Plesionectes Longicollum: Super Long-Necked Ancient Sea Monster Rediscovered from 47-Year-Old German Fossil!

In a remarkable 2025 scientific resurrection, paleontologists have finally unveiled Plesionectes longicollum—“long-necked near-swimmer”—a basal plesiosauroid with one of the most extreme necks ever recorded in an Early Jurᴀssic marine reptile. The nearly complete skeleton, excavated in 1978 from a quarry in Holzmaden, southwestern Germany, languished unrecognized for 47 years until modern analysis revealed its true idenтιтy.

Published August 4, 2025, in PeerJ, the study by Sven Sachs and colleagues describes the specimen (SMNS 51945) from the world-famous Posidonia Shale (~183 million years ago). Measuring roughly 3–4 meters long, this osteologically immature individual already possessed an extraordinarily elongated neck—far surpᴀssing typical proportions for its group—paired with a compact body and paddle-like limbs optimized for agile underwater maneuvering.

Most astonishingly, the fossil preserves remnants of soft tissue, offering rare glimpses into skin and possible musculature. Its primitive anatomy places Plesionectes among the earliest diverging plesiosauroids, making it the oldest known plesiosaur from the Holzmaden locality and a crucial window into the initial diversification of long-necked marine reptiles.

The discovery rewrites Early Jurᴀssic marine ecosystems. While later plesiosaurs became icons of the Cretaceous, this “super long-necked” pioneer shows that extreme neck elongation evolved remarkably early. Experts call it a “time capsule” that proves the Posidonia Shale still holds surprises after centuries of study.

From a dusty museum drawer, Plesionectes longicollum emerges as a graceful, long-necked hunter that stalked Jurᴀssic seas—proof that even 47-year-old fossils can deliver blockbuster revelations. Paleontology’s plesiosaur story just gained its most neck-stretching chapter yet!