Ypresicolius sandcoleiformis Mayr & Kitchener, 2024 (new genus and species)
(Specimens of Ypresicolius sandcoleiformis [scale bars = 5mm], from Mayr and Kitchener, 2024)
Meaning of name: Ypresicolius = Ypresian Colius [genus of mousebirds including the extant speckled mousebird]; sandcoleiformis = sandcoleid-shaped [in Latin]
Age: Eocene (Ypresian), 54.6‒55 million years ago
Where found: London Clay Formation, Essex, U.K.
How much is known: Two partial skeletons, together including various limb bones and some vertebrae.
Notes: Ypresicolius was a close relative of extant mousebirds, a group of small, tree-dwelling birds. Mousebirds are nimble climbers with long tail feathers, and feed mostly on fruits and leaves. Today, they are found only in Africa, but their close fossil relatives are known from the Paleogene of Europe and North America.
Like another group of Paleogene proto-mousebirds, the sandcoleids, Ypresicolius had raptor-like talons that it may have used for handling food. (However, this does not mean that these proto-mousebirds primarily ate meat, as sandcoleids lacked hooked beaks and preserved gut contents suggest that they regularly ate fruit.) Despite these and other similarities with sandcoleids, details of the hindlimb and breastbone anatomy of Ypresicolius may indicate that it was slightly more closely related to modern mousebirds.
Reference: Mayr, G. and A.C. Kitchener. 2024. A new mousebird (Aves, Coliiformes) from the early Eocene London Clay of Walton-on-the-Naze (Essex, United Kingdom) constitutes a morphological link between sandcoleids and coliids. Geodiversitas 46: 979–993. doi: 10.5252/geodiversitas2024v46a20
