Crocodylia are one of the distinctive groups that survived the K/Pg mass extinction event. New material from Upper Cretaceous–lower Palaeogene deposits is therefore important to understanding shifts in crocodylian distribution and ecology. This paper describes a fragmentary mandible of a marine crocodylian, from the lower Maastrichtian (Upper Cretaceous) of Møns Klint (Denmark). The specimen is referred to cf. Thoracosaurus (Gavialoidea). Although the material was collected in 1968, it has not yet been formally described. However, the specimen warrants further attention, given its palaeoecological and palaeobiogeographical significance. For instance, the Møns Klint “Thoracosaurus” is an indication of increased competition between large piscivores, and of added predation pressure on fish and cephalopod communities. This gavialoid therefore provides new insight into predator-prey interactions in the Danish Chalk palaeoenvironment. Regarding crocodylian distribution, the Møns Klint specimen represents the oldest European gavialoid record, with all other material deriving from uppermost Maastrichtian and Danian deposits. This indicates that Gavialoidea were present in the European “Chalk Sea” throughout the Maastrichtian, rather than being latest Maastrichtian arrivals. Furthermore, the Møns Klint “Thoracosaurus” represents one of few lower Maastrichtian gavialoids worldwide, the other two being from Mississippi and New Jersey (USA). The specimen thus extends the palaeogeographical range of lower Maastrichtian gavialoids across the proto-Atlantic. This reveals transatlantic distribution of Gavialoidea dating back to the earliest Maastrichtian, providing further evidence for distributional communication between marine vertebrate faunas of North America and Europe. These factors make the Møns Klint “Thoracosaurus” particularly valuable to understanding the distribution of K/Pg Crocodylia.

鳄鱼是在 K/Pg 大灭绝事件中幸存下来的独特群体之一。因此，来自上白垩统 - 下古近纪沉积物的新材料对于了解鳄鱼分布和生态学的变化很重要。本文描述了来自 Møns Klint（丹麦）的下马斯特里赫阶（上白垩统）的海洋鳄鱼的碎片下颌骨。标本参考cf。胸龙（ Gaviloidea）。尽管该材料是在 1968 年收集的，但尚未正式描述。然而，鉴于其古生态学和古生物地理意义，该标本值得进一步关注。例如，Møns Klint “ Thoracosaurus ””表明大型食鱼动物之间的竞争加剧，以及对鱼类和头足类群落的捕食压力增加。因此，这种gavialoid 为丹麦白垩古环境中的捕食者-猎物相互作用提供了新的见解。关于鳄鱼的分布，Møns Klint 标本代表了欧洲最古老的 gaviloid 记录，所有其他材料均来自最上层的马斯特里赫特和达尼亚沉积物。这表明 Gavialoidea 存在于整个马斯特里赫特人的欧洲“白垩海”中，而不是最新的马斯特里赫特人到达。此外，Møns Klint “胸龙” 代表了世界上为数不多的马斯特里赫特低等鱼种之一，另外两种来自密西西比州和新泽西州（美国）。因此，该标本将马斯特里赫特河下游的古地理范围扩展到了整个原始大西洋。这揭示了可追溯到最早的马斯特里赫特人的 Gavialoidea 的跨大西洋分布，为北美和欧洲海洋脊椎动物群之间的分布交流提供了进一步的证据。这些因素使得 Møns Klint “胸龙”对于了解 K/Pg 鳄鱼的分布特别有价值。