Paraganitus ellynnae is a species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of sea slug

Slug

Slug is a common name that is normally applied to any gastropod mollusc that lacks a shell, has a very reduced shell, or has a small internal shell...

, an acochlidian, a shell-less marine

Marine (ocean)

Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...

 gastropod mollusk in the family Microhedylidae

Microhedylidae

Microhedylidae are a taxonomic family of sea slugs, marine gastropod mollusks within the clade Acochlidiacea.- 2005 taxonomy :Microhedylidae has been listed as a synonym of Parhedylidae in the taxonomy of Bouchet & Rocroi . Ganitidae Rankin, 1979 has been listed as a sole family within Hedylopsoidea...

.

Paraganitus ellynnae is the only species in the genus Paraganitus.

Description

Paraganitus ellynnae is smaller than 5 mm and is externally symmetric. It has no shell in adults, and no operculum in adults. It has also no head shield and no posterior shield. It is able to partially retract parts of its anterior body into a temporal visceral cavity. The visceral sac is largely separated from the rest of the body. The mantle

Mantle (mollusc)

The mantle is a significant part of the anatomy of molluscs: it is the dorsal body wall which covers the visceral mass and usually protrudes in the form of flaps well beyond the visceral mass itself.In many, but by no means all, species of molluscs, the epidermis of the mantle secretes...

 is robust. The visceral hump is conical. The tail is short and pointed. The foot is narrow, the anterior foot edge is rounded and it can crawl on the whole foot. It has no mantle cavity. It has elongated/pointed rhinophore

Rhinophore

A rhinophore is one of a pair of club-shaped structures which are the most prominent part of the external head anatomy of a group of sea slugs, marine gastropod opisthobranch mollusks in the order Nudibranchia, the nudibranchs, specifically the dorid nudibranchs.- Etymology :The name relates to the...

s. Like all acochlidians, it has oral (= labial) tentacles. Paraganitus ellynnae has long and slightly recurved oral tentacles. Oral tentacle nerves have been present in all examined acochlidians to date, but those nerves were not examined in this species.

Like all acochlidians, it lacks plicate gills. The position of the anus is unknown. It has no calcareous spicules, but it has integumental concrements. It has no keel on the visceral hump.

It has aggregations of precerebral ‘accessory ganglia’. It has no eyes. The presence or absence of Hancock's organ

Hancock's organ

Hancock's organ is a lateral sensory organ of gastropods, a sense organ found in some sea snails. This organ is found in most shelled opisthobranchs....

 is unknown. It has prepharyngeal CNS

Central nervous system

The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...

 as is the case in all other acochlidians.

Ecology

Paraganitus ellynnae is marine and is a mesopsammic species, in other words, these very small slugs live in the interstitial spaces of marine sands.