Investigating the Lower Jurassic marine crocodilian Mystriosaurus
by Sven Sachs, Michela M. Johnson, Mark T. Young & Pascal Abel
Mystriosaurus laurillardi is one of the first marine crocodile fossils ever to be described. While it received its generic name in 1834, the three-dimensionally preserved skull was mentioned in the literature as early as 1776. The fossil that would later be named Mystriosaurus laurillardi was found in a quarry in Altdorf near Nuremberg in Southern Germany by Johann Friedrich Bauder. Bauder was an Altdorf-based merchant and avid naturalist, who was mayor of Altdorf from 1770 to 1776. The fossil was first mentioned in the scientific literature in an article by Johann Ernst Immanuel Walch (1776), who correctly referred to it as the skull of a crocodile. Johann Samuel Schröter (1780) was less convinced about the crocodylian nature of the find, suggesting that it might be the skull of an ant-eating animal.
Some years later the famous poet Johann Wolfgang von Goethe became aware of the Altdorf skull and told his friend, the wealthy Darmstadt-based naturalist Johann Heinrich Merck, about it. Apparently, Goethe had plans to purchase the fossil from Bauder but was beaten to it by Merck. After it came into his possession, Merck published a note about the skull and compared it to the Indian gharial (Merck, 1786). When Merck died in 1791 the fossil was purchased by landgrave Ludwig X in 1792, who added it to the Nature Cabinet at Darmstadt, which formed the foundation of today’s Hessisches Landesmuseum.
Various researchers, including Cuvier (1825), mentioned the skull before Johann Jakob Kaup, who was by then an assistant at the Nature Cabinet in Darmstadt, finally named it Mystriosaurus laurillardi. The specimen is now in collections at the Hessische Landesmuseum in Darmstadt and has the specimen number HLMD V946-948.
Mystriosaurus has been broadly accepted as a valid genus in numerous publications during the 19th and early 20th Centuries. However, in 1961 and 1962 the Tübingen based palaeontologist Frank Westphal published two revisions of Early Jurassic teleosauroids and concluded that Mystriosaurus laurillardi Kaup, 1834 was in fact a subjective junior synonym of Steneosaurus bollensis Jäger, 1828. This conclusion was largely based upon the characteristics named by Kaup in Bronn & Kaup (1842). Still, even Westphal found differences, mentioning that the ventrally protruding tip of the snout found in the Mystriosaurus type specimen is the most extreme case within Steneosaurus. Nevertheless Westphal’s (1961, 1962) conclusion was not questioned in any of the succeeding publications dealing with teleosauroids from the European Jurassic.
In 2018, however, our team reinvestigated the Mystriosaurus type specimen at Darmstadt and come to very different conclusions which were now published the journal Acta Palaeontologica Polonica (Sachs et al., 2019).
During our investigation we referred a second skull to Mystriosaurus. This specimen is another, yet more complete, three-dimensionally preserved skull from Whitby (Yorkshire, Great Britain) that is housed in the collection of the Natural History Museum London with the specimen number NHMUK PV OR 14781. This skull is also an old find; it was purchased by the British Museum in 1840, but it is unclear when and by whom it was discovered. The specimen was long referred to as Teleosaurus brevior, a manuscript name established by Richard Owen (see Blake, 1876, Woodward, 1885). In a study by Blake (1876), it was referred to the genus Steneosaurus and described as Steneosaurus brevior (Blake, 1876).
The German and English skulls share a number of key features, including: a similar length of the rostrum; four teeth in the premaxilla; and an identical, forwardly facing nasal opening, a character that rarely occurs in crocodylomorphs as nearly all fossil and extend forms have the nasal openings at the top of the snout.
In addition to these characters, the specimen also displays: extreme ornamentation on several bones forming the rostrum and skull roof; the presence of numerous large neurovascular foramina on the premaxillae, maxillae and dentaries; and unique antorbital and temporal fenestrae. These features are also diagnostic for Mystriosaurus and distinguish it from all other crocodilians, including Steneosaurus bollensis.
Mystriosaurus laurillardi is a marine crocodylomorph with a mesorostrine skull (having a snout that is between 70 and 55% of the total skull length). It lived during the early Toarcian of the Early Jurassic (approximately 182 million years ago), patrolling the coasts of what is today Germany and England. It can be distinguished from contemporary species such as Steneosaurus bollensis by a number of characters, which includes the forwardly facing nasal openings.
Besides the holotype specimen and the Whitby skull (‘S.’ brevior holotype), we can tentatively attribute another specimen from Holzmaden in Southern Germany to Mystriosaurus. This specimen is a complete skull embedded in a slab of Posidonia Shale that is shown at the Urweltmuseum Hauff in Holzmaden.
Now, after a 250-year mystery, of the validity of Mystriosaurus, a more than 4 m long marine crocodilian, has been resolved.
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