Dibolostethus Hoffman, 2009

Means, Jackson C., Bouzan, Rodrigo S., Iniesta, Luiz Felipe Moretti, Martínez-Torres, Daniela, Vasquez-Valverde, Luisa F., Brescovit, Antonio D. & Ivanov, Kaloyan, 2023, A review of the previously monotypic tribe Dibolostethini (Chelodesmidae: Chelodesminae) with description of two new species and a summary of the Chelodesmidae of the Tropical Andes Biodiversity Hotspot, European Journal of Taxonomy 885 (1), pp. 65-85 : 78-81

Key to males of Dibolostethus Hoffman, 2009

1. Sternite of 5 th body ring with two pairs of short, blunt projections ( Fig. 3D ); apex of gonopodal prefemoral process with large, tongue-shaped lobe, best seen in anterior view ( Fig. 7B ); Colombia.......................................................... D. kattani Means, Bouzan, Martínez-Torres & Ivanov sp. nov.

– Sternite of 5 th body ring without modifications; apex of gonopodal prefemoral process not as above; Ecuador............................................................................................................................................. 2

2. Projections on sternite of 4 th body ring stout, conical, curving at tip between coxae, appressed along entire length ( Fig. 4C–D ); prefemoral process and solenomere together resembling blacksmithing bolt tongs in lateral and mesal views ( Fig. 6A, C ); body length approximately 30 mm; color of appendages and body uniform ............................... D. inopinatus Means, Bouzan & Ivanov sp. nov.

– Projections on sternite of 4 th body ring thin, blade-like, curving beyond coxae, separated along entire length ( Fig. 4A–B ); prefemoral process enveloping, and partially obscuring solenomere in mesal view ( Fig. 5C ); body length less than 25 mm; color of appendages lighter and contrasting with that of body ..................................................................................................... D. sicarius Hoffman, 2009

A total of 34 chelodesmid genera have been reported from the Tropical Andes Biodiversity Hotspot ( Table 1 ). These include 24 genera from 9 nine tribes and 10 additional genera currently unassigned to a tribe. Of the 34 genera known from the Tropical Andes, 9 (25%) are monotypic. The most species rich genera in the region include Trichomorpha Silvestri, 1897 (26 spp.), Leptodesmus de Saussure, 1859 (13 spp.), Chondrodesmus Silvestri, 1897 (11 spp.), and Biporodesmus Attems, 1898 , Trachelodesmus Peters, 1865 , and Leiodesmus Silvestri, 1897 (5 spp. each). Conversely, 15 genera are represented in the region by a single species ( Table 1 ).

Taxa have been reported from six of the seven (excluding Chile) countries falling within the boundaries of the Tropical Andes ( Fig. 9 ). The most widespread genus in the region is Leptodesmus , stretching from northwestern Venezuela to northwestern Argentina (> 3800 km). It is important to note that Hoffman (1971) restricted the genus to only 21 species endemic to Brazil, with the remaining taxa considered incertae sedis, and without assignment at the generic level ( Bouzan et al. 2021).

The number of species and records (in parentheses) from each country are as follows: Colombia – 49 species (61 records); Venezuela – 21 (26); Peru – 19 (27); Ecuador – 13 (13); Argentina – 5 (6); and Bolívia – 4 (4); for a total of 110 species and 137 records (Supp. file 1). A.kmz file of the Chelodesmidae of the Tropical Andes is provided as Supp. file 2.

Figures

Fig. 3. Dibolostethus Hoffman, 2009 somatic characters continued. A, E. Dibolostethus sicarius Hoffman, 2009, holotype, ♂ (VMNH110810). B–D. D. kattani Means, Bouzan, Martínez-Torres & Ivanov sp. nov., holotype, ♂ (ICN-MD-1317-1). A. Coxa 2, mesal view, red arrow = gonopore. B. Left leg 4, posterior view, red arrow = tibial ventro-apical projection. C. Left leg of 5th leg pair showing incrassate femur, red arrow = tibial ventro-apical projection. D. Body ring 5, lateral view, red circle = anterior pair of sternal projections. E. Prefemur 5, red arrow = basal pore. Abbreviations: Cx = coxa; Pf = prefemur.

Fig. 7. Dibolostethus kattani Means, Bouzan, Martínez-Torres & Ivanov sp. nov., holotype, ♂ (ICN- MD-1317A), right gonopod. A. Mesal view. B. Anterior view. C. Lateral view. Red circles = cingulum. Dashed lines = prostatic groove. Abbreviations: Lb = lobe; PfP = prefemoral process; S = solenomere; Sh = shelf.

Fig. 4. Body ring 4, sternal projections. A–B. Dibolostethus sicarius Hoffman, 2009, holotype, ♂ (VMNH110810). C–D. D. inopinatus Means, Bouzan & Ivanov sp. nov., holotype, ♂ (VMNH110813). A, C. Lateral views. B, D. Posterolateral views. Abbreviation: Cx = coxae.

Fig. 6. Dibolostethus inopinatus Means, Bouzan & Ivanov sp. nov., holotype, ♂ (VMNH110813), left gonopod. A. Lateral view, red circle = cingulum. B. Anterior view. C. Mesal view. Dashed lines = prostatic groove. Abbreviations: PfP = prefemoral process; S = solenomere.

Fig. 5. Dibolostethus sicarius Hoffman, 2009, holotype, ♂ (VMNH110810), left gonopod. A. Lateral view. B. Anterior view. C. Mesal view. Red circles = cingulum. Dashed lines = prostatic groove. Abbreviations: PfP = prefemoral process; S = solenomere.

Fig. 9. Distribution of Chelodesmidae spp. in the Tropical Andes Biodiversity Hotspot, by country. Note: the type locality of Dibolostethus sicarius Hoffman, 2009 is included for completeness although it falls just outside of the boundaries of the Tropical Andes Biodiversity Hotspot. For information on these taxa see Supp. file 1.