A new genus and species of elasmosaurid — a type of plesiosaur with an extremely long, slender neck — has been identified from the fossilized remains found near the Marambio Base, a permanent, all year-round Argentine Antarctica station on Marambio Island.
Life reconstruction of Marambionectes molinai. Image credit: O’Gorman et al., doi: 10.1080/14772019.2024.2312302.
Elasmosaurs are members of Elasmosauridae, a family of plesiosaurs that flourished during the Cretaceous period, about 145 million to 66 million years ago.
These creatures were fully adapted to an aquatic lifestyle, and had a distinctive body plan comprising a streamlined body, paddle-like limbs and a very long neck with up to 75 individual vertebrae.
The new species, Marambionectes molinai, inhabited the Cretaceous oceans, around 67 million years ago.
Its fossils were recovered from the upper levels of the López de Bertodano Formation in the James Ross archipelago of the Antarctic Peninsula in February 2018.
“The collected remains of Marambionectes molinai include the trunk and part of the tail, the limbs, neck and skull, as well as stomach stones called gastroliths, possibly used to mechanical digestion of food,” said CONICET paleontologist José O’Gorman and his colleagues.
“They were extracted in the first campaign, an intense and exhausting experience that was interrupted by a several-day snowstorm that isolated our research team in a shelter waiting for better weather conditions to allow them to finish the work.”
The material of Marambionectes molinai. Image credit: O’Gorman et al., doi: 10.1080/14772019.2024.2312302.
The phylogenetic analysis recovered Marambionectes molinai within the clade Weddellonectia and as a sister group of the subfamily Aristonectinae.
In this sense, the authors suggest that some of the skeletal characteristics of aristonectines were acquired through a process that began in non-aristonectine elasmosaurids, before the appearance of this clade.
“The general preservation state of the specimen is exceptional, even of cranial material, although it is not complete,” the paleontologists said.
“We were able to confirm not only that it is a new species, but also has particular characteristics that allowed us to locate it as a form of transition between the two groups that inhabited the southern hemisphere, giving light to the evolutionary process and the connection between other genera found in Chile, New Zealand and Western Antarctica.”
The discovery of Marambionectes molinai is reported in a paper in the Journal of Systematic Palaeontology.
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Jose P. O’Gorman et al. 2024. A new elasmosaurid (Plesiosauria: Sauropterygia) from the López de Bertodano Formation: new data on the evolution of the aristonectine morphology. Journal of Systematic Palaeontology 22 (1); doi: 10.1080/14772019.2024.2312302