Marionia Vayssiere 1877
Creators: name: Silva, Felipe De Vasconcelos
name: Pola, Marta
name: Cervera, Juan Lucas
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Nudibranchia
Tritoniidae
Marionia

description: Genus Marionia Vayssière 1877 (Figs 3J, 4G, 5G, 6G)
Duvaucelia Risso 1826, Paris, Levrault, 4: 38.
Type species: Marionia blainvillea Risso 1818 (= Marionia berghii Vayssière 1879), by subsequent designation by Vayssière (1879).
Diagnosis: Rachidian tooth tricuspid, smooth. Masticatory border denticulate, denticles sharp, triangular or rounded. Digestive system arrangement cladohepatic, U- or G-shaped.
Morphology: Body slender or broad, length up to 200 mm (Fig. 3J). Oral veil bilobed. Four to 18 simple or branched velar processes, with the outermost ones oħen longer. Five to 16 pairs of arborescent gills. Rachidian tooth tricuspid and smooth (Fig. 4G). Masticatory borders of the jaws denticulate, with medium-sized (up to 50 µm) denticles with sharp cusps and conical or triangular bases. ODG complex cladohepatic, with the stomach located in the upper region of the posterior ODG complex (Fig. 5G). Penis flagelliform (Fig. 6G), cylindrical or conical.
Species composition: Marionia abrahamorum, Marionia blainvillea, Marionia cucullata Couthouy 1852, Marionia chloanthes Bergh 1902, Marionia echinomuriceae Jensen 1994, Marionia ghanensis Edmunds and Carmona 2017, Marionia gemmii, Marionia kinoi, Marionia limceana, Marionia pellucida Eliot 1904, Marionia pusa Er. Marcus and Ev. Marcus 1968, Marionia vanira Ev. Marcus and Er. Marcus 1966 and the new species Marionia flani Silva et al. sp. nov. (see description below).
Remarks: The morphological synapomorphies of Marionia within Marioniinae are the smooth tricuspid rachidian tooth (Fig. 4G), sharp and triangular or rounded denticles in the masticatory border and a unique arrangement of the cladohepatic digestive system: the stomach and intestine are located above the upper region of the posterior ODG complex, and the entire arrangement is in the shape of a ‘U’ or ‘G’ (Fig. 5G).
According to our phylogenetic analyses, Marionia consists of two clades with different geographical compositions: one clade includes the Pacific Marionia kinoi and several Atlantic species, including the type species Marionia blainvillea, whereas the other is comprised of the Atlantic Marionia limceana and many unnamed Pacific species (Fig. 2). The inclusion of Marionia cucullata in the genus is based on a recent phylogenetic hypothesis that shows the species grouped with Marionia blainvillea (Moles et al. 2021), as well as on morphological evidence that fits our proposed diagnosis: the G-shaped arrangement of the digestive system and the smooth tricuspid rachidian tooth (Odhner 1934). Species for which molecular data are not available, namely Marionia chloanthes, Marionia echinomuriceae, Marionia ghanensis, Marionia pellucida, Marionia pusa and Marionia vanira, are included in this genus on the basis of the presence of true stomach plates, the cladohepatic ODG complex and the smooth tricuspid rachidian tooth (Ev. Marcus and Er. Marcus 1966; Er. Marcus and Ev. Marcus 1968; Ev. Marcus 1983, Edmunds and Carmona 2017). Marionia gemmi is the only species of Marionia with smooth masticatory border of the jaw (Almón et al. 2018).
description: Published as part of 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), pp. 445-476 in Zoological Journal of the Linnean Society (Zool. J. Linn. Soc.) (Zool. J. Linn. Soc.) 199 (2) on page 468, DOI: 10.1093/zoolinnean/zlad013, http://zenodo.org/record/8432389