''Mongolarachne'' is an
extinct
Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
genus
Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of
spider
Spiders (order (biology), order Araneae) are air-breathing arthropods that have eight limbs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude spider silk, silk. They are the largest order of arachnids and ran ...
s placed in the
monogeneric family Mongolarachnidae. The genus contains only one species, ''Mongolarachne jurassica'', described in 2013, which is presently the largest fossilized spider on record.
The type species was originally described as ''Nephila jurassica'' and placed in the living genus ''
Nephila'' which contains the
golden silk orb-weavers.
Subsequently it was determined to be
stem
Stem or STEM most commonly refers to:
* Plant stem, a structural axis of a vascular plant
* Stem group
* Science, technology, engineering, and mathematics
Stem or STEM can also refer to:
Language and writing
* Word stem, part of a word respon ...
-orbicularian, i.e. a relative of the group
Orbiculariae, which contains the family Nephilidae, but also several other families, such as
Theridiidae
Theridiidae, also known as the tangle-web spiders, cobweb spiders and comb-footed spiders, is a large family of Araneomorphae, araneomorph spiders first described by Carl Jakob Sundevall in 1833. This diverse, globally distributed family includes ...
,
Theridiosomatidae or
Uloboridae.
The species is known only from the
Middle Jurassic
The Middle Jurassic is the second Epoch (geology), epoch of the Jurassic Period (geology), Period. It lasted from about 174.1 to 161.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relativel ...
Jiulongshan Formation, part of the
Daohugou Beds, near the village of
Daohugou in
Ningcheng County
Ningcheng County ( Mongolian: ; zh, s=宁城县) is a county of southeastern Inner Mongolia, China, bordering Liaoning province to the east. It is under the administration of Chifeng City.
The daohugouthallus extinct genus of lichen was found ...
, northeastern
China
China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
.
A second putative species, ''
Mongolarachne chaoyangensis'', was described in 2019,
but it was subsequently shown to be a forgery based on a fossil
crayfish
Crayfish are freshwater crustaceans belonging to the infraorder Astacidea, which also contains lobsters. Taxonomically, they are members of the superfamilies Astacoidea and Parastacoidea. They breathe through feather-like gills. Some spe ...
.
Jorg Wunderlich placed ''
Longissipalpus'' and ''
Pedipalparaneus'' from the
Cenomanian
The Cenomanian is, in the International Commission on Stratigraphy's (ICS) geological timescale, the oldest or earliest age (geology), age of the Late Cretaceous epoch (geology), Epoch or the lowest stage (stratigraphy), stage of the Upper Cretace ...
aged
Burmese amber
Burmese amber, also known as Burmite or Kachin amber, is amber from the Hukawng Valley in northern Myanmar. The amber is dated to around 100 million years ago, during the latest Albian to earliest Cenomanian ages of the mid-Cretaceous period. Th ...
into Mongolarachnidae in 2015.
[J. Wunderlich. 2015. On the evolution and the classification of spiders, the Mesozoic spider faunas, and descriptions of new Cretaceous taxa mainly in amber from Myanmar (Burma) (Arachnida: Araneae). ''Mesozoic Spiders (Araneae): Ancient Spider Faunas and Spider Evolution, Beiträge zur Araneologie'' 9:21-408]
History and classification
''Mongolarachne jurassica'' is known only from two fossils, the
holotype
A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...
, 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 fossil
A compression fossil is a fossil preserved in sedimentary rock that has undergone physical compression. While it is uncommon to find animals preserved as good compression fossils, it is very common to find plants preserved this way. The reason f ...
s in a pale grey finely laminated sedimentary
tuff
Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock co ...
.
The fossil specimens are from outcrops of the Jiulongshan Formation exposed in the Wuhua Township. The type specimens is currently preserved in the
Key Lab of Insect Evolution & Environmental Changes collections housed in the
Capital Normal University, located in
Beijing
Beijing, Chinese postal romanization, previously romanized as Peking, is the capital city of China. With more than 22 million residents, it is the world's List of national capitals by population, most populous national capital city as well as ...
,
China
China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
. ''Mongolarachne jurassica'' was first studied by Paul Selden of the
University of Kansas
The University of Kansas (KU) is a public research university with its main campus in Lawrence, Kansas, United States. Two branch campuses are in the Kansas City metropolitan area on the Kansas side: the university's medical school and hospital ...
and the
Natural History Museum
A natural history museum or museum of natural history is a scientific institution with natural history scientific collection, collections that include current and historical records of animals, plants, Fungus, fungi, ecosystems, geology, paleo ...
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
''Biology Letters'' is a peer-reviewed scientific journal published by the Royal Society, established in 2005. It focuses on the rapid publication of short research articles, reviews, and opinion pieces across the biological sciences. The editor-in ...
''. The
etymology
Etymology ( ) is the study of the origin and evolution of words—including their constituent units of sound and meaning—across time. In the 21st century a subfield within linguistics, etymology has become a more rigorously scientific study. ...
of the
specific epithet
In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...
''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
The Priabonian is, in the International Commission on Stratigraphy, ICS's geologic timescale, the latest age (geology), age or the upper stage (stratigraphy), stage of the Eocene epoch (geology), Epoch or series (stratigraphy), Series. It spans ...
species ''
Nephila pennatipes'' from
Colorado
Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...
's
Florissant Formation. The oldest recognized member of the family Nephilidae is the
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...
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
In phylogenetics, an apomorphy (or derived trait) is a novel Phenotypic trait, character or character state that has evolution, evolved from its ancestral form (or Plesiomorphy and symplesiomorphy, plesiomorphy). A synapomorphy is an apomorphy sh ...
".
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
The holotype female is fossilized with her underside facing up. Portions of all but two of the legs are missing from the fossil. The carapace of the holotype is and the
opisthosoma
The opisthosoma is the posterior part of the body in some arthropods, behind the prosoma ( cephalothorax). It is a distinctive feature of the subphylum Chelicerata (arachnids, horseshoe crabs and others). Although it is similar in most respects ...
is . The total body-length is approximately while the front legs reach about in length. This puts ''M. jurassica'' females in the same size-range as modern females of ''Nephila'', and makes ''M. jurassica'' the largest described fossil spider.
The tibia of the third leg features tufts of
setae called gaiters, which are also found on the other three tibia. The feature of a gaiter on the third tibia is found only in modern ''Nephila'' and, according to the original authors of description of ''M. jurassica'', its presence along with the large size indicated the species was part of the genus.
The allotopotype male has a body length of with elongated
pedipalp
Pedipalps (commonly shortened to palps or palpi) are the secondary pair of forward appendages among Chelicerata, chelicerates – a group of arthropods including spiders, scorpions, horseshoe crabs, and sea spiders. The pedipalps are lateral to ...
s.
See also
*
Goliath birdeater
The Goliath birdeater (''Theraphosa blondi'') belongs to the tarantula
Tarantulas comprise a group of large and often hairy spiders of the family Theraphosidae. , 1,100 species have been identified, with 166 genera. The term "tarantula" ...
(''Theraphosa blondi''), largest known spider in the world by mass
*
Giant huntsman spider, largest known spider in the world by leg span
* ''
Cerbalus aravaensis'', a huntsman spider found in Israel and Jordan
References
External links
Biggest Fossil Spider Found
{{Taxonbar, from1=Q22950039, from2=Q32999707
Jurassic arachnids
Fossil taxa described in 2011
Araneomorphae
Prehistoric animals of China
Monotypic prehistoric spider genera
Monotypic Araneomorphae genera
Middle Jurassic arthropods
Mesozoic arthropods of Asia
Middle Jurassic animals of Asia