With their find, Matz and his colleagues argue that fossil traces cannot be used alone as evidence that multicellular animals were evolving during the Precambrian, slowly setting the stage for the Cambrian explosion.
"I personally think now that the whole Precambrian may have been exclusively the reign of protists," says Matz. "Our observations open up this possible way of interpreting the Precambrian fossil record."
He says the appearance of all the animal body plans during the Cambrian explosion might not just be an artifact of the fossil record. There are likely other mechanisms that explain the burst-like origin of diverse multicellular life forms.
DNA analysis confirmed that the giant protist found by Matz and his colleagues in the Bahamas is Gromia sphaerica, a species previously known only from the Arabian Sea.
They did not observe the giant protists in action, and Matz says they likely move very slowly. The sediments on the ocean floor at their particular location are very stable and there is no currentperfect conditions for the preservation of tracks.
Matz says the protists probably move by sending leg-like extensions, called pseudopodia, out of their cells in all directions. The pseudopodia then grab onto mud in one direction and the organism rolls that way, leaving a track.
He aims to return to the location in the future to observe their movement and investigate other tracks in the area.
Matz says the giant protists' bubble-like body design is probably one of the planet's oldest macroscopic body designs, which may have existed for 1.8 billion years.
"Our guys may be the ultimate living fossils of the macroscopic world
|Contact: Dr. Misha Matz|
University of Texas at Austin