ched the area. In 1993, Meyer observed that the sediments above the track level record a marine transgression (sea level rise), and that the tracks were formed at a time when the sea level was relatively low. The eastern part of the tracksite shows mudcracks and, within the tracks, Thalassinoides burrows. At the time of track formation, the eastern part of the tracksite was probably emerged while the western part was submerged. In 1989, Meyer discovered an additional tracksite near Grenchen about 5 km (3.1 mi) from the Lommiswil tracksite that contained similar sauropod tracks. By 1993, a total of six sites were known in the area, which could all be correlated to the same layer within the Reuchenette Formation. Therefore, Meyer suggested that these sites together form a megatracksite (a large-scale but discontinuous tracksite). Description and interpretation

Trackway in the lower-right corner of the surface (sauropod walking from right to left) The Lommiswil tracksite covers a surface of 7,000 m2 (75,000 sq ft) and contains at least 10 identifiable trackways, one of them measuring 60 m (200 ft) in length. The tracks are preserved as moulds (concave impressions) and are 10–25 cm (3.9–9.8 in) deep. The tracks are relatively large; the pes (hind foot) tracks are triangular in shape and up to 80 cm (31 in) in length and 50–60 cm (20–24 in) in width. The manus (fore foot) tracks are often overprinted by the pes, but where they are preserved, they are crescent-shaped and much smaller, measuring about 40 cm (16 in) in both length and width. The stride length (the distance between two tracks made by the same foot) is 220 to 250 cm (87 to 98 in). In general, the tracks lack anatomical details such as claw impressions. Sometimes, the pes tracks are only partly impressed, forming a horseshoe-like shape. The trackways are wide-gauged (the pes tracks do not overlap the trackway midline). The clearest trackway shows a right turn of about 57°. Despite the variability of their shape, Meyer suggested that all tracks were prob