RE: Dromaeosaurus Tracks?

[Dino Guy Ralph <dinoguy@sbcglobal.net>]

See http://www.sedgwickmuseum.org/exhibits/dinosaurs.html , which includes
an illustration of a dromaeosaur #2 phalanx (toe).  Surely you have seen
illustrations like this in dinosaur books by David Norman or Gregory S.
Paul.  The toe bones permit an extreme degree of movement both fore and aft
(hyperflexion and hyperextension).  Typically, bones do not articulate in
such a way unless this degree of movement is used by the living animal.  It
is hypothesized that elastic ligaments would hold the #2 claw up off the
ground while walking, running, or resting -- somewhat in the manner of the
retracted position of a cat's claws (cheetah claws and dew claws
notwithstanding).  When pressed into service, a tendon attached to the
flexor muscles of the lower leg (the drumstick) would pull on the flexor
tubercle (the knobby protrusion at the forward base of the claw) to flex the
toe.  

There is some disagreement about the type of wound a dromaeosaur claw would
inflict -- which would depend largely on the unknown geometry of the keratin
sheath that covers the bony claw core (as a complete dromaeosaur keratin
claw sheath has yet to be recovered).  In order to "slice" through prey, the
claw would have to be very sharp on the underside.  But even such a claw
which is not sharp on the bottom could presumably do considerable damage by
nature of its sharp point, its laterally compressed hooked shape, and the
strength of the leg muscles.  A cassowary sports formidable claws on its
feet, and can inflict serious wounds when it is threatened in spite of the
claws not being particularly sharp.  The famous "fighting dinosaurs" of the
Gobi preserve a snapshot of _Velociraptor_ imbedding its killer claw into
the throat of _Protoceratops_, so it is doubtful that the claws were merely
for display.

I suggest reading through the chapter on dromaeosaurs in Gregory S. Paul's
_Predatory Dinosaurs of the World_ for further information.
   
Dino Guy Ralph
Docent at the California Academy of Sciences
Dinosaur and Fossil Education
Member of the Society of Vertebrate Paleontology