# data[].attributes.attachment_link.title
Learn About the Evolution of Dogs 🐶 | Weird But True! | S1 E4 | Full Episode | @natgeokids​

# data[].attributes.attachment_link.title
The Amazing History of Dogs | Reading Passage Grade 4, 5, 6 | Scholastic Storyworks Magazine

# data[].attributes.attachment_link.description
For thousands of years, dogs have been by our sides. But where did it all begin?

# data[].attributes.attachment_link.authors[].name
The Editors of Encyclopaedia Britannica • Edit History

# data[].attributes.attachment_link.description
archosaur, (subclass Archosauria), any of various reptiles, including all crocodiles and birds and all descendants of their most recent common ancestor. Archosaurs (“ruling reptiles”) are members of a subclass that also includes the dinosaurs, the pterosaurs (flying reptiles), and several groups o…

# data[].attributes.attachment_link.title
Evolution of the sensory systems in archosaurs / Curr. Biol., April 29, 2021 (Vol. 31, Issue 12)

# data[].attributes.attachment_link.description
Belonging to the same group as birds and dinosaurs, today’s modern day crocodiles include 24 existing species.

# data[].attributes.attachment_link.description
Modern Day Velociraptor? (Link to our research photos and video here!) Meet the red-legged seriema, Cariama cristata. This modern South American bird is the only surviving cousin to the famed “terror birds” like Phorushacos and Titanis, apex predators that roamed South America as recently as 2 million years ago. It

# data[].attributes.attachment_link.readable_text
Our "Species of the Week" series highlights the flagship species of each of the 844 unique ecoregions contained within Earth's bioregions.
Off the northeast coast of Australia lies one of the oldest tropical rainforests on our planet. Years of seclusion have kept many primitive species of plants and animals flourishing, some so ancient in appearance they seem to take us back to the time of the dinosaurs.

Standing over 1.9 meters (6 feet) tall and weighing up to 85 kilograms (187 pounds), the southern cassowary is a large, flightless bird. Bristly, black feathers cover its body up to a long neck that turns dark indigo and then suddenly, bright blue around its face, expressive brown eyes, and elongated, stony bill. Two red wattles hanging down around its throat give it a bit of a turkey feel, but it is the massive, horn-like casque sitting atop its head that makes this cassowary look positively prehistoric.

Thick, three-toed feet with 4-inch talons and a dagger-like inner claw are also what give these birds the nickname of "living dinosaurs." Bearing an uncanny resemblance to velociraptors, scientists say the birds are one of the most direct relatives to prehistoric creatures, still thriving after 80 million years. Their strong feet and legs allow them to jump up to five feet high and run up to 30 miles per hour. However, this power is used to mostly defend themselves or their nests and babies. Southern cassowaries are mostly solitary birds, but that all changes during the breeding season.

In late winter or early spring, thunderous calls are heard throughout the jungle. Adult females are larger than males and will mate with several partners, laying a clutch of three to four eggs with each. Southern cassowary eggs are a vivid green color, matching the ground nest the males have built out of the surrounding vegetation. Males are in charge of incubating the eggs and raising the young. Fathers teach juvenile cassowaries how to forage and they will become independent around nine months of age.

These large birds are predominantly frugivorous and play an important role in dispersing forest . Southern cassowaries eat the fruit that has fallen to the jungle floor and the seeds within that fruit are digested and spread throughout the region by the cassowary's feces. This keeps the biodiversity of the forest blooming at a higher rate, a found that the seeds of a rare Australian tree showed increased germination from 4% to 92% after passing through the digestive tract of a southern cassowary.

More than 80% of the coastal lowland rainforest in Australia has been cleared over the past century, so although currently not considered endangered, protecting the southern cassowary plays a vital role in preserving this ecosystem that has been around for hundreds of thousands of years.

Click the button below to discover how you can help protect the remaining rainforest home of this amazing creature!

Help Protect the Daintree Rainforest

# data[].attributes.attachment_link.title
Southern cassowary: 'living dinosaur' gardeners of the Daintree Rainforest | One Earth

# data[].attributes.attachment_link.description
With a large caste on its head and 4-inch talons, the southern cassowary is a "living dinosaur" and vital seed disperser of one of the oldest tropical ecosystems on our planet.

# data[].attributes.attachment_link.title
Shark evolution: a 450 million year timeline

# data[].attributes.attachment_link.description
Evolving before trees and weathering five mass extinctions, sharks are true survivors.

# data[].attributes.attachment_link.readable_text
Most scientists believe that sharks came into existence around 400 million years ago. That's 200 million years before the dinosaurs!
It's thought that they descended from a small leaf-shaped fish that had no eyes, fins or bones. These fish then evolved into the 2 main groups of fish seen today. Bony fish (Osteichthyes) and cartilaginous fish (Chondrichthyes - the sharks, skates, rays and ).

The fossil record documents over 3,000 shark species. Yet it's likely many more existed but disappeared without trace. After death, a shark's skeleton rots away due to it being made of cartilage instead of bone. So, usually the only remains they leave behind are their teeth, dermal denticles and fin spines. But we can tell a lot from a single tooth. From this, scientists can tell what the shark fed on and even identify the species it belonged to.

Shark fossil records are abundant and diverse. They show that some species, living over 150 million years ago, were identical to those existing today. One of the earliest known species was the Cladoselache. Like many other early sharks their mouth was located at the front of their snout. A trait that the Megamouth Shark, Frilled Shark, Angelshark and devil rays still have today.

One fossil tooth, belonging to a Megalodon Shark, measures a massive 17cm in length. Indicating that this enormous predator was as long as two buses! The massive Megalodon is an ancestor of today's infamous White Shark.

Sharks have always dominated the top of the marine food chain. For a brief time they were joined by other huge marine reptiles, such as Mosasaurs and Plesiosaurs. Yet sharks are the only group to have survived to modern day.

The entire history of our planet can be broken down into 4 stages:

THE PRECAMBRIAN SUPEREON

This began with the evolution of the Earth 4.6 billion years ago. It's categorised by a complete lack of animal life.

THE PALEOZOIC ERA (545-250 million years ago)

This period saw the evolution of life from single celled organisms to bony fish and sharks. A rapid increase in the number of shark species occurred during this time. In an age called the Carboniferous some sharks evolved weird and crazy appendages. None of the sharks that lived in the Paleozoic are around today. But all modern day sharks evolved from them.

