| Dichotomous key of marine turtles |
| 1. |
Large costals are absent on the carapace - Dermochelys coriacea
Large costals are present on the carapace - 2 |
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| 2. |
Six pairs of costals or more pairs are present - Lepidochelys olivacea
Less than six pairs of costals are present - 3
|
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| 3 |
Five pairs of costals are present - Caretta caretta
Four pairs of costals are present - 4
|
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| 4 |
Two pairs of prefrontals are present & all - Eretmochelys imbricata
Costals are overlapped |
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| |
One pair of prefrontals is present & all - Chelonia mydas
Costals are not overlapped  |
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