''Vernanimalcula guizhouena'' is an

acritarch Acritarchs are organic microfossils, known from approximately 1800 million years ago to the present. The classification is a catch all term used to refer to any organic microfossils that cannot be assigned to other groups. Their diversity refle ...

dating from ; it was 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 A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

record at the end of the Marinoan

Glaciation A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate bet ...

and the belief upon discovery it was an animal.

Discovery

The ''Vernanimalcula''

s were discovered in the

Doushantuo Formation The Doushantuo Formation (formerly transcribed as Toushantuo or Toushantou, from ) is a geological formation in western Hubei, eastern Guizhou, southern Shaanxi, central Jiangxi, and other localities in China. It is known for the fossil Lagerst ...

in China. This formation is a '' Konservat-Lagerstätte'', one of the rare places where soft body parts and very fine details are preserved in the fossil record.

Anatomy

The ''Vernanimalcula'' fossils were interpreted as showing a

triploblastic Triploblasty is a condition of the gastrula in which there are three primary germ layers: the ectoderm, mesoderm, and endoderm. Germ cells are set aside in the embryo at the blastula stage, which are incorporated into the gonads during organo ...

structure, a

coelom The coelom (or celom) is the main body cavity in most animals and is positioned inside the body to surround and contain the digestive tract and other organs. In some animals, it is lined with mesothelium. In other animals, such as molluscs, ...

, a differentiated gut, a mouth, an

anus The anus (Latin, 'ring' or 'circle') is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, the residual semi-solid waste that remains after food digestion, which, ...

, and paired external pits that were believed possible

sense organs A sense is a biological system used by an organism for sensation, the process of gathering information about the world through the detection of stimuli. (For example, in the human body, the brain which is part of the central nervous system re ...

, making it the earliest known member of the

Bilateria The Bilateria or bilaterians are animals with bilateral symmetry as an embryo, i.e. having a left and a right side that are mirror images of each other. This also means they have a head and a tail (anterior-posterior axis) as well as a belly and ...

(

animal Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and go through an ontogenetic stage ...

s with

bilateral symmetry Symmetry in biology refers to the symmetry observed in organisms, including plants, animals, fungi, and bacteria. External symmetry can be easily seen by just looking at an organism. For example, take the face of a human being which has a ...

, at least as embryos). The appearance of ''Vernanimalcula'' so early in the fossil record was believed to have had important implications if it were really bilaterian. The radiation of animals into many

phyla Phyla, the plural of ''phylum'', may refer to: * Phylum, a biological taxon between Kingdom and Class * by analogy, in linguistics, a large division of possibly related languages, or a major language family which is not subordinate to another Phy ...

would have occurred before any animal became much larger than microscopic size, making the sudden appearance of many animal phyla in the

Cambrian explosion The Cambrian explosion, Cambrian radiation, Cambrian diversification, or the Biological Big Bang refers to an interval of time approximately in the Cambrian Period when practically all major animal phyla started appearing in the fossil record. ...

an illusion and merely represented a (geologically) sudden increase in size and the development of easily fossilised body parts by

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...

in existing phyla. The description of ''Vernanimalcula'' as bilaterian has been strongly challenged. Other workers (Bengtson, Budd and co-workers) in the field have repeatedly claimed that ''Vernanimalcula'' is largely a

taphonomic Taphonomy is the study of how organisms decay and become fossilized or preserved in the paleontological record. The term ''taphonomy'' (from Greek , 'burial' and , 'law') was introduced to paleontology in 1940 by Soviet scientist Ivan Efremov t ...

artefact generated by phosphate growth within a spherical object such as an acritarch, and thus ''Vernanimalcula'' was not even an

, let alone a bilaterian. Chen ''et al.'' initially defended their interpretation of ''Vernanimalcula'' against the claims of Bengtson and Budd. Petryshyn ''et al.'' examined additional fossils resembling ''Vernanimalcula'' and concluded that the fossils are "likely biogenic in nature."

References

{{Taxonbar, from=Q135440 Acritarch genera

Discovery

Anatomy

See also

References