After Lamsdell, 2013
<==o Chelicerata Heymons, 1901 (chelicerates; kynsileukaiset)
|-- Pycnogonida Latreille, 1810 [Pantopoda; Arachnopoda Dana, 1853] (sea spiders; merilukit)
`--o Euchelicerata Weygoldt & Paulus, 1979
|-- †Offacolus kingi Orr et al., 2000
|?- †Sarotrocercus oblita Whittington, 1981
`--o Prosomapoda Lamsdell, 2013 [paraphyletic Merostomata Dana, 1852 (in partim); Synziphosurida]
|?- †Andarella Moore, McKenzie & Lieberman, 2007
|?- †Borchgrevinkium Novojilov, 1959
`==o †Weinberginidae Richter & Richter, 1929 [paraphyletic]
|?- †Dibasterium durgae Briggs, Siveter, Siveter, Sutton, Garwood & Legg, 2012
|-- †Weinbergina opitzi Richter & Richter, 1929
`--+--+-- †Venustulus waukeshaensis Moore, in Moore et al., 2005
| `-- †Camanchia grovensis Moore, Briggs, Braddy & Shultz, 2011
`--+-- †Legrandella lombardi Eldredge, 1974
`--+--o Xiphoxura Latreille, 1802 sensu Lamsdell, 2013 [Merostomata Dana, 1852] (horseshoe crabs; molukkiravut)
| |?-o †Maldybulakia Tesekov & Alekseev, 1998 [Lophodesmus Tesekov & Alekseev, 1992 (preoccupied?); Maldybulakia Edgecombe, 1998]
| | |-- †M. angusi Edgecombe, 1998
| | `-- †M. malcolmi Edgecombe, 1998
| |--o †Kasibelinurus Pickett, 1993 [Kasibelinuridae Pickett, 1993]
| | |-- †K. amicorum Pickett, 1993
| | `?- †K.? randalli (Beecher, 1902)
| `--+-- †Willwerathia laticeps (Størmer, 1936) [paraphyletic Weinberginidae]
| `-- Xiphosurida Latreille, 1802 (horseshoe crabs; molukkiravut)
`--o Planaterga Lamsdell, 2013
|--o †Bunodidae Packard, 1886
| |?-o †Bunaia Clarke, 1919
| | |-- †B. woodwardia
| | `-- †B. heintzi Størmer
| |-- †Bunodes lunula d'Eichwald, 1854 [Exapinurus Nieszkowski, 1859]
| `-- †Limuloides limuloides (Woodward, 1865) Størmer, 1952 [Hemiaspis Woodward, 1864] [Limuloididae Størmer, 1952]
|-- †Bembicosoma pomphicus Laurie, 1899 [paraphyletic Bunodidae]
|-- †Pasternakevia podolica Selden & Drygant, 1987 [paraphyletic Pseudoniscidae Packard, 1886]
|?- †Bunodella horrida Matthew, 1889 [paraphyletic Pseudoniscidae Packard, 1886]
|--+-- †Cyamocephalus loganensis Currie, 1927 [paraphyletic Pseudoniscidae Packard, 1886]
| `--o †Pseudoniscus Nieszkowski, 1859 [Neolimulus Woodward, 1868] [paraphyletic Pseudoniscidae Packard, 1886]
| |-- †P. aculeatus Nieszkowski, 1859
| `-- †P. roosevelti Clarke
`--o Dekatriata Lamsdell, 2013
|-- †Winneshiekia youngae Lamsdell, Briggs, Liu, Witzke & McKay, 2015
`--+-- †Houia yueya (Lamsdell, Xue & Selden, 2013) Selden, Lamsdell & Qi, 2015 [Kasibelinurus yueya Lamsdell, Xue & Selden, 2013]
`--+-- †Chasmataspidida Caster & Brooks, 1956 [Diploaspida Simonetta & Delle Cave, 1978]
`--o Sclerophorata Kamenz, Staude & Dunlop, 2011
|-- †Eurypterida Burmeister, 1843 [Gigantostraca Haeckel, 1866; Cyrtoctenida Størmer & Waterston, 1968] (meriskorpionit; seascorpions)
`-- Arachnida Lemarck, 1801 (hämähäkkieläimet; arachnides)
After Legg, 2014 (fig. 5a)
<==o Chelicerata
|-- Pycnogonida
`--+-- †Sanctacaris
`--+--+-- †Offacolus
| `-- †Sarotrocercus
`--o Euchelicerata
|--+-- †Dibasterium
| `-- Xiphosura
`--+-- †Chasmaspidida
`--+-- †Eurypterida
`-- Arachnida
Reference(s):
- Legg, D. A., 2014: Sanctacaris uncata: the oldest chelicerate (Arthropoda).
