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Helochelydridae Temporal range: Berriasian–Maastrichtian PreꞒ Ꞓ O S D C P T J K Pg N
Helochelydra nopcsai skull
Shell of Naomichelys
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Pantestudines
Clade:	Testudinata
Clade:	Perichelydia
Family:	†Helochelydridae Nopsca, 1928
Genera
See text
Synonyms
Solemydidae Lapparent and Murelaga 1997

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 (granicones) 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 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.

Genera

• Aragochersis 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), 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.

References

1. ^ "†Helochelydridae Nopsca 1928". Paleobiology Database. Fossilworks. Retrieved 17 December 2021.
2. Joyce WG; Rabi M; Clark JM; Xu X. (2016). "A toothed turtle from the Late Jurassic of China and the global biogeographic history of turtles". BMC Evolutionary Biology. 16 (1): 236. Bibcode:2016BMCEE..16..236J. doi:10.1186/s12862-016-0762-5. PMC 5084352. PMID 27793089.
3. Gentry, Andrew D.; Ebersole, Jun A. (2021-08-10). "The first occurrence of the stem turtle Naomichelys from the Late Cretaceous of eastern North America". Historical Biology. 34 (7): 1129–1136. doi:10.1080/08912963.2021.1962855. ISSN 0891-2963. S2CID 238677455.
4. Scheyer, T. M.; Pérez-García, A.; Murelaga, X. (March 2015). "Shell bone histology of solemydid turtles (stem Testudines): palaeoecological implications". Organisms Diversity & Evolution. 15 (1): 199–212. Bibcode:2015ODivE..15..199S. doi:10.1007/s13127-014-0188-0. ISSN 1439-6092. S2CID 18628827.
5. WALTER, J.G., CHAPMAN S.D., MOODY R.T.J., and WALKER, C.A. 2011. 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.
6. ^ Hans-Dieter Sues (August 6, 2019). The Rise of Reptiles. 320 Million Years of Evolution. Johns Hopkins University Press. p. 53. ISBN 9781421428680.
7. Joyce, Walter G. (April 2017). "A review of the fossil record of basal Mesozoic turtles" (PDF). Bulletin of the Peabody Museum of Natural History. 58 (1): 65–113. doi:10.3374/014.058.0105. S2CID 54982901. Retrieved July 9, 2017.
8. Rollot, Yann; Evers, Serjoscha W.; Joyce, Walter G. (December 2021). "A redescription of the Late Jurassic (Tithonian) turtle Uluops uluops and a new phylogenetic hypothesis of Paracryptodira". Swiss Journal of Palaeontology. 140 (1): 23. Bibcode:2021SwJP..140...23R. doi:10.1186/s13358-021-00234-y. ISSN 1664-2376. PMC 8550081. PMID 34721284.
9. Rollot, Yann; Evers, Serjoscha W.; Pierce, Stephanie E.; Joyce, Walter G. (2022-11-02). "Cranial osteology, taxonomic reassessment, and phylogenetic relationships of the Early Cretaceous (Aptian-Albian) turtle Trinitichelys hiatti (Paracryptodira)". PeerJ. 10: e14138. doi:10.7717/peerj.14138. ISSN 2167-8359. PMC 9636874. PMID 36345484.
10. Tong, Haiyan; Tortosa, Thierry; Buffetaut, Eric; Dutour, Yves; Turini, Eric; Claude, Julien (January 2022). "A compsemydid turtle from the Upper Cretaceous of Var, southern France". Annales de Paléontologie. 108 (1): 102536. Bibcode:2022AnPal.10802536T. doi:10.1016/j.annpal.2022.102536. S2CID 248792130.
11. Tong, Haiyan; Buffetaut, Eric; Méchin, Patrick; Méchin-Salessy, Annie; Claude, Julien (2023-01-03). "A Solemys Skull from the Late Cretaceous of Southern France". Diversity. 15 (1): 58. doi:10.3390/d15010058. ISSN 1424-2818.
12. A. Pérez-García; E. Espílez; L. Mampel; L. Alcalá (2019). "A new basal turtle represented by the two most complete skeletons of Helochelydridae in Europe". Cretaceous Research. 107: Article 104291. doi:10.1016/j.cretres.2019.104291. S2CID 210279023.
13. ^ Joyce, Walter G. (2022-10-04). "A review of helochelydrid shell material from late Albian to early Cenomanian greensands of Southern England, United Kingdom". The Anatomical Record: ar.25086. doi:10.1002/ar.25086. ISSN 1932-8486. PMID 36193668. S2CID 252693787.
14. 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

v t e Pantestudines
Kingdom: Animalia Phylum: Chordata Class: Sauropsida Clade: Diapsida Clade: Sauria Clade: Archelosauria Sauropsida see Sauropsida Pantestudines see below↓ Pantestudines
Pantestudines †Eorhynchochelys †Eunotosaurus? †Odontochelys †Pappochelys Testudinata †Chinlechelys †Condorchelys †Eileanchelys †Heckerochelys †Indochelys †Kallokibotion †Kayentachelys †Proganochelys †Proterochersis †Spoochelys †Australochelyidae Australochelys Palaeochersis Waluchelys †Meiolaniformes Chubutemys Otwayemys Patagoniaemys Peligrochelys Trapalcochelys Meiolaniidae Gaffneylania Meiolania Ninjemys Niolamia Warkalania †Sichuanchelyidae Laurasichersis Mongolochelys Sichuanchelys †Helochelydridae Aragochersis Helochelydra Helochelys Naomichelys Solemys †Compsemydidae Berruchelus Calissounemys Compsemys Kallokibotion? Peltochelys Riodevemys? Selenemys? Tongemys †Paracryptodira Compsemydidae? Helochelydridae? Pleurosternidae Dinochelys Dorsetochelys Glyptops Pleurosternon Riodevemys? Selenemys? Toremys Uluops Baenidae Arundelemys Arvinachelys Baena Boremys Cedrobaena Chisternon Denazinemys Edowa Eubaena Gamerabaena Gehennachelys Goleremys Hayemys Lakotemys Neurankylus Palatobaena Peckemys Plesiobaena Protobaena Saxochelys Scabremys Stygiochelys Thescelus Trinitichelys †Xinjiangchelyidae Annemys Brodiechelys Camerochelys Chengyuchelys Jastmelchyi Kalasinemys Larachelus Phunoichelys Protoxinjiangchelys Shartegemys Siamochelys Tienfuchelys Undjulemys Xinjiangchelys Yanduchelys †Sinemydidae / Macrobaenidae Anatolemys Appalachemys Asiachelys Aurorachelys Changmachelys Dracochelys Gallica Galvechelone Hongkongochelys Hoyasemys Jeholochelys Judithemys Kirgizemys Liaochelys Macrobaena Manchurochelys Ordosemys Osteopygis Oxemys Sinemys Tienfucheloides Wuguia Xiaochelys Yakemys Yumenemys †Thalassochelydia (sensu Joyce et al., 2021) Aplax Cyrtura Euryaspis Hispaniachelys Neusticemys Owadowia Pelobatochelys Thalassemys Protostegidae? "Eurysternidae" Achelonia Chelonides Eurysternum Hydropelta Idiochelys Palaeomedusa Parachelys "Plesiochelyidae" Craspedochelys Globochelus Hylaeochelys? Jurassichelon? Plesiochelys Portlandemys Tropidemys Sandownidae Angolachelys Brachyopsemys Leyvachelys Sandownia Solnhofia? Testudines see Testudines
See also: Angolachelonia Ankylopoda Mesochelydia Perichelydia Category

• Helochelydridae
• Turtle families