Marambionectes
A Late Cretaceous elasmosaurid plesiosaur from Antarctica.
Marambionectes, meaning "Marambio Island swimmer," is a genus of weddellonectian elasmosaurid plesiosaur from the Late Cretaceous López de Bertodano Formation in Antarctica. Its only known species is *M. molinai*, represented by a partial skeleton.
The holotype, IAA-Pv 752, was unearthed in 2018 from unit 9 of the López de Bertodano Formation on Marambio (Seymour) Island in the James Ross Archipelago. This partially articulated, incomplete adult specimen includes a basioccipital, mandible, some teeth, cervical, pectoral, dorsal, and caudal vertebrae, ribs, an ilium, the right humerus and ulna, and a femur. In 2024, O'Gorman and colleagues named the new genus and species, with the generic name referencing Marambio Island and the Greek "nectes" for "swimmer," and the specific name honoring Argentine fossil preparator Omar J. Molina for his Antarctic fieldwork.
Phylogenetic analysis by O'Gorman et al. (2024) placed *Marambionectes* as a derived weddellonectian elasmosaurid, the sister taxon to Aristonectinae. An updated analysis by O'Keefe et al. (2025) produced nearly identical results, recovering it as the outgroup to Aristonectinae. The description sparked controversy in the paleoart community because the researchers used AI-generated images to depict the species.
Quick Facts
- Genus
- Marambionectes
- Species
- molinai
Facts from the source article.
Lore & Background
The Marambionectes holotype specimen, IAA-Pv 752, was discovered in 2018 in sediments of the López de Bertodano Formation (unit 9) near Marambio (Seymour) Island of James Ross Archipelago, Antarctica. The specimen is partially articulated and incomplete, consisting of the basioccipital, mandible, some teeth, cervical, pectoral, dorsal, and caudal vertebrae, ribs, an ilium, the right humerus and ulna, and a femur. The specimen belongs to an adult animal. In 2024, O'Gorman and colleagues described Marambionectes molinai as a new genus and species of elasmosaurid plesiosaur based on these fossil remains.
Reader's Guide
Marambionectes is significant as a derived member of the elasmosaurid clade Weddellonectia, recovered as the sister taxon to the Aristonectinae in phylogenetic analyses by O'Gorman et al. (2024). Nearly identical results were recovered by O'Keefe et al. (2025) in an updated version of this phylogenetic matrix, with Marambionectes as the aristonectine outgroup. Its discovery adds to the understanding of Late Cretaceous plesiosaur diversity in Antarctica. The description of Marambionectes created controversy within the paleoart community when the researchers used AI-generated images to depict the species.
Did You Know?
- The generic name Marambionectes combines a reference to Marambio Island with the Greek word 'nectes', meaning 'swimmer'.
- The specific name molinai honors Argentinian fossil preparator Omar J. Molina and his Antarctic field work.
- The holotype specimen was discovered in 2018 in the López de Bertodano Formation.
More in Fossils of Antarctica 1-24
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