The Helochelydridae are an extinct family of stem-turtles known from fossils found in North America and Europe spanning the Early to Late Cretaceous.[1][2]
The skull, shell and osteoderms of helochelydrids are covered in small, cylindrical protuberances, which are a distinctive characteristic of the group.[3] They are thought to be terrestrial, based on the presence of limb osteoderms and bone histology.[4] Their skull morphology is dissimilar to that of extant tortoises, suggesting an omnivorous habit similar to that of box turtles.[5]
Helochelydridae includes all turtles that are more closely related to Helochelydra than Sichuanchelys, Meiolania, or extant turtles.[6] 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.[7] Some recent studies have recovered them as paracryptodires,[8][9] though other studies have found them to be more basal than paracryptodires.[10][11]
Indeterminate remains most similar to “Helochelydra” anglica and “Helochelydra” bakewelli have been reported from the Berriasian aged Angeac-Charente bonebed of France.[14]
The Helochelydridae are an extinct family of stem-turtles known from fossils found in North America and Europe spanning the Early to Late Cretaceous.
