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Testudinata

Testudinata is commonly known as turtles, and all its members are the oldest reptiles in existence. They are characterized by a very strong shell on their bodies. When attacked, the turtle can retract its head, tail and limbs into the shell. Most turtles are carnivorous. Turtles can usually live on land and in water, and there are also sea turtles that live in the sea for a long time. Turtles are also long-lived animals, and some live for more than a hundred years in the natural environment.

I. Introduction to Testudines

1. Definition and Main Characteristics

  • Taxonomic Placement
    Testudines (also referred to as Chelonia in some classifications) is an order of Reptilia (reptiles) that includes all extant and extinct turtles, tortoises, and terrapins. With around 350 living species, they inhabit freshwater, marine, and terrestrial environments in tropical, temperate, and even high-elevation regions worldwide.

  • Prominent Morphological Features

    • Carapace and Plastron: The most distinctive attribute is the hard shell composed of an upper carapace (formed by expanded ribs and vertebrae) and a lower plastron, often covered by horny scutes or leathery skin.

    • Neck Retraction: Based on how the neck is retracted or bent sideways, turtles are divided into two main suborders: Cryptodira (hidden-necked turtles) and Pleurodira (side-necked turtles).

    • Toothless Jaws: Turtles lack true teeth, instead bearing sharp, horn-like beaks for feeding.

    • Longevity and Growth: Many Testudines species exhibit long lifespans and slow growth rates; some sea turtles and giant tortoises can live for decades or even over a century.

  • Ecological Habits

    • Habitat Range: Includes marine (e.g., sea turtles), freshwater (e.g., softshell turtles, pond turtles), and terrestrial (e.g., tortoises) habitats.

    • Varied Diets: Some are strictly herbivorous (many tortoises), others are omnivorous (certain freshwater turtles), and some are carnivorous (softshells, snapping turtles, leatherback turtles, etc.).

    • Reproduction: All are oviparous, laying eggs on land or sandy beaches. The hatchlings receive no parental care post-hatching.

2. Ecological and Human Significance

  • Role in Food Webs
    Freshwater and marine turtles often act as mid-level predators, scavengers, or algae grazers, helping maintain aquatic ecosystems. Tortoises can be influential herbivores in grasslands and deserts, aiding seed dispersal and soil turnover.

  • Economic and Cultural Value

    • Fisheries and Medicinal Use: Some turtles (like softshell turtles, certain freshwater species) are harvested for food or used in traditional medicine.

    • Pets and Ornamental Species: Many species (e.g., red-eared sliders, Asian box turtles, sulcata tortoises) appear in the pet trade, which can raise concerns regarding invasive species or illegal trafficking.

    • Cultural Symbol: Turtles often symbolize longevity and resilience in various cultures, while sea turtles hold important roles in marine ecotourism and folklore.


II. Evolutionary History

  1. Fossil Record and Early Origins

  • Turtles emerged as early as the Late Triassic (over 200 million years ago), as evidenced by fossils like Odontochelys, which had partly formed shells.

  • By the Jurassic, stem turtles like Proganochelys displayed a more complete shell, although retaining some primitive traits. These fossils illustrate the evolutionary path from thickened ribs and dermal plates to the robust shells we see today.

  1. Division into Hidden-necked and Side-necked Turtles

  • The difference in neck retraction strategy leads to two main lineages:

    • Cryptodira: The majority of modern turtles (sea turtles, tortoises, freshwater turtles) retract their necks straight back into the shell.

    • Pleurodira: Fewer species found mainly in the Southern Hemisphere (snake-necked and side-necked turtles) bend their necks sideways to tuck it under the shell margin.

  • This divergence dates back to the Late Jurassic or mid-Cretaceous, with each lineage evolving extensively on different continents.

  1. Modern Diversity and Distribution

  • Through subsequent geological periods, tectonic shifts and climatic changes allowed turtles to expand into marine, riverine, wetland, and desert habitats.

  • Human activities (hunting, habitat destruction, global trade) and climatic changes now pose significant threats to many turtle populations, placing numerous species under endangered or protected status.


