TAPHONOMY OF CLYPEASTER ROSACEUS AS MODEL FOR THE PRESERVATION POTENTIALS OF 3-DIMENSIONAL MULTI-ELEMENT SKELETONS

The tests of clypeasteroids are unique within the echinoids. The plates that make up the skeleton are not only interconnected by specialized skeletal structures, but also by differentiated internal supports connecting the oral and aboral sides of the test. Clypeasteroids test are also serve as substrates for encrustation and bioerosion. Although their taphonomy has been included in fossil examples especially if occurring in mass accumulations, there are few studies on taphonomic pathways of recent clypeasteroids. The present analysis focuses on test of Clypeaster rosaceusfrom San Salvador Island, The Bahamas. The echinoid is an epifaunal grazer and can reach sizes of up to 13 cm. During life it masks itself with diverse randomly available material including stones, shells and algae.

A total number of 130 tests were collected during July and August 2015. These tests were randomly sampled irrespective of their state of preservation and also included partly fragmented examples. The tests were then analyzed for various taphonomic features including predation, spine and plate disarticulation, intra- and interplate fragmentation, surface abrasion, encrustation and bioerosion. Special emphasis was given to fragmentation patterns and the distribution of internal supports in order to detect the correlation of the presence of internal supports and presence of plate disarticulation. Major plate loss occurs often occurs in the area of the petalodium which lacks internal support while the ambital areas which are highly supported are largely intact. The surviving remains can show high rates of encrustation which indicated long surface residence times. Encrustation consists of both soft bodied and skeletal organisms. Based on this preliminary survey, the 3-dimensional tests structure seems to increase the test strength and can lead to an increased preservation potential in the fossil record.