Kouphichnium isp. from the Priabonian–Rupelian of Manipur, India

The basal part of the Laisong Formation, the Barail Group, in the Indo-Myanmar Ranges of northeast India is of great interest for its transitional character with the older Disang Group and its rich assemblages of trace fossils associated with tempestitic deposits. Recent observation of Kouphichnium isp. from the Priabonian–Rupelian basal Laisong Formation at the Gelmon quarry in the Churachandpur district of Manipur led to the first report of this ichnogenus from India. The new finding of Kouphichnium isp. is significant with reference to the biostratigraphy of the Laisong Formation and evaluation of its palaeoecology and palaeoenvironment. The trackways are preserved as straight, or epichnial imprints in 2–7-mm thick shale and laminated siltstone intercalated with thin beds of fine sandstone. They are attributed to the crawling/walking activities of limulids. Association of these trackways in the studied section with shales, laminated siltstone and other sedimentary features such as tidal bundles, hummocky cross-stratification, mud-draped scours and desiccation cracks suggests a tidal flat environment. The presence of Kouphichnium isp. in the studied section indicates the occurrence of horseshoe crabs at the eastern margin of Tethys Sea.