Peronia willani Dayrat & Goulding, 2020

Dayrat, Benoit, Goulding, Tricia C., Apte, Deepak, Aslam, Sadar, Bourke, Adam, Comendador, Joseph, Khalil, Munawar, Ngo, Xuan Qu ảng, Tan, Siong Kiat & Tan, Shau Hwai, 2020, Systematic revision of the genus Peronia Fleming, 1822 (Gastropoda, Euthyneura, Pulmonata, Onchidiidae), ZooKeys 972, pp. 1-224 : 1

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Peronia willani Dayrat & Goulding

sp. nov.

Peronia willani Dayrat & Goulding sp. nov. Figs 59 View Figure 59 , 60 View Figure 60 , 61 View Figure 61 , 62 View Figure 62 , 63 View Figure 63 , 64 View Figure 64

Type material.

Holotype. Australia • holotype, hereby designated, 50/35 mm [1628 H]; Northern Territory, Darwin, Talc Head; 12°28.765'S, 130°46.297'E; 15 Aug 2012; B Dayrat and field party leg.; station 62, large and open forest of Sonneratia alba with soft mud; NTM P.57625.

Additional material examined.

Australia • 4 specimens 65/45 mm [1620], 18/14 mm [1653], 60/50 mm [1654], and 35/25 mm [1655]; Northern Territory, Darwin, on the right side of the road just before bridge to Channel Island; 12°33.228'S, 130°52.580'E; 14 Aug 2012; B Dayrat and field party leg.; station 61, Avicennia mangrove with sandy mud; NTM P.57626. • 9 specimens 35/25 mm [1667], 60/50 mm [1623], 40/25 mm [1668], 22/18 mm [1669], 8/5 mm [1624], 10/7 mm [1625], 15/10 mm [1670], 60/40 mm [1626], and 15/12 mm [1629]; same collection data as for the holotype; NTM P.57627.

Additional material examined

(historical museum collections). Australia • 1 specimen 38/30 mm; Northern Territory, Port Darwin; Mac Leay leg.; 12°30'S, 130°50'E; 1 Jan 1881; SMNH 180715.


(Fig. 6 View Figure 6 ). Endemic to Darwin, Northern Territory, Australia.


Peronia willani is named after Richard Willan, senior curator of mollusks at the Museum and Art Gallery of the Northern Territory, Darwin, Australia, who kindly and generously helped us during our field expedition around Darwin.


(Fig. 59 View Figure 59 ). Unlike most other Peronia species, which are usually found in the rocky intertidal, P. willani is primarily found on sandy mud or even directly on mud.

Color and morphology of live animals

(Fig. 60 View Figure 60 ). The color of the dorsal notum is highly variable, from nearly whitish to dark brown and greenish, most often mottled with darker and lighter areas. The color of the dorsal papillae varies as that of the background itself, but dorsal papillae can also be lighter (yellowish-greenish) than the background. The ventral surface (foot and hyponotum) varies from whitish (almost transparent) to yellowish and can change rapidly in any given individual. Occasionally, a black ring is present on the hyponotum around the pedal sole. The ocular tentacles are brown-grey, like the head. The dorsal notum of live animals is covered by dozens of papillae of various sizes. Some papillae bear black dorsal eyes at their tip. The number of papillae with dorsal eyes is variable (from 10 to 25). The largest specimens are 65 mm long.

Digestive system

(Figs 61A View Figure 61 , 62 View Figure 62 ). Examples of radular formulae are presented in Table 5 View Table 5 . The median cusp of the rachidian teeth is approximately 30 μm long. The hook of the lateral teeth is approximately 100 μm long. The intestinal loops are of type I, with the transitional loop oriented between 3 to 6 o’clock.

Reproductive system

(Figs 61B, C View Figure 61 , 63 View Figure 63 , 64 View Figure 64 ). In the anterior (male) parts, the muscular sac of the accessory penial gland is less than 25 mm long. The hollow spine of the accessory penial gland is narrow, elongated, and straight or slightly curved, and its shape (including at its tip) varies between individuals. Its length ranges from 1.5 mm ([1620] NTM P.57626) to 1.9 mm ([1628 H] NTM P.57625). Its diameter at the conical base ranges from 240 to 250 μm. Its diameter at the tip ranges from 80 to 100 μm. The retractor muscle is shorter or longer than the penial sheath and inserts near the heart. Inside the penial sheath, the penis is a narrow, elongated, soft, hollow tube. Its distal end bears conical hooks which are less than 37 μm long.

Diagnostic features

(Table 4 View Table 4 ). Peronia willani is characterized by a unique combination of anatomical traits: intestinal loops of type I (with a transitional loop oriented between 3 and 6 o’clock), retractor muscle inserting at the posterior end of the visceral cavity, muscular sac up to 25 mm, spine of the accessory penial gland between 1.5 and 1.9 mm long. Peronia willani is anatomically distinct from P. sydneyensis , with which it is most closely related (Figs 2 View Figure 2 - 4 View Figure 4 ), and from P. verruculata , from which it is close geographically (Fig. 6 View Figure 6 ).


A new species name is needed because no existing name applies to the species described here. A specimen from Darwin, Northern Territory, preserved in Stockholm (SMNH 180715) identified as O. verruculatum by Hoffmann (1928: 73) is identified here as P. willani because of its massive (18 mm long) muscular sac (Table 4 View Table 4 ). Also, to our knowledge, P. verruculata is not present in Northern Territory (Fig. 6 View Figure 6 ).