present studies, it seems very probable that mesonychids had a powerful mandibular musculature. The variation of the length/width ratio of homologous lower check teeth of various species of mesonychids might serve as an index to feeding habit. A relatively long lower cheek tooth suggests a carnivorous habit, while a relatively transverse, blunt lower tooth may indicate an omnivorous or scavenging habit. The Mesonychoidea, in agreement with the action of Van Valen (1966), are transferred from the Carnivora to the Condylarthra. No sound phylogenetic conclusions can be offered for the evolution within the Mesonychidae. The known diversity of mesonychids in the late Eocene and early Oligocene of Asia, and our ignorance of the Asiatic Paleocene and early and middle Eocene faunas would badly mar any proposed phylogeny. As a heuristic alternative, the arrangement of the known mesonychid genera to form several adaptive levels may partially clarify mesonychid diversity. In this paper the following five adaptive levels are suggested without implying any phyletic relationship between the various levels: carnivore level, advanced carnivore level, omnivore-carnivore level, omnivore level, bone-crushing level. This study of Asiatic mesonychids revealed a previously unsuspected diversity of genera among the Asiatic forms in comparison to European and North American taxa. The presence of at least 10 genera is ascertained from the poorly known Asiatic strata in comparison to the seven known genera of mesonychids from the relatively well-known early Tertiary of North America and Europe. For a summary of the known worldwide temporal and geographic distribution of the Mesonychidae, see tables 10 and 11"--P. 171.Item Evolution and systematics of Cerion (Mollusca, Pulmonata) on New Providence Island : a radical revision. Bulletin of the AMNH ; v. 182, article 4([New York] : American Museum of Natural History, 1986) Gould, Stephen Jay.; Woodruff, David S."Cerion has been described by its leading student W.J. Clench as 'the most difficult genus of pulmonate mollusks to classify.' No other pulmonate genus shows greater diversity of form; moreover, almost all these divergent morphologies hybridize at their areas of geographic contact. The result is a taxonomic morass that has effectively debarred fruitful biological work on these fascinating snails. The taxonomy of New Providence Island is the most elaborate for the entire genus; more than 90 species of Cerion have been designated, and the distribution of existing names makes no geographic or ecological sense. We use morphometric and genetic techniques to conclude that the living Cerion of New Providence reduce to two semispecies, C. glans (the ribby morphotype) and C gubernatorium (the mottled morphotype). Traces of an extinct C. agassizi line (a prominent taxon of fossil dunes) survive as introgressions into C. gubernatorium populations of southeastern New Providence. These two groups form the basis of Cerion faunas throughout the northern Bahamas; their separation and recognition provide a key to resolving Cerion's taxonomy both here and elsewhere. Ribby and mottled morphotypes are recurrently evolved 'developmental packages,' not homologous taxa from place to place -- thereby illustrating the importance of developmental channeling in parallel evolution. We base our taxonomic decision upon a conciliance among many independent criteria. Geographic distribution: parental morphotypes occupy their expected positions, with narrow hybrid zones at predicted points of transition. Morphology of parental populations: differences between ribby and mottled are not simple consequences of one minor alteration in growth, but summed results of several independent covariance sets. Morphotypes differ consistently in amounts of variation and patterns of covariance. Hybrid populations: we find both enhanced variation and patterns of covariance based on developmental disturbance never before detected in parental populations of Cerion. Genetics: samples grouped by frequencies of electromorphs yield the same clusters of ribby and mottled populations specified by morphology. Morphotypes can be distinguished by allele frequencies, while hybrid populations contain rare alleles found in neither parental taxon. The genetic hybrid zone is wider than the morphological zone and asymmetric about it. An appendix allocates all previously named taxa, and resolves the status of 19 designated fossil taxa, plus a new species (Cerion clenchi), into three successive faunas, marking waves of migration correlated with rise and fall of Pleistocene seas"--P. 391.Item Notes on shell morphology and classification of the Siliquariidae (Gastropoda) : the protoconch and slit of Siliquaria squamata Blainville. American Museum novitates ; no. 2263(New York, N.Y. : American Museum of Natural History, 1966) Gould, Stephen Jay."Siliquaria, described for the first time, is 0.25 mm. wide, helically coiled, and has a sinuous aperture, whereas that of the other two siliquariid genera is 1 mm. wide and planispiral, with a circular aperture. Protoconch form can no longer be used as the chief diagnostic familial characteristic as proposed by Morton (1951). The siliquariid slit is analogous in form, but not in function, to the selenizone of slit-bearing archaeogastropods. Since the siliquariid slit is much longer than that of archaeogastropods, the morphology of slit healing differs. To prevent lateral filling of the slit by growth increments running longitudinally along the slit toward the slit-healing lamina, such increments are either not deposited or else run underneath, rather than in the same surface, as in their predecessors"--P. 11-12.Item Speciation and Punctuated Equilibria: An Alternative to Phyletic Gradualism. [3rd draft](1972) Eldredge, Niles.; Gould, Stephen Jay.Third draft of Eldredge and Gould, 1972.