Palaeoscolecid scleritome fragments with 'Hadimopanella' plates from the early Cambrian of South Australia

Abstract

Phosphatized articulated palaeoscolecid scleritome fragments with attached 'Hadimopanella' Gedik, 1977 plates are described from the lower Cambrian Mernmerna Formation of South Australia. 'Hadimopanella' is principally known from single, isolated, button-shaped, phosphatic sclerites. The new articulated material from South Australia reveals for the first time the configuration of plates referable to Hadimopanella within the scleritome. The scleritome fragments represent the main trunk sections of the cuticle with anterior and posterior terminations lacking. Each annulus on the trunk is ornamented by rows of irregularly alternating 'Hadimopanella' plates. The large majority of plates display a single, centrally located, conical node referable to the form species 'H. apicata' Wrona, 1982. However, individual plates display considerable morphological variation with plates situated along the flattened trunk margin identical to the form species 'H. antarctica' Wrona, 1987. The South Australian material displays the detailed scleritome configuration of cuticular plates and platelets and demonstrates irrefutably that plates of the form species 'H. apicata' and 'H. antarctica' occur as mineralized cuticular elements on the same palaeoscolecid scleritome.