Basic anatomy of species of Triphoridae (Gastropoda, Triphoroidea) from Brazil Author Fernandes, Maurício Romulo Author Pimenta, Alexandre Dias text European Journal of Taxonomy 2019 2019-04-17 517 1 60 journal article 26998 10.5852/ejt.2019.517 d05987e2-6008-4deb-9773-1d988013beba 2647891 CAC6F8AF-ED37-4989-9672-68316920750B Metaxia excelsa Faber & Moolenbeek, 1991 Figs 2A , 3 Material examined BRAZIL • [2, 1 d] specs; Fernando de Noronha Archipelago , canal between islands Ressureta and Rata ; 03°48′55″ S , 32°23′31″ W ; 12 m depth; 10 Aug. 2012 ; G.H. Pereira Filho leg.; MZSP 122353 . Description of basic anatomy OPERCULUM. Elliptical, thin, semi-transparent, membranous, nucleus and number of whorls not discernible; diameter of operculum exceeds diameter of opercular pouch in 17%. JAW. Wing-shaped; outer side with scales usually rectangular/squared, sometimes rhombus-shaped or even oblong-lanceolate; some scales covered by micro-pores up to 270 nm in diameter; rectangular scales 10.5–15.4 µm long, 4.8–7.7 µm wide, ratio length/width 1.8–2.9, rhombus-shaped scales 17.9– 24.5 µm long, 5.9–10.0 µm wide, ratio length/width 2.4–3.1, oblong-lanceolate scales 14.6–16.5 µm long, 4.0–5.0 µm wide, ratio length/width 2.9–3.6. RADULA. Formula 4-1-1-1-4; central tooth with four to five elongated and claw-like cusps, median cusp present or not but always thinner, with the basal plate of tooth assuming a concave format (i.e., outer cusps in an upper position than median one), outer cusps usually distinctly oriented outwards and reaching slightly larger dimensions (equal or up to 1.2× more elongated) than inner cusps; lateral teeth with four elongated claw-like cusps, basal plate of tooth slightly concave (not as much as central tooth), all cusps approximately with the same length, but cusp 1 considerably broader and sometimes slightly shorter than remaining cusps; marginal teeth gradually diminishing in size outwards; M1 and M2 with four cusps very similar to lateral teeth, with all cusps similar in length or width; M3 with three similar, moderately elongated, pointed and claw-like cusps; M4 small, with three curved and pointed cusps, median one 1.2 to 1.6 times more elongated than remaining cusps; central tooth 6.4–9.2 µm wide, lateral teeth 7.1–9.9 µm wide, M1 5.8–8.7 µm wide, M2 4.1–6.7 µm wide, M3 3.2–4.4 µm wide, M4 2.3–3.1 µm wide. Fig. 2. Specimens studied. A . Metaxia excelsa Faber & Moolenbeek, 1991 (MZSP 122353). B . Metaxia rugulosa (C.B. Adams, 1850) (BMSM 56034). C . Cosmotriphora melanura (C.B. Adams, 1850) (MNRJ 33980). D . Iniforis pseudothomae Rolán & Fernández-Garcés, 1993 (MZSP 100957). E . Latitriphora albida (A. Adams, 1854) (BMSM 55442). F . Monophorus olivaceus (Dall, 1889) (MNRJ 34615). G . Nanaphora verbernei (Moolenbeek & Faber, 1989) (MZSP 85022). H . Nototriphora decorata (C.B. Adams, 1850) (MNRJ 28941). I . Sagenotriphora osclausum (Rolán & Fernández-Garcés, 1995) (MNRJ 35061). J . Similiphora intermedia (C.B. Adams, 1850) (MNRJ 29763). K . Strobiligera gaesona (Dall, 1927) (MZSP 53685). L . “ Inella ” harryleei Rolán & Fernández-Garcés, 2008 (FLMNH 450495). Scale bars: 1 mm. Fig. 3. Metaxia excelsa Faber & Moolenbeek, 1991 . A–G . MZSP 122353. A . External morphology. B–C . Jaw, outer side. D–G . Radula. Scale bars: A = 1 mm; B = 50 µm; C = 2 µm; D–F = 10 µm; G = 5 µm. Remarks The radula of M . excelsa shares several features with that of M . exaltata (Powell, 1930) ( Marshall 1977 ) , such as the general tooth morphology and the gradual decrease of size towards the outermost marginal teeth, confirming their affinity at genus-level. The distinction lies in the number of marginal teeth (only four in M . excelsa , but nine or ten in M . exaltata ), the median cusp of the central tooth (apparently more reduced or vestigial in M . exaltata ) and the number of cusps in the outermost marginal teeth (three in M4 of M . excelsa , two in M9 or M10 of M . exaltata ). The radula of M . metaxa described by Bouchet (1985) shows slight differences compared to M . excelsa , like a central tooth with four cusps (instead of five in M . excelsa ), lateral teeth and M1-M2 with five cusps (four in M . excelsa ) and the presence of five marginal teeth (four in M . excelsa ). Radulae of both species are similar in general tooth morphology, with claw-like cusps, and in the number of cusps of the outermost marginal teeth (i.e., three cusps). The tooth morphology of M . excelsa is also quite similar to the two unnamed species from the southwestern Pacific studied by Nützel (1998) , especially to Metaxia sp. 1, albeit these two species have six and five marginal teeth (but four in M . excelsa ). The predominance of rectangular scales in the jaw of Metaxia sp. 1 looks identical to the observed in M . excelsa ( Fig. 3B ).