The order Testudines encompasses all turtles and tortoises, remarkable reptiles celebrated for their distinctive shells, slow metabolisms, and impressive lifespans. Their fossil record stretches back over 200 million years, making them one of the most ancient groups of reptiles, well before the rise of snakes and lizards. As fully encased in bony armor, they possess unsurpassed protective adaptations among vertebrates. Testudines thrive in diverse habitats worldwide, from oceans and freshwater to deserts, showcasing extraordinary evolutionary success and resilience.
The two main groups within Testudines are turtles and tortoises.
Testudines first appeared over 200 million years ago.
What are Testudines?
Testudines are defined by a bony shell that encloses the body.
Testudines are more closely related to lizards than to birds.
Testudines inhabit marine, freshwater, and terrestrial environments.
Only female Testudines lay eggs.
Source Material
Author: U.S. Fish and Wildlife Service
Document: Testudines: The Turtle and Tortoise Order
Date Published: 2023
Testudines are an order of reptiles distinguished by a bony shell that provides extraordinary protection. This shell is formed by the fusion of ribs, vertebrae, and dermal bone, creating a rigid armor that encloses both the dorsal (carapace) and ventral (plastron) parts of the body. They first appeared more than 200 million years ago and have remained largely unchanged since, making them one of the most ancient reptile groups. Testudines include turtles (mainly aquatic or semi-aquatic) and tortoises (primarily land-dwelling), and they inhabit diverse environments from oceans to freshwater and terrestrial ecosystems worldwide. Only female Testudines lay eggs, often in carefully excavated nests.
- A unique, fused bony shell defines Testudines, providing lifelong protection.
- The order dates back over 200 million years, making them living fossils.
- Testudines include both aquatic/semi-aquatic turtles and land-adapted tortoises.
- They occupy marine, freshwater, and terrestrial habitats globally.
- Reproduction is oviparous, with females laying eggs in nests.
Famous Testudines include the leatherback sea turtle, Galápagos giant tortoise, and red-eared slider.
Adult Testudines lack teeth; they use keratinized beaks.
Tortoises have high-domed shells and stout, elephantine legs.
Testudines are monophyletic, meaning all members share a common ancestor.
Source Material
Author: Britannica
Document: Testudines (Turtles) - Facts, Characteristics & Examples
Date Published: 2024
Source Material
Author: University of Wisconsin-La Crosse
Document: Turtle Biology
Date Published: 2009
Testudines are reptiles with a distinctive bony shell formed by fused ribs and vertebrae, providing exceptional protection. This order includes both turtles and tortoises: turtles are generally aquatic or semi-aquatic, while tortoises are primarily land-dwellers. Testudines first appeared over 200 million years ago, making them one of the oldest reptile groups. They inhabit marine, freshwater, and terrestrial environments worldwide. Unlike many reptiles, adult Testudines lack teeth and use keratinized beaks for feeding. Only females lay eggs, which are buried in nests. Tortoises differ from other Testudines by having high-domed shells and sturdy, elephant-like legs adapted for terrestrial life. The order Testudines is monophyletic, meaning all members share a common evolutionary ancestor.
- Unique bony shell: fused ribs/vertebrae form protective armor.
- Includes both aquatic/semi-aquatic turtles and terrestrial tortoises.
- Among the oldest reptiles: >200 million years old.
- Found in marine, freshwater, and land habitats globally.
- Toothless adults use beak; only females lay eggs.
- Tortoises = high-domed shells + sturdy legs for land.
- Testudines = monophyletic (single evolutionary lineage).
Testudines include sea turtles, box turtles, and Galápagos tortoises.
Testudines first appeared during the Triassic period, over 200 million years ago.
Testudines occupy marine, freshwater, and terrestrial environments.
Testudines possess a unique shell fused to their spine and ribs.
Tortoises have a high-domed shell and stout legs, unlike aquatic turtles.
Testudines lack teeth and instead use a beak for feeding.
Testudines are more closely related to lizards than to crocodiles.
Source Material
Author: National Geographic
Document: Testudines - Turtle and Tortoise Facts
Date Published: 2024
Examples of Turtles
Leatherback sea turtles, green sea turtles, and red-eared sliders are all turtles.
Most turtles spend the majority of their lives in aquatic or semi-aquatic environments.
Turtles possess flatter shells and webbed limbs, unlike tortoises.
The shell grows along with the turtle throughout its life.
Turtles inhabit oceans, rivers, and swamps, among other habitats.
