Xim, Ibarra-Núñez & Chamé-Vázquez & Maya-Morales, 2021

Ibarra-Núñez, Guillermo, Chamé-Vázquez, David & Maya-Morales, Julieta, 2021, A new spider genus (Araneae: Linyphiidae: Erigoninae) from a tropical montane cloud forest of Mexico, European Journal of Taxonomy 731, pp. 97-116 : 101-102

Xim gen. nov.

urn:lsid:zoobank.org:act:E6CE6724-C10E-47E9-BC3A-9FC415514958

Figs 1–5

Type species

Xim trenzado gen. et sp. nov. by monotypy and present designation.

Diagnosis

Xim gen. nov. is sister to a clade including Ceratinopsis Emerton, 1882 , Tutaibo Chamberlin, 1916 and Sphecozone O. Pickard-Cambridge, 1871 . Xim gen. nov. shares with each of these three genera a subtegulum ectal to the tegulum ( Figs 2C, F , 3A ), a membranous connection between radix and embolus ( Fig. 2B ), embolus originated from radix at a distinct angle ( Figs 2B, E , H–I, 3B), a short, entire epigynum ( Fig. 5 A–B, G), fertilization duct separated from copulatory duct ( Fig. 5H ), and copulatory openings at the dorsal plate-ventral plate junction ( Fig. 5 A–B). Additionally, Xim gen. nov. shares with Ceratinopsis and Tutaibo an intersegmental, straight-hook paracymbium ( Fig. 2C, F ), a tegulum with papillae ( Fig. 2 B–C, E–F, H), a spiral radical tailpiece ( Figs 2 A–B, D–E, 3B) and a radical ridge ( Figs 2E , H–I, 3B). Xim gen. nov. differs from each of those three genera by having a high cymbium ( Figs 1B , 2A , C–D, F), a large paracymbium ( Figs 2 A–F, 3A), a very short straight embolus ( Figs 2B, E , H–I, 3B), male cheliceral stridulatory striae scaly, widely and evenly spaced, both sexes with a post-ocular lobe ( Fig. 1B, E ), male with two series of prolateral macrosetae on femur I ( Figs 1 A–B, 4A–G), and the female by having strongly oblong, u-shaped spermathecae ( Fig. 5 C–H). Furthermore, Xim gen. nov. differs from Ceratinopsis by lacking trichobothria on the prolateral side of palpal tibia, by having a retrolateral tibial apophysis ( Fig. 2C, F ) and the dorsal plate of epigynum with an anterior lobe flush with the ventral plate ( Fig. 5 A–B, G); from Tutaibo by lacking a cymbial basal excavation and a tegular sclerite on the anterior part of the tegulum, by having a cymbium retrolateral groove ( Fig. 2C , F–H), an embolic membrane ( Figs 2E , H–I, 3B), copulatory ducts not encapsulated ( Fig. 5 C–F, H) and male lacking a proximal dorsal macroseta on the tibiae I and II; from Sphecozone by having a paracymbium ( Figs 2 A–F, 3A), a cymbial retrolateral groove ( Fig. 2C , F–H), by lacking a cymbial basal excavation, and by lacking an epigynal atrium.

Etymology

The genus is named after the word spider in the Mam language, whose native speakers inhabit the border area between Mexico and Guatemala. The gender is masculine.

Description

BODY. Small (1.49–1.91), light brown; post-ocular lobe conical, lower in females; AER and PER slightly recurved; male with prolateral macrosetae on femur I; leg formula 1423.

MALE PALP. Tibia with conspicuous prolateral apophysis, small retrolateral apophysis and one retrolateral trichobothrium; cymbium with prolateral and dorsal processes; paracymbium large; tegulum elliptical; radix with spiral tailpiece and serrated ridge; embolus very short and straight.

EPIGYNUM. Ventral plate large, ovoid with anterior semicircular concavity; dorsal plate small rectangular and transverse with large anterior lobe; copulatory openings as narrow slits between ventral plate and anterior lobe of dorsal plate; copulatory ducts short and wide; spermathecae oblong, u-shaped with one mesal and one ectal branch; fertilization ducts small.

