PALEONTOLOGY
New insights into the evolution and paleoecology of mosasaurs: most comprehensive study to date
Iconic extinct marine lizards continue to surprise us
image:
Sarabosaurus dahli life reconstruction
view moreCredit: Andrey Atuchin
Mosasaurs are extinct marine lizards, spectacular examples of which were first discovered in 1766 near Maastricht in the Netherlands, fueling the rise of the field of vertebrate palaeontology (the study of fossil remains of animals with backbones). Palaeontologist Michael Polcyn presented the most comprehensive study to date on the early evolution and ecology of these extinct marine reptiles. On 16 December, Polcyn will receive his PhD from Utrecht University for his research into the evolution of the mosasaurs. "Mosasaurs are a textbook example of macroevolution, the emergence of new and distinct groups of animals, above the level of species. Although they have been studied for centuries, new discoveries, novel research approaches, and the application of technology, are still teaching us about their relationships and behaviors, some of which continues to surprise us. For example, through the use of detailed comparative anatomy aided by micro-CT scanning technology, we have gained a much better understanding of what group of lizards mosasaurs likely evolved from.”
Additionally, use of these advanced imaging technologies has allowed him to study the internal structures of the braincases of mosasaurs, and sort out the early evolutionary relationships of some previously problematic fossil taxa. “This study not only addressed the early evolution of the group, but also explored small- and large-scale aspects of their feeding biology,” Polcyn continued. “One spectacular example was a specimen I discovered in Angola, that had the remains of three other mosasaurs in its stomach, one of which was the same taxon as the predator, and documented the first occurrence of cannibalism in mosasaurs."
To the sea
Mosasaurs belong to a group of lizards that took to the sea about 100 million years ago (just like the ancestors of the whales later did). Throughout their 34-million-year history, they evolved into well-adapted marine animals that occupied a wide variety of niches and habitats. Together with a large number of other species, they became extinct 66 million years ago, in the aftermath of the meteorite impact that also wiped out the dinosaurs. "A relatively large number of fossils are known from the second half of the evolutionary history of mosasaurs, allowing a good understanding of the relationships among those species, which have been classified into four major groups," says Polcyn. “Much less is known about their early evolutionary history, and how those major groups are related to one another, their origins, and the origin of mosasaurs as a whole.” To address these gaps, Polcyn has focused on bringing new discoveries to light and restudying historical specimens with advanced imaging technologies, providing significant new anatomical information that is used to infer phylogenetic relationships. Polcyn’s work helps resolve a long-running scientific debate, concluding mosasaurs are not very closely related to snakes, but supporting the idea that their closest relatives are near the monitor lizards.
You are what you eat
Not much was previously known about the feeding habits of mosasaurs either, but a small, yet no less remarkable gap in that knowledge was filled with the discovery, by Polcyn in Angola, of a fossilized mosasaur with three other mosasaurs in its stomach, one being the same species as the predator. "Whether that mosasaur was a scavenger or actively hunted its prey cannot be said with certainty; however, we do have the first documented example of cannibalism in mosasaurs. Additionally, we gained insights into how mosasaurs processed their prey, and relative body size of prey and predator." Also included in his dissertation is a large-scale study of the feeding behaviour of mosasaurs, looking at how mosasaurs divided their foraging areas through the evolutionary history of the group. Polcyn integrated previously published data, along with a new, very large sample that covered a period from 92 to 66 million years ago and included finds from all over the world. The result of that study illuminate patterns of foraging area segregation, and feeding diversity in mosasaurs.
About
Polcyn's entry into palaeontology followed a non-traditional academic path. After serving in the U.S. submarine service and a career in technology and engineering, he devoted himself to research on extinct vertebrates, with a focus on marine reptiles. He is currently a Senior Research Fellow at ISEM at Southern Methodist University in Dallas, Texas.
Method of Research
Meta-analysis
Subject of Research
Animals
A new species of flying reptiles reshuffles the timeline of pterosaur evolution
image:
Reconstruction of Melkamter pateko
view moreCredit: Palaeo-Artist: Pedro Andrade
About 230 million years ago, almost 80 million years before the first bird appeared, their distantly related cousins, the pterosaurs took to the sky, as the first group of active fliers among the vertebrates. Pterosaurs developed active, flapping flight with the help of a wing membrane, which was mainly spanned by the strongly elongated fourth finger of the hand.
In the course of their evolution, the flight capabilities of pterosaurs were improved. Whereas most early forms had still rather short wings and a long tail, the derived subgroup of pterodactyloids had slender, elongate wings and a shortened tail. These animals included basically all Cretaceous pterosaurs and the largest flying animals ever, such as Quetzalcoatlus, which reached wingspans of 12 m or more.The transition from the basal forms to the pterodactyloids happened during the Jurassic, and the first representatives of this group appear in the fossil record in the Late Jurassic, some 160 million years ago. However, our knowledge of pterosaur evolution in the Jurassic is based almost exclusively on the fossil record of the Northern Hemisphere, as very few fossils are known from the southern continents.
Alexandra Fernandes and Prof. Oliver Rauhut of the Bavarian State Collection for Paleontology and Geology (SNSB - Bayerische Staatssammlung für Paläontologie and Geologie) have now introduced a new species of pterosaur from the late Early Jurassic (some 178 million years ago) of Chubut province, Argentina. The new species, named Melkamter pateko, shows several characters of the advanced pterodactyloids – but is around 15 million years older than its next-oldest known relative. Apparently, the origin of this group of pterosaurs reaches much further back in time than currently recognized.
The location of Melkamter's find is also remarkable. The new species comes from an inland setting - apparently this pterosaur lived far from the nearest seacoast. Most known Jurassic pterosaurs come from marine environments and obviously lived close to the sea and probably mainly fed on fish and other marine organisms. In contrast, Melkamter probably mainly fed on insects. This occurrence in inland environments and preference for non-aquatic prey supports recent suggestions that pterodactyloids might have originated in such environments.
„It is possible that an early specialization in highly mobile prey such as flying insects contributed to the evolutionary success of the pterodactyloids. This find highlights not only how little we still know about the pterosaurs of the Southern Hemisphere, but also the potential that the southern continents have to improve our understanding of pterosaur evolution”, explains Alexandra Fernandes reseacher at the Bavarian State Collection for Paleontology and Geology and first author of the study. The study was recently published in the scientific journal Royal Society Open Science.
Location of Melkamter pateko (right) in the Argentine province of Chubut
Credit
Oliver Rauhut
Journal
Royal Society Open Science
Subject of Research
Animals
Article Title
The oldest monofenestratan pterosaur from the Queso Rallado locality (Cañadón Asfalto Formation, Toarcian) of Chubut Province, Patagonia, Argentina
Article Publication Date
11-Dec-2024
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