Podocnemididae Explained

Podocnemididae is a family of pleurodire (side-necked) turtles, once widely distributed. Most of its 41 genera and 57 species are now extinct. Seven of its eight surviving species are native to South America: the genus Peltocephalus, with two species, only one of which is extant (P. dumerilianus, the Big-headed Amazon River turtle); and the genus Podocnemis, with six living species of South American side-necked river turtles and four extinct. There is also one genus native to Madagascar: Erymnochelys, the Madagascan big-headed turtle, whose single species E. madagascariensis.

Like other pleurodire turtles, podocs have a "side-necked" defensive posture, turning the head sideways to hide it under the shell. Another characteristic of pleurodires is that the pelvis is fused to the shell which prevents pelvic motion, making it difficult to walk on land.^{[1] [2]} Podocnemididae turtles live in aquatic environments and have shells streamlined to aid in swimming.^[3]

Taxonomy and systematics

According to Ferreira et al. (2015), the family name derives from two Greek words: "podos" (foot) and "cnemis" (leg armor worn by Roman soldiers.)

To clarify some closely related names:

• Podocnemidae (Baur, 1893) is an alternate but less commonly-used name for the same biological group as family Podocnemididae (Cope, 1868).^[4]
• Epifamily Podocnemidinura: The family Podocnemididae has two sister families (Hamadachelys and Brasilemys); the relationship of these three families is sometimes recognized by grouping them as the epifamily Podocnemidinura.
• Superfamily Podocnemidoidea: At a higher level yet, the epifamily Podocnemidinura is grouped with the family Bothremydidae to form the superfamily Podocnemidoidea.^[5]
• Podocnemidinae: An earlier classification, rejected by Gaffney, treated Podocnemididae as a subfamily (Podocnemidinae) within the closely related family Pelomedusidae.^[6])

According to Gaffney et al. (2011), the family Podocnemididae can be diagnosed from its cranial traits including "the unique possession of a cavum pterygoidei formed by the basisphenoid, pterygoid, prootic, and quadrate [bones], underlain by the pterygoid and basisphenoid."

The pocnemid family dates to the late Cretaceous; it includes 20 genera and 30 species. Only three genera (and eight species) survive.

The three living genera of Podocnemididae (one of which is monotypic) are:

• Erymnochelys – Madagascan big-headed turtle
• Peltocephalus
  • Peltocephalus dumerilianus – Big-headed Amazon River turtle
  • †Peltocephalus maturin Late Pleistocene^[7]
• Podocnemis – South American side-necked river turtles

Taxonomy

Fossils show that Podocnemidids were once found in Europe, Asia, North America, and Africa. Stupendemys lived around 5.5 million years ago in northern South America, and was the largest freshwater turtle with a carapace length of 2.4m (07.9feet), the largest of any known turtle and is the largest pleurodire known.^[8] While Peltocephalus and Erymnochelys have often been recovered as more closely related to each other than to Podocnemis in morphological analyses,^{[9] [10]} genetic studies have found Erymochelys to be more closely related to Podocnemis than to Peltocephalus.^{[11] [12]}

Genera:

