299 — Late Ediacaran trackways produced by bilaterian animals with paired appendages

In South China, a new fossil may represent the earliest-known instance of bilaterian paired-appendages in the fossil record. Dated to the Ediacaran Period (635 – 541 Mya), this fossil (according to current best-interpretation) is a trackway: fossilized footprints. This trackway is evidence of an animal with bilaterally symmetric, “paired” appendages — appendages for which the other side of the body has a matching appendage. This is perhaps a body plan that we now take for granted, but in the Ediacaran, Bilateria was a whole new thing. These tracks indicate an animal that used leg-like structures to stand up out of the sediment at the sediment-water interface, and walked forward (like a lizard, not like a crab).

The only other well-known commonly found structures from this period and geographic area are fossilized indications of small burrows, which suggests that it’s possible that our bilaterally symmetric fossil friend also burrowed in the sediment.

The fossil is shown with several different lighting directions in order to demonstrate the relief. It makes me think that it’d be really interesting to have a consistent way of representing 3D data on a fossil when 3D scanning technology is not available — perhaps something like the ability to interactively modify the light positioning, a la this recent work by Tyler Morgan-Wall on ray-trace based relief shading.