Navanax, COOPER, 1862

Zamora-Silva, Andrea & Malaquias, Manuel António E., 2018, Molecular phylogeny of the Aglajidae head-shield sea slugs (Heterobranchia: Cephalaspidea): new evolutionary lineages revealed and proposal of a new classification, Zoological Journal of the Linnean Society 183, pp. 1-51 : 44-46

THE GENUS NAVANAX COOPER, 1862

Navanax was regarded by Bergh (1905) and Marcus & Marcus (1970) to be a synonym of Chelidonura because of similar morphological traits such as the presence of an elongated head shield, cephalic sense organs with mounds containing sensory bristles, backward extensions of the posterior shield, well-developed parapodial lobes and a racemose prostate in both genera. Rudman (1974) presumed Navanax to be a synonym of Aglaja because of resemblances between their shells, buccal bulbs and female glands. Gosliner (1980) reinstated the genus as valid based on distinct characteristics of the cephalic shield (well-developed antero-lateral portions extended as semi-circular funnels) and male genitalia (conical and convoluted penial papilla and fused bilobed prostate). The monophyly of Navanax has received support in some recent molecular phylogenetic studies (e.g. Camacho-García et al., 2014; Oskars et al., 2015), and the genus, including the type species N. inermis , received maximum support in the current study ( Fig. 2A, B).

PHILINOPSIS PEASE, 1860 , SPINOAGLAJA ORTEA, MORO & ESPINOSA, 2007 , AND THE NEW GENERA

SPINOPHALLUS AND TUBULOPHILINOPSIS

The possible non-monophyly of the genus Philinopsis was previously suggested by some molecular phylogenetic studies. Anthes & Michiels (2007) including eight species of Philinopsis found the genus to split into two sub-clades, which the authors named the ‘ taronga ’ and ‘ pilsbryi ’ groups. Later, Camacho-García et al. (2014) recovered a hypothesis where all species, but one ( P. falciphallus ) clustered together with moderate to high support in Bayesian analyses (PP = 0.92, 0.96), yet with no support in ML analyses (BS = <50, 65). Moreover, P. falciphallus nested within a ‘superclade’ containing representatives of the genera Aglaja , Chelidonura and Navanax (sub-clade A 2 in Camacho-García et al., 2014).

Our analyses did not obtain statistical support for the monophyly of Philinopsis (PP/BS = 0.71/42; Fig. 2A, B). Instead, we have obtained four well-supported sub-clades for which it is possible to establish synapomorphies. One of these clades corresponds to Philinopsis s.s., another is consistent with the genus Spinoaglaja ( Ortea et al., 2007) , and for the last two clades, no names were available. Therefore, we here propose two new genera Spinophallus and Tubulophilinopsis (see Systematic results section).

Philinopsis s.s. (PP/BS = 1/97) with type species P. speciosa includes species distributed in WA and IWP ( Table 4). This genus is defined by the presence of a convex-concealed shell ( Fig. 5E), wide and rectangular body, flat cephalic shield, two slightly squared anterior lobes with the posterior flap raised into a peak on the midline, and symmetrical caudal lobes, poorly developed enclosing the posterior end of the mantle cavity ( Pease, 1860; Rudman, 1968; Gosliner, 1980, 2011, 2015; Fig. 3L).

The new clade Spinophallus (PP/BS = 0.97/98), consistent with the ‘ taronga group ’ of Anthes & Michiels (2007), with type species S. coronata Gosliner, 2011 ( Figs 2A, B, 3M; Supporting Information, Figs S1–S 4) is restricted to the IWP, and it is characterized by an elongated and wide body, quadrangular and blunt cephalic shield with a bulbous dorsal projection on its posterior end, symmetrical and inconspicuous caudal lobes, and conical spines on the penial papilla or in the penial sac (see Gosliner, 2015: 3, fig. 1 for images of this bulbous projection).

The next new clade, Tubulophilinopsis (PP/ BS = 1/97; Figs 1, 2; type species T. pilsbryi ), corresponds to the ‘ pilsbryi group ’ of Anthes & Michiels (2007) and was also obtained by Camacho-García et al. (2014) (see Systematic results section for a synopsis of this genus). Animals of this genus share the presence of a pentagonal cephalic shield with an elevated hump containing the frontal eyes inserted in unpigmented periocular areas ( Figs 3O, 4; Imamoto, 2003; Berberain & Michenet, 2015), three different types of shell ( Table 5) and a slim and long tubular buccal bulb ( Rudman, 1972a, 1974).

The genus Spinoaglaja (type species S. petra ) was erected by Ortea et al. (2007) based on the unique presence of spines on the apex of the shell. Camacho-García et al. (2014) did not regard the genus valid and re-ascribed ‘ petra ’ to the genus Philinopsis . Our results showed that all species of ‘ Philinopsis ’ with shell-bearing spines ( Figs 5K, 6E) form a clade with high support (PP/BS = 0.97/100; Fig. 2A, B). The external morphology of Spinoaglaja is similar to Tubulophilinopsis , but its particular shell morphology is autapomorphic, and therefore, we here resurrect the genus name Spinoaglaja for the WA species S. aeci ( Romani & Pagli, 2015) , S. petra ( Fig. 3N; Ortea et al., 2007) and the IWP S. orientalis ( Figs 2A, B, 6E).