Mickwitzia
| Mickwitzia Temporal range: Terreneuvian–mid Cambrian | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Clade: | Brachiozoa |
| Stem-group: | Brachiopoda |
| Family: | †Mickwitziidae Goryanskii, 1969 |
| Genus: | †Mickwitzia Schmidt, 1888 |
| Species | |
| |
Mickwitziids are a Cambrian group of shelly fossils with originally phosphatic valves, belonging to the Brachiopod stem group, and exemplified by the genus Mickwitzia – the other genera are Heliomedusa (a possible junior synonym of Mickwitzia?) and Setatella.[1]
Shell microstructure
Punctae or tubes penetrate through multiple shell wall layers, and individual punctae often develop a single, axial phosphatic tube. The shell comprises multiple phosphatic laminae; the region closest to the edge of the shell was presumably more organic-walled than phosphatized as it tends to be more flimsily preservevd.[2]
Members of the genus appear to share characteristic shell microstructure in common with Tommotiids such as Micrina,[3] and like this taxon, mickwitziids may not have been able to enclose their entire body within a bivalved shell.[4]
The shells are punctuated with inward-directed hollow cones, conceivably associated with setae – though intact setae are exceptionally preserved along the margin of mickwitziid shells yet not found emanating from the cones, which have no evidence of ever incorporating setae.[2]
Affinity
Mickwitziids are stem-group brachiopods, with links to the tommotiid grade. Mickwitzia itself is conceivably synonymous with Heliomedusa.[2]
Distribution
The oldest mickwitziid dates to the Terreneuvian.[5]
References
- ↑ 1 Butler, A. D., Streng, M., Holmer, L. E. & Babcock, L. E. 2015 Exceptionally preserved Mickwitzia from the Indian Springs Lagerstätte (Cambrian Stage 3), Nevada. J. Paleontol. 89, 933–955. (doi:10.1017/jpa.2016.8)
- 1 2 3 Butler, Aodhán D.; Streng, Michael; Holmer, Lars E.; Babcock, Loren E. (2016). "Exceptionally preserved Mickwitzia from the Indian Springs Lagerstätte (Cambrian Stage 3), Nevada". Journal of Paleontology. 89 (6): 933–955. doi:10.1017/jpa.2016.8.
- ↑ McMenamin, M. A. S. (1992). "Two new species of the Cambrian genus Mickwitzia". Journal of Paleontology. 66 (2): 173–182. doi:10.1017/S0022336000033680 (inactive 2016-07-09). JSTOR 1305903.
- ↑ Holmer, L. E.; Skovsted, C. B.; Williams, A. (2002). "A stem group brachiopod from the Lower Cambrian: Support for a Micrina (halkieriid) ancestry". Palaeontology. 45 (5): 875–882. doi:10.1111/1475-4983.00265.
- ↑ Devaere, Léa; Holmer, Lars; Clausen, Sébastien; Vachard, Daniel (2014). "Oldest mickwitziid brachiopod from the Terreneuvian of southern France". Acta Palaeontologica Polonica. doi:10.4202/app.00021.2013.