Actinistia
Quick Summary
Actinistia is an order of lobe-finned bony fishes that appeared in the Devonian Period, approximately 400 million years ago. This group is now represented by only two living species of coelacanths, genus Latimeria.12
Key characteristics of Actinistia include:
* A skull divided into two units connected by a strong joint.1
* Incompletely ossified skull bases and vertebral columns, with the notochord often persisting.1
* Fleshy, lobed fins supported by bone or cartilage, which foreshadowed the limbs of land vertebrates.1
* Modern coelacanths are large predators, averaging 5 feet in length and weighing around 100 pounds. They are slow-growing and long-lived, with some individuals estimated to be over 100 years old.2
Coelacanths were thought to be extinct until a living specimen was discovered in 1938. Both living species, the African coelacanth (Latimeria chalumnae) and the Sulawesi coelacanth (L. menadoensis), are considered threatened.2
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