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Trachemys medemi VARGAS-RAMÍREZ, VALLE, CEBALLOS & FRITZ, 2017

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Higher TaxaEmydidae, Deirochelyinae, Testudinoidea, Testudines (turtles)
Subspecies 
Common NamesE: Atrato slider 
SynonymTrachemys medemi VARGAS-RAMÍREZ, VALLE, CEBALLOS & FRITZ 2017
Trachemys medemi — TTWG 2021 
DistributionColombia (Chocó)

Type locality: Ro Sucio, Chocó, Parque Nacional Natural Los Katíos, Colombia  
Reproduction 
TypesHolotype: IAvH-R-1606 (Instituto de Investigación de Recursos Biologicos Alexander von Humboldt, Colección de Reptiles, Villa de Leyva), leg. Jose V. Rodríguez, H. Pavas, 20 January 1977 
DiagnosisDiagnosis: In addition to its genetic distinctiveness, T. medemi differs from T. scripta and West Indian slider turtles (T. decorata, T. decussata, T. stejnegeri, T. terrapen) by posterior marginal scutes without median notch; males of T. medemi also have no elongated foreclaws. Trach- emys medemi differs from these species, T. gaigeae and T. nebulosa by the presence of ocelli on all costal scutes; T. gaigeae, T. nebulosa, and T. taylori possess a reticulate carapacial pattern (which may be combined with ocelli in T. taylori); a reticulate pattern is lacking in T. medemi. Trachemys grayi, T. ornata, T. venusta, and T. yaquia have never wide brick-red supratemporal stripes as T. medemi.
The two subspecies of T. dorbigni differ from T. medemi by their yellow to orange postorbital stripe, an irregular carapacial pat- tern with often open light wide elements and the much darker plastron with a solid dark or black central figure covering all or most of the plastron in adult turtles. Trachemys medemi differs from geographically neighboring taxa as follows: Compared to T. v. venusta, the postorbital stripe is brick-red (not yellowish or pale brownish red) and much wider, the ocellar pattern of the carapace is less distinct, and the dark plastral figure more extensive, encroaching on most of the plastron. In T. v. venusta, the plastral figure typically covers less than 30%–50% of the plastron and is normally confined to its central part. Trachemys venusta callirostris differs from T. medemi by its spotted chin pattern, a much wider dark plastral figure, and a postorbital stripe not in touch with the eye. Isolated dark plastral whorls do not occur in any of these taxa. 
Comment 
Etymology“We dedicate this new species with deep respect to Federico Medem (1912–1984), born as Count Friedrich Johann von Medem in Remte (then Remten), Latvia, from an old German-Baltic noble family. After his immigration to Colombia (1950), Medem contributed significantly to the development of herpetology of that country, in particular to the knowledge of turtles and crocodiles. Among others, he highlighted the distinctiveness of the Atrato slider (Medem, 1958, 1962, 1975) and provided in 1962 a most detailed morphological description that is repeated in large parts here. Among others, he highlighted that the broad brick-red postorbital stripes of the Atrato slider are a distinctive character in which it differs from its Central American relatives. 
References
  • TTWG; Rhodin, A.G.J., Iverson, J.B., Bour, R., Fritz, U., Georges, A., Shaffer, H.B., and van Dijk, P.P. 2021. Turtles of the World: Annotated Checklist and Atlas of Taxonomy, Synonymy, Distribution, and Conservation Status (9th Ed.). In: Rhodin, A.G.J., Iverson, J.B., van Dijk, P.P., Stanford, C.B., Goode, E.V., Buhlmann, K.A., and Mittermeier, R.A. (Eds.). Chelonian Research Monographs 8:1–472. doi:10.3854/crm.8.checklist.atlas.v9.2021. - get paper here
  • Vargas-Ramírez M, del Valle C, Ceballos CP, Fritz U. 2017. Trachemys medemi n. sp. from northwestern Colombia turns the biogeography of South American slider turtles upside down. J Zool Syst Evol Res. 2017;55:326–339 - get paper here
 
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