amniote vertebrates that are classified under the reptile class

The sex of developing crocodilians is determined by the incubation temperature of the eggs. This means crocodilians do not have genetic sex determination, but instead have a form of environmental sex determination which is based upon the temperature embryos are subjected to early in their development.

Crocodile embryos do not have sex chromosomes, and unlike humans sex is not determined genetically. Sex is determined by temperature, with males produced at around 31.6 °C, and females produced at slightly lower and higher temperatures. The average incubation period is around 80 days, and also is dependent upon temperature.

Nile crocodiles have temperature-dependent sex determination, which means the sex of their hatchlings is determined not by genetics, but by the average temperature during the middle third of their incubation period.

If the temperature inside the nest is below 31.7 °C (89.1 °F), or above 34.5 °C (94.1 °F), the offspring will be female. Males can only be born if the temperature is within that narrow 5-degree range.

its temperature dependent

A sex chromosome helps in the determination of sex in an organism.