Strongylosteus is a large member of the familyChondrosteidae and the largest non-reptilian marine vertebrate in the Posidonia Shale, with a size between 3 metres (9.8 ft) and 4.5 metres (15 ft), and an estimated weight over 800 kg to 1 tonne.
Strongylosteus has been suggested as a junior synonym of Chondrosteus, although there haven't been any new revisions about the status of the genus.[3]