End Triassic Bivalve Extinction: Lombardian Alps, Italy

Christopher A. McRoberts, Cathryn R. Newton, Andrea Allasinaz

Research output: Research - peer-reviewArticle

  • 21 Citations

Abstract

A major biotic crisis affecting virtually all major marine invertebrate clades occurred at the close of the Triassic. Species-level data on bivalves from the Lombardian Alps of Italy record the extinction and suggest a possible causal mechanism. A significant decline in species richness is observed during the lower Rhaetian, where 51% of bivalve species, equally distributed among infaunal and epifaunal filter-feeders, went extinct. The taxonomic loss at the middle Rhaetian was more severe, where 71% of the bivalve species were eliminated, including all infaunal and 50% of the epifaunal species. The data indicate that the extinction selectively eliminated infaunal bivalves. An initial loss of bivalve species richness during the middle and upper Rhaetian correlates with changes in sedimentary facies related to a fall in relative sea level. This sea level fall is marked by the onset of peritidal micrites and shifting ooid shoals which may have rendered substrates unsuitable for both epifaunal and infaunal bivalves. The possible influences of temperature and salinity fluctuations are difficult to assess, but they may also have had a deleterious effect on the local bivalve fauna. The loss due to peritidal conditions is not consistent with the selective survivorship of epifaunal taxa recurring in overlying Jurassic rocks. We propose that physiologic differences and selective resistance to physical stress are consistent with the pattern of selective extinction. Facies shifts associated with the marine regression are not sufficient to account for the extremely high magnitude of infaunal extinction. This selection against infaunal bivalves is probably caused by their decreased capacity to filter feed relative to their metabolic demands. A decrease in primary productivity could have selectively eliminated the infauna. Oceanographic processes or atmospheric darkening, perhaps caused by an extraterrestrial impact, could drastically limit food resources (primary productivity) and is consistent with the selective extinction at the end of the Triassic.

LanguageEnglish (US)
Pages297-317
Number of pages21
JournalHistorical Biology
Volume9
Issue number4
DOIs
StatePublished - Mar 1 1995

Fingerprint

Alps region
Bivalvia
extinction
Italy
sea level
primary productivity
species diversity
Oceans and Seas
survival rate
rocks
invertebrates
fauna
salinity
temperature
Salinity
Invertebrates
Food
Temperature

Keywords

  • Bivalvia
  • extinction
  • Italy
  • Jurassic
  • palaeoecology
  • Triassic

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)

Cite this

End Triassic Bivalve Extinction : Lombardian Alps, Italy. / McRoberts, Christopher A.; Newton, Cathryn R.; Allasinaz, Andrea.

In: Historical Biology, Vol. 9, No. 4, 01.03.1995, p. 297-317.

Research output: Research - peer-reviewArticle

McRoberts CA, Newton CR, Allasinaz A. End Triassic Bivalve Extinction: Lombardian Alps, Italy. Historical Biology. 1995 Mar 1;9(4):297-317. Available from, DOI: 10.1080/10292389509380505
McRoberts, Christopher A. ; Newton, Cathryn R. ; Allasinaz, Andrea. / End Triassic Bivalve Extinction : Lombardian Alps, Italy. In: Historical Biology. 1995 ; Vol. 9, No. 4. pp. 297-317
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