THE MESOZOIC ERA (250-65 million years ago)

Some of the sharks from the Paleozoic period survived into the Mesozoic. During the Jurassic period there was another rapid increase in the number of shark species. This is when all modern shark families and the skates and rays first evolved. The end of the Mesozoic saw the fall of the great marine reptiles.

THE CENOZOIC ERA (65 million years ago - present day)

Modern sharks and toothed whales (such as the Killer Whale) continued to flourish at the top of the food chain. Hammerheads were the last of the modern shark families to evolve, and did so in the Cenozoic. Their evolution date is estimated at between 50 and 35 million years ago.

Despite surviving 5 mass extinctions, today, many shark species are threatened with extinction. Pressure form damaging human activities means that sharks are now one of the most threatened groups of animals on the planet.

Find out what you can do to help by visiting our Get Involved page.

Love Discovering Sharks?

We're passionate about providing great content for our fellow shark enthusiasts! If you'd like to see more content like this you can always help us by making a donation below. Every penny counts and we'd really appreciate your support.

You can set up a regular, or one-off, donation in support of all our work. Your gift to sharks will then be allocated where it's needed the most. Every penny helps.

Latest

Related

Most read

Conservation groups are calling for answers and action in relation to the landing of Endangered Giant Devil Rays in Kelibia, Tunisia, in contravention of international agreements to protect the species.

# data[].attributes.attachment_link.description
Most scientists believe that sharks came into existence around 400 million years ago. That's 200 million years before the dinosaurs! It's thought that they descended from a small leaf-shaped fish that had no eyes, fins or bones. These fish then evolved into the 2 main groups of fish seen today.

# data[].attributes.body
Understanding Chelicerates

Chelicerates (Chelicerata) are a type of arthropod, which is a group of animals that includes harvestmen, scorpions, mites, spiders, horseshoe crabs, sea spiders, and ticks. There are about 77,000 different kinds of chelicerates alive today. Chelicerates have two main body sections and six pairs of legs. Four pairs of these legs are used for walking, while the other two pairs, called chelicerae and pedipalps, are used for eating. Chelicerates do not have mandibles (jaws) or antennae (feelers).

Chelicerates are very old animals that first appeared around 500 million years ago. Some of the earliest chelicerates were giant water scorpions, which were the biggest arthropods ever, growing up to 3 meters long! The closest living relatives to these giant water scorpions are horseshoe crabs.

In the past, chelicerates were mostly hunters, but today they have developed many different ways to find food. Some chelicerates eat plants (herbivores), some eat dead matter (detritivores), some are hunters (predators), some live off other animals (parasites), and some eat leftovers (scavengers).

# data[].attributes.attachment_link.title
Sea scorpion and spider | The failures and successes of chelicerate | Evolution Story

# data[].attributes.attachment_link.readable_text
Evolution Of Saber-toothed Cats

Smilodon

Gorgonops

WMNH paleontologists research the Pleistocene time period. The saber-tooth cats that we find is called Homotherium. Compared to other saber-toothed cats like Smilodon, they had shorter canines and were smaller in size.

Homotherium

# data[].attributes.attachment_link.description
Evolution Of Saber-toothed Cats Smilodon Gorgonops WMNH paleontologists research the Pleistocene time period. The saber-tooth cats that we find is called Homotherium. Compared to other saber-toothed cats like Smilodon, they had shorter canines and were smaller in size. Homotherium

# data[].attributes.attachment_link.readable_text
Saber-toothed cats ( Smilodon fatalis), also known as the saber-toothed tigers or simply smilodons, are some of the most iconic ice age animals. Their claims to fame are their oversized canine teeth, which could reach up to seven to eight inches (17-20 centimeters) long! These big cats lived during the Pleistocene epoch, appearing in the fossil record about 800,000 years ago. Although they are not the only saber-toothed carnivore to live during that period, they are certainly the best-known.

Saber-toothed cats may be known as tigers or lions, but names can be deceiving! These cats are actually not directly related to modern tigers or lions. Rather, they were a unique group of animals, standing up to three feet (1 m) tall at the shoulder, 5.5 feet (1.7 m) in length, and up to 750 pounds (340 kg) in weight. They would have been somewhat similar to lions, though shorter and almost twice as heavy.

Despite the size difference, saber-toothed cats likely had some things in common with lions. To begin with, they had similar throat bones as lions, meaning they could roar. They may have also lived in packs. Some depictions show this cat as a solitary hunter, like modern tigers, but fossil evidence suggests something different. Saber-toothed cat skeletons with diseases like arthritis or healed injuries have been found. If these cats hunted and lived alone, they would not have survived injuries as they would have not been able to hunt for food. However, if they lived in a pack, where other animals could share food with the injured animal, an injury did not necessarily imply a death sentence. Perhaps the movie Ice Age got this right!

When the saber-toothed cat did hunt, it had a style all its own. Unlike modern big cats, who have long legs and long tails used for balance when running, the saber-toothed cat was not very good at chasing-down prey. Its heavy, bulky body, short legs, and bobbed tail made it better suited for ambush attacks. It would use its powerful, front legs to grab and hold prey so that it could use its formidable saber-like teeth, which were serrated along the front and back edges like a steak knife. The saber-toothed cat would slash at its prey's belly or throat before retreating and waiting for the unlucky animal to die. However, it would likely not have attacked its prey's back or neck, as the strong muscles in this area of the body could break the cat's teeth. The saber-toothed cat mostly hunted the large, slow-moving animals that were plentiful at the time, like sloths, bison, and even young mammoths and mastodons.

This ambush-hunting style worked well and helped saber-toothed cats to survive throughout the Americas. They spread from coast to coast, from southern Canada all the way to Peru. They even lived here at White Sands! Keep in mind that back then the sand dunes did not exist, and the Tularosa Basin was home to an enormous lake called Lake Otero. This lake attracted a number of ice age mammals, including sloths, mammoths, camels, and, of course, saber-toothed cats.

