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Perching, climbing, roosting was Re: 11th specimen of Archaeopteryx



My thoughts in random order. I hope I haven't forgotten half of them.

-- The 2nd toe of dromaeosaurids was able to be flexed very far. It may well have been used to hold branches against the metatarsus, all else being equal -- but all else wasn't equal. There's a reason why the huge claw is called "sickle claw": it's flattened from side to side, and its very narrow palmar edge, while blunt on the ungual bone, may have supported an outright cutting edge on the horny sheath in the living animal. Cutting off the branch on which you sit brings the Darwin Award to mind. Unfortunately, no keratinous claw of a dromaeosaurid is preserved in 3D as far as I know. -- Any species that climbs trees and stands around in them for evolutionary significant spans of time -- say, a few decades -- will show adaptations to this. -- Conversely, grasping feet -- including feet shaped by compromises between grasping and walking/running -- may not have grasped any plant matter, but prey. Today, the most extreme phalangeal ratios, claw sizes and claw curvatures are found in predatory birds. The hands of theropods are plesiomorphically in that range; this includes *Archaeopteryx*. Perhaps this also explains why carnosaurs had less extreme phalangeal ratios than extant cursorial birds. -- 300-lb rednecks are _better_ suited for climbing trees than *Archaeopteryx* was. Sure, their weight is a massive disadvantage, I presume they're wearing shoes, and they have laughably short toes; but they've got amazingly flexible hands, insanely mobile shoulders, forearms that can rotate through about 180° (and that's before we consider rotation of the entire arm at the shoulder joint), hips almost as mobile as a lizard's, rotatable lower legs, ankles that allow tilting of the feet, a long, flexible vertebral column, and a dorsoventrally flattened ribcage with the remarkably mobile shoulder blades on its dorsal side. Do not project primate -- or even "just" general mammalian or indeed general amniote! -- anatomy into dinosaurs. Do not take it for granted; not everyone has it. -- So far, I don't see a reason to assume any climbing or roosting in any dinosaur that wasn't able to fly into a tree. *Confuciusornis* may be an exception, but it had moderately grasping feet, huge curved claws on the 1st and 3rd fingers, an enormous deltopectoral crest on each robust humerus, and IIRC shorter legs than Archie, especially shorter lower legs; it was clearly better at trunk-climbing than Archie, even if not much. -- Why climb into a tree for safety rather than hide under a shrub? There are mammals and squamates in both places. Complete safety is for oceanic islands, if that. -- Yes, the ability to perch is plesiomorphic for Neornithes. That doesn't mean it evolved much earlier. Crown-group turtles are amphibious plesiomorphically, and the extant terrestrial representatives are secondarily terrestrial, but among Testudinata as a whole, the marine *Odontochelys* is an outlier; the rest of the stem group was unambiguously terrestrial. -- As someone mentioned, goats are fairly highly specialized rock climbers. Seeing them in a tree isn't any more surprising than seeing 300-lb rednecks in a tree. And apparently the tree kangaroos are the sister-group of the rock wallabies (*Petrogale*). -- *Zhongornis*? Underrated? Isn't it rather an overrated juvenile *Confuciusornis*?