Monday, February 3, 2020

Archimedes Bryozoan Fossil with Holdfast

Here is a rare example of an Archimedes sp. bryozoan fossil with part of holdfast (root like structures) exposed. It was used to anchor it to the seabed. Another rare feature is the part of the netting or mesh structure that extended out into the water along the edge of the creature's screw shape. The name for water pump screw credited to the Greek engineer Achimedes of Syracuse (287-212 BC).

The naming of this genus is credited to Indiana's first state geologist David Dale Owen (1807-1860) to his publication, A Geological Reconnoisance and Survey of the State of Indiana in 1837 and 1838 in 1838. He later wrote an article for The American Journal of Science and Arts, Volumes 43-44 (1842) entitled Regarding Human Foot-Prints in Solid Limestone. He writes "characterized by a very remarkable fossil coralline, resembling the Retepora of Lin., but verticillated spirally like a continuous screw; described by Lesueur under the appropriate name of Archimedes.*" He writes that on page 19 with a foot note listing, "I am not sure that Lesueur ever published his description of this fossil; but I know that while he resided here (at New Harmony) he engraved a plate containing several views of it, with that intention. He considered it, I believe, a new genus; but it may be only a new species of Retepora; if so, most aptly entitled Retepora Archimedes."

Owen is referring to the French naturalist Charles Alexandre Lesueur (1778-1846). He lived at New Harmony Indiana from 1826-1837. He was good friends with Thomas Say who named the Pentremites blastoid fossil genus and is buried at New Harmony.

The fossil pictured above was part of the James Conkin collection. This bryozoan existed in the Mississippian Period, the genus died out in the Permian Period. No locality was listed with this fossil but I am guessing it was found in Indiana or Kentucky. Thanks to Kenny for the picture.