Permian Gastropoda of the southwestern United States. 2, Pleurotomariacea : Portlockiellidae, Phymatopleuridae, and Eotomariidae. Bulletin of the AMNH ; v. 114, article 2
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Date
1958
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New York : [American Museum of Natural History]
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Abstract
"The development of a mass etching program for the recovery of silicified fossils from Permian limestone of west Texas has resulted in the accumulation of a large number of fossil gastropods and has made possible the present systematic study of the pleurotomarian gastropods. Most of the collections used herein were made by, or under the direction of, G. Arthur Cooper, Norman D. Newell, and J. Brookes Knight. These collections were obtained from the Wolfcamp, Leonard, and Word formations of the Glass Mountains of Texas and from the Hueco, Bone Spring, and Cherry Canyon formations of the Sierra Diablo and Guadalupe Mountain region. Comments on stratigraphy are made for the orientation of the reader. Little original stratigraphic work has been done, except to verify or corroborate correlations based on other fossil groups. A few of the paleoecological relationships are discussed, with particular emphasis on molluscan assemblages in the Glass Mountains. An instance is cited of a relationship between a Heliospongia and Glyptotomaria (Glyptotomaria) marginata. Statistical methods used include those based on univariate analysis and on allometric growth line comparisons. This latter type of analysis is based on the relative growth line, as estimated by the reduced major axis. Discrimination was based, in part, on a comparison of slope and position differences of the relative growth line between samples. Studies of the logarithmic spiral show that it can be useful in the study of pleurotomarians and may be treated statistically. The value of the logarithmic spiral formula as a discriminatory character must be weighed against the time and labor required in its derivation. Gross measurements of the spiral, such as the use of suture ratios, tend to reduce expenditure of time, but they also reduce accuracy. Some of the directional and non-directional variations within species and genera are noted. This study attempts to show some aspects of pleurotomarian speciation during the Permian. These are particularly well illustrated in the genus Tapinotomaria. Studies of population structure made it possible to understand some of the changes thought to be responsible for most speciation in the families studied. Emphasis is placed on ontogenetic growth characters. The bulk of this paper is devoted to an analysis and description of the rich and heretofore unknown Permian pleurotomarian faunules. The general increase in knowledge about Permian representatives of the superfamily Pleurotomariacea is briefly discussed. Two families, Portlockiellidae and Phymatopleuridae, are diagnosed and discussed. The family Eotomariidae Wenz, 1938, is redefined and expanded. Thirteen genera are discussed herein: Lamellospira and Lacunospira are new; Eirlysia, Tapinotomaria, Discotomaria, Callitomaria, and Shwedagonia are discussed for the first time (see Batten, 1956). Tapinotomaria and Shwedagonia have been discussed at some length because of their interesting evolutionary developments. Five previously described genera are also included, Euconospira, Spiroscala, and Glyptotomaria are redefined; Phymatopleura and Paragoniozona are discussed. A total of 32 species are included, 28 of which are new and named"--P. 159.
Description
p. 157-246, [11] p. of plates : ill. ; 27 cm.
Thesis (Ph. D.)--Columbia Univeristy.
Includes bibliographical references (p. 245-246).
Thesis (Ph. D.)--Columbia Univeristy.
Includes bibliographical references (p. 245-246).
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