Metalycaeus heudei

Information from the abstract

Metalycaeus heudei (Bavay & Dautzenberg, 1900) Figs 2 A, 3 Alycaeus (Charax) heudei Bavay & Dautzenberg, 1900: 121–122. Type locality: Haut-Tonkin. Metalycaeus heudei – Páll-Gergely et al. 2020 d: 143 –144. Páll-Gergely et al. 2021: 53, fig. 41. Material examined. Laos • 2 shells; Houaphanh Province, Viengxay District, Ban Nathan village; 20°27'28.1"N, 104°08'43.4"E; 965 m a. s. l.; 6 Oct. 2022; leg. K. Inkhavilay; CUMZ 14473 –14474 (Figs 2 A, 3) • 17 shells; Houaphanh Province, Viengxay District, Ban Hang Long village; 20°27'38.7"N, 104°10'28.6"E; 840 m a. s. l.; 6 Oct. 2022; leg. K. Inkhavilay; CUMZ 14475. Diagnosis. Shell depressed to conical. Protoconch scaly; spiral striation starting from R 1, continuing to the end of R 2. R 1 ~ 1 ¾ whorls with regular, strong radial ribs. R 2 ~ ¼ whorl and nearly twice as long as R 3; with ~ 32 ribs. R 3 with less distinct ribs, strongly coiling downwards being highly oblique to horizontal axis of the shell, slightly expanding near the end of the aperture. Inner peristome blunt, slightly protruding. Outer peristome thickened, multilayered, expanded in various degrees, not reflected. Apertural lip finely granulated, mostly with 4–6 wavy ridges inside the apertural tube at the position when the tube starting to coil downward. Umbilicus round, close. Differential diagnosis. See Páll-Gergely et al. (2017: 83). Distribution. Yunnan, Hunan and Hubei provinces, China; Shan and Kayah States, Myanmar; northern Vietnam; Luang Prabang (Páll-Gergely et al. 2017, 2021) and Houaphanh provinces, Laos. Remarks. Metalycaeus heudei is one of the most widely distributed alycaein species known, with high variation in shell size, shell shape from depressed to conical, R 2 length and shape (bulging or not), and the strength of the swelling on R 3. The shells from Houaphanh Province, Laos in this study correspond to the conical end of the shell shape spectrum (paviei form). These shells are also very similar to the type material of Alycaeus paviei var. minor Bavay & Dautzenberg, 1912 in having a close umbilicus and ridges inside the apertural tube at the position when the tube starting to coil downward. In addition, a lack of spiral striation on the protoconch was detected in these shells, aligning to the previous report that not all shells from the same Metalycaeus species possess this character (Páll-Gergely et al. 2017, 2021). See earlier taxonomic treatment of M. heudei in Páll-Gergely et al. (2021).

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Related topics: Diatoms and Algae Research · Calcium Carbonate Crystallization and Inhibition · Marine Bivalve and Aquaculture Studies