Chimerarachne yingi, copyright Bo Yang.

Belongs within: Tetrapulmonata.
Contains: Mesothelae, Mygalomorphae, Basalhaplogynae, Neocribellatae.

The Araneida are a clade of arachnids including the spiders (Araneae) and the Cretaceous Chimerarachne, united by the organisation of the openings of the silk glands into a group of spinnerets at the end of the opisthosoma, and modification of the male pedipalp as an organ for sperm transfer. Chimerarachne yingi is known from the mid-Cretaceous Burmese amber and differs from modern spiders in retaining a long terminal flagellum (Wunderlich 2019). The tarsus of the pedipalp bears a pair of apical apophyses in some but not all of the known specimens; the modified pedipalp has been interpreted as a sperm transfer organ like that of modern male spiders. Modern spiders are also characterised by the modification of the chelicerae to bear venomous fangs. In most living spiders, forming the clade Opisthothelae, all trace of external segmentation has been lost from the abdomen. The fangs are plesiomorphically parallel with one another but in members of the clade Araneomorphae they close towards the midline of the body.

Other fossil spiders may include the Pyritaraneidae, a poorly defined group of large, long-legged arachnids known from the Carboniferous of Europe.

Spiders losing their lungs
Published 21 April 2008
Hypochilus petrunkevitchi, photographed by Marshal Hedin.

Modern spiders can be divided into three suborders or infraorders or what-have-you. The Mesothelae or Liphistiomorphae (segmented spiders) are a small group distinguishable from all other spiders by their obviously segmented abdomens. The Mygalomorphae (vertical-fanged spiders) have fangs that move straight up and down, and include the trapdoor and funnel-web spiders and American tarantulas. The largest group of spiders by far is the Araneomorphae (cross-fanged spiders), with fangs angled towards each other, including orb-weavers, cobweb spiders, jumping spiders, wolf spiders, and pretty much any other spider family you’re likely to be familiar with. However, some older references may list a fourth group, the Hypochilomorphae, and it’s with the latter that we’re dealing today.

The Tasmanian cave-dwelling austrochilid Hickmania troglodytes. The four yellow spots visible on the underside correspond to the positions of the book lungs. Photo by Niall Doran from here.

The ‘hypochilomorphs’ include three small families, the Hypochilidae, Austrochilidae and Gradungulidae, that are now regarded as basal members of the Araneomorphae. Like other araneomorphs, they possess fangs that are angled towards each other rather than parallel. Where they differ from other araneomorphs is in the number of book lungs they possess. Book lungs are the ancestral respiratory structure for all arachnids, and evolved from the gills of their aquatic ancestors as they adapted to life on land. They are little more than gills recessed into the underside of the animal and covered over to prevent moisture loss, and the name “book lung” refers to their appearance in cross-section like leaves of a book. The ancestral number of book lungs in arachnids is four, though many arachnids (particularly the smaller forms, and including some spiders) have independently replaced the book lungs with tracheae, or lack any specialised respiratory structures entirely. Most araneomorphs with book lungs have lost the posterior pair and only have two book lungs. Hypochilomorphs retain the posterior pair, demonstrating their basal position to other araneomorphs and causing them to all too often be damned with the execrable title of “living fossil”. However, because this is an ancestral feature rather than a derived one, it does not indicate that hypochilomorphs form a group exclusive of other araneomorphs, and other features make it clear that Austrochiloidea (Grandungulidae and Austrochilidae) are more closely related to the other araneomorphs than they are to Hypochilidae (Griswold et al. 1999). The remaining araneomorphs have usually been presented as a single clade (the Araneoclada), though at least one species of Filistatidae, Kukulcania hibernalis, possesses posterior book lungs as a juvenile, suggesting that family lost the posterior book lungs independently of other araneomorphs, and Lopardo et al. (2004) suggested that Filistatidae may be outside the Austrochiloidea + Araneoclada clade.

