Title: The systematics of sympatric species in West Indian spatangoids
Description: "Analysis of the echinoid genera Brissopsis, Plethotaenia and Paleopneustes indicates that each genus has two species which live sympatrically in the West Indian area. Each species is described and illustrated. The following species and sub-species of the genus Brissopsis are recognized in the Atlantic Ocean: B. alta, B. atlantica, B. elongata, B. elongata jarlii, B. mediterranea, B. lyrifera, b. lyrifera capensis, and B. evanescens. Ther are two species of the genus Pleithotaenia: P. angularis n.sp. and P. spatangoides (A. Agassiz, 1883). These species are described and the genus placed in the family Spatangidae on the basis of numerous characters. Two species of Paleopneustes are described: P. cristatus A. Agassiz, 1873 and P. tholoformis n. sp. Paleopneustes is shown to be closely related to Plesiozonus, Pericosmus, and Faorina. These four genera are united as a revised family, the Paleopneustidae.^

The genera remaining in Mortensen's (1950) concept of the Paleopneustidae are placed in the Asterostomatidae as suggested by Fischer (1966). A new species of Saviniaster, S. enodatus n. sp., is described from deep water south of Grand Bahama, B.W.I. The genus was previously known by one species from the Eocene deposits of France. Where possible, allometric, individual, and geographic variation are compared for each of the species. The characters of the test are shown to be relatively stable and do not vary greatly with changes in habitat or geographic distance. Inhibitor genes which prevent expression of fascioles and pedicellariae are discussed. The value of the fascioles as a taxonomic character is discussed, and the path of fascioles over the plates is show to be a useful taxonomics feature. Sympatric species-pairs are common in spatangoids of other parts of the world and from the fossil record.^

The differences between the members of each species-pair are surprisingly constant in the various genera. The possibility that the paired forms are a non-sex-linked polymorphism is rejected in favor of their representing distinct species. A system of measurements is developed which statistically represents the external morphology of a spatangoid. This system is intended to promote standardization of measuring spatangoids for investigation of their taxonomy, zoogeography and speciation"--Page 1.
Subjects: Sea urchins
Places: West Indies