Eolimax

## Species

†Eolimax ediacaraensis

Eolimax is an extinct genus of possibly bilaterian or vendobiotan that lived during the Ediacaran period. Eolimax has been found in the Ediacara Cliffs of Galand.

## Description

Eolimax is a relatively common animal within the Ediacara Cliffs, and has possibly been found elsewhere. It a soft-bodied organism. All fossils are oval in outline. It is assumed that the organism was capable of stretching its front and back parts of the body for locomotion. The animal seems to possess bilateral symmetry, however it unclear whether it is a true bilaterian similar to Protobilateria, and has been of uncertain placement.

Eolimax is described as having a dorsal covering, also known as a "soft shell" that ranges from 2 to 5 centimeters in length and between 1 to 2 centimeters in width and was highly flexible. The shell ranged from 50 to 200 millimeters in height.

The animal also possessed a frilled fringe that was possibly used for either locomotion or as part of the respiratory system, performing a function similar to gills. The fringe extended past the soft shell, suggesting that Eolimax either possessed an ineffective respiratory system that required a lot of oxygen, or that it lacked predators.

## Ecology

Eolimax lived in shallow waters, no deeper than 30 meters, sharing the calm, oxygenated seafloor with microbial mats and other Vendobiota.

Eolimax probably grazed along the microbial mats, however it is also possible that Eolimax could've been predator in nature, as it was more mobile than other known Ediacaran animals who lived along the seafloor. There is also a significant lack of evidence for asexual reproduction in fossils of Eolimax, suggesting that it produced sexually, possibly being the earliest or one of the earliest pieces of evidence of sexual reproduction in animals, and also possibly why Eolimax could move more efficiently than other animals at the time.

## Classification

The exact placement of Eolimax in the Animal Kingdom is unclear. It is formally placed within Vendobiota, but some claim the Eolimax is a basal bilaterian or even possibly an early mollusk. Eolimax shares some fringed characteristics with protoarticulates which are considered to be vendobiotans, however they also lack a segmented body, which is seen in both protoarticulates and Protobilateria.

The idea that all early bilaterians were worm like and segmented, as seen in Protobilateria, has also been a cause as to why Eolimax is not considered a bilaterian, however, if it was a bilaterian it would mean that bilaterians likely existed long before Eolimax, possibly by the start of Ediacaran, and if it is a mollusk, then it is not only the oldest known bilaterian, but also means that early ecdysozoans diversified long before the Rimunian, suggesting that Eolimax could either be an ancestorial mollusk, or even an ancestor of cyclopsians or triopsians, and early cyclopsians lacked hard shells a seen in Monoculus.

## Theoretical importance

The Rimunian explosion resulted in the rapid diversification of life on Ratera, and saw the emergence of most of Ratera's main groups of animals. The Rimunian explosion started early on in the Rimunian, around 540 million years ago, and lasted until at least 520 million years ago, although its affects are still present today.

The majority of animals that more complex than cnidarians are split into two groups, deuterostomes, and ecdysozoans. The mollusk-like characteristics of Eolimax would make it an ecdysozoan. If so, then it is not only the earliest known mollusk, but also the oldest known ecdysozoan, and lineages of ecdysozoans would've had to diverge long before the Rimunian explosion. At the very least, Eolimax is more closely related to mollusks, cyclopsians, and triopsians, meaning that that half of the ecdysozoan group diverged before the Rimunian explosion, whereas the other half, containing arthropods and their relatives diverged during the Rimunian explosion. Furthermore, seeing that fossils attributed to relatively modern-looking cnidarians have been discovered in similarly aged rock, that would mean that the divergence of bilaterian and cnidarian lineages happened well over 580 million years ago.