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With the exception of the genera Platemys (XY, Chelidae), Staurotypus (XY, Kinosternidae), and Siebenrockiella (XY) and Kachuga smithii (ZW) (Bataguridae), turtles lack heteromorphic sex chromosomes (either XY male heterogamety, or ZW female heterogamety); their mechanism for sex determination is different than in humans. Of the other turtles, only a few do not practice temperature (environmental-) dependent sex determination (TSD). The incubation temperature of the eggs at a sensitive period of development in the middle trimester triggers the gonadal development leading to the sex of the hatchling.
left: Pseudemydura umbrina - western swamp turtle
(photo: Gerald Kuchling);
right: Clemmys insculpta - wood turtle
(photo: James H. Harding)
Two TSD patterns have been discovered in turtles. Pattern I, found in some Bataguridae, and the Carettochelyidae, Cheloniidae, Dermochelyidae, Emydidae, and Testudinidae, has a single transition zone of temperature below which incubation yields nearly or totally 100% males and above which only females are produced. Pattern II, known from the Pelomedusidae, Kinosternidae, Macroclemys temminckii (Chelydridae), and a few Bataguridae has two transition zones, with males predominating at intermediate temperatures and females at both extremes; in most species no constant incubation temperatures within the transition zone yield 100% males (however, exceptionally, constant temperatures do yield 100% males in some Sternotherus and in Chelydra). Pattern I occurs chiefly in turtles in which the adult females are larger than adult males; Pattern II is found mainly in turtles with females smaller than males or in which body size is not dimorphic. The smaller sex is typically produced at the coolest incubation temperatures.
Incubation temperature seems to have no great influence on sex ratios in turtles of the family Chelidae.
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Pelomedusa subrufa, Pelusios gabonensis, Pelusios nanus, Pelusios adansonii, Pelusios broadleyi, Pelusios castaneus, Pelusios chapini, Pelusios castanoides, Pelusios seychellensis, Pelusios williamsi, Pelusios subniger, Pelusios bechuanicus, Pelusios upembae, Pelusios rhodesianus, Pelusios niger, Pelusios carinatus, Pelusios sinuatus, Podocnemis erythrocephala, Podocnemis expansa, Podocnemis lewyana, Podocnemis sextuberculata, Podocnemis unifilis, Podocnemis vogli, Erymnochelys madagascariensis, Peltocephalus dumerilianus, Chelodina longicollis, Chelodina novaeguineae, Chelodina steindachneri, Chelodina expansa, Chelodina parkeri, Chelodina rugosa, Chelodina siebenrocki, Chelodina oblonga, Chelodina pritchardi, Chelodina mccordi, Chelodina reimanni, Elseya dentata, Elseya novaeguineae, Elseya latisternum, Elusor macrurus, Emydura australis, Emydura victoriae, Emydura subglobosa, Emydura krefftii, Emydura macquarrii, Emydura signata, Rheodytes leukops, Pseudemydura umbrina, Hydromedusa maximiliani, Hydromedusa tectifera, Phrynops gibbus, Phrynops vanderhaegei, Phrynops nasutus, Phrynops raniceps, Phrynops dahli, Phrynops tuberculatus, Phrynops zuliae, Phrynops hogei, Phrynops rufipes, Phrynops hilarii, Phrynops geoffroanus, Phrynops williamsi, Platemys platycephala, Acanthochelys pallidipectoris, Acanthochelys radiolata, Acanthochelys macrocephala, Acanthochelys spixii, Chelus fimbriatus, Chelydra serpentina, Chelydra acutirostris, Chelydra rossignonii, Macroclemys temminckii, Chelonia mydas, Natator depressus, Eretmochelys