Helochelydra

Helochelydra is an extinct genus of extinct stem turtle known from the Early Cretaceous (Barremian) of the Isle of Wight, southern England.^[1][2][3][4]

Helochelydra Temporal range: Early Cretaceous Barremian PreꞒ Ꞓ O S D C P T J K Pg N ↓
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Pantestudines
Clade:	Testudinata
Family:	†Helochelydridae
Genus:	†Helochelydra Nopcsa, 1928
Type species
†Helochelydra nopcsai Lapparent de Broin and Murelaga, 1999

Phylogeny

Helochelydra is a member of the stem turtle family Helochelydridae, which is known from Late Jurassic to Late Cretaceous deposits in North America and Europe. Cladistic analysis recovers Helochelydridae outside the clade leading to crown turtles (Testudines).^[5]

Taxonomy

Helochelydra was named in 1928 by Franz Baron Nopcsa for a partial shell (NHMUK R171) from the Early Cretaceous Wessex Formation of the Isle of Wight that Lydekker (1889) had referred to Tretosternon punctatum, a turtle taxon from the Purbeck Group of Dorset, but no species name was provided.^[6][7] Lapparent de Broin and Murelaga (1999) recognized Helochelydra as closely related to the Late Cretaceous stem turtle Solemys, and erected the type species epithet nopcsai for NHMUK R171, even as they considered Tretosternon a possible synonym of Pleurosternon.^[8] The turtles "Trionyx" bakewelli and "Platychelys" anglica were referred to Helochelydra by Milner (2004) based on morphological similarities with the shell of the type species, but were placed in Compsemyidae by Joyce et al. (2012).^[5]

References

1. A. R. Milner. 2011. Turtles. Palaeontological Association Field Guide to Fossils 14:295-304.
2. "Helochelydra". www.gbif.org. Global Biodiversity Information Facility. Retrieved 2020-01-31.
3. "Fossilworks: Helochelydra". fossilworks.org. Fossilworks. Retrieved 17 December 2021.
4. Joyce, Walter G.; Rabi, Márton; Clark, James M.; Xu, Xing (2016-10-28). "A toothed turtle from the Late Jurassic of China and the global biogeographic history of turtles". BMC Evolutionary Biology. 16 (1): 236. doi:10.1186/s12862-016-0762-5. PMC 5084352. PMID 27793089.
5. W. G. Joyce, S. D. Chapman, R. T. J. Moody, C. A. Walker (2011) The skull of the solemydid turtle Helochelydra nopcsai from the Early Cretaceous of the Isle of Wight (UK) and a review of Solemydidae. Special Papers in Palaeontology: 75-97.
6. LYDEKKER, R. (1889). Catalogue of the Fossil Reptilia and Amphibia in the British Museum (Natural History). III. Chelonia. Trustees Brit. Mus. (Nat. Hist.), London, pp. 1-239.
7. NOPCSA, F. (1928). Palaeontological notes on the reptiles. 4. Helochelydra and Hylaeochelys, two little known tortoises from the Wealden and Purbeck Formations. Geol. Hungar., Ser. Palaeont. 1(1): 44-50.
8. F. de Lapparent and X. Murelaga. 1999. Turtles from the Upper Cretaceous of Lano (Iberian Peninsula). Estudios del Museo de Ciencias Naturales de Alava 14(1):135-211.