These cats were tenacious and adaptable animals, thriving for hundreds of thousands of years before their time finally came to an end. Saber-toothed cats went extinct between 8,000 and 10,000 years ago, as the ice age drew to an end and their prey began to die out. Even so, these formidable hunters certainly left their mark on the world - quite literally here at White Sands, as we have found their footprints! These prints are part of our Pleistocene trackway, a collection of footprints left behind by our ice age inhabitants thousands of years ago.

Learn more: Saber-Toothed Cats

# data[].attributes.attachment_link.title
Saber-Toothed Cats - White Sands National Park (U.S. National Park Service)

# data[].attributes.attachment_link.description
Saber-toothed cats ( Smilodon fatalis), also known as the saber-toothed tigers or simply smilodons, are some of the most iconic ice age animals. Their claims to fame are their oversized canine teeth, which could reach up to seven to eight inches (17-20 centimeters) long!

# data[].attributes.attachment_link.readable_text
Imagine a world in which horses of all colors, shapes, and sizes roamed the world, some barely larger than a small dog. That world no longer exists--but once it was real. Today's horses represent just one tiny twig on an immense family tree that spans millions of years. All the other branches of the horse family, known as Equidae, are now extinct. The earliest known horses evolved 55 million years ago and for much of this time, multiple horse species lived at the same time, often side by side, as seen in this diorama.

Ancient Horses

Some 10 million years ago, up to a dozen species of horses roamed the Great Plains of North America. These relatives of the modern horse came in many shapes and sizes. Some lived in the forest, while others preferred open grassland.

Here, two large Dinohippus horses can be seen grazing on grass, much like horses today. But unlike modern horses, a three-toed Hypohippus tiptoes through the forest, nibbling on leaves. A small, three-toed Nannippus, shown here eating shrubs, ate both grass and leaves.

In the background are several other large mammals alive at that time, including Procamelus, a camel relative; a herd of Dinohippus horses; Gomphotherium, a distant relative of true elephants; and Teleoceras, a hornless rhinoceros.

A Brief History of Horses

By 55 million years ago, the first members of the horse family, the dog-sized Hyracotherium, were scampering through the forests that covered North America. For more than half their history, most horses remained small, forest browsers. But changing climate conditions allowed grasslands to expand, and about 20 million years ago, many new species rapidly evolved. Some--but not all--became larger and had the familiar hooves and grazing diets that we associate with horses today. Only these species survived to the present, but in the past, small and large species lived side by side.

Changing Sizes

Horses were once much smaller than they are today. But there was not a steady increase in size over time. Little Nannippus, shown in the diorama at full adult size, was actually smaller than its predecessors.

Dinohippus

The Dinohippus shown grazing on the left is a close relative of horses today. Like modern-day Equus, Dinohippus had single-toed hooves and ate mostly grass. The other extinct species shown in the diorama had three toes and never developed single hooves.

# data[].attributes.attachment_link.description
Imagine a world in which horses of all colors, shapes, and sizes roamed the world, some barely larger than a small dog. That world no longer exists--but once it was real. Today's horses represent just one tiny twig on an immense family tree that spans millions of years.

# data[].attributes.attachment_link.readable_text
Of all the animals, snakes are among the best known but perhaps the most misunderstood. Snakes are characterized by their elongated limbless bodies. They are found in almost every part of the world except the polar regions. Although the greatest species diversity is found in the tropics, snakes occupy a wide range of habitats, from deserts to rainforests, lakes, and oceans. Snakes belong to the class Reptilia, which includes all reptiles. Within Reptilia they are classified with the lizards into the order Squamata. There are roughly 2,500 to 3,000 snake species living today.

Many people associate snakes with a painful and venomous bite. Each year venomous snakes bite thousands of people, many of whom die as a result. However, the danger of snakebite is often overstated. A snake will bite a human only when frightened or threatened. Also, only a small fraction of snake species produce venom. Even in venomous snakes, the venom is an adaptation used mainly to immobilize prey rather than for defense. Snakes can control the amount of venom they inject via a bite. They tend to reserve the limited amount they have available at any one time to help them capture their meals. About 40 percent of snakebites received by humans are "dry"-that is, no venom is injected. However, all snakebites require prompt and appropriate medical attention. In many parts of the world, the production and availability of antivenins-serums that neutralize specific venoms-have greatly reduced the hazards associated with venomous snakebite.

Snakes play a vital role in nature. As predators, for example, some species are important for keeping rodent populations in check. Rodents are seedeaters; overabundant populations can harm plant communities, destroy crops, and ruin stored grains. Attempts by humans to eradicate snakes have resulted in abrupt increases in rodent populations.

Decreased snake populations also bode poorly for animals that depend on these reptiles for their own dinner. Snakes are the natural prey of many animals, including hawks, owls, foxes, and raccoons. Despite their undeserved bad reputations, snakes hold a crucial position in the delicate balance of life. ( See also ecology.)

Much of the snake's internal structure is modified because of the animal's long, slender body shape. The pelvic girdle-the skeletal arch that supports the hind limbs of most vertebrates-is missing in most snakes. Some groups, such as the boas and pythons, have remnants of the pelvic girdle and vestigial limbs-tiny appendages visible on the underside of the animal's body. Many snakes have only one lung; if two lungs are present, one may be greatly reduced in size. Most of the internal organs, such as the liver, kidneys, ovaries, and testes, are very elongated. Snakes lack a urinary bladder; they excrete kidney wastes as solid material.

Although limblessness has some obvious disadvantages for an animal, snakes use their long cylindrical bodies to advantage in certain situations. Snakes can move soundlessly, and the uniformity of their shape allows them to blend into their surroundings in habitats where appendages might make camouflage more difficult. Their slender, flexible bodies also give them access to underground burrows, rock crevices, and tree cavities that are impenetrable for other animals. ( See also adaptation.)

Relationship Between Body Shape and Activity
Although all snakes are cylindrical in shape, the body's weight and length vary considerably across snake species. This variation generally reflects the snake's habitat, feeding style, and behavior. Stout, heavy-bodied species, such as many of the vipers and pit vipers, are slow moving, often sedentary animals that sit and wait for prey. Among such species are the largest living snakes, which belong to the boa and python families. Individual giant anacondas (a type of boa) and reticulated pythons have exceeded 30 feet (9 meters) in length.

