chelonians

Chelonians are reptiles belonging to the order Testudines, characterized by a bony or cartilaginous shell developed from their ribs and acting as a shield. This shell is typically divided into a dorsal carapace and a ventral plastron. Chelonians are found on every continent except Antarctica, inhabiting a wide range of environments including oceans, freshwater bodies, and terrestrial habitats. The order Testudines includes turtles, tortoises, and terrapins, though these distinctions are often based on habitat and common usage rather than strict taxonomic separation.

These animals are ectothermic, meaning they rely on external sources of heat to regulate their body temperature. Their diets vary significantly depending on the species, ranging from herbivorous to carnivorous or omnivorous. Chelonians reproduce sexually, and most species lay eggs, which are typically buried in nests dug in soil or sand. The incubation period and sex determination can be influenced by environmental factors, particularly temperature.

Chelonians have a long evolutionary history, with fossil evidence dating back over 200 million years, making them one of the oldest reptile groups. Many species are long-lived, with some individuals surviving for over a century in captivity and the wild. Unfortunately, many chelonian populations are threatened by habitat loss, pollution, climate change, and the pet trade, leading to numerous species being listed as endangered or critically endangered. Conservation efforts are ongoing to protect these ancient and diverse reptiles.