The foetus of an Ichthyosaurus has been discovered still inside the womb 200 million years after its mother died during pregnancy.
The 3.5 metre (11ft) pregnant ichthyosaur lived at the time of the earliest dinosaurs during the early Jurassic period.
Scientists said the incomplete embryo was less than seven centimetres long and consisted of preserved vertebrae, a forefin, ribs and a few other bones.
Researchers examining a fossil (pictured) left unidentified for more than 20 years have found that it belonged to the species Ichthyosaurus somersetensis, making it the biggest Ichthyosaur fossil ever found at 3.5 metres (11.5 ft) long
There was evidence the foetus was still developing in the womb when it died.
The find adds to evidence that ichthyosaurs, some of which grew to more than 20 metres (65 ft), gave birth to live young unlike egg-laying dinosaurs.
Dean Lomax, from the University of Manchester, who co-led the UK-German team, said: ‘This specimen provides new insights into the size range of the species, but also records only the third example of an ichthyosaurus known with an embryo – that’s special.’
The creature, named ichthyosaurus somersetensis, was discovered on the Somerset coast during the 1990s but ended up in the collections of the Lower Saxony State Museum in Hanover, Germany.
The new study also showed that a tail from another ichthyosaur had been added to the skeleton to make it appear more complete and visually appealing for display.
Palaeontologist Dr Sven Sachs, from the Bielefeld Natural History Museum in Germany, who also took part in the research, said: ‘It is often important to examine fossils with a very critical eye.
‘Sometimes, as in this instance, specimens aren’t exactly what they appear to be.
‘However, it was not “put together” to represent a fake, but simply for a better display specimen.
They also found incomplete embryo remains within the skeleton, including a 7 cm (2.8 in) string of backbone, a forefin, ribs and a few other unidentified bones. Pictured is an arti’st reconstruction of the pregnant marine reptile
‘Specimens like this provide palaeontologists with important information about when these animals lived.
‘Many examples of ichthyosaurus are from historical collections and most do not have good geographical or geological records, but this specimen has it all.’
The specimen was the largest of the ichthyosaurus family of ichthyosaurs on record, said the scientists writing in the journal Acta Palaeontologica Polonica.
Ichthyosaurs were a highly successful group of sea-going reptiles that became extinct about 90 million years ago.
Often misidentified as swimming dinosaurs, these reptiles appeared before the first dinosaurs had evolved.
The creature, named ichthyosaurus somersetensis, was discovered on the Somerset coast during the 1990s
They evolved from an as-yet unidentified land reptile that moved back into the water.
The huge animals, which remained at the top of the food chain for millions of years, developed a streamlined, fish-like form built for speed.
Scientists calculate that one species had a cruising speed of 22 mph (36 kmh).
The largest species of ichthyosaur grew to over 20 metres (65 ft) in length.