Scansors

I haven't really done justice to the scansoriopterygids in the past. I did save them a spot in my dinosaur hands drawing, but as it turns out that one's wrong.

Scansors are just weird. They're rather small dinosaurs (pigeon sized) that (probably) hail from the Middle Jurassic and may have spent time in trees. They've come out as avialians in phylogenetic analyses, but they aren't very much like typical avialians. I wouldn't be surprised if they turned out to be a more basal lineage. It doesn't help that only three specimens are known, two of which are juveniles. The juvenile specimens are probably both Scansoriopteryx heilmanni (although one was described as "Epidendrosaurus ninchengensis"), while the third specimen was named Epidexipteryx hui. Scansoriopteryx heilmanni had a long tail with a fan of feathers at the tip, while Epidexipteryx hui had a short tail with four ribbon-shaped feathers attached (although it might be that its tail was longer than its fossil shows, as some tail vertebrae appear to be missing). However, it's been suggested that Epidexipteryx hui might actually be the adult of Scansoriopteryx heilmanni, which isn't as strange as it sounds, as other Mesozoic birds are known have shrunk their tails as they grew. The hands of Scansoriopteryx heilmanni (and possibly those of Epidexipteryx hui, but they aren't well preserved) were weird, too, with a long third finger. (In typical theropods, the second finger is the longest.) Strangely, the wing feathers of Scansoriopteryx heilmanni (Epidexipteryx hui doesn't preserve any wing feathers) appear to attach to the third finger, not the second as in typical aviremigians, which might lend support to the idea scansors aren't really aviremigians at all and evolved similarities with them convergently. Scales are known from underneath the base of the tail in Scansoriopteryx heilmanni, also unknown in other aviremigians. The first toe in scansors probably wasn't reversed (as first reported), but was placed low on the foot, similar to therizinosaurs. Scansor skulls tended to be short, with large front teeth, probably good for grabbing insects.