Rhiostoma hainesi Pfeiffer, 1862

Tongkerd, Piyoros, Tumpeesuwan, Sakboworn, Inkhavilay, Khamla, Prasankok, Pongpun, Jeratthitikul, Ekgachai, Panha, Somsak & Sutcharit, Chirasak, 2023, Systematic revision of the snorkel snail genus Rhiostoma Benson, 1860 (Gastropoda, Caenogastropoda, Cyclophoridae) with descriptions of new species, ZooKeys 1142, pp. 1-144 : 1

5. Rhiostoma hainesi Pfeiffer, 1862

Figs 17B, C , 18 , 21 , 22 , 32B

Rhiostoma hainesi Pfeiffer, 1862a: 115, pl. 12, fig. 8. Type locality: Camboja [Cambodia]. Pfeiffer 1865: 38, 39. Martens 1867: 64. Fischer 1891: 101. Kobelt 1902: 178. Fischer and Dautzenberg 1904: 427. Kobelt 1911: 762, pl. 113, fig. 1. Fischer 1973: 47. Tarruella and Doménech 2010: 189, fig. 1d. Tumpeesuwan 2001: 35-40, figs 4.7-4.9. Kongim et al. 2013b: 16, fig. 2e. Sutcharit et al. 2019: 28, fig. 6f, g.

Pterocyclos hainesii [sic]- Reeve 1863: Pterocyclos pl. 4, species 19.

Pterocyclus [sic] ( Rhiostoma ) Rhiostoma hainesi - Nevill 1878: 263.

Rhiostoma smithi Bartsch, 1932: 70, 71, fig. 1. Type locality: Khao Sabap, southern Siam [Khao Sabap, Khlung District, Chanthaburi Province, Thailand]. Abbott 1989: 34, with 2 figures (paratype). Solem 1966: 11. Panha and Thanamitramanee 1997: 2. Hemmen et al. 1999: 8, fig. 4. Patamakanthin 2001: 222, 223, fig. m1-m3. New synonym.

Rhiostoma tomlini Salisbury, 1949: 41, 42, pl. 3b, figs 3, 4. Type locality: Khao Sabap, Siam [Khao Sabap, Khlung District, Chanthaburi Province, Thailand]. Solem 1966: 11. Sutcharit et al. 2019: 51, fig. 12d. Chen et al. 2022: fig. 1b. New synonym.

Rhinostoma [sic] Rhinostoma housei kirai Habe, 1965: 128 [in part], pl. 2, fig. 11. Type locality: Chanthaburi, Thailand. New synonym.

Type material.

Syntype NHMUK 20170371 (2 shells; Fig. 21A ) from Camboja. Holotype NMNH 382943 (Fig. 21B ) of Rhiostoma smithi Bartsch, 1932, from Kao Sabap, S.E. Siam. Holotype NMW 1955.158.24924 (Fig. 21C ) of Rhiostoma tomlini Salisbury, 1949, from Khao Sabap, Thailand, paratype NHMUK 1949.6.7.1 (2 shells; Fig. 21D ) from Khao Sabap, Siam, and paratype NHMUK 20170372 (1 juvenile shell) from Khao Sabap, Siam. Holotype NSMT 52242 (Fig. 21E ) of Rhiostoma housei kirai Habe, 1965, from Chanthaburi, Thailand.

Other material examined.

