Age & Origin: This pair of fossils originates from the Early Cretaceous period (approximately 125 million years ago) and belongs to the Jehol Biota. They were excavated from the renowned Yixian Formation in western Liaoning, China. Scientific Value: As a rare positive-negative counterpart specimen, it not only fully displays the skeletal morphology of *Hyphalosaurus* but also preserves skin textures and soft tissue impressions in the negative counterpart. This provides critical evidence for studying the physiology of this prehistoric aquatic reptile and its paleoecological environment. Collector's Value: 1. Completeness: The skeletal positive and impression negative correspond perfectly, with a preservation rate exceeding 90%. 2. Rarity: Paired *Hyphalosaurus* fossils are highly prized in both academic research and the collector's market.