Didactyl, tridactyl and tetradactyl theropod trackways from the Lower Jurassic of Morocco: evidence of limping, labouring and other irregular gaits

Abstract

Two theropod trackways with alternating long–short pace lengths and a didactyl theropod trackway were discovered from Ait Blal tracksite situated in central High Atlas Mountains, Morocco. They are described here together with other tridactyl and tetradactyl footprints. The track-bearing bed belongs to the Lower Jurassic (Pliensbachian) Aganane Formation. One of the theropod trackways with alternating pace lengths indicates locomotion by a limping dinosaur. In this trackway, the pathological irregularities in the morphology of right footprints suggest that the trackmaker had injured its right foot. Another trackway with alternating pace lengths suggests the accidental problem while walking of theropod trackmaker. The morphology of the didactyl theropod trackway may be attributable to a dromaeosaurid or dromaeosaurid-like trackmaker whose body fossil remains have not been reported from the Jurassic. If the trackmaker of the didactyl prints was a dromaeosaurid, the discovery supports the idea that dromaeosaurid dinosaurs had early origins and also are ancestral to birds.