Excavating the “Sea Dragon Dinosaur Dolphin Fossil” – AKA, The Rutland Ichthyosaur

^1*Dean R. Lomax, ²Nigel R. Larkin, ^3,4Mark Evans, ⁵Emma L. Nicholls, ⁶Ian Boomer, ⁷Steven Dey, ⁸Darren Withers, ⁹Emily J. Swaby, ¹⁰Paul de la Salle, ⁸David Savory, and ⁸Mick Beeson

^1*Department of Earth and Environmental Sciences, The University of Manchester; ²University of Reading; ³British Antarctic Survey; ⁴University of Leicester; ⁵Horniman Museum and Gardens, London; ⁶University of Birmingham; ⁷ThinkSee3D; ⁸Peterborough Geological and Palaeontological Group; ⁹Open University; ¹⁰The Etches Collection

In January 2021, a string of semi-articulated ichthyosaur vertebrae was uncovered at the Rutland Water Nature Reserve during some routine maintenance of one of the reserve’s lagoons. The chance find was made by Joe Davis, Conservation Team Leader for the Leicestershire and Rutland Wildlife Trust, which runs the reserve in partnership with Anglian Water who own the land. Following a one-day exploratory dig in February, which revealed what appeared to be a complete skeleton embedded in the Early Jurassic clay (Toarcian Whitby Mudstone Formation), a full excavation was undertaken in Summer 2021. Spread across three weeks, the excavation revealed a 10-metre-long, mostly articulated specimen representing the most complete skeleton of a large prehistoric reptile ever found in Britain. Our initial assessment suggests that it is an example of Temnodontosaurus, possibly T. trigonodon. If correct, this would be the first definite occurrence in the UK. The discovery was formally announced in January 2022, almost a year after the find had been made, and was covered extensively in the media.

 

An Introduction to the Ichthyosaurs of The Kimmeridge Clay

Steve Etches

The Etches Collection Museum of Jurassic Marine Life, Kimmeridge, Dorset, UK

I will be discussing the paucity of articulated ichthyosaurs skeletons found in the Kimmeridge Clay: Three specimens are in The Etches Collection and there are one each in the Natural History Museum London and the Bristol City Museum.  Of the three Specimens at the Etches Collection only one has been studied and described. However, the evidence in these specimens gives a good indication of their particular lifestyle that has been ignored up to now. Also, although individual ichthyosaur bones are the most common finds in the Kimmeridge Clay, why do we not find complete articulated specimens? The answer is the rise of the mega predators i.e. Pliosaurs and Metriorhynchid crocodiles. The evidence shows that ichthyosaurs amongst other reptiles are commonly a major food source for these predators. I will illustrate this by showing many predated and scavenged ichthyosaur elements.

Exploration and Redetermination of Fossil Marine Reptile Material at the Horniman Museum – The Lost, Misidentified and Unknown

Emma Nicholls

The Horniman Museum and Gardens, London, UK

The Horniman Museum has a fossil collection of around 200,000 specimens. Approximately 175,000 of them were collected by Walter Bennett (1892-1971), a mining engineer and amateur palaeontologist. Around a quarter of the Bennett Collection is vertebrate material, predominantly ichthyosaurs, plesiosaurs, crocodilians, and fish. The Collection was transferred to the Horniman Museum in 1989 and bulk-accessioned under one number, with less than 2% added to the collections management database over the last 30 years.

Recent research has uncovered scientifically significant information about this hitherto poorly known material. Many of the marine reptile specimens were collected at quarries that are listed as Sites of Special Scientific Interest or Geological Conservation Review sites, some of which are no longer accessible for further collecting or study.

Investigations have also recovered a figured, yet ‘lost’, partial ophthalmosaur paddle from the Middle Jurassic, and redetermined plesiosaur and metriorhynchid material, previously misidentified as Dacentrurus and plesiosaur, respectively. This paper will provide an overview of the marine reptile material at the Horniman Museum, with particular focus on the Bennett Collection, and explore new insights into its significance.

