A mysterious fossil that has evoked images of a sea monster roaming the shallow waters of prehistoric Cincinnati may not be the remains of such a complex life form, but even so scientists are stumped as to what kind of creature (or sea plant) it was.

The researchers, who presented the finding at a Geological Society of America meeting in Dayton, Ohio, say one thing is sure: The enigmatic "blob" — discovered in elliptical pieces that, when fitted together, extended about 7 feet long and 3.5 feet wide — was once alive.

The team of scientists, along with the fossil hunter who discovered the 450-million-year-old specimen, suggest a range of possibilities: a type of huge algae or microbial mat, or even a member of the cnidarian family, which includes jellyfish (though scientists concede the jellyfish idea is highly unlikely).