Gigarachnidae 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 : 272-273

Family † Gigarachnidae Jiang & Li , fam. nov.

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

Diagnosis. Gigarachnidae Jiang & Li , fam. nov. can be distinguished from most extant Araneoidea by the absence of paracymbium; from Palpimanoidea by the absence of peg teeth; from Synspermiata by the presence of AME and nonpiriform bulb ( Figs 5D , 6A–C ); from RTA clade by the absence of an RTA and the relative position of cymbium and bulb ( Figs 6A–C ); from Hypochilidae and Austrochilidae by the presence of only one pair of booklungs.

The cribellar area of Gigarachnidae Jiang & Li , fam. nov. is covered by impurity and was thus not observable, but it can be distinguished from many extinct families from Kachin amber by the combination of gigantic size (the largest known araneomorph spider in Kachin amber), absence of any apophyses on the male palpal podomeres ( Fig. 6C ) and the complex tegular apophyses ( Figs 6A–C ). Some members of the family † Pholcochyroceridae Wunderlich, 2008 have large-sized body (i.e., Autotomiana Wunderlich, 2015 ) or complex tegular apophyses (i.e., Pholcochyrocer Wunderlich, 2008 and Spinicreber Wunderlich, 2015 ; see Wunderlich, 2012: 226–227, figs 33–37; Wunderlich, 2015: 382, figs 177–178; Wunderlich & Müller, 2020: 155, figs 147–149) and also have serrate accessory claw setae ( Wunderlich, 2015). However, Gigarachnidae Jiang & Li , fam. nov. can still be well distinguished from † Pholcochyroceridae by the presence of feathery scales and modified eye domain ( Fig. 5D ). Gigarachnidae Jiang & Li , fam. nov. resembles the other new family, † Pilosarachnidae Jiang & Li , fam. nov., by the presence of feathery scales, distinct longitudinal fovea and the absence of apophyses on all male palpal podomeres, but can be distinguished by the relative position of cymbium and bulb ( Figs 6A–C ) and the presence of AME- PME protruding tubercle ( Fig. 5D ).

The flat body, long hairs bore at the end of abdomen ( Figs 5A–B ) and PME-AME tubercle ( Fig. 5D ) of Gigarachnidae Jiang & Li , fam. nov. are unique characters in Kachin amber.

Description. Gigantic araneomorph spider from Kachin amber. Three tarsal claws, serrate accessory claw setae present ( Fig. 5C ); eight eyes, AME and PME on a common protruding tubercle, ALE and PLE on lateral tubercles ( Fig. 5D ); fovea distinct, longitudinal; feathery scales present on legs, carapace and abdomen; spines numerous on walking legs but absent on tarsi, spines forming a ring at apex of each metatarsi; paracymbium absent, tegular apophyses many and complex.

Distribution. Late Cretaceous Kachin amber, Myanmar .

Comments. The lack of cribellar information hampered further discussion on the taxonomic placement of such a remarkable family. A new conspecific specimen will definitely help, but regarding its rareness, it seems rather difficult to obtain one. Spiders of large size may be difficult to find in amber because they have a greater chance of struggling out instead of being caught, as mentioned in Wunderlich (2017). Indeed, the traces of struggle near the legs of the spider can be easily seen in the type specimen ( Figs 5A–B ).

Figures

Figure 5. Gigarachne bian Jiang & Li, gen. & sp. nov., holotype male. A. Habitus, ventral view. B. Habitus, dorsal view. C. Tarsal claws of left leg II. D. Eye domain, dorsal view. E. Mouthparts, ventral view. Scale bars: A–B=2.0mm; C=0.2 mm; D–E=1.0mm.

Figure 6. Gigarachne bian Jiang & Li, gen. & sp. nov., holotype male, right male palp.A.Apical view. B. Retrolateral view.C.Ventral view. Images horizontally flipped for the sake of comparison. Scale bars: A=0.2mm; B–C=0.5mm.