Smallest Known Raptor Tracks Suggest Mocroraptorine Activity in Lakeshore Setting: Summary

Ongoing studies in a geological formation in South Korea have produced many different tracks, many of which were small and well-preserved. Now there is a report of diminutive two-toed tracks that are around one centimeter long. They are from a new dromaeosaurid(feathered theropod) trace fossil that is similar to a larger trace fossil found thirty kilometers away. This theropod has been named Dromaeosauriformipes Rarus and has been found on a slab with at least eight other tracks that have been categorized as fossils of other species. The track pattern reveals that the trackmaker had varying gaits and speeds. They are, by far, the smallest raptor tracks found so far.

South Korea is well-known for its abundance of Cretaceous track sites in the Gyeongsang Supergroup, which includes many geological formations. It is known for some of the most distinct didactyl dromaeosaurid tracks. There have been recent reports of new mammal and theropod tracks. These tracks are abundant, diverse, and very well-preserved. They often represent species that normally do not show up on less receptive surfaces. These tracks were recovered as part of a government-initiated rescue mission around a Korean National Monument. It was removed by a large rock saw, and contained two trackways and some isolated tracks. The two trackways had seven and three tracks respectively and at least eight isolated tracks. These include two tridactyl ichnogenera(trace fossils, in this case, tracks). They had different morphologies, one is large and robust, and the other had three parallel scratches. All of these tracks were mapped and photographed in situ(on site) and measurements of length, width, steps, and stride were measured using the original specimens, replicas, tracings and calipers(a mathematical tool that measures dimensions).

Gyeongsang Basin in South Korea

The analysis of these tracks has produced the following results. The first trackway, the holotype of this dinosaur, D. Rarus, contains didactyl tracks that are around one centimeter long and 0.4 centimeters wide. Its average step is around 4.5 times its footprint’s length. The average angle of its pace is 188 degrees. The second trackway had similarly sized prints but had a stride that was at least five and a half times longer than the stride length of the prints in the first trackway. Trackway one indicates a slower gait of around 1.6km/h, and Trackway two indicates faster movement of around 37.8 km/h. This is consistent with the maximum speeds of a dinosaur like Velociraptor. The eight isolated prints are similarly sized but do not seem to be associated with the trackways. Collectively, the eighteen tracks from the trackways and isolated prints might represent at least six different trackways that were probably made a similar number of individuals. The similarity in track depth suggests the activity of many individuals over a short period of time instead of repeat crossings of a few individuals over a long period of time.

Prints of different dromaeosaurs

The ichnogenus of  Dromaeosauriformipes Rarus shows a similar morphology to Dromaeosauripus. They both have similar trackway proportions, and that is recognized in the ichnotaxa or name. The other components of its name are derived from the unique features of this species. It is the smallest of all dromaeosaurs discovered its feet are uniquely proportioned. It also lacks any trace of a heel pad, making it hard to compare to some of the other species. However, there are also several similarities. Like D. Jinjuensis and other discovered dromaeosaurs, the toe traces do not join at the heel. This may have a behavioral explanation, like walking on toes instead of heels, or a problem with preserving the tracks.

Artist’s rendition of D. Rarus

In a nutshell, paleontologists may have found a new species of microraptor called Dromaeosauriformipes Rarus, and it is the smallest one ever found so far. It has been found due to the excellent preservation conditions of the Jinju formation in South Korea. Examination of these results reveals that it shared many similarities to other dromaeosaurs. It has the same morphology and a similar gait, but its footprints are uniquely proportioned. The two trackways representing this species came with at least eight isolated tracks that suggest a busy Cretaceous lakeshore. Overall, it is a very exciting scientific discovery that introduces a new member to the unique and interesting family of dromaeosaurs.

Original Article



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