Range Extension of Pseudotorinia Phorcysi (Gastropoda: Architectonicidae) from the SW Atlantic, with Remarks on Its Ontogeny
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Zootaxa 4175 (5): 491–493 ISSN 1175-5326 (print edition) http://www.mapress.com/j/zt/ Correspondence ZOOTAXA Copyright © 2016 Magnolia Press ISSN 1175-5334 (online edition) http://doi.org/10.11646/zootaxa.4175.5.8 http://zoobank.org/urn:lsid:zoobank.org:pub:E17C0963-12CA-4DB8-AFA2-0581FFFDA836 Range extension of Pseudotorinia phorcysi (Gastropoda: Architectonicidae) from the SW Atlantic, with remarks on its ontogeny DANIEL C. CAVALLARI1,* & RODRIGO B. SALVADOR2, 3 1Museu de Zoologia da Universidade de São Paulo. São Paulo, SP, Brazil 2Staatliches Museum für Naturkunde Stuttgart. Stuttgart, Baden-Württemberg, Germany 3Eberhard Karls Universität Tübingen. Tübingen, Baden-Württemberg, Germany 4Corresponding author: E-mail: [email protected] Architectonicidae is a diverse family of heterobranch sea snails comprising over 11 genera and 140 extant species distributed worldwide (Bieler & Petit, 2005). They live in shallow to deep water, and have turbinate to discoidal shells, with a typically wide umbilicus and a downward-pointing (heterostrophic) protoconch (Healy, 1998). Pseudotorinia phorcysi Cavallari, Salvador & Simone, 2013 is a deep-water species known only from its type locality in the SW Atlantic, off Cabo Frio, Rio de Janeiro state, Brazil (23°41'S 42°06'W, 430–450 m depth). Its original description was based on a single eroded juvenile specimen collected by the French-Brazilian expedition “Marion Dufresne” MD55 in the late 1980s (Cavallari et al., 2014). A recent review of the malacological collection of the Museu de Zoologia da Universidade de São Paulo (MZSP; São Paulo, Brazil) revealed a reasonably well-preserved adult specimen of P. phorcysi, collected in southern Brazilian waters. This effectively expands the species’ geographic and bathymetric ranges. The specimen studied here is an empty shell collected off Solidão, Rio Grande do Sul state, Brazil. Its older age, evidenced by a greater number of whorls and larger size, also allowed further ontogenetic observations, which are discussed below. The description of Pseudotorinia phorcysi by Cavallari and colleagues (2014) was based on a single, damaged juvenile specimen recovered by the MD55 expedition off SE Brazil in 1987 (for details on the expedition, see Tavares, 1999). Though it was not well preserved and had only 1¾ teleoconch whorls, the holotype (MNHN 26363; P = 0.59, SD = 2.69, H = 1.0, UD = 0.76, w = 0.88, h = 0.71, all in mm) presented enough characteristics for a precise generic placement and its description as a new species (Cavallari et al., 2014). The new species’ diagnostic features are: a discoid and distinctly keeled shell, with a wide umbilicus (UD ~30% of SD) and well-marked suture (Fig. 1B); the teleoconch sculpture on the upper (adapical) region of the whorls bearing two similarly strong beaded midribs; the presence of a sharp peripheral keel formed by a single very strong beaded spiral rib and a lower, weaker similarly sculptured rib, with fine axial growth lines in the depression between them. The teleoconch sculpture on the shells’ basal (abapical) region consists of 3–4 beaded spiral ribs, with coarser nodules towards the umbilicus, and the protoconch-teleoconch transition is marked by a strong terminal varix (Fig. 1B). Compared to the holotype, the specimen studied here is a considerably older and larger individual, with 3¼ teleoconch whorls (P = 0.75, SD = 5.46, H = 2.24, UD = 1.8, w = 1.67, h = 1.42, all in mm). Even though it is somewhat worn, especially on the upper side, some key elements for its safe recognition as P. phorcysi are present: the shell’s pale white color and outline; umbilical width (~ 30% of SD; Fig. 1C); well-marked suture (Fig. 1E) and the sharp peripheral keel formed by a single, strong, beaded infraperipheral rib and a weaker lower peripheral rib (Fig. 1E), with axial growth lines between them. Moreover, the protoconch-teleoconch transition is marked by a terminal varix, which is damaged but still noticeable on the specimen’s upper side (Fig. 1D) and still relatively intact basally (Fig. 1F). The apertural profile is also virtually the same (Fig. 1A, F), still remarkably similar to the example of Bieler (1993: fig. 224a, left). The coarse, angular periumbilical nodules (Fig. 1G) are strikingly similar to those of the holotype (Cavallari et al., 2014: fig. 7), which becomes especially evident when comparing apertural views of both specimens (Fig. 1A, F). Nevertheless, there are discrepancies to be noted. The protoconch is slightly larger in the present specimen (0.75 mm as opposed to 0.59 mm in the holotype). A similar degree of size variation is not uncommon among