[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Modern feathers on a non-avian dinosaur - today's Nature



Tim Williams wrote-

> The tail is proportionately longer than in NGMC 91 (which the authors say
"can probably > be referred to _Sinornithosaurus_")

Ooh.  How surprising ;-)

> BPM 1 3-13 shows several advanced
> osteological features (stiffened dromie-like tail; "sickle-claw";
> hourglass-shaped sternum composed of two sternal plates and with sockets
for
> the sternal ribs; semilunate carpal that caps mc's 1 and 2), but lacks
> avialan features such as unserrated teeth, short tail, and reversed
hallux.

The authors refer it to the Dromaeosauridae, although they must have a very
broad definition of the clade, differing from the accepted Dromaeosaurus +
Velociraptor definition.  The characters they cite are characteristic of
more inclusive clades-
- elongate prezygopophyses and chevrons (Eumaniraptora- reversal in Aves and
Rahonavis)
- retroverted pelvis (Maniraptora- reversals in oviraptorosaurs and derived
troodontids)
- sickle claw (Troodontidae, Eumaniraptora- reversal in Aves)
And to distinguish it from avians-
- non-reversed hallux (more basal than avians and Microraptor(?))
- serrated teeth (more basal than avians)
- long tail
This deserves a bit of comment.  The tail is approximately 6 times the
femoral length, though photo quality gives this a wide error bar.
Archaeopteryx does have a shorter tail (3.8 times), but it's longer than
non-avians like ornithomimids (3.5-3.6) and enigmosaurs (1.2-2.9).  As
Shuvuuia, Sinornithoides, Rahonavis, cf. Sinornithosaurus, Microraptor and
Rahonavis also have shorter tails, while Deinonychus has a long one, the
elongate tail might actually be evidence to include the new taxon in the
Dromaeosauridae, or at least the Deinonychosauria.  However, some basal taxa
(Compsognathus, Sinosauropteryx, Ornitholestes) have elongate tails too,
although others (Tyrannosauridae) don't, so this needs further study.
Besides what the authors mention, there is not much observable about the new
specimen.  Why couldn't Norell et al. have included a line drawing?  I
suppose it is just a brief communication....
Measurements- tail (~435 mm), humerus (~75 mm), ulna (77 mm), manus (~100
mm), femur (~75 mm), tibia (128 mm), metatarsus (68 mm)

Mickey Mortimer