Stupendemys

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Stupendemys
Skeletal reconstruction of Stupendemys geographicus at the AMNH

Skeletal reconstruction of Stupendemys geographicus at the AMNH

Temporal occurrence
Miocene ( Huayquerian ) to Pliocene ( Montehermosum )
9 to 4 million years
Locations
Systematics
Turn-Neck Turtles (Pleurodira)
Eupleurodira
Podocnemidoidea
Podocnemididae
Podocnemidinae
Stupendemys
Scientific name
Stupendemys
Wood , 1976

Stupendemys was a genus of very large freshwater turtles in the Podocnemididae family. Fossil remains of the genus have been found in present-day Venezuela and western Brazil. In addition to the type species Stupendemys geographicus , only one other species ( Stupendemys souzai ) has been describedso far. The latter species allocation is, however, controversial and is not recognized by all experts.

Etymology and history of research

The generic name Stupendemys (from English "stupendous" = "enormous", "huge") aptly refers to the extraordinary size of the animals. The first fossils were recovered from the Urumaco Formation in northern Venezuela in the summer of 1972 as part of a paleontological expedition by Harvard University . The genus and type species were first described in 1976 by Roger Conant Wood . Wood's first description was based on the holotype (MCNC 244) at the Museo de Ciencias Naturales in Caracas (Venezuela) and other fossil evidence. Including a well-preserved carapace with a length of 218 cm (MCZ P 4376), which is now in the Museum of Comparative Zoology at Harvard University. Wood realized that Stupendemys must be a turtle with a largely aquatic way of life, but was not sure whether he was looking at a marine or a freshwater one.

In 1985, Rhodin examined the structure of the upper arm bones of Stupendemys , mainly comparing them with sea turtles.

In the 1990s there were reports of finds of Stupendemys from the Solimões Formation in the Brazilian province of Acre . A marine way of life could now be ruled out for these finds. In 2006 the finds from Brazil were combined into a separate species ( Stupendemys souzai ). However, this assignment is considered controversial, as several individual skeletal elements from different sites have been combined without any evidence that they actually belong to the same species. For some skeletal elements it is even doubted that they belong to the genus Stupendemys .

From stupendemys date there is no clearly identifiable evidence of the skull. Considerations that an isolated skull and an isolated lower jaw from the same Brazilian find layers, which were jointly described under the name Caninemys tridentata in 2009 , could be the skull of a smaller Stupendemys species, are purely speculative and also not based on corresponding fossil evidence underpinned. The skull of Caninemys tridentata served as a template for a skeletal reconstruction of Stupendemys geographicus at the American Museum of Natural History . For this, however, the replica of the skull had to be enlarged by around twice the size of the original fossil in order to adapt it to the proportions of the trunk skeleton.

In 2007 Scheyer & Sánches-Villagra published histological studies on the carapace of Stupendemys geographicus .

features

Replica of the carapace (MCZ P 4376) of stupendemys geographicus . The indentation and the thickened, outwardly curved edge of the carapace in the neck area are clearly visible (in the picture above)

Due to the lack of clarity with regard to the taxon Stupendemys souzai , the description of the generic characteristics is based on Wood, 1976:

  • Giant growth
  • The carapace is flattened and shows an anterior indentation in the neck area
  • The edge of the carapace is clearly thickened in the area of ​​this indentation and curved outwards.
  • Strongly developed cervical vertebrae
  • The shaft of the humerus , which is also extremely solid, has an approximately triangular cross-section
  • The femur is just as strong and flattened dorsoventrally .

Stupendemys geographicus is the largest known freshwater turtle in the history of the earth . Wood gives in his first description for the armor size of the holotype a length of about 2.30 meters and a width of 1.90-1.95 meters. However, larger specimens were found later. For a carapace (UNEFM − CIAPP − 2002−01) at the Center of Archeology, Anthropology and Paleontology of the Universidad Nacional Experimental Francisco de Miranda (UNEFM) in Coro (Venezuela), a length of 3.30 meters and a width of 2.18 meters indicated. The whole animal was probably up to 4 meters long.

