The earliest known reptile

Abstract

AMNIOTES (reptiles, birds and mammals) are distinguished from non-amniote tetrapods (amphibians) by the presence of complex embryonic membranes. One of these, the amnion, gives its name to the group. Very few skeletal characters distinguish amniotes from amphibians1, making it difficult to recognize early amniotes in the fossil record. The earliest amniote fossil identified so far is Hylonomus from the Westphalian (Upper Carboniferous) of Joggins, Nova Scotia2,3, (∼300 Myr). I report here the discovery of a much earlier amniote skeleton from the Brigantian (Lower Carboniferous) of Scotland (∼338 Myr) 4, which thus represents the earliest occurrence of amniotes in the fossil record. The specimen was collected from the East Kirkton Limestone, near Bathgate, West Lothian4–8, and is part of a unique terrestrial fauna that includes eurypterids, myriapods, scorpions and the earliest-known harvestman spider7,9, together with the earliest known temno-spondyls, a group that may include the ancestors of all living amphibians10. It will make an important contribution to our knowledge of early amniote morphology and the interrelationships of tetrapods.