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Hello Dwight, Jack, and List, It has been several days, Dwight, since you asked another good question about what might be determined from study of dinosaur trackways. So, for those who may have forgotten the question, I'll repeat it: -----Original Message----- From: Stewart, Dwight <Dwight.Stewart@VLSI.com> To: 'STARSONG@prodigy.net' <STARSONG@prodigy.net>; jconrad@lib.drury.edu <jconrad@lib.drury.edu>; Dino mailing list <dinosaur@usc.edu> Date: Tuesday, February 23, 1999 10:46 PM Subject: RE: thanks for tracks & a question "Okay, this brought a question to mind that was rattling around in my head a few weeks ago. To whit: can anything be inferred about dinosaur mass/weight from the prints, aside from the "wide/narrow" gauge artifact you just mentioned? Here, I was thinking of forensic work as the model, in that the approx. height & weight of a human can be derived from shoe size, stride length, & the depth of the tracks. Now, I realize that preservation conditions would greatly complicate this, as would the question of under track, over track, etc. But, nevertheless, it seems intuitively feasible." Yes, forensic work does provide a good model of ways to derive a maximum amount of data especially from trackways, but even from singular tracks, in some instances. Of course, as you mention, the derivations will be more accurate when one is working from prime tracks, rather than under-prints, over-prints, etc. A good reference on matters related to this is a small but very useful little book entitled, DYNAMICS OF DINOSAURS & OTHER EXTINCT GIANTS by R. McNeill Alexander, and published by Columbia University Press in 1989 (ISBN 0-231-06667-8). Yes, 'ball-park figures' for an animal's velocity (or lack of it) can be derived from trackway (or track) studies. Of course, trackways are best for this, but singular tracks can reveal certain limited data. In the latter case, for example, I have found several Theropod tracks (various types and sizes) in which an animal was making a very fast change of direction. One can easily determine by observation, the degree to which the foot was tilted (relative to the horizontal layering of the sedimentary substrate) during the turn, the amount of substrate that is pushed up by the centrifugal force involved at the moment of turn. Then, from these observations and other data (and calculations) one can come up with reasonably reliable figures for substrate penetrability and compactibility at the time of the event, the animal's approximate mass, and probable velocity, etc. Two of the things that have surprised me about some of the Theropods from Maryland's Early Cretaceous is that apparent speed and agility. Then, there are the several tracks possibly made by Dromeosaurs with that second-digit's 'terrible claw'! I had never thought about the tip of this claw being so knife-blade thin and awesomely sharp (probably because I'd been thinking mainly in terms of the claw bones we see, instead of the much longer, sharper keratinous sheath that surrounded it in life), but a couple of the tracks I've found here leave no doubt in my mind that this particular Theropod was truly a 'Jack the Ripper'. There are a few tracks with substantial amounts of 'splash-out' , suggesting a surprisingly high-speed run in very wet soil that was not -- all the same -- covered with water (or the splash drops would not look as they do). I hope this provides some insight, and I shall forgo quoting any of the formulae Alexander provides in the book mentioned (or any of the others available in various publications). Some work has already been done to extrapolate quantitative data from trackways, but it seems to me that this is a fairly new field of endeavor, with much more potential than what has yet been realized, especially if one uses sophisticated computer software designed for modeling the action and its effects. I'm not as yet aware of any off-the-shelf software specifically designed for this kind of work, but I suspect there are some extant software that could help in (or be modified for) this type investigation. One area in which I use computer technology to study tracks (and the few small trackways available to me) is via IMAGE PROCESSING. Enhancement sometimes reveals meaningful details that had not been noticed before. It also has enabled less-experienced observers to readily perceive details of, and hence to interpret the tracks with more insight. So far as I know, I am the first track researcher to utilize this helpful innovation in study of mesozoic tracks. Relevant to this: Several summers past, I had time to do some dinosaur tracking in Texas, where I found something so surprising and exciting that I slept very little for a couple of weeks after the discovery : The short trackway of a HATCHLING Sauropod from the Comanchean (Lower Cretaceous) of Travis County, consisting of three clear imprints and a fourth (right manus) that is less clear and possibly distorted by the right pes (back foot) coming down too close behind that right front foot. In other words, there are two superb (shallow but beautifully detailed) left and right pes (back foot) imprints, and one equally superb, right-manus imprint, along with the much-less clear right manus (front foot) impression. Dimensions? Well, each of the two pes impressions is only 5.8 cm in length, while the manus measures only 3.0 cm in width! These beautiful little tracks are recorded in a carbonate (marine lagoon) substrate, and are the first hatchling sauropod tracks documented anywhere. If we take the typical Paluxy Sauropod pes length to be 85 cm long, then at 5.8 cm, the Travis county hatchling pes is only 1/14.6th of that size! Image enhancement of a photo of this track-bearing slab made the tiny Sauropod tracks show up ever more marvelously, revealing some details that had not been noticed before enhancement. Those tiny Sauropod tracks are virtually identical in form (but not in size, of course) to the best of the Paluxy river-bed tracks of Texas, except that the four sharp claw marks on each pes imprint (the 5th toe seems represented only by a bulge of the foot flesh positioned externo-laterally to toe 4) seem to have been made by claws even shaper and, relatively, longer than corresponding claws in imprints made by the more-adult Texas sauropods. Dr. Robert Weems of the U.S. Geological Survey, Reston, Virginia, has speculated that long, sharp claws on the hatchling Sauropod may have been useful in escaping from the egg shell when hatching time came, and that the claw sharpness probably diminished as the hatchling walked more and more in silt, sand, or across pebbles, thus the sharpness of these claws suggest that this particular track maker was very recently hatched. Some skeptics out there who have not had the chance to see these tracks, might wonder whether, knowing the shapes of the Larger Texas Sauropod tracks, some of us might have just imagined that random forms in the carbonate substrate look like the Paluxy Sauropod tracks. Well, seeing them would take care of that; but since I cannot include illustrations or photos in postings to this list, I shall mention one other nice advantage of computerized image processing: Using absolutely none of the artwork capabilities of the computer, but using a series of commands that are computational, only, I had my system look for and draw the outlines of whatever forms it detected on the slab. Really, to my astonishment, it drew ever far better outlines of the Paluxy-like hatchling tracks than I had even imagined (in my wildest hopes) it would do! My point? My computer was not fantasizing Brontopodus birdi type tracks, as a sight-unseen skeptic might speculate those of us here had done. Excellent images of many of the small to medium-sized tracks can be obtained by simply scanning them on my flat-bed scanner, which has a very surprising depth of field. This provides a quick and easy way of cataloging the collection with high quality color photos that include size-reference objects. That's it for now. Ray Stanford |