A scenic insight into the living environment of the Cretaceous period: around 129 million years ago, a two-legged dinosaur with a pathologically deformed foot was walking in what is now Spain, as the examination of a fossil track shows. Apparently, the animal compensated for its disability when walking, as is still typical today for birds with injuries or deformities on the foot, as characteristic analyzes of the track suggest.
Bones and other remains are usually the focus of paleontologists, but in addition to these fossil relics there are also traces that come from the animals of the past: At some sites around the world, fossilized footprints of dinosaurs and other creatures testify to prehistoric times. They can provide insight into the characteristics and movement patterns of these animals. For example, body heights and running speeds have already been read from tracks. In the current case, however, the study results enrich knowledge about the health problems that once affected dinosaurs.
An asymmetrical track
In the sights of the paleontologists around Angela Buscalioni from the Autonomous University of Madrid was a fossil track that was discovered in Las Hoyas in Spain in sedimentary rock. Numerous footprints are already known from the site, which originate from dinosaurs that walked over the soft ground there about 129 million years ago. But the track, labeled LH-Mg-10-16, is unusual: it appears to have come from a bipedal theropod dinosaur—although the features of the six consecutive footprints look strikingly different. It was therefore unclear whether they came from just one animal, and if so, what the special feature was all about. To investigate this question, Buscalioni and her colleagues scanned the footprints to obtain three-dimensional information that allows conclusions to be drawn about foot shapes and movement characteristics.
As the researchers report, their results show that, despite the clear difference between the prints, it is the track of only one animal. The exact species of the theropod dinosaur cannot be determined, but at least its size can be estimated: According to the dimensions of the footprints, it was about two meters at the waist. As the researchers report, the analyzes show that the animal left imprints with its right foot with an average length of 44 centimeters, while the left foot left tracks only about 35 centimeters long.
A toe was twisted
This was due to a deformation of the left foot: while all three toes can be seen pointing forward in the tracks of the right foot, there are only two on the left. Because one of the toes was twisted backwards. As the researchers explain, this was probably the result of an injury or a deformity of the foot. Other results also showed that the dinosaur apparently compensated for its disability when walking. In contrast to comparable traces of other dinosaurs, the footprints of LH-Mg-10-16 are further apart laterally. In addition, analyzes of the imprint depth showed that the animal put more strain on its healthy right foot when walking. The authors point out parallels to today’s birds: Similar toe deformations and compensatory behaviors are known from chickens or ostriches, for example.
Additional findings at the site indicate that the theropod dinosaur with the pathologically deformed foot appeared to be walking through a soft mat of microbes covered by shallow water. He was possibly on his way to a larger waterhole, the trace of which is also evident at the site. Buscalioni and her colleagues conclude that LH-Mg-10-16 is particularly clear evidence of a dinosaur track with pathological features. The study also sheds light on how this dinosaur – and perhaps many others as well – may have found ways to survive despite pathological problems.
Source: PLOS, technical article: PLoS ONE, doi: 10.1371/journal.pone.0264406