Whatever environmental catastrophe that mauled the archaeocetaceans in our world almost had the same effect on the Late Eocene mosasaurs. Gone were the huge, 15m long tylosaurine sea-serpents and their kin. However, unlike the early whales, the long-bodied mosasaurs had also exploited freshwater habitats, which proved to be their salvation and to this day, a number of small long-bodied mosasaurs surivive in riverine and nearshore habitats.
(Text by Brian Choo )
    Currently the most highly specialised of marine reptiles. Like the Jurassic ichthyosaurs before them and the odontocetaceans of our Earth, the ancestors of these creatures were long-bodied serpentine inshore predators (see above) that developed an increasingly fishlike body for a pelagic existence.

    Saurocetids are fish-like marine squamates ranging from 1.5 to 15 metres in length. They are broadly analogous with our world's odontocetes but have not produced a big-game carnivore in the same league as the orca. The scales have been completely lost and have been replaced with a smooth, leathery hide. The paired nostrils are positioned at the top of the head. Propulsion is by strokes of a fish-like tail bearing 2 vertical flukes. All saurocetes are viviparous.

    The precursors of the saurocetaceans were the huge predatory mosasaurs, marine squamates that evolved in the Cretaceous and were amongst the top ocean predators from the Santonian to the Eocene. The decline of inland seas in the Maastrichtian put pressure on the mosasaurs to more fully exploit the open oceans. One lineage abandoned the serpentine mosasaur-body, becoming more fishlike with a large falcate caudal fin replacing the simple spatulate form.

    While the Late Eocene disaster decimated their long-bodied kin, the early saurocetaceans flourished, developing ever larger and larger forms. Today over 40 species ply the tropical to warm temperate oceans of the world, feeding mainly on cephalopods and small fish. However, they have been unable to venture into the cooler seas, thus are denied access to the rich polar krilling grounds.

(Text by Brian Choo)

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