Wednesday, December 15, 2010
Fossil of the Week
12/15/10 – The Hind Legs of a Whale
The 44-foot-long skeleton of a modern North Atlantic Right Whale (Eubalaena glacialis) hangs in the atrium above the Museum of the Earth’s Borg Warner Gallery, fully visible from the lobby and from outside the building through its surrounding glass windows. It is an iconic specimen, salvaged for the Museum by PRI staff when the whale washed ashore in late 1999 at Cape May, New Jersey.
Some of the most fascinating features of a whale are those clearly linking it as a mammal to its terrestrial ancestors. Perhaps the best example in this category is the vestigial pelvis and hind limbs. Shown here is the left pelvic bone, with the thick thigh bone or femur at the center in the photograph. According to PRI’s director Warren Allmon in his book A Leviathan of our Own: the Tragic and Amazing Story of North Atlantic Right Whale #2030 (Paleontological Research Institution, © 2004):
“The pelvis of a whale is an inherently fascinating structure because it is so clearly a vestige of evolutionary history, retained from the distant past when the whale’s ancestors had four legs and walked on dry land. Although fossils have been found that show that early whales did have external hind limbs, modern whales normally lack any such appendages, except as unusual “freak” occurrences. The “pelvic” bones of modern whales (which actually often include vestiges of the femur or thigh bone, and even the shin bone or tibia, as well as the pelvis or hips) are normally buried inside the flesh of the body, underneath the base of the tail. Although these bones are the site of attachment of several sets of muscles … they are clearly much reduced from their former size and function…”
“Almost everything we know about the pelvic bones of right whales is derived from the work of John Struthers M.D., who in 1880 published results of detailed dissections of at least 10 animals. The pelvic bones of #2030* consist of two bones, one from each side of the animal. Comparing these bones to the illustrations of Struthers … indicates that they represent the pelvic or hip bones and the femur, all fused together. Struthers’ work indicates that right whales are variable in the form of their pelvic bones; some are completely fused while others have the femur, and even the tibia, present as separate bones.”
Right Whale #2030 provides a striking visual display at the Museum of the Earth. It also illustrates two major themes of the Museum – evolution and conservation – in one unforgettable specimen.
*The number 2030 was assigned to this female right whale in Massachusetts Bay in June 1990 by the National Marine Fisheries Service. Subsequent sightings included the Bay of Fundy in 1994-1997 as well as several sightings off the southeastern U.S. in 1996. She became entangled in fishing gear in May 1999 and despite attempts to free her, she died off the New Jersey coast in October 1999.
Text by Paula Mikkelsen