Active, terrestrial (land-dwelling) species such as racers and garter snakes are more streamlined. The arboreal (tree-dwelling) species, such as tropical vine snakes, are extremely slender and lightweight so that vegetation can support their weight. The smallest snakes are the burrowing blind snakes, the tiniest of which do not reach 4 inches (10 centimeters) in length.

The snake's vertebral column is unusually long and contains more vertebrae than do the skeletons of any other major group of animals. It consists of precaudal (in front of the tail) vertebrae, to which ribs are attached, and caudal (tail-section) vertebrae, to which ribs are not attached. Snake vertebrae are distinctive in that each vertebra touches its front and back neighbors at five different points. These points fit together and move in relation to one another in a way that allows the vertebrae to swivel easily. As a result, the vertebral column is both flexible and rigid: it easily flexes from side to side and up and down but allows for only minimal twisting on its long axis.

Jaws and Teeth
All snakes are carnivorous, or meat-eating, and consume their prey whole, without chewing. Often, the prey is larger in diameter than the snake's own head and body. Snakes have highly mobile and flexible skulls and jawbones. In addition, in some snakes the back portion of the lower jawbone can be disconnected from the upper jaw so that the mouth can open very wide.

In most species the teeth are curved backward to ensure that prey, which may be alive when swallowed, cannot easily escape. Most snakes have needle-sharp teeth. In the families Viperidae ( vipers and pit vipers, including rattlesnakes) and Elapidae ( cobras and their relatives), the front pair of teeth is modified into fangs that are larger than the other teeth. Some snakes of the family Colubridae have a pair of fangs at the back of the upper jaw.

The teeth are modified in species that do not capture large prey. For example, the soft diet of the egg-eating snakes requires little in the way of teeth; accordingly, snakes of this group have only a few peglike teeth. The burrowing blind snakes, which feed mainly on ants and termites, also have few teeth.

Scales and Molting
The bodies of snakes are covered entirely with scales that arise from the outer skin layer. In most species the scales on the underside of the body are wider than they are long. The scales on the upper part of the body may be quite smooth and shiny, or they may have a ridge, or keel, running lengthwise down the center of each scale. Species may be distinguished by whether they have smooth or keeled scales.

All reptiles shed their scales continually throughout their lifetimes. Snakes characteristically shed the outer layer of skin all at once. Before shedding-which is also called molting-the snake's eyes turn milky blue in color. The old layer of scales begins to loosen at the front end of the snake's body, along its lips. The animal often hastens the molting process by rubbing its head against a rough object, such as a rock, to break the skin loose. The snake then crawls completely out of its skin, leaving the shed skin intact. The discarded skin is a transparent envelope of scales that is an exact duplicate of the body's scale pattern.

Snakes lack eyelids and external ears. The eyes are covered by a transparent, shieldlike scale that is replaced when the snake sheds its skin. This lack of a movable eyelid is responsible for the animal's often disconcerting stare. Snakes cannot hear most airborne sounds, but they can detect low-frequency vibrations in the ground by means of bones in their lower jaws. This allows a snake to sense the approach of another animal. Snakes also do not have vocal cords and so are voiceless. However, many species can make loud hissing noises. They produce the sound by expelling air through an opening in the throat known as the glottis.

Vision in some species is very good, while in others it is not well developed. Many burrowing snakes, such as the blind snakes, are sightless. Vipers, pit vipers, and other nocturnal snakes have elliptical pupils that look like vertical slits in bright light. In darkness the pupils dilate, or open up, for better night vision.

The pit vipers and some pythons and boas have heat-sensitive pits on the head that detect infrared radiation, or heat. Many of these snakes capture birds or mammals in total darkness by sensing the prey's body heat. The pit vipers have a pair of pits, one on each side of the head, between the eye and nostril. In boas and pythons with such pits, several pits are situated along the snake's lips.

The snake's forked tongue gathers chemical information about its surroundings. When the tongue is flicked out of the mouth, chemical particles in the air adhere to its moist surface. The tongue is then drawn in and pressed against a sensory structure called Jacobson's organ that is located in the roof of the mouth. This organ can distinguish between various chemical stimuli. When a snake senses movement in its environment, it will begin to flick its tongue in and out in search of chemical information.

Regulation of Body Temperature
Snakes are poikilothermic-that is, their body temperature varies with the temperature of the environment. Poikilotherms are often described as cold-blooded, a misleading definition. Unlike homeotherms (so-called "warm-blooded" animals)-whose body temperature remains constant regardless of environmental temperature-poikilotherms use behavior to control their body temperature. In cold conditions a snake's metabolism slows down considerably, and snakes can become immobile at temperatures several degrees above freezing. This can make them vulnerable to predators during extended cold periods, such as overnight. To avoid this, most snakes spend the night below ground or in another protected area. In the morning, the snake often makes its way to a sunny open area, such as an exposed rock. As it basks in the sun, it slowly warms up and its metabolic rate increases until it can move around at a normal pace again.

In temperate regions snakes spend the winter in a dormant state called hibernation. They usually seek out an underground den in which to spend this long inactive period. Many snakes, often of different species, may share a well-protected den.

Overheating can also be a serious problem. Most snakes cannot tolerate temperatures above about 100° F (38° C) for more than a few minutes. They must avoid prolonged exposure to direct sunlight on hot days. In warm seasons a snake often seeks the shelter of a shady spot after it finishes its morning sunbath.

Snakes capture various animals as prey. Many species eat only certain types of prey. Some hognose snakes, for example, eat almost exclusively toads of the genus Bufo. Water snakes prey mostly on fishes and frogs, and the tree-climbing rat snakes eat mainly birds and bird eggs. Rattlesnakes eat mainly small mammals such as rodents. A few groups, such as the coral snakes, feed on other snakes and lizards. Others, such as racers, eat a wide variety of vertebrates and invertebrates.

Most snakes have strong jaws with rows of sharp, backward-pointing teeth to catch and hold their prey. The snake gradually works its jaws over the captured animal, swallowing it whole and usually head first. A snake may take more than an hour to completely swallow a large meal.

Some snakes have unusual features adapted to their specialized diets. For instance, the snail-eating snakes of South America and Asia have enlarged teeth on the lower jaw. The snakes use their jaws like a ratchet to extract snails from their shells. The egg-eating snakes of Africa have downward-pointing spines on their front vertebrae. The spines break an egg after it has been swallowed so that the snake can regurgitate the shell.

