TAXONOMIC RE-EXAMINATION OF PERMO-CARBONIFEROUS BRACHIOPODS FROM BOLIVIA: IMPLICATIONS FOR FAUNAL CHANGE DURING THE LATE PALEOZOIC ICE AGE

The Late Carboniferous to Early Permian brachiopod fauna from the Copacabana Formation (northern Bolivia) spans an entire glacial episode during the late Paleozoic ice age, but investigating the effects of glacial-interglacial climate change on the marine communities is difficult because the fauna is poorly understood. Many genera have not been formally described in decades, and little is known about their paleogeographic affinities. New collections were made from the lower Copacabana Formation (Upper Carboniferous) at Ancoraimes and the middle Copacabana Formation (Lower Permian) at Yaurichambi. The brachiopods were then described taxonomically, and using these new taxa assignments faunal counts were conducted. The two localities share many taxa in common, although different taxa were abundant at each site. Kozlowskia, Phricodothyris, Stereochia, and Composita were most common at both localities, but several genera that are uncommon at Ancoraimes, such as Rhipidomella, Reticulariina, and Neochonetes, are very rare at Yaurichambi. Within-sample genus richness decreased, from 8.7 genera per sample in the Late Carboniferous at Ancoraimes to 7.2 genera per sample at Yaurichambi, and several less common taxa do not appear or appear in very low numbers at Yaurichambi. Further, taxa such as Costatumulus, Waagenoconcha, and Hoskingia, typical of cooler climates in Gondwana, increased in numbers across the interval, implying decreasing water temperatures and diversity in subtropical marine environments during the Late Carboniferous onset of the late Paleozoic ice age.