Marmaronchis Dayrat & Goulding, 2018

Dayrat, Benoît, Goulding, Tricia C., Khalil, Munawar, Lozouet, Pierre & Tan, Shau Hwai, 2018, Systematic revision one clade at a time: A new genus of onchidiid slugs from the Indo-West Pacific (Gastropoda: Euthyneura: Pulmonata), Raffles Bulletin of Zoology 66, pp. 814-837 : 823-824

Marmaronchis Dayrat & Goulding , new genus

Type species. Marmaronchis vaigiensis , designated here.

Etymology. The name Marmaronchis is a combination of mármaros (Ð μάρμαρος), which means ‘marble’ in Greek (because the dorsal notum of Marmaronchis slugs is marbled with dark and light areas), and onchis, a word derived from the Greek Ð Ôgkoj and one of the early names used to refer to onchidiid slugs.

Gender. Gender. Masculine, gender of onchis (ICZN Art. 30.1.1; ICZN, 1999), a word derived from the masculine Greek word Ð Ôgkoj, which means ‘mass’ or ‘tumour’. As a result (ICZN Art. 31.2; ICZN, 1999), the endings of the specific names vaigiense (an adjective from the Latinisation of a geographical name — Vaigiou) and marmoratum (a Latin adjective) must be changed from neuter gender (because Onchidium is a name of neuter gender) to masculine gender (i.e., vaigiensis and marmoratus ).

Diagnosis. Body not flattened. No dorsal gills. Dorsal eyes present on notum. Retractable, central papilla absent. Foot wide, approximately half of total width. Eye tentacles short and narrow. Eyes at tip of ocular tentacles. Pneumostome median, closer to anus and pedal sole than to hyponotum margin. Female opening close to anus. Male opening below and on left of right ocular tentacle (in dorsal view). Intestinal loops of type I. Rectal gland present. Penial hooks present. Accessory penial gland present, with spine but no muscular sac.

Diagnostic features. Externally, Marmaronchis is not easily distinguished from other onchidiid genera. It could be confused with Melayonchis and Wallaconchis Goulding

& Dayrat in Goulding et al., 2018b. Internally, however, Marmaronchis is characterised by a unique combination of anatomical traits which is not found in any other onchidiid genus: intestinal loops of type I, rectal gland present, and accessory penial gland present.

Remarks. Onchidium vaigiense and Onchidium marmoratum belong to a clade that is separate from all other onchidiid genera ( Figs. 1 –4). A new generic name is needed for that clade because no existing generic name applies to it (for a recent review of the application of all onchidiid genusgroup names, see Dayrat et al., 2017). More specifically, molecular phylogenetic analyses here clearly show that O. vaigiense and O. marmoratum do not belong to Onchidium (type species: Onchidium typhae Buchannan, 1800 ) which agrees with anatomical data because both O. vaigiense and O. marmoratum lack the distinct synapomorphy of Onchidium (large, conical, pointed papillae on the dorsum of live animals).

Figures

Fig. 1. Phylogenetic tree showing relationships between Marmaronchis individuals based on mitochondrial COI sequences. Numbers above branches are the bootstrap values (Maximum Likelihood analysis) and below are the posterior probabilities (Bayesian analysis); only significant numbers (>75% and>0.9) are indicated. All other sequences serve as outgroups. Information on individually-identified Marmaronchis specimens can be found in the list of material examined.