Dave is the nickname for a particularly interesting and complete specimen of dromaeosaurid. It is also called NGMC 91, a specimen designation. It has been referred to the taxon Sinornithosaurus , but the authors considered that it was potentially viable it was a new species and so did not refer it to the only known species (at the time), Sinornithosaurus millennii . (Currently, there are two species, now supplemented by Sinornithosaurus haoiana .)
There’s a lot to be said about Dave. Here’s a few oddbits.
1. Dave, unlike many fossils from the Liaoning lagerstätten, is not just covered in “dinofuzz,” but is completely covered in it. The only region of the body that seems to not bear any filamentous integument is the foot (which preserves scales) and the tip of the nose (which doesn’t seem to preserve anything in detail).
2. Dave is covered in a variety of different types of integument, from thin filaments (stage 1 feathers of ), bound and bunched clusters, and a pennaceous “true” feather.
3. These are not distributed around the body in converntional forms: The pennaceous feathers are not barbulated, preserving only the barbs and rachis. Thus, they are not truly “vaned.” This type of feather occurs in birds today, and is considered both degenerate from a true vaned plume, and as an antecedant to it . These features are known in Dave only at the tip of the tail and in the base of the hindlimb. They are not present in the forelimb, or elsewhere on the hindlimb. In direct contrast to Microraptor gui  (a closely related taxon), the arm and leg did not have “wings.” Sinornithosaurus millennii also doesn’t seem to have true “wings,” as filamentous integument are found on the arms of the holotype .
4. Dave is not an adult, it seems: Portions of its body appear juvenile, including the proportion of the head to the body, and of the limbs to the body, while many features suggest it is a specimen of Sinornithosaurus millennii. It’s not unlikely that the specimen is its own, unique taxon, related to Sinornithosaurus millennii, but it has been considered less likely in the extent that it is preferable to not name juveniles as the basis of taxonomy when there are also likely adults present.
5. Dave is strange. Several bones of the body are actually longer than those of Sinornithosaurus millennii, despite variation in the proportions and indications Dave is a juvenile of the other taxon. This is one good reason why Dave is not always considered a specimen of Sinornithosaurus millennii, even if it is still a juvenile. Ontogeny is not well understood in dromaeosaurids due to a lack of juveniles but also because microraptorian dromaeosaurids are even more different from conventional dromaeosaurids due to their skeletal features, proportions, etc. .
So what does that mean? Dave is important, and not fully described, which makes much of this preliminary. But there are certainly several things we can glean from what is presented to us. First, let’s compare the two taxa we’re talking about:
Dave is pretty small, although larger than Microraptor zhaoianus, and has some odd proportions: a very short tail, a large triangular head, and relatively shorter arms. These seem to be ontogenetically younger features. But scaling does not compare among other animals, for some of Dave’s limbs are very close to the “adult” size, despite other portions being vastly smaller. It is likely a subadult, but is it necessarily a subadult of Sinornithosaurus millennii? That’s left Dave in the grey area phylogenentically.
Dave is also particular for preserving a variety of integument. This includes simple filaments, complex basally-branching filament bundles, and long raches with barbs, effectively plumulaceous feathers. The last set are only know from the rear of the leg, and are limited to the thigh. You can see this distribution below:
IVPP V12811, the holotype of Sinornithosaurus millennii, preserves only “stage 1 feathers” (see ), around the legs, chest and arms, and tail, where they are present in NGMC 91. But the latter specimen elaborates this, while showing that the tip of the snout and the feet were likely unfeathered. Some have argued, however, that despite this, the integument can be adapted or expanded beyond the preserved or likely limits of what we’ve found, but I’ll get to that in a later post.
Dave tells us that there’s more about integument evolving in theropod dinosaurs than we know, and that modern avian feathers, derived from a core model, are all exapted from a type III-IV feathers , but many of their precursors lacked any such thing as a modern avian feather. Dave’s feathers lack barbules, which link barbs together and are inherent to the form of a pennaceous feather (you cannot have a “vane” without barbules, as the barbules link the barbs into said structure). Yet despite this, Dave also has some feathers around its pollex (“thumb”), which may be termed an “alula” with only the faintest twinge of regret. That’s because the alula in birds certainly arises from the first digit (mdI), but in this case it likely have to do with the fact that, with the apparent exception of the tip of the snout and the actual exception of the tarsus and pes, Dave is entirely coated in feathers, including the entire manus [see above].
 Ji Q., Norell, M. A., Gao, K.-q., Ji S.-a. & Ren D. 2001. The distribution of integumentary structures in a feathered dinosaur. Nature 410:1084-1087.
 Xu X., Wang X.-l. & Wu X.-c. 1999. A dromaeosaurid dinosaur with a filamentous integument from the Yixian Formation of China. Nature 401:262-266.
 Liu J., Ji S.-a., Tang, F.-c. & Gao, K.-q. 2004. A new species of dromaeosaurids from the Yixian Formation of western Liaoning. Geological Bulletin of China 23(8):778-783.
 Prum, R. O. 1999. Development and evolutionary origin of feathers. Journal of Experimental Zoology 285:291-306.
 Xu X., Zhou Z.-m, Wang X.-l., Kuang X., Zhang F.-c. & Du X. 2003. Four-winged dinosaurs from China. Nature 421:335-340.