Origin of spiders and their spinning organs illuminated by mid-Cretaceous amber fossils

29 Pages·2017·6.18 MB·English

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https://doi.org/10.1038/s41559-018-0475-9
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Origin of spiders and their spinning organs
illuminated by mid-Cretaceous amber fossils
Diying Huang   1*, Gustavo Hormiga2, Chenyang Cai3, Yitong Su1, Zongjun Yin1, Fangyuan Xia4 and
Gonzalo Giribet   5*
1State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing,
China. 2Department of Biological Sciences, The George Washington University, Washington, DC, USA. 3Key Laboratory of Economic Stratigraphy and
Palaeogeography, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China. 4Lingpoge Amber Museum, Shanghai,
China. 5Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA.
*e-mail: [email protected]; [email protected]
Nature eCOlOGY & evOlutiON | www.nature.com/natecolevol
© 2018 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.
Supplementary Information:

Origin of spiders and their spinning organs illuminated by mid-Cretaceous amber
fossils

Diying Huang1,*, Gustavo Hormiga2, Chenyang Cai4, Yitong Su1, Zongjun Yin1, Fangyuan Xia3,
Gonzalo Giribet5,*

Arthropoda; Chelicerata; Arachnida; Serikodiastida; Uraraneida (total group)
Chimerarachne yingi Wang et al., 2018 (Figs. 1–3, Suppl. Figs. 1–11)

Description
Specimen NIGP167161 (Nanjing Institute of Geology and Palaeontology, CAS, Nanjing), male. Total body
length ca. 1.92 (excluding flagellum). Abdomen ca. 0.94 long, 0.45 wide. Carapace projecting anteriorly,
longer than wide, with a smoothly undulate margin, and subtle radial furrows but no discernible fovea.
Six eyes medially located near the anterior margin of the carapace, an anterior larger pair juxtaposed to
a posterior row of four eyes of smaller diameter (Fig. 2a,f, 3a). Labium a narrow rectangular plate,
sternum peltate, longer than wide. Chelicerae subchelate, orthognathous (Fig. 2b); paturon ectally
bearing cuticular striae (comb) (Fig. 1c, Suppl. Fig. 3e). Legs with paired pectinated tarsal claws (Suppl.
Fig. 3f), bearing a small median claw. Legs with macrosetae and numerous smaller setae (Figs. 1e, 1g),
with a long distal metatarsal trichobothrium (Fig. 1e; red arrow). Pedipalps with a robust cylindrical tibia
with 3 strong ventromesal macrosetae and a modified tarsus with a conical base, a distal part
differentially sclerotized and bearing apophyses and macrosetae, including a large apical, slightly curved,
macroseta; macrosetae absent from the less sclerotized region (Fig. 1b,d, Suppl. Fig. 2d). Abdomen
longer than wide (Suppl. Fig. 10a, b, c), with six segments in addition to a pedicel and four pairs of
spinnerets, a three-segmented pygidium and a long and thin flagellum at least twice the body length,
with more than 70 articles bearing numerous long setae. A small transversal plate is visible along the
mid posterior margin of the first conspicuous ventral abdominal segment (Fig. 2e, h, Suppl. Fig 2a).
Flagellar ornamentation varying from basal to apical region. Anterior lateral (ALS) and posterior lateral
spinnerets (PLS) long and multi-articulated, anterior median spinnerets as two juxtaposed median knobs
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at the posterior margin of the fourth opisthosomal segment (Fig. 2c); PLS similar to ALS in length and
degree of articulation (with 14 and 12 articles, respectively), distally decreasing in diameter, with the
basal article being significantly longer and wider, and the apical ones being very small (Figs. 1g, 1h, 2a–
d). Spinneret articles mesoventrally bearing long spigots (ca. 10 micrometres in diameter) with a
distinctive raised base (most easily observed in distal half of the PLS). Posterior median spinnerets very
small, barely discernible.
Other measurements (lengths). Pedipalp: Femur 0.38, Patella 0.13, Tibia 0.26, Tarsus 0.35. Leg I:
Femur 0.68, Patella 0.22, Tibia 0.46, Metatarsus 0.32, Tarsus 0.31. Leg II: Femur 0.54, Patella 0.17, Tibia
0.32, Metatarsus 0.33, Tarsus 0.34. Leg III: Femur 0.50, Patella 0.17, Tibia 0.41, Metatarsus 0.31, Tarsus
0.35. Anterior lateral spinnerets ca. 0.56; posterior spinnerets 0.59.