III. Major Classification Table of Testudines

A. Suborder Pleurodira (Side-necked Turtles)

FamilyRepresentative GenusExample SpeciesDistribution & Notes
Chelidae (Austro-American Side-necked Turtles)Chelus (Mata mata), Chelodina (Long-necked turtles), etc.Mata mata (Chelus fimbriata), Australian long-necked turtle (Chelodina longicollis), etc.Found in South America and Australia; notably long necks that fold sideways, some have very unusual appearances.
Pelomedusidae (Afro-American Sideneck Turtles)Pelomedusa (African Helmeted Turtle), Pelusios, etc.African helmeted turtle (Pelomedusa subrufa), etc.Mostly in Africa, parts of South America and Madagascar; neck folds to the side rather than fully retracting.
Podocnemididae (River Turtles)Podocnemis (South American River Turtles), etc.Yellow-spotted river turtle (Podocnemis unifilis), etc.Large, riverine turtles found in South American basins and Madagascar; many species are big-bodied and aquatic.

B. Suborder Cryptodira (Hidden-necked Turtles)

FamilyRepresentative GenusExample SpeciesDistribution & Notes
Cheloniidae (Sea Turtles)Chelonia (Green Sea Turtle), Eretmochelys (Hawksbill), Caretta (Loggerhead), etc.Green sea turtle (Chelonia mydas), Hawksbill (Eretmochelys imbricata), Loggerhead (Caretta caretta), etc.Occupy tropical/subtropical oceans worldwide; threatened by fisheries bycatch, marine pollution, coastal habitat loss.
Dermochelyidae (Leatherback Sea Turtle)Dermochelys (Leatherback Turtle)Leatherback turtle (Dermochelys coriacea)The largest sea turtle; unique leathery shell instead of horny scutes; jellyfish specialist; also endangered globally.
Chelydridae (Snapping Turtles)Macrochelys (Alligator Snapping Turtle), Chelydra (Common Snapping Turtle)Alligator snapping turtle (Macrochelys temminckii), Common snapping turtle (Chelydra serpentina)Native to North America; large freshwater turtles with strong bites and aggressive temperament.
Trionychidae (Softshell Turtles)Pelodiscus (Chinese Softshell), Apalone (American Softshell), Rafetus, etc.Chinese softshell turtle (Pelodiscus sinensis), Spiny softshell (Apalone spinifera), etc.Soft, leathery carapace; well-adapted for ambush hunting and burrowing; found in Asia, Africa, North America.
Emydidae (Pond and Box Turtles)Trachemys (Sliders), Emys (European Pond Turtle), Graptemys (Map Turtles), etc.Red-eared slider (Trachemys scripta elegans), European pond turtle (Emys orbicularis), etc.Mostly in North America and parts of Europe/North Africa/Asia; popular in pet trade. Red-eared sliders can be invasive.
Testudinidae (Tortoises)Testudo (Mediterranean tortoises), Geochelone (Giant tortoises), Gopherus (Gopher tortoises), etc.Sulcata tortoise (Centrochelys sulcata), Galápagos tortoise (Chelonoidis niger), etc.Terrestrial species with strong, columnar limbs; found in arid/semi-arid regions worldwide; some are extremely long-lived.
Geoemydidae (Leaf and Pond Turtles)Mauremys (Asian Pond Turtle), Cuora (Asian Box Turtle), Sacalia, Chinemys, etc.Asian leaf turtle (Mauremys mutica), Yellow-margined box turtle (Cuora flavomarginata), etc.Mostly Asian distribution; many species threatened by habitat loss and over-collection for food or medicine.
Dermatemydidae (Mesoamerican River Turtle)Dermatemys (Giant River Turtle)Central American river turtle (Dermatemys mawii)Endemic to river systems in Central America; extremely endangered due to limited distribution and exploitation.

IV. Conclusion

  1. Multiple Evolutionary Events Shaping Global Distribution

  • The fossil record of turtles dates back to the Late Triassic, revealing the earliest shells and subsequent division into the hidden-neck (Cryptodira) and side-neck (Pleurodira) lineages.

  • These lineages diversified into marine, freshwater, and terrestrial habitats on different continents across geological time.

  1. Ecology and Human Interaction

  • Turtles play vital roles in marine and freshwater ecosystems (e.g., sea turtles controlling jellyfish populations, softshells scavenging organic matter). Tortoises are key herbivores in deserts/grasslands.

  • Overexploitation (hunting, trade), habitat loss, and pollution threaten many turtle species, making conservation efforts vital.

  1. Conservation and the Future

  • Many sea turtles and numerous freshwater/terrestrial turtles are listed under international conventions or on endangered species lists. Conservation efforts include protected areas, nesting beach patrols, captive breeding, and release programs.

