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Re: Heterodontosaurid with protofeathers
Jeff Hecht wrote:
> I talked with Alan Brush who says the "protofeathers" were
> hollow unbranched structures, just as he and Rick Prum had
> predicted the ancestral form would be. I'm no expert, but
> it's looking plausible that some kind of filamentary fuzz
> might have been primitive within archosaurs after the
> crocodiles split off. Or perhaps before; it could be that
> the fuzz was easy to lose.
Jeff, I agree. At least to a large degree...
"One possibility... is that a fuzzy body covering is primitive for Ornithodira,
and was retained by certain pterosaurs (like _Sordes_ etc) and dinosaurs
(especially small theropods), but lost (or scaled back) independently in many
lineages. Under this hypothesis, sauropodomorphs would be secondarily 'naked'.
Most (and maybe all) ornithischians might be naked too - either due to large
body size, or to a burrowing ecology in the smaller and/or more basal
ornithischians. The tail 'quills' of _Psittacosaurus_ could even be highly
modified versions of these filamentous structures. This hypothesis would mean
that a fuzzy integument would go back to lagosuchian-grade archosaurs. Highly
speculative, I know, and as I write this I find myself less and less convinced
that it's even plausible."
As I re-read this, I find this idea slightly more plausible. And with the
caveat that we now have basal ornithischians (a heterodontosaur) with
Although this topology is not supported in the _Tianyulong_ paper, a
Heterodontosauriformes clade (uniting heterodontosaurids and marginocephalians)
could make the integumentary structures of _Tianyulong_ and _Psittacosaurus_
synapomorphic for heterodontosauriforms and independent of theropods.