Helochelydridae

The skull, shell and osteoderms of helochelydrids are covered in small, cylindrical protuberances, which are a distinctive characteristic of the group.{{Cite journal|last1=Gentry|first1=Andrew D.|last2=Ebersole|first2=Jun A.|date=2021-08-10|title=The first occurrence of the stem turtle Naomichelys from the Late Cretaceous of eastern North America|url=https://www.tandfonline.com/doi/full/10.1080/08912963.2021.1962855|journal=Historical Biology|volume=34 |issue=7 |language=en|pages=1129–1136|doi=10.1080/08912963.2021.1962855|s2cid=238677455 |issn=0891-2963|url-access=subscription}} They are thought to be terrestrial, based on the presence of limb osteoderms (granicones) and bone histology.{{Cite journal|last1=Scheyer|first1=T. M.|last2=Pérez-García|first2=A.|last3=Murelaga|first3=X.|date=March 2015|title=Shell bone histology of solemydid turtles (stem Testudines): palaeoecological implications|url=http://link.springer.com/10.1007/s13127-014-0188-0|journal=Organisms Diversity & Evolution|language=en|volume=15|issue=1|pages=199–212|doi=10.1007/s13127-014-0188-0|bibcode=2015ODivE..15..199S |s2cid=18628827|issn=1439-6092}} Their skull morphology is dissimilar to that of extant tortoises, suggesting an omnivorous habit similar to that of box turtles.WALTER, J.G., CHAPMAN S.D., MOODY R.T.J., and WALKER, C.A. 2011. [https://www.researchgate.net/publication/267202874 The skull of the solemydid turtle Helochelydra nopcsai from the Early Cretaceous of the Isle of Wight (UK) and a review of Solemydidae] IN BARRETT, P.M. and MILNER, A.R. (eds.) Studies on Fossil Tetrapods. Speicial Papers in Palaeontology, 86, 75-97.

Helochelydridae includes all turtles that are more closely related to Helochelydra than Sichuanchelys, Meiolania, or extant turtles.{{cite book |author=Hans-Dieter Sues |url=https://books.google.com/books?id=qGycDwAAQBAJ&dq=Meiolania+length&pg=PA53 |title=The Rise of Reptiles. 320 Million Years of Evolution |date=August 6, 2019 |publisher=Johns Hopkins University Press |isbn=9781421428680 |page=53}} 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.{{Cite journal |last1=Joyce |first1=Walter G. |date=April 2017 |title=A review of the fossil record of basal Mesozoic turtles |url=http://doc.rero.ch/record/288659/files/joy_rfm.pdf |journal=Bulletin of the Peabody Museum of Natural History |volume=58 |issue=1 |pages=65–113 |doi=10.3374/014.058.0105 |accessdate=July 9, 2017 |s2cid=54982901}} Some recent studies have recovered them as paracryptodires,{{Cite journal |last1=Rollot |first1=Yann |last2=Evers |first2=Serjoscha W. |last3=Joyce |first3=Walter G. |date=December 2021 |title=A redescription of the Late Jurassic (Tithonian) turtle Uluops uluops and a new phylogenetic hypothesis of Paracryptodira |journal=Swiss Journal of Palaeontology |language=en |volume=140 |issue=1 |pages=23 |doi=10.1186/s13358-021-00234-y |pmid=34721284 |pmc=8550081 |issn=1664-2376 |doi-access=free |bibcode=2021SwJP..140...23R }}{{Cite journal |last1=Rollot |first1=Yann |last2=Evers |first2=Serjoscha W. |last3=Pierce |first3=Stephanie E. |last4=Joyce |first4=Walter G. |date=2022-11-02 |title=Cranial osteology, taxonomic reassessment, and phylogenetic relationships of the Early Cretaceous (Aptian-Albian) turtle Trinitichelys hiatti (Paracryptodira) |journal=PeerJ |language=en |volume=10 |article-number=e14138 |doi=10.7717/peerj.14138 |pmid=36345484 |pmc=9636874 |issn=2167-8359 |doi-access=free }} though other studies have found them to be more basal than paracryptodires.{{Cite journal |last1=Tong |first1=Haiyan |last2=Tortosa |first2=Thierry |last3=Buffetaut |first3=Eric |last4=Dutour |first4=Yves |last5=Turini |first5=Eric |last6=Claude |first6=Julien |date=January 2022 |title=A compsemydid turtle from the Upper Cretaceous of Var, southern France |url=https://linkinghub.elsevier.com/retrieve/pii/S0753396922000027 |journal=Annales de Paléontologie |language=en |volume=108 |issue=1 |pages=102536 |doi=10.1016/j.annpal.2022.102536|bibcode=2022AnPal.10802536T |s2cid=248792130 |url-access=subscription }}{{Cite journal |last1=Tong |first1=Haiyan |last2=Buffetaut |first2=Eric |last3=Méchin |first3=Patrick |last4=Méchin-Salessy |first4=Annie |last5=Claude |first5=Julien |date=2023-01-03 |title=A Solemys Skull from the Late Cretaceous of Southern France |journal=Diversity |language=en |volume=15 |issue=1 |pages=58 |doi=10.3390/d15010058 |issn=1424-2818|doi-access= free}}

