Crocodiles

are distinguished by their usually large size. From neck to tail, their backs are covered in rows of bony plates, which can give the impression of thorns or teeth. Crocodiles appeared toward the end of the Triassic Period, and they are the closest living relatives to both dinosaurs and birds. Their hearts are divided into four chambers, their brains show a high degree of development, and the musculature of their abdomens is so developed that it resembles the gizzards of birds. The larger species are very dangerous.

OVIPAROUS Most reptiles are oviparous (they lay eggs); however, many species of snakes and lizards are ovoviviparous (they give birth to live offspring).

A Skin with Scales

Reptiles are vertebrates, meaning that they are animals with a spinal column. Their skin is hard, dry, and flaky. Like birds, most reptiles are born from eggs deposited on land. The offspring hatch fully formed without passing through a larval stage The first reptiles appeared during the height of the Carboniferous Period in the Paleozoic Era. During the Mesozoic Era, they evolved and flourished, which is why this period is also known as the age of reptiles. Only 5 of the 23 orders that existed then have living representatives today.«

EMBRIONARY MEMBRANES

They develop two: a protective amnion and a respiratory allantoic! (or fetal vascular) membrane.

SOLOMON ISLAND SKINK

Corucia zebrata turtles

HERMANN'S TORTOISE

Testudo hermanni

APPROXIMATELY

Squamata

BOA CONSTRICTOR

Squamata

APPROXIMATELY

SPECIES OF SNAKES EXIST.

This order constitutes the largest group of living reptiles and includes more than 6,000 species of lizards and snakes. The majority of animals in this order have bodies that are covered with corneous scales. The squamata include three forms of reptiles that are somewhat different from each other: the amphisbaenians, the lizards, and the snakes. It also contains certain extinct forms of reptiles, including pythonomorpha, which had snakelike bodies and lizard-like feet.

BOA CONSTRICTOR

Boa constrictor

They regulate their temperature by taking advantage of different sources of external heat, such as direct sunlight and stones, tree trunks, and patches of ground that have been heated by the sun.

ECTOTHERMIC The body temperature of reptiles depends on the environment—they cannot regulate it internally. This is why higher temperatures increase their vitality.

SKIN

Dry, thick, and impermeable, it protects the body from dehydrating even in very hot, dry climates.

THE TONGUE Large, protractile, and bifid, a reptile's tongue is very short and thick, and it contains the taste organs.

ROSY BOA

Chelonians

The order of the testudines differentiated itself from the rest of the reptile world during the Triassic Period. Today it comprises marine turtles and terrestrial turtles. The species of this order are unique. They are covered with shells that consist of a dorsal carapace and a ventral plastron. These shells are so much a part of these animals that their thoracic vertebrae and ribs are included in them. Since these rigid shells do not allow turtles to expand their chests to breathe, these animals use their abdominal and pectoral muscles like diaphragms.

turtles

HERMANN'S TORTOISE

Testudo hermanni

SKELETON is almost entirely ossified (not cartilaginous).

SPECIES OF TURTLES EXIST.

LUNGS

Since the ribs are fused with the shell, turtles cannot move their ribs to inhale. They use the muscles in the upper part of their legs to produce a pumping motion and inhale air.

SKELETON is almost entirely ossified (not cartilaginous).

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