Mongolarachne jurassica is known only from two fossils, the
holotype, specimen number "CNU-ARA-NN2010008" which is a mostly complete adult female and the later described
allotopotype male, number CNU-ARA-NN2011001-1 (part) and CNU-ARA-NN20110001-2 (counterpart). The individuals are preserved as
compression fossils in a pale grey finely laminated sedimentary
tuff. The fossil specimens are from outcrops of the Jiulongshan Formation exposed in the Wuhua Township. The type specimens are currently preserved in the
Key Lab of Insect Evolution & Environmental Changes collections housed in the
Capital Normal University, located in
Beijing,
China.
Mongolarachne jurassica was first studied by Paul Selden of the
University of Kansas and the
Natural History Museum along with Dong Ren and ChungKun Shih both of the Capital Normal University. Their 2011
type description of the genus and species was published online in the journal
Biology Letters. The
etymology of the
specific epithet jurassica refers to the age of the species. The genus name
Mongolarachne is derived from (
Inner) Mongolia, where the fossils were found, and the Latin
arachne meaning "spider". The family name is a derivative of the genus name. If it had been confirmed, placement of
Mongolarachne jurassica in the genus
Nephila would have made it the oldest described species of the genus
Nephila, extending the known fossil range of the genus back 130 million years. and making
Nephila the longest lived modern spider genus known. However, with the removal of
M. jurassica the oldest species in
Nephila is again the
Late Eocene species
Nephila pennatipes from
Colorado's
Florissant Formation. The oldest recognized member of the family Nephilidae is the
Cretaceous species
Cretaraneus vilaltae of Spain. Fossils of female specimens are known only from
N. pennatipes, all other fossil nephilids having been described from male specimens. The placement of
M. jurassica was first questioned by Kuntner
et al. in 2013, who claimed that
M jurassica differs from extant members of the genus
Nephila in many anatomical traits and cannot be assigned to this genus, or indeed to the family Nephilidae. According to Kuntner
et al. (2013) in an academic conference presentation following the description of the species Paul Selden (the first author of the description of
M. jurassica) suggested that
M. jurassica might be
cribellate; if confirmed this would have made it the only known cribellate member of
Nephila and the only known cribellate
araneoid. Kuntner
et al. themselves considered the presence of cribellum to be a piece of evidence that
M. jurassica was not in fact a nephilid. The authors suggested that
M. jurassica lacked a striated cheliceral boss, which the authors considered to be "a key nephilid
synapomorphy". The authors considered it more likely that this species is actually a stem-orbicularian. This assessment was confirmed later in 2013 by Paul Selden, ChungKun Shih, and Dong Ren, with the description of a male
M. jurassica which has notably different pedipalp morphology from that of male
Nephila. The authors moved the species to the new genus
Mongolarachne, which they assigned to a separate family Mongolarachnidae. The authors considered it most likely that
M. jurassica is a stem-orbicularian, more distantly related to the group
Araneoidea (including nephilids) than
deinopids and
uloborids are. ==Description==