Dimarcusidae is a
family
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
of
triclad
A planarian is one of the many flatworms of the traditional class Turbellaria. It usually describes free-living flatworms of the order Tricladida (triclads), although this common name is also used for a wide number of free-living platyhelm ...
s found mostly in freshwater habitats of
cave
A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can refer to smaller openings such as sea ...
s, although at least one species, ''
Rhodax evelinae'', occurs in surface waters.
Currently the family contains only seven species distributed in five genera, although the total number of species is thought to be much higher.
Description
The morphological features uniting species of Dimarcusidae are related to the
reproductive system
The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are als ...
. Their ovaries are located more posteriorly than in most triclads, which usually have them close to the brain. The penis in species of Dimarcusidae contains glandular elements and the common ovovitelline duct is perpendicular to the female genital duct.
Taxonomy
The family Dimarcusidae was erected in 1972 by Mitchell and
Kawakatsu to include a new species, ''Dimarcus villalobosi''. However, the same species had been briefly described by Benazzi in the same year as ''
Opisthobursa mexicana'' and this name had priority, with ''Dimarcus villalobosi'' becoming a junior synonym. As a result, the family is called Dimarcusidae despite the absence of a valid genus ''Dimarcus''.
Phylogeny
Historically, species of Dimarcusidae have been classified as members of the suborders
Maricola (marine triclads) or Paludicola (freshwater triclads). They received their own suborder, Cavernicola, in 1990, although their relationship to other triclads had not been settled.
Recent molecular studies, however, suggest that Cavernicola is the sister group of Maricola, thus being more closely related to marine than to freshwater triclads.
Genera
Currently the family Dimarcusidae includes the following five genera:
*''
Balliania''
Gourbault, 1978
*''
Kawakatsua''
Sluys, 2019
*''
Novomitchellia''
Özdikmen, 2010
*''
Opisthobursa''
Benazzi, 1972
*''
Rhodax''
Marcus, 1946
References
{{Taxonbar, from=Q3028057
Cavernicola (worm)