Paratritonia Baba 1949

Silva, Felipe De Vasconcelos, Pola, Marta & Cervera, Juan Lucas, 2023, A stomach plate to divide them all: a phylogenetic reassessment of the family Tritoniidae (Nudibranchia: Cladobranchia), Zoological Journal of the Linnean Society (Zool. J. Linn. Soc.) 199 (2), pp. 445-476 : 471

Genus Paratritonia Baba 1949

Type species: Paratritonia lutea Baba 1949 , by original designation. To date, this is a monotypic genus.

Diagnosis: Rachidian tooth unicuspid, denticulate. Digestive system arrangement holohepatic. Outermost lateral teeth denticulate.

Morphology: Body slender, length up to 35 mm. Six simple velar processes. Six to seven pairs of arborescent gills. Rachidian tooth unicuspid and denticulate. First lateral tooth differentiated. Outermost lateral teeth denticulate, bearing 20–25 accessory denticles. Large number of lateral teeth (about 100–110 per half row). Gonopore at beginning of one-third of body length on right side, below first pair of gills. Anus and nephroproct below second pair of gills.

Remarks: The monotypic Paratritonia is included in Marioniinae based on the presence of ‘chitinous stomach plates’ defined by Baba in its original description (1949). This does not agree with the description of the stomach plates of P. lutea as ‘epithelial folds, undetachable’ by Ev. Marcus (1983: 181), which are the characteristics of the cuticular folds of Tritoniinae . Similarly, Odhner (1963) defined Paratritonia as having an undifferentiated first lateral tooth, which is not found in the description of Baba (1949). Other features of Paratritonia include an entire oral veil and denticulate outermost lateral teeth ( Baba 1949). Once molecular data on P. lutea become available, its phylogenetic position within Tritoniidae will shed light on whether this is the case of a divergent species such as Tritonicula khaleesi , Tritonidoxa capensis , and Marianina rosea or a group of smaller marioniids currently assigned to Marioniopsis .