Eoplectreurys
Encyclopedia
Eoplectreurys is an extinct monotypic
genus
of spider
from the family Plectreuridae, with a sole species, Eoplectreurys gertschi. The fossils of Eoplectreurys were recovered from the 165 Ma old Middle Jurassic
Daohugou formation tuffs in Inner Mongolia
, China
.
are deposited in the Nanjing Institute of Geology and Palaeontology
with the genus being described from a total of seven adult spiders. Eoplectreurys was first studied and described by Drs Paul Selden and Diying Huang, who published their type description in the journal Naturwissenschaften in 2010. The genus name is a combination of the Greek
word eos which means "dawn", and Plectreurys the name of the modern genus which the fossils closely resemble.
Eoplectreurys is considered the oldest described spider genus of the Haplogynae series
, predating the described Haplogynae spiders from Cretaceous
ambers in Jordan
and Lebanon
, and is the oldest member of Plectreuridae. The two other Plectreuridae species described from fossils are both known from specimens preserved in amber with Palaeoplectreurys baltica from Eocene Baltic amber
and Plectreurys pittfieldi from early Miocene
Dominican amber
. The modern distribution of Plectreuridae is restricted to Southwestern North America
, Central America
, and parts of the Greater Antilles
. The current restricted range of the family may be due to either the severe cooling at the Eocene
-Oligocene
transition or the Pliocene
-Pleistocene
ice age.
s in the fine-grained lacustrian rocks and thus have been flattened from their dimensions in life. Due to the lack of exterior genitalia on females, it is very difficult to identify possible Eoplectreurys females from among the number of Haplogynae spiders found in the Daohugou formation. Only one specimen is a possible match, having a carapace which is round as in the Eoplectreurys males, while the other known Haplogynae female specimens possess elongated carapaces. Only one other family of spiders, Segestriidae, is similar to the fossils. However the legs of Segestriidae have more spines than the fossils and the overall carapace shape of Segestriids is elongated, with maxillae which do not meet in front of the labium. On average Eoplectreurys was a small spider with the average body length, not including legs, being 3 millimetre (0.3 cm). The fossils display fused chelicerae
, distinctly short legs, and are ecribellate, that is, without the silk spinning organ called a cribellum
. The number of eyes is not distinguishable in the fossils and the stridulating file which is found on the pedipalp
s are not apparent or not present. Eoplectreurys is most similar in structure to the P. tristis group of Plectreurys.
The species lived around a lake in a volcanically active area and was found in fine-grained volcanic ash
lacustrine (lake-bed) deposits, the ash helping to preserve the specimens.
Monotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...
genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of spider
Spider
Spiders are air-breathing arthropods that have eight legs, and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms...
from the family Plectreuridae, with a sole species, Eoplectreurys gertschi. The fossils of Eoplectreurys were recovered from the 165 Ma old Middle Jurassic
Middle Jurassic
The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from 176-161 million years ago. In European lithostratigraphy, rocks of this Middle Jurassic age are called the Dogger....
Daohugou formation tuffs in Inner Mongolia
Inner Mongolia
Inner Mongolia is an autonomous region of the People's Republic of China, located in the northern region of the country. Inner Mongolia shares an international border with the countries of Mongolia and the Russian Federation...
, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
.
History and classification
The type specimensHolotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
are deposited in the Nanjing Institute of Geology and Palaeontology
Chinese Academy of Sciences
The Chinese Academy of Sciences , formerly known as Academia Sinica, is the national academy for the natural sciences of the People's Republic of China. It is an institution of the State Council of China. It is headquartered in Beijing, with institutes all over the People's Republic of China...
with the genus being described from a total of seven adult spiders. Eoplectreurys was first studied and described by Drs Paul Selden and Diying Huang, who published their type description in the journal Naturwissenschaften in 2010. The genus name is a combination of the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
word eos which means "dawn", and Plectreurys the name of the modern genus which the fossils closely resemble.
