Carpometacarpus

The proximal end of the carpometacarpus is a large, trochleated, convex lump that is very obviously homologous with the semi-lunate carpal bone of non-avian maniraptoran theropods. ❋ Unknown (2010)

Based predominantly on the morphology of the carpometacarpus, some ornithologists have proposed that cariamaens are closely related to the Hoatzin* Opisthocomus hoazin**, that bizarre folivorous, arboreal bird that (uniquely among birds) practices foregut fermentation. ❋ Darren Naish (2006)

(Anhimidae) are, in terms of hand anatomy, among the most incredible of birds because they possess two large spikes on the carpometacarpus. ❋ Unknown (2010)

While birds do still possess the bones of three individual fingers, the metacarpal and distal carpal bones have united to form a single structure called the carpometacarpus. ❋ Unknown (2010)

In The Palaeontological Association Newsletter article mentioned above, Al McGowan (2006) also mentioned Stewart’s interest in this subject and, even better, discussed and figured an eagle owl carpometacarpus from post-glacial deposits near Cheddar, Somerset. ❋ Darren Naish (2006)

A projecting structure termed the extensor process (or extensor attachment) is present between the carpal trochlea and the alular digit; it belongs to metacarpal I (also called the alular metacarpal), but this is hard to appreciate in modern birds because metacarpal I is fused imperceptibly into the carpometacarpus as mentioned above [in the adjacent diagram, from ❋ Unknown (2010)