Some creatures are so weird they seem to defy classification. They're even assigned the word "Problematica," a classification that serves as a sort of purgatory for the strangest of the strange as our understanding of the evolutionary tree of life continues to deepen. Such is the case with the Tully monster, which scientists have mulled over since a 300 million-year-old fossil was found more than 50 years ago in central Illinois, UPI reports. Last year, scientists reported in Nature that the sea creature, officially known as Tullimonstrum gregarium, is a vertebrate related to the lamprey, pointing to a "primitive backbone" once thought to be its gut. Now, in a Science Daily news release, paleobiologists say not so fast.
Reporting this week in the journal Palaeontology, researchers claim last year's research was flawed, and that "the last thing the Tully monster could be is a fish." They point to its eyes on stalks, which are simple structures without lenses (vertebrates boast complex eyes), as well as the fact that it is lacking in structures that all aquatic vertebrates are believed to possess. Lauren Sallan says that arguments in favor of it being a kind of arthropod like a lobster or a kind of mollusk like a sea cucumber are "well-constructed," and notes that while there are "plenty of weird things and that's great, if you're going to make extraordinary claims, you need extraordinary evidence." Misassignment, she warns, "really affects our understanding of vertebrate evolution." (Speaking of classification, scientists have discovered our 79th organ.)
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