Discartemon tonywhitteni Sutcharit & Panha, 2020

Sian Man, Nem, Siriboon, Thanit, Lin, Aung, Sutcharit, Chirasak & Panha, Somsak, 2022, Revision of the carnivorous land snail family Streptaxidae (Stylommatophora, Achatinina) in Myanmar, with description of four new species, ZooKeys 1110, pp. 39-102 : 39

Discartemon tonywhitteni Sutcharit & Panha, 2020

Figs 1 , 2A , 3A, B , 4A, B , 5 , 24A

Discartemon tonywhitteni Sutcharit & Panha in Sutcharit et al. 2020: 154, fig. 3a-c. Type locality: Phra (Buddha) Cave, Lenya National Park, Tanintharyi Township, Tanintharyi Region, Myanmar.

Material examined.

Holotype CUMZ 5108; paratypes CUMZ 5107 (14 shells), CUMZ 5101 (30 shells), CUMZ 5102 (25 shells), CUMZ 5104 (18 shells), CUMZ 5105 (30 shells), CUMZ 5106 (20 juvenile shells). Limestone outcrop ~ 3.4 km south of the Phra (Buddha) Cave, Lenya National Park, Tanintharyi Township, Tanintharyi Region, Myanmar (11°11'56.2"N, 99°10'25.7"E): CUMZ 13001 (7 specimens in ethanol; Fig. 3A, B ).

Diagnosis.

This species was clearly described in Sutcharit et al. (2020). Shell is depressed-heliciform, white and translucent, spire low conical to convex with wide and depressed suture. Shell surface glossy, with fine transverse ridges that diminish below periphery; varices present. Embryonic shell large, ~ 2½ whorls with smooth surface; following whorls in regularly expanding coil. Last whorl usually angular; widely open umbilicus. Apertural dentition with one strong parietal, one palatal, one basal, one columellar and one supracolumellar lamella (Fig. 3A, B ).

Genital organs. Atrium (at) short. Penis (p) long and slender. Penial sheath (ps) thin and extending ~1/2 to 3/4 of penis length; penial sheath retractor muscle (psr) very thin, originating at atrium and inserting distally on penial sheath (Fig. 4A ). Vas deferens (vd) very short, ~ 1/6 of penial sheath length and passes through penial sheath before entering penis distally (Fig. 4B ). Penial retractor muscle (pr) thin and very long, inserting at penis and vas deferens junction.

Internal wall of atrium generally smooth (Fig. 5A ). Proximal and middle penial wall with dense and translucent penial hooks (~ 5 hooks/200 μm 2) and located on conical papillae (Fig. 5B-D ). Penial hooks small (<0.04 mm in length), expanded at base, tips pointed (Fig. 5C, E ). and curved towards genital orifice. Most penial hooks with blunt tips (Fig. 5E ). Distal penial wall with dense and translucent conical penial papillae with embedded penial hooks, ~ 12 penial papillae/200 μm 2 (Fig. 5F ).

Vagina (v) short, ~ 1/3 of penis length. Gametolytic duct (gd) a long tube extending as far as albumin gland; gametolytic sac (gs) ovate. Free oviduct (fo) long, ~ 2 times of vagina length. Oviduct (ov) slender and folded; prostate gland inconspicuous and bound to oviduct. Talon (ta) small, short and club shaped. Hermaphroditic duct (hd) bearing long seminal vesicle (sv) ca. twice as long as the length from talon to branching point of seminal vesicle (Fig. 4A ).

Vaginal wall with transverse vaginal folds; vaginal hook absent (Fig. 5G ).

Radula . Each row consists of ~ 35-49 teeth with formula (24-17) -1- (17-24). Central tooth very small with pointed cusp. Lateral and marginal teeth undifferentiated, unicuspid and lanceolate. Latero-marginal teeth gradually reducing in size, with outermost teeth much smaller and shorter than inner teeth (Fig. 24A ).

Distribution.

Discartemon tonywhitteni is the southernmost distributed species and, currently, is known as the only form from the type locality (Fig. 1 ), which is an isolated limestone outcrop in Tanintharyi Region, southern Myanmar ( Sutcharit et al. 2020).

Remarks.

Sutcharit et al. (2020) described D. tonywhitteni based only on shells. Fortunately, seven alcohol-preserved specimens collected near the type locality were sent by the FFI staff after the species was published. These additional specimens allow us to describe the genitalia and radular morphology of this species herein.

Figures

Figure 1. Approximate sampling locations used in this study. The location name and coordinates are listed in Table 1. Historical type localities of a broad scale, such as Tavoy, Burma, Moulmein, Mergui, and Tenasserim, are not indicated on this map.

Figure 2. Living snails A Discartemon tonywhitteni from near Phra (Buddha) Cave, Tanintharyi Region (shell width ~ 10 mm) B Discartemon paurodeviatus sp. nov. from the type locality (shell width ~ 11 mm) C Haploptychius heliakosus sp. nov. from the type locality (shell height ~ 9 mm) D Carinartemis exacutus from Lun Nga Mountain, Kayin State (shell height ~ 14 mm) E, F Carinartemis sankeyi (E) from Kayon Cave, Mon State (shell height ~ 10 mm) and (F) from Saddan Cave, Mawlamyine, Mon State (shell height ~ 10 mm).

Figure 3. A, B Discartemon tonywhitteni, specimen CUMZ 6264 from Phra (Buddha) Cave, Tanintharyi Region C-E Discartemon paurodeviatus sp. nov. C holotype CUMZ 13002 with apertural dentition and D, E paratypes CUMZ 13003 from the type locality.

Figure 4. Genital anatomy of A, B Discartemon tonywhitteni, specimen CUMZ 13001 A reproductive system and B insertion of vas deferens into penial sheath C, D Discartemon paurodeviatus sp. nov., paratype CUMZ 13003 C reproductive system and D insertion of vas deferens into penial sheath.

Figure 5. Internal sculpture of genitalia of Discartemon tonywhitteni, specimen CUMZ 13001 A atrium surface B arrangement of penial hooks on proximal part of penis C lateral view of proximal penial hooks D arrangement of penial hooks on middle part of penis E high magnification view of pointed penial hooks on middle part of penis F top view of distal penial hooks embedded in penial papillae G arrangement of transverse vaginal folds.

Figure 24. Radula of specimens A Discartemon tonywhitteni, paratype CUMZ 13001 B Discartemon paurodeviatus sp. nov., paratype CUMZ 13003 C Haploptychius heliakosus sp. nov., paratype CUMZ 13014 D Carinartemis exacutus, specimen CUMZ 13021 E, F Carinartemis sankeyi, specimen CUMZ 13029 E overview of radula and F high magnification of central teeth.