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A new Jane tooth stirs debate

July 1, 1993

A new Jane tooth stirs debate

By Rod Myers, Naturalist

The discovery of a new Jane tooth and the overlooking of one discovered months ago sheds new light on the identification of Burpee Museum’s mystery dinosaur. The new tooth is believed to have come from the anterior of the maxilla, which is the upper jaw. The tooth just found in the earth of the now-famous plaster pod is bigger than an identical tooth found in October.

The October Jane tooth’s origin is not known. Both teeth, however, have a classic Tyrannosaurus rex design, which is plump and triangular shaped if observed from the front and not from the side (see drawing). Though the teeth are not as large as T. rex teeth, their shape could mean that Jane was beginning to reach T. rex adulthood. It’s argued that juvenile T. rexes had longer faces, meaning they had more teeth. As the T. rex got older, its face shortened; therefore, it lost space for the teeth, thus losing them. Jane has substantially more teeth than a T. rex, though obviously they are much smaller and all but two are shaped differently than a T. rex. The tooth serrations are also placed differently except in the teeth that resemble miniature T. rex teeth.

A small T. rex would not need big bone-crushing teeth like an adult. It would be killing smaller prey or dining on pre-chomped or sliced prepared food from the parents. The serrations on the teeth of the young would befit those for slicing as most of Jane’s are.

Evidence suggests T. rexes laid between 12 to 24 eggs in a nest site. That’s a lot of eggs for a meat-eating dinosaur, and the odds are that only 10 percent of the young made it to adulthood. The time for a T. rex to reach maturity is estimated at two to five years. That’s if dinosaurs grew as rapidly as birds. At any rate, a tremendous amount of growth and structural change occurred in the lives of T. rexes from hatching to adult. The dinosaur nest found giving the evidence that Tyrannosaurus laid many eggs in one clutch was believed to be that of a Tarbosaur, which is an Asian species of Tyrannosaur closely related to the T. rex.

But don’t make a conclusion yet; Jane is a long way from being identified. Mike Henderson, Burpee’s paleontologist, says it’s much too early to make a decision. “You have to look at the totality of the bones; one must look at all the evidence,” said Henderson. “We’ve only looked at 10 percent of the Jane bones that we have; it’s going to be a while before we are done.”

Mike said there could be another explanation for the Jane tooth looking like a T. rex besides being a T. rex tooth. “Jane could have had heterodentition; that is, she could have had different types of teeth for different jobs like we have molars for crushing and front teeth for biting. Heterodonts are unusual in the dinosaur world, but they did occur. There’s an extinct marine reptile called the Globidon that had spiked teeth in the front for grabbing and ball-like teeth in the back for crushing. There’s a twist, though; we believe the new Jane tooth that looks like a T. rex tooth came from the anterior of the upper jaw. You would expect a large bone-crushing tooth like this one would be situated in the back. T. rexes have bone-crunching teeth front and back; they are not heterodonts. One could say Jane is starting to get her adult teeth and all of the same type. We have to examine the tooth sockets before we conclude where the tooth came from.”

If the teeth are changing, other things may be changing as well. Mike brought out a post orbital, a portion of Jane’s skull. “In the Cleveland skull that’s believed to be a Nano,” he observed, “the post orbital is different than a T. rex, but in Jane’s it looks like something in between the Cleveland skull and a T. rex. Perhaps it’s in the process of changing. Jane’s skull is bigger, so perhaps it’s older and on the road more to being a T. rex.”

Mike pointed out again that it’s too early to tell what Jane is. In the early days after they knew they had a unique discovery, Robert Bakker and Peter Larson jumped into the race in predicting what Jane is. They are both aggressive, intelligent theorists who claimed Jane to be a Nanotyrannus. Mike Carr is the main proponent claiming that Jane and the Cleveland Nano are both young T. rexes. Bakker and Larson took a commanding early lead, but Carr, whose personality is much less aggressive, is gradually catching up in the race. “Carr is kinda shy, very methodical and extremely intelligent,” said Henderson.

There’s a biological term called convergence, which means that two species, though unrelated, look similar because of similar behavior. Believe it or not, that’s one of the possibilities of Jane’s identification. Jane may not even be related to a T. rex. Another possibility is that Jane could be very closely related to a T. rex like a red fox to a gray fox. Bakker and Larson figure the genetic relationship is more like the wolf and the coyote.

There are four most probable possibilities of what Jane might be. (1) Jane might be a young T. rex that’s beginning to grow into adulthood; (2) Jane could be a Nanotyrannus, a distinct species; (3) Jane could be a different species of T. rex; or (4) none of the above. The possibilities in the category range from Jane being a runt T. rex to not being related to Tyrannosaurus at all.

All the data will be in by late summer. “I will make a decision when all the evidence is in,” said Mike Henderson. Then he grinned like a 5-year-old who had just found his first fossil.

Rod Myers is a local resident with an interest in the environment and disability issues. He has an associate’s degree in science and a bachelor’s in fine arts. Rod is a member of the Audubon Society, the Wild Ones Natural Landscapers and Rockford Amateur Astronomers, Inc.

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