The Hypochilidae are large spiders found in Asia and North America. They construct a unique web for snaring prey, often referred to as a “lampshade web” in reference to its shape, though if the description in Forster & Forster (1999) holds for all hypochilids, then the photo on the Wikipedia page for this family is quite possibly upside down. According to Forster & Forster, Hypochilus builds its web on the underside of an overhanging rock, with a tightly woven upper section flaring out around the lower circular edge. Hypochilids are mostly montane species.

Spelungula cavernicola, photographed by Paddy Ryan.

The Austrochiloidea are restricted to Southern Hemisphere continents—the Austrochilidae are found in southern South America and Tasmania, while the Gradungulidae are found in eastern Australia and the South Island of New Zealand (Forster & Forster 1999). The Austrochilidae build large horizontal webs, but many Grandungulidae have abandoned web-building and become active hunters. The Gradungulidae are characterised by the significant increase in size of one of the claws on the legs, which is used to great effect in seizing prey. In one of the Australian web-building species, the cave-dwelling Progradungula carraiensis, a long, sparse web is built between the ground and an overhang, up to and exceeding a metre in height. The spider itself sits head downwards at the base of the web, low enough that the front legs are near the ground. Any suitable prey that walks by the spider is grabbed with the front legs and bitten. The prey may be eaten where it is caught, or carried up to the top part of the web that also serves as a retreat for the spider. One of the New Zealand species, Pianoa isolata, has abandoned the web but hangs down among strands of dense moss, catching its prey in a similar manner to Progradungula. A New Zealand cave-dwelling species Spelungula cavernicola is an active hunter but often feeds on its prey suspended in mid-air from a silk dragline. The round egg-sacs are also hung from draglines, probably as protection from potential predators.

Systematics of Araneida
    |  i. s.: Antrochares macgregori Rainbow 1898 [=A. novaeguineaensis ms]M72
    |         Argentotenus devisi Rainbow 1898M72
    |         IdiommataM72
    |           |--I. crassipes Rainbow 1898M72
    |           `--I. sordida Rainbow 1898M72
    |         Mollica juncunda Rainbow 1912M72
    |--Chimerarachne Wang et al. 2018 [Chimerarachnida, Chimerarachnidae]W19
    |    `--C. yingi Wang et al. 2018W19
    `--Araneae [Arachneae, Arachnides, Aranea, Araneides, Aranina, Artharachnae, Parallelodontes]GD16
         |  i. s.: Archoleptona schusteriUB02
         |         BlabommaUB02
         |         Bryantella smaragdus (Crane 1945) [incl. Parnaenus convexus Chickering 1946]J02
         |         PterinochilusWS02
         |           |--P. carnivorus Strand 1917J98
         |           `--P. nigrofulvus (Pocock 1898)WS02
         |         TholiaKK90
         |           |--T. conifera Koch & Keyserling 1886KK90
         |           |--T. mammeata Koch & Keyserling 1886KK90
         |           |--T. peltata Koch in Koch & Keyserling 1886KK90
         |           |--T. pilosa Koch & Keyserling 1886KK90
         |           |--T. simpla Koch & Keyserling 1886KK90
         |           `--T. tuberculata Koch in Koch & Keyserling 1886KK90
         |         Ulesanis Koch 1872KK90
         |           `--U. sextuberculata Koch & Keyserling 1890KK90
         |         Wirada Keyserling 1886KK90
         |           `--W. rotunda Koch & Keyserling 1890KK90
         |         Tobesoa Koch & Keyserling 1890KK90
         |           `--*T. theridioides Koch & Keyserling 1890KK90
         |         Gmogala Koch & Keyserling 1890 [=Imogala (l. c.)]KK90
         |           `--*G. scarabaea Koch & Keyserling 1890 [=Imogala (l. c.) scarabaea]KK90
         |         Euro permundaB96
         |         Daramulunia [=Daramuliana (l. c.)]C90
         |         PyritaraneidaeD07
         |           |--Pyritaranea tubiferaF04
         |           `--Dinopilio Fritsch 1904D07, F04
         |                `--*D. gigas Fritsch 1904F04
         |         Amphitrogulus sternalis Gourret 1886D07
         |         Phalangillum hirsutum Gourret 1886D07
         |         Tidarren sisyphoidesCM07
         |         Novakia ‘trituberculata’ (Urquhart 1887) [=Epeira trituberculata non Lucas 1846]NS00
         |         Phalaea marginata Strand 1907J98
         |         Barusia maheni (Kratochvíl & Miller 1939)UO05
         |         Hadites tegenarioides Keyserling 1862UO05
         |         Ariadne Doleschall 1857D57
         |           `--*A. flagellum Doleschall 1857D57
         |         Sarinda lindaC08
         |         Perneria Fritsch 1904F04
         |           `--*P. salticoides [=Arthrolycosa salticoides]F04
         |         Pleurolycosa Fritsch 1904F04
         |           `--*P. prolifera [=Arthrolycosa prolifera]F04
         |         AcrosomaH04
         |           |--A. bifurcatumH04
         |           |--A. hexacanthumH04
         |           `--A. spinosumH04
         |         Troglodiplura lowryiY95
         |         Desidiopsis racovitzaiPP64
         |         Sanogasta backhauseniR14
         |         Cupa kalawitanaR14
         |         AcanthodonP01
         |           |--A. flaveolum Pocock 1901P01
         |           `--A. thorelliiP01
         |         HeligmomerusP01
         |           |--H. deserti Pocock 1901P01
         |           `--H. somalicusP01
         |         Thlaosoma dubiumR96
              `--Araneomorphae (see below for synonymy)JD-S07
                   |  i. s.: Phrynarachne decipiensB96
                   |         Dendrolycosa Doleschall 1859D59
                   |           `--*D. fusca Doleschall 1859D59

