BBC Earth (Asia) - - Update -

The largest known fos­silised spec­i­men of a pre­his­toric species of aquatic rep­tile called Ichthyosaurus som­er­seten­sis has been found in a mu­seum in Ger­many – and in an un­usual twist, it turns out to be that of an ex­pec­tant mother.

Al­though some­times in­cor­rectly re­ferred to as ‘swim­ming di­nosaurs’, ichthyosaurs were in fact an en­tirely sep­a­rate or­der that evolved from land-based rep­tiles that had re­turned to the sea, much as man­a­tees and whales have evolved from pre­vi­ously land-based mam­mals. They ranged in length from 1m to over 20m.

The I. som­er­seten­sis fos­sil in ques­tion is of a 3-3.5m adult fe­male. The fos­sil, which dates back some 200 mil­lion years to the Early Juras­sic Pe­riod, was orig­i­nally un­earthed in the 1990s, but un­til re­cently lan­guished in the col­lec­tion at the Lower Sax­ony State Mu­seum in Han­nover, Ger­many. That was un­til it was spot­ted by palaeon­tol­o­gist Sven Sachs of the Biele­feld Nat­u­ral His­tory Mu­seum, also in Ger­many.

Sus­pect­ing it could in fact be an

I. som­er­seten­sis spec­i­men, Sachs con­tacted the Univer­sity of Manch­ester’s Dean Lo­max, who along with his col­league Prof Judy Mas­sare had first de­scribed the species. Not only did Sachs’ hunch turn out to be cor­rect, the spec­i­men was also found to con­tain the fos­silised em­bryo of a baby I. som­er­seten­sis, with a pre­served sec­tion of ver­te­brae mea­sur­ing a mere 7cm long.

“It amazes me that spec­i­mens such as this can still be ‘re­dis­cov­ered’ in mu­seum col­lec­tions,” said Lo­max. “This spec­i­men pro­vides new in­sights into the size range of the species, but also records only the third known ex­am­ple of an Ichthyosaurus with an em­bryo. That’s spe­cial.”

Only three ichthyosaur fos­sils con­tain­ing em­by­ros have ever been dis­cov­ered

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