A field guide to mesozoic birds and other winged dinosaurs

Microraptorians
Microraptorians were the smallest and among the most primitive
ornithodesmids, most retaining many features in common with archaeopterygids
and early troodontids. The earliest members of this group
were large compared to other primitive birds, though later members independently
re-acquired small sizes comparable to archaeopterygids. None
were as large as the moderately sized members of the other ornithodesmid
groups.
Microraptorians appear to have been more predatory than most
other early birds, beginning a trend that would reach its apogee in the large
eudromaeosaurians. Most had long, narrow snouts with recurved and partially
serrated teeth. The claw borne on digit II was larger than in archaeopterygids
and many troodontids of the same size, though it was still relatively
broad compared to eudromaeosaurians and may have been primarily
a climbing tool. There is evidence that even the smallest species, such as
Microraptor zhaoianus, occasionally took prey that approached or exceeded
their own body size.
Suggestions that some microraptorians were venomous, and that
they had long, protruding, fang-like teeth, are incorrect, and were based on
misinterpretation of teeth that had come out of their sockets during fossilization.
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