Dissecting Lithiotis Bivalves Implications for the Early Jurassic Reef Eclipse英文电子书.pdf

RESEARCH REPORT 51 Dissecting ‘‘Lithiotis’’ Bivalves: Implications for the Early Jurassic Reef Eclipse NICOLE M. FRASER,* DAVID J. BOTTJER, and ALFRED G. FISCHER Department of Earth Sciences, University of Southern California, Los Angeles, CA, 90089-0740, E-mail: N.Fraser@nhm.ac.uk PALAIOS, 2004, V. 19, p. 51–67 other marine ecosystems, yet are more vulnerable to glob- al biogeochemical events. Reefs are often the first ecosys- Following extensive Late Triassic coral-constructed reefs tems decimated in biotic crises and often the last to return and the aftermath of the Triassic–Jurassic mass extinction, (Droser et al., 1997). One of the most striking effects of the Early Jurassic buildups are rare and constructed primari- end-Triassic mass extinction was the total loss of reef eco- ly by bivalves. The Pliensbachian exhibits a radiation of ab- systems that had flourished, notably in the Northern Cal- errant pterioid bivalves, the ‘‘Lithiotis’’ bivalves, which in- careous Alps and elsewhere, until the end of the period. clude: Lithiotis problematica, Cochlearites loppianus, Ger- The Early Jurassic, or Lias, represents a slow but steady villeioperna sp., Mytiloperna sp., and Lithioperna scutata. paleogeographic change due to the reconfiguration of the These large bivalves are ubiquitous in shallow, nearshore continents with the rifting of Pangaea (Nance and Mur- tropical waters and restricted to the Early Jurassic recovery phy, 1994). The Early Jurassic is also punctuated by a sig- interval. Fie