Vernanimalcula Fossil range: Ediacaran
The supposed "fossil" of Vernanimalcula guizhouena
Scientific classification
Kingdom: Animalia Subkingdom: Eumetazoa (unranked): Bilateria Genus: Vernanimalcula Species: V. guizhouena
Binomial name
Vernanimalcula guizhouena

Vernanimalcula guizhouena is a fossil believed by some to represent the earliest known member of the Bilateria (animals with bilateral symmetry). It is known from deposits dating to 600 to 580 million years ago. The fossils are between 0.1 and 0.2 mm across (roughly the width of one or two human hairs). Vernanimalcula means "small spring animal", referring to its appearance in the fossil record at the end of the Marinoan Glaciation (see also Snowball Earth).

The Vernanimalcula fossils were discovered in the Doushantuo Formation in China. This formation is a Lagerstätte, one of the rare places where soft body parts and very fine details are preserved in the fossil record. The Vernanimalcula fossils appear to show triploblastic structure, a coelom, a differentiated gut, a mouth, an anus, and paired external pits that could be sense organs.

The description of Vernanimalcula is not without controversy. Other workers (Bengtson and Budd) in the field have claimed that it is largely a taphonomic artefact generated by growth of phosphate within a spherical object such as an acritarch.¹ Chen et al. have defended their interpretation of Vernanimalcula against the claims of Bengtson and Budd.²

The appearance of Vernanimalcula so early in the fossil record has important implications. The radiation of animals into many phyla may have occurred before any animal became much larger than microscopic size. The sudden appearance of many animal phyla in the Cambrian Explosion may be an illusion. The Cambrian Explosion may instead represent a (geologically) sudden increase in size and the development of easily fossilized body parts by species in existing phyla.³⁴⁵⁶

References