Definition of proatlas in English:

proatlas

noun

Anatomy Zoology
  • A vertebral element located between the base of the skull and the atlas vertebra which fuses with the skull during embryonic development in most vertebrates, but persists as a distinct element in some, especially as a pair of small, V-shaped bones anterior to the neural arch of the atlas in certain reptiles (e.g. chameleons and tuataras).

Origin

Late 19th century; earliest use found in American Naturalist.