Anguipecten simoneae Morrison & Whisson, 2009
MORRISON, H. M. & C. S. WHISSON. 2009. Description of Anguipecten simoneae n.sp. from northern Western Australia (Bivalvia, Pectinidae). Conchylia, 40 (3-4): 45-51, figs. 1-22. [p. 46, figs. 2-10, 17-18]
2009 Anguipecten simoneae Morrison & Whisson, 2009
2009 Anguipecten simoneae Morrison & Whisson, 2009
H. M. Morrison & C. S. Whisson, 2009, figures 2-22.
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«Type material: Material examined: holotype and 10 paratypes.
Holotype: WAM S. 42740, Type locality: near Imperieuse Reef, southern most atoll of the Rowley Shoals, 17° 35' 42.35" - 20.75" S. 118° 58' 54.12" - 47.64" E. Taken live at 108-140 metres depth by dredging, h: 32.2 mm w: 27.8 mm, pr. (Figs: 2-9,13-16).
Paratype 1: HM 10773, near Mermaid Reef, northern most atoll of the Rowley Shoals, by commercial trawler at 100-150 metres depth, h: 30.5 mm w: 26.7 mm, dead articulated pr: (Fig: 10 a-b).
Paratype 2: WAM S. 42741, same as type locality, h: 31.7 mm w: 26.5 mm live collected pr: (Fig: 17 a-b).
Paratype 3: MNHN 22277, same locality as paratype 1, h: 33.1 mm w: 28.7 mm Iv: (Fig: 18)
Paratype 4: HD currently unnumbered, same locality as paratype 1, h: 28.1 mm w: 24.2 mm Iv: (unfigured).
Paratype 5: HM 10774, same locality as paratype 1, h: 34.2 mm w: 29.1 mm rv: (unfigured).
Paratype 6: MNT currently unnumbered, same locality as paratype 1, h: 29.3 mm w: 26.2 mm rv: (unfigured).
Paratype 7: WAM S. 43262, same locality as paratype 1, h: 28.7 mm w: 25.3 mm rv: (unfigured).
Paratype 8: HM 10775, same locality as paratype 1, h: 37.2 mm w: 31.7 mm rv: (unfigured).
Paratype 9: RGFD currently unnumbered, same locality as paratype 1, h: 29.1 mm w: 25.7 mm Iv: (unfigured).
Paratype 10: HM 10776, same locality as paratype 1, h: 33.7 mm w: 28.6 mm rv: (unfigured).
Comparative material:
Anguipecten lamberti (SOUVERBIE in SOUVERBIE & MONTROUZIER, 1874): One voucher specimen HM 7633, New Caledonia, h: 57.1 mm w: 55.1 mm Iv: (Fig: 19).
Anguipecten picturatus DUKSTRA, 1995: One voucher specimen HM 9844, Okinawa, Japan, h: 50.4 mm w: 43.5 mm pr: (Fig: 20 a-b). Twelve specimens taken by diving or dredging from Rowley Shoals WA, Indonesia, Philippines, Gulf of Thailand (Malaysia) and Japan.
Anguipecten lamberti form gregoryi (SOUVERBIE in SOUVERBIE & MONTROUZIER, 1874): One voucher specimen HM 7549, Oahu, Hawaii, USA, h: 47.3 mm w: 45.6 mm pr: (Fig: 21 a-b).
Anguipecten superbus (G. B. SOWERBY 11, 1842): One voucher specimen HM 9963, Tanimbar, Indonesia, h: 55.4 mm w: 53.6 mm pr: (Fig: 22 a-b). Fourteen specimens taken by diving or dredging from Ashmore Reef WA, Cartier Island WA, Indonesia, Philippines and Papua New Guinea.
Type locality: Australia, Western Australia, near Imperieuse Reef, southernmost atoll of the Rowley Shoals, taken at 108-140 metres depth by dredging.
Latitude 17° 35' 42.35" S - 118° 58' 54.12" E to 17° 35' 20.75"S –118° 58' 47.64" E.
Distribution: To date, Anguipecten simoneae n. sp. is only known from the Rowley Shoals, a group of three atolls lying in a north-easterly to south-westerly direction over a distance of 120 km. All three atolls rise steeply from ocean floor depths of 230 metres (Imperieuse Reef) to 440 metres (Mermaid Reef), creating a narrow depth zone in which A. simoneae n. sp. has been found. It is possible that A. simoneae n. sp. occupies the same bathymetric range throughout the Rowley Shoals atolls, as all three are geologically similar and offer very similar habitats.
