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Sinopterus, a closer look

Sinopterus has just gone under the tracing and coloring mouse and some
surprises popped out.

1. The ilium is quite long ~ half the torso ~ an anterior tip peeks out
from in front of the left elbow and a similar impression shows up in the
dorsal series.

2. The sternal complex is transitional between the germanodactylid shape
and the dsungaripterid/tapejarid/pteranodontid shape. In the former, the
posterior edge is a big round curve. In the latter it is squared off. In
Sinopterus the lateral edges are straight, but they converge on a short
transverse posterior rim. Plus the cristospine is short and wide, which
may be the juvenile state. Overall it resembles an equilateral triangle
with the back tip cut off and moved anterior as the cristospine.  : )

3. That big globe inside the orbit is a dang big sclerotic ring,
together with an assortment of rod-like pterygoids and ectopalatines
(combo bone). This is confirmed by the presence of another big sclerotic
ring anterior to the left femoral head (surprise!). Either that or its
another dang Anomolacaris mouth piece.

4. The mess of a pelvis illustrated by Wang, et al. has some real
structure. A fused sacrum of 5+ verts is seen in ventral view. Two big
long-stemmed prepubes are visible. The femoral head is displayed so the
slender neck is pointed anterolaterally, disarticulated just outside the

5. The pelvis is unnaturally close to the sternum (elbows and ilium
overlap), so the difficult-to- make-out vertebral column must be sinuous
underneath it all.

6. The dorsal ribs are mostly missing, but many have drifted to the
pterosaur's far right (stage left). Others are caught beneath the
sternal complex and along the right antebrachium where some look like
the pteroid.

7. The pteroids are longer than half the radius in length.

8. All three manual digits and all their phalanges are visible on the
pterosaur's right. Digit one is twisted within the other ones and the
ungual is disarticulated.

9. The scapulae were drawn way too wide. The left one left impressions
beneath the sternal complex. Both are short and no doubt attached to the
vertebral column.

10. The tail bones, at least some of them, can be found near the left

11. The right metacarpals appear to indicate that 1 reaches the carpus,
but 2 and 3 reach only about 3/4 of the way back.

12. The feet are still too poorly preserved to make out, but their
length relative to the tibia remains shorter than in any tapejarid, but
longer than in Noripterus, a dsungaripterid.

13. The quadrate, or part of it, is inverted alongside  cervical 3.

14. The postorbital process of the jugal is robust. I haven't found the
postorbital or squamosal. The entire cranial portion of the skull was
shifted forward during taphonomy a distance starting from the impression
left behind the skull in situ.

15. Cladistically Sinopterus moves to the basal Tapejaridae, only one
step removed from the basal Pteranodontidae.

JPGs, both insitu and bipedal, free for the asking.

David Peters