The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

Platemys platycephala
Platemys platycephala
(twist-necked turtle)

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Platemys platycephala (Schneider, 1792)

Common name: twist-necked turtle

Synonyms and Other Names: grooved sideneck turtle, chata

Taxonomy: available through www.itis.govITIS logo

Identification: Platemys platycephala is a relatively small, dark, flattened turtle with a carapace (upper shell) length of only 145-200 mm (5.7-7.85 in) (Pritchard and Trebbau, 1984). Like most chelids (Australo-American sidenecks) the neck draws the head into the shell laterally (Freiberg, 1981; Pritchard and Trebbau, 1984; Obst, 1986; Bonin et al., 2006). The flattened carapace has a wide, median groove or trough bordered by two raised carinae (keels), and the broad plastron (lower shell) is pigmented black or dark brown (Pritchard and Trebbau, 1984; Obst, 1986; Ernst and Barbour, 1989). The small, dark head is smooth, covered by a single large scale dorsally, and typically has orange or orange-brown pigment dorsally (Pritchard, 1979; Pritchard and Trebbau, 1984; Ernst and Barbour, 1989; Bonin et al., 2006). The neck has prominently pointed tubercles or spikes (Pritchard, 1979; Pritchard and Trebbau, 1984; Bonin et al., 2006). No other turtle indigenous to the U.S. shares this unique combination of features. The twist-necked turtle is variously illustrated in Pritchard (1979), Freiberg (1981), Obst (1986, 1998), Ernst and Barbour (1989), Lamar (1997), Bonin et al. (2006), and Krysko et al. (2011: MorphoBank 188573, www.morphobank.org, Project Number p536).

Size: carapace (upper shell) length of 145-200 mm (5.7-7.85 in).

Native Range: Platemys platycephala is indigenous to the Amazon and Orinoco River drainages in Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Peru and Venezuela (Freiberg, 1981; Pritchard and Trebbau, 1984; Ernst and Barbour, 1989; King and Burke, 1989; Iverson, 1992; Bonin et al., 2006).

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Nonindigenous Occurrences: Sometime between 1982-1987 a single P. platycephala was collected by Paul Moler on the Wilderness Country Club Golf Course, Naples, Collier County, Florida, U.S.A. (P. Moler, personal communication 1998, Nonindigenous Species Database Report – phone conversation; Krysko et al., 2011). This individual was still living as a captive in 2011, and a photographic voucher (UF 154589, MorphoBank M88573) of it was used to illustrate Krysko et al. (2011).

Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Platemys platycephala are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
FL198519851Big Cypress Swamp

Table last updated 12/6/2023

† Populations may not be currently present.

Ecology: The twist-necked turtle is carnivorous in captivity, eating small fish, worms, and other animal products; but its diet in the wild is poorly known other than observations of this species feeding on amphibian eggs (Pritchard and Trebbau, 1984; Ernst and Barbour, 1989; Lamar, 1997; Bonin et al., 2006). This aquatic turtle inhabits shallow waters (not large rivers), and prefers crawling on the bottom rather than swimming (Pritchard and Trebbau, 1984; Ernst and Barbour, 1989). They are known to wander overland on the forest floor (Ernst and Barbour, 1989). Female P. platycephala lay a single, brittle-shelled egg on the ground, either buried under leaves or fully exposed in an open depression (Pritchard and Trebbau, 1984; Bonin et al., 2006).

Means of Introduction: Unknown. Probably a pet release.

Status: Not established.

Impact of Introduction: The impacts of this species are currently unknown, as no studies have been done to determine how it has affected ecosystems in the invaded range. The absence of data does not equate to lack of effects. It does, however, mean that research is required to evaluate effects before conclusions can be made.

