The Amazing Diversity of Swiss Ichthyosaurs

An ichthyosaur, drawn by me, originally for my book. Based on Ichthyosaurus communis, which was originally thought to have lived in Switzerland, but the specimen in question is now more likely to have been Protoichthyosaurus, which had a noticeably upward-curved lower jaw..

 

Well, it has finally happened. I am now a co-author on a peer-reviewed paleontological paper. I guess you could say I am something of a scientist myself now. The paper in question is Swiss Ichthyosaurs: a review, published in the Swiss Journal of Paleontology, headed by Christian Klug and co-written by six other authors. 

It is open access and can be read Here.

The following images and information are all taken from the paper.

Fig. 1 of the paper, showing the phylogeny of the Ichthyosauria and where Swiss specimens can be placed on the family tree. As you can see, Swiss ichthyosaurs come from almost all major points of the whole clade.

It is pretty much what the title says: A comprehensive view of all notable ichthyosaur material that has been found over the centuries in Switzerland. While most of this is a compilation of already existing literature, we were also able to incorporate brand new data and assessments, including a new genus that was described just this year, and reclassify some questionable taxa. We also included state-of-the-art photos and illustrations of important specimens, so this paper should prove to be a major anchoring point in all future research on the topic. My main contribution to this paper were the making of initial taxa-lists, compiling literature on the topic and researching the history behind some of the specimens.

Geographic distribution of ichthyosaur finds in Switzerland.

The important results of this review are that Switzerland truly was an ichthyosaur country. Multiple species and specimens from all three periods of the Mesozoic are known across the country, from almost all the major families of the clade, including members which sat at important points of evolutionary transition.

Triassic

The greatest diversity of Swiss ichthyosaurs is found in the Middle Triassic, thanks largely to the famous Konservat-Lagerstätten of Monte San Giorgio. Among the taxa we recognize on a named basis are:

• Wimanius odontopalatus
• Mixosaurus cornalianus
• Mixosaurus kuhnschnyderi
• Phalarodon sp.
• Cymbospondylus buchseri
• Besanosaurus leptorhynchus

 

Skeletal of Mixosaurus cornalianus, by Beat Scheffold.

 

These can be grouped into three types: Phalarodon and Mixosaurus are small, streamlined and fast swimmers, already very suggestive of the ichthyosaur types that would become prominent in the Jurassic. Soft-tissue preservation has shown that Mixosaurus already possessed a prominent dorsal fin, something that paleoartist Beat Scheffold told me he has already speculated on before it was even discovered. Besanosaurus and possibly Wimanius were shastasaurids, which were giant ichthyosaurs, albeit with long, slender snouts, possibly adapted towards sucking up cephalopod prey. Cymbospondylus was a large marine predator, likely hunting fish and other reptiles of the time. The specimen from Monte San Giorgio is a 6m long juvenile. Based on what we know from other Cymbospondylus species, adults may have grown up to 17 metres long.

Skeletals of Cymbospondylus (top) and Besanosaurus (bottom), by Beat Scheffold.

Among the specimens that cannot be clearly identified are also an indeterminate mixosaurid and shastasaurid from Laufenburg and Schleitheim respectively and, more importantly, gigantic teeth, ribs and vertebrae from shastasaurids in the Kössen Formation of Kanton Graubünden. These bones have become quite famous, as their size is suggestive of animals that may have grown up to (maybe even exceeding) 20 metres in length, making them possibly some of the largest marine reptiles of all time.

Jurassic

The end of the Triassic saw the extinction of many of the more archaic forms and the proliferation of the remaining clades of the Neoichthyosauria, mainly Parvipelvia. Most of the Swiss specimens come from the Early Jurassic of the northern part of the country. These are:

• Protoichthyosaurus cf. applebyi (formerly identified as an Ichthyosaurus communis)
• Temnodontosaurus sp.
• Eurhinosaurus longirostris
• Hauffiopteryx typicus (formerly identified as a Leptonectes tenuirostris)
• Stenopterygius sp.

Hauffiopteryx material from the Unterer Hauenstein (Solothurn). Note the very large orbit and scleral rings.

Stenopterygius sp. from Teysachaux in Kanton Fribourg.

Again, there is an interesting diversity of forms here. Protoichthyosaurus and Stenopterygius can be imagined as fairly “standard” ichthyosaurs, meaning compact, fast swimmers that likely hunted fish and cephalopods. Temnodontosaurus on the other hand was a very large (up to 15 metres in length) predator of other marine tetrapods, likely filling out the role previously occupied by forms like Cymbopospondylus and later the pliosaurs and mosasaurs. Eurhinosaurus and Hauffiopteryx meanwhile were more specialized beasts. Eurhinosaurus is quite famous for the length of its upper jaw exceeding that of the lower one, readily inviting comparisons to modern swordfish and spearfish (the extinct whale Eurhinodelphis, funnily enough also known from Switzerland, had the same configuration too). It has become doubtful, however, if Eurhinosaurus used its long snout to strike at fish like a marlin. It may have instead used it to probe sediments for burrowing invertebrate prey. Hauffiopteryx was an elongated parvipelvian with ridiculously huge eyes, suggesting perhaps an adaptation towards deep waters or nocturnal activities. The odd thing about this specimen’s taphonomy is that its snout was vertically piercing through three ammonite zones, which would suggest that it somehow died while ramming head-first into the ground, almost like a scene from the Looney Tunes. 

Skeletal of Argovisaurus, by Beat Scheffold. The name refers to Argovia, a latinization of Aargau, while the species name honors Marta Fernandez, known for her work on marine reptiles.

