查看更多>>摘要：Two new species of deep-sea stalked crinoids belonging to the family Hyocrinidae were collected in the northeastern Pacific. The descriptions contain detailed information on character variations and ontogeny. The five specimens of Gephyrocrinus messingi n. sp. lived at depths ranging from 1,777 m to 2,110 m off British Columbia and California. This new species is the first record of the genus Gephyrocrinus in the Pacific Ocean, which was previously known from only a single species, G. grimaldii, fromthe northeastern Atlantic at the same depth range. The two species illustrate opposing pheno-types within the same genus. Fifty-eight specimens of the second new species, Ptilocrinus clarki n. sp., were dredged off British Columbia close to the type-locality of P. pinnatus, the type species of the genus Ptilocrinus, but at shallower depths ranging from 1,178 to 1,986 m. This exceptional collection provides significant data on intraspecific variation in the main morphological characters, especially armpattern. The ontogeny of stalk articulations and the main traits of adoral plate differentiation are described in detail. A complementary investigation on P. pinnatus was conducted using specimens collected by the "Albatross" expedition at a depth of2,906 m. Despite similarities in external morphology, tegmen and cover plates, the two ptilocrinid species display significant differences in pinnule architecture, aboral cup and stalk articulations. From comparison with Gephyrocrinus messingi n. sp. and Ptilocrinus clarki n. sp., G. grimaldii and P. pinnatus are interpreted as the result of heterochronic development by paedomorphy after ecological or geographic isolation. Pinnule architecture in the two new species suggests first steps in an evolutionary trend toward a rigid box which protects gonad inflation in the proximal part of the pinnule. These new data on Ptilocrinus and Gephyrocrinus create problems in the current taxonomy of the family Hyocrinidae. The main derived characters, especially in pinnule and arm pattern, are used to propose new hypotheses for hyocrinid phylogeny.
查看更多>>摘要：Africorchestia, a new genus of coastal sand-hoppers (Amphipoda, Talitridae), is described from western Africa and southwestern Europe. Africorchestia includes five species: A.fischeri (H. Milne Edwards, 1830); A. quadrispinosa (KM. Barnard, 1916); A.skoogi (Stebbing, 1922); A. spinifera (Mateus, 1962); and A. tricornuta (Shoemaker, 1920). Along the west coast of Africa and the south-western coast of Europe there is a group of striking sand-hoppers with sculptured pleosomes and setae on the dactyli of pereopods 6 and 7. Although known since H. Milne Edwards (1830) first described Orchestia fischeri, they have never been incorporated into a distinct genus. In this paper we describe the genus, Africorchestia gen. nov. and include five species, Orchestia fischeri H. Milne Edwards, 1830, Talorchestia quadrispinosa K.H. Barnard, 1916, Talorchestia skoogi Stebbing, 1922, Talorchestia spinifera (Mateus, 1962) and Talorchestia tricornuta Shoemaker, 1920. Although males are known for all species females have only been described for A. skoogi and A. spinifera. Consequently sexual dimorphism is incompletely known for the genus.
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