Habitat: All known specimens of Anguipecten simoneae n. sp. were taken by either scientific dredging or commercial trawling. Information from the type locality suggests a habitat of coarse sand, shell grit and fine rubble over a bathymetric range of 100-150 metres.
The senior author has found Anguipecten superbus and A. picturatus under rocks or coral slabs in clean sandy conditions, while A. lamberti was observed "flapping wildly when large slabs were overturned at 240 ft depth on a sandy bottom" (JOHN EARLE, pers. comm.). It is probable that Anguipecten simoneae n. sp. also lives under small rocks and rubble, as the live collected specimens were remarkably free of encrustations.
Description of the shell: Shell small for the genus, up to 37 mm high, solid, compressed, oblong, nearly equivalve and equilateral, right valve slightly more convex than left valve, auricles long and subequal, umbonal angle 75°. Both valves radially sculptured with eight prominent lirae with the addition ofprominent ridges laterally. Lirae significantly narrower than interstices (approx. 1: 1.5 on central part of disc). Secondary radial sculpture of almost obsolete riblets on lirae with smooth interstices give undulating appearance with more prominent small riblets appearing only on ribs and interstices near central margin (approx. 7 per lira, 5 per interstice). Right valve as above, though with weaker sculpture. Microsculpture consists of delicate and closely spaced commarginal lamellae, extending over most of the disc (25-30 per mm in the central part), but becoming obsolete near ventral margin. Anterior auricles sculptured with 5-6 distinct radial riblets, posterior auricles lacking radial riblets but showing 2-3 prominent folds. Inner surface plicated, more so peripherally with small elongate nodules demarcating the plicae and extending to 5-6 distinct nodules on the anterior and posterior margin. Resilifer triangular. Byssal notch distinct, fasciole weakly developed. Ctenolium present, active but vestigial. Single cardinal rather broad crus, very close to dorsal margin. External colour ofleft valve predominantly cream with interrupted angular bands of orange to orange-red, becoming darker towards the margins. Right valve as above but paler. Internally showing external colours with faint patch of yellow near umbo.
Discussion: The tribe Decatopectinini was established by WALLER (1986) to encompass 10 extant genera exhibiting early beak inflation, very closely spaced cornrnarginal lamellae and very weak or absent resilial hinge teeth. Within this tribe, the genus Anguipecten DALL, BARTSCH & REHDER, 1938 is generally characterised by an elongate form and more numerous, finer ribs (NEWELL, 1969). The small subequal auricles, lack of ctenolium and byssal notch further help to define this small genus. The description of Anguipecten pacificus DIJKSTRA, 2002 broadened the interpretation of the genus to include specimens with a low rib count and an undulating sculpture. DUKSTRA further expanded the definition of the species by including four specimens from the Kai Islands (Indonesia) in the description of A. pacificus. These specimens clearly exhibit a distinct byssal notch and prominent auricles. They also show a vestigial, active ctenolium (VIRGINIE HÉROS, pers. comment), (see Fig: 11a-b). These four specimens were not included in the type series but in all other aspects of the final publication. DIJKSTRA & KASTORO (1997) had originally assigned these Indonesian specimens to Anguipecten picturatus DIJKSTRA, 1995 but DIJKSTRA subsequently included them with A. pacificus. These specimens however show a marked similarity to the new species A. simoneae n. sp. The one feature that all members ofthe genus Anguipecten clearly exhibit is the fine commarginal lamellae, which in the case of A. simoneae n. sp. number 25-30 per mm in the central part of the disc (see Fig. 13).
The placement of Anguipecten simonae n. sp. within the genus Anguipecten currently appears most appropriate.
Comparison: Anguipecten simonae n. sp. is conchologically the most extreme species within the genus and is immediately separable from all other congeners. Its small size (holotype h: 32 mm, largest paratype h: 37 mm), low rib count (8-9), distinct byssal notch and vestigial ctenolium separate A. simonae n. sp. from A. superbus, which has 18-32 radiallirae (DIJKSTRA, 2002) and is generally much larger (50-60 mm, RAINES & POPPE, 2006). A. lamberti also has a high rib count (approx. 30 ribs) and is much larger (h: 40-50 mm, see Figs. 19, 21a-b). A. picturatus differs from A. simonae n. sp. in size (h: 40-50 mm), brighter colour, number of radial lirae (12-15) and a coarse secondary radial sculpture (see Fig. 20a-b).
