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Mineralized skeletons of bryozoans first appear in rocks from the Early Ordovician period, [1] making it the last major phylum to appear in the fossil record. This has led researchers to suspect that bryozoans arose earlier but were initially unmineralized, and may have differed significantly from fossilized and modern forms.
[46] [48] During the Middle Triassic the scleractinian corals typical of modern oceans appeared. During the Triassic, corals were rare in North America. Nevertheless, some were present on the west coast, although these corals did not congregate into reefs. [49] Ichthyosaurs were one of the most important groups of marine reptiles during the ...
The large spindle-shaped genus Fusulina and its relatives were abundant in what is now Russia, China, Japan, North America; other important genera include Valvulina, Endothyra, Archaediscus, and Saccammina (the latter common in Britain and Belgium). Some Carboniferous genera are still extant. The first true priapulids appeared during this ...
This list of prehistoric bryozoans is an attempt to create a comprehensive listing of all genera that have ever been included in the bryozoa which are known from the ...
Sharks first appeared in the mid Devonian period, and are extremely rare to find anywhere. A variety of teeth from these sharks, some long and sharp, and others flat, can be seen in the collection of Alma College. They were found in Ohio in the late 19th century. Also found from these primitive sharks are spines from their fins, which were ...
This was South America's first eutherian carnivore. South American procyonids then diversified into forms now extinct (e.g. the "dog-coati" Cyonasua, which evolved into the bear-like Chapalmalania). However, all extant procyonid genera appear to have originated in North America. [70]
The Chazy Reef Formation is a mid-Ordovician limestone deposit in northeastern North America. It consists of some of the oldest reef systems built by a community of organisms [ 1 ] rather than the deposit of a limited range of similar organisms, such as Stromatolite mounds deposited by ancient cyanobacteria.
Lichenalia is an extinct genus of cystoporate bryozoan belonging to the family Rhinoporidae. It is known from the Upper Ordovician to the Middle Silurian periods, which spanned from approximately 460 to 430 million years ago.