Araneomorphae [Antiodontes, Arachnomorphae, Araneoclada, Ecribellatae, Hypochilomorphae, Inaequitelae, Tubitelariae]JD-S07

*Type species of generic name indicated


[B96] Brunet, B. 1996. Spiderwatch: A Guide to Australian Spiders. Reed New Holland: Sydney.

[C08] Ceccarelli, F. S. 2008. Behavioral mimicry in Myrmarachne species (Araneae, Salticidae) from north Queensland, Australia. Journal of Arachnology 36 (2): 344–351.

[C90] Coddington, J. A. 1990. Book review: Advances in spider taxonomy 1981–1987: a supplement to Brignoli’s A catalogue of the Araneae described between 1940 and 1981 (edited by P. Merrett), by Norman I. Platnick. Journal of Arachnology 18: 245–248.

[CM07] Cokendolpher, J. C., & P. G. Mitov. 2007. Natural enemies. In: Pinto-da-Rocha, R., G. Machado & G. Giribet (eds) Harvestmen: The Biology of Opiliones pp. 339–373. Harvard University Press: Cambridge (Massachusetts).

[D57] Doleschall, C. L. 1857. Bijdrage tot de kennis der Arachniden van den Indischen Archipel. Natuurkundig Tijdschrift voor Nederlandsch Indië, series 3, 3 (5–6): 399–434, pls 1–2.

[D59] Doleschall, C. L. 1859. Tweede Bijdrage tot de kennis der Arachniden van den Indischen Archipel. Verhandelingen der Natuurkundige Vereeniging in Nederlandsch Indie [Acta Societatis Scientiarum Indo-Neêrlandicae] 5 (5): 1–60, pls 1–18.

[D07] Dunlop, J. A. 2007. Paleontology. In: Pinto-da-Rocha, R., G. Machado & G. Giribet (eds) Harvestmen: The Biology of Opiliones pp. 247–265. Harvard University Press: Cambridge (Massachusetts).

Forster, R. R., & L. M. Forster. 1999. Spiders of New Zealand and their Worldwide Kin. University of Otago Press: Dunedin (New Zealand), and Otago Museum: Dunedin.

