ABSTRACT
A combination of population censuses, field and laboratory experiments using specimens of Eucidaris tribuloides, Diadema antillarum, Tripneustes ventricosus and Echinometra lucunter have been used to derive predictions as to the taphonomic bias likely to affect fossil occurrences of species assigned to the echinoid families Cidaridae, Diadematidae, Toxopneustidae and Echinometridae. Results of field work indicate that, in Caribbean reef and near-reef environments, the echinoids under study are reduced to essentially bleached carcasses of disarticulated spines, lantern elements and a corona entirely denuded of organic material within six days. The rapidity with which biostratinomic processes act on the echinoids is underscored by the results of the population censuses in that there is no correlation between the distributions of live and dead echinoid material. Tumbling experiments using bleached carcasses reveal that amount of disturbance has no significant effect on the degree of breakage suffered by the corona or spines and lantern elements. However, significant differences do occur between taxa in the amount of coronal breakage as well as the contribution of spines and lantern to a recognizable (> 2mm) size fraction. This suggests that the taphonomic biases affecting fossils assigned to each family may be different. Field and laboratory results have been synthesized into a predictive model of the preservational styles expected to predominate occurrences of fossil species assigned to each echinoid family. A test of the model using literature-derived data of echinoid occurrences reveals that observed styles of preservation in each family are different and that they generally agree with the predictive model. These results suggest that actualistic studies of echinoid taphonomy are useful in the interpretation of echinoid generic diversity.
