From the Super Mario Wiki
The title of this article is conjectural; an official name for the article's subject has not been found, so it has been given a fitting title by editors. If an official name appears, it is requested that the article be moved to the correct name.
Baby Dragoneels are shorter sub-species of Dragoneels that also first appeared in New Super Mario Bros. U. Instead of being red, they are purple colored.
New Super Mario Bros. U
In New Super Mario Bros. U, only two Baby Dragoneels appear in a small section with Coins and a Star Coin of the Sparkling Waters level, Dragoneel's Undersea Grotto. They have the same strategies of the Dragoneel, they follow Mario, while the hero must avoid them. However, they make tighter turns, and are significantly slower. Throwing fireballs at its head will make it move slower and slower. They are one of the few enemies that don't reappear in New Super Luigi U.