Shell

Description is based on the holotype, the numbers in brackets refer to the paratype I and paratype II, respectively. The shape is globose, the outer lip slightly thickened, pale brown, with three dark-brown bands; in the holotype and paratype I, the third band is wider than the first two; in paratype II, the middle band is the widest; and the other two are barely perceptible. The interior of the shell is white and shiny and the bands are visible. Shell with 4.2 whorls (4.1, 4.0). Protoconch shell caramel in colour, with 1.8 whorls (1.8 whorls, 1.8 whorls); the first 1.3 whorls without sculpture, then some isolated granules from 1.4 to 1.5 and the rest of the protoconch with well-marked growth lines. Sculpture of teleoconch consisting of white growth lines and covered by small oval granules. The umbilicus is obliquely perforate. Parietal callus is thin, translucent and white. Shell height 27.3 mm (27.3 mm, 20.0 mm); shell diameter 36.1 mm (35.5 mm, 26.0 mm); aperture height 19.9 mm (18.0 mm, 14.6 mm); aperture diameter 19.1 mm (19.6 mm, 13.2 mm) (Fig. 1 and Fig. 2).

Figure 1.  

Humboldtiana dugesi sp. nov. holotype CNMO8475.

Figure 2.  

Humboldtiana dugesi sp. nov. holotype CNMO8475 showing the details of the protoconch.

Reproductive anatomy

Penis globose, 6.9 mm, interior of the penis with a stout verge extending half of the penis cavity. The penis retractor muscle is inserted at the base of the epiphallus, which is 11 mm long. The epiphallus is short, cylindrical and measures 10.9 mm. Flagellum long, 73 mm in length, is nearly 4.07x the combined length of the penis plus epiphallus. The genital atrium is short, measuring 2.5 mm. The lower vagina is short and slightly taller than half penis size, 3.65 mm, extending to the region of the dart sacs; four dart sacs approximately of the same size, 2 mm. The median vagina bears four dart glands, forming a ring just above the dart sacs, with the dart glands reaching a maximum height of 3.2 mm. The spermathecal duct is 52 mm in length, the spermatheca bears a caecum of 5.4 mm length and it adheres to the albumen gland, the spermatheca is elongated and sac-shaped, with a length of 4.7 mm (Fig. 3).

Figure 3.  

Reproductive anatomy of Humboldtiana dugesi sp. nov. holotype CNMO8475. Abbreviations: cae, spermathecal caecum; dgla, dart glands; ds, dart sacs; epi, epiphallus; fla, flagellum; gen atr, genital atrium; pen, penis; pr, penis retractor; spd, spermathecal duct; spt, spermatheca; vag, vagina; vd, vas deferens.

Humboldtiana dugesi sp. nov. can be distinguished from other species included in the subgenus Humboldtiana by a protoconch with growth lines and granulated microsculpture, in opposition to the rest of the species of the subgenus where the protoconch lacks sculpture. On the other hand, in the reproductive anatomy, H. dugesi shared with H. potosiana the presence of a globose penis, but in H. dugesi, the penis bears a stout verge that covers half of the penis cavity; also, in H. dugesi, the flagellum is long, 4x the combined length of the penis plus epiphallus; meanwhile, in H. potosiana, the flagellum is short, barely 1x the combined length of the penis plus epiphallus.

This species is dedicated to the French-Mexican naturalist of the 19^th century, Alfredo Dugès, a pioneer in the study of natural history in Mexico, particularly in the state of Guanajuato.

Mexico: Guanajuato; Cuerámaro; Sierra de Penjamo; Fuerte de los Remedios, only known from type locality.

Three individuals were collected active in rock crevices during the day, two empty shells were collected in leaf litter, at an altitude of 1939 m a.s.l. The vegetation of the type locality is a temperate subhumid oak forest.

The new species described in this paper could be assigned to the Humboldtiana buffoniana species group of the subgenus Humboldtiana by the almost smooth sculpture of the protoconch and the dart glands just above the dart sacs. The Humboldtiana (Humboldtiana) buffoniana group comprises 20 species distributed from the border between New Mexico and Texas (Humboldtiana ultima) to the Mexican Transvolcanic Belt (Fig. 4). Since most of the species of the genus show an insular distribution and are only known from the type locality, we only compare the new species to the four closely-geographically distributed species of the Humboldtiana (Humboldtiana) buffoniana group, Humboldtiana potosiana Pilsbry, 1927 from Sierra de San Miguelito, San Luis Potosí (Pilsbry 1927); H. salviahispanica (Mejía et al. 2009) from Huichapan, Hidalgo, H. queretaroana (Dall 1897) and H. pinicola (Thompson and Brewer 2000), both from the Municipality of Pinal de Amoles in the Sierra Gorda of Querétaro (Fig. 4, Suppl. material 1). Humboldtiana dugesi has a small shell that is similar to H. salviahispanica and H. potosiana; also, the number of whorls and shell sculpture are similar; however, H. dugesi can be diagnosed by the presence of growth lines and isolated granules in the protoconch, the last of which is a unique character within the genus. On the other hand, in the reproductive anatomy, H. dugesi shares with H. potosiana a globose penis, but in H. dugesi, the epiphallus is long and cylindrical, the flagellum is long and 4x the combined length of the penis + epiphallus and the spermathecal appendix is present. In contrast, in H. potosiana, the epiphallus is short and stout, the flagellus is short, barely 1x the combined length of the penis + epiphallus and the spermathecal appendix is absent (Table 1).

Figure 4.  

Geographic distribution of the species included in the genus Humboldtiana. The star represents the collection record of Humboldtiana dugesi sp. nov. described in this paper. For details of the collection records of each species, please see the Supplementary file. Records of the species included in the Humboldtiana buffoniana species group are marked in red.