Wednesday, May 4, 2011

May 2011 Fossil of the Month

Corals, Crinoids & The Like

Crinoids are unusually beautiful and graceful members of the phylum Echinodermata. This is the phylum that brings you starfish, sea urchins, and sand dollars. The crinoids are a breed apart however, they resemble an underwater flower. Some even have parts that look and act like roots anchoring them to the ocean floor. They are commonly called sea lilies. Their graceful stalks can be meters long. Other varieties have no stalks or root like parts. They are commonly known as feather stars. Unlike the sea lilies the feather stars can move about on tiny hook like structures called cirri. Crinoids are alive and well and living in an ocean near you! They are also some of the oldest fossils on the planet. The earliest come from the Ordovician Period. Most of the Paleozoic forms died out in the great Permian extinctions. The few species surviving into the Mesozoic Era thrived. Many new species evolved during this time including the ancestors of the present day class Articulata. Corals are among the most colorful animals in the sea. Most corals live in warm, shallow, tropical seas and feed on plankton. The oldest fossil corals are from the Ordovican period, over 450 million years ago. Corals are marine animals with a sac-like body, mouth, tentacles and skeleton. It is the skeleton that survives in the fossil record. Of the varieties of fossilized corals found throughout the world exquisitely detailed specimens from the mountains of Indonesia are among the most unique. In Indonesia, entire coral heads are often completely preserved and appear just as they did 20 million years ago, although their density is much changed by replacement with silica, iron, manganese and other minerals. There are fern corals, brain corals, hex corals, honeycomb corals and many more. Florida and Georgia in the USA are also import sources of fossil coral. In fact Florida has declared fossil coral to be the Florida State Rock. Fossil coral pieces are sought after by gemstone and fossil collectors around the world as well as being used in beads and other jewelry.