New early Miocene species of the cheilostome bryozoan Microporella from the South Island of New Zealand

Since its first appearance in the early Miocene, the cheilostome bryozoan genus Microporella has been cosmopolitan, recorded from most continents. However, Miocene Microporella records in New Zealand are scarce, and currently limited to a single middle Miocene species identified as Microporella hyadesi (a Recent bifoliate erect form originally described from Cape Horn and Tierra del Fuego) from the Mt. Brown 'E' Limestone Formation of North Canterbury. Here, we describe and illustrate three new early Miocene (Otaian-Altonian New Zealand stages corresponding to the Aquitanian-Burdigalian) species, namely Microporella incurvata sp. nov., M. gladirostra sp. nov. and M. whiterocki sp. nov., that represent the geologically oldest regional examples of the genus to date. A fourth species is left in open nomenclature because complete ovicells are not preserved in the only recovered specimen. The colonies of Microporella were collected from several rock formations exposed in limestone quarries on the South Island. The three new species share ovicells with a personate structure, but differ in the appearance of the ooecial surface (evenly pseudoporous versus imperforate), shape of the ascopore opening (cribrate versus non-cribrate), number of oral spine bases, and shape of the avicularian rostrum and crossbar. We also illustrate for the first time ovicells of another fossil species, Microporella rusti, from the Pleistocene Nukumaru Limestone Formation of the Wanganui Basin on the North Island. The ovicells of this taxon are rare, being found in only six of several hundred specimens collected to date. The ovicells of M. rusti are also very large, covering the entire orifice of the maternal zooid, similar to those of some other Microporella species all characterized by erect bifoliate colonies contrasting with the encrusting colonies of M. rusti.