Abstract

Understanding the response of a species or lineage to long-term environmental change is a critical aspect of evolutionary paleoecology. In order to do this, paleobiologists must have an excellent fossil record of a lineage and an independent source of environmental data in the same region. This situation occurs in the San Pedro area of southern California, where relatively new paleotemperature and paleoproductivity records enhance the well-known fossil gastropod record. We quantified shell morphology of late Pleistocene and Recent turritellid gastropods from this area and compared the timing of changes with temperature and productivity reconstructions for the region. Our results indicate that warm temperatures and moderate to high productivity are associated with larger shells and wider whorls. Cold temperatures and lower productivity are associated with smaller, narrower shells. We propose that warm temperatures and moderate productivity result in higher growth rates in turritellid gastropods. Our work also suggests that below a certain threshold temperature, productivity appears to have no influence on shell morphology. In other words, growth rate is unaffected by high productivity unless average temperatures are above a certain level. These results are consistent with models of shell deposition and with experimental results from living gastropods and bivalves reported in the literature.

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