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A Petoskey stone is a rock and a fossil, often pebble-shaped, that is composed of a fossilized rugose coral, Hexagonaria percarinata. [1] Such stones were formed as a result of glaciation, in which sheets of ice plucked stones from the bedrock, grinding off their rough edges and depositing them in the northwestern (and some in the northeastern) portion of Michigan's lower peninsula.
It was a hermatypic coral, which require "warm, clear, shallow water" and live in symbiotic relationships with algae. [2] It is also likely that zooxanthellae (a kind of protozoa) lived on the coral. [3] It has been theorized that Isastrea could endure lower temperatures than most other hermatypic corals because it occurs farther north than ...
"Tetracorallia" from Ernst Haeckel's Kunstformen der Natur, 1904 Cross-section of Stereolasma rectum, a rugose coral from the Middle Devonian of Erie County, New York. The Rugosa, also called the Tetracorallia, rugose corals, or horn corals, are an extinct order of solitary and colonial corals that were abundant in Middle Ordovician to Late Permian seas.
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 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 ...
Around 300 species have been described. Among the most common tabulate corals in the fossil record are Aulopora, Favosites, Halysites, Heliolites, Pleurodictyum, Sarcinula and Syringopora. Tabulate corals with massive skeletons often contain endobiotic symbionts, such as cornulitids and Chaetosalpinx. [1] [2]
Favosites is an extinct genus of tabulate coral characterized by polygonal closely packed corallites (giving it the common name "honeycomb coral"). [1] The walls between corallites are pierced by pores known as mural pores which allowed transfer of nutrients between polyps.
Halysites (meaning chain coral) is an extinct genus of tabulate coral. [1] Colonies range from less than one to tens of centimeters in diameter, and they fed upon plankton. [2] These tabulate corals lived from the Ordovician to the Devonian (from 449.5 to 412.3 Ma).
Lithostrotion is a genus of rugose coral which is commonly found as a fossil within Carboniferous Limestone. Lithostrotion is a member of the family Lithostrotionidae. The genus Lithostrotion, a common and readily recognised group of fossils, became extinct by the end of the Palaeozoic era. [1]