「バイカル湖学」入門[1 1 ] 底生生物グリゴーリー·イヴアノヴィチ·ガラジー

摘要

This paper has two objections: (1) to show the brief outlines of benthic animals and plants of Lake Baikal, and, (2) to present the results from a comprehensive survey of the large collection of fossil branchiopods and a study on the allied species of the Recent Spinicaudata. The status of the Recent clam shrimp family Baikalolkhoniidae from Lake Baikal is re-examined, and a new species, distinct from its allied species Baikalolkhonia tatianae Naganawa, 1999, is described. As the fossil evidence of these early clam shrimps is so poor, one cannot say where this family should be placed on the evolutionary tree. The Paleo-Mesozoic clam shrimp families Lioestheriidae, Estheriellidae, or Leaiadidae could have been an early forerunner of this family, but to what group of modern clam shrimps it is related is impossible to say. The finding of this new species surely holds the key to the solution of the taxonomic question, because its radial ornaments on the carapace indicate an intermediate form, which bridges the gap between extinct and existing spinicaudatan families.