Thailand: Khao Yai, Muang, Nakornnayok: CUMZ 4458. Khoa Sib Ha Chun, Kaeng Hang Maeo, Chanthaburi: CUMZ 10075, 10107. Klong Plub, Khlung, Chanthaburi: CUMZ 10017. Makok Waterfall, Khlung, Chanthaburi: CUMZ 3807, 3814, 3920, 3921, 4421, 4814 (Fig. 22B ), 4819, 4827, 10102, 10105, 10109. Trok Nong Waterfall, Khlung, Chanthaburi: CUMZ 4455. Ban Ma Kham, Ma Kham, Chanthaburi: CUMZ 10099. Phrabat Khao Ma Kham, Ma Kham, Chanthaburi: CUMZ 10116. Khlong Narai waterfall, Muang, Chanthaburi: CUMZ 10101. Plieu Waterfall, Chanthaburi: CUMZ 3801, 4336, 4338, 4339, 4340, 4380, 4381 (Figs 21F , 22A ), 4393, 4394, 4403, 4404, 4405, 4418, 4422, 4425, 4426, 4428, 4434, 10106, 10194 (Fig. 22D ). Si Bha Chan Waterfall, Muang, Chanthaburi: CUMZ 4733. Hin Dat waterfall, Pong Nam Ron, Chanthaburi: CUMZ 10100. Khao Soi Dao Wildlife Breeding Center, Soi Dao, Chanthaburi: CUMZ 3855, 3883, 3898, 3917, 4402, 4423, 4457, 4743, 10114, 10117. Wat Khao Sukim, Tha Mai, Chanthaburi: CUMZ 3803, 3815, 3828, 3918, 3919, 4867, 10103, 10108, 10110, 10111, 10118, 10119, 10120. Wat Tham Klong Tip, Tha Mai, Chanthaburi: CUMZ 10112. Chanthaburi: CUMZ 10113. Khao Chamao-Khao Wong, Khao Chamao, Rayong: CUMZ 4456, 4816 (Fig. 22C ), 4822, 10098. Khao Chamao Waterfall, Khao Chamao, Rayong: CUMZ 3897. Klong Pla Kang waterfall, Khao Chamao-Khao Wong, Khao Chamao, Rayong: CUMZ 10104. Wat Chat San Phatthanaram, Bo Rai, Trat: CUMZ 10115 .

Diagnosis.

Shell large, thick, and depressed. Detached whorl longer than aperture width, curved and descending. Apertural lip much expanded on palatal wall. Breathing device usually tubular and its tip often attached to preceding whorl. Shell usually with thick dark brown periostracum.

Differential diagnosis.

Rhiostoma hainesi differs from R. rhothonotaphrosa sp. nov. by having a large and stout last whorl, tubular- or notch-shaped breathing device, thickened brownish periostracum, and lip slightly thickened and widely expanded. In contrast, R. rhothonotaphrosa sp. nov. has a smaller shell size, slender last whorl, notch-shaped breathing device, white shell colour with brownish zigzag pattern, periostracum thin corneous, and lip thickened, slightly expanded, and multi-layered.

Description.

Shell. Shell large, cW 22.1-27.8 mm, cH 11.3-15.2 mm, thick, and discoidal shape; detached-whorl length 11.0-28.5 mm. Apex acute; spire elevated. Whorls 5 to 6, convex, increasing regularly; suture wide and slightly deep; last whorl rounded and stout. Shell surface with fine growth lines. Periostracum thick corneous with brownish to dark brown colour (without periostracum shell uniformly whitish to yellowish colour); with narrow dark spiral band on periphery. Detached whorl long, ~2 × longer than apertural width, curved and descending. Peristome circular and double; lip thickened, broadly expanded on palatal wall, and multi-layered. Aperture opened sub-laterally to sub-ventrally. Breathing device typically tubular (incomplete tube and notch shape sometime present), and its tip sometimes attached to preceding whorl; outer lip forms a short to long closed tube and is located just behind apertural lip; inner lip with small hole inside aperture (or deep incision in notch shape). Umbilicus widely opened and deep. Operculum calcareous, cup-shaped, and multispiral (Figs 21 , 22 ).

Radula. Teeth arrangement and shape are almost identical to R. housei . Central tooth with large central cusp and two lateral cusps on each side. Lateral teeth composed of four cusps; central cusp large with blunt tip; two inner cusps with pointed tips; one outer cusp small and dull. Marginal teeth each consisting of three pointed cusps (Fig. 32B ).

Distribution.

The previous records of R. hainesi were mostly from vague locations in Cambodia and Thailand: Khao Sabap (= Plieu National Park, Chanthaburi) ( Pfeiffer 1862a; Habe 1965). The recent study obtains specimens from several localities in Nakhonnayok, Rayong, and Chanthaburi provinces (Fig. 18 ).

Remarks.

