Feathers edge closer to the origins of dinosaurs by Aziz1412


									                               The beautiful specimen of Sciurumimus.
                         Aside from the last few bones of the tail it is complete

It has been clear to palaeontologists for decades now that living birds are the direct descendants of
dinosaurs. Much evidence had been accumulated from skeletons, eggs and other fossils to support this
conclusion, but the icing on the cake came in the late 1990s with the first discoveries of feathered
dinosaurs. There were animals that were from lineages that originated before Archaeopteryx and its kin
took to the skies – feathers had, rather unsurprisingly, evolved well before flight. Now dozens of
specimens are known from several different fossil beds representing more than 20 species of dinosaurs
that were not birds, but that did definitively have feathers.
                              he skull of Sciurumimus seen under UV light

However, feathers require unusually good preservational conditions to become fossils and remain
relatively rare. This means it's near certain that many of the dinosaurs that we know only from bones
did have feathers when alive – given the presence of feathers in the tyrannosaurs Yutyrannus and Dilong
for example, it's looking increasingly likely that the legendary Tyrannosaurus rex had feathers. For
palaeontologists the real question though is quite when feathers first appeared. To date, discoveries
have been limited to a major group of dinosaurs called the coelurosaurs. However, a newly described
dinosaur called Sciurumimus potentially pushes the origin of feathers back towards the origin of
dinosaurs and implies that still more dinosaurs might have been running around with downy coats.
                              Part of the tail of Sciurumimus under UV light.
                   The red arrow points to the long thin filamentous feathers on the tail

Sciurumimus is represented by a beautiful fossil of a very young animal that was discovered in southern
Germany a couple of years ago. The skeleton itself is wonderfully preserved, but under ultraviolet light,
a host of bits of soft tissues are visible including bits of muscles, skin and, most importantly, feathers.
The name Sciurumimus means "squirrel mimic" on account of the bushy tail and indeed the tail of this
animal has rather long feathers that would presumably have given that part of the animal a rather
squirrel-like appearance. Otherwise though it was decidedly un-squirrel-like, being a bipedal carnivore
and capable of giving a rather nastier nip than the average London "tree-rat". It's worth noting that
these feathers are more like thin filaments and would be hair-like in appearance, though of course birds
have many kinds of feathers and not just those associated with the wings. Sciurumimus would have
been more downy like a baby chick or shaggy like a kiwi or cassowary, than covered in a neat layer or
plumage like a pigeon or chicken.

What makes Sciurumimus potentially of great interest though is where it fits in the dinosaur family tree.
The authors themselves advise caution with their results, but their analysis suggests that Sciurumimus is
a megalosauroid dinosaur and thus from a group that preceded the coelurosaurs. In short, feathers may
have been present in dinosaurs earlier than previously thought and more dinosaurs may have had
feathers than previously thought. While it's sadly true that the best way to conclude this little piece is
the horrible statement that "more research is needed", this is an exciting development: feathers are
rarely preserved and every new find can potentially add much to our knowledge and understanding of
their origin and evolution. Sciurumimus provides not just a new data point in this ongoing process, but
an important early one and there is much more to come from this fossil and from feather research.

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