Monday, 28 January 2013

Predator or prey....unpicking dinosaur tracks in Spain!

The Las Cerradicas dinosaur track site (dated between Tithonian–Berriasian) near Teruel in Spain is the subject of our latest paper. The Manchester team have been collaborating with a splendid group of scientists in Spain, working on seventeen dinosaur trackways that make this site a dinosaurs trackers heaven. Some of the trackways have been attributed to quadrupedal ornithopods, sauropods and theropods. However, in our paper we discuss the exposure of new track evidence that allows a more detailed interpretation of the controversial tridactyl (three-toed) trackways as well as the modes of locomotion and affinities of the trackmakers.

Trackway LCR8 preserved in level 3 as true tracks. A) Sketch of the trackway LCR8 with preserved manus tracks (redrawn from [22]). B) Picture and outline drawing of the pes-manus set LCR8.7. C) Picture and outline drawing of the pes-manus set LCR8.5. Scale (card) = 8 cm.doi:10.1371/journal.pone.0054177.g005
The team used detailed stratigraphic analysis to reveal four different levels where footprints have been
preserved in different modes. Within the tridactyl trackways, manus (hand) tracks are mainly present in a specific horizon relative to surface tracks. The presence of manus tracks is interpreted as evidence of an ornithopod trackmaker. Cross-sections produced from photogrammetric digital models show different depths of the pes (foot) and manus (hand), suggesting subtle differences in loading between the forelimbs and the hindlimbs.
Track LCR3.3 preserved in layer 3 as true track. A) Picture of the track. Note the levels 1 and 2 in the left part of the picture. Scale (card) = 8 cm. B) Photogrammetric 3D depth analysis model. The white line represents the longitudinal cross section that crosses the track from the ‘‘heel’’ pad through the digit III to the manus print. The contour-line spacing is 3 mm. The depth units are also mm. C) Cross section profile.doi:10.1371/journal.pone.0054177.g009
Several features (digital pads, length/width ratio, claw marks) of some ornithopod pes tracks from Las Cerradicas are reminiscent of theropod pedal morphology. This morphological convergence, combined with the shallow nature of the manus tracks, which reduces preservation potential, opens a new window into the interpretation of these tridactyl tracks. Thus, trackmaker assignations during the Jurassic–Cretaceous interval of purported theropod trackways may potentially represent ornithopod dinosaurs....and not our predatory friends the theropods. Moreover, the Las Cerradicas trackways are further evidence for quadrupedalism among some basal small- to medium-sized ornithopods from this time interval. So tracks can really give insight to how dinosaurs once walked.

To read more on the Las Cerradicas dinosaur track site, click HERE for the paper in the open-access journal PLOS ONE.