[F04] Fritsch, A. 1904. Palaeozoische Arachniden. Selestverlag: Prague.

[GD16] Garwood, R. J., J. A. Dunlop, P. A. Selden, A. R. T. Spencer, R. C. Atwood, N. T. Vo & M. Drakopoulos. 2016. Almost a spider: a 305-million-year-old fossil arachnid and spider origins. Proceedings of the Royal Society of London Series B—Biological Sciences 283: 20160125.

Griswold, C. E., J. A. Coddington, N. I. Platnick & R. R. Forster. 1999. Towards a phylogeny of entelegyne spiders (Araneae, Araneomorphae, Entelegynae). Journal of Arachnology 27: 53–63.

[H04] Haeckel, E. 1899–1904. Kunstformen der Natur. Bibliographisches Institut: Leipzig und Wien.

[J98] Jäger, P. 1998. Das Typenmaterial der Spinnentiere (Arachnida: Acari, Amblypygi, Araneae, Opiliones, Pseudoscorpiones, Scorpiones, Uropygi) aus dem Museum Wiesbaden. Jahrbuecher des Nassauischen Vereins fuer Naturkunde 119: 81–91.

[J02] Jocqué, R. 2002. Genitalic polymorphism—a challenge for taxonomy. Journal of Arachnology 30 (2): 298–306.

[KK90] Koch, L., & E. Keyserling. 1884–1890. Die Arachniden Australiens nach der Natur beschrieben und abgebildet vol. 2. Bauer & Raspe: Nürnberg.

Lopardo, L., M. J. Ramírez, C. Grismado & L. A. Compagnucci. 2004. Web building behavior and the phylogeny of austrochiline spiders. Journal of Arachnology 32: 42–54.

[M72] Monroe, R. 1972. Chelicerate type-specimens in the Queensland Museum. Memoirs of the Queensland Museum 16 (2): 291–307.

[NS00] Nicholls, D. C., P. J. Sirvid, S. D. Pollard & M. Walker. 2000. A list of arachnid primary types held in Canterbury Museum. Records of the Canterbury Museum 14: 37–48.

[PP64] Peres, J. M., & J. Picard. 1964. Nouveau manuel de bionomie benthique de la mer Mediterranee. Recueil des Travaux de la Station Marine d’Endoume, Bulletin 31 (27): 5–137.

[P01] Pocock, R. I. 1901. Descriptions of some new African Arachnida. Annals and Magazine of Natural History, series 7, 7: 284–288.

[R96] Rainbow, W. J. 1896. Descriptions of some new Araneidae of New South Wales. No. 6. Proceedings of the Linnean Society of New South Wales 21 (3): 320–344, pls 18–20.

[R14] Ramírez, M. J. 2014. The morphology and phylogeny of dionychan spiders (Araneae: Araneomorphae). Bulletin of the American Museum of Natural History 390: 1–374.

[UB02] Ubick, D., & T. S. Briggs. 2002. The harvestman family Phalangodidae 4. A review of the genus Banksula (Opiliones, Laniatores). Journal of Arachnology 30 (2): 435–451.

[UO05] Ubick, D., & R. Ozimec. 2005. On the harvestman genus Lola Kratochvíl (Opiliones: Laniatores). Natura Croatica 14 (3): 161–174.

[WS02] Whitmore, C., R. Slotov, T. E. Crouch & A. S. Dippenaar-Schoeman. 2002. Diversity of spiders (Araneae) in a savanna reserve, Northern Province, South Africa. Journal of Arachnology 30 (2): 344–356.

[W19] Wunderlich, J. 2019. What is a spider? Cretaceous fossils modify strongly phylogenetics as well as diagnoses of families, superfamilies and even suborders of spiders (Araneida) and other arthropods. Beiträge zur Araneologie 12: 1–32.

[Y95] Yen, A. L. 1995. Australian spiders: an opportunity for conservation. Records of the Western Australian Museum Supplement 52: 39–47.

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