Landouria circinata Nahok & Tumpeesuwan & Tumpeesuwan 2021, sp. nov.
Creators: name: Nahok, Benchawan
name: Tumpeesuwan, Sakboworn
name: Tumpeesuwan, Chanidaporn
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Stylommatophora
Camaenidae
Landouria
Landouria circinata

description: Landouria circinata sp. nov.
urn:lsid:zoobank.org:act: B434E62B-9FA6-43FB-B27F-A4B1B0413225
Figs 3A, 4A, 5A, 6A–C; Tables 1–4
Landouria sp. – Tanmuangpak et al. 2012: 7, 12, fig. 5y. — Tanmuangpak 2016: 125–126, figs 4.74– 4.75.
Landouria sp.4 – Ounchareon 2015: 40–42, figs 4.12, 4.13, 5.1, 5.7.
Landouria sp.2 – Yingkhamhang 2016: 21–22, 39–41, 43–45, 47–48, figs 4.3–4.4, 4.21b, 4.22c, 4.23b, 5.1b, 5.2b.
Diagnosis
Shell brownish-corneous, periphery angular, sharply keeled. Flagellum circinate; penis cylindrical and longer than vagina; base of gametolytic sac thick and stout. Radula with unicuspid short tongue-shaped central teeth.
Etymology
The Latin word ‘ circinata ’ refers to the coiled or curled flagellum which resembles the circinate vernation of a fern shoot.
Type material
Holotype THAILAND • shell (SH = 8.2 mm, SW = 13.8 mm, AH = 5.1 mm, AW = 5.1 mm, UW = 3.8 mm); Loei Province, Mueang District, Phu Pha Lom Forest Park; 17°33′18.03″ N, 101°52′6.71″ E; alt. 415 m; 7 Jun. 2017; B. Nahok and U. Chanlabut leg.; NHMSU-00023. (Fig. 3A)
Paratypes THAILAND • 11 shells, 43 living specs; same collection data as for holotype; GenBank No. MN449401 and MZ435746; NHMSU-00024.
Description
SHELL (Fig. 3A, Table 1). Dextral, medium sized, conical-lenticular, with six slightly convex whorls. Suture shallow. Apex obtuse, depressed and low-conical. Light brown at 4 early whorls, dark brown at 2 last whorls. Sharply keeled, with pale brown band on the peripheral keel. Umbilicus very deep and wide. Aperture lip somewhat thickened, rounded rhombic.
GENITAL SYSTEM (n = 3) (Fig. 5A, Table 4). Penis very long, cylindrical, and curled, divided into two portions of equal length, internally with parallel, transverse folds, containing a short, rather rounded verge. Epiphallus short cylindrical, thinner than the penis. Flagellum slightly crenated and curled up, resembling the circinate vernation of a fern shoot, with thin grooves internally and tubercles on its surface at the end, internally with transverse robust folds. Vas deferens is a slender, cylindrical tube, thicker at the end where it connects to free oviduct; entering flagellum basally. Vagina less than half as long as penis, internally with four thin longitudinal pilasters. Free oviduct shorter than vagina. Gametolytic sac thickened at base, stout and gradually tapering distally to form a slender distal tube ending in a balloonshaped, medium-sized sac. Prostate gland very long, uterus long and swollen.
RADULA (n = 3). Comprises 95 transverse rows with 57–61 teeth per row; radular formula: (20)-(8–10)- 1-(8–10)-(20). Central tooth symmetric, unicuspid, tongue-shaped; lateral teeth longer than central tooth and oblique, unicuspid, tongue-shaped (Fig. 6A). Marginal teeth tricuspid with medium-sized endocone; mesocone rather large, with rounded cusp; ectocone triangular (Fig. 6B–C).
Remarks
Landouria circinata sp. nov. resembles L. strobiloides (see Tumpeesuwan & Tumpeesuwan 2019: fig. 3) in shell morphology, L. circinata sp. nov. has a smaller shell, a shallower suture, and darker peripheral zone than L. strobiloides (Table 4, Fig. 3A). Its central and lateral radular teeth are unicuspid and tongueshaped, whereas they are lanceolate in L. strobiloides (Table 4, Fig. 6A). The unique characters of L. circinata sp. nov. are its circinate flagellum and its penis that is much longer than the vagina (Fig. 5A), whereas L. strobiloides has a strobilus-like flagellum and a penis that is shorter than the vagina.
Distribution
Landouria circinata sp. nov. is known only from the type locality.
description: Published as part of Nahok, Benchawan, Tumpeesuwan, Sakboworn & Tumpeesuwan, Chanidaporn, 2021, Five new species of the land snail genus Landouria Godwin-Austen, 1918 (Gastropoda, Camaenidae) from northeastern Thailand, with note on genitalia and radula morphology of Landouria diplogramma (Möllendorff, 1902), pp. 142-166 in European Journal of Taxonomy 767 (1) on pages 149-153, DOI: 10.5852/ejt.2021.767.1495, http://zenodo.org/record/5514839