 Ancient Shark Fossil
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Oct. 3, 2003 — What might be dubbed the original "Jaws" — the world's oldest fossil of a toothed shark from Canada — has been found intact in a rare discovery that is expected to shed new light on the evolution of both teeth and sharks.
The small 409 million-year-old shark was identified from a New Brunswick Museum specimen collected in 1997 near Campbellton, New Brunswick said a team led by Randall Miller, of the museum's paleontology laboratory, in a report Thursday in the British journal Nature.
"It has two rows of teeth and paired pectoral fin-spines — a feature previously unknown in cartilaginous fish," the journal said in a media release on the find. "It beautifully illustrates a well-known animal group in its early stages of evolution."
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The report said the fossil is from a very early shark species known as Doliodus problematicus — previously known only from their teeth — and is a highly unusual find because its body is so complete and articulated. It includes preserved, cartilage, teeth, scales and the surprising large fin-spines.
Because sharks are mostly cartilage — not bone — most evidence of ancient species has, until now, been mainly of single teeth and other isolated body parts.
The specimen from Canada is between 15 and 20 million years older than the previous record holder, a South Australian species known as Antarctilamna prisca.
The specimen is cleaved in five parts, revealing a series of transverse sections through its head and other body regions and, based on comparisons with the anatomy of other sharks, it was probably no more than about 30 inches long in total when it was alive, the report said. It had about 15 rows of tooth "families," consisting of up to three teeth each, arranged along its lower jaw.
Previous discoveries of sharks from the Early and Middle Devonian periods were mainly from the ancient southern super-continent of Gandawana or its near neighbors, which had led to suggestions that sharks evolved there, although the teeth found earlier from this species were problematical because they suggested otherwise.
The new find, however, clearly establishes that sharks were in the waters of the northern super-continent of Laurentia by the early Devonian, the report said: "Northern Gondwana and Laurentia were possibly close, across a shallow shelf connecting north Gondwanan shoreline locales."
An Australian fish expert and member of the team, Susan Turner, of Monash University and the Queensland Museum, traveled to Canada last year to work with Miller on the specimen.
She said in local news reports at the time that the find indicated that both the environment and the rock that housed the fossil were special. The rock was very fine-grained and originally may have been mud from a warm seaside lagoon.
Ancient fish were thought to lack jaws and to rely on tough scales to grind their food.
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