Panton's "mystery" fossil sparks a scientific debate

PANTON-If you're familiar with Vermont's famous Champlain Black or Panton Stone-a much sought after landscaping stone found in deposits along Lake Champlain from Vermont and New York to the Canadian border-you may have admired the ubiquitous marine fossils embedded in its dense gray matrix. These ancient reef creatures include a variety of seashells, crablike animals called trilobites, and other invertebrate denizens of the prehistoric deep.

Among the Panton Stone's ancient reef fauna are distinctive, disk-shaped objects commonly called "sunflower coral". These sunflower-like fossil disks were a big part of the local reef community and are frequently found in western Addison County-some grew up to three feet or more in diameter.

Regarding the ancient makers of the unusual disks, scientists have been debating the origin question since this fossil was first discovered in the early 19th century. While some have identified the fossil as coral, others have identified it as a kind of hard porifera or sponge built up by tiny, protozoa-like critters.

Today, most fossil experts believe "sunflower coral" was the product of green sea algae-unicellular and colonial plants.

If their theory is correct, then the layered, accretionary disks found in Vermont were built up by prehistoric algae absorbing minerals and nutrients via sea water and then expelling the waste to build up porous mounds.

A few fossil-collecting mavericks consider "sunflower coral" as a kind of mysterious quasi-sponge, but they are unable to pin down exactly what tiny vanished critters created the calcite structures. But even with most researchers now favoring green algae as the source of "sunflower coral" found in the Panton Stone-with a few porifera holdouts-it remains to be officially classified to any biological phyla.

In 1830, French zoologist Henri Marie Ducrotay de Blainville gave the fossil its Latin, scientific name, Receptaculites (pronounced: receptacle-eye-tees), named for the hundreds of tiny receptacle-like chambers found in the disks. De Blainville also helped date the Panton Stone fossil-and its fellow turned-to-stone reef lifeforms-to approximately 480-450 million years ago.

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