Snakes' food sources are often scarce or unpredictable. Therefore, snakes have evolved physiological characteristics that allow them to go for long periods without eating. Individuals of many species have been known to go for several months in captivity without food, though they require water on a frequent basis. Like other reptiles, snakes are dormant and do not require food during cold weather. During warmer periods, if food is scarce, snakes get energy from fat stored in their bodies. The fat is replenished when food becomes more plentiful.

Using Venom to Capture Prey
Members of the families Viperidae and Elapidae inject venom into their prey through a pair of hollow fangs in the front of the mouth. This immobilizes and then kills the prey. The venom is made in a pair of glands located at the back of the head and then passes through a duct to the fangs. Some members of the Colubridae family have fangs in the rear of the mouth and venomous saliva. These fangs are not hollow, but they have lengthwise grooves. While the snake bites its prey, the toxic saliva can enter the puncture wound through the grooves in the fangs.

Constriction
Many nonvenomous snakes are constrictors that coil around their prey and squeeze until the animal dies from suffocation. Constrictors include not only the large boas and pythons but also many smaller species such as king snakes and rat snakes. ( See also boa constrictor; anaconda; rosy boa.)

Snakes have many natural enemies and, like other animals, have a variety of defenses. The natural enemies of snakes include many kinds of birds and mammals, crocodilians, turtles, and other snakes. Hawks, owls, wading birds, and members of the cat and weasel families eat large numbers of snakes. Large invertebrates such as centipedes and scorpions may eat smaller snakes.

Many snakes will bite an attacker if given the opportunity. Bites from nonvenomous snakes are generally harmless to humans, though the bites of some of the larger species can cause lacerations and extensive bleeding. Although constrictors squeeze their prey to death, constriction is not normally used for defense.

Coloration
The coloring of snakes can offer protection from predators in different ways. In some species coloring provides camouflage. For example, many arboreal snakes are bright green and resemble vines. Copperheads and many other forest-dwelling species have brown crossbands that match the pattern of dead leaves and debris on the forest floor. Some snakes, particularly species that are active above ground much of the time, have uniform color patterns or longitudinal stripes that create an optical illusion that eliminates the sensation of motion. A predator attempting to keep its eye on the body of a black racer or ribbon snake soon finds itself watching the tail of the snake disappear. This type of illusion has led to the mistaken belief that many snakes, including racers and coachwhips, are extremely fast-moving; in reality most snakes cannot travel as fast as a human can walk.

Bright colors, particularly red, yellow, and orange, on the underbody are an important defensive adaptation in some species. When threatened, the snake displays the underside of the tail and rear portion of the body. The sudden display of bright color startles the potential predator, which then may flee. ( See also protective coloration; sand boa; green tree python; ribbon snake.)

Mimicry can also protect snakes from predators. Many species of snake in the Western Hemisphere have bright red and yellow rings encircling the body. They thus resemble the venomous coral snakes that inhabit the same regions. Although such mimic snakes are harmless, their resemblance to dangerous predators warns away potential enemies.

Other Defense Strategies
Some snakes use noise as a threat. The most dramatic examples are the several species of North American rattlesnake, which create a loud rattling sound by vibrating the dried scales at the end of their tails. Deadly cobras, harmless hognose snakes, and a variety of other species assume an erect posture and spread their neck regions to intimidate potential enemies. A final resort of some species is to pretend to be dead or dying. This behavior reaches its extreme in hognose snakes, which writhe, bleed from the mouth, and regurgitate their food during their death act.

Most snake species move by using their ventral scales-the scales on the undersides of their bodies-to pull themselves across rough surfaces. Even a paved road has enough rough spots for the ventral scales to gain purchase and pull the snake along. The snake's many ribs are connected by muscles to the ventral scales, though the ribs themselves are firmly attached to the vertebrae and are immobile.

Most species use a type of movement called serpentine locomotion, in which the body winds itself into a series of S-shaped horizontal loops. Each section of a loop pushes against surface resistance.

Other species resemble caterpillars in motion. They inch along in a more or less straight line, using a flow of muscle contractions along the sides. The body is sequentially lifted, anchored, and pushed forward by resistance against the ventral scales. This type of movement is called rectilinear, or caterpillar, locomotion and is used by large, heavy-bodied snakes such as some of the boas and pythons.

Some species use concertina locomotion, so-named because the movement resembles the opening and closing of an accordion-like instrument called a concertina. The back part of the body is securely anchored, and the front part of the body is extended as far forward as possible. The front part is then anchored, and the rear portion is drawn up into accordion-like folds.

Tree snakes modify the concertina technique to move from branch to branch, and some are able to stretch across open spaces of more than half their body length. To scale vertical tree trunks, rat snakes use a combination of locomotion techniques. The flying snakes of India and Southeast Asia can flatten their bodies to such an extent that the animals can glide from one tree to another in a manner that resembles flight.

Some snakes, such as sidewinder rattlesnakes and the African horned viper use a specialized form of locomotion called sidewinding. This is characteristic of desert dwellers that need to travel across loose sand, where the lack of surface friction makes the other methods of locomotion impossible. The front part of the body is thrown upward and sideways in an arch, landing several inches to the side of the original location. The rest of the body follows the same path through the air without touching the sand in between, so that the snake progresses sideways, leaving a track of disconnected, parallel marks in the sand.

All snakes are capable of swimming, though many never encounter open water in their natural habitats. Terrestrial species use serpentine locomotion to travel across the surface of open bodies of water. However, sea snakes, which spend most of their lives in the water, have tails that are slightly flattened vertically and function like paddles.

Most snakes are generally solitary for most of the year. In some species large numbers congregate for mating or hibernation. Raftlike masses of thousands of sea snakes, presumably congregating for breeding purposes, have been observed in the Pacific Ocean. North American garter snakes sometimes are found in enormous numbers during the early spring mating season. During other parts of the year, some species may be abundant in a particular area, but each individual functions independently of the others.

The life cycle and mating behavior of snakes vary regionally in response to environmental conditions. Snakes in tropical regions mate throughout the year, but the timing is often related to wet-dry seasons and varies from species to species. Snakes in colder regions mate either in the fall before hibernation or in early spring.

