1. Members of the order Chelonia; reptiles with a bony or leathery shell covering the body, including turtles, tortoises, and terrapins.
Usage: Plural form; used in zoology and general contexts.; Includes both aquatic and terrestrial species.

Examples

• Chelonians are among the oldest living reptiles, with fossils dating back over 200 million years.
• The museum's exhibit featured chelonians from around the world, including sea turtles and giant tortoises.
• Scientists study chelonians to understand how they adapt to different environments.
• Many chelonians are endangered due to habitat loss and illegal trade.
• Chelonians have remained relatively unchanged in form since the age of dinosaurs.