With Fossil Friday falling on Christmas, I would have liked to post a picture of a fossil reindeer (Rangifer tarandus). But most of the vertebrate fossils at Western Science Center are from Riverside County, and while reindeer (or caribou, as they’re called in North America) did make it as far south as Georgia during the Ice Age they apparently never made it to southern California. So instead I’ve gone with the closest relative to reindeer in our collection.
Rangifer is a member of the family Cervidae, the deer. A unique and highly visible feature of cervids is the presence of antlers in males in almost all extant species (a few species don’t grow antlers, and in reindeer the females also grow them).
Shown above is the base of an antler from the Early Pleistocene deposits in San Timoteo Canyon, found during the Southern California Edison El Casco Substation project. This is the left antler seen in lateral view, with anterior to the left. The bone at the base is a fragment of the frontal, which makes up part of the braincase. The cylindrical shaft angling back from the frontal is called the pedicle, while the rugose portion at the tip is the coronet. Here’s a medial view of the same fragment:
Antlers are unique in that, even though they are made of bone, they are shed and regrown periodically, usually every year. The pedicle is the only permanent part of the antler. In contrast, other mammals with comparable head gear, such as bovids (cattle and antelopes), have horns that consist of a bony core covered with a keratin sheath and that are never shed (pronghorns shed the keratin sheath but not the bony core).
(As an aside, antler growth is initiated by hormones stimulating specialized connective tissue that covers the pedicle. In researching this blog post, I was surprised to find that injuries to the skin in other parts of the head can result in antler growth at the sites of the injuries, so that occasionally a deer will grow extra antlers (Bubenik and Hundertmark 2002)!)
When I first looked at this specimen, I was struck by its size; it’s much larger than the white-tailed deer (Odocoileus virginianus) I frequently saw back east. I briefly wondered if it might be from an elk (Cervus elaphus), another species that, like reindeer, apparently never made it to southern California. We happen to have a modern elk in the WSC collection, and a quick comparison showed that, large as it is, our fossil specimen is much smaller than a mature elk:
This specimen is probably close to the upper end of the size range for a mule deer, Odocoileus hemionus, which does live in southern California. There may also be extinct species of Odocoileus from the Early Pleistocene that are possibilities, but with only an antler fragment it may not be possible to make a definite identification of this specimen beyond the family or genus.