Kyung Soo Kim, Jong Deock Lim, Martin G. Lockley, Lida Xing, Dong Hee Kim, Laura PiÃuela, Anthony Romilio, Jae Sang Yoo, Jin Ho Kim & Jaehong Ahn (2018)
Smallest known raptor tracks suggest microraptorine activity in lakeshore setting
Scientific Reports 8, Article number: 16908Â
Ongoing studies of a multiple track-bearing horizons from massive excavations in the Jinju Formation (Lower Cretaceous) of South Korea have yielded a remarkable diversity of avian, non-avian dinosaur, pterosaur, crocodilian and mammal tracks, many very small and well preserved. Here we report diminutive, didactyl tracks (~1.0âcm long) assigned to a new dromaeosaurid ichnogenus Dromaeosauriformipes, which resembles the larger, but still quite small, ichnogenus Dromaeosauripus, also from the same formation only 30âkm away. These diminutive tracks are consistent with the foot size of smaller dromaeosaurid taxa like Early Cretaceous Microraptor from China, and may represent diminutive species or juveniles of larger species. The association of tracks with lakeshore sediments is consistent with the evidence that Microraptor was a fish eater. Two trackways and isolated tracks indicate variable trackmaker gaits and speeds. If oviparous, as assumed for most non-avian dinosaur neonates, the trackmakers must have hatched from tiny eggs. Previous studies of the Korean Cretaceous indicate the presence of other diminutive (~1.0âcm long) theropod tracks (Minisauripus). Such occurrences strongly suggest that small tracks attributed to juveniles, or very small tetrapod species, are more common than previously supposed especially where suitable preservation conditions prevailed.
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Tom Moklestad, T. Caneer and Spencer G. Lucas (2018)
The "lost tracks" At Dinosaur Ridge, Colorado, from the base of the Cetaceous (late Albian-early Cenomanian) Mowry Shale Member of the Benton Formation, show a swimming(?) ornithopod affected by a current.
in Lucas, S.G. and Sullivan, R.M., eds., 2018. Fossil Record 6. New Mexico Museum of Natural History and Science 79: 503-511
ÂIt is 80-plus years since the discovery of a single dinosaur trackway of 13 tracks was made along West Alameda Parkway on Dinosaur Ridge, and during this time relatively few other sites with dinosaur âswim tracksâ have been documented worldwide. The original tracks and their unmarked location have been lost to weathering and mass wasting that may have been hastened by vandalism, unintentional human activity and/or unauthorized collecting. The original documentation includes an internal report of the Colorado Museum of Natural History (now Denver Museum of Nature and Science). The odometer reading and photographic evidence in the original report are interpreted here to indicate the tracks were on the dip slope in a road cut of the marine Mowry Shale near the depositional contact with the underlying, deltaic South Platte Formation. These tracks are different than hundreds of subsequently uncovered tracks in many trackways nearby on slightly older strata of the South Platte Formation; this trackway represents a different locomotion pattern in a different environment and possibly represents a different kind of dinosaur. Each track was composed of three partial toe prints with some having a partial sole print, suggesting the trackmaker was experiencing buoyancy. Swimming south, generally parallel to the shoreline of the Western Interior Seaway to its right, the trackmaker was tiptoeing, as opposed to foot-paddling, a mode of theropod swimming interpreted from scratch marks in some cases. This movement is interpreted to have been affected by a current.Â