Helochelydridae

The Helochelydridae are an extinct family of stem-turtles known from fossils found in North America and Europe spanning the Early to Late Cretaceous.

The skull, shell and osteoderms of helochelydrids are covered in small, cylindrical protuberances, which are a distinctive characteristic of the group. They are thought to be terrestrial, based on the presence of limb osteoderms (granicones) and bone histology. Their skull morphology is dissimilar to that of extant tortoises, suggesting an omnivorous habit similar to that of box turtles.

Helochelydridae includes all turtles that are more closely related to Helochelydra than Sichuanchelys, Meiolania, or extant turtles. Although referred to as Solemydidae in recent literature on extinct turtles, Helochelydridae has priority over Solemydidae. They are placed as part of the clade Perichelydia. Some recent studies have recovered them as paracryptodires, though other studies have found them to be more basal than paracryptodires.

Position of helochelydrids according to Tong et. al. 2023:

Indeterminate remains most similar to "Helochelydra" anglica and "Helochelydra" bakewelli have been reported from the Berriasian aged Angeac-Charente bonebed of France.