在19世纪的过程中，从整个英格兰南部的白垩纪中期沉积物中发现了许多海龟壳遗骸，包括剑桥郡的剑桥格林德的矮小和描述不佳的Trachydermochelysphlyctaenus类型，来自怀特岛上格林桑德的Plastremyslata，和来自多塞特郡梅尔伯里砂岩的“Trachydermochelys”rutteri。对地层成因的回顾表明，所有物质都来自上格林和的Aptian晚期晚期或西MelburyMarlyChalk组的Cenomanian早期，从地质学上讲，一个相对狭窄的时间窗口。如上所述，phlyctaenus是一个有问题的分类单元，因为最合理的类型系列是一个嵌合体，其中包括两个helochelydrid形态型，除了原骨遗骸。通过指定选型可以解决此难题。对所有历史资料的回顾证实了存在三个不同于Helochelydradanubina的英国分类群，一种从德国命名的年代分类单元。至少有四个喜乐类群，因此,发生在西欧早白垩纪向晚白垩纪过渡期间。
A number of helochelydrid turtle shell remains were recovered over the course of the 19th century from mid-Cretaceous sediments throughout Southern England, including the poorly figured and described types of Trachydermochelys phlyctaenus from the Cambridge Greensand of Cambridgeshire, Plastremys lata from the Upper Greensand of the Isle of Wight, and \"Trachydermochelys\" rutteri from the Melbury Sandstone of Dorset. A
review of stratigraphic provenience suggests that all material originates from late Late Aptian portions of the Upper Greensand or early Early Cenomanian portions of the West Melbury Marly Chalk Formation, a relatively narrow time window geologically speaking. As described, Trachydermochelys phlyctaenus is a problematic taxon, because the most plausible type series is a chimera that includes two helochelydrid morphotypes in addition to protostegid remains. This conundrum is resolved through the designation of a lectotype. A
review of all historic material confirms the presence of three English taxa distinct from Helochelydra danubina, a coeval taxon named from Germany. At least four helochelydrid taxa, therefore, occurred in western Europe during the Early to Late Cretaceous transition.