Pseudotorinia Sacco, 1892 species, however (e.g., Pseudotorinia gemmulata (Thiele, 1925); see Bieler, 1993, for several additional examples). The protoconch of the holotype was damaged and had lost its initials whorls, (Cavallari et al., 2014: fig. 9), but here it can be observed whole (Fig. 1D, G). The shell outline changes very little from young to adult specimens; still, the peripheral keel becomes slightly less prominent, and the basal region somewhat more inflated (Fig. 1F). Accepted by M. Schroedl: 9 Sept. 2016; published: 18 Oct. 2016 491 FIGURE 1. Pseudotorinia phorcysi from the SW Atlantic; A–B. Holotype MNHN 26363; A. apertural view (SD = 2.69 mm, H = 1.0 mm); B. apical view (P = 0.59). C–G. Specimen from Rio Grande do Sul MZSP 19431; C. umbilical view (SD = 5.46 mm); D. detail of protoconch, arrow indicates location of terminal varix (scale = 2 mm) E. apical view; F. apertural view (H = 2.24 mm); G. umbilical view, detail of protoconch, arrow indicates location of terminal varix (scale = 2 mm). 492 · Zootaxa 4175 (5) © 2016 Magnolia Press CAVALLARI & SALVADOR The overall shell sculpture is less prominent in the present specimen, though this can be attributed to long-term abrasion and to some elements becoming less conspicuous with age. On the upper side, the sculpture on the initial whorls is mostly similar to that of the holotype, but additional elements are present on subsequent whorls. Besides the lower and upper peripheral ribs and the subsutural rib, an additional, much narrower midrib (upper midrib) can already be seen at 1½ teleoconch whorls, followed by a lower midrib at 2½ teleoconch whorls and beyond (Fig. 1E). In fact, the beginning of the upper midrib in the very same whorl is visible in the holotype, even though Cavallari et al. (2014: fig. 8) did not emphasize this. The basal field sculpture (Fig. 1C) is more delicate, which is expected of a larger specimen, but its basic components remain the same: numerous (4–5), thinner nodulose ribs and wider (3) proxumbilical ribs with coarser, larger and less numerous nodules towards the umbilical region. The umbilical crenae is very strong, and in this specimen is clearly separated from the remaining basal field sculpture by a deep sulcus. This sulcus is itself sculptured by strong axial growth lines, and is not present in younger individuals, which can be verified in the specimens’ earliest whorls in umbilical view (Fig. 1C), and the holotype itself (Cavallari et al., 2014: fig. 6). The present specimen was collected 820 km southward and over 700 km eastward of the type locality, off Solidão, Rio Grande do Sul state. It being so far removed from the original distribution does not come as a surprise for most architectonicid species, which are known to have very wide ranges due to extended planktonic larval stages (Healy, 1998; Bieler & Petit, 2005). The present record also expands the species’ bathyal range to shallower depths, from the previously known 430-450 m to 184 m. Abbreviations: Shell measurements: SD, shell diameter; H, shell height; P, protoconch width; w, aperture width; h, aperture height, UD, umbilical diameter. Shell structures and shell measurements terminology after Bieler (1993). Institutional: MNHN = Muséum National d'Histoire Naturelle (Paris, France); MZSP = Museu de Zoologia da Universidade de São Paulo (São Paulo, Brazil). Material examined: Type specimens: Holotype: Brazil; off Rio de Janeiro state: 23°41'S, 42°06'W, 430-450 m, MNHN 26363 (MD55, sta. CB104; Bouchet, Leal & Métivier col., 01.vi.1987). Additional material: Brazil; Rio Grande do Sul state, off Solidão, 31°08'S, 49°31'W, 184 m, 1 sh, MZSP 19431 (R/V “W. Besnard” col., 06.viii.1972). Acknowledgements We are thankful to Luiz R.L. Simone (MZUSP) for bringing the specimen to the senior author’s attention, and for numerous helpful observations. References Cavallari, D.C., Salvador, R.B. & Simone, L.R.L. (2014) Taxonomical study on the Architectonicidae (Gastropoda, Heterobranchia) collected by the Marion Dufresne (MD55) expedition to SE Brazil. Spixiana, 37 (1), 35–43. Bieler, R. (1993) Architectonicidae of the Indo-Pacific (Mollusca, Gastropoda). Abhandlungen Des Naturwissenschaftlichen Vereins in Hamburg, 30, 1–376. Bieler, R. & Petit, R.E. (2005) Catalogue of Recent and fossil taxa of the family Architectonicidae Gray, 1850 (Mollusca: Gastropoda). Zootaxa, 1101, 1–119. Healy, J.M. (1998) Superfamily Architectonicoidea. In: Beesley, L.P., Ross, G.J.B. & Wells, A. (Eds.), Mollusca: the Southern Synthesis. Part B. CSIRO Publishing, Melbourne, pp. 858–862. Tavares, M. (1999) The cruise of the Marion Dufresne off the Brazilian coast: account of the scientific results and list of stations. Zoosystema, 21 (4), 597–605. DISTRIBUTION OF PSEUDOTORINIA PHORCYSI Zootaxa 4175 (5) © 2016 Magnolia Press · 493.