Modern Benthic Fauna Originated in the Mesozoic

Ancient Origin of the Modern Deep-Sea Fauna

Authors:

1. Ben Thuy (a,*)
2. Andy S. Gale (b)
3. Andreas Kroh (c)
4. Michal Kucera (d)
5. Lea D. Numberger-Thuy (e)
6. Mike Reich (a,e)
7. Sabine Stöhr (f)

Affiliations:

a. Geoscience Centre, University of Göttingen, Department of Geobiology, Göttingen, Germany

b School of Earth and Environmental Sciences, University of Portsmouth, Portsmouth, United Kingdom

c. Natural History Museum Vienna, Department of Geology and Palaeontology, Vienna, Austria,

d. Marum – Centre for Marine Environmental Sciences, University of Bremen, Bremen, Germany,

e. Geoscience Centre, Museum, Collections and Geopark, University of Göttingen, Göttingen, Germany,

f. Swedish Museum of Natural History, Stockholm, Sweden

Abstract:

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.

Read it. It strongly suggests that the anoxic/hypoxic events had less effect on the extinctions than has been thought before. Or the events as seen in the Cretaceous may not have been as wide spread, I suppose, or the modern fauna were plenty of refugia during those events...