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Hi Ralph and other interested
persons,
You
(Ralph) said, "It surprises me that the tracks reveal the "terrible
claw" at all; articulated dromaeosaur specimens have preserved the digit in
a hyperflexed pose. If the claw were habitually extended during
locomotion, contact with the ground would cause wear on the tip, blunting the
ungual phalanx and rendering it less useful as a
weapon..."
Precisely, as appears to be the case in the seeming Dromeosaurid tracks found in
Maryland, and you've correctly deduced a major reason why, in these rare
instances, the "terrible claw" impression is recorded:
You (Ralph) wondered, "Would you interpret these tracks to have recorded the digit AS A CONSEQUENCE OF THE SUBSTRATE BEING PARTICULARLY SOFT (CAUSING THE FOOT TO SINK IN DEEPLY), [MY emphasis. -- Ray S.] as was apparently the case with numerous theropod tracks which preserve some impression of the #1 digit (even though it was probably held off the ground)?" In the case of the left (as contrasts with the right) unassociated pes imprint, the foot sank as much as 6 cm down, rather deep for a pes only 9 cm long! In this case of deep penetration, basically the whole 'pocket' made by the 'terrible claw', along with its 'pull-out-of-the-muck' withdrawal pattern, are recorded! In this case, the 'terrible claw' rotated posterio-medially, leaving its passage recorded for 'eternity'. (O.K. Let's be conservative, 100+ million years in not really an eternity!) This particular imprint will be CT scanned (possibly this week if I get time) at a cooperating local hospital, in order to try and provide us with a nice image showing both the outside and INSIDE shape of the terrible claw's pocket and withdrawal pattern, for use in publication. Of course, one can just look into the imprint and see much of the inside of the 'pocket', but for purpose of publication, a CT image will be much better. If the CT scan effectively renders the internal image with sufficient resolution -- considering this imprint is naturally glued together by a dark-colored, very dense iron compound -- then the hospital administrator says we may be able to use the system to render a 3-D graphic of the entire print! You can imagine why this gets exciting. As to the right pes print, it is also 9 cm long; but in this case the foot only sank down an average of 1 cm. And, it was apparently only when the back of the foot was lifted (pushing the toe tips deeper) that the very sharp terrible claw's tip penetrated the substrate and left a very long (5 cm), narrow slice extending (as view dorsally) posterio-laterally, beginning with a initial and broader substrate penetration pattern of, roughly, 'diamond' shape. But what makes this even more dramatic is the fact that one not only sees the sharp terrible-claw cut (visible both from the upper side AND from the bottom side of the substrate in which it is recorded), but that the (apparently gooey, marshy, and, thus, rather coherent) WHOLE SUBSTRATE AREA THROUGH WHICH THE CLAW PASSES IS LIFTED DRAMATICALLY UPWARD, instead of being depressed as by the other two toes! This also shows up clearly and dramatically when viewed from the bottom of the substrate, as well as from the posterior end of the print. A few seemingly TWO-toed tracks I've found could be examples of this same type animal walking with the terrible claw completely off the substrate. In a few instances, there in only an odd depression at what should be the base of a toe #2. I wonder whether that could be an impression of the probably somewhat enlarged PAD beneath the remarkable 'hyper extendable' joint construction of toe # 2. Then Ralph asked, "Does the track show only the tip of the claw or the entire toe?" Oops! That's been answered, de facto, and the answer is BOTH, but in different situations. Last question: "When are you going to publish?" The CT scan comes first, in case it will help illustrate the internal morphology of that particular left-pes track. Then, after further analysis, I'll seek to illustrate and describe these tracks for publication, but as yet I have no idea as to how, where, or when. Any suggestions from those experienced in these matters? I'm just an amateur trying to open a bit more of the 'lost world' of Maryland's Cretaceous dinosaurs, feeling fulfillment in it, and deeply appreciative of the encouragement, insight, and help already received from professionals who examine the still-increasing evidence. I'll admit, however, that being vastly inexperienced, I'm a little intimidated by my ignorance about the formalities of writing a report for a truly scientific publication. Thanks for asking about this, Ralph. It helps me to clarify things that were not clarified in my earlier posting.
Ray Stanford
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