A new petrel (Aves: Procellariidae) from the early Miocene of Patagonia (Argentina)

A right carpometacarpus (MLP 10-XII-11-1) from the early Miocene Gaiman Formation was collected in the fossiliferous locality Bryn Gwyn (Chubut Province, Argentina). After extensive comparisons with extinct and extant species, and geometric morphometric analyses, we concluded that it belongs to Procellariidae. It is supported by the presence of sulcus tendineus restricted to the distal half, a small crest belonging to the m. ulnometacarpalis dorsalis scar, notch and tubercle on the ventral rim of trochlea carpalis, a wide fovea carpalis caudalis not proximally delimited, a rounded, shallow, and proximo-cranial fossa supratrochlearis, and pneumatic foramina within the small fovea carpalis caudalis. The geometric morphometric analyses show clear similarities with Procellariidae, and locate MLP-10-XII-11-1 close to Procellaria aequinoctialis, Daption capense and Pterodroma incerta in the dorsal configuration, and to P. incerta and Macronectes giganteus in the ventral one. Also, the dorsal configuration is more conservative within families than the ventral one. Although this carpometacarpus does not present any exclusive character, the combination of characters found in the new fossil is unique, suggesting that MLP 10-XII-11-1 might represent a new genus and species. However, the proposal of a new species must wait until more complete specimens are found.