Pilosarachnidae Jiang & Li

Jiang, Tongyao, Xin, Yafei, Yao, Zhiyuan & Li, Shuqiang, 2020, Two new spider families from Late Cretaceous Kachin amber (Arachnida: Araneae), Zoological Systematics 45 (4), pp. 266-280 : 267-268

Family † Pilosarachnidae Jiang & Li , fam. nov.

Type genus. Pilosarachne Jiang & Li , gen. nov.

Diagnosis. Pilosarachnidae Jiang & Li , fam. nov. can be distinguished from Synspermiata by the presence of AME and the morphology of bulb which is not piriform; from Araneoidea and Palpimanoidea by the presence of cribellum; from Dionycha of RTA clade by the presence of ITC. The new family resembles modern cribellate RTA clade spiders (e.g., members of marronoid clade such as Dictynidae O. Pickard-Cambridge, 1871 , Desidae Pocock, 1895 , etc.) by the shape of cymbium, attaching angle of bulb relative to cymbium and the arrangement of tegular apophyses ( Figs 3A–D ), but can be easily distinguished by the absence of an RTA and the presence of serrate accessory claw setae. Pilosarachnidae Jiang & Li , fam. nov. resembles Hersiliidae Thorell, 1870 by the presence of feathery scales (in the sense of Griswold et al., 2005), discoid tegulum, presence of median apophysis and filiform embolus, but can be distinguished from the latter by the short clypeus, eye domain in an anterior-most position rather than in the center of the carapace, posterior lateral spinnerets not elongated and the presence of cribellum. The family also resembles Deinopidae C. L. Koch, 1850 and Uloboridae Thorell, 1869 by the presence of abundant feathery scales, a cribellum, and serrate accessory claw setae, but can be distinguished from both families by the absence of tarsal spines and contiguous lateral eyes; and additionally, from Deinopidae by the absence of enlarged PME and coiled embolus; and from Uloboridae by the absence of femoral trichobothria.

As for the extinct cribellate families at the same time and locality (i.e., Kachin amber), Pilosarachnidae Jiang &Li , fam. nov. can generally be distinguished from most cribellate families by the presence of rich feathery scales on carapace, abdomen and all appendages, such as † Alteruloboridae Wunderlich, 2018 , † Frateruloboridae Wunderlich, 2018 , † Praearaneidae Wunderlich, 2017 and † Protoaraneoididae Wunderlich, 2018 ( Wunderlich, 2017; Wunderlich & Müller, 2018). Pilosarachnidae Jiang & Li , fam. nov. resembles † Mongolarachnidae Selden et al., 2013 (occurs in Jurassic Daohugou bed and Kachin amber; Selden et al., 2011, 2013; Wunderlich, 2015, 2017) by the presence of serrate accessory claw setae, and with the presence of femoral spines and apical spines on male palpal tibia, but can be distinguished by the following combination of characters: 1. the absence of extremely long femur of male palp (palpal femur of almost identical length to femur III and shorter than carapace length), while male palpal femur in two subfamilies of Mongolarachnidae (Longissipalpinae and Pedipalparaneinae) is longer than femur III and the length of carapace; 2. the contiguous lateral eyes; 3. the spoon-like membranous conductor ( Figs 3A–B, D ), while in Mongolarachnidae the conductor is absent (see Selden et al., 2013: 1175, fig. 2f) or a filiform tegular apophysis (e.g., Wunderlich, 2015: 383–384, figs 186–190) or a fork-like sclerotized apophysis (see Wunderlich, 2015: 384, fig. 197) is present instead. Wunderlich (2015) provided a set of characters for Mongolarachnidae with description of two new genera from this family, i.e., Longissipalpus Wunderlich, 2015 and Pedipalparaneus Wunderlich, 2015 , in which he concluded that feathery hairs (equivalent to feathery scales in Griswold et al., 2005) are absent in this family. However, after examining our own specimens, we found that feathery scales are actually present in both Longissipalpus and Pedipalparaneus . Thus, we do not distinguish Pilosarachnidae Jiang & Li , fam. nov. and Mongolarachnidae base on the existence of feathery scales.

Additionally, Pilosarachnidae Jiang & Li , fam. nov. has a remarkable autapomorphy, the serrate structure on the prolateral-proximal margin of the tegulum, near the base of embolus ( Figs 3B, D ). This character is unique in comparison to other known spiders from Kachin amber. However, the detailed structures on male palp are highly variable at species-level and shouldn’t be considered for higher-level classification ( Ramírez, 2014), so we do not exclude the possibility that undiscovered species from the same family will lack such a structure.

Description. Medium-sized cribellate spider from Kachin amber. Three tarsal claws ( Figs 2B–C ), serrate accessory claw setae present; eight eyes, ALE and PLE contiguous ( Fig. 2E ); fovea distinct, longitudinal; body and appendages covered by dense feathery scales; spines numerous on legs but absent on tarsi, spines forming a ring at apex of each metatarsi ( Fig. 2A ); paracymbium absent; tibia of male palp without apophyses, embolus with pars pendula (a membranous structure that accompanies embolus), conductor and median apophysis present, and with a serrate structure on tegulum, present near base of embolus ( Figs 3A–D ).

Distribution. Late Cretaceous Kachin amber, Myanmar .

Figures

Figure 2. Pilosarachne ju Jiang & Li, gen. & sp. nov., holotype male. A. Habitus, lateral view. B. Tarsal claws of left leg II, lateral view. C. Tarsal claws of right leg II, ventral-apical view. D. Spinnerets, ventral view. E. Carapace, dorsal view. F. Chelicerae, anterior view. Scale bars: A=2.0mm; B–C, E=1.0mm; D, F =0.5mm.

Figure 3. Pilosarachne ju Jiang & Li, gen. & sp. nov., holotype male. A. Left palp, retrolateral view. B. Bulb of left palp, ventral view. C. Right palp, dorsal view, horizontally flipped for the sake of comparison. D. Left palp, ventral view. Scale bars: A, C–D=0.5 mm; B=0.2mm.