The largest South American freshwater turtle today, the arraus turtle ( Podocnemis expansa ), on the other hand, reaches a maximum shell length of only about one meter with a body mass of about 50 kilograms. The largest species of sea turtle living today, the leatherback turtle ( Dermochelys coriacea ), has a body mass of up to 650 kg with a carapace of up to 2.10 meters. Reports of a leatherback turtle with a body mass of 916 kg, however, are considered unreliable. In view of the above-mentioned carapace lengths and the considerably more massive structure of the shell compared to Dermochelys coriacea , a much higher body mass can be assumed for Stupendemys .

species

  • Stupendemys geographicus Wood, 1976 ( type species )
  • Stupendemys souzai Bocquentin & Melo, 2006

Paleecology

Habitat and way of life

The size and the strongly flattened carapace of Stupendemys indicate a largely aquatic way of life. The finds of Stupendemys geographicus from Venezuela come from the so-called "capa de huesos" ("bone layer") or "capa de tortugas" ("turtle layer ") from the most hanging parts of the Urumaco formation . The sediments of the Urumaco Formation were deposited in the delta area of an extensive river system with numerous different habitats, from continental, savanna-like plains to rivers, still waters , freshwater swamps and brackish water- bearing estuaries to shallow marine coastal zones. Therefore it was initially unclear whether the Stupendemys was a freshwater turtle or a marine form.

The Solimões formation, from which the Brazilian finds from Stupendemys come, on the other hand, was deposited in a vast alluvial fan ("Megafan") with river channels, lakes and flood plains at the eastern foot of the young Andes, far away from the sea. The general consensus today therefore assumes that Stupendemys was a genus of freshwater turtles. However, there is still the theoretical possibility that the finds from Venezuela and Brazil each represent separate species of Stupendemys that were adapted to different habitats.

No reliable information can be given about the diet of Stupendemys .

Individual age

The leatherback turtle ( Dermochelys coriacea ) shows the highest growth rate of all turtles living today with an average rate of over 8.5 cm / year in the youth stage. This extremely high growth rate for turtles is expressed in leatherback turtles in a special structure of the bone structure, especially on the joint heads of the humerus . Similar structures of the bone structure, which indicate high growth rates, are found in Archelon ischyros from the Upper Cretaceous of North America, but not in Stupendemys . For all other turtle species today, a growth rate of between 3.0 and 5.3 cm / year can be assumed.

Scheyer & Sánches-Villagra, 2007 use these key data to estimate the individual age of the largest specimen found so far (UNEFM − CIAPP − 2002−01) of Stupendemys . Assuming a high, histologically not proven, growth rate, the authors believe that the minimum age is 30 years. Assuming the more realistic, lower growth rates, an individual age of around 60–110 years can be assumed.

literature

  • E.-A. Cadena, TM Scheyer, JD Carrillo-Briceño, R. Sánchez, O. A Aguilera-Socorro, A. Vanegas5, M. Pardo, DM Hansen and MR Sánchez-Villagra. 2020. The Anatomy, Paleobiology, and Evolutionary Relationships of the Largest Extinct Side-necked Turtle. Science Advances. 6 (7); eaay4593. DOI: 10.1126 / sciadv.aay4593
  • Barry Cox, Dougal Dixon, Brian Gardiner: Dinosaurs and Other Animals of Ancient Times. The great encyclopedia of prehistoric wildlife. Gondrom Verlag, Bindlach 1989, ISBN 3-8112-1138-2 .
  • Marcelo S. de la Fuente, Juliana Sterli, Ignacio Maniel: Origin, Evolution and Biogeographic History of South American Turtles. Springer Earth System Sciences, Cham-Heidelberg-New York-Dordrecht-London 2014, ISBN 978-3-319-00517-1 ( reading sample ).

