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#Archovember Day 11 - Macrospondylus bollensis

The Thalattosuchians were a clade of marine pseudosuchians commonly called “marine crocodiles” or “sea crocodiles”. They were seperated into two groups, the Teleosauroids and the Metriorhynchoids. The metriorhynchoids seemed to be adapted for spending all their time in the water: they had smooth, scale-less skin, tail flukes, and even flippers. Meanwhile, teleosauroids held onto their crocodyliform nature, retaining their osteoderms and probably heading onto land when needed. They inhabited a wide range of habitats: from semi-marine coasts and estuaries, to open-ocean, to freshwater. The Early Jurassic Macrospondylus bollensis was one of these teleosauroids.

Macrospondylus bollensis, long known as “Steneosaurus bollensis” (Steneosaurus being a wastebasket taxon for thalattosuchians) finally had its genus revived in 2020. At 5.5 m (18 ft), it was the largest known Early Jurassic crocodylomorph. Like many other teleosauroids, it had a long, tapering snout, similar to its modern equivalents the gavialids. This snout would have allowed it to quickly maneuver through the water with little resistance, snapping up fish. Oddly enough, like Megalosaurus, Macrospondylus is also represented in the Crystal Palace gardens (though they are simply labeled as Teleosaurus). Modeled after gharials and based on much better preserved fossils than Megalosaurus, the teleosaur statues actually hold up pretty well, other than using a more crocodilian scute pattern.

Macrospondylus bollensis fossils have been found in Germany, the UK, and Luxembourg. It lived in the newly forming Tethys Sea, which was warm and shallow at the time, dotted with small tropical islands where Macrospondylus would have likely emerged to bask in the sun. This area is known for its fossilized crinoids, cephalopods, bivalves, crustaceans, ichthyosaurs, sharks, bony fish, and more, often exquisitely preserved “frozen in time” due to sudden events and nigh perfect fossilization factors. There was an abundance of fish here for Macrospondylus to feast upon, including chimaeras like Acanthorhina, the armoured Dapedium, the long-bodied Euthynotus, pups of the shark-like Hybodus, the herring-like Leptolepis, and many more. It would have lived alongside a variety of icthyosaurs, small plesiosaurs, and other teleosauroids such as Mystriosaurus, Pelagosaurus, and Platysuchus, pterosaurs such as Campylognathoides and Dorygnathus, and come across sauropods such as Ohmdenosaurus wandering the shorelines. But Macrospondylus was not the biggest “fish” in the sea, and if it ventured into the open ocean it could have come across the 8–10 metre (26–33 ft) long icthyosaur Temnodontosaurus, the apex predator of the Early Jurassic Tethys Sea (which is also on display at the Crystal Palace!)

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