PLoS ONE Reports on the “Ancient Origin of the Modern Deep-Sea Fauna”
|October 11, 2012||Posted by News under News|
An interesting new paper has just been published in PLoS One, describing the discovery of fossilised sea creatures off the coast of Florida, which purportedly shows that modern deep sea creatures (e.g. sea urchins, starfish) may have appeared far earlier than previously believed.
The abstract reports,
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.
Aside from the obvious conflict between the divergence molecular-clock-based estimates and the fossil evidence, what is particularly remarkable is the striking similarity of these ancient creatures to modern deep sea fauna. Indeed, as Science Daily put it,
Previously, researchers believed that these present-day animals evolved in the relatively recent past, following at least two periods of mass extinction caused by changes in their oceanic environment. The new fossil collection described in this study predates the oldest known records of the present-day fauna. “We were amazed to see that a 114 million year old deep-sea assemblage was so strikingly similar to the modern equivalents,” says lead author Ben Thuy. [emphasis added]
Another day; another bad day to be a Darwinian.