A new cryptoclidid from the Oxford Clay Formation of Cambridgeshire, UK

¹Hilary Ketchum, ^2*Roger Benson, ^3*Mark Graham, ^4*Carl Harrington, ^4*Heather Middleton, ^4*Cliff Nicklin, ^4*Shona Tranter, and ^4*Mark Wildman

¹Oxford University Museum of Natural History; ²Department of Earth Sciences, University of Oxford; ³Natural History Museum, London; ⁴Oxford Clay Working Group

*Authors in alphabetical order

Cryptoclididae is a species-rich clade of plesiosaurians that spanned from the Middle Jurassic to the Early Cretaceous. Here we present a substantially complete skeleton of a long-necked cryptoclidid from Whittlesey, Cambridgeshire, discovered by the Oxford Clay Working Group in 2014. The specimen was extracted and donated to the Oxford University Museum of Natural History in 2015, following 450 hours of preparation of the postcranial skeleton. After it reached the museum, the field jacket containing the skull was CT scanned to facilitate its removal from the matrix. Around 500 hours of preparation revealed that the skull is exceptionally well preserved. Other than Cryptoclidus, the skulls of cryptoclidids are generally poorly known due to their fragile construction. This new specimen therefore provides much additional anatomical information for the clade. The specimen has several autapomorphies, indicating that it is a new species, probably most closely related to Muraenosaurus.

Functional reconstruction of the ichthyosaurian jaw using 3D computed tomography

^1,2Sarah Jamison-Todd, ¹Benjamin Moon, ¹Andre Rowe, ³Matt Williams, ¹Michael Benton

¹Palaeobiology Research Group, University of Bristol; ²Earth Sciences, University College London; ³Bath Royal Literary and Scientific Institute

Early Jurassic ichthyosaurs are known for their excellent preservation and substantial diversity, being an important component of the marine ecosystems at this time. The ecology and functional palaeobiology of these marine reptiles have been considered qualitatively from time to time, but they offer great potential for quantitative studies. Here we present a quantitative study of ichthyosaur jaw mechanics using material from the exceptionally preserved Toarcian Strawberry Bank locality of Ilminster, UK. Using 3D CT scanned skulls referred to Hauffiopteryx typicus (BRLSI M1399) and Stenopterygius triscissus (BRLSI M1409), we reconstruct the posterior cranial musculature involved in jaw adduction, applying finite element modelling to the ichthyosaur jaw for the first time. Our results show a combined muscle force of 291 N that translates to a posterior bite force of 181 N (using lever mechanics) in H. typicus and total force of 158 N with posterior bite force of 68 N in S. triscissus. Most force is derived from the M. depressor mandibulae in both taxa, but H. typicus has relatively higher stresses in the antorbital region than S. triscissus reflecting the gracility of the nasals. Differences in reconstructed bite force are explained by the different sizes of these specimens, however, S. triscissus has a relatively weaker bite force than H. typicus for its size despite the more robust cranial architecture and larger teeth. These data support previous hypotheses of different feeding strategies between the two taxa and likely different prey preferences with H. typicus likely hunting softer prey than S. triscissus.

New insight into prenatal development in ichthyosaurs

^1,2Feiko Miedema

¹Staatliches Museum für Naturkunde Stuttgart; ²Hohenheim University

The Ichthyosauria is a clade of diapsids secondarily adapted to marine life. All members of the group were viviparous. We know this because of the numerous fossil pregnant females found in many species throughout phylogeny. There is a large sample size in specimens of several taxa, such as Stenopterygius and Mixosaurus, because they are regularly found in Lagerstätten deposits in Germany and the Alpine region. This lends us the opportunity to study their osteological development in great detail. In Stenopterygius specifically we were able to establish for the first time four separate prenatal stages on the basis of the relative onset and timing of ossification of the cranial elements. Dermatocranial elements ossified earlier than chondro- and splanchnocranial elements. In the dermotacranial elements specifically the circumorbital elements are more advanced throughout development whereas the skull roof lags most other elements continuously. In Mixosaurus the same overall pattern of dermatocranial elements ossifying earlier than chondro – and splanchnocranial elements is also present. Moreover, the development of the braincase elements of Mixosaurus compared to Stenopterygius is interesting as in Mixosaurus early developmental remnants of possible basal tubera are found. These are entirely lost throughout the development of Stenopterygius. In both late-stage embryonic material of Stenopterygius and Mixosaurus the skull roof elements have established a tight connection, however the antimeric midline connections are not established. We therefore hypothesize that this non-closure functions as a fontanelle convergent to other animals. Lastly, we are developing a proxy for staging ichthyosaur embryos in other taxa based on relative notochord pit size.