New species of ancient ceolacanth discovered in Texas
October 29 2012 Lewis Smith
The Ceolacanth fossil discovered in Texas
photo: SMU Research
A new species of ancient ceolacanth has been discovered by a fossil collector walking across a housing development.
The tiny fossilised remains of the fish had been washed into a small gully by water running off land in Fort Worth, Texas, cleared in preparation for house-building.
The fossil was spotted by Robert R Reid, who lives close to where it lay, who donated it to Southern Methodist University in Dallas where it was identified as a 100 million-year-old fish.
Ceolacanths are more closely related to humans than any other fish, having shared their most recent common ancestor with vertebrate animals.
They also have a boney support in their fins which is the predecessor to true limbs and led in time to animals crawling onto land for the first time.
The specimen found in Fort Worth was named Reidus hilli and represents the 81st species of coelacanth, two of which are still alive today.
Mr Reid said: "When I found it, I could tell it was a bone but I didn't think it was anything special. I certainly didn't think it was a coelacanth."
It would have lived in the sea, like its modern relations, whereas early coelacanths are thought to have lived in fresh water fish. But while modern ceolacanths can reach three metres (10 feet) in length, the fossil species probably measured just 40cm (16 inches).
"These animals have one of the longest lineages of any vertebrates that we know," said John Graf, of Southern Methodist University.
“What makes the coelacanth interesting is that they are literally the closest living fish to all the vertebrates that are living on land. They share the most recent common ancestor with all of terrestrial vertebrates."
He said the fossil discovered in Forth Worth was a partial skull which included gular plates, bones on the underside of the jaw.
Graf, whose findings were reported in Historical Biology: An International Journal of Paleobiology, identified Reidus hilli from a partial skull, including gular plates, which are bones that line the underside of the jaw.
"Coelacanths are not the only fish that have gular plates, but they are one of the few that do," Graf said. "In fact, the lenticular shape of these gular plates is unique to coelacanths. That was the first indicator that we had a fossil coelacanth."
He added: "Reidus hilli helped me tie a group of coelacanths together into what I identify as a new family of coelacanths," he said. "This family represents a transition between the two large groups of youngest living coelacanths from the fossil record, Mawsoniidae and Latimeriidae."
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