Specimen NIGP167162 (Nanjing Institute of Geology and Palaeontology, CAS, Nanjing), male. Somatic
morphology (Suppl. Figs. 9a–g), including pedipalps, similar to that of specimen NIGP167161.
Measurements: Total body length ca. 2.08 (excluding flagellum). Abdomen ca. 1.19 long, flagellum +
pygidium ca. 5.61 long. Carapace 0.89 long, 0.67 wide. Pedipalp (left/right): Femur 0.37/0.31, Patella
0.15/0.17, Tibia (left) 0.18. Leg I (left/right): Femur 0.67/0.67, Patella + Tibia (left) 0.74, Patella (right)
0.22, Tibia (right) 0.53, Metatarsus 0.39/0.26, Tarsus 0.35/0.22.

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Supplementary figure 1 | Micro-CT reconstructions of Chimerarachne yingi (NIGP167161). a, detail of
prosoma in anterior view; arrows identify the eyes. b, detail of the spinnerets’ proximal region with
anterior median (red arrows). c, detail of prosoma in ventrolateral view; red arrows point at cheliceral
fangs. d, ventral view of prosoma. e, frontal view of whole body. Scale bars represent 0.5 mm in a–c, 0.2
mm in d–e.

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Supplementary figure 2 | Micro-CT reconstructions of Chimerarachne yingi (NIGP167161). a–b, detail
of anterior median spinnerets (red arrows) with different angles. c, f, transverse section showing the
anterior median spinneret (red arrow) and spinneret on basal segment of posterior lateral spinneret
(blue arrow). d, e, corresponding c, showing the cutting section. Scale bars represent 0.1 mm in a, b, f,
0.2 mm in c, 0.5 mm in d and e.
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Supplementary Figure 3 | Fluorescence images of Chimerarachne yingi (NIGP167161). a, general
habitus of body in ventral view. b, general habitus of body in dorsal view. c, detail of prosomal sternal
region. d, details of pedipalp and leg I. e, detail of chelicerae in ventral view with possible stridulatory
striae. f, details of tarsal claws. d, details of leg 1 and pedipalp. Scale bars represent 0.5 mm in a, b, 0.2
mm in c, d, f, 0.1 mm in e.
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Supplementary Figure 4 | Light micrographs (a–c) and fluorescence images (d) of Chimerarachne yingi
(NIGP167161) showing the details of pedipalps. Scale bars represent 0.2 mm in a, c, d, and 0.1 mm in b.

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Supplementary Figure 5 | Light micrograph and fluorescence image of Chimerarachne yingi
(NIGP167161) showing details on leg setae. a, right leg 3, red arrow indicating the apical spurs on
metatarsus, black arrow indicating a trichobothrium. b, right leg 1, black arrow indicating a metatarsal
trichobothrium. Scale bars represent 0.2 mm.

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Supplementary Figure 6 | Light micrographs of recent Liphistius sp. (a) and Chimerarachne yingi
(NIGP167161) (b, c) showing details of spinnerets. a, paired spinnerets of recent Liphistius sp. (GH2776,
male from northern Thailand), red arrow indicating anterior and posterior lateral spinnerets, blue arrow
indicating the anterior and posterior median spinnerets. b, anterior and posterior lateral spinnerets (red
arrows), the small anterior and posterior median spinnerets (blue arrows). c, enlargement of b. Scale
bars represent 0.5 mm in a, 0.1 mm in b and c.
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Supplementary Figure 7 | Light micrographs of Chimerarachne yingi (NIGP167161) showing details of
spinnerets. a, spigots on right anterior lateral spinneret (blue arrows), spigots on posterior lateral
spinnerets (red arrows). b, detail of pygidium and spinnerets. Scale bars represent 0.1 mm.

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