Hiatomegops spinalis, Guo & Selden & Ren, 2022

Guo, Xiangbo, Selden, Paul A. & Ren, Dong, 2022, New specimens from Mid-Cretaceous Myanmar amber illuminate the phylogenetic placement of Lagonomegopidae (Arachnida: Araneae), Zoological Journal of the Linnean Society 195, pp. 399-416 : 406-408

HIATOMEGOPS SPINALIS GUO ET AL. sp. nov.

( FIG. 3 )

Z o o b a n k r e g i s t r a t i o n: u r n: l s i d: z o o b a n k. org:act: 9168FFD9-29C1-4158-878B-D29E71594D41

Etymology: The specific name is the Latin adjective spinalis , meaning with spine(s), referring to the long macrosetae on the distal prolateral surface of palpal tibia.

Holotype: Female, specimenno.CNU-ARA-MA2020002.

Locality and horizon: Hukawng Valley, Kachin State, northern Myanmar; lowermost Cenomanian, Mid-Cretaceous.

Diagnosis: As for the genus.

Ta p h o n o m i c f e a t u r e s: C N U - A R A - M A 2 0 2 0 0 0 2: completely preserved; many bubbles and impurities are present around the spider. Parts of insect legs are present as syninclusions.

Description: Body length 2.89, carapace and legs darkcoloured, abdomen light-coloured, with an indistinct median dorsal stripe ( Fig. 3A, B ). Carapace piriform in outline, length 1.30, width 0.87 at widest point, covered with short, dense, feathery setae pressed flat against the cuticle ( Fig. 3A ). Cephalic region of carapace slightly raised, with a pair of anterolateral protrusions next to the inner side of PME ( Fig. 3E ). Fovea small oval, deeply depressed, situated in the centre of carapace, next to the posterior margin of cephalic region ( Fig. 3A ). Eight eyes present; PME enormous, 0.26 in diameter, situated on anterolateral corner of carapace; PLE small, placed at the mediolateral margin of cephalic region, separated 0.31 from the PME centre; AME and ALE contiguous, situated between the PME and the clypeal margin. Chelicera length 0.62, width 0.27 at base, cheliceral insertion close to mouthparts, stridulatory files absent. Fang length 0.22. Chelicera with about six peg teeth on promargin ( Fig. 3E ), retromargin not visible. Labium ligulate, slightly longer than wide, not fused to sternum. Endites elongated, converging and meeting in midline; serrula as a single row of teeth. Sternum shield shaped, covered with setae, convex and without tubercles.

Palpal podomere lengths: fe 0.34, pa 0.17, ti 0.24, ta 0.45. Palp hairy; tibia and tarsus with several dorsal trichobothria; tibia with a long macrosetae on the distal prolateral surface ( Fig. 3F ). Palpal claw absent.

Legs hairy, no legs enlarged; metatarsus slightly longer than tarsus. Leg formula II> I> IV> III: leg I cx 0.23, tr 0.07, fe 0.90, pa 0.47, ti 0.76, mt 0.64, ta 0.49; leg II cx 0.26, tr 0.07, fe 0.98, pa 0.40, ti 0.93, mt 0.63, ta 0.46; leg III cx 0.27, tr 0.07, fe 0.80, pa 0.36, ti 0.58, mt 0.47, ta 0.42; leg IV cx 0.33, tr 0.09, fe 0.93, pa 0.33, ti 0.73, mt 0.67, ta 0.47. Metatarsus and tarsus without scopulae. Distal preening comb composed of seven to ten short macrosetae, present on metatarsus of posterior legs ventrally. Feathery setae at least present on femur and patella of leg II. Tibiae with about ten, metatarsi with about six, tarsi with about six trichobothria in at least two rows. Three tarsal claws, paired claws with three to five teeth, median claw hook-like.

Abdomen ovoid, length 1.33, width 0.89, densely covered with short, feathery setae. Female genitalia simple, epigyne absent. A broad subovoid opening, interpreted as tracheal spiracle, situated on the postgastric area behind the epigastric furrow ( Fig.3G,H ). Six spinnerets; ALS with three segments, basal segment much longer than others; PLS about as large as ALS, with two segments, distal segment almost as the equal length with basal segment; retrolateral surface of distal segment with a series of large spigots ( Fig. 3I, J ).

Remarks: Lagonomegopidae was once thought to have a female-biased sex ratio ( Pérez-de la Fuente et al., 2013), but as more and more male lagonomegopids are found and described, this issue was resolved ( Park et al., 2019). The well-preserved female genitalia of CNU-ARA-MA2020002 shows that it is an unequivocal adult female.

Figures

Figure 3. Hiatomegops spinalis, holotype CNU-ARA-MA2020002: A, habitus, dorsal view, showing fovea (arrow) and feathery setae (magnified at the top right) on carapace; B, schematic drawing of dorsal habitus; C, habitus, ventral view; D, schematic drawing of ventral habitus; E, cephalothorax, anterior view, showing peg teeth (magnified at the bottom left); F, tibia and tarsus of right pedipalp, lateral view, showing trichobothria (asterisks) and long macrosetae (arrow); G, basal part of abdomen, ventral view, showing female genitalia and tracheal spiracle; H, schematic drawing of basal ventral abdomen; I, spinnerets, ventral view; J, schematic drawing of spinnerets, showing spigots (lower arrow). Scale bars represent 0.5 mm (A, B, C, D), 0.2 mm (E) and 0.1 mm (F, G, H, I, J).