A Pleistocene Ecosystem
by Wesley Gordon
page 16


Three Lower Jaws in One

On a Saturday three years later, the boys, now organized as a fossil-hunting group, were again digging in fine sand at Locality V3604 at a second site rich with Tetrameryx specimens. Labeled T2, this site was about 1500 feet south of the original site, T1. (The boys gave exceptionally rich pockets special identifications. Such information would be useful to scientists should they wish to plot the exact places where the fossils were discovered.)

Camelops jaw T-2

One this Saturday much excitement was created by a team member who was digging out the lower jaw of a horse. “Two jaws, one on top of the other!” he called out. Under the horse jaws was the left lower jaw of Tetrameryx irvingtonensis, with the six back (or grinding) teeth intact. The boys wondered how the jaws of two such different plant-eaters could have been buried together. Did the animals fall victim to a  band of wolves, or did a sabercat get one and wolves the other? Perhaps they perished at a dried-up watering hole. This happens to animals in drought in Africa and Australia.

The speculations continued: “What about this idea?” asked one. “They may have died in a different place. Let’s suppose that one of them died upstream and was buried during winter floods. Later a big rain could have washed it down during winter floods. Later a big rain could have washed it down here where it just happened to settle on top of the other.”

Another boy disagreed. “If that had happened,” he commented, “the teeth would have been broken or eroded.”

Soon more complicated problems arose. Under the two jaws was the left lower jaw of a camel. One boy was positive that the cause of death must have been an extended drought. He visualized vultures picking flesh from many carcasses and rains washing the bones into a deep pool. “Don’t bring vultures into this,” one boy inside. “We haven’t found evidence of vultures at Irvington.”

“But proof that they weren’t here hasn’t been found, either,” stated another member of the group.

The director asked, “Couldn’t these three herbivore have died of a sickness, such as the hoof-and-mouth disease?” The group agreed that this was another possibility. With a smile, a boy suggested that the animals were standing under an oak tree when a bolt of lightning shattered the tree and killed them.

“Yes,” continued someone else, “a pack of wolves came along and had their first meal of ‘cooked’ meat. The wolves became so excited that they dragged the bodies of the camel, horse, and antelope all over the place, until they happened to reach the big pool. There they finished picking off the cooked meat and left the bones, Then came a big rain that washed the bones into the water.”

What do you think? The following information may help you to evaluate the suggestion that vultures picked the bones of the three animals. Vultures are extremely common in the Irvington area today. They were also common among the fossils discovered at Rancho la Brea. Irvington and Rancho la Brea are about 400 miles apart and differ in Mammal Age by more than a million years. Fossilized remains of ducks and geese have been found at Irvington and in the tar pits. Were vultures at Irvington about 1.3 million years ago?

Whether or not you include vultures in the ancient Irvington ecosystem depends on the rules you follow. If you decide to include only the animals whose remains have been found and identified at Irvington, vultures cannot be included. But you might decide to include animals (and plants) that could or should have been present. This brings the discussion to an extremely important consideration: Whatever your rules may be, state them clearly so that your reconstruction can be judged fairly. You must, of course, also make it perfectly clear that your reconstruction of past events merely represents that could have happened not necessarily what did happen.


 [Back to Index]