Sudden and Gradual Molluscan Extinctions in the Latest Cretaceous of Western European Tethys

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Based on graphic correlation of the major lithological boundaries.

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The absence of ammonites in the marls of Member V is unlikely to be due to preservation failure, given that ammonites are found in the similar marls of Member III, which occurs lower in the section.

Ammonite fossils have been found, on average, once every 18 m² of outcrop in the top 1.3 m of the Cretaceous at Hendaye, France. Echinoids are recovered at a comparable rate of one specimen per 19 m² of outcrop. At least one echinoid per collecting season, but no ammonites over seven seasons, has been recovered in about 50 m² of outcrop excavated within the pre-K-T gap (1.3 to 3.0 m below the K-T boundary). At these recovery rates, the probability that ammonites were as abundant in the excavated interval as they were above the pre-K-T gap is only 0.06; however, the probability that the ammonites were a third as abundant in the excavated interval as they were above the pre-K-T gap is 0.39.

We thank A. Smith, M. Foote, D. Jablonski, D. Jacobs, B. Runnegar, and two anonymous reviewers for their comments. Supported by NSF grant EAR-9258045 to C.R.M. and by EAR-8904797 and EAR-8843926 to P.D.W.