A giant spider from the Jurassic of China reveals greater diversity of the orbicularian stem group

Abstract

A large female spider, Nephila jurassica, was described from Middle Jurassic strata of north-east China and placed in the modern genus Nephila (family Nephilidae) on the basis of many morphological similarities, but, as with many ancient fossils, the single specimen lacked synapomorphies of the family (Selden et al. 2011). In order to test the placement within the nephilid phylogenetic tree, Kuntner et al. (2013) calibrated the molecular phylogeny using N. jurassica in three different scenarios based on inferred mitochondrial substitution rates. They concluded that N. jurassica fitted better as a stem orbicularian than a nephilid. Now, a giant male spider has been discovered at the same locality that yielded N. jurassica. The two sexes are considered conspecific based on their similar morphological features, size, and provenance. The male cannot be accommodated in Nephilidae because of its pedipalp morphology, so the new genus Mongolarachne and family Mongolarachnidae are erected for the species. Comparison with possibly related families show that Mongolarachnidae is most likely on the orbicularian stem, close to other cribellate orbicularians (e.g., Deinopoidea), which suggests a greater diversity of cribellate orbicularians during the Middle Jurassic.Electronic supplementary materialThe online version of this article (doi:10.1007/s00114-013-1121-7) contains supplementary material, which is available to authorized users.

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“…Selden et al. () did not present convincing evidence that these two specimens are conspecific (e.g. the male resembles Ectatosticta , a hypochilid genus endemic to China), so in our view the question of where M. jurassica belongs is still in need of further research.…”

“…However, the fossil described by Selden et al (2011) does seem to have morphological characters compatible with those of other nephilids. A male specimen described two years later was assigned to the same species (Selden et al, 2013) and because the male did not fit the Nephilidae diagnosis, the female (described as N. jurassica) and the male were placed in a new family-Mongolarachnidae. Selden et al (2013) did not present convincing evidence that these two specimens are conspecific (e.g.…”

“…A male specimen described two years later was assigned to the same species (Selden et al, 2013) and because the male did not fit the Nephilidae diagnosis, the female (described as N. jurassica) and the male were placed in a new family-Mongolarachnidae. Selden et al (2013) did not present convincing evidence that these two specimens are conspecific (e.g. the male resembles Ectatosticta, a hypochilid genus endemic to China), so in our view the question of where M. jurassica belongs is still in need of further research.…”

Peer Review #1 of "Spider phylogenomics: untangling the Spider Tree of Life (v0.1)"

“…The MRCA of Haplogynae + Hypochilidae was given a lognormal prior of (mean in real space) 278 Ma (SD=0.1) based on the fossil Eoplectreurys gertschi (Selden and Penney, 2010). The MRCA of Deinopoidea (cribellate orb-weavers) was given a lognormal prior of (mean in real space) 195 Ma (SD=0.3) based on the fossil Mongolarachne jurassica (Selden et al, 2013). The MRCA of ecribellate orb-weavers was given a lognormal prior of (mean in real space) Ma (SD=0.4) based on the fossil Mesozygiella dunlopi (Penney and Ortuño, 2006).…”

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“…The MRCA of Haplogynae + Hypochilidae was given a lognormal prior of (mean in real space) 278 Ma (SD=0.1) based on the fossil Eoplectreurys gertschi (Selden and Penney, 2010). The MRCA of Deinopoidea (cribellate orb-weavers) was given a lognormal prior of (mean in real space) 195 Ma (SD=0.3) based on the fossil Mongolarachne jurassica (Selden et al, 2013). The MRCA of ecribellate orb-weavers was given a lognormal prior of (mean in real space) 168…”