Dolabrifera, GRAY, 1847

Valdés, Ángel, Breslau, Eric, Padula, Vinicius, Schrödl, Michael, Camacho, Yolanda, Malaquias, Manuel António E., Alexander, Jennifer, Bottomley, Morgan, Vital, Xochitl G., Hooker, Yuri & Gosliner, Terrence M., 2018, Molecular and morphological systematics of Dolabrifera Gray, 1847 (Mollusca: Gastropoda: Heterobranchia: Aplysiomorpha), Zoological Journal of the Linnean Society 184, pp. 31-65 : 37-38

GENUS DOLABRIFERA GRAY, 1847

Dolabrifera Gray, 1847: 162 . Type species: Dolabrifera dolabrifera ( Rang, 1828) , by original designation.

Diagnosis: Body oval to elongate, wider posteriorly, narrowing gradually towards head. Oral tentacles, rhinophores slit, flattened, wider distally. Oral tentacles emerging anteriorly from the head, clearly differentiated. Rhinophores dorsal, typically smooth. Parapodial lobes reduced, located behind body midline, fused posteriorly, overlapping partially in middle. Dorsum typically covered with tubercles of different sizes. Shell solid, calcified, reduced, flat, elongate, subtriangular, wider posteriorly, tapering anteriorly into a conspicuous nucleus. Jaws reduced to small section of the labial cuticle with simple denticles. Radula with large, subtriangular rachidian teeth, with several denticles on each side of the cusp; lateral teeth with long, coarsely denticulate cusps. The posterior end of buccal bulb, at insertion of the oesophagus, with two elongate structures (post-radular armature), of numerous elongate denticles. Gizzard muscular, with numerous irregular plates. Male reproductive system with distinct penial canal and penial sheath, where penial papilla is typically located.

Remarks: Since its original introduction by Gray (1847), several nominal species have been described in or transferred to Dolabrifera , many of them based on shell material or preserved specimens. Nearly all of those species were confirmed to be members of Dolabrifera , but later synonymized with D. dolabrifera (see Engel & Hummelinck, 1936; Eales, 1944) or D. brazieri (see Hedley, 1917). However, the taxonomic assignment of two of those species is questionable. The first one, Dolabrifera holboelli Bergh, 1872 , was described from a single specimen collected in ‘Mare grönland’ (= Greenland Sea). Bergh (1872: pl. 5, figs 1–24) provided illustrations of the preserved animal, shell, radula, jaw, gill and other anatomical details (some of them reproduced in Supporting Information, Fig. S2S–U). All descriptions are consistent with the characteristics of a member of Dolabrifera , and examination of the holotype (ZMUC GAS-2163) confirms the generic placement of this species in Dolabrifera . However, there are no confirmed reports of Dolabrifera from Greenland, nor from other temperate or cold-water regions in the North Atlantic; thus, the most likely explanation for this record is that the specimen was mislabelled. Based on the radular and shell morphology, D. holboelli resembles the tropical Indo-Pacific species D. dolabrifera because the lateral teeth have bifurcated apices with two equally large denticles, and the shell widens abruptly near the apical end, but none of these traits are conclusive. In the absence of molecular data or information on the geographical origin of the holotype, D. holboelli is here treated as an uncertain species. The second problematic species, Dolabrifera pelsartensis O’Donoghue, 1924 , was described from ‘Pelsart Island’ (Pelsaert Island), Western Australia, based on two preserved specimens. O’Donoghue (1924: pl. 27, fig. 3, pl. 29, figs 26–28) illustrated a preserved animal (Supporting Information, Fig. S2R) and a radula, which shows mid-lateral teeth with two to three denticles and simple cusps. No illustrations of the shell or other anatomical features were provided. With the available information, it is difficult to compare D. pelsartensis with the species here described. The radular morphology is most similar to that of D. brazieri , which appears to be endemic to temperate Eastern Australia and New Zealand. Examination of material from Western Australia is necessary to clarify the status of this species.

Another species, Dolabrifera triangularis Watson, 1884 , has almost certainly been erroneously assigned to Dolabrifera . Watson (1884) described D. triangularis based on a shell collected from Simon’s Bay, South Africa. Although Watson (1884) described the shell in detail, provided no illustrations and the live animal is unknown. Years later, Watson (1886: 673–674, pl. 50, fig. 7; Supporting Information, Fig. S2V, W) redescribed and illustrated this shell, which is nearly triangular, short, with a large nucleus. The only remaining syntype (NHMUK 1887.2.9.2296) here examined, matches this description, but is much shorter and thicker that other shells of Dolabrifera spp. In addition, no specimens of Dolabrifera have been documented in False Bay and surrounding areas despite the comprehensive studies ( Gosliner, 1987; Zsilavecz, 2007). Based on the available evidence, we cannot identify D. triangularis and therefore is here regarded as a nomen dubium.