Most snakes are oviparous, meaning that the female lays eggs. In other species the eggs develop and hatch inside the mother's body, but the snake gives birth to live young. Such species are called ovoviviparous. Both strategies are found in most regions of the world, though a greater proportion of tropical snakes lay eggs than do snakes in temperate regions. Depending on the species, gestation (the time from fertilization to birth) can range from about six months to two years. The number of young varies from about three to more than 50, again depending on the species.

Baby snakes resemble the adults at birth. They are adapted to cope with their environments immediately after birth. The young of live-bearing species are enclosed in a thin membrane, from which they emerge within a few minutes after leaving the mother's body. The hatchlings of oviparous species possess a tiny scale on the end of the nose. This scale, known as the egg tooth, is used to slit open the leathery egg from the inside. Baby snakes shed their outer layer of skin soon after birth, and the egg tooth is lost during this process.

Like other reptiles, snakes grow rapidly as juveniles. Some may grow throughout their lifetimes, but once they have attained maturity their growth slows considerably. In some species the female snakes are much larger than the males, whereas in other species the males are larger. Species in which the females are larger generally produce greater numbers of young than do species in which the females are smaller. Larger size in males is found in species in which the males engage in combat for territories or mates.

Snakes are known to live for several years in the wild, but the maximum lifetime of any species in the wild is unknown. Individuals of several different species have been kept alive in captivity for more than 20 years, and a few have lived for more than 30 years.

Within the class Reptilia, snakes are classified in the order Squamata (along with the lizards) and the suborder Serpentes. The finer taxonomic classification of snakes is a contentious area of zoology. Starting in the late 20th century, genetic data have raised questions about standing classifications, most of which are based on fossil and anatomical evidence. However, the suborder is commonly divided into the blind snakes (roughly 375 species) and the typical snakes (some 2,500 species). The latter group is made up of the lower snakes and the higher snakes. The lower snakes include pipe snakes, shieldtail snakes, boas, and pythons. The higher snakes include the three largest snake families, Colubridae, Elapidae, and Viperidae, as well as the stiletto vipers and mole vipers. Different classification systems divide the living snakes into different numbers of families, often more than 15. Some of the major families are discussed below.

Blind Snakes
The blind snakes are small burrowing species in which all scales covering the body are the same size. The animals are seldom longer than 8 inches (20 centimeters). Their eyes are reduced to tiny eyespots, which are covered by bony head shields. The short, blunt tail resembles the head. Most species have remnants of the pelvic girdle. The blind snakes constitute three families: Typhlopidae (blind snakes), found in most tropical areas; Anomalepididae (dawn blind snakes), found from Central America to northern South America; and Leptotyphlopidae (worm snakes, thread snakes, or slender blind snakes), found from the southwestern United States to South America and in most of Africa and the adjoining portions of Asia.

Pipe Snakes
The pipe snakes (family Cylindrophiidae) are primarily tropical species restricted to Central and South America and Southeast Asia. They have remnants of the pelvic girdle and visible vestigial hind limbs. They are medium-sized burrowing snakes with small, smooth scales.

Shieldtail Snakes
The shieldtail, or rough-scale, snakes (family Uropeltidae) are confined to India and Sri Lanka. These generally small snakes use their solid head bones to burrow in the soil. Shieldtail snakes are characterized by an enlarged scale on the end of the tail that may be rough or spiny. Some species have bright color patterns.

Boas and Pythons
The families Boidae ( boas) and Pythonidae ( pythons) are closely related. They include the largest snakes in the world, such as the giant anaconda ( Eunectes murinus) of South America and the reticulated python ( Python reticulatus) of Asia. Most are constrictors that live mainly in trees or on the ground, though several species are small burrowers and some are semiaquatic. Most boas and pythons have pelvic girdle remnants and vestigial hind limbs terminating in claws, or spurs, that are visible on the underbelly, on either side of the vent. Members of the family Boidae inhabit the Americas, Africa, and Asia, while members of the family Pythonidae occur in Asia, Africa, and Australia. (The sole species of python found in the Americas is usually classified in its own family.)

More than half of the world's snake species belong to the family Colubridae. The family includes the racers, king snakes, rat snakes, water snakes, garter snakes, hognose snakes, rainbow snakes, and hundreds of others. Colubrids have no front fangs, and most have rows of teeth that are of equal size. Some species, such as the rear-fanged snakes, have specialized teeth for feeding and defense. The bite of most of the rear-fanged snakes is harmless or only mildly venomous to humans, but the bite of some colubrids, such as the boomslang ( Dispholidus typus) of Africa, can be fatal. Colubrids are found worldwide, from the tropics to the cooler regions.

Cobras, Mambas, Coral Snakes, and Relatives
The members of the family Elapidae, called elapids, have a pair of immobile, hollow fangs in the front of the mouth that are used to inject venom into prey. Most species are highly venomous, and some are large. The species in this family occupy most of the subtropical and tropical regions of the world. Elapids are found worldwide, except Europe, Madagascar, and Antarctica. Among the notable species are the cobras of Africa and Asia, the kraits (genus Bungarus) of Asia, the mambas (genus Dendroaspis) of Africa, and the many coral snakes of the Americas. The sea snakes also belong to the family Elapidae. They are marine snakes that live mainly along coastal regions of the Pacific and Indian oceans. Elapids constitute most of the snakes of Australia. Many of them are small and harmless, but some Australian elapids, such as the taipans (genus Oxyuranus) and the tiger snake ( Notechis scutatus), are large and very dangerous.

Vipers, Rattlesnakes, Moccasins, and Relatives
Members of the family Viperidae are characterized by a pair of large fangs in the front of the mouth that fold inward and lie horizontally when the mouth is closed. Large venom glands at the back of the head are connected to the hollow fangs by venom ducts. Snakes of the family include the true vipers and the pit vipers, which have heat-sensitive pits on the sides of their heads. The true vipers are found in Europe, Asia, and Africa. They include the European vipers (genus Vipera) and the extremely heavy-bodied Gaboon viper ( Bitis gabonica) of Africa. The pit vipers are more wide-ranging. They are most common in the Americas but are also found in Asia, including Japan, the Philippines, and Indonesia. The pit vipers include rattlesnakes, the copperhead ( Agkistrodon contortrix), the cottonmouth ( A. piscivorus), and fer-de-lance (genus Bothrops).

