Added Morphological Characteristics of Muscle Scars, Maxillula and Mandible of Two Ostracod Genera Loxoconcha (Loxoconchidae) and Xestoleberis (Xestoleberididae)

Abstract

Total 23 species of the genus Loxoconcha and 21 species of the genus Xestoleberis were presented in this study. The results show that most species of the genus Loxoconcha consist of four adductor scars to arrange in a curved sub-vertical row and concave anteriorly, except L. pulchra carrying five, in which the top one is divided into two. The frontal scars with C-shape, opening anteriorly are presented in most of Loxoconcha species, however, the frontal scar with bean-shape or oval-shape is discovered in five species of L. japonica group. Most of L. kosugii bear the frontal scar with C-shape, but the frontal scar with Y-shape is found in several individuals. This phenemenon shows the close phylogeny between the genus Loxoconcha and Palmoconcha. About the genus Xestoleberis, chaetotaxy of setae on most appendages is a typical character of this genus, except for setae of exopodite on the maxillula. The published fossil records and the tendencies of change in the number of setae on the maxillula and mandible among three phylogenetic groups suggest that Group A or B is an ancestor of the genus Xestoleberis, and Group C is a derived group.