Remarks: The taxonomy of P. platycephala has been summarized by Pritchard and Trebbau (1984), King and Burke (1989), Bonin et al. (2006), and Bickham et al. (2007). An exhaustive list of vernacular names has been applied to this turtle in various regions of South America and includes “matamata” (Mittermeier et al., 1980; Freiberg, 1981; Pritchard and Trebbau, 1984), a name more commonly applied to the chelid, Chelus fimbriatus. By far the best overviews of the natural history of the twist-necked turtle are by Pritchard and Trebbau (1984) and Bonin et al. (2006).

To a minimal extent this turtle is exploited by the commercial pet trade, with twist-necked turtles from Bolivia typically being exported to Miami, Florida, and Germany (Pritchard and Trebbau, 1984; Bonin et al., 2006).

References: (click for full references)

Bickham, J.W., J.B. Iverson, J.F. Parham, H.-D. Philippen, A.G.J. Rhodin, H.B. Shaffer, P.Q. Spinks, and P.P. van Dijk. 2007. An annotated list of modern turtle terminal taxa with comments on areas of taxonomic instability and recent change. Chelonian Research Monographs 4:173-199.

Bonin, F., B. Devaux, and A. Dupré. 2006. Turtles of the World. [English Edition.] The Johns Hopkins University Press, Baltimore. 416 pp.

Ernst, C.H., and R.W. Barbour. 1989. Turtles of the World. Smithsonian Institution Press, Washington, D.C. and London. 313 pp.

Freiberg, M. 1981. Turtles of South America. T.F.H. Publications, Inc., Neptune, New Jersey. 125 pp.

Iverson, J.B. 1992. A revised checklist with distribution maps of the turtles of the world. First Edition. John B. Iverson, Richmond, Indiana. 363 pp.

King, F.W., and R.L. Burke (editors). 1989. Crocodilian, Tuatara, and Turtle Species of the World. A Taxonomic and Geographic Reference. The Association of Systematics Collections, Washington, DC. 216 pp.

Krysko, K.L., J.P. Burgess, M.R. Rochford, C.R. Gillette, D. Cueva, K.M. Enge, L.A. Somma, J.L. Stabile, D.C. Smith, J.A. Wasilewski, G.N. Kieckhefer III, M.C. Granatosky, and S.V. Nielsen. 2011. Verified non-indigenous amphibians and reptiles in Florida from 1863 through 2010: Outlining the invasion process and identifying invasion pathways and status. Zootaxa 3028:1-64.

Lamar, W. W. 1997. The world’s most spectacular reptiles & amphibians. World Publications, Tampa. 208 pp.

Mittermeier, R.A., F. Medem, and A.G.J. Rhodin. 1980. Vernacular names of South American turtles. Society for the Study of Amphibians and Reptiles Herpetological Circular (9):1-44.

Moler, P. 1998. Personal communication—Herpetologist, Florida Fish and Wildlife Conservation Commission, Gainesville, Florida.

Obst, F.J. 1986. Turtles, Tortoises and Terrapins. St Martin’s Press, New York. 231 pp.

Obst, F.J. 1998. Turtles & tortoises. Pp. 108-125. In: H. G. Cogger and R. G. Zweifel (editors). Encyclopedia of Amphibians & Reptiles. Second Edition. Academic Press, San Diego. 240 pp.

Pritchard, P.C.H. 1979. Encyclopedia of Turtles. T.F.H. Publications, Inc., Neptune, New Jersey. 895 pp.

Pritchard, P.C.H., and P. Trebbau. 1984. The Turtles of Venezuela. Contributions to Herpetology 2. Society for the Study of Amphibians and Reptiles, Ithaca. 403 pp., 47 plates, 16 maps.

Other Resources:
Laurie Vitt's Photographs

Author: Somma, L.A.

Revision Date: 6/29/2023

Citation Information:
Somma, L.A., 2023, Platemys platycephala (Schneider, 1792): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=1224, Revision Date: 6/29/2023, Access Date: 12/6/2023

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.


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Citation information: U.S. Geological Survey. [2023]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [12/6/2023].

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