Monday, October 14, 2013

Tracking Dinosaurs

The problem with tracking dinosaurs is “what happens when you find one”?

 By our very nature, “trackers” track. We can’t help it. For some, it is an obsession. Some groups such as search and rescue, law enforcement and military trackers, track people. Others, such as naturalists, biologists and hunters track animals; but did you know that there is a very specialized group of trackers who actually track dinosaurs? These scientists study fossilized dinosaur tracks. Their mission is to sleuth out not only what dinosaurs actually looked like, but how they lived.

There are a number of sites in the world where dinosaur tracks are found, and Tuba City Arizona is just such a place. The tracks are located 6 miles east of highway 89 on Route 160. I couldn't help but notice a large home-made sign on the south side of the highway that said, "Dinosaur Tracks" (right around mile marker 316). Actually the word "dinosaur" was misspelled on the sign but I got the message. The track site is located about 600 feet down the dirt road to Moenave that heads north from highway 160.  At the site, there are crude kiosks manned by indigenous Navajo native Americans who are more than willing to show visitors the tracks as well as fossilized dinosaur remains.  A tip is expected - and with my guide...well deserved.

The day that I was at the dinosaur track site, the wind was gusting to over 40 miles per hour. As the area is sandy desert, this amounted to being painfully sand blasted. I would really like to return to the site to study and measure the tracks in more detail – hopefully, it will be a day without the strong winds.

The first thing about the location that caught my attention was the lack of controls or security for the fossils. I suspect that there are very few dinosaur track sites where one can actually walk among the artifacts. The second thing that becomes immediately apparent is the number of fossilized tracks; there are literally hundreds of them.

Dinosaur tracks are considered to be “trace fossils”, also referred to as ichnites or ichnofossils. Trace fossils are formed while the ancient animal is still alive.

As a tracker, it was exciting to see a number of successive prints just waiting to be followed. One set of prints I found had at least seven consecutive footfalls. In the jargon used by the scientists, a series of two or more consecutive tracks is called a “trackway”. While we are discussing jargon, “Paleoicnologists” is the term used for the scientists who study these ancient trace fossils.

While checking out the stride and straddle, it is quickly observed that the stride is quite long. According to formulas developed by R. M. Alexander and others (Alexander, 1989) the estimated speed of travel can be calculated by comparing the length of the footprint to the pace distance. Basically, if the length of the pace (distance between successive prints) is approximately four times the length of the actual track print, it indicates that this animal was running. Although this trackway’s prints were not quite the four to one ratio, it is close enough to consider that this animal was moving quickly.

Subsequent research indicates that the tracks were made by a three toed, bipedal, meat eating Theropod from the lower Jurassic period (between 199.6 and 175.6 million years ago). There were a number of similar tracks of varying sizes in the area ranging from eight to fourteen inches long with strides reaching up to about four feet. It was interesting to see that there was not much straddle. This would indicate a fairly narrow pelvic girdle.

The foot falls were neutrally aligned (no toe in or out). It would be interesting to find out if a dinosaur’s gender can be indicated by “toe-in” like with gender differentiation of ungulates - such as deer.

Although technically a four toed beast, the fourth toe of the Theropod is more like a dogs dew claw and not part of the track. According to Tracking Dinosaurs, by Martin Lockley (1991) the odd number of toes in the track indicates that the dinosaur did not have any horns - or if it did - the horn (or horns) would be located midline on the skull such as the horns found on a Rhinoceros. I didn’t notice any sign of tail drag although I suspect that all bipedal dinosaurs would have had a tail for balance. In a couple of tracks, a distinct claw on each of the three toes is observable. I wonder if claws are found on all dinosaurs or just on the carnivorous species?

With so many unanswered questions, the field of dinosaur tracking is certainly worth investigating further.  However, it really doesn’t matter what your specialty is in tracking.  If it is true that “trackers” track, then we should be able to study any track and get a better understanding of what made the “sign”. You don’t have to be a scientist to study fossilized dinosaur tracks, just a tracker.

Just imagine tracking something that existed 200 million years ago…unbelievable. But after all…Adventure is where you find it.

Bart Bjorkman
Northern Tracker

One of the best sites that I found on the internet about tracking dinosaurs is by Glen J. Kuban