Triangular-Shaped Ediacaran Fossil Thectardis Avalonensis From the Sonia Sandstone, Jodhpur Group, Marwar Supergroup, Western India

The present study records the triangular-shaped Ediacaran fossil identified as Thectardis avalonensis from the Sonia Sandstone of Jodhpur Group, Marwar Supergroup, western India. These Ediacaran fossil specimens are preserved in convex (positive) relief, but one is in negative relief on the bedding planes of sandstone in the Sursagar mines area. T. avalonensis is well-preserved, unskeletonized, elongated and triangular in shape, with sharp, raised marginal rims or ridges that widen at the triangular base and taper towards the apex of the organism. This Ediacaran triangular-shaped T. avalonensis organism is recorded for the first time from India. The phylogenetic affinity of T. avalonensis is still uncertain, as some have interpreted it as a sponge based on a body plan consistent with the hydrodynamics of the sponge water-canal system, which lacked a mouth or movement and its length–width ratio of more than 1.6. As well as these, T. avalonensis may also belong to Diskagma-like lichen or living Cladonia-like lichen group and the Auroralumina-like cnidarian organisms of the Ediacaran crown group.