PEREGRINELLA - AN EARLY CRETACEOUS COLD-SEEP-RESTRICTED BRACHIOPOD

Brachiopods generally have not been considered to be typical or signif icant faunal components of modern or ancient hydrothermal vent and col d-seep settings. The Early Cretaceous (Neocomian) rhynchonellide brach iopod Peregrinella has long been viewed as a paleontological curiosity because of its distinctive morphology, status as the largest Mesozoic brachiopod, anomalous stratigraphic associations, and widespread, yet discontinuous paleogeographic distribution. Examination of all worldw ide Peregrinella occurrences (14) indicates restriction of this brachi opod to ancient cold-seeps. It is probable that Peregrinella grew to l arge sizes in such great abundances at fossil cold-seep sites because of a richly organic food supply generated by localized fluid seepage a nd bacterial chemosynthetic activity. Living brachiopods are not known to harbor chemosymbiotic bacteria in their tissues; however, direct c hemoautotrophic utilization of reduced fluids by Peregrinella cannot b e rejected or demonstrated at present. Peregrinella occurs at widely s eparated cold-seeps of Neocomian age (e.g., California, Mexico, Tibet, Europe), yet its mode of dispersal and larval development is unknown. In modern hydrothermal vents of the deep-sea, organism dispersal occu rs along oceanic ridges, where benthic faunas display both planktotrop hic and nonplanktotrophic larval-mode types. Peregrinella may represen t a Mesozoic relic of a long-lived ''lineage'' of vent-seep associated rhynchonellides from the Paleozoic (e.g., ?Eoperegrinella, Dzieduszyc kia), but major gaps in the stratigraphic record between these rhyncho nellide occurrences, and the lack of rigorous phylogenetic analysis fo r these groups preclude a clear resolution of the origin(s) of vent-se ep brachiopods at present.