imbricata, Caretta caretta, Lepidochelys kempii, Lepidochelys olivacea, Dermochelys coriacea, Dermatemys mawii, Carettochelys insculpta, Dogania subplana, Palea steindachneri, Pelodiscus sinensis, Trionyx triunguis, Rafetus swinhoei, Rafetus euphraticus, Aspideretes leithii, Aspideretes hurum, Aspideretes nigricans, Aspideretes gangeticus, Nilssonia formosa, Amyda cartilaginea, Pelochelys bibroni, Pelochelys cantorii, Chitra chitra, Chitra indica, Apalone mutica, Apalone spinifera, Apalone ferox, Cycloderma frenatum, Cycloderma aubryi, Cyclanorbis elegans, Cyclanorbis senegalensis, Lissemys punctata, Claudius angustatus, Staurotypus salvinii, Staurotypus triporcatus, Sternotherus odoratus, Sternotherus depressus, Sternotherus minor, Sternotherus carinatus, Kinosternon subrubrum, Kinosternon baurii, Kinosternon acutum, Kinosternon creaseri, Kinosternon leucostomum, Kinosternon scorpioides, Kinosternon integrum, Kinosternon oaxacae, Kinosternon chimalhuaca, Kinosternon alamosae, Kinosternon hirtipes, Kinosternon herrerai, Kinosternon sonoriense, Kinosternon flavescens, Kinosternon angustipons, Kinosternon dunni, Platysternon megacephalum, Batagur baska, Callagur borneoensis, Chinemys nigricans, Chinemys reevesii, Geoclemys hamiltonii, Hardella thurjii, Hieremys annandalii, Kachuga kachuga, Kachuga dhongoka, Kachuga smithii, Kachuga sylhetensis, Kachuga tecta, Kachuga trivittata, Kachuga tentoria, Malayemys subtrijuga, Morenia ocellata, Morenia petersi, Ocadia glyphistoma, Ocadia philippeni, Ocadia sinensis, Orlitia borneensis, Siebenrockiella crassicollis, Cuora amboinensis, Cuora flavomarginata, Cuora galbinifrons, Cuora trifasciata, Cuora aurocapitata, Cuora pani, Cuora mccordi, Cuora zhoui, Cuora yunnanensis, Cyclemys dentata, Cyclemys tcheponensis, Cyclemys n.sp., Geoemyda spengleri, Geoemyda japonica, Geoemyda yuwonoi, Heosemys depressa, Heosemys grandis, Heosemys leytensis, Heosemys silvatica, Heosemys spinosa, Mauremys annamensis, Mauremys japonica, Mauremys mutica, Mauremys iversoni, Mauremys leprosa, Mauremys caspica, Melanochelys tricarinata, Melanochelys trijuga, Notochelys platynota, Pyxidea mouhotii, Rhinoclemmys annulata, Rhinoclemmys areolata, Rhinoclemmys funerea, Rhinoclemmys nasuta, Rhinoclemmys punctularia, Rhinoclemmys melanosterna, Rhinoclemmys pulcherrima, Rhinoclemmys rubida, Sacalia bealei, Sacalia quadriocellata, Sacalia pseudocellata, Clemmys guttata, Clemmys muhlenbergii, Clemmys insculpta, Clemmys marmorata, Emys orbicularis, Emydoidea blandingii, Terrapene coahuila, Terrapene carolina, Terrapene ornata, Terrapene nelsoni, Chrysemys picta, Trachemys scripta, Trachemys gaigeae, Trachemys dorbignyi, Trachemys adiutrix, Trachemys decorata, Trachemys decussata, Trachemys stejnegeri, Trachemys terrapen, Pseudemys concinna, Pseudemys gorzugi, Pseudemys peninsularis, Pseudemys rubriventris, Pseudemys nelsoni, Pseudemys alabamensis, Pseudemys texana, Deirochelys reticularia, Graptemys geographica, Graptemys barbouri, Graptemys pulchra, Graptemys ernsti, Graptemys gibbonsi, Graptemys caglei, Graptemys pseudogeographica, Graptemys ouachitensis, Graptemys versa, Graptemys oculifera, Graptemys flavimaculata, Graptemys nigrinoda, Malaclemys terrapin, Kinixys belliana, Kinixys lobatsiana, Kinixys spekii, Kinixys erosa, Kinixys homeana, Kinixys natalensis, Pyxis planicauda, Pyxis arachnoides, Chersina angulata, Homopus boulengeri, Homopus bergeri, Homopus areolatus, Homopus femoralis, Homopus signatus, Psammobates geometricus, Psammobates