Oldest southern sauropterygian reveals early marine reptile globalization.

Sauropterygians were the stratigraphically longest-ranging clade of Mesozoic marine reptiles with a global fossil record spanning ∼180 million years 1. However, their early evolution has only been known from what is now the Northern Hemisphere, extending across the northern and trans-equatorial western margins of the Tethys paleo-ocean 1 after the late-Early Triassic (late Olenekian, ∼248.8 million years [Ma] ago 2), and via possible trans-Arctic migration 1 to the Eastern Panthalassa super-ocean prior to the earliest Middle Triassic (Olenekian–earliest Anisian 3,4 , ∼247 Ma). Here, we describe the geologically oldest sea-going reptile from the Southern Hemisphere — a nothosaur (basal sauropterygian 5) from the Middle Triassic (Anisian, after ∼246 Ma6) of New Zealand. Time-scaled ancestral range estimations thus reveal an unexpected circum-Gondwanan high-paleolatitude (>60° S7) dispersal from a northern Tethyan origination center. This coincides with the adaptive diversification of sauropterygians after the end-Permian mass extinction 8 and suggests that rapid globalization accompanied their initial radiation in the earliest Mesozoic. Benjamin Kear and colleagues describe the geologically oldest sea-going reptile from the Southern Hemisphere. This fossil evidences the trans-oceanic dispersal and rapid global radiation of sauropterygians after the end-Permian mass extinction. [ABSTRACT FROM AUTHOR]