Morphometric investigation of Tribrachidium from Nilpena Ediacara National Park, South Australia

Abstract

Nilpena Ediacara National Park (South Australia) preserves over 200 specimens of Tribrachidium heraldicum and 95 specimens of the newly described Tribrachidium gehlingi within the fossiliferous Ediacara Member. We use rotational geometric mor-phometrics to quantify the morphological variation within each species and the differ-ences between the two. Both species were found to be morphologically different from one another, forming distinct groups within the morphospace. Analysis of the symmet-ric and asymmetric shape components revealed that both species present limited deformation, suggesting they consisted of a fairly resistant material. Growth appears to have been comprised of various interacting allometric relationships that maintain a consistent overall morphology for both species, possibly constrained by its suspension feeding mode.