Microstigmatid Spiders - Family: Microstigmatidae
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The Microstigmatidae are a small family of 38 species in 11 genera. It was elevated from subfamily (in Dipluridae) to family status only in 1981 by R.J Raven and N.I. Platnick who, in their concise publication of that date also attempted to establish some order in family. In 2019 they were divided into two subfamilies The current division into 11 genera was suggested only in 2022 by Montes de Oca eta al. What stands out from all the recent phylogenetic studies is that identification to genus level is very difficult for most and identification to species level near impossible - particularly for some of the tiny South American species - for lay-persons, the features one needs to look for often requiring specialist knowledge and equipment.
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Microstigmatids can be anything from tiny to large with the local contingent usually ranging towards the larger end. The Northern Rivers is home to at least seven species from two genera. The usual colour scheme is dark-browns and or black with some species displaying muddy reds as well and there are the occassional light-brown species as well. They are named to highlight the small, round openings of their booklungs, 'micro' meaning small and 'stigmata' meaning openings. In the past this feature was used to diagnose the family but with the addition of the genera Pseudonemesia, Spelocteniza and later, Envia, it can not be used as a defining feature anymore. Until further research is done, no defining features are recognised at present.
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Microstigmatids tend to be ground spiders spending much of their time roaming throught the leaf litter on the forest floor although the Australian species dig burrows for themselves. Their use of silk is very limited and they do not create webs. The eyes are very closely set and some species are quite aggressive. Currently two subfamilies are recognised and the Australian species appear to be limited to an area between just south of Sydney to 100 kilometers or so north of Brisbane.
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Subfamily: Stigmatinae
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Ixamatus broomi
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Ixamatus caldera
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Volcanic Ground Spider - Ixamatus candidus
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Ixamatus fischeri (possible occurrence)
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Ixamatus musgravei
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Ixamatus webbae
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Xamiatus kia
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Taxonomy:
Phylum: Arthropoda (Arthropods)
> Subphylum: Chelicerata (Chelicerates)
> Class: Arachnida (Arachnids)
> Order: Aranea (Spiders)
> Suborder: Mygalomorphae (Mygalomorphs)
> Superfamily: Avicularioidea
> Family: Microstigmatidae (Microstigmatid Spiders)
> Subfamily: Stigmatinae
> Genus: Ixamatus
> Species: I. broomi
> Species: I. caldera
> Species: I. candidus - Volcanic Ground Spider
> Species: I. fischeri ^
> Species: I. musgravei
> Species: I. webbae
> Genus: Xamiatus
> Species: X. kia
* = likely
^ = possibly
References and links:
> Montes de Oca, L., Indicatti, R.P., Opatova, V., Almeida, M., Pérez-Miles, F. and Bond, J.E., (2022). 'Phylogenomic analysis, reclassification, and evolution of South American nemesioid burrowing mygalomorph spiders.' Molecular Phylogenetics and Evolution 168(107377): 1-19.
> Opatova, V., Hamilton, C.A., Hedin, M., Montes de Oca, L., Král, J. and Bond, J.E., (2020). 'Phylogenetic systematics and evolution of the spider infraorder Mygalomorphae using genomic scale data.' Systematic Biology 69(4): 671-707. doi:10.1093/sysbio/syz064
> Raven, R.J. and Platnick, N.I., (1981). 'A revision of the American spiders of the family Microstigmatidae (Araneae, Mygalomorphae).' American Museum Novitates 2707: 1-20.
https://wsc.nmbe.ch/family/56/Microstigmatidae
> Montes de Oca, L., Indicatti, R.P., Opatova, V., Almeida, M., Pérez-Miles, F. and Bond, J.E., (2022). 'Phylogenomic analysis, reclassification, and evolution of South American nemesioid burrowing mygalomorph spiders.' Molecular Phylogenetics and Evolution 168(107377): 1-19.
> Opatova, V., Hamilton, C.A., Hedin, M., Montes de Oca, L., Král, J. and Bond, J.E., (2020). 'Phylogenetic systematics and evolution of the spider infraorder Mygalomorphae using genomic scale data.' Systematic Biology 69(4): 671-707. doi:10.1093/sysbio/syz064
> Raven, R.J. and Platnick, N.I., (1981). 'A revision of the American spiders of the family Microstigmatidae (Araneae, Mygalomorphae).' American Museum Novitates 2707: 1-20.
https://wsc.nmbe.ch/family/56/Microstigmatidae
Photographic contributions: