Epidendrosaurus Features

["Jaime A. Headden" <qilongia@yahoo.com>]

Thought I'd take this moment to talk about some peculiarities of
*Epidendrosaurus ningchengensis*. Glad first of all to see some sub-Jehol
lagerstätt fossils.

  Anyways, aside from the manus, the next most peculiar features about
this animal is the pes. In this, the shortest main metatarsal is IV, and
I, II, and III are all even in the distal articular ends. The first digit
faces the same way as the other digits on both pes. Part of a manual digit
appears to lie above the right pes in direct line to the first toe and
metatarsal, but the position of the first toe in the other pes suggests
this is not likely a reason to doubt the position of the first toe in that
first foot. The fourth toe is very wierd in that the phalanges follow a
pattern of 1:.65:.7:1.25, and oddly avian in this measure if it weren't
for the extra fourth-digit phalanx (birds have only four, not five, fourth
pedal phalanges). The limb proportions are nearly even, with the femur
estimate at a length just under the tibia, and the femur only slightly
longer than metatarsal III, but the latter is more than 75% the tibia
length. Such hindlimb features are suited to arboreal animals, btw.

  The skull is remarkable in that the lower jaw, if correctly identified
in its entirety, is the length of the frontoparietals. More likely these
represent just the dentaries, but as I have only a vague photograph and
the lamentable typical line-drawing to work from, I cannot judge the
accuracy of either opinion. The dnetition is largest mesially and
rostrally, and is apparently procumbent. A completely fused and
undifferentiated scleral ring makes me doubt it's authenticity, and I
wonder at what other animals are present in the Daohugou fauna that could
produce this. If a scleral ring, its autapomorphous. The frontals form a
T-shape in dorsal aspect, and there is a deep caudal separation that
suggest they have been flattened from a normally high-domed position. The
parietals are very quadrate in form without much lateral concavity; they
also appear to be formed from the ventral impression of the fused pair,
instead of being a naturally preserved bone. Nonetheless, the
supratemporal fossae do not incur medially, and the parietals are wider
rostrally than caudally. The orbits were huge, with the frontals, which
are caudally wider than the parietals were at their greatest width, being
nearly 850% wider caudally than between the orbits. The frontals also
appear to have been formed from impressions of the ventral surface, and do
not conform otherwise to dorsal frontal surface architechture.

  The coracoid is semilunate, and strongly concave on its ventral margin.
The scapula and coracoid are not in natural position, but are flipped on
their long axis, so that the ventral margin faces dorsally. Nonetheless,
it is a very plesiomorphic shoulder in this respect, with an expanded
ditsal end, very short relative to the humerus, and an apparent acromion
that is deeply emarginated from the unfused coracoid. The coracoid was
inline with the scapula and did not decline from the axis at all,
apparently. The forearm is shorter than the humerus, and the humerus
itself has a small deltopectoral crest. 

  The authors provide for 9 cervical vertebrae and point to a long
structure as the cranial dorsals. This is formed from an series of
vertebrae that resembles a notarium at first glance, and the authors
illustrate it this way, but not, I think to provide it as a notarium-like
structure at all. Though they cannot differentiate vertebrae, there are
distinct vertebral choanae. Ribs are simple and all are as long as the
cranial most, but are preserved as impressions. Continuations are not
noted, nor are broken ends.

  The skull features remind me of some pterosaurs, and I am curious as to
the pes also having these similarities. The humerus is not in the least as
what is seen in flight-adapted animals without an everted caput or distal
end, and the deltopectoral crest is very proximal. I seriously consider
the likelyhood of the "third" digit to be problematic in identifying the
third metacarpal, which the authors assign to a single lone elem. If
missing, the third metacarpal may be the element the authors identify as
the first phalanx of the third digit (mdIII-1), but nothing explicitly
provides actual structure of the manus but for the proximal ends of two
metacarpals (?) the authors illustrate near the identified first digit.
Parts of both manus are present, and I do not think the authors did a good
job of trying to accoutn for both manus as would make me happy. A long
impression extending from three centra is identified as the tail imprint,
and this is longer than 6 times the preserved jaw length and over 150% the
hindlimb length. It continues off the slab.

  No integumentary impressions are present, and I am hard-pressed apart
from some appendicular proportions to find anything birdlike about this
animal. In fact, the scapular morphology in context with the bizarre pes
makes me curious about possible dinosauriform, basal pterosaurian, or
*Scleromochlus*-type relationships. I would need better photographs. The
specimen is a apparent juvenile, and the huge head is accounted in this
manner, along with the apparent juvenile periosteum and under-developed
epiphyses of the limb bones. A supposed distal tarsal, well defined toes
and large claws, ossified scleral ring, appear to argue against this. it
is not apparent, and may be impossible to tell, about neurocentral fusion.
All well apparent ventrebrae are presented as either dorsally-viewed
cervicals, or ventrally-veiwed caudals, unrevealing in fusion in the
slightest.

  This is not, btw, the same specimen as the Chinese specimen Czerckas
has, though some features (supposed third finger in this specimen, actual
third finger in Czerckas'; pes morphology) are in general agreement; some
features are not, included supposed tail anatomy, manual ungual morphology
and proportion, etc. I am curious why, when the "Archaeoraptor" elements
were repatriated, this specimen was not? By Chinese law, any fossils from
China belong to _China_ and cannot be bought or sold. It is better
articulated than Czerckas' specimen, though, but not as well-preserved.

  Cheers,
  

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

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