Less than an inch long, the oval-shaped creature—a species of so-called multiplacophoran dubbed Protobalanus spinicoronatus—was previously known from only a few rare and incomplete specimens, which made for inaccurate reconstructions.

"The original reconstruction was made where the plates were arranged in a long row, almost like a long worm with 17 plates down its back," said study co-author Jakob Vinther, a paleontologist at the University of Texas at Austin.

The latest P. spinicoronatus model is based on the most complete known fossil of a multiplacophoran, discovered in 2001 in northern Ohio. Partially covered in rock, the animal's shell and spikes had become fragmented as it decayed. (See pictures of strange-looking sea creatures.)

To reassemble the specimen, the team made a three-dimensional model