A. pacificus is distinct in having 6-7 undulating radial lirae, large size (h: 40-60 mm), no byssal notch and no evidence of a ctenolium and a much coarser microsculpture (C. 8-10 per mm in the central part; DIJKSTRA, 2002). The only group of specimens which can be confused with A. simonae n. sp. are the Kai Islands specimens. At first glance these four valves appear to have features of both A. simonae n. sp. and A. pacificus, i. e. the low undulating broad radial lirae of A. pacificus combined with the large rounded auricles and distinct byssal notch of A. simonae n. sp. (see Figs: 10-12). Their size and general colouring are also more like those of A. simonae n. sp. than of A. pacificus. It is possible that further material from Indonesia may place the problematic group of Indonesian specimens either with A. simonae n. sp. or they become the basis for a separate species. If subsequent research shows the Kai Islands specimens to be a separate species, it would appear that there might be sufficient grounds for separating A. simoneae n. sp. and the Kai Islands material from other members of the genus Anguipecten at the generic level, based on low rib count, prominent auricles and active ctenolia in their adult shells.
Etymology: This species is named in honour of Ms. SIMONE PFUETZNER of Kingsley, Australia who has been a constant and much loved companion of the senior author and who has continually contributed to the world of conchology. Her drive for thoroughness and accuracy in all things is an inspiration.»
HUGH M. MORRISON & COREY S. WHISSON, 2009
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«Description. Shell up to 37 mm high; solid, compressed, oblong, somewhat triangularly elongate, left valve almost flat, right valve slightly more convex than left valve, nearly equivalve and equilateral, anterior auricles somewhat larger in size and shape than posterior auricles, umbonal angle c. 75°; cream with interrupted angular bands of orange to orange-red, right valve paler.
Both valves sculptured with 8 primary radial plicae, and a few weaker plicae laterally. Plicae narrower than interstices dorsally, widening down disc to equal width of interspaces ventrally. Secondary radial sculpture of obsolete radial riblets on plicae and in interstices. Sculpture of right valve somewhat weaker than left. Microsculpture of closely spaced commarginal lamellae. Anterior auricles sculptured with 5–6 distinct radial riblets, posterior auricles with 3–4 weaker radial riblets and 2–3 prominent folds. Dorsal margin straight, somewhat raised on right valve. Inner surface plicated, short internal rib carinae present near margin. Adductor scar insertion prominent. Resilifer narrowly triangular, resilial teeth weak, intermediate teeth strongly developed. Byssal notch distinct, byssal fasciole weak; functional ctenolium rudimentary, with 3–4 teeth. Dimensions. Illustrated paratype: 100–150 m, off Mermaid Reef, Rowley Shoals, WA (HM10773): H 30.5, L 26.8 mm.
Habitat. Living on the outer continental shelf, probably on coarse sand, shell grit and fine rubble, similar to the other species of Anguipecten.
Distribution. So far only known from the Rowley Shoals off northern Western Australia. Present material alive at 108–140 m. Specimens from the Kai Islands, Indonesia, possibly also belong here (see below).
Remarks. The present species is morphologically close to Anguipecten pacificus Dijkstra, 2002, known from the Marquesas Islands, French Polynesia, but differs in size (A. simoneae up to 37 mm in height, A. pacificus up to 60 mm), in having more numerous radial plicae (A. simoneae 8, A. pacificus 6–7), and in having a byssal notch, byssal fasciole and active ctenolium, features that are lacking in adult specimens of A. pacificus.
Dijkstra (2002: 139–140) identified four specimens from the Kai Islands, eastern Indonesia (Morrison & Whisson, 2009: 48, fig. 11a–b, as Anguipecten sp.) as atypical specimens of A. pacificus. In fact these specimens are closer to Anguipecten simoneae than to A. pacificus and provisionally are determined as A. simoneae. DIJKSTRA, H. H. & A. G. BEU. 2018. Living scallops of Australia and adjacent waters (Mollusca: Bivalvia: Pectinoidea: Propeamussiidae, Cyclochlamydidae and Pectinidae). Records of the Australian Museum, 70 (2): 113-330, figs. 1-102. [p. 178, 179]
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Anguipecten simoneae Morrison & Whisson; H. H. Dijkstra & A. G. Beu, 2018, Living scallops of australia and adjacent waters, figures 29I, 29J, 31G, 31H.
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