  • Ongoing genetic and phylogenetic research refines our understanding of turtle relationships, guiding taxonomy, conservation priorities, and strategies.


Summary

This overview analyzes the historical evolution, main classifications, and roles of the order Testudines in ecology and human society. If you need to get more detailed information on the morphology, distribution, and conservation status of specific species, you can refer to local herpetological records, reports from wildlife conservation organizations, and the latest molecular systematics research. I hope this "Classification of Testudines" can provide you with easy-to-understand and informative popular science.

Testudines Squamata Crocodilia Lizardia
Caretta

Caretta

Caretta,Loggerhead turtle, loggerhead sea turtle, loggerhead sea turtle, loggerhead sea turtle, loggerhead sea turtle, loggerhead sea turtle

Features:The back of the head is brownish red, the sides of the head are light brown, the belly and jaws are yellow. The back of the neck is dark. The eyes are large, the carapace is brownish red, and the backs of the limbs are also brownish red.

The loggerhead sea turtle is a single species worldwide that spends most of its life in the open ocean and shallow waters. It rarely comes ashore, except for brief nesting and egg-laying by females. Hatchlings live in floating clumps of Sargassum. Adults and juveniles live on the continental shelf a...

Sacalia bealei

Sacalia bealei

Sacalia bealei,Beal's eyed turtle,Spotted turtle

Features:There is usually a pair of eye-shaped spots on the back of the head, with 1-3 black spots in the center.

The spotted turtle is aquatic, mainly living in streams with slow and clear water flow and gravel bottom in hilly areas below 400 meters above sea level. It is timid and will retract its head, tail and limbs into its shell or run around aimlessly when disturbed. It likes to bask in the sun, and the...

Geoemyda spengleri

Geoemyda spengleri

Geoemyda spengleri,Black-breatsed Leaf Turtle,Golden turtle, twelve-horned turtle, maple leaf turtle, black-breasted leaf turtle, twelve-winged turtle

Features:They eat small amounts and grow slowly.

The ground tortoise lives in the shaded and moist areas near streams in the mountain jungle at an altitude of about 700 meters, and is also often found in streams. It is terrestrial or semi-aquatic and cannot enter deep waters. The understory trees, vines and bamboos in its habitat are abundant, and...

Cuora

Cuora

Cuora,Broken plate turtle, snake turtle, snake-claw turtle, Asian box turtle

Features:The plastron can be completely closed to the carapace

The genus Cuora (scientific name: Cuora) is a genus of Testudinata, Testudinidae, commonly known as box turtles. They are distributed in the Yangtze River and all places south of it in my country. Common ones include golden-headed box turtles, yellow-margined box turtles, three-lined box turtles, Yu...

Mauremys mutica

Mauremys mutica

Mauremys mutica,Stone turtle, stone golden coin turtle, water turtle, yellow turtle, fragrant turtle

Features:The individual is medium-sized, flat and oval in shape, with a small head. The back of the head is smooth and scaleless, yellow or yellow-olive in color, and the ventral side of the head and throat are yellow, hence the name.

The yellow-throated water turtle lives in the waters of hilly areas, mountain basins in semi-mountainous areas, and river valleys. Sometimes it also often moves in bushes and rice fields. During the day, it mostly plays and forages in the water. On sunny days, it likes to be on land, and sometimes c...

Mauremys sinensis

Mauremys sinensis

Mauremys sinensis,Chinese Stripe-necked Turtle,Ocadia sinensis Gray,1834,Chinese turtle, spotted turtle, pearl turtle, long-tailed turtle, Taiwan turtle

Features:The head is small, with a tapered snout that protrudes beyond the tip of the beak.

The flower turtle is an aquatic turtle. It is water-loving and has the habit of going ashore to bask in the sun. When the temperature is above 25℃ and the weather is fine and sunny, the flower turtle likes to climb onto the terrace or the shore to bask in the sun. The flower turtle has a wide adapt...

Mauremys nigricans

Mauremys nigricans

Mauremys nigricans,Red-necked pond turtle,Painted turtle, black-necked painted turtle, three-lined turtle, Guangdong grass turtle, black-necked terrapin

Features:They like warmth and are afraid of cold. They have a gentle temperament and will not hurt others on their own initiative.

The black-necked turtle is large in size and lives in streams in subtropical hilly and mountainous forests. The black-necked turtle moves clumsily, crawls slowly, has a gentle temperament, and does not actively hurt people. The black-necked turtle likes warmth and is afraid of cold. It cannot live i...