Stiletto Snakes and Mole Vipers
The classification of the family Atractaspididae is especially contentious, because every type of fang is found among its members. In general, these snakes are highly venomous burrowing animals. They inhabit a wide range of habitats, including deserts. The most notorious genus, Atractaspis, comprises many species of African asps in which the fangs swing outward to the sides. This allows the snake to strike with its mouth closed by swinging its head.

Although the oldest-known fossil snake was dated as 120 million years old, scientists think that snakes may have evolved even earlier. However, the evolutionary origin of snakes remains poorly understood. Whether the first snakes were terrestrial or marine remains a contentious topic. Some DNA studies suggest that snakes may have evolved from terrestrial lizards that excelled at burrowing underground.

The fossil record indicates that snakes began to diversify in the late Cretaceous period. The Colubridae appeared about 22 to 36 million years ago, and the venomous snakes of the families Elapidae and Viperidae appeared about 5 to 22 million years ago. It is believed that these three major families originated in Asia and later spread to other parts of the world. ( See also animal; reptiles; evolution; fossils.)

Perhaps because snakes hold a morbid fascination for humans, they have inspired many myths. It has been said, for example, that snakes use their tails to whip people, shape themselves into hoops and roll down hills, milk cows, and hypnotize their prey. While snakes do have many unusual traits, they are not capable of any of these feats.

Some of the greatest threats to snakes are caused by human activity. Habitat destruction throughout the world has drastically decreased the number of snakes. Some species can survive even in highly urbanized areas, though these species are generally smaller, secretive forms that go unseen by most people. Countless numbers of snakes are also accidentally killed on highways.

International laws restrict the capture and transport of many species of snake, though some continue to be hunted for leather or for the pet trade. Members of venomous species are captured and kept in captivity for the production of antivenin. In some cultures people eat larger snakes. In the southern United States many snakes are killed in rattlesnake roundups, or snake rodeos, in which large numbers of people gather to collect and kill rattlesnakes and other species of snake. Increasingly, members of the public have objected to these events as being inhumane.

Behler, D.A., and Behler, J.L. Snakes (Benchmark Books, 2002).Ernst, C.H., and Zug, G.R. Snakes in Question: The Smithsonian Answer Book, 2nd ed. (Smithsonian Institution, 2004).Greene, H.W. Snakes: The Evolution of Mystery in Nature (Univ. of Calif. Press, 1997). Mattison, Christopher. Snake: The Essential Visual Guide to the World of Snakes (DK Publishing, 2006).Phelps, Tony. Poisonous Snakes, rev. ed. (Blandford, 1989).

# data[].attributes.attachment_link.description
Of all the animals, snakes are among the best known but perhaps the most misunderstood. Snakes are characterized by their elongated limbless bodies. They are found in almost every part of the world except the polar regions. Although the greatest species diversity is found in the tropics, snakes occupy a wide range of habitats, from deserts to rainforests, lakes, and oceans.

# data[].attributes.attachment_link.title
Snakes’ rapid evolution might be the secret of their success

# data[].attributes.attachment_link.description
They might not have legs, but snakes are outpacing their relatives in the race to evolve.

# data[].attributes.attachment_link.title
The Evolution of Snakes: From Tiny Legged Creatures to Specialized Predators

# data[].attributes.attachment_link.readable_text
The Evolution of Cassowaries - Where did they come from?

For many people, the evolution of the cassowary is perplexing. The Southern Cassowary's three-toed feet, amber eyes, casque, and brightly-coloured neck are evocative of a dinosaur. Southern Cassowaries belong to the taxonomic order Struthioniformes, commonly known as 'ratites'.

Ratites - Dinosaur Birds

Ratites are (mostly) large-bodied birds that have adapted to a terrestrial way of life. Other ratites include the ostrich species, emu, New Zealand's five kiwi species and the two rhea species of South America.

Ratites are morphologically different to other birds. They lack a keel bone, to which flight muscles attach. They also only have small vestigial wings. Ratites occur on all Southern continents except Antarctica, reflecting their Gondwanan heritage. They are ancient birds that began to evolve around 60 million years ago, during the Cretaceous period, when non-avian dinosaurs were the dominant animal life on Earth.

Biologists believe that the ratites share a common, flighted ancestor. The ratites may have lost their ability to fly more than once as they evolved and diversified. Flying is the most energy-expensive form of animal movement. Losing the ability to fly allowed the Cassowaries and their ratite relatives (with the exception of kiwis) to grow much larger than other birds. There are three species of Cassowary. The sub-species in Australia is known as Australian Southern Cassowary. Their closest relative is another Australian bird, the emu. These birds probably diverged from a common ancestor 25-30 million years ago.

Birds first appeared in the Jurassic period (about 150 million years ago). The extinction of terrestrial dinosaurs at the end of the Cretaceous period (65 million years ago) allowed birds and mammals to diversify and grow larger. They also took on many of the ecological roles left open by the extinct dinosaurs.

Where are they now?

Over the years humans have exploited ratites for meat, eggs and feathers. The two largest ratites have become extinct within recent centuries for these reasons: the moas of New Zealand and elephant birds of Madagascar. The picture below shows the evolution of the cassowary; the darkened ratites are currently distributed throughout the world and the extinct species are greyed out.

Scientists believe that modern birds evolved from a group of carnivorous dinosaurs known as 'theropods', which walked on two legs. These dinosaurs shared many features of modern birds: feathers, hollow bones, nesting, egg-brooding and care for their young.

# data[].attributes.attachment_link.title
Evolution - Save the Cassowary - Rainforest Rescue

# data[].attributes.attachment_link.description
The evolution of the cassowary originated around 60 million years ago, where the common ancestor of these ancient birds lived alongside dinosaurs.

# data[].attributes.attachment_link.title
Cassowaries | Wet Tropics Management Authority

# data[].attributes.attachment_link.description
The Wet Tropics World Heritage Area is a living natural wonder and a cultural landscape like nowhere else on earth. It hugs the coastal fringes from Townsville to Cairns like a long green ribbon.

# data[].attributes.attachment_link.readable_text
The Evolution of Spiders

Spiders first evolved around 310 million years ago from earlier arachnid ancestors. They currently populate every continent on Earth apart from Antarctica, and there are about 50,000 extant species, with new species continually being discovered. As predators, these octopedal creatures consume large quantities of insects, making them a vital component of most land-based ecosystems.

