Additional Eocene echinoids from the Sylhet Limestone of Mikir Hills, Assam, Northeast India: Deeper insights into Neo-Tethys palaeobiogeography

We report the presence of two additional echinoid species, Eupatagus faurai ( Lambert, 1927 ) and Echinolampas vilanovae ( Cotteau, 1890 , Échinides éocènes de la province d’Alicante ), from the Sylhet Limestone of Mikir Hills (MH), Assam, North East India. The two species from the middle Eocene of Assam are well recognised under the genera Eupatagus and Echinolampas and are found associated with echinoid fossil spines. These are recorded for the first time from the sediments of the Sylhet Limestone in the MH, Assam. The horizon containing the echinoid faunas described here is recorded in SBZ 16–18, which corresponds to the late Lutetian-Bartonian age of the middle Eocene, as previously reported for the larger benthic foraminifera-bearing bed. The discovery of the present additional echinoids in the Sylhet Limestone of MH provides fascinating evidence for a direct marine connection of the Neo-Tethys Seaway during the Eocene between Northeast India, the northwestern Himalayas, and Western Europe. These fossils support the presence of a warm, shallow marine sea. These findings enhance our understanding of the culmination of the Neo-Tethys Seaway, eventually leading to the formation of the mighty Himalaya.