Hexagonaria is a genus of colonial rugose coral. Fossils are found in rock formations dating to the Devonian period, about 350 million years ago. Specimens of Hexagonaria can be found in most of the rock formations of the Traverse Group in Michigan. Fossils of this genus form Petoskey stones, the state stone of Michigan.[1] They can be seen and found in most Midwestern U.S. states.
| Hexagonaria Temporal range: Devonian
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|---|---|
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| Hexagonaria percarinata | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Cnidaria |
| Class: | Hexacorallia |
| Subclass: | †Rugosa |
| Order: | †Stauriida |
| Family: | †Disphyllidae |
| Subfamily: | †Hexagonariinae |
| Genus: | †Hexagonaria Gürich, 1896 |
| Species | |
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Hexagonaria is a common constituent of the coral reefs exposed in Devonian Fossil Gorge below the Coralville Lake spillway[2] and in many exposures of the Coralville Formation in the vicinity of Coralville, Iowa.[3]
Species Identification
editBased on Erwin C. Stumm's Corals of the Traverse Group of Michigan Part 13, Hexagonaria, published in 1970.[1] Notably, other species of Hexagonaria occur in rocks outside the Michigan Basin; those other species are not covered by the chart below and may overlap with the species below in size and numbers of septa. Other features diagnose the differences between species; the metrics below merely represent handy features for diagnosis in the Michigan Basin, not comprehensive diagnoses.
| Species | Corallites (diameter) | Septa (count) |
|---|---|---|
| H. anna | 12–16 mm | 32-44 |
| H. cristata | 16–20 mm | 36-44 |
| H. fusiformis | 6–10 mm | 34-38 |
| H. percarinata | ~10 mm | 38-40 |
| H. alpenensis | 2–6 mm | 26-28 |
| H. subcarinata | 8–12 mm | 30-34 |
| H. attenuate | 8–14 mm | 30-38 |
| H. potterensis | 4–15 mm | 36-38 |
| H. profunda | 13–15 mm | 38-42 |
Image Gallery
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Hexagonaria mirabilis -
H. percarinata, "Petoskey stone"
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References
edit- ^ a b Stumm, Erwin C. (19 June 1970), Corals of the Transverse Group of Michigan Part 13, Hexagonaria (PDF), vol. 23, Ann Arbor: The University of Michigan Press, pp. 81–91
- ^ Jean Prior, Devonian Fossil Gorge Archived 2010-06-18 at the Wayback Machine, Iowa Geological Survey, 1998.
- ^ Brian J. Witzke and Bill J. Bunker, Sedimentation and stratigraphic architecture of a Middle Devonian (late Givetian) transgressive-regressive carbonate-evaporite cycle, Coralville Formation, Iowa area, Paleozoic Sequence Stratigraphy, Biostratrigraphy and Biogeology, Special Paper 321, Geological Society of America, 1997.
- "Hexagonaria". The Paleobiology Database. Archived from the original on 20 July 2011. Retrieved 27 February 2010.
Further reading
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Media related to Hexagonaria at Wikimedia Commons- Stumm, Erwin C. (1948). Lower Middle Devonian species of the tetracoral genus Hexagonaria of east-central North America. Contributions from the Museum of Paleontology. Vol. v. 7, no. 2. Ann Arbor: Univ. of Michigan Press. OCLC 11520377.