oculiferus, Psammobates tentorius, Manouria emys, Manouria impressa, Indotestudo elongata, Indotestudo forstenii, Geochelone elegans, Geochelone platynota, Geochelone pardalis, Geochelone sulcata, Geochelone gigantea, Geochelone arnoldi, Geochelone hololissa, Geochelone radiata, Geochelone yniphora, Geochelone carbonaria, Geochelone denticulata, Geochelone chilensis, Geochelone abingdoni, Geochelone ephippium, Geochelone hoodensis, Geochelone chathamensis, Geochelone nigrita, Geochelone phantastica, Geochelone darwini, Geochelone becki, Geochelone microphyes, Geochelone vandenburghi, Geochelone vicina, Geochelone guentheri, Testudo graeca, Testudo hermanni, Testudo horsfieldii, Testudo kleinmanni, Testudo marginata, Testudo weissingeri, Gopherus flavomarginatus, Gopherus polyphemus, Gopherus agassizii, Gopherus berlandieri, Malacochersus tornieri, subrufa, olivacea, nigra, castanoides, intergularis, williamsi, lutescens, laurenti, subniger, parietalis, geoffroanus, tuberosus, platycephala, melanonota, serpentina, osceola, mydas, agassizii, imbricata, bissa, coriacea, schlegelii, mutica, calvata, spinifera, hartwegi, aspera, pallida, guadalupensis, emoryi, ater, punctata, andersoni, scutata, minor, peltifer, subrubrum, hippocrepis, steindachneri, leucostomum, postinguinale, scorpioides, albogulare, cruentatum, abaxillare, hirtipes, murrayi, chapalaense, tarascense, magdalense, megacephalum, sonoriense, longifemorale, flavescens, arizonense, durangoense, megacephalum, peguense, vogeli, tristernalis, shiui, thurjii, indi, smithii, pallidipes, tentoria, circumdata, flaviventer, amboinensis, couro, kamaroma, flavomarginata, sinensis, evelynae, galbinifrons, hainanensis, serrata, bourreti, mutica, kami, caspica, rivulata, siebenrocki, ventrimaculata, trijuga, thermalis, edeniana, coronata, indopeninsularis, parkeri, punctularia, diademata, flammigera, pulcherrima, rogerbarbouri, incisa, manni, rubida, perixantha, marmorata, pallida, orbicularis, colchica, eiselti, galloitalica, lanzai, capolongoi, occidentalis, hispanica, fritzjuergenobstii, hellenica, iberica, persica, luteofusca, carolina, major, triunguis, bauri, yucatana, mexicana, ornata, luteola, nelsoni, klauberi, picta, marginata, dorsalis, bellii, scripta, elegans, troostii, hartwegi, taylori, cataspila, venusta, yaquia, hiltoni, nebulosa, ornata, grayi, callirostris, chichiriviche, emolli, dorbignyi, brasiliensis, decussata, angusta, stejnegeri, vicina, malonei, concinna, floridana, suwanniensis, reticularia, chrysea, miaria, pseudogeographica, kohnii, ouachitensis, sabinensis, nigrinoda, delticola, terrapin, centrata, tequesta, rhizophorarum, macrospilota, pileata, littoralis, belliana, nogueyi, arachnoides, oblonga, brygooi, signatus, cafer, tentorius, trimeni, verroxii, emys, phayrei, graeca, terrestris, ibera, anamurensis, zarudnyi, nikolskii, armeniaca, hermanni, boettgeri, horsfieldii, kazachstanica, rustamovi, Class Reptilia, Family Bataguridae, Family Carettochelyidae, Family Chelidae, Family Cheloniidae, Family Chelydridae, Family Dermatemydidae, Family Dermochelyidae, Family Emydidae, Family Kinosternidae, Family Pelomedusidae, Family Platysternidae, Family Testudinidae, Family Trionychidae, Order Testudines, Phylum Chordata, Subfamily Batagurinae, Subfamily Cyclanorbinae, Subfamily Deirochelyinae, Subfamily Emydinae, Subfamily Geoemydinae, Subfamily Kinosterninae, Subfamily Pelomedusinae, Subfamily Podocneminae, Subfamily Staurotypinae, Subfamily Trionychinae, Suborder Cryptodira, Suborder Pleurodira
