A geological region in the Karoo Basin of South Africa, comprising a group of terrestial formations, largely river-deposited shales and sandstones, dating from the Middle Permian through Early Triassic periods. The Cambrian is preceded by the Edicarian stage at the end of the Pre-Cambrian, and followed by the Ordovician period.
Bone fish dating review
The Middle Cambrian comprises the Cambrian B and C epochs; in North America these are named the Montezuman, Dyerian, Delmaran and Marjuman Stages, dating from 520-500 mya.
The Late Cambrian is identified as the Cambrian D epoch; in North America these are named the Steptoean and Sunwaptan Stages, dating from 500-490 mya.
Canini includes all wolves and domesticated dogs, including the Australian dingo,) of dogs were first used in Linnean classification.
Both archaeological finds and recent genetic studies indicate that dogs were domesticated from grey wolves (Canis lupus) by about 15,000 years ago.
These show that Acanthostega had well-developed limbs, with an unusual array of 8 digits on its hands and feet.
Acanthostega was mainly adapted to life in the water. The species name gunnari is for Gunnar Save-Soderburgh, who first discovered the fossil evidence of this tetrapod in the 1930s.In 1987 Jennifer Clack of Cambridge University found and published descriptions of more complete specimens.Many have a type of tooth with interlayered enamel and dentine, called labyrithodont (“”).This trait used to be thought to signify early amphibians ancestral to reptiles, but it does not occur consistently in the reptile-like amphibians called Reptilomorphs, which eventually developed into reptiles.It is recognized as the direct ancestor of all breeds of domestic dogs, the earliest of whom were simply tamed gray wolves.