Phylogenetic relationships and justification of monotypy

Our phylogenetic analysis yielded eight equally most parsimonious trees (L 1096, CI 0.19, RI 0.58; excluding uninformative characters 104 and 155: L 1094). The topology of the strict consensus of these trees (L 1099, CI 0.19, RI 0.58) is identical to the consensus tree of Frick et al. (2010), except that here (and in each of the eight most parsimonious trees) Xim trenzado gen. et sp. nov. is sister to a clade that includes Ceratinopsis , Tutaibo and Sphecozone ( Figs 6–7 ), corresponding to clades 76 of Miller & Hormiga (2004) and 62 of Frick et al. (2010). Circumscribing Xim trenzado gen. et sp. nov. within a polytypic genus would require synonymization of these three genera. Nevertheless, Miller & Hormiga (2004: 402) stated that the monophyly of Sphecozone and Tutaibo are not in doubt and are clearly diagnosable. The phylogenetic analysis supports, with nine unambiguous characters, the hypothesis that Xim trenzado gen. et sp. nov. is not congeneric with the genera included in clade 76 of Miller & Hormiga (2004), making necessary a new genus for this species. The nine unambiguous characters of Xim trenzado gen. et sp. nov. are: cymbium as tall as long (9-1); sperm duct path in distal part of tegulum with thigh kink (23-1), embolus short (43-1), initial orientation of PTA perpendicular (68-0), RTA present (70-1), male with a post-ocular, conical lobe (103-1), cheliceral stridulatory striae scaly (117-1), female palpal tarsus without proximal dorsomesal macrosetae (127-0), female palpal tarsus with one ventroectal macrosetae (132-1).

Figures

Fig. 1. Xim trenzado gen. et sp. nov. A–C, G. ♁ (ECOTAAR-004950). D–F, H. ♀ (ECOTAAR-005063). A–F. Habitus. A, D. Dorsal view. B, E. Lateral view. C, F. Ventral view. G, H. Carapace in frontal view. Scale bars: A–F = 0.25 mm.

Fig. 2. Xim trenzado gen. et sp. nov., male left palpus. A–C. ECOTAAR-004974. D–E, G–I. ECOTAAR-004950. F. ECOTAAR-004952. A, D. Mesal view. B, E. Ventral view. C, F. Ectal view. G. Dorsal view. H. Apical view. I. Detail of E showing radix and embolus. Scale bars: A–E = 50 μm; F = 20 μm.

Fig. 3. Xim trenzado gen. et sp. nov., male left palpus, schematic. A. Palpus without embolic division, ventral view.B. Embolic division with part of distal suprategular apophysis, ventral view. Scale bars: A = 50 μm; B = 40 μm.

Fig. 4. Xim trenzado gen. et sp. nov. A–B. ECOTAAR-004950. C–F, H–I. ECOTAAR-004962. G. ECOTAAR-004952. A–G. Male left femur I. D–G. Details of macrosetae. A, D. Dorsal view. B, E. Prolateral view. C, F. Ventral view. G. Apical view. H. Tarsal organ of leg I. I. Trichobothrium of retrolateral palpal tibia. Scale bars: A–C = 70 μm; D–F = 30 μm; H = 5 μm; I = 10 μm.

Fig. 5. Xim trenzado gen. et sp. nov., ♀, epigynum. A–B. ECOTAAR-005063.C–F. ECOTAAR-005183. A, G. Ventral view. B. Posterior view. C–D, H. Dorsal view. D. Detail of C showing left copulatory duct and spermatheca. E. Antero-dorsal view. F. Detail of E showing left copulatory duct and spermatheca. Scale bars: A–C, E, G–H = 40 μm; D, F = 20 μm.

Fig. 6. Strict consensus tree of the eight most parsimonious trees, showing only the distal clades where Xim trenzado gen. et sp. nov. is situated. Tree with Bremer support values noted beside nodes.

Fig. 7. Strict consensus tree of the eight most parsimonious trees, showing only the distal clades where Xim trenzado gen. et sp. nov. is situated. Tree with unambiguous character optimization; character and character-state numbers given above and below marks, respectively; color of marks denotes homoplasious (white) or non-homoplasious (black) character-state changes.