Faunal tracks and the discovery of swimming traces from the Middle Jurassic of the Yorkshire Coast
WAJ Rutter (UK)
On 2 June 2011, a large slab of faunal tracks was found in Scalby Bay, north of Scarborough (Fig. 1). These footprints were immediately recognised as not being dinosaur footprints due to the size, shape and distribution of the tracks. They were in a fallen block, which was identified as a layer in the Long Nab member of the Scalby Formation, as the horizon was visible approximately 60cm above the base of the cliff.
Several people were involved in the extraction and transporting of the specimen: Rob Clayton, Amy Parry, John Hudson and Tina Sleaford and me. Photographs of the in situ specimen were taken by Peter Sleaford (Figs. 2, 4, 5 and 6) and I drew a sketch diagram of the footprints (Fig. 3, based on Fig. 2). John Hudson later consulted a paper presented to the Yorkshire Geological Society in 2003, which contained a trackway classification chart for specimens found in the area (Romano and Whyte, 2003).
After examining the specimen in the light of the classification chart, we confirmed that the tracks were not made by a dinosaur. From the distinct differences in the tracks to those previously found in the area, we also deduced that these tracks were formed underwater in a river channel, which formed a part of the fluvial delta associated with the Middle Jurassic in the area.
Also from the classification chart, we came to a preliminary conclusion that the trackways were made by crocodilians and a Chelonian (a superorder which includes turtles, tortoises and terrapins). There is one possible Chelonian track and three possible crocodilian tracks. However, the three crocodilian tracks are not believed to be related to one another, as they are randomly aligned. That is, they are not a continuous set of prints and are not considered as parts of a continuous trackway. Several other tracks of a similar nature to these have been discovered a few miles along the coastline to the north, in a different formation, so these tracks are a significant discovery about the presence of different types of fauna present during this specific period of deposition.
The footprints are labelled in Fig. 3. as I, II and IV are all possible crocodilian tracks and III is a possible Chelonian track. Note that Fig. 3 is a sketch of Fig. 2, which shows the significant sections and helps to highlight the most important sections on the slab.
Many footprints are discovered annually and the area is world renowned for the quality of the remains of dinosaurs, reptiles and other fauna of the period that can be found here. Several types of fauna have been identified along this stretch of coastline and, generally speaking, are identified based on tracks and trackways. However, only one definitive ichnospecies has been labelled based on the footprints from the area, which is Deltapodus brodockii, made by a large Stegosaur. From the range and variety of tracks and trackways, it is thought the area was a large migratory route for land-based creatures.
Just a pause for thought – if 160 million years ago, there were large reptiles and dinosaurs roaming the land and they left behind their footprints, will we get chance to leave physical footprints for 100myrs rather than just a layer of concrete?
References and further reading
Romano, M. and Whyte, M., PYGS Jurassic dinosaur tracks and track-ways of the Cleveland Basin, Yorkshire: preservation, diversity and distribution, 2003.