Ocular shell structures in some loxoconchid Ostracoda

Ocular structures are poorly known in some podocopid ostracodes, including the Family Loxoconchidae, Sars 1925, although the features are useful in taxonomy and seem to have potential in paleoenvironmental reconstruction. Here, 10 species of Loxoconcha and Loxocorniculum were studied with polished and thin sections, internal molds, and light and scanning electron microscopy. The ocular sinus may be well developed even in species that have indistinct external ocular structures. In general, the ocular sinus in adults of these loxoconchids is low, relatively wide, unstalked, and has a subcentral concavity and a distinct rim. In Loxoconcha, depending upon the species, either the anterior or posterior distal part of the sinus may be the higher, while in Loxocorniculum the anterior portion is higher. The sinuses in both genera are unlike the elongate, stalked, and distally bulbous structure in the trachyleberids. The ocular sinus in each species is diagnostic, thereby providing another character for taxonomic studies. Ocular structures also may provide a means of estimating paleodepths.