Download Gps Trackmaker 64 Bits
Tam Enke
The tracks were only a few meters away from high tide, but sometimes turned that way, vanished, then reappeared further down the beach. This told us the otter was out close to peak tide that morning (between 6-8 a.m.) and was mixing up its exercise regime by occasionally dipping into the surf. Raindrop impressions on top of the tracks confirmed this, as the tracks looked crisp and fresh except for having been pitted by rain. For us, rain started inland and south of there on the island around 10 a.m., but reached the tracks sooner than that. We were there about three hours after then, so the otter was likely long gone, on to another adventure. Nonetheless, we made sure to look up and ahead frequently, just in case the trackmaker decided to come back to the scene of his or her handiwork.
A new Middle Jurassic tracksite dominated by non-avian theropod footprints from the Wangjiashan Formation in Pingchuan District, Baojishan Basin, Gansu Province has yielded a unique trackway with four consecutive manus-pes sets. Only three previous examples, all Early Jurassic in age, of theropod trackways are known with convincing examples of manus tracks and in each case, only two tracks were recorded in association with pes tracks with metatarsal impressions and pelvic traces indicating crouching behavior. Thus, this is the first example of manus tracks registered while a theropod trackmaker was walking. This unique configuration is here designated as Grallator pingchuanensis ichnosp. nov. which shows the trackmaker forelimbs registering in a wide straddle gait, much wider than the pes trackway width. G. pingchuanensis confirms previous reports that theropods could occasionally register tridactyl, ectaxonic manus traces. In the case of the Pingchuan trackway, the short step indicates an animal moving at a slow speed, probably due to a soft substrate.
The Pingchuan theropod tracks can clearly be referred to as grallatorid in the broader sense of the Grallator-Eubrontes plexus (Lockley et al. 2013), and are here assigned to a new ichnospecies (G. pingchuanensis) of the former ichnogenus on the basis of a unique and diagnostic trackway pattern with novel implications for theropod behavior. All four known examples, in order of reporting (Connecticut, Poland, Utah and Gansu), are from the Lower-Middle Jurassic, and all represent Grallator or a closely related ichnogenus. This raises questions as to whether crouching theropod Grallator, or Grallator-like trackmakers engaged in gaits and postures that allowed registration of manus tracks. Since no trackway of a quadrupedal theropod has previously been reported, it is not known if the short step and inward rotation of the pes is a necessary corollary of the wide spacing of the manus traces and their positions relative to the pes. A functional locomotor/biomechanical analysis of potential trackmakers based on the known Lower Jurassic theropod skeletal reconstructions is outside the scope of this paper but could shed light on these questions.
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