PHOSPHATIC CUTICLE IN THYLACOCEPHALANS: A TAPHONOMIC CASE STUDY OF AUSTRIOCARIS (ARTHROPODA, THYLACOCEPHALA) FROM THE FOSSIL-LAGERSTATTE POLZBERG (REINGRABEN SHALES, CARNIAN, UPPER TRIASSIC, LOWER AUSTRIA) AUSTRIOCARIS

Thylacocephala PINNA, ARDUINI, PESARINI & TERUZZI 1982, is a recently established group of bivalved arthropods that exists since the Cambrian and is geographically widely distributed. This group was extensively studied with respect to its taxonomy, morphology and ecology, but the taphonomic pathways involved in their preservation have not received the same attention. In this study, the cuticle of the thylacocephalan Austriocaris GLAESSNER, 1931 from Polzberg (Upper Triassic, Lower Austria) is analyzed and compared with material from the Cambrian (Stage 3 and 4) and with other members of the Thylacocephala. The apatitic layer of the carapace of this bivalved arthropod is compact and no evidence of original ultrastructures has been found at this stage of research, but its carapace contains organic matter (probably in the form of kerogen, due to the presence of C, S and N in the semi-qualitative energy dispersive X-ray analyses). Austriocaris had a primary phosphatic cuticle, which is shared by all the members of this group. The taphonomical processes that occurred at the Polzberg Fossil-Lagerstatte are most likely more complicated than hitherto expected, and probably influenced by a taxonomic factor.