Laser Beams help Scientists Interpret Dinosaur Footprints
Trackways left by dinosaurs as they wandered across soft mud millions of years ago can provide palaeontologists with information on long extinct animal’s behaviour. Trackways are trace fossils, these preserve evidence of the activity of animals. Such sets of footprints can help scientists calculate the travelling speed, stride length and other characteristics of the animals that left them. If there are a group of footprints fossilised, they can provide clues to dinosaur herding behaviour. Trackway evidence suggests that sauropods (long-necked dinosaurs), moved about in closely knit and tightly grouped herds, with mature animals on the outside and younger, smaller animals on the inside. Large footprints on the perimeter of the group and smaller footprints towards the middle provide the scientific evidence to show that Sauropods moved around like this to give some protection to the younger animals within the herd.
Signs of heavily churned up sediments which contain Mesozoic fossils could have been caused by the trampling of large numbers of dinosaurs, for example, at what was a waterhole, or lake shore. This phenomenon is known as “dinoturbation”.
However, problems arise when geological processes lead to the movement of the strata so that they are no longer presented in a horizontal plane. There are a number of examples of this within the known fossil record, some of them are classified by Ichnologists (scientists that study footprints), as “megatracks”. A megatrack site is an area where dinosaurs have left footprints that have become fossilised across huge areas of land. Some palaeontologists believe that these sites represent migration routes, prehistoric trackways that may have been used by groups of dinosaurs following the rains, searching for fresh feeding or heading for breeding grounds. Some of these routes may have been created over hundreds of migrations.
One such dinosaur trackway site is at Fumanya in the south-east Pyrenees in Spain. Here the Cretaceous sediments have been raised up to a slant of 60 degrees and the trackways cover a distance of nearly 2,000 metres. The footprints have preserved the passage of a group of enormous titanosaurs as they crossed a muddy plain, (long-necked dinosaurs, the last type of sauropod to evolve).
Unfortunately, the footprint layer is very soft and crumbling and any attempt to climb the rock face to get a close look at the tracks could result in irreversible damage. To examine the tracks at a safe distance would have proved problematical but thanks to the ingenuity of the University of Manchester team given the job of analysing the prints, this difficulty has been overcome. The Manchester team scanned the rock surface and the prints using LiDAR, a laser mapping system that produces detailed 3-D images. The LiDAR system (termed LiDAR – Light Detection and Range), provided an accurate 3-D contour map of the site. This digital process represents a huge leap forward (no pun intended for the Ichnologists), compared to more traditional methods of study involving close physical examination and plaster cast copies.
The higher resolution and the accuracy of the images will help palaeontologists to better understand how these huge animals walked, which part of the foot was lifted from the ground first as a step was made and the role of the claws in helping to provide support and grip as these dinosaurs moved. The use of LiDAR in this way is an interesting application of the technology. It is used in geology and archaeological excavations as well as for traffic enforcement, where this system is used by a number of police forces to detect speeding motorists. LiDAR is able to detect and calculate the speed of a single car within a group of moving vehicles and in certain situations, it is the system of choice when compared to the more traditional RADAR gun.