Hexagonaria

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 states.

Not to be confused with Hexagonia.

Hexagonaria
Temporal range: Devonian 416–359.2 Ma
Hexagonaria percarinata
Scientific classification
Kingdom: Animalia
Phylum: Cnidaria
Class: Anthozoa
Family: †Disphyllidae
Subfamily: †Hexagonariinae
Genus: †Hexagonaria
Gürich, 1896
Species
  • H. anna
  • H. cristata
  • H. fusiformis
  • H. percarinata
  • H. alpenensis
  • H. subcarinata
  • H. attenuate
  • H. potterensis
  • H. profunda
  • H. mirabilis

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

Based on Erwin C. Strumm's Corals of the Traverse Group of Michigan Part 13, Hexagonaria, published in 1970.[1]

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

References
  1. Stumm, Erwin C. (19 June 1970), Corals of the Transverse Group of Michigan Part 13, Hexagonaria (PDF), 23, Ann Arbor: The University of Michigan Press, pp. 81–91
  2. Jean Prior, Devonian Fossil Gorge Archived 2010-06-18 at the Wayback Machine, Iowa Geological Survey, 1998.
  3. 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.

Further reading
  • Stumm, Erwin C. (1948). Lower Middle Devonian species of the tetracoral genus Hexagonaria of east-central North America. Contributions from the Museum of Paleontology. v. 7, no. 2. Ann Arbor: Univ. of Michigan Press. OCLC 11520377.
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