The ancient fish left an impression of its distinctive armored exterior plates in 370 million-year-old red sandstone deposits in north-central Pennsylvania, researchers from Drexel University reported Wednesday.
Taking advantage of a technique similar to that used by forensics technicians, researcher Ted Daeschler made a rubber cast of the impression by pouring latex onto the rock.
Once the latex hardened, Daeschler peeled it out and dusted its surface with a fine powder to better show the edges of the bony plates and the shapes of fine ridges on the fish's bony armor, in the same way a crime scene investigator would dust for fingerprints.
That allowed him to identify the find as a new species of extinct armored fish dubbed Phyllolepis thomsoni, a Drexel release said.
The fish is from the late Devonian period, at a time long before dinosaurs walked the Earth although, geologically speaking, not long before the very first species began to walk on land, leading to the rise of the first vertebrate species with limbs, the researchers said.