Amniotes first invaded saline lagoons and coastal seaways towards the end of the Palaeozoic (Early Permian, ~ 280 Ma: Piñeiro et al. 2012), but by the dawn of the Mesozoic (Early–Middle Triassic, ~ 250–235 Ma: Rieppel, 2002; McGowan & Motani, 2003) they had achieved a diversity of specialized body-forms requisite for an obligate oceanic lifestyle. Such an explosive ecomorphological radiation paved the way for amniote dominance of large-bodied aquatic carnivore/omnivore niches over the next 185 Ma, with some lineages (e.g. dyrosaurid crocodylomorphs and bothremydid turtles: Gaffney, Tong & Meylan, 2006; Barbosa, Kellner & Sales Viana, 2008) even persisting on into the Palaeogene (until ~ 50 Ma), and diversifying (i.e. chelonioid sea turtles: Hirayama, 1997) alongside emergent marine mammals through the Neogene (from ~ 23 Ma) and up until today.

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