Australia: The Land Where Time Began

A biography of the Australian continent 

These were sessile marine organisms that lived in the Early Cambrian. Before the evolution of the coral animals they were the first reef builders. Appearing in the Early Cambrian about 530 million years ago, they diversified widely with more than 100 families being known. Their reign was to be short lived, by 520 million years ago they were in steep decline, and by the Middle Cambrian most were extinct, and the last known species, Antarcticocyathus webberi disappeared from the fossil record almost at the end of the Cambrian.

It has been suggested that their extinction may have been related to the appearance and diversification of the demosponges.

They inhabited shallow seas around the coasts of the continents, their widespread distribution suggesting they may have dispersed by planktonic larvae. Their relationships are uncertain, though many believe they were probably a type of sponge. The name pleosponge has been used for them by some scientists.

Links

http://www.wisegeek.com/what-are-archaeocyathids.htm http://en.wikipedia.org/wiki/Archaeocyatha http://www.ucmp.berkeley.edu/porifera/archaeo.html http://www.biodiversitylibrary.org/bibliography/5235