Myodocope ostracods from the Silurian of Australia

摘要

The Silurian of Australia contains at least three genera (one new, Canalarta gen. nov.) and three species (two new, Canalarta papata sp. nov. and Bolbozoe beccata sp. nov.) of myodocope ostracods. These fossils were recovered from clastic sedimentary deposits in the lower Silurian (probably Homerian) Walker Volcanics unit of New South Wales that may represent mudflow deposits. In having the youngest occurrence of Entomozoe aff. tuberosa and the oldest known Bolbozoe species, the Australian myodocopes represent a chronologically intermediate assemblage between previously known early and late Silurian myodocope faunas. Several fossil groups from the Silurian of Australia, such as ostracods, trilobites, brachiopods and corals, apparently have a cosmopolitan distribution at generic level. The presence of many continental and micro-continental landmasses that existed along and within the tropical pan-Tethyan seaway, together with the prevailing ocean circulation, could explain this distributional pattern. The depositional setting, sedimentary deposits and faunal associates do not provide conclusive evidence concerning the lifestyle of the Australian myodocopes. They could represent nektobenthic species, as has been suggested for other early to mid Silurian myodocopes, or hyperbenthic/ pelagic species, as was proposed for known late Silurian forms.