of partly digested fishes, recognisable by their scales. Subsequent research in 1968 determined that these belonged to the fish genus Pholidophorus, but also that cephalopod beaks and sucker hooks were present. Such hard food particles apparently were retained by the stomach and regularly regurgitated. Carcasses of drowned animals were eaten as well: in 2003 a specimen of Platypterygius longmani was reported having, besides fishes and a turtle, the bones of a land bird in its stomach. Some early ichthyosaurs were durophagous and had flat convex teeth adapted for crushing shellfish. They thus ate benthos from the floor of shallow seas. Other species were perhaps suction feeders, sucking animals into their mouths by quickly opening their relatively short jaws. This was first assumed for Shonisaurus, which giant by this means might have secured a constant food supply for its huge body, and in 2011 for the short-snouted Guanlingsaurus liangae. However, in 2013 a study concluded that the hyoid bone of ichthyosaurs, at the tongue base, was insufficiently ossified to support a suction feeding movement and suggested the alternative that such species were ram feeders, gathering food by constantly swimming forwards with a wide-open mouth. Typical ichthyosaurs had very large eyes, protected within a bony ring, suggesting that they may have hunted at night or at great depths; the only extant animals with similarly large eyes are the giant and colossal squids. Sight thus seems to have been one of the main senses employed while hunting. Hearing might have been poor, given the very robust form of the stapes. Grooves in the palate however, suggest that smell might have been acute or even that electro-sensory organs might have been present. Ichthyosaurs themselves served as food for other animals. During the Triassic their natural predators mainly consisted of sharks and other ichthyosaurs; in the Jurassic these were joined by large Plesiosauria and marine Crocodylomorpha. This is again confirmed by stomach contents: in 2009 e.g., a plesiosaur specimen was reported with an ichthyosaur embryo in its gut. Locomotion In ichthyosaurs, the main propulsion was provided by a lateral movement of the body. Early forms employed an anguilliform or eel-like movement, with undulations of the entire trunk and tail. This is usually considered rather inefficient. Later forms, like the Parvipelvia, has a shorter trunk and tail and probably used a more efficient carangiform or even thunniform movement, in which the last third of the body,