ST. PAUL — A write-in campaign for a prehistoric giant beaver that weighed more than 200 pounds has secured it a spot on a list of possible candidates for state fossil.

The write-in campaign has been so successful that the beaver, or Castoroides ohioensis, is now in the lead among possible state-fossil candidates proposed by the Science Museum of Minnesota. The fossil, found in St. Paul, dates back to the Pleistocene epoch and is estimated to be 2.58 million years to 10,150 years old.

Minnesota is one of just seven states without a state fossil, said Alex Hastings, the Phillip W. Fitzpatrick Chair of Paleontology at the Science Museum of Minnesota, who is leading an effort to have an official state fossil in Minnesota.

Hastings put together a list of eight candidates — representing different creatures, different parts of the state and different geologic times — for consideration. As of Tuesday, more than 2,100 people had voted, he said.

The entry for Castoroides ohioensis notes that it had “buck teeth and aquatic lifestyle” and “was the size of a small bear,” according to officials with the St. Paul museum.

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The other top two vote-getters as of Tuesday were: Stromatolite, a fossil made from photosynthesizing bacteria found primarily in northern Minnesota that date back 1.9 billion years, and Bison antiquus, a bison whose fossils date back about 60,000 to 4,270 years ago and are found in central and southern Minnesota.

Voting ends Oct. 1; the winner will be announced on National Fossil Day, Oct. 13. Science Museum officials will then reach out to legislators who represent the district where the fossil was found and ask for help in pursuing legislation to have it designated the official state fossil, Hastings said.

Castoroides ohioensis almost became Minnesota’s state fossil back in 1988, but the measure failed in the Legislature.