Individual evidence

  1. ↑ a b c d e f R. C. Wood: Stupendemys geographicus, the World's largest Turtle. In: Breviora - Museum of Comparative Zoology. No. 436, 31 pp., 1976 ( digitized version ).
  2. ↑ a b A. GJ Rhodin: Comparative chondro-osseous development and growth of marine turtles. In: Copeia. Volume 1985, 1985, pp. 752-771.
  3. ↑ F. de Lapparent de Broin, J. Bocquentin, FR Negri: Gigantic turtles (Pleurodira, Podocnemididae) from the Late Miocene-Early Pliocene of South Western Amazon. In: Bulletin de l'Institut Fraçais d'Études Andines. Volume 22, No. 3, 1993, pp. 657-670 ( digitized version ).
  4. ↑ J. Bocquentin, FR Negri: Sobre la ocorrencia do quelônio gigante Stupendemys (Pleurodira, Podocnemididae, Podocnemidinae) no Mioceno-superior Plioceno da Amazônia sul-ocidental. In: Ameghiniana. Volume 30, No. 3, 1993, pp. 324-325.
  5. ^ ES Gaffney, KE Campbell, RC Wood: Pelomedusoid side-necked turtles from Late Miocene Sediments in southwestern Amazonia. In: American Museum Novitates. No. 3245, 1998, pp. 1-11 ( digitized version ).
  6. ↑ a b J. Bocquentin, J. Melo: Stupendemys souzai sp. nov. (Pleurodira, Podocnemididae) from the Miocene-Pliocene of the Solimões Formation, Brazil. In: Revista Brasileira de Paleontologia. Volume 9, No. 2, 2006, ISSN  1519-7530 , pp. 187-192 ( digitized PDF file; 643.83 KB ).
  7. ^ A b P. A. Meylan, ES Gaffney, D. de Almeida Campos: Caninemys, a new side-necked turtle (Pelomedusoides: Podocnemididae) from the Miocene of Brazil. In: American Museum Novitates. No. 3639, 2009, pp. 1–26 ( digitized version ).
  8. ↑ ES Gaffney, PA Meylan, RC Wood, E. Simons, D. de Almeida Campos: Evolution of the Side-Necked Turtles: The Family Podocnemididae In: Bulletin of the American Museum of Natural History. No. 350, 237 pp., 2011 ( digitized version ).
  9. ↑ a b c d T. M. Scheyer, MR Sánches-Villagra: Carapace bone histology in the giant pleurodiran turtle Stupendemys geographicus: Phylogeny and function. In: Acta Palaeontologica Polonica. Volume 52, No. 1, 2007, pp. 137-154 ( digitized version ).
  10. ↑ CR McClain, MA Balk, MC Benfield, TA Branch, C. Chen, J. Cosgrove, ADM Dove, LC Gaskins, RR Helm, FG Hochberg, FB Lee, A. Marshall, SE McMurray, C. Schanche, SN Stone, AD Thaler: Sizing ocean giants: patterns of intraspecific size variation in marine megafauna. In: PeerJ. 3: e715, 2015. doi : 10.7717 / peerj.715 .
  11. ^ A b M. R. Sánches-Villagra & TM Scheyer: Fossil turtles from the northern neotropics: The Urumaco sequence fauna and finds from other localities in Venezuela and Colombia. In: MR Sánchez-Villagra, OA Aguilera, AA Carlini (Eds.): Urumaco and Venezuelan Paleontology - The Fossil Record of the Northern Neotropics. Indiana University Press, 2010, ISBN 978-0-253-35476-1 , pp. 173-191 ( digitized ).
  12. ^ MR Sánches-Villagra, O. Aguilera, I. Horovitz: The Anatomy of the World's Largest Extinct Rodent. In: Science. Volume 301, 2003, pp. 1708-1710 ( digitized version ).
  13. ↑ E. Μ. Latrubesse, J. Bocquentin, JCR Santos, CG Ramonell: Paleoenvironmental Model for the Late Cenozoic of Southwestern Amazonia: Paleontology and Geology. In: Acta Amazonica. Volume 27, No. 2, 1997, pp. 103-117 ( digitized version ).
  14. ^ GR Zug, JF Parham: Age and Growth in Leatherback Turtles, Dermochelys coriacea (Testudines: Dermochelyidae): A Skeletochronological Analysis. In: Chelonian Conservation and Biology. Volume 2, No. 2, 1996, pp. 244-249 ( digitized version ).
  15. ^ ML Snover, AGJ Rhodin: Comparative Ontogenetic and Phylogenetic Aspects of Chelonian Chondro-Osseous Growth and Skeletochronology. In: J. Wyneken, MH Godfrey & V. Bels (Eds.): Biology of Turtles - From Structures to Strategies of Life. CRC Press, 2007, ISBN 978-0-8493-3339-2 , pp. 17-43 ( digitized version ).