• Stem group taxa (Podocnemidoidae)
  • †Brasilemys^[13] Romualdo Formation, Brazil, Early Cretaceous (Albian)
  • †Amabilis^[14] São José do Rio Preto Formation, Brazil, Late Cretaceous (Santonian)
  • †Hamadachelys Kem Kem Group, Morocco, Late Cretaceous (Cenomanian)
  • †Portezueloemys Portezuelo Formation, Argentina, Late Cretaceous (Turonian)
  • †Cambaremys Marília Formation, Brazil, Late Cretaceous (Maastrichtian)
  • †Bauruemys Presidente Prudente Formation, Brazil, Late Cretaceous (Campanian)
  • †Roxochelys Adamantina Formation, Brazil, Campanian
  • Family †Peiropemydidae
    • †Peiropemys Marília Formation, Brazil, Maastrichtian
    • †Pricemys Marília Formation, Brazil, Maastrichtian
    • †Lapparentemys Santa Lucía Formation, Bolivia, Paleocene
    • †Yuraramirim^[15] Adamantina Formation, Brazil, Campanian
  • Family Podocnemididae (crown group)
  • †Caninemys Northern South America, Miocene
    • Subfamily Podocnemidinae
      • †Cerrejonemys Cerrejón Formation, Colombia, Paleocene
      • Podocnemis South America, Miocene-Recent
    • Subfamily Erymnochelyinae
      • †Gestemys Geste Formation, Argentina, Eocene
      • †Stupendemys^[16] Northern South America, Miocene
      • †Carbonemys Cerrejón Formation, Colombia, Paleocene
      • Peltocephalus Northern South America, Late Pleistocene-Recent
      • †Ragechelus^[17] Farin-Doutchi Formation, Niger, Maastrichtian
      • Erymnochelyini (formerly the "Erymnochelys group")
        • †Apeshemys^[18] (formerly "Podocnemis" aegyptiaca) Egypt, Early Miocene
        • †Eocenochelus Eocene, Europe
        • Erymnochelys Madagascar, Recent
        • †Shetwemys (formerly "Podocnemis" fajumensis) Jebel Qatrani Formation, Egypt, Oligocene Shumaysi Formation, Saudi Arabia, Oligocene
        • †Turkanemys Kenya, Miocene-Pliocene
        • †Kenyemys Kenya, Miocene-Pliocene
        • †Mokelemys Democratic Republic of the Congo, Pliocene
      • Stereogenyina
        • †Stereogenys cromeri Qasr el Sagha Formation, Egypt, Late Eocene
        • †Andrewsemys^[19] (formerly "Stereogenys" libyca) Egypt, Late Eocene-Early Oligocene
        • †Cordichelys Egypt, Late Eocene
        • †Lemurchelys Moghara Formation, Egypt, Early Miocene
        • †"Podocnemis" bramlyi Moghara Formation, Egypt, Early Miocene
        • †Latentemys Egypt, Miocene
        • †Bairdemys Late Oligocene-Miocene, Americas
        • †Brontochelys Bugti Hills, Pakistan Early Miocene
        • †Shweboemys Pliocene-Pleistocene, Myanmar
        • †Piramys^[20] India, Late Miocene
      • Incertae sedis
        • †Neochelys Eocene, Europe
        • †"Stereogenys" podocnemoides Qasr el Sagha Formation, Egypt, Late Eocene
        • †Dacquemys Birket Qarun Formation, Egypt, Late Eocene, Jebel Qatrani Formation, Egypt, Early Oligocene
        • †Albertwoodemys Jebel Qatrani Formation, Egypt, Oligocene
        • †Mogharemys Moghara Formation, Egypt, Early Miocene

Morphology based cladogram after Ferreira et al. 2024^[21]

External links

• • • Web site: Podocnemididae. 2008-01-22. https://web.archive.org/web/20081011004704/http://www.jcvi.org/reptiles/families/podocnemididae.php. 2008-10-11. dead.

