A dinosaur named Plesionectes Longicollum, a marine reptile that expanded the Jurassic fossil record of the Posidonia Shale in southern Germany, was recently named. Sven Sachs of the Bielefeld Natural History Museum and an international team elevated a decades-old specimen to both a new genus and species through an anatomical study.
“This specimen has been in collections for decades, but previous studies never thoroughly explored its distinctive anatomy,” said Sachs, lead author of the study.
Catalogued as SMNS 51945, the skeleton was excavated in 1978 from shale near Holzmaden in Baden-Württemberg and later stored at the State Museum of Natural History Stuttgart. The largely complete animal measured about 295 centimeters, including a 125-centimeter neck and an 81-centimeter tail, and even preserved soft-tissue impressions. “The skeleton is somewhat compressed, and the head is not quite complete. The living animal would have been about 3.5 meters long,” said Sachs.
Holzmaden had already yielded five plesiosaur species representing all major lineages. Plesionectes longicollum raised the count to six and, at roughly 183 million years old, became the oldest plesiosaur recorded in the formation. “Our detailed investigation uncovered an unusual combination of skeletal features that clearly distinguishes it from all previously known plesiosaurs,” said Sachs.
Earlier researchers had considered the fossil too immature to classify. “In recent years, our knowledge about growth changes in the skeleton of plesiosaurs has increased, so we can better assess today which anatomical features change little and can therefore be used to distinguish from other plesiosaurs,” said Sachs. “I have known the find for a long time. The long neck caught my attention from the beginning,” he added.
Daniel Madzia, a co-author, offered a broader perspective. “This discovery adds another piece to the puzzle of marine ecosystem evolution during a critical time in Earth’s history. The early Toarcian period when this animal lived was marked by environmental changes, including a major oceanic anoxic event that affected marine life worldwide,” said Madzia.
“Plesionectes was, like all plesiosaurs, a very good swimmer that probably primarily fed on fish,” said Sachs, according to the German Press Agency. Limb girdles, vertebrae, and the elongated neck suggested a maneuverable, pursuit-style hunter.
The fossil remains at the Stuttgart museum, viewable to visitors during occasional open days, while researchers continue to examine Posidonia Shale material for other overlooked species.
Written with the help of a news-analysis system.