So having covered ornithischian ossified tendons it’s time to switch to the other side of the dinosaurian tree and take a look at the hyper elongate zygopophyses of dromaeosaurs. This is a bizarre feature of dromaeosaur tails where the (normally) little articulation points between vertebrate (the pre and postzygopophyses) are elongated such that they overlap other individual vertebrae rather than just articulating with each other. The postsygos (at the rear) are only mildly elongate compared to the truly mammoth prezygos which can overlap half a dozen or more bones.
Here, several have become disarticulated so that the individual shafts of the zygopophyses stick out free of the tail making them more visible. Just about visible (it’s not the greatest image) is the fact that these are part of the vertebrae and continuous with them and are not separate elements as are the ossified tendons of the ornithischians. A good look under a microscope makes that pretty clear, though of course a bad photo shot through glass in a museum doesn’t always. Also worth noting is the fact that under the tail, the chevron bones are also massively elongated too.
It’s tempting to assume that this makes the tail an incredibly stiff rod-like structure and this has been suggested in the past, but this is not likely to be the case. For a start this specimen is hardly unique in that the bones have separated out from each other even when the rest of the skeleton remains articulated, so clearly if even a fairly mild disturbance after death can move the bones around, then in life there must have been a degree of flexibility. Secondly, other specimens are preserved with the tail flexed to a degree suggesting that things are not that rigid. Finally, it’s pretty unlikely that the whole thing was exceptionally rigid as this would make it prone to breaking – even our own long bones can flex at least a bit when stressed without snapping, and some long and thin bones (like this one for example) pretty much must have had some flexibility or they’d break constantly – bones are not always very rigid (and indeed as an aside, bat bones are incredibly flexible). So while the tail was undoubtably stiffened, it was unlikely the flag-pole that some people think it was.
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