Hanleya mediterranea Sirenko 2014, sp. nov.
Creators: name: Sirenko, Boris
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Polyplacophora
Lepidopleurida
Hanleyidae
Hanleya
Hanleya mediterranea

description: Hanleya mediterranea sp. nov.
(Figures 6–8A–J)
Hanleya hanleyi – Dell’ Angelo, Lombardi and Taviani, 1998:244, Pl. 2, Figures 1–2 (not H. hanleyi Bean in Thorpe, 1844), Dell’ Angelo and Smriglio, 2001: 85, Pl. 25, E–H, Pl. 26, L–P (partim, non H. hanleyi Bean in Thorpe, 1844).
(Continued)
Hanleya multigranosa – Sabelli and Taviani, 1979: 161, Figure 4 (non Chiton multigranosus Reuss, 1860).
Type material
Holotype, ZISP 2201, BL = 4.7 mm, now disarticulated, consisting of mounts of shell, perinotum and radula, and three paratypes, ZISP 2202.
Type locality
Mediterranean Sea, off Begur, Girona, Spain, in 200–300 m.
Material examined
Holotype and three paratypes, ZISP 2202, BL = 4.0– 4.7 mm, Mediterranean Sea, off Prinkipo, Turkey, 40.5139° N, 29.0724° E, in 50 m.
Distribution
Mediterranean Sea off Spain and Turkey, in 50–200 m.
Diagnosis
Animal very small, to 4.7 mm long, elevated (dorsal elevation 0.37) subcarinate, valves beaked; anterior margin of intermediate valves splayed laterally, with large inward curve in jugal area. Several granules of tegmentum in pleural areas joined, each granule with single megalaesthete and 9–16 micraesthetes; girdle covered dorsally with long, pointed scales that are smooth or with one central rib, as well as with numerous long needles. Insertion plates well developed both in head and tail valves.
Description
Holotype small, BL = 4.7 mm. Valves subcarinated, beaked (Figure 6D), shell and girdle white. Head valve semicircular, posterior margin wide, V-shaped, notched in the middle, tegmentum sculptured with roundish granules (diameter 70–80 µm), arranged without pattern (Figure 6A). Intermediate valves trapeziform, anterior margin greatly splayed laterally, with large inward curve in jugal area, posterior margin with small beak, lateral areas sculptured like head valve with rare round granules, jugal area sculptured with oval granules (about 80 × 50 µm) arranged without interspaces or pattern (Figure 6B). Pleural areas sculptured with oval granules (120 × 70 µm) arranged without pattern, several granules join to form larger granules (up to 220 × 160 µm) (Figures 6E and 8I, J). Intermediate valves VI and VII have indistinct, short, longitudinal rows of granules in pleural areas near their posterior margin that are interrupted by large, joined granules in other part of pleural area. Each granule contains one megalaesthete surrounded by 9–16 micraesthetes (Figure 8I). Tail valve narrower than head valve, more or less oval, mucro submedian, clearly indicated, postmucronal slope decidedly concave directly behind mucro, straightening near the posterior margin, antemucronal area sculptured like central area of intermediate valves, postmucronal area like head valve (Figure 6C and F).
Articulamentum strongly developed, insertion plates only on head valve 1/5 the length of the valve, apophyses wide, oriented laterally, connected to primordium of insertion plates in intermediate valves; insertion plates obsoletely striate in head and tail valves (Figure 6G).
Girdle narrow, 1/4 width of intermediate valve, covered dorsally with long pointed scales that may be smooth or with one central rib (50–86 × 23 µm) and numerous long smooth needles (330–550 × 24 µm). Marginal and dorsal needles similar. Ventral scales (50–55 × 18 µm) smooth typically, shorter than dorsal scales (Figures 7A, B, C, and 8C–E).
Radula 2.2 mm long, with 28 transverse rows of mature teeth (total about 34 transverse rows). Central tooth short, nearly rectangular, with narrow blade; major lateral tooth with tridentate cusp, central denticle largest, exterior and interior cusps approximately equal (Figures 7D and 8F–H).
Gills merobranchial, adanal, without interspaces, five ctenidia on each side, gills extending from valve VII to anus.
Etymology
From the Mediterranean Sea, where this species was found.