Position of helochelydrids according to Tong et. al. 2023:{{Cite journal |last1=Tong |first1=Haiyan |last2=Buffetaut |first2=Eric |last3=Méchin |first3=Patrick |last4=Méchin-Salessy |first4=Annie |last5=Claude |first5=Julien |date=2023-01-03 |title=A Solemys Skull from the Late Cretaceous of Southern France |journal=Diversity |language=en |volume=15 |issue=1 |pages=58 |doi=10.3390/d15010058 |issn=1424-2818 |doi-access=free}}{{clade|{{clade

|label1=Mesochelydia

|1={{clade

|1=†Kayentachelys

|2={{clade

|1=†Condrochelys

|2={{clade

|1={{clade sequential

|1=†Heckerochelys

|2=†Eilanchelys

|3=†Indochelys

}}

|label2=Perichelydia

|2={{clade sequential

|1=†Spoochelys

|2=†Meiolaniformes

|3=†Sichuanchelyidae

|4={{clade

|label1=†Helochelydridae

|1={{clade

|1=†Aragochersis

|2={{clade

|label1=

|1=†Solemys

|2={{clade

|1=†Helochelydra

|2=†Naomichelys

}}

}}

}}

|label2=Testudines (crown group)

|2={{clade

|1={{clade

|label1=†Paracryptodira

|1={{clade

|1=†Haemys

|2=†Baenidae

|3={{clade

|1=†Neurankylus

|2={{clade

|1={{clade

|1=†Dinochelys

|2=†Glyptops

}}

|2={{clade

|1={{clade

|1=†Arundelemys

|2=†Trinitichelys

}}

|2={{clade sequential

|1=†Uluops

|2=†Lakotemys

|3=†Pechemys

}}

|3={{clade sequential

|1=†Toremys

|2=†Dorsetochelys

|3=†Pleurosternon

}}

}}

}}

}}

}}

|2={{clade sequential

|1=†Compsemydidae

|2=†Platychelyidae

|3=Pleurodira (side-necked turtles)

}}

}}

|2={{clade

|1={{clade sequential

|1=†Solnhofia

|2=†Santanachelys

|3=†Thalassochelydia

}}

|2={{clade

|1={{clade

|1=†Macrobaenidae

|2=†Xinjiangchelyidae

}}

|2=crown-group Cryptodira

}}

}}

}}

}}

}}

}}

}}

}}

}}}}

• Aragochersis{{Cite journal|author1=A. Pérez-García |author2=E. Espílez |author3=L. Mampel |author4=L. Alcalá |year=2019 |title=A new basal turtle represented by the two most complete skeletons of Helochelydridae in Europe |journal=Cretaceous Research |volume=107 |article-number=104291 |doi=10.1016/j.cretres.2019.104291 |s2cid=210279023 }} Escucha Formation, 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 Grünsandstein Formation, Germany, Late Cretaceous (Cenomanian), Cambridge Greensand, England, Albian-Cenomanian, France, Spain, Cenomanian
• Trachydermochelys phlyctaenus Seeley 1869 (revised Joyce, 2022{{Cite journal |last=Joyce |first=Walter G. |date=2022-10-04 |title=A review of helochelydrid shell material from late Albian to early Cenomanian greensands of Southern England, United Kingdom |journal=The Anatomical Record |volume=308 |issue=6 |language=en |pages=1633–1645 |doi=10.1002/ar.25086 |pmid=36193668 |s2cid=252693787 |issn=1932-8486|doi-access=free |pmc=12062560 }}), Cambridge Greensand, England, Albian-Cenomanian
• Naomichelys 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)

Indeterminate remains most similar to “Helochelydra” anglica and “Helochelydra” bakewelli have been reported from the Berriasian aged Angeac-Charente bonebed of France.Ronan Allain, Romain Vullo, Lee Rozada, Jérémy Anquetin, Renaud Bourgeais, et al.. [https://hal.archives-ouvertes.fr/hal-03264773/document 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

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{{cite web |url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=56005 |title=†Helochelydridae Nopsca 1928 |work=Paleobiology Database |publisher=Fossilworks |access-date=17 December 2021}}

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{{Pantestudines}}

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