Darting Hatchling

Source
This item is found within the Dart's Nest an infrequently spawned object in Dustwallow Marsh. The spawn location appears to be close to where Dart, a rare mob raptor appears. However reports are that they are not on the same timer.

It can also appear on the Black Market Auction House.

Pet Journal
''Rarely leaves nest until maturity. Enjoys conducting pranks on the nearby Razormaw nest.''

Trivia
Occasionally it will "dart" off into the distance at a high speed and run around in a circle before returning.