Notes and References

1. Wise. Taylor B.. Stayton. C. Tristan. 2017-03-01. Side-necked Versus Hidden-necked: A Comparison of Shell Morphology Between Pleurodiran and Cryptodiran Turtles. Herpetologica. 73. 1. 18. 10.1655/HERPETOLOGICA-D-15-00038. 90226667 . 0018-0831.
2. Sánchez-Villagra. Marcelo R.. Winkler. Jasmin D.. Wurst. Linda. 2007-04-19. Autopodial skeleton evolution in side-necked turtles (Pleurodira): Pleurodire autopodial evolution. Acta Zoologica. en. 88. 3. 199–209. 10.1111/j.1463-6395.2007.00267.x. 83721738 .
3. Mayerl. Christopher J.. Brainerd. Elizabeth L.. Blob. Richard W.. 2016-06-23. Pelvic girdle mobility of cryptodire and pleurodire turtles during walking and swimming. The Journal of Experimental Biology. 219. 17. 2650–2658. 10.1242/jeb.141622. 27340204. 0022-0949. free.
4. Ferreira . Gabriel S. . Rincón . Ascanio D. . Solórzano . Andrés . Langer . Max C. . 2015 . The last marine pelomedusoids (Testudines: Pleurodira): a new species of Bairdemys and the paleoecology of Stereogenyina . . 3 . 1–29 . 10.7717/peerj.1063 . 26157628 . 4493680 . 2019-02-20 . free . 2017-12-02 . https://web.archive.org/web/20171202051058/https://peerj.com/articles/1063.pdf . dead .
5. Gaffney. E. S.. Eugene S. Gaffney . Tong . H.. Meylan. P. A.. Evolution of the side-necked turtles: The families Bothremydidae, Euraxemydidae, and Araripemydidae . . 300. 1–700. American Museum of Natural History . New York . 2006-11-17. 10.1206/0003-0090(2006)300[1:EOTSTT]2.0.CO;2. 2246/5824. 85790134 . The relationships of the family Podocnemididae to its sister taxa Hamadachelys and Brasilemys are recognized by placing them in the epifamily Podocnemidinura. The epifamily Podocnemidinura is the sister group to the family Bothremydidae, and together they form the superfamily Podocnemidoidea..
6. Book: Fritz Jürgen Obst . 1998 . Pelomedusinae . H. G. Cogger . R. G. Zweifel . Encyclopedia of Reptiles and Amphibians . 112–113 . . San Diego . 0-12-178560-2.
7. Ferreira . G. S. . Nasciemento . E. R. . Cadena . E. A. . Cozzuol . M. A. . Farina . B. M. . Pacheco . M. L. A. F. . Rizzutto . M. A. . Langer . M. C. . 2024 . The latest freshwater giants: a new Peltocephalus (Pleurodira: Podocnemididae) turtle from the Late Pleistocene of the Brazilian Amazon . Biology Letters . 20 . 3 . 20240010 . 10.1098/rsbl.2024.0010 . 38471564 . 10932709 .
8. Cadena. E.-A.. Scheyer. T. M.. Carrillo-Briceño. J. D.. Sánchez. R.. Aguilera-Socorro. O. A. Vanegas. A.. Pardo. M.. Hansen. D. M.. Sánchez-Villagra. M. R.. February 2020. The anatomy, paleobiology, and evolutionary relationships of the largest extinct side-necked turtle. Science Advances. en. 6. 7. eaay4593. 10.1126/sciadv.aay4593. 32095528 . 2375-2548. 7015691. 2020SciA....6.4593C .
9. de la Fuente . Marcelo S. . Maniel . Ignacio J. . Ruiz . Pablo González . Ledesma . Jonathan . Deraco . Maria V. . del Papa . Cecilia . Herrera . Claudia . 2022-12-31 . A new podocnemidid (Pleurodira: Pelomedusoides) from the Eocene of north-western Argentina, with comments on its evolutionary relationships and palaeoenvironmental settings . Journal of Systematic Palaeontology . en . 20 . 1 . 10.1080/14772019.2022.2081939 . 1477-2019.
10. Ferreira . Gabriel S. . Bronzati . Mario . Langer . Max C. . Sterli . Juliana . March 2018 . Phylogeny, biogeography and diversification patterns of side-necked turtles (Testudines: Pleurodira) . Royal Society Open Science . en . 5 . 3 . 171773 . 10.1098/rsos.171773 . 2054-5703 . 5882704 . 29657780. 2018RSOS....571773F .
11. Vargas-Ramírez . Mario . Castaño-Mora . Olga V. . Fritz . Uwe . 2008-12-20 . Molecular phylogeny and divergence times of ancient South American and Malagasy river turtles (Testudines: Pleurodira: Podocnemididae) . Organisms Diversity & Evolution . en . 8 . 5 . 388–398 . 10.1016/j.ode.2008.10.001 . 1439-6092.
