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Here's another from the same paper as
Tugulusaurus. It's been called a dromaeosaurid, but is it?
Phaedrolosaurus Dong 1973
P. ilikensis Dong 1973
Etymology- "shining lizard", from Greek
phethon.
Early Cretaceous
Lianmugin Formation of Tugulu Group, Xinjiang,
China
Lectotype- (IVPP V
4024-1) (~7 m) tooth (31 mm)
referred- (IVPP V 4024-2) (2.5-4.2 m) tibiotarsi
(320 mm)
(IVPP V 4024-3) proximal femur
Diagnosis- anterior serrations basally absent but
tooth mediolaterally thicker than Deinonychus, Saurornitholestes, Velociraptor
or Ricardoestesia (provisional diagnosis, may be nomen dubium).
Description-
This description is plagued with the same poor
translation and figures as Tugulusaurus. The tooth is about twice the size
of Deinonychus, which would indicate a theropod about seven meters long.
The tibia would indicate an animal 2.5 to 4.2 meters long, depending on what we
scale it to.
The holotype is a tooth whose outline is near
identical to Deinonychus (fig. 23A in Ostrom 1969). It is compressed,
recurved and serrated like most theropods. Serrations extend from the base
to the tip of the posterior carina, with eighteen serrations per five mm.
The base of the anterior carina is smooth, but serrations are present starting
half way up. It is said to be thicker than Deinonychus teeth.
The proximal femur is briefly mentioned, but not
described or illustrated. It was found at a separate site, so should not
be regarded as Phaedrolosaurus. Barsbold and Osmolska (1999) note that
this femur has a wing-like lesser trochantor.
A pair of tibiotarsi were found in the same
horizon, but again at a different site, and referred to Phaedrolosaurus.
The tibia is fused with the fibula and astragalocalcaneum. It is fairly
straight in anterior(?) view and expands proximally. The distal end
differs from Deinonychus and Velociraptor in that the calcaneum projects
strongly laterally and there is a pronounced step in the lateral projection of
the astragalus. The tibia is said to have a conspicuous cnemial crest and
be round in cross section. The fibula is very slender and extends to the
calcaneum. It is described as having a deep proximomedial fossa and a
jacent process (tubercle for m. iliofibularis?) that becomes a ridge at the
outer margin. The astragalus has a high ascending process.
Relationships-
Both Molnar (pers. comm. to Glut 1989) and Sues
(1977) state that Phaedrolosaurus appears dromaeosaurid. Barsbold and
Osmolska (1999) say the wing-like lesser trochantor is distinctly
non-dromaeosaurid. Besides these opinions, authors have generally just
placed this genus in the Dromaeosauridae without question. Let's compare the remains to dromaeosaurids.
First, note that the tooth, femur and
tibiotarsi should not be regarded as pertaining to the same species as there was
no association. The tooth shares the lack of basal anterior serrations
with dromaeosaurids, but other groups as well. Nothing in it's basic
morphology prevents it from being a dromaeosaurid tooth. The wing-like
lesser trochantor is unlike the finger-like trochantor in dromaeosaurids.
The tibia is fused with the fibula and astragalocacaneum, unlike
dromaeosaurids. The deep proximomedial fibular fossa is a plesiomorphic
character lost in dromaeosaurids. Phaedrolosaurus does have a high
ascending process and fibular-calcaneal contact like dromaeosaurids, but these
are coelurosaur symplesiomorphies. So, while the tooth might be
dromaeosaurid, the limb elements are most certainly not.
The tooth, which is the only element that should be
referred to Phaedrolosaurus, is finely serrated, compressed, recurved and lacks
basal serrations anteriorly. The only theropods with these characters are
dromaeosaurids, Ricardoestesia and compsognathids. Unfortunately, basal
coelurosaur teeth are very rare and undescribed for the most part and
Ricardoestesia's affinities are unknown. Pheadrolosaurus is probably
either a basal coelurosaur or dromaeosaurid, but exact relations cannot be
determined at this time. The tooth is said to be thicker than Deinonychus
and Velociraptor. This would also imply it is thicker than Ricardoestesia
and Saurornitholestes. Perhaps it is a diagnostic character. If not,
one should wait for a detailed comparison of dromaeosaurid teeth (serration
frequency, morphology, cross-section) until such a taxon is declared nomen
dubium.
The proximal femur referred to Phaedrolosaurus is
not oviraptorosaur or eumaniraptoran, as these groups have either finger-like or
fused lesser trochantors. The lack of further information makes a more
exact placement impossible, although this would allow the possibility of a basal
coelurosaur affinity. In this case, it could come from
Phaedrolosaurus.
The tibiotarsus has a deep proximomedial fibular
fossa, which is unknown in maniraptorans except for oviraptorids. The high
ascending process is characteristic of coelurosaurs. The presence of
fibular-calcaneal contact eliminates some derived eumaniraptorans (mononykines,
troodontids, Rahonavis, pygostylians). The presence of a fused
astragalocalcaneum, which is also fused to the tibia, is only known in some
maniraptorans. Thus, at first glance, the deep proximomedial fibular fossa
and fused tibiotarsus seem to be mutually exclusive in theropods (the first
being absent in maniraptorans and the second present). Oviraptorids are
the single maniraptoran group with a deep proximomedial fibular fossa and a
fused tibiotarsus. Are these tibiotarsi from an oviraptorid? Nothing
contradicts this, although better support would be preferred. This is
because the fused tibiotarsus may be age-related and have a wider distribution
than currently thought. Thus, I recommend the tibiotarsi be classified as
a non-eumaniraptoran coelurosaur, possibly oviraptorid. These specimens
could therefore belong to Phaedrolosaurus, if it is a basal coelurosaur, but not
if it is dromaeosaurid. If the tibiotarsi are oviraptorid, they certainly
could not be Phaedrolosaurus. They could also hypothetically be from the
same species as the proximal femur, if they aren't oviraptorid. It
might be noted that the tibiotarsus is diagnostic, possessing a distinctly
medially projecting calcaneum, similar but more extreme than Nedcolbertia,
Harpymimus, Aublysodon and Tyrannosaurus.
Those of you who want figures of the tooth and
tibiotarsus (one page), contact me offlist. Next I'll do Nanshiungosaurus
bohlini. Is it Nanshiungosaurus? We'll find out soon.
Mickey Mortimer
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