The Leos is a species whose egg is featured on Eggdoku. Leos

Original concept art from 2012 pictured below:

Felisfire concept art leos by delve-d58hysp

Created by delve aka KnifeSmile(#1414)

The Leos was said to be an undead lion-wyvern species, cursed by the feli gods, however, the concept was altered and updated in 2016 by the site's staff and a new concept was drawn by Luna(#5626), which is now the one currently slated to be released.

The Leos will likely be released in 2017.