12. Selvatti . Alexandre Pedro . Moreira . Filipe Romero Rebello . Carvalho . Daniel Cardoso . Prosdocimi . Francisco . Russo . Claudia Augusta de Moraes . Junqueira . Ana Carolina Martins . June 2023 . Phylogenomics reconciles molecular data with the rich fossil record on the origin of living turtles . Molecular Phylogenetics and Evolution . en . 183 . 107773 . 10.1016/j.ympev.2023.107773. 36977459 .
13. The oldest pre-Podocnemidid turtle (Chelonii, Pleurodira), from the Early Cretaceous, Ceara State, Brasil, and its environment. De Lapparent. France. Treballs del Museu de Geologia de Barcelona. 9 . 43–95. December 4, 2021. In the Podocnemidoidea, Brasilemys n.g. represents the earliest known specimen of the Podocnemidoidae, immediately after the divergence of the Bothremydidae. It is part of the formidable radiation in the Pelomedusoides which occurs during the early Cretaceous when South America separated from Africa..
14. Hermanson. Guilherme. Iori. Fabiano V.. Evers. Serjoscha W.. Langer. Max C.. Ferreira. Gabriel S.. 2020. A small podocnemidoid (Pleurodira, Pelomedusoides) from the Late Cretaceous of Brazil, and the innervation and carotid circulation of side-necked turtles. Papers in Palaeontology. en. 6. 2. 329–347. 10.1002/spp2.1300. 2056-2802. free. 2020PPal....6..329H .
15. Ferreira. Gabriel S.. Iori. Fabiano V.. Hermanson. Guilherme. Langer. Max C.. September 2018. New turtle remains from the Late Cretaceous of Monte Alto-SP, Brazil, including cranial osteology, neuroanatomy and phylogenetic position of a new taxon. PalZ. en. 92. 3. 481–498. 10.1007/s12542-017-0397-x. 2018PalZ...92..481F . 134701879 . 0031-0220.
16. Eugene S. Gaffney. Peter A. Meylan. Roger C. Wood. Elwyn Simons. Diogenes De Almeida Campos. 2011. Evolution of the Side-Necked Turtles: The Family Podocnemididae. Bulletin of the American Museum of Natural History. 350. 1–237. 10.1206/350.1. 2246/6110. 83775718 . The family Podocnemididae consists of 20 genera and 30 species considered here as valid and diagnosable by cranial characters. Three of these genera and eight species persist into the Recent fauna, barely reflecting the evolutionary diversity and distribution of the group. The family extends from the late Cretaceous to the Recent and occurs in North and South America, Europe, Asia, and Africa..
17. Broin. France de Lapparent de. Chirio. Laurent. Bour. Roger. October 2020. The oldest erymnochelyine turtle skull, Ragechelus sahelica n. gen., n. sp., from the Iullemmeden basin, Upper Cretaceous of Africa, and the associated fauna in its geographical and geological context. Geodiversitas. 42. 25. 455–484. 10.5252/geodiversitas2020v42a25. 226238494 . 1280-9659. free.
18. Pérez-García . A. . New shell information and new generic attributions for the Egyptian podocnemidid turtles "Podocnemis" fajumensis (Oligocene) and "Podocnemis" aegyptiaca (Miocene) . 2021 . Fossil Record . 24 . 2 . 247–262 . 10.5194/fr-24-247-2021 . free . 2021FossR..24..247P .
19. Pérez-García. Adán. 2019-03-16. New information and establishment of a new genus for the Egyptian Paleogene turtle 'Stereogenys' libyca (Podocnemididae, Erymnochelyinae). Historical Biology. 31. 3. 383–392. 10.1080/08912963.2017.1374383. 2019HBio...31..383P . 90915135 . 0891-2963.
20. Ferreira. Gabriel S.. Bandyopadhyay. Saswati. Joyce. Walter G.. 2018-11-15. A taxonomic reassessment of Piramys auffenbergi, a neglected turtle from the late Miocene of Piram Island, Gujarat, India. PeerJ. en. 6. e5938. 30479901 . 10.7717/peerj.5938. 2167-8359. 6240434 . free .
21. Ferreira . G. S. . Nascimento . E. R. . Cadena . E. A. . Cozzuol . M. A. . Farina . B. M. . Pacheco . M. L. A. F. . Rizzutto . M. A. . Langer . M. C. . March 2024 . The latest freshwater giants: a new Peltocephalus (Pleurodira: Podocnemididae) turtle from the Late Pleistocene of the Brazilian Amazon . Biology Letters . en . 20 . 3 . 10.1098/rsbl.2024.0010 . 1744-957X . 10932709 . 38471564.