Phys.org has a story about our friend the Tullymonster. Recall that last year there was quite a bit of discussion about the classification of the Illinois State Fossil. Two independent groups of scientist published paper last Spring, one claiming that it was a vertebrate and one even claimed it to be a primitive lamprey.
Now a group of paleobiologists led by the University of Pennsylvania's Laren Sallen, say all that research was wrong. The original paper is open access and appears in the Journal Paleontology.
"This animal doesn't fit easy classification because it's so weird," said Sallan, an assistant professor in Penn's School of Arts & Sciences' Department of Earth and Environmental Science. "It has these eyes that are on stalks and it has this pincer at the end of a long proboscis and there's even disagreement about which way is up. But the last thing that the Tully monster could be is a fish."
In a new report in the journal Palaeontology, Sallan and colleagues argue that the two papers that seemingly settled the Tully monster debate are flawed, failing to definitively classify it as a vertebrate. The mystery of the Tully monster, known to scientists as Tullimonstrum gregarium, remains.
"It's important to incorporate all lines of evidence when considering enigmatic fossils: anatomical, preservational and comparative," said Sam Giles, a junior research fellow at the University of Oxford and coauthor of the study. "Applying that standard to the Tully monster argues strongly against a vertebrate identity."
Sallan and Giles coauthored the work with Robert Sansom of the University of Manchester, Penn postdoctoral researcher John Clarke, Zerina Johnason of the Natural History Museum London, Ivan Sansom of the University of Birmingham and Philippe Janvier of France's Muséum National d'Histoire Naturelle.
The Tully monster has been known since the 1950s, when the first fossils were found in Mazon Creek fossil beds in central Illinois. Since then, thousands of specimens have been identified from the area. The species is the state fossil of Illinois and even graces the side of UHauls. But none of the attempts to classify it to an animal group over the last half century had stuck.
"Initially it was published as a worm," Sallan said. "There is a well-constructed argument that it is some kind of mollusc, like a sea cucumber. And there's another very strong argument that it's some kind of arthropod, similar to a lobster."
