The provenance and palaeobiology of a new multi-vaned, chambered frondose organism from the Ediacaran (later Neoproterozoic) of South Australia

Abstract

Abstract The new, large, frondose and stalked, Ediacaran (late Neoproterozoic) ‘petalonamid’ Pambikalbae hasenohrae gen. et sp. nov . is preserved in a three-dimensional manner within sandy channel fills occurring directly below the Ediacara Member of the Rawnsley Quartzite on the ‘Nilpena’ pastoral property at a western outlier of the Flinders Ranges, South Australia. Pambikalbae hasenohrae was made up of numerous chambered vanes supported by a tapering axial stem and an anchoring stalk. Chambers forming the vanes were commonly infilled with sediment, though variably flattened; groups of vanes representing individual specimens can extend as much as c . 3.7 cm deep through the hosting sandstone matrix. Several series of chambers present in each vane abut at zigzag sutures. Pambikalbae is clearly not a cnidarian sea pen, but nevertheless exhibits characteristics suggestive of an evolutionary grade comparable to that of known modern cnidarian divisions. Though the serial geometric configuration of its thin integument seems ideally suited to house symbiotic microbial photoautotrophs, our appraisal of the palaeoecology of Pambikalbae is supportive of its being a heterotrophic suspension feeder. Pambikalbae may plausibly be a highly derived hydrozoan, part of the ancestral stock of the Siphonophorida, or a sister group to the early Chondrophorina.