Archimicrura, Chernyshev, 2025

Genus Archimicrura gen. nov.

urn:lsid:zoobank.org:act:648123AE-59B0-41FD-B830-40735AB44840

Type species. Micrura ignea Schwartz & Norenburg, 2005 View in CoL .

Diagnosis. Lineidae with lateral horizontal cephalic slits and caudal cirrus. Cutis glands separated from outer longitudinal musculature of body wall by thin connective tissue layer. Thin layer of diagonal musculature present between body middle circular and inner longitudinal muscle layers. Longitudinal muscle plate between rhynchocoel and foregut present. Proboscis typical heterotype (see Chernyshev 2015); outer longitudinal musculature well developed; two muscle crosses present; and neural sheath not developed into separate nerves. Vascular blood plexus absent in foregut region. Cerebral ganglia without outer neurilemma; neurochords and neurochord cells absent. Three frontal organs.

Generic composition. Archimicrura ignea ( Schwartz & Norenburg, 2005) comb. n.

Remarks. Archimicrura ignea holds a basal position in the phylogenetic tree of Lineidae and is a sister taxon to the rest of the lineids that form Clade 1 sensu Kajihara et al. (2022). The lack of outer neurilemma is a trait characteristic of Micrura , but in M. fasciolata , the proboscis lacks outer longitudinal musculature. Unfortunately, the original description of M. ignea does not provide data on some of the structures ( Schwartz & Norenburg 2005). Archimicrura ignea has an archaic structure of the pseudocnidae, not typical of other Lineidae ( Magarlamov et al. 2021) . The diagonal muscles located between the middle circular and inner longitudinal musculature of the body wall may also be a plesiomorphic state.

Etymology. The new generic name is feminine in gender, formed by adding the Greek prefix archi - (meaning “ancient”) to the name Micrura .