Ancient origin of the modern deep-sea fauna.
The origin and possible antiquity of the spectacularly diverse modern deep-sea fauna has been debated since the beginning of deep-sea research in the mid-nineteenth century. Recent hypotheses, based on biogeographic patterns and molecular clock estimates, support a latest Mesozoic or early Cenozoic date for the origin of key groups of the present deep-sea fauna (echinoids, octopods). This relatively young age is consistent with hypotheses that argue for extensive extinction during Jurassic and Cretaceous Oceanic Anoxic Events (OAEs) and the mid-Cenozoic cooling of deep-water masses, implying repeated re-colonization by immigration of taxa from shallow-water habitats. Here we report on a well-preserved echinoderm assemblage from deep-sea (1000-1500 m paleodepth) sediments of the NE-Atlantic of Early Cretaceous age (114 Ma). The assemblage is strikingly similar to that of extant bathyal echinoderm communities in composition, including families and genera found exclusively in modern deep-sea habitats. A number of taxa found in the assemblage have no fossil record at shelf depths postdating the assemblage, which precludes the possibility of deep-sea recolonization from shallow habitats following episodic extinction at least for those groups. Our discovery provides the first key fossil evidence that a significant part of the modern deep-sea fauna is considerably older than previously assumed. As a consequence, most major paleoceanographic events had far less impact on the diversity of deep-sea faunas than has been implied. It also suggests that deep-sea biota are more resilient to extinction events than shallow-water forms, and that the unusual deep-sea environment, indeed, provides evolutionary stability which is very rarely punctuated on macroevolutionary time scales.
Geoscience Centre, University of Göttingen, Department of Geobiology, Göttingen, Germany. nebyuht@yahoo.com
Ben
B
Thuy
Andy S
AS
Gale
Andreas
A
Kroh
Michal
M
Kucera
Lea D
LD
Numberger-Thuy
Mike
M
Reich
Sabine
S
Stöhr
D000818:Animals; D044822:Biodiversity; D005075:Biological Evolution; D004447:Echinodermata / Q000145:classification / Q000254:growth & development*; D005580:Fossils; D005843:Geography; D008386:Marine Biology / Q000379:methods; D009792:Oceans and Seas; D010163:Paleontology / Q000379:methods