–Naturwissenschaften: Vol. 101, #12, pp. 1065-1073 [doi: 10.1007/s00114-014-1245-4]
|
After Parker, 1982, and Hou & Bergström, 1997
<==o Chelicerata
|-- Pycnogonida
`--o Euchelicerata
|--o Merostomata
| |-- Xiphosura
| `--+-- †Chasmataspida
| `-- †Eurypterida
`-- Arachnida
|
Reference(s):
- Briggs, D. E. G., Siveter, D. J., Siveter, D. J., Sutton, M. D., Garwood, R. J. & Legg, D., 2012: Silurian horseshoe crab illuminates the evolution of arthropod limbs.
–Proceedings of the National Academy of Sciences: Vol. 109, #39, pp. 15702-15705 [doi: 10.1073/pnas.1205875109]
- Haug, J. T., Maas, A., Haug, C. & Waloszek, D., 2011: Sarotrocercus oblitus - Small arthropod with great impact on the understanding of arthropod evolution?
–Bulletin of Geosciences: Vol. 86, #4, pp. 725-736
- Hou X. & Bergström, J., 1997: Arthropods of the Lower Cambrian Chengjiang fauna, southwest China.
–Fossils & Strata, Number 45, 22nd December 1997, pp. 1-116
- Kazlev, M. A., 2000: Order (and Class?) Chasmataspida.
–iNet: The Kheper site: http://www.kheper.auz.com/gaia/biosphere/arthropods/chasmataspida/index.html
- Lamsdell, J. C., 2013: Revised systematics of Palaeozoic ‘horseshoe crabs’ and the myth of monophyletic Xiphosura.
–Zoological Journal of the Linnean Society: Vol. 167, #1, pp. 1-27 [doi: 10.1111/j.1096-3642.2012.00874.x]
- Lamsdell, J. C., Briggs, D. E. G., Liu, H. P., Witzke, B. J. & McKay, R. M., 2015: A new Ordovician arthropod from the Winneshiek Lagerstätte of Iowa (USA) reveals the ground plan of eurypterids and chasmataspidids.
–The Science of Nature: Vol. 102, #9, pp. (1-8) [doi: 10.1007/s00114-015-1312-5]
- Parker, S. P. (ed.), 1982: Synopsis and classification of living organisms. Vols. 1 & 2
–McGrew-Hill Book Company
- Selden, P. A., Lamsdell, J. C. & Qi, L., 2015: An unusual euchelicerate linking horseshoe crabs and eurypterids, from the Lower Devonian (Lochkovian) of Yunnan, China.
–Zoologica Scripta: Vol. 44, #6, pp. (645-652) [doi: 10.1111/zsc.12124]
- Størmer, L., Petrunkevitch, A. & Hedgpeth, J. W., 1955: Arthropoda 2 - Chelicerata with sections on Pycnogonida and Palaeoisopus. xvii-181
in Moore, R. C. (ed.): Treatise on Invertebrate Paleontology - Part P
–Geological Society of America and University of Kansas Press, Lawrence, 1955