Eoplectreurys is considered the oldest described spider genus of the Haplogynae series
Haplogynae
The Haplogynae are a series of araneomorph spiders.Unlike the Entelegynae, they lack hardened female genitalia .Most of the species within this group have six eyes, as opposed to most other spiders...
, predating the described Haplogynae spiders from Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
ambers in Jordan
Jordan
Jordan , officially the Hashemite Kingdom of Jordan , Al-Mamlaka al-Urduniyya al-Hashemiyya) is a kingdom on the East Bank of the River Jordan. The country borders Saudi Arabia to the east and south-east, Iraq to the north-east, Syria to the north and the West Bank and Israel to the west, sharing...
and Lebanon
Lebanon
Lebanon , officially the Republic of LebanonRepublic of Lebanon is the most common term used by Lebanese government agencies. The term Lebanese Republic, a literal translation of the official Arabic and French names that is not used in today's world. Arabic is the most common language spoken among...
, and is the oldest member of Plectreuridae. The two other Plectreuridae species described from fossils are both known from specimens preserved in amber with Palaeoplectreurys baltica from Eocene Baltic amber
Baltic amber
The Baltic region is home to the largest known deposit of amber, called Baltic amber or succinite, with about 80% of the world's known amber found there. It dates from 44 million years ago...
and Plectreurys pittfieldi from early Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
Dominican amber
Dominican amber
Dominican amber is amber from the Dominican Republic. Resin from the extinct species Hymenaea protera is the source of Dominican amber and probably of most amber found in the tropics....
. The modern distribution of Plectreuridae is restricted to Southwestern North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, Central America
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...
, and parts of the Greater Antilles
Greater Antilles
The Greater Antilles are one of three island groups in the Caribbean. Comprising Cuba, Jamaica, Hispaniola , and Puerto Rico, the Greater Antilles constitute almost 90% of the land mass of the entire West Indies.-Greater Antilles in context :The islands of the Caribbean Sea, collectively known as...
. The current restricted range of the family may be due to either the severe cooling at the Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
-Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
transition or the Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
-Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
ice age.
Description
The specimens of Eoplectreurys are preserved as compression fossilCompression 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...
s in the fine-grained lacustrian rocks and thus have been flattened from their dimensions in life. Due to the lack of exterior genitalia on females, it is very difficult to identify possible Eoplectreurys females from among the number of Haplogynae spiders found in the Daohugou formation. Only one specimen is a possible match, having a carapace which is round as in the Eoplectreurys males, while the other known Haplogynae female specimens possess elongated carapaces. Only one other family of spiders, Segestriidae, is similar to the fossils. However the legs of Segestriidae have more spines than the fossils and the overall carapace shape of Segestriids is elongated, with maxillae which do not meet in front of the labium. On average Eoplectreurys was a small spider with the average body length, not including legs, being 3 millimetre (0.3 cm). The fossils display fused chelicerae
Chelicerae
The chelicerae are mouthparts of the Chelicerata, an arthropod subphylum that includes arachnids, Merostomata , and Pycnogonida . Chelicerae are pointed appendages which are used to grasp food, and are found in place of the chewing mandibles most other arthropods have...
, distinctly short legs, and are ecribellate, that is, without the silk spinning organ called a cribellum
Cribellum
The cribellum is a silk spinning organ found in certain spiders. Unlike normal spinnerets, the cribellum consists of one or more plates covered in thousands of tiny spigots. These spigots produce extremely fine fibers which are combed out by the spider's calamistrum, producing silk with a wooly...
. The number of eyes is not distinguishable in the fossils and the stridulating file which is found on the pedipalp
Pedipalp
Pedipalps , are the second pair of appendages of the prosoma in the subphylum Chelicerata. They are traditionally thought to be homologous with mandibles in Crustacea and insects, although more recent studies Pedipalps (commonly shortened to palps or palpi), are the second pair of appendages of the...
s are not apparent or not present. Eoplectreurys is most similar in structure to the P. tristis group of Plectreurys.
The species lived around a lake in a volcanically active area and was found in fine-grained volcanic ash
Volcanic ash
Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...
lacustrine (lake-bed) deposits, the ash helping to preserve the specimens.