Isoxys
| Isoxys | ||||||
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Isoxys sp. , 24mm |
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| Temporal occurrence | ||||||
| Lower to Middle Cambrian | ||||||
| 521 to 504.5 million years | ||||||
| Locations | ||||||
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| Systematics | ||||||
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| Scientific name | ||||||
| Isoxys | ||||||
| Walcott , 1890 | ||||||
Isoxys is a genus with an uncertain position within the arthropods (Arthropoda).
features
Isoxys had a non-mineralized head shield with flexible lateral pleural folds which almost completely covered the body, large spherical eyes, and a pair of extremities with thick spiky outgrowths on their anterior margins. The following 13 limbs had a two-branch shape with paddle-like limbs. This was followed by a telson with side flaps that protruded over the rear edge of the head shield.
The intestine has also been partially preserved: it was pipe-like and ran from the mouth to the telson and was flanked by bulbous structures arranged in pairs, which are believed to be digestive glands.
Way of life
The genus occurred exclusively in tropical and subtropical areas. Because of the morphology of the Telsons and the paddle-like limbs on the thorax , Isoxys is thought to be a swimmer. The large eyes enabled an almost 360 ° view, which was helpful for hunting and also to protect against predators. The pleural folds almost completely covering the body also served as protection.
Locations
The genus Isoxys has been found in Cambrian fossil deposits worldwide : in North America ( Burgess Shale , Sirius Passet , Langston Formation, Chilhowee ), South Australia ( Emu Bay Shale ), China ( Kaili Formation , Chengjiang ), Siberia , southern France and Spain . Due to the numerous occurrences, one concludes that Isoxys was widely distributed during the Cambrian.
Systematics
The systematic classification within the arthropods has not yet been clarified. Some authors place Isoxys with the arachnomorpha , others, however, because of the extremities on the head, directly with the jawbearers (Chelicerata). Some authors include the genus in the class Thylacocephala , but their relationship is also unclear
The following types are currently described:
- Isoxys acutangulus Walcott, 1908
- Isoxys auritus Jiang, 1982
- Isoxys bispinatus Cui, 1991
- Isoxys carbonelli Richter & Richter, 1927
- Isoxys chilhoweanus Walcott, 1890 ( type )
- Isoxys communis Glaessner, 1979
- Isoxys curvirostratus Vannier & Chen, 2000
- Isoxys glaessneri García-Bellido, Paterson, Edgecombe, Jago, Gehling & Lee, 2009
- Isoxys longissimus Simonetta & Delle Cave, 1975
- Isoxys paradoxus Hou, 1987
- Isoxys volucris Williams, Siveter & Peel, 1996
- Isoxys wudingensis Luo and Hu, 2006
- Isoxys zhurensis Ivantsov, 1990
swell
literature
- Diego C. García-Bellido, Jean Vannier and Desmond Collins: Soft-part preservation in two species of the arthropod Isoxys from the middle Cambrian Burgess Shale of British Columbia, Canada . Acta Palaeontologica Polonica 54 (4) 2009: 699-712. doi : 10.4202 / app.2009.0024
Individual evidence
- ↑ M. Williams, DJ Siveter, JS Peel: Isoxys (Arthropoda) from the early Cambrian Sirius Passet deposit, North Greenland . Journal of Paleontology 70, 1996: 947-954.
- ^ TJ Cotton, SJ Braddy: The phylogeny of arachnomorph arthropods and the origin of the Chelicerata . Transactions of the Royal Society of Edinburgh: Earth Sciences 94, 2004: 169-193.
- ^ MA Wills, DEG Briggs, RA Fortey, M. Wilkinson, PHA Sneath: An arthropod phylogeny based on fossil and recent taxa . In: GD Edgecombe (ed.): Arthropod Fossils and Phylogeny , 1998, 33-105.
- ↑ J.-Y. Chen, D. Waloszek, A. Maas: A new “great appendage” arthropod from the Lower Cambrian of China and homology of chelicerate chelicerae and raptorial antero − ventral appendages . Lethaia 37, 2004: 3-20.
- ↑ J. Vannier, J.-Y. Chen, D.-Y. Huang, S. Charbonnier, X.-Q. Wang: The Early Cambrian origin of thylacocephalan arthropods . Acta Palaeontologica Polonica 51 (2), 2006: 201-214. PDF