Holocene thecideide brachiopods from the north-western Pacific Ocean: systematics, life habits and ontogeny

摘要

A new species of the lacazelline brachiopod genus Ospreyella is described from shallow cryptic habitats in Palau, western Caroline Islands and Arnd Atoll, Pohnpei, eastern Caroline Islands, north-western Pacific Ocean. This new taxon, here named Ospreyella palauensis, and representing the third discovery of a species of Ospreyella from the Indo-Pacific region, is compared with the other two recently described extant species of the genus, O. depressa Luter from the Great Barrier Reef, Australia, and O. maldiviana Logan from the Maldive Islands, northern Indian Ocean. An ontogenetic sequence is described for the new species and compared with those previously described for other Holocene lacazellines. Additionally, a study of ontogenetic stages in Thecidellina congregata from Saipan in the Northern Mariana Islands shows early-stage similarities to those of the new species and other lacazellines. These observations on development in extant forms provide important analogies for comparison with ontogenetic stages in ancestral fossil forms and information which may be useful in reconstructing thecideide phylogenetic history.