Rhynchocephalians – These are members of the sister group to squamates (which include lizards, snakes, and worm lizards) and encompass living Tuataras (Sphenodon punctatus), dating back to the late Jurassic period in the Solnhofen Archipelago. They have been recognized for nearly two centuries, with an increasing number of specimens and species, yet their evolutionary development remains poorly understood. A well-documented marine rhynchocephalian genus, Plerosaurus, existed during the late Jurassic period about 150 million years ago, but clear juvenile specimens have yet to be identified among more than 15 known specimens (with several unlisted).
Plerosaurus is a remarkable long-swimming Rhynchocephalian that lived around 150 million years ago in what is now Germany during the late Jurassic period. Image credit: Roberto Ochoa.
“Genuine Plerosaurus is the most common rhynchocephalian found in the Late Jurassic deposits of Canjuers and Cerin, France, as well as in the Solnhofen Archipelago, Germany,” stated Dr. Victor Beccari from the SNSB-Bayerische Staatsammlung für Paläontologie and the Ludwig-Maximilians-Universität, along with his colleagues.
“This genus is characterized by an elongated triangular skull, a reshaped anterior jaw, an absence of a low anterior flange in the front part of the teeth, and reduced forelimbs.”
“Currently, there are two species within this genus: Pleurosaurus goldfussi and Pleurosaurus ginsburgi.”
“The specific distinctions are based on the count of anterior sacral vertebrae (50 and 57, respectively), the ratio of skull to appendix, and more advanced pelvic development in Pleurosaurus goldfussi.”
“Extensive research has been undertaken; however, in the more than 15 published specimens of Plerosaurus, no clear juvenile specimens have been recorded as of yet.”
Plerosaurus cf. P. ginsburgi: (a) Standard light photographs. (b) Photo under UV light. (c) Interpretation diagram of the specimen. Image credit: Beccari et al., doi: 10.1002/ar.25545.
In a recent study, researchers described a juvenile specimen of Plerosaurus.
The fossils were sourced from the Mörnsheim Formation near Müllheim, close to Solnhofen, Bavaria, Germany.
“This fossil is especially intriguing as it distinctly exhibits characteristics typical of young animals,” commented the paleontologist.
“Its teeth are small, show no signs of wear, its bones remain underdeveloped, and the vertebrae are still forming.”
“This small size, along with other features, makes it the first clearly identified juvenile Plerosaurus. These specimens bridge crucial gaps in understanding the growth and development of these extinct reptiles.”
Findings of juvenile Plerosaurus have significant implications for classifying another genus, Acrosaurus.
“Historically, some paleontologists have posited that Acrosaurus might represent a juvenile form of Plerosaurus, but until now, there was no substantial evidence to support this theory,” the researchers noted.
“These new fossils exhibit numerous similarities to previously identified Acrosaurus, suggesting that it is not a separate genus, but rather a hatchling form of Plerosaurus.”
“For years, I have sought to comprehend how these animals grew and developed, but I had never encountered such a young, well-preserved specimen,” remarked Dr. Andrea Villa from the Paleontologia Miquel Crusafont Institute.
The team’s paper was published in the March 2025 issue of Anatomical Records.
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Victor Beccari et al. 2025. Young Pleurosauride (Rhynchocephalia) from the Titonians of the Mörnsheim Formation, Germany. Anatomical Records 308(3):844-867; doi:10.1002/ar.25545
Source: www.sci.news