Comparative remarks (Table 1)
Hanleya mediterranea is distinguished from other species in the genus, including H. hanleyi, by its lack of longitudinal rows of granules across the entire pleural area, and by the presence of large granules comprising two or more small granules in pleural areas.
Small specimens of Hanleya nagelfar, which have a similar radula, differ from H. mediterranea by having dorsal spicules that are oval in transverse section, with six perceptible ribs. In H. mediterranea (BL = 4.7 mm) the head valve has more strongly developed insertion plates that are 16–20% the length of the valve, compared with H. nagelfar, (BL = 5–7 mm), in which the insertion plates are 3–9% the length of the head valve.
Hanleya tropicalis differs from H. mediterranea in having carinated valves, in lacking an insertion plate in the tail valve, and by having a smaller exterior denticle on the major lateral teeth of the radula (Figure 8H and K).
Hanleya harasewychi has similar dorsal scales on the girdle, but differs from H. mediterranea by having rounded valves, in the colour of the shell and girdle, by having longer granules on pleural areas of intermediate valves, as well by their arrangement, by a wider jugal sinus, a well-developed and pectinate insertion plate in the tail valve, and by a lower number of mineralised transverse rows of radular teeth as well as in the shape of the head of the major lateral teeth.
Hanleya brachyplax has a similar radula, but differs from H. mediterranea in being less elevated, having a well-developed insertion plate in its tail valve, and by its larger size.
Hanleya multigranosa (Reuss, 1860) from Middle Miocene deposits of Bohemia differs from the new species in having a shorter insertion plate on the head valve, a differently shaped tail valve, and smaller and more numerous granules on the tail valve. A single Pleistocene intermediate valve from Parma, Italy, which was identified as H. multigranosa by Sabelli and Taviani (1979: Table 1, Figure 4) most likely belongs to H. mediterranea. The records of fossil Hanleya from the Miocene of Poland, reported as H. multigranosa by Sulc (1934) and from the Upper Miocene of Italy, reported as H. hanleyi by Dell’ Angelo et al. (1999) should be confirmed by comparison of these fossil specimens with the new species described herein. Hanleya glimmerodensis Janssen, 1978 from the Upper Oligocene of western Germany differs from H. mediterranea in having well-marked longitudinal rows of granules on pleural areas of intermediate valves.
Several publications report Hanleya hanleyi as occurring in the Mediterranean Sea (Monterosato 1879; Malatesta 1962; Sabelli 1972, 1974; Dell’ Angelo et al. 2004 and references in Dell’ Angelo and Smriglio 2001). Among these studies, Sabelli (1972) reported this species to reach a body length of 9 mm, and occur at depths ranging from 35–40 m to 140 m. Sabelli (1974) reported a body length of about 10 mm, while Dell’ Angelo and Smriglio (2001) reported a maximum body length of about 13 mm. Dell’ Angelo (personal communication) informed me that he has several specimens of Hanleya hanleyi collected in the Mediterranean Sea (BL <7 mm), from depths of 40–120 m and single valves dredged at depths up to 400 m in his collection. Dell’ Angelo and Smriglio (2001: pl. 25 C, Figure 36) included several photographs of chitons that have longitudinal rows of granules on central areas of intermediate valves. Although more than one species of Hanleya may inhabit the Mediterranean Sea, I provisionally attribute the above-mentioned records to H. mediterranea.
Although the validity of Hanleya tropicalis and H. brachyplax is not in doubt, the relationship between H. hanleyi and H. nagelfar has been questioned. It is very difficult to distinguish small specimens of H. nagelfar from H. hanleyi because they both have a very similar sculpture of the tegmentum (Waren and Klitgaard 1991). As noted in the introduction, the discussion about differences between H. nagelfar and H. hanleyi has continued since the description of H. nagelfar. The relationship between H. hanleyi and H. nagelfar is further explored by a study of age variability in H. nagelfar.
description: Published as part of Sirenko, Boris, 2014, Composition of the genus Hanleya (Mollusca: Polyplacophora: Lepidopleurida), with the description of two new species, pp. 2913-2945 in Journal of Natural History 48 (45 - 48) on pages 2923-2931, DOI: 10.1080/00222933.2014.963722, http://zenodo.org/record/4631535