Three nominal taxa have long been confused with R. hainesi : R. smithi Bartsch, 1932, R. tomlini Salisbury, 1949, and R. housei kirai Habe, 1965. The first two species were described based only on differences in shell colour and shapes of the breathing device. The type localities of both are from the same location at "Khao Sabap" [= Plieu National Park, Khlung, Chanthaburi, Thailand], and their holotypes are identical with R. hainesi (Fig. 21A-D ). The last taxon, R. housei kirai , was nominated as a subspecies of R. housei (sensu Habe 1965). However, the holotype (Fig. 21E ) exhibits a long and curved detached whorl, short tubular breathing device, expanded and thick apertural lip, and brownish periostracum (remaining inside umbilical area), which are the unique characters of R. hainesi . In addition, the type locality was Chanthaburi Province, which is within the distribution range of R. hainesi . Therefore, we recognise these three nominal taxa as junior subjective synonyms of R. hainesi .

The three variations in breathing device shape were reported in Tumpeesuwan (2001: fig. 5.2d-f): tubeless, incomplete tube, and complete tube. In this study, R. hainesi from Chanthaburi populations also exhibit sympatrically occurring morphs. The typical and more abundant morph has a short to long tubular breathing device (Figs 21F , 22A ), and the less abundant morph has a notch-shaped breathing device (Fig. 22C ). Specimens with these three distinct types of breathing devices were sampled for the COI analysis, and the results suggest that these are conspecific (Fig. 3 ).

Figures

Figure 3. Maximum likelihood (ML) tree showing the relationships among Rhiostoma species based on 660 bp of the mitochondrial COI gene sequence. The major nodes are indicated by numbers as the Maximum likelihood (ML) bootstrap values and Bayesian posterior probabilities of Bayesian inference (BI), respectively. Nodes with sufficient support by both ML and BI are indicated by black circles, and nodes with partial support by only ML are indicated by grey circles, and only BI by white circles. Newly described species in this study are highlighted in blue.

Figure 17. Live snails of the species group II A Rhiostoma housei specimen CUMZ 3987 from Ao Manow, Prachuap Khiri Khan B, C Rhiostoma hainesi from Khao Soi Dao, Chanthaburi B without breathing device and C with long breathing device D Rhiostoma jalorensis specimen CUMZ 3994 from Wat Tham Sue, Krabi. All figures are not to scale. Photographs: P. Tongkerd (B, C).

Figure 18. Distribution map of Rhiostoma housei - species group.

Figure 21. Shell of Rhiostoma hainesi A syntype NHMUK 20170371 from Camboja B holotype of " Rhiosotma smithi Bartsch, 1932 " NMNH 382943 from Khao Sabap, southern Siam C, D originally labelled as " Rhiostoma tomlini Salisbury, 1949 " from Khao Sabap, Siam C holotype NMW 1955.158.24924 and D paratype NHMUK 1949.6.7.1 E holotype of " Rhiostoma housei kirai Habe, 1965 " NSMT 52242 from Chanthaburi, Thailand F specimen CUMZ 4381 from Chanthaburi.

Figure 22. Shell of Rhiostoma hainesi A specimen CUMZ 4381 from Chanthaburi B specimen CUMZ 4814 from Makok Waterfall, Chanthaburi C specimen CUMZ 4816 from Khao Chamao, Rayong D specimens CUMZ 10194 from Chanthaburi shows series of growth from small juvenile (on the left) to nearly adult (on the right).

Figure 32. Radula morphology A Rhiostoma housei specimen CUMZ 3982 from Wat Tham Srivilai, Saraburi B Rhiostoma hainesi specimen from Chanthaburi C Rhiostoma jalorensis specimen CUMZ 3994 from Wat Tham Sua, Krabi D Rhiostoma ebenozostera sp. nov. paratype CUMZ 4704 from Tham Pha Poo, Loei E Rhiostoma lannaense sp. nov. paratype CUMZ 4701 from Chiang Dao, Chiang Mai F Rhiostoma tigrina sp. nov. paratype CUMZ 4497 / 2 from Mae Sai, Chiang Rai.