The Helochelydridae are an extinct family of stem-turtles known from fossils found in North America and Europe spanning the Early to Late
Cretaceous.
Description
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 and bone histology. Their skull morphology is dissimilar to that of extant tortoises, suggesting an omnivorous habit similar to that of box turtles.
Taxonomy
Helochelydridae includes all turtles that closely related to '' Helochelydra'' than '' Sichuanchelys'', '' Meiolania'', or extant turtles.basal
Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''.
Science
* Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure
* Basal (medicine), a minimal level that is nec ...
than paracryptodires.
Genera
* '' Aragochersis''Escucha Formation
The Escucha Formation is a geological formation in La Rioja and Teruel provinces of northeastern Spain whose strata date back to the late Aptian to middle Albian stages of the Early Cretaceous. Dinosaur remains are among the fossils that have bee ...
, Spain, Early Cretaceous ( Albian)
* '' Helochelydra'' Wessex Formation, England, Early Cretaceous ( Barremian)
*''“Helochelydra” anglica'' (Lydekker, 1889) Purbeck Group, United Kingdom, ( Berriasian)
*''“Helochelydra” bakewelli'' Mantell, 1833 Tunbridge Wells Sandstone, England, ( Valanginian)
* ''Helochelys
''Helochelys'' is an extinct
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, alt ...
'' Grünsandstein Formation
The Grünsandstein Formation is a geologic formation in Germany. It preserves fossils dating back to the Cretaceous period.
See also
* List of fossiliferous stratigraphic units in Germany
See also
* Lists of fossiliferous stratigraphic un ...
, Germany, Late Cretaceous (Cenomanian
The Cenomanian is, in the ICS' geological timescale, the oldest or earliest age of the Late Cretaceous Epoch or the lowest stage of the Upper Cretaceous Series. An age is a unit of geochronology; it is a unit of time; the stage is a unit in the s ...
), Cambridge Greensand, England, Albian-Cenomanian, France, Spain, Cenomanian
* ''Trachydermochelys phlyctaenus'' Seeley 1869 (revised Joyce, 2022Naomichelys
''Naomichelys'' is an extinct genus of helochelydrid stem turtle known from the Cretaceous (Aptian-Campanian) of North America. It is the only member of the family known to be native to North America.
Distribution
''Naomichelys'' is known nume ...
'' Cretaceous (Aptian-Campanian) North America[
*'' Plastremys'' Upper Greensand Formation, Cambridge Greensand, England, Albian-Cenomanian, Spain, Albian France, Cenomanian
* '' Solemys'' France, Spain, Late Cretaceous ( Campanian- Maastrichtian)
* ''Trachyaspis turbulensis'' Bergounioux 1957 Gargallo, Spain, Early Cretaceous (Aptian-Albian) (possibly synonymous with ''Plastremys rutteri'')][Ronan Allain, Romain Vullo, Lee Rozada, Jérémy Anquetin, Renaud Bourgeais, et al.]
Vertebrate paleobiodiversity of the Early Cretaceous (Berriasian) Angeac-Charente Lagerstätte (southwestern France): implications for continental faunal turnover at the J/K boundary
Geodiversitas, Museum National d’Histoire Naturelle Paris, In press. ffhal-03264773f
References
{{Taxonbar, from=Q3489339
Testudinata
Prehistoric reptile families