Cyclemys oldhamii

Cyclemys oldhamii

Cyclemys oldhamii,Snake-catching turtle, snake-catch turtle, snake-killing turtle

Features:Darker body color

The European turtle is a wild animal of the order Testudinata and family Geochelone. In the wild, it often hides near dead trees to look for insects. The juveniles are closer to water turtles, but cannot go into deep water....

Testudo horsfieldii

Testudo horsfieldii

Testudo horsfieldii,Afghan Tortoise Central Asian Tortoise Four-toed Tortoise Horsfield's Tortoise Steppe Tortoise,Land turtle, taspaha, prairie tortoise, land tortoise, turtle

Features:The four-clawed tortoise is the only tortoise that lives in the desert grasslands of my country.

In the Yili River Valley in Xinjiang, China, there is a small creature called "Tasipaka". "Tasipaka" means "stone" and "Paka" means "toad". What kind of animal is this stone-like toad? It is the four-clawed tortoise, which is listed as "critical...

Manouria impressa

Manouria impressa

Manouria impressa,Impressed Tortoise, Kirin tortoise

Features:As the name suggests, the carapace is flat and even concave in the middle, forming a groove with three horizontal lines.

Concave-shelled tortoise lives in tropical and subtropical mountainous areas. Adults live on the banks of mountain streams, and young turtles can climb up to the banks and lie horizontally on tree trunks to bask in the sun. They live far away from water and have a narrow distribution area. They feed...

Indotestudo elongata

Indotestudo elongata

Indotestudo elongata,Elongated Tortoise,Yellow elephant turtle, pillow turtle, dry turtle, Burma land, dragon claw turtle and so on

Features:Big eyes, short neck, high back and long nails.

Burmese tortoises are subtropical terrestrial tortoises, living in mountains, hills and bush forests, active at night, warm and afraid of cold. Docile, spiritual, mainly herbivorous, but also eat animal food, can feed melons, fruits, vegetables, lean meat, etc., like to eat tomatoes. The optimum te...

Platysternon megacephalum

Platysternon megacephalum

Platysternon megacephalum,Big-headed Turtle,Hawk-billed turtle, big-headed flat-chested turtle, eagle turtle, etc

Features:The body is flat, the head is large, and it cannot be shrunk into the shell.

Flat chest turtle like Yin fear of high temperature, fierce temperament, rock climbing and tree climbing ability is very strong. It lives mainly in the clear streams of the mountains. It also appears in swamps, pools, rivers and fields, generally at night, can climb stone walls or trees, and can cli...

Testudines

Testudines

Tortoise, golden turtle, grass turtle, mud turtle, mountain turtle, black turtle, flower turtle

Features:Turtles have a long lifespan and their shells can be boiled into turtle glue, which is a commonly used Chinese medicine.

In a broad sense, turtle refers to the general term for animals of the order Testudinata, and in a narrow sense, refers to species under the family Testudinidae. It is an ancient reptile that still exists. Generally, turtles are also called tortoises. Turtles are reptiles that evolved with shells as...

Aldabrachelys gigantea

Aldabrachelys gigantea

Aldabra giant tortoise, Seychelles giant tortoise, Darding giant tortoise, Arnold's giant tortoise

Features:The second largest tortoise in the world.

This tortoise was discovered by humans more than 400 years ago. At that time, people did not realize that it was a long-lived animal. It was not until the most famous Aldabra tortoise, Advita, appeared that people began to study the age of tortoises. The Sanskrit meaning o...

Centrochelys sulcata

Centrochelys sulcata

Sulcata tortoise, Sulcata tortoise, African spurred tortoise, spurred tortoise, hairy-clawed tortoise

Features:The third largest tortoise in the world and the largest tortoise on the African continent.

The Sulcata tortoise is a tortoise reptile that lives on land. It originally belonged to the family Testudinidae and the genus Testudinidae, so its Chinese name includes the Sulcata tortoise and the Sulcata tortoise. It was finally classified into the genus Centrochelys and is the only surviving spe...

Chelonia mydas

Chelonia mydas

green sea turtle,Green turtle, blue turtle, stone turtle, tsio̍h-ku,ku-piah,ku-phi̍ah

Features:One of the largest hard-shelled sea turtles.

Turtles are one of the oldest animals on Earth. These creatures have existed in the world for more than 200 million years, but their living environment is being threatened by the growing development of humans. Therefore, in 2000, the American Turtle Rescue Organization launched an international fest...