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Worldwide distribution of the modiomorphid bivalve genus Caspiconcha in late Mesozoic hydrocarbon seeps

100%

Jenkins R. G., Kaim A., Little C. T. S., Iba Y., Tanabe K., Campbell K. A.

Acta Palaeontologica Polonica

2013

tom 58

nr 2

Exceptionally well preserved specimens of the bivalve mollusc Modiola major were collected from a Lower Cretaceous (Barremian) hydrocarbon seep deposit in northern California. This material, together with the type series of M. major, and various other specimens from Upper Jurassic to Lower Cretaceous seep localities in California, is redescribed and referred to the hydrocarbon seep−restricted modiomorphid genus Caspiconcha. We include also a description of Myoconcha americana because some previous reports have incorrectly synonymized Myoconcha americana with Caspiconcha major. In addition, we report Caspiconcha sp. from a Lower Cretaceous (Albian) hydrocarbon seep from Hokkaido, Japan, and we review all currently described species of Caspiconcha, and other species that probably belong to this genus. We demonstrate that Caspiconcha had a widespread distribution in Late Jurassic to Early Cretaceous hydrocarbon seeps, but became rare thereafter, with the last representative occurring in Upper Cretaceous strata of Japan. This macroevolutionary pattern is similar to that observed in the seep−restricted brachiopods. After the decline of Caspiconcha at the end of the Early Cretaceous and its last occurrence in the Campanian, the ecological niche of epifaunal to semi−infaunal seep endemic bivalves was largely vacant and not reoccupied until the Eocene with the appearance of the vesicomyid and bathymodiolin bivalves. The formal placement of M. major into the genus Caspiconcha restricts the fossil record of mytilids at seeps to post−Mesozoic times, and thus there is less discrepancy between the fossil record of chemosynthetic mytilids and their divergence age estimates from molecular data.

Chaetopterid tubes from vent and seep sites: Implications for fossil record and evolutionary history of vent and seep annelids

88%

Kiel S., Dando P. R.

Acta Palaeontologica Polonica

2009

tom 54

nr 3

443-448

Vestimentiferan tube worms living at deep−sea hydrothermal vents and cold seeps have been considered as a clade with a long and continuing evolutionary history in these ecosystems. Whereas the fossil record appears to support this view, molecular age estimates do not. The two main features that are used to identify vestimentiferan tubes in the fossil record are longitudinal ridges on the tube’s surface and a tube wall constructed of multiple layers. It is shown here that chaetopterid tubes from modern vents and seeps—as well as a number of fossil tubes from shallow−water environments—also show these two features. This calls for a more cautious interpretation of tubular fossils from ancient vent and seep deposits. We suggest that: current estimates for a relatively young evolutionary age based on molecular clock methods may be more reliable than the inferences of ancient “vestimentiferans” based on putative fossils of these worms; not all of these putative fossils actually belong to this group; and that tubes from fossil seeps should be investigated for chitinous remains to substantiate claims of their potential siboglinid affinities.

Ograniczanie wyników

2 Acta Palaeontologica Polonica

1 Campbell K. A.

1 Dando P. R.

1 Iba Y.

1 Jenkins R. G.

1 Kaim A.

1 Kiel S.

1 Little C. T. S.

1 Tanabe K.

1 2013

1 2009

Wyniki wyszukiwania

Worldwide distribution of the modiomorphid bivalve genus Caspiconcha in late Mesozoic hydrocarbon seeps

Chaetopterid tubes from vent and seep sites: Implications for fossil record and evolutionary history of vent and seep annelids