From the Middle Jurassic of Aargau is instead known Argovisaurus martafernandezi, a basal ophthalmosaurian with a 1.3 metre-long skull. It was first described just in March of this year! The only notable specimen from the Late Jurassic of Switzerland is one dubbed the “Bornsaurier”, a platypterygiine from Solothurn whose genus cannot be conclusively determined but was probably something similar to Brachypterygius/Grendelius. The remains of this animal sat in the Naturmusem Olten since 1905, where they had originally been mislabelled as belonging to a marine crocodylian (thalattosuchian). Otherwise known from the Late Jurassic are only a few indeterminate ophthalmosaurians.

Cretaceous

No clearly identifiable taxa of ichthyosaurs are known form the Cretaceous of Switzerland. This may be both due to the depositional environment, local ecology as well as the fact that ichthyosaurs were slowly losing diversity during this time, until eventually going extinct on their own in the Cenomanian.

Vertebra of a Cretaceous ophthalomsaurine from La Presta in Kanton Neuchatel.

However, we do still know that ichthyosaurs lived here during this time thanks to isolated teeth and vertebrae, which come from the Aptian of St. Gallen and Neuchatel. These were historically assigned to Platypterygius, but are not further identifiable than as indeterminate ophthalmosaurians.

Deleted Bits: Mystery Marine Reptiles

One part of my research did not make it into the final publication, but that decision was fairly reasonable, as it did not really relate to ichthyosaurs but rather to other marine reptiles of the time, namely plesiosaurs. From historical records of the 19th century are known three rather mysterious specimens of marine reptiles which have not been examined again since their original description. My original hope in including these in early drafts of the paper was that this could spark future research on these neglected specimens, which may uncover new species and insights into the Cretaceous marine reptile diversity of the country. This is especially important as, compared to ichthyosaurs, the record of plesiosaurians in Switzerland is exceedingly rare. At least mentioning them here in this blogpost may have the same effect and perhaps I will do the necessary research myself somewhen in the future.

Some of the following information was gathered through personal communication with Dr. Adam S. Smith of the Plesiosaur Directory, to whom I am very thankful.

«Polyptychodon sp.» 

• Location: Sainte-Croix (Waadt)

• Time: Early Cretaceous, Hauterivian («Middle Neocomian» in sources)

• Remarks: A single tooth. Polyptychodon is regarded today as a nomen dubium, which is why all that can be said about this specimen is that it likely comes from an unknown pliosaur of the type Pliosaurus or Kronosaurus. That pliosaurs lived in Switzerland is well known, thanks to a humerus from Brugg. The original tooth was housed in the private collection of Gustave Campiche.

• References: Pictet & Campiche 1860, Jaccard 1869.

«Plesiosaurus neocomiensis» 

• Location: Sainte-Croix (Waadt)

•  Time: Early Cretaceous, Hauterivian («Early to Middle Neocomian» in sources)

•  Remarks: Known from two neck vertebrae, three dorsal vertebrae, rib bones, hips and a jaw fragment. Pictet and Campiche classified these in a new species “Plesiosaurus neocomiensis”, but were open to discuss the possibility that the bones from the early and middle Nèocomien may respectively be separate species. Casts of these bones were presented by Campiche in 1866 at the Natural History Museum of London (the lectotype is in the NHM database). In the following years additional British fossils were added to this taxon. Said British specimens were then however reassigned by Richard Lydekker and Per Ove Persson to Cimoliasaurus cantabrigensis, who also rejected Plesiosaurus neocomiensis as a valid taxon. The Swiss specimens were ignored during this reassessment, which leaves them in an interesting taxonomical limbo. Obviously, they cannot be actual Plesiosaurus, as that is a genus from the Early Jurassic that was sometimes used as a wastebasket taxon, but they likely are also not Cimoliasaurus (Smith, pers. comm.). A new examination could therefore be fruitful. Either Campiche’s bones cannot be further identified than Plesiosauria indet. or there may be a chance here to uncover a brand new taxon native to Switzerland. The original bones were in Campiche’s collection and should therefore be traceable to a modern museum collection in Vaud.

• References: Pictet & Campiche 1860, Jaccard 1869, Persson 1963.

«Mosasaurus grosjeanni» 

• Location: Court, Bern

• Time: Late Jurassic, Kimmeridgian

• Remarks: A large tooth found by a pastor named Grosjean at the Mont-Girod. Greppin described it as a contemporary and “imitator” of “Megalosaurus meriani” (today the sauropod Amanzia greppini), by which he seems to have simply meant that it was a large, predatory reptile. Greppin’s original classification as a mosasaur is surely wrong, as those do not appear until the Late Cretaceous. Possible bearers of the tooth may have been large plesiosaurs/pliosaurs, marine crocodylians or perhaps even an ichthyosaur. Teeth of large theropod dinosaurs are also known from the Kimmeridigian of Switzerland.

• References: Greppin 1867, Heer 1883.

References:

• Greppin, Jean-Baptiste: Essai géologique sur le Jura suisse, Délémont 1867.
• Heer, Oswald: Die Urwelt der Schweiz, Zürich 1865 (2. Ausgabe 1883).
• Jaccard, A.: Description du Jura Vaudois et Neuchatelois, in: Matériaux pour la carte géologique de la Suisse, 6, 1869, S. 1 – 340.
• Persson, Per Ove: A Revision of the Classification of the Plesiosauria with a Synopsis of the Stratigraphical and Geographical Distribution of the Group, in: Lunds Universitets Arsskrift, 59, 1963.
• Pictet, François Jules; Campiche, Gustave: Matériaux pour la Paléontologie Suisse, 1860.