After 121 years, identification of 'grave robber' fossil solves a paleontological enigma

8:59:00 PM, Sunday, December 16, 2012

(Phys.org November 19, 2012) "An international team of researchers, including Carnegie Museum of Natural History scientist John Wible, has resolved the evolutionary relationships of Necrolestes patagonensis, whose name translates into "grave robber," referring to its burrowing and underground lifestyle. This much-debated fossil mammal from South America has been a paleontological riddle for more than 100 years.

Scientific perseverance, a recent fossil discovery, and comparative anatomical analysis helped researchers to correctly place the strange 16-million-year-old Necrolestes, with its upturned snout and large limbs for digging, in the mammal evolutionary tree. This finding unexpectedly moves forward the endpoint for the fossil's evolutionary lineage by 45 million years, showing that this family of mammals survived the extinction event that marked the end of the Age of Dinosaurs. This is an example of the Lazarus effect, in which a group of organisms is found to have survived far longer than originally thought. Situating Necrolestes among its relatives in the fossil record answers one long-held question, but creates others; it reminds us that there is a lot we don't yet know about the global impacts of the massive extinction event 65 million years ago and it challenges assumptions that the well-documented effects that occurred in western North America were experienced globally.

The scientific paper resolving the mystery of Necrolestes appears today in Proceedings of the National Academy of Sciences.

A paleontological riddle Since its discovery in Patagonia in 1891, Necrolestes has been an enigma. "Necrolestes is one of those animals in the textbooks that would appear with a picture and a footnote, and the footnote would say 'we don't know what it is,'" says co-author John Wible, Carnegie Museum of Natural History mammalogist and member of the discovery team that also includes researchers from Australia and Argentina. Wible is known for his work on the origins and evolutionary relationships among the three modern mammal groups: placentals (live-bearing mammals such as humans), marsupials (pouched mammals such as opossums), and egg-laying mammals (such as platypuses)..."

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