Brachiopods from the extreme South Pacific and adjacent waters

Abstract

Sixteen genera and 27 species of Recent brachiopods are reported from the far southern Pacific Ocean and adjacent parts of the South Atlantic and southern Indian Ocean. These specimens extend the known geographic ranges of at least 10 species and the known bathymetric ranges of at least seven species. The new material gives greater support to the idea that many Recent brachiopod species have a wide geographic range and calls into question the very limited geographic ranges of many species known only from the fossil record. Puncta density appears to be a useful character for distinguishing Neothyris compressa and N. lenticularis. At least nine different types of geographic distribution are represented among the species studied for this paper. Areas of moderate depth on seamounts, particularly along oceanic ridges and on oceanic rises, may form important geographic areas of distribution, avenues of dispersal, and barriers to brachiopods. Four examples of polytypic species are cited. The new specimens lend additional support to the notion that one polytypic species of Liothyrella extends, with clinal morphological changes, from southernmost South America to Antarctica. Students of modern brachiopods are urged to consider large-scale geographic variation within species and not to hide it with finely delimited taxa. This approach has the potential to lead, in both modern and ancient brachiopods, to a taxonomy with fewer and more meaningful species and genera. Progenetic changes seem to be a common adaptive strategy in brachiopods on largely soft substrates and in deep water. The progenesis may be short term within a single species or long term involving evolution of new species and genera.