Re-examination of manus-only and manus-dominated sauropod trackways from Morocco

Abstract

Manus-only and manus-dominated trackways of sauropods previously reported from the Iouaridène Basin of Morocco are relocated and re-examined. One trackway, interpreted as a manus-only trackway, was a misinterpretation of a poorly preserved trackway of a large theropod that walked in the opposite direction to that previously inferred. Two previously described manus-dominated trackways could be underprints. One previously described manus-only trackway and a newly discovered manus-only trackway could also be underprints. However, if the true imprinting surface is not identified, an "underprint origin" cannot be accepted as firm evidence that the footprints were imprinted on land, and a swimming or submerged sauropod might have left similar underprints under the contact layer. Kinematic investigations might help to reconstruct the origin of the trackway. The two manus-only trackways from the Iouaridène tracksite apparently show alternating pace lengths which suggests semi-galloping to galloping gait patterns by the trackmakers. Such a galloping gait pattern has never been reported from regular sauropod trackways, and it is unclear as to whether such a trackway pattern represents rapid locomotion. A partly submerged sauropod could perhaps register such galloping gait manus-only trackway patterns as a result of swimming behavior.