Quantula doma Deeprom & Tumpeesuwan & Tumpeesuwan 2022, new species

Quantula doma, new species

(Figs. 3B–C, 4B–C, 6A–J; Tables 1 –3)

Quantula sp. – Jumlong et al., 2013: 71–72, 74–76, 78–79, fig. 3.

Quantula weinkauffiana – Worachak, 2014: 40–42, figs. 4.1A–B, 4.2 A–C, 4.3 B–C.

Quantula sp. 1 – Worachak, 2014: 43–45, figs. 4.4A, 4.5A–E, 4.6A–B.

Quantula sp. 1 – Jirapatrasilp et al., 2021: 193 (1), 262–263. Quantula striata – Hoompuay, 2016: 22–25, figs. 4.1–4.3. Quantula sp. 6 – Hoompuay, 2016: 43–45, figs. 4.21–4.24.

Material examined. Holotype: NHMSU-00048 (Fig. 4B) from Khao Sala, Buachet District, Surin Province; 14°25′50.5″N 103°56′15.6″E; 14 October 2017; SH = 18.69 mm, SW = 28.61 mm. Paratypes: 47 shells (25 adults & 22 juveniles), 28 living specimens; same data as holotype; NHMSU-00049. One shell (NHMSU-00050) from Phu Jor Kor, Nong Soong District, Mukdahan Province; (16°22′22.1″N, 104°22′32.2″E), 11 October 2017 (Fig. 4C); Two adult and three juvenile shells, and nine living specimens (NHMSU-00051) same locality as NHMSU-00050; One adult and one juvenile shells and two living specimens (NHMSU-00052); Pha Nam Yoi, Nong Phok District, Roi Et Province, Thailand; 16°19′22.3″N 104°19′33.4″E; 11 October 2017; seven adult and three juvenile shells, and five living specimens (NHMSU-00053), same data with NHMSU-00052.

Diagnosis. Last whorl angular with peripheral keel, not descending in front. Amatorial organ duct longer than amatorial organ.

Etymology. The specific epithet is derived from the Latin word ‘domus’ meaning roof, referring to the fact that its shell shape is similar to a hemispherical roof.

Description. Shell (n=48, 26 adult & 22 juveniles from Khao Sala (Fig. 4B) and n=20, 11 adults & 9 juveniles from Phu Jor Kor and Pha Nam Yoi (Fig. 4C)): Dextral, domeshaped to depressed-conic lenticular, with 6–6¼ whorls, suture shallow, growth line prominent. Last whorl angular with peripheral keel, but less sharp than Q. wienkauffiana. Shell height 14.8–21.9 mm, shell width 25.1–35.3 mm. Apex blunt, shell light brown, ventral side paler than dorsal side. Apertural lip simple and thick, and slightly expanded at columellar side in adult specimens. Umbilicus narrow and deep.

Body (n=28 from Khao Sala (Fig. 3B) and n = 11 from Phu Jor Kor and Pha Nam Yoi (Fig. 3C)): Living snail orange brown, with two lateral light brown or dark stripes running from base of each upper tentacle backward to pneumostome.

Genitalia (n=13, comprising three specimens from Khao Sala (one specimen from Hoompuay, 2016) (Fig. 6A–E), three specimens from Phu Jor Kor, and seven specimens from Pha Nam Yoi (five specimens from Hoompuay, 2016) (Fig. 6F–J): Penis short, cylindrical, inner wall with robust longitudinal penial pilaster alternating with 1–2 thin longitudinal pilasters (Fig. 6D), whereas specimens from Phu Jor Kor sculptured with irregular undulate penial pilasters arranged in inclined and longitudinal rows (Fig. 7D). Epiphallus shorter than penis. Vas deferens longer than penis. Gametolytic duct connecting to basal part of amatorial organ, basally bulbous, distally with short and small duct. Tapering gametolytic sac long, robust (Fig. 6A). Amatorial organ elliptical, with inner wall smooth. Papilla of amatorial organ strong, long, reaching junction of gametolytic duct. Corneous spike present (Fig. 6B–C). Amatorial organ duct longer than amatorial organ. Vagina and free oviduct shorter than penis. Inner wall of vagina smooth, with 3–4 thin longitudinal pilasters on median part (Fig. 6E). Specimens from Phu Jor Kor has gametolytic duct connecting to middle part of amatorial organ. Gametolytic sac cylindrical, long. Amatorial organ long, cylindrical, with inner wall sculptured with irregular undulated short pilasters. Papilla of amatorial organ robust, cylindrical, distally finger-shaped, without terminal corneous spike. Vagina longer than penis, internally with four to five longitudinal pilasters. Amatorial organ duct nearly as long as, or slightly longer than amatorial organ.

Radula (n=13, comprising three specimens from Khao Sala (one specimen from Hoompuay, 2016) (Fig. 7A–B) three specimens from Phu Jor Kor, and seven specimens from Pha Nam Yoi (five specimens from Hoompuay, 2016) (Fig. 7C–D): with 83–90 rows of teeth. Each row with 83–123 teeth, formula: (24–42) + (17–19) + 1 + (17–19) + (24–42) in specimens from Khao Sala, and approximately 70–82 rows of teeth, each of which comprises 91–123 teeth. Fomula: (31–43) + (14–18) + 1 + (14–18) + (31–43) in specimens from Phu Jor Kor and Pha Nam Yoi. Central and lateral teeth lanceolate, tricuspid. Marginal teeth bicuspid and gradually changing to unicuspid and sword shaped.

Distribution. Quantula doma, new species, is found in sandstone mountains of the southern part of north-eastern Thailand, in the Surin, Roi Et, and Mukdahan Provinces.

Remarks. According to the genetic distance and phylogenetic analysis, Quantula “sp. 1” from Khao Sala in Jirapatrasilp et al. (2021) (specimen no. H60, COI and 28s accession numbers MT803088 and MT741936) is clustered with the Q. doma, new species (specimen no. KSH and KSL). Genetic distances within the Khao Sala population are around 0.5% (Table 2), and all specimens have rather strong support (Fig. 2) (BI posterior probability of 1.00 and 100% for ML, and 99% for NJ bootstrap replicate), based on which we conclude that specimen H60, KSH and KSL represent the same species as Q. doma, new species. Although conchologically this new species looks similar to Q. simonei Thach & Huber 2018 from Laos (see Thach, 2018: plate 49, figs. 580, 581 top), in Q. doma, new species, the last whorl is angulate with weak peripheral keel and has an open umbilicus, whereas in Q. simonei, the last whorl is well-inflated without peripheral keel, and the umbilicus is mostly covered by the columella portion of the apertural lip.