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Re: Gansus Bird-Dino Connection - Penn Press Release

On Wednesday, June 28, 2006, at 06:14 PM, Tim Williams wrote:

Michael Habib wrote:

Frigates can nest in trees, actually, despite not being able to 'perch' in the technical sense of the word.

By perching in the 'technical sense' do you mean one or more toes is capable of opposing two or more other toes in a prehensile grip?


Nevertheless, the hallux of two modern galliform groups (cracids and megapodids) inserts on the metatarsus at the same level of the other toes. To use the ornithological term, the hallux is 'incumbent' not 'elevated'. Megapodes live on the ground and use the long hallux for mound-building, but the cracids (guans, curassows, chachalacas) roost in trees and use the hallux to oppose the other toes. Cracids would be true perchers, wouldn't they?

Good point, the hallux of modern galliforms, being incumbent, probably forms a true prehensile grip (though not a particularly good one since the hallux is reduced in size). Cracids would certainly be true perchers. So I stand corrected on galliforms. Pelicaniforms and cavity-nesting anseriforms would remain as good examples of species that do not have a perching foot but utilize arboreal roosts or nests.

In any case, I did not intend to create so much confusion, my original point was merely that absence of a prehensile grip in a fossil bird (especially very basal ones) does not preclude arboreal habits.


--Mike H.