Lemdadella
| Lemdadella Temporal range: [1]
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| Genus: | Lemdadella Sdzuy, 1978
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Lemdadella is an extinct genus of redlichiid trilobites that lived during the late Atdabanian stage,[1] which lasted from 530 to 524 million years ago during the early part of the Cambrian Period.
Distribution
- Lemdadella sp. occurs in the Lower Cambrian of Morocco (Botomian, Ounein A bioherm, Lemdad 1 section, High Atlas )[2]
- Lemdadella linaresae was collected in the Lower Cambrian of Spain (Atdabanian, Pedroche Formation, Member 1, Puente de Hierro Section)[3]
- Lemdadella sp. was found in the Lower Cambrian of Antarctica (Toyonian, Shackleton Limestone; BC-BD collections)[4]
- Lemdadella antarcticae occurs in the Lower Cambrian of Antarctica (Atdabanian, Shackleton Limestone; BC-BD collections)[5]
Description
Glabella gently tapered forward. At the midline, a ridge between the glabella and the border of the cephalon (a so-called plectrum) may be present. Crescent-shaped eye-ridges. Thorax not divided in prothorax and opisthothorax, no macropleural segment.[6]
Biostratigraphy
Lemdadella is currently the oldest trilobite genus known, dating back to about Template:Geologic Ages Inline million years ago. The International Commission on Stratigraphy has proposed that the first appearance datum of trilobites should be used as the lower boundary of Cambrian Series 2 and Cambrian Stage 3.[7] If this proposal will be defined as a GSSP, it will most likely use the first appearance of Lemdadella, a species of Lemdadella, or a trilobite zone that includes Lemdadella. The age and global distribution of Lemdadella are therefore of key importance for the Stratigraphy of the Cambrian.[8]
The following trilobite zones contain Lemdadella (Brackets contain geographic distribution):[8]
- Fallotaspis zone (Spain, Laurentia)
- Eoredlichia-Yunnanocephalus zone (Antarctica)
References
- ^ a b Sepkoski, Jack (2002). "A compendium of fossil marine animal genera (Trilobita entry)". Bulletins of American Paleontology. 364: 560. Retrieved 2008-01-12.
- ^ Geyer, G.; Landing, E.; Heldmaier, W. (1995). "Faunas and depositional environments of the Cambrian of the Moroccan Atlas regions". Beringeria. Special Issue 2: 47–119.
- ^ Liñán, E.; Dies, M.E.; Vintaned, J.A.G.; Gozalo, R.; Mayoral, E.; Muñiz, F (2005). "Lower Ovetian (Lower Cambrian) trilobites and biostratigraphy of the Pedroche Formation (Sierra de Córdoba, southern Spain)". Géobios. 38: 365–381. doi:10.1016/j.geobios.2003.11.007.
- ^ Palmer, A.R.; Rowell, A.J. (1995). "Early Cambrian trilobites from the Shackleton Limestone of the Central Mountains". Journal of Paleontology Memoir. 69 (6): 1–28.
- ^ Palmer, A.R.; Rowell, A.J. (1995). "Early Cambrian trilobites from the Shackleton Limestone of the Central Mountains". Journal of Paleontology Memoir. 69 (6): 1–28.
- ^ Paterson, R.J.; Jago, J.B. (2006). "New trilobites from the Lower Cambrian Emu Bay Shale Lagerstätte at Big Gully, Kangaroo Island, South Australia". Memoirs of the Association of Australasian Palaeontologists. 32: 43–57. ISSN 0810-8889.
- ^ "GSSP Table - Paleozoic Era". Retrieved 18 November 2012.
- ^ a b Yuan, J.L.; Zhu, X.J.; Lin, J.P.; Zhu, M.Y. (22 September 2011). "Tentative correlation of Cambrian Series 2 between South China and other continents" (PDF). Bulletin of Geosciences: 397–404. doi:10.3140/bull.geosci.1274. Retrieved 23 November 2012.
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