Thomas D. Carr. Study of this 3D reconstruction of the dinosaur called "Jane" indicates it is Tyrannosaurus rex and not a close but smaller cousin.
ScienceMagazine has a story about a new study which shows that Nanotyrannus was just a juvenile Tyrannosaurus rex. The study, which was presented at the Society of Vertebrate Paleontology in Dallas, was led by Thomas Carr, a paleontologist at Carthage College in Kenosha, Wisconsin. Not everyone agrees. Bob Bakker still thinks that Nanotyrannus was a separate species. Get all the details over at sciencemag.org.
In Dallas, Carr presented a new analysis of Jane’s skull and skeleton, based on a three-dimensional computer reconstruction of the skull which filled in missing segments and allowed him to analyze the features in more detail. His team examined microscopic “growth rings” in Jane’s calf bone, which accumulate per year of life. The team found nine such rings in the bone and space for two more, leading them to conclude that Jane was indeed a juvenile, about 11 years old when she died. Moreover, close examination of the skeleton revealed that it was still undergoing “remodeling” typical of very fast growing bone. Although younger and older specimens of T. rex are known, Jane filled an important gap in researchers’ knowledge of the growth pattern of tyrannosaurs, Carr told the meeting. “She was just about to, or had already entered, the rapid phase of growth” typical of very large carnivorous dinosaurs.
In addition, Carr argued, a comparison of Jane with the 1940s Nanotyrannus skull—made possible if both are considered juveniles—kills the idea that the original Nanotyrannus skull has unique features that T. rex does not. “Jane was heralded by some as the second coming of Nanotyrannus,” Carr said. But according to his analysis, the two skulls share a number of features once thought to be unique to Nanotyrannus, including a hole in a small jaw bone and a long and low snout. Rather than being diagnostic of a separate species, Carr concluded, such features actually characterize juvenile tyrannosaurs.
Some paleontologists at the meeting found Carr’s arguments convincing. The two skulls “are the same animal, the same species,” says Stephen Brusatte, a paleontologist at the University of Edinburgh in the United Kingdom. Zanno agrees. “Tom makes a compelling argument” that there was only one top predator in western North America rather than two. “His explanation is the simplest and most parsimonious.”
But Bakker is standing his ground. “Tom has not seen the best specimen,” of Nanotyrranus, he told Science. Yet details about that specimen—a third and nearly complete skeleton found in Montana in 2006—has not yet been published. It is mired in controversy after its owners tried—and failed—to sell it at auction for $7 million or more. Most paleontologists, citing the ethics of their profession, will not study it unless it is either donated to or purchased by a museum.