the rest of the useful pics of F33 – sadly I only had a pretty bad digital camera available back than, one that had real trouble focusing through the glass.
F33 in dorsal view, anterior trunk. Note the vertically places scapulae and backward swept ribs.
Anterior view of the shoulder girdle and trunk, with the neck getting badly into the way
Right hind limb on dorsal view.
and the entire critter in right lateral view, in its new home (no longer on the wall, but on the ground).
I may have access to a really cool digitizing tool soon; if so this beast will be scanned all over!
The taphonomy of this individual is pretty cool, too. The scapulae are preserved practically vertical, with the coracoid overlapping. The ribs are swept way back, the limbs folded together under the body. The entire animal is perfectly articulated, except for post-mortem damage. I believe the sequence of events was as follow:
- the animal got stuck in the mud (see Sander 1992)
- it settled down when I got exhausted from trying to fight free
- it died and was covered before any scavenging could occur (if we assume that the tail got lost later), or was partly covered with the tail exposed and scavenged
- before the intercostal musculature and most of the ligaments and tendons could decay the body cavity was compressed dorsoventrally. The ribs, being in their natural position inclined backwards, shifted into a nearly horizontal position, dragging the semi-decayed shoulder girdle along. The tips of the ribs thus moves back & inwards, and this made the coracoids overlap and the scapula rotate into an unnaturally steep position.
- at the same time the limbs were folded from zig-zag to a stack of parallel parts. The hips got slightly flattened, making the pubes and ischia rotate with their proximal ends down while the distal ends stayed were they were, enlarging the angle between the shafts of ischia and pubes.
- final decay of remaining soft tissues and petrification of the bones.
All in all rather fortunate circumstances: the little bones that tend to shift around like carpals and tarsals stayed in place, and the ribcage didn’t “blow up”. Combined with the more common posture of animals on their sides or with at least the anterior body on its side this fossil allows a much better understanding of the overall appearance. For example, you can’t argue for a broader-than-high ribcage, because a broad-oval would have collapsed differently.
Sander, P.M. 1992. The Norian Plateosaurus bonebeds of central Europe and their taphonomy. Palaeogeography, Palaeoclimatology, Palaeoecology, 93:3-4:255-299.