Synspermiata is a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...

araneomorph The Araneomorphae (also called the Labidognatha) are an infraorder of spiders. They are distinguishable by chelicerae (fangs) that point diagonally forward and cross in a pinching action, in contrast to the Mygalomorphae (tarantulas and their ...

spider Spiders (order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species ...

s, comprising most of the former " haplogynes". They are united by having simpler genitalia than other araneomorph spiders, lacking a

cribellum Cribellum literally means "little sieve", and in biology the term generally applies to anatomical structures in the form of tiny perforated plates. In certain groups of diatoms it refers to microscopically punctured regions of the frustule, or o ...

, and sharing an evolutionary history of synspermia – a particular way in which

spermatozoa A spermatozoon (; also spelled spermatozoön; ; ) is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote. (A zygote is a single cell, with a complete set of chromos ...

are grouped together when transferred to the female.

Synspermia

Spermatozoa A spermatozoon (; also spelled spermatozoön; ; ) is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote. (A zygote is a single cell, with a complete set of chromos ...

are produced in a multi-step process. A primary spermatocyte with the full diploid number of

chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins ar ...

s divides to form two secondary spermatocytes which are haploid, i.e. each has half the diploid number of chromosomes. Each secondary spermatocyte then divides to produce two spermatids which undergo further development to form spermatozoa. In synspermia, two or more spermatids from the same spermatocyte fuse together and are enclosed in an envelope, forming a "capsule". This contrasts with cleistospermia, where the capsules enclose individual spermatozoa. After transfer to the female in either form, decapsulation and activation are necessary before the resulting spermatozoa can fertilize eggs.

Phylogeny

In 2014, Peter Michalik and Martín Ramírez published a study of the morphology of the reproductive system of male spiders, including their spermatozoa. They found a

within haplogyne spiders, Synspermatia, characterized by the absence of a

and the

synapomorphy In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to hav ...

(shared derived character) of synspermia. Not all members of the clade exhibit synspermia, since it has evolved into cleistospermia multiple times and Telemidae have individually encapsulated sperm cells arranged in densely packed stacks. A much larger

molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

study published in 2016 also found Synspermatia to be a clade, grouping with the families

Hypochilidae Lampshade spiders, family Hypochilidae, are among the most primitive of araneomorph spiders. There are two genera and twelve species currently recognized. Like mygalomorphs, most hypochilids have two pairs of book lungs, but like araneomorphs the ...

and

Filistatidae Crevice weaver spiders (Filistatidae) comprise cribellate spiders with features that have been regarded as " primitive" for araneomorph spiders. They are weavers of funnel or tube webs. The family contains 18 genera and more than 120 described sp ...

at the base of

Araneomorphae The Araneomorphae (also called the Labidognatha) are an infraorder of spiders. They are distinguishable by chelicerae (fangs) that point diagonally forward and cross in a pinching action, in contrast to the Mygalomorphae (tarantulas and their ...

Families

Families placed in Synspermiata are: *

Caponiidae Caponiidae is a family of ecribellate haplogyne spiders that are unusual in a number of ways. They differ from other spiders in lacking book lungs and having the posterior median spinnerets anteriorly displaced to form a transverse row with the a ...

Diguetidae Coneweb spiders (Diguetidae) are six-eyed haplogyne spiders that live in tangled space webs, fashioning a cone-like central retreat where they hide and lay eggs. It is a small family, containing only two genera with fifteen species and is conf ...

* Drymusidae *

Dysderidae Dysderidae, also known as woodlouse hunters, sowbug-eating spiders, and cell spiders, is a family of araneomorph spiders first described by Carl Ludwig Koch in 1837. They are found primarily in Eurasia, extending into North Africa with very few ...

Ochyroceratidae Ochyroceratidae is a six-eyed spider family, with 165 described species in ten genera. They are common inhabitants of caves and the tropical forest litter of South Africa, the Caribbean, Asia and South America. Considered an ecological counterpar ...

Oonopidae Oonopidae, also known as goblin spiders, is a family of spiders consisting of over 1,600 described species in about 113 genera worldwide, with total species diversity estimated at 2000 to 2500 species. The type genus of the family is ''Oonops'' Ke ...

* Orsolobidae *

Pacullidae Pacullidae is a family of araneomorph spiders first described by Eugène Simon in 1894. It was merged into Tetrablemmidae in 1958, then raised back to family status after a large phylogenetic study in 2017. Description The family Pacullidae cont ...

Periegopidae ''Periegops'' is a genus of spiders with six eyes instead of the usual eight. It is the only genus in its family (Periegopidae) and has three described species. It was long considered to be members of Sicariidae or Segestriidae until Raymond For ...

* Pholcidae *

Plectreuridae Plectreuridae, also called plectreurid spiders, is a small spider family confined to the Southwestern United States, Mexico, and the Caribbean. Only two living genera are known—the nominate genus '' Plectreurys'' and '' Kibramoa''. In the past, ...

Scytodidae Spitting spiders (Scytodidae) is a family of araneomorph spiders first described by John Blackwall in 1864. It contains over 250 species in five genera, of which '' Scytodes'' is the best-known. Description Like recluse spiders and coneweb sp ...

Segestriidae Tube-dwelling spiders (Segestriidae) are a family of araneomorph spiders first described by Eugène Simon in 1893. It consists of five genera, two large and widespread, '' Segestria'' and '' Ariadna'', and three smaller genera, '' Citharoceps' ...

Sicariidae Sicariidae is a family of six-eyed venomous spiders known for their potentially necrotic bites. The family consists of three genera and about 160 species. Well known spiders in this family include the brown recluse spider and the six-eyed sand ...

* Telemidae *

Tetrablemmidae Tetrablemmidae, sometimes called armored spiders, is a family of tropical araneomorph spiders first described by Octavius Pickard-Cambridge in 1873. It contains 126 described species in 29 genera from southeast Asia, with a few that occur in Afri ...

Trogloraptoridae ''Trogloraptor'' is a genus of large spiders found in the caves of southwestern Oregon. It is the sole genus in the family Trogloraptoridae, and includes only one species, ''Trogloraptor marchingtoni''. These spiders are predominantly yello ...

Extinct families

† Eopsilodercidae (Telemidae was not included in the analysis by Wheeler et al., but is placed in Synspermiata in other studies.

References

{{Taxonbar, from=Q30681442 Araneomorphae