Scientists Uncover More Secrets of Elusive Extinct Marine Reptile

New technology has allowed paleontologists to identify five more fossils of the rare Besanosaurus hidden right in their own museums.

The skull of the type specimen of Besanosaurus leptorhynchus is characterized by extreme longirostry (i.e., thin elongate snout), and equipped with tiny pointed teeth, perfect for catching small fish and extinct cousins of squids with rapid snapping moves of the head and jaws. (Credit: Gabriele Bindellini and Marco Auditore, © Museo di Storia Naturale di Milano)

(CN) — In a new international study, paleontologists have taken another look at their fossils of the ancient reptile, the Besanosaurus, and found exciting new information about the elusive species and how it lived in the Mid-Triassic period.

Details of the study are published Thursday in PeerJ – the Journal of Life and Environmental Sciences, where international paleontologists from Italy, Switzerland, the Netherlands and Poland, present their findings on the marine reptile, changing what was previously thought of the species.

This study came about when the Italian researchers realized they were re-analyzing their Besanosaurus fossil in Milan at the same time that Swiss researchers Andrzej Wolniewicz (IP PAS, Warsaw), Feiko Miedema (SMNS, Stuttgart), and Torsten Scheyer (UZH, Zurich) were studying their Besanosaurus fossil.

“Rather than doing parallel studies, we pooled our data and efforts and pulled on the same string, to enhance our understanding of these fascinating extinct animals”, said Torsten Scheyer.

The Besanosaurus leptorhynchus belongs to a group of extinct aquatic reptiles called the ichthyosaurs, whose name directly translates to ‘fish lizard.’ They first came about in the early Triassic period and persisted until the late Cretaceous, reaching their most diverse era during the Jurassic. Some of these reptiles looked extremely fish-like with smooth bodies and paddle-shaped arms, and they were characterized by their impressive mobility in waters.

It’s quite rare to find fossils of ichthyosaurs from the middle Triassic, the authors noted, which made this study’s discoveries all the more impressive. The Besanosaurus is said to be one of the earliest ichthyosaurs on record. It sported a long eel-like tail instead of the crescent-shaped fish-like tails later ichthyosaurs had, long, slender jaws lined with conical teeth, and eyes likely adapted to see in dark, murky waters. Until now, the longest Besanosaurus was approximately 20 feet long.

It was first discovered 30 years ago near Besano, Italy, hence its name that literally means Besano lizard, during an excavation led by the Natural History Museum of Milan. After re-examining the skull bones from the museum, the authors of the study were able to identify five more of their fossils as belonging to the Besanosaurus. 

Each of these fossils varied in size, which the researchers explained likely signifies the ancient reptiles at different stages in their development. According to their findings, the Besanosaurus is in fact the oldest known ichthyosaur, having emerged in the early Triassic. Additionally, the Besanosaurus has now broken a new record, as researchers now know this reptile could reach up to 26 feet long. This makes it the largest marine predator of its time, and the new best representative of the subgroup, the shastasaurids, which includes some of the largest marine reptiles known.

“The extremely long and slender rostrum suggests that Besanosaurus primarily fed on small and elusive prey, feeding lower in the food web than an apex predator: a novel ecological specialisation never reported before this epoch of the Triassic in a large diapsid reptile. This might have triggered an increase of body size and lowered competition among the diverse ichthyosaurs that co-existed in this part of the Tethys Ocean”, said first author Gabriele Bindellini of the Earth Science Department of Milan University.

The bones all came from museum collections from Milan, Zurich, and Tübingen, and were all excavated from roughly the same location in the Monte San Giorgio region. The area contains a marine basin that is blanketed with bituminous shales, or sedimentary rock that is rich in bitumen, which is most often used as asphalt. 240 million years ago, these shales settled at the bottom of the basin where oxygen is low, creating the ideal environment for fossil preservation. Today, it is recognized as a famous site for yielding excellent fossils of Triassic life, including marine and semiaquatic reptiles, fish and hard-shelled invertebrates.

“Studying these fossils was a real challenge. All Besanosaurus specimens have been extremely compressed by deep time and rock pressure, so we used advanced medical CT scanning, photogrammetry techniques and comparisons with other ichthyosaurs to reveal their hidden anatomy and reconstruct their skulls in 3D, bone by bone”, said senior author Cristiano Dal Sasso of the Natural History Museum of Milan, who was the first to discover and name the Besanosaurus.

As technology advances and more state-of-the-art techniques are developed, people can expect the scientific community to be making more discoveries such as this as they comb through previously explored subjects and find new avenues for innovation.

%d bloggers like this: