Euthycarcinoidea
| Euthycarcinoidea Temporal range: Cambrian–Middle Triassic | |
|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| (unranked): | Euthycarcinoidea |
Euthycarcinoidea was a group of enigmatic, possibly amphibious arthropods that ranged from Cambrian to Triassic times.
Morphology
The euthycarcinoid body was divided into cephalon (head), preabdomen, and postabdomen. The cephalon consisted of two segments and included mandibles, antennae and presumed eyes. The preabdomen consisted of 5-14 tergites, each having up to 3 somites. Each somite had in turn a pair of uniramous, segmented legs. The postabdomen was limbless and consisted of up to 6 segments and a terminal tailspine.[1]
Affinities
Due to its particular combination of characteristics, the position of the Euthycarcinoidea within the Arthropoda has been ambiguous; however, its general features and the discovery of fossils from this group in Cambrian rocks suggest that it may have given rise to the mandibulates - i.e., the group that includes the myriapods (centipedes, millipedes and the like), crustaceans, and hexapods (insects).[2]
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Environment and Life Habits
Euthycarcinoid fossils have been found in marine, brackish and freshwater deposits.[3] Fossil impressions of euthycarcinoid postabdomens in association with Protichnites trackways in Cambrian intertidal / supratidal deposits also suggest that euthycarcinoids may have been the first arthropods to walk on land.[4] [5] It has been suggested that the biofilms and microbial mats that covered much of the vast tidal flats during the Cambrian Period in North America may have provided the nourishment that lured these arthropods onto the land.[6] Fossil evidence also suggests the possibility that some euthycarcinoids came onto the land to lay and fertilize their eggs via amplexus, as do the modern limulids (horseshoe crabs)[7]
References
- ↑ Ortega-Hernandez et al., 2010, page 195.
- ↑ Ortega-Hernandez et al., 2010, page 196.
- ↑ Ortega-Hernandez et al., 2010, page 196 & 197.
- ↑ Collette & Hagadorn, 2010.
- ↑ Collette et al., 2012.
- ↑ MacNaughton et al., 2002. page 394.
- ↑ Collette et al., 2012, pages 452 & 453.
Further reading
- Anderson, L. I.; Trewin, N. H. (1991). "An early Devonian arthropod fauna from the Windyfield cherts, Aberdeenshire, Scotland". Palaeontology 46 (3): 467–509. doi:10.1111/1475-4983.00308.
- Collette, J. H., Gass, K. C. & Hagadorn, J. W. (2012). "Protichnites eremita unshelled? Experimental model-based neoichnology and new evidence for a euthycarcinoid affinity for this ichnospecies". Journal of Paleontology 86 (3): 442–454. doi:10.1666/11-056.1.
- Collette, J. H. & Hagadorn, J. W. (2010). "Three-dimensionally preserved arthropods from Cambrian Lagerstatten of Quebec and Wisconsin". Journal of Paleontology 84 (4): 646–667. doi:10.1666/09-075.1.
- MacNaughton, R. B., Cole, J. M., Dalrymple, R. W., Braddy, S. J., Briggs, D. E. G., & Lukie, T. D. (2002). "First steps on land: Arthropod trackways in Cambrian-Ordovician eolian sandstone, southeastern Ontario, Canada". Geology 30 (5): 391–394. Bibcode:2002Geo....30..391M. doi:10.1130/0091-7613(2002)030<0391:FSOLAT>2.0.CO;2.
- McNamara, K. J. & Trewin, N. H. (1993). "A euthycarcinoid arthropod fauna from the Silurian of Western Australia". Palaeontology 36: 319–335.
- Ortega-Hernandez, J., Tremewan, J., & Braddy, S. J. (2010). "Euthycarcinoids". Geology Today 26 (5): 195–198. doi:10.1111/j.1365-2451.2010.00770.x.
- Vaccari, N. E., Edgecome, G. D. & Escudero, C.; Edgecombe; Escudero (2004). "Cambrian origins and affinities of an enigmatic fossil group of arthropods". Nature 430 (6999): 554–557. Bibcode:2004Natur.430..554V. doi:10.1038/nature02705. PMID 15282604.