Ray Stanford and some of his MD track slabs

Ray's baby ankylosaur skeleton Photo by Ray Stanford

As fabulous as these finds were, none compare to his 2012 discovery of an approx. 8 x 3 ft track slab, which is being hailed as one of the most important fossil finds of all time, and which came about through some odd coincidences. Ray first noticed a small patch of the rock poking through the grass near a parking lot at the NASA Goddard Space Center near Wash DC, while dropping off his wife Sheila, who works there. Upon brushing off the small exposure, Ray realized that it was a nodosaur track. This alone was a wonderful find, since nodosaur tracks are rare. It was also found in the nick of time, since within days NASA was planning to plow the area over in preparation for construction of a new building. After realizing the importance of the find, NASA decided to postpone the construction project and contract for the rest of the slab to be exposed, excavated, molded, and removed. During these activities, from which Ray was largely excluded, only one other large track (a sauropod front print) was noticed on the slab.

NASA Goddard track slab (top) and color diagram. Even more shallow and subtle tracks occur on the slab than are shown on the diagram. Adapted from illustration by Ray and Sheila Stanford

Fortunately, a cast of the slab was delivered to Ray's home for his study. As Ray examined it under angled lights, and gently sloshed onto it a solution of light-colored sediment to highlight its contours, he and Sheila began to spot more and more tracks and unusual features. Before long, they had recognized almost 70 tracks of at least eight different animals. These included baby nodosaur prints alongside the original large one, several small theropods trails taking very short steps (some with heel impressions), some bird-like tracks, pterosaur prints (wing, foot, and beak marks), three sizes and types of early mammal tracks (the most ever found on one surface--including the largest Cretaceous mammal track ever found), a sauropod front foot track, a possible crocodile track, plus a nodosaur scute, coprolites, and invertebrates (apparent insect larva). Many of these features appear to suggest interesting behaviors and interactions, such as a baby nodosaur walking with a parent, a group of theropods moving very slowly and in the same direction (possibly stalking the smaller mammals or avoiding the larger ones), and pterosaurs stabbing at insect larva, and hopping mammals.

In short, the find exhibits an almost unimaginable variety and density of tracks and behaviors on one relatively small slab, inspiring track expert Martin Lockley to call it the "Rosetta Stone of Cretaceous tracks." Ray himself calls it a virtual "time machine." The find has been featured in many news stories, and was described in the prestigious science journal Nature, with Ray and Lockley as lead authors.

The original slab has been moved to an undisclosed location, but the finished cast is now on display at NASA Goddard, where a grand-opening celebration was attended by many scientists and government dignitaries. I am trying to arrange a club field trip to see the Ray's finds, and am pleased to report that Ray has offered to give us a personal tour and talk.

The mind boggles at what might exist on even larger exposures of the track bed, which evidently once existed on the NASA properly. Sadly, except for a few small pieces, all other remains of the bed were long ago plowed up and dumped (or buried?) in unknown locations. Also unfortunate, the streams and creeks where Ray did most of his collecting have been covered over with concrete or gravel in the name of "flood control," even though this ended up only making flooding worse, while ruining the collecting and natural beauty of the streams, and wasting millions of tax dollars.

Large theropod and sauropod tracks, attributed to Acrocanthosaurus and Sauroposeidon Paluxy Riverbed, Texas. Photo by Glen J. Kuban, 2012

Some interesting comparisons and contrasts can be made between the Goddard slab and the Lower Cretaceous tracks I have been studying for many years in Texas, especially in and around Dinosaur Valley State Park near Glen Rose, Texas. Like the Goddard slab, many of the Texas sites show a remarkable variety and density of tracks. These include many striding trails of theropod and sauropod tracks, as well as elongate, heel-impressed tracks (once mistaken by some for "human" prints) apparently made by slender ornithomimid or "ostrich mimic" dinosaurs, a few ornithopod (bipedal, plant-eating dinosaur) trackways, plus various invertebrate markings and problematic traces, including large double-gouge marks, "swishes" and "squiggles" of uncertain origin. However, so far the Texas sites have not yielded any pterosaur or mammal tracks, and despite being almost the same age as the MD tracks, the Texas sites and individual tracks are typically orders of magnitude larger. Some of the TX sites cover areas larger than a football field, and even the smallest tracks on them are much larger than most MD tracks. A typical Texas sauropod footprint set (rear and front print) is almost the size of the entire Goddard slab. These astounding size differences may reflect differences in the average sizes (or growth stages) of the animals visiting each area, as well as preservational biases due to different substrates and environmental conditions. The MD beds are organic-rich ironstones, apparently formed on ancient river deltas, whereas the Texas track beds are mainly limestones, formed on vast mud-flats near a large, shallow sea.

I hope to give another NCFC talk later this year discussing recent discoveries and developments with the Texas tracks, including new efforts to save and further document as many tracks as possible as they continue to erode and break up, and to provide better track access and interpretation. Fortunately, the new state park superintendent (Kelby Bridwell) is very enthusiastic about these goals. It may help that a BBC documentary on T. rex behavior that was partly filmed in the park last summer (and is expected to be released in the U.S. soon), is drawing renewed attention to the track sites there. A film trailer shows me walking along and interpreting the longest trackway in the park (and possibly all of N America). with over 150 steps in sequence. Even though none of the Texas tracks were made by T. rex, some were made by a similar large theropod named Acrocanthosaurus atokensis. For more information on the MD and Texas tracks, including links to the Nature paper on the Goddard slab and the BBC trailer, please see: http://paleo.cc/tracks.htm