Marine turtles sense Earth's magnetic field to navigate vast distances.
Source Material
Author: National Geographic
Document: Turtles: Facts, Types & Pictures
Date Published: 2023
"Turtles" are Testudines characterized by streamlined shells and adaptations for aquatic life, such as webbed feet or flippers. They can be found in marine, freshwater, and some terrestrial environments. Notable examples include sea turtles like the leatherback and green sea turtle, and freshwater species like the red-eared slider. Turtle shells grow with the animal, providing protection and buoyancy. Marine turtles exhibit remarkable migratory abilities, often navigating using Earth's magnetic fields. Today, many turtle species face threats from habitat loss and pollution.
- Streamlined shells and webbed limbs adapt turtles for swimming.
- Found in oceans, rivers, lakes, and some wetlands.
- Examples: Leatherback sea turtle, green sea turtle, red-eared slider.
- Shells grow as they mature; provide protection and aid buoyancy.
- Marine turtles use geomagnetic cues for long-distance migration.
- Conservation concerns include habitat destruction and pollution.
Leatherback sea turtle, red-eared slider, and painted turtle are well-known turtles.
Aquatic turtles have webbed feet and flatter, more streamlined shells.
Most turtles are found in freshwater, marine, or semi-aquatic environments.
Turtle shells grow along with the turtle over its lifespan.
Green sea turtle, snapping turtle, and box turtle are all turtles.
Most turtles use sharp-edged beaks to grasp and cut food.
Examples of Tortoises
Galápagos, Russian, and Aldabra are all tortoises.
Tortoises are primarily terrestrial.
Tortoises have stout legs, high-domed shells, and are mostly herbivores.
Tortoises are known for their exceptional longevity.
Tortoises inhabit deserts, grasslands, and scrub forests.
Tortoises retract their head and limbs into their strong shell for protection.
Tortoises are terrestrial reptiles within Testudines, distinguished by their high-domed shells and robust, elephantine legs adapted for walking on land. They are primarily herbivorous, consuming a diet of grasses, leaves, and fruits. Tortoises inhabit diverse land environments, including deserts and grasslands, and are renowned for their exceptional longevity, with some living over 100 years. They protect themselves by retracting their heads and limbs into their durable shells. Notable examples include the Galápagos giant tortoise, Aldabra giant tortoise, and Russian tortoise.
- Tortoises = land-dwelling Testudines with heavy, domed shells.
- Strong, columnar legs support movement on rough terrain.
- Mostly herbivorous: eat plants, fruits, and vegetables.
- Found in deserts, grasslands, and forests worldwide.
- Known for extreme longevity; some exceed a century in age.
- Defensive strategy: retract head/limbs into shell.
- Examples: Galápagos giant tortoise, Aldabra tortoise, Russian tortoise.
Aldabra giant tortoise, Galápagos tortoise, and Russian tortoise are all tortoises.
Tortoises are primarily terrestrial animals.
Tortoises have a high-domed shell and strong, columnar legs.
Most tortoises have an exceptionally long lifespan.
Tortoises are typically found in deserts, grasslands, and shrublands.
Tortoises protect themselves by retracting their head and limbs into their shell.
The order Testudines, comprising turtles and tortoises, is distinguished by a unique bony shell that provides exceptional protection and has contributed to their evolutionary success over more than 200 million years. Turtles are generally adapted to aquatic or semi-aquatic lifestyles, featuring streamlined shells and webbed limbs, while tortoises are primarily terrestrial with robust, high-domed shells and sturdy legs. Both groups exhibit fascinating adaptations for survival, reproduction, and longevity, making them among the most remarkable and enduring reptiles on Earth.
- Testudines are defined by their fused bony shells and long evolutionary history.
- Turtles are mostly aquatic/semi-aquatic; tortoises are land-dwellers with specialized limbs.
- Both groups display extraordinary adaptations for protection, locomotion, and longevity.
All Testudines have a shell formed by fused bones.
Testudines are most closely related to lizards and snakes.
Turtles commonly inhabit oceans, rivers, and lakes.
Tortoises are terrestrial turtles within the order Testudines.
Most adult Testudines are either herbivores or omnivores, depending on the species.
Galápagos giant tortoise and Russian tortoise are true tortoises.
All Testudines lay eggs on land; aquatic species come ashore to nest.
Red-eared slider and painted turtle are freshwater species.
Turtles and tortoises belong to the order Testudines.