Thalattosuchians are ancient relatives of the ancestors of modern-day crocodiles, a biological aunt if you will, and part of the head, backbone, and limbs of Turnersuchus hingleyae have been found on what paleontologists call the Jurassic Coast, in Dorset of the United Kingdom.

The name derives from Paul Turner and Lizzie Hingley, who discovered the fossil in 2017. The ending “suchus,” is the Latinized form of “soukhos,” Greek for crocodile. 

Turnersuchus is the oldest complete enough thalattosuchian of the Early Jurassic, Pliensbachian period, around 185 million years ago to-date. The discovery of this new predator helps fill a gap in the fossil record and suggests that thalattosuchians, with other crocodyliforms, originated around the end of the Triassic period – around 15 million years further back in time than when Turnersuchus lived. That would mean they survived the end-Triassic mass extinction.

Turnersuchus hingleyae by Júlia d'Oliveira.

No digs have found thalattosuchians in Triassic rocks yet, leaving a gap during which a group must have existed, but hasn't been found in fossil evidence - a ghost lineage. Until the discovery of Turnersuchus, this ghost lineage extended from the end of the Triassic until the Toarcian, in the Jurassic.

Thalattosuchians are referred to colloquially as ‘marine crocodiles’ or ‘sea crocodiles’, despite the fact they are not members of Crocodylia, but are more distantly related. Some thalattosuchians became very well adapted to life in the oceans, with short limbs modified into flippers, a shark-like tail fin, salt glands, and potentially the ability to give live birth (rather than lay eggs). In Turnersuchus, some recognized thalattosuchian features had yet to fully evolve.

It lived in the Jurassic Ocean and preyed on marine wildlife. And, due to its relatively long, slender snout, would have looked similar in appearance to the currently living gharial crocodiles, which are found in all the major river systems of the northern Indian subcontinent. had particularly large supratemporal fenestrae – a region of the skull housing jaw muscles. This suggests that Turnersuchus and other thalattosuchians possessed enlarged jaw muscles that likely enabled fast bites; most of their likely prey were fast-moving fish or cephalopods.

It’s possible too, just as in modern-day crocodiles, that the supratemporal region of Turnersuchus had a thermoregulatory function – to help buffer brain temperature.