About a thousand species of spider (Araneae) have been unearthed from fossils, and many of these are extinct ancestors of the modern variety. Due to the soft exteriors of spiders, fossilized remains are more likely to be intact if they were preserved in tree amber, as shown below.

The extinct ancestors of spiders provide a window into how spiders and their unusual adaptations (e.g., webs) evolved and diverged from other species. In the following sections, a timeline of spider ancestors is presented, from the earliest forms of land-based life, to their modern incarnations. Along the way, the evolutionary course of their behavioral and anatomical adaptations is described.

Arthropods (550 mya)

Arthropods were the first group of species to leave the oceans to colonize land. This occurred around 450 million years ago (mya), well before the existence of dinosaurs. The earliest arthropods were marine animals dating back to about 550 mya. They include the Spriggina (pictured) and the Parvancorina. The well-known trilobites were also a type of arthropod.

Arthropods were pre-adapted for the transition to land, having strong exoskeletons and (by 450 mya) rudimentary limbs for locomotion. They had an open circulatory system including a heart, and compound eyes that utilized thousands of photo-receptive units.

Those that took to land developed book lungs (from their gills) to filter oxygen from the air. These book lungs are still present in modern spiders and many related species. Indeed, arthropods later evolved into spiders, insects, centipedes, scorpions, mites, ticks, crabs, shrimp, and lobsters.

Chelicerata (445 mya)

Chelicerata are a subgroup of arthropods that diverged (i.e., became a separate species) around 445 mya. The group now includes spiders, scorpions, horseshoe crabs, mites, and ticks.

Like arthropods, these creatures had segmented bodies and jointed limbs. Chelicerata are defined as having two segments (the head and abdomen) with myriad appendages, including the "chelicerae," which manifest as pincers or fangs. Some chelicerates remained predatory while others became herbivorous or parasitic.

The earliest known chelicerate is Sanctacaris uncata. Another notable extinct chelicerate is Megarachne servinei (pictured above), which was once thought to be a giant spider. It was actually a sea scorpion. Megarachne had a diameter of about 50 cm and went extinct about 300 million years ago.

Trigonotarbida or "Arachnids" (420 mya)

The earliest known arachnids were called Trigonotarbida (pictured below). They looked similar to spiders but did not possess silk-producing glands. Trigonotarbida appeared between 420 and 290 million years ago.

Arachnids comprise a group of octopedal species including spiders, scorpions, mites and ticks. They possess two chelicerae (fangs) that can look like additional legs. Their long, jointed appendages and improved water conservation meant they were well adapted for quick travel across land.

# data[].attributes.attachment_link.title
The Evolution of Spiders and Their Remarkable Adaptations

# data[].attributes.attachment_link.description
This article examines the timeline of spider evolution from arthropods to modern spiders and the unique adaptations they acquired along the way.

# data[].attributes.body
Chelicerates, a group of arthropods that includes spiders, scorpions, and horseshoe crabs, adapted to various environmental changes over time, which shaped their evolutionary trajectory. Key environmental factors that influenced their adaptations include:

1. Transition to Land: Early chelicerates were likely aquatic, but during the Silurian period (around 430 million years ago), some chelicerates moved onto land. This shift was driven by the availability of new ecological niches, such as terrestrial food sources and fewer predators. As a result, chelicerates developed adaptations to cope with life on land, such as:

- Respiratory Adaptations: Gills were replaced with tracheae or book lungs to enable gas exchange in a terrestrial environment.

- Exoskeletons: A hard, water-resistant exoskeleton helped to reduce water loss and provided protection from desiccation.

- Limbs and Movement: Modification of limbs for locomotion on land, including the development of specialized appendages for capturing prey and sensing the environment.

2. Changing Climate: Fluctuations in global climate over millions of years, including ice ages and warming periods, prompted chelicerates to adapt to varying temperatures, moisture levels, and habitats. This influenced their ability to survive in both aquatic and terrestrial environments, leading to diverse adaptations in physiology and behavior.

3. Predation Pressures: Over time, chelicerates evolved features like venom (in spiders and scorpions) and powerful pincers (in horseshoe crabs and scorpions) to subdue prey and defend themselves against predators. This adaptation was essential for survival in increasingly competitive ecosystems.

4. Dietary Changes: As some chelicerates adapted to land, their diet also shifted. For example, spiders evolved to become carnivorous predators, developing silk-producing glands for building webs to trap prey. This allowed them to exploit new food sources, like flying insects.

In summary, chelicerates adapted to environmental changes by evolving specialized respiratory structures, exoskeletons, defensive mechanisms, and feeding strategies, enabling them to thrive in diverse habitats across millions of years.

# data[].attributes.body
Tetrapodophis is an extinct genus of early snakes, notable for its combination of traits seen in both snakes and their limbed ancestors. It lived during the Late Cretaceous period (~95 million years ago) and is famous for its relatively complete fossil, which shows both a small set of reduced limbs and an elongated, snake-like body. This intermediate morphology provides important insights into the evolutionary transition from limbed reptiles to modern snakes. Environmental changes during the time when Tetrapodophis lived would have had significant effects on its adaptations.

1. Changes in Habitat (Marine vs. Terrestrial Environments)

Transition to semi-aquatic or fully aquatic life: Tetrapodophis lived during the Cretaceous period, a time when the Earth experienced significant environmental changes, including rising sea levels and the formation of inland seas. These changes likely played a role in the shift of many reptiles toward aquatic or semi-aquatic lifestyles. Tetrapodophis, which had small, vestigial limbs and an elongated body, might have been adapted to such habitats, where limblessness would be advantageous for swimming or moving through dense vegetation and burrows.

Increased forested environments: As the Cretaceous period progressed, forests were becoming more extensive due to warmer global temperatures and higher levels of atmospheric CO2. These forest environments would have influenced the evolution of species like Tetrapodophis, which would need to adapt to a forest floor habitat where its limbless body could help it navigate leaf litter and undergrowth, while also making it more efficient in moving through narrow spaces and hunting small prey.

2. Changes in Prey Availability

Evolution of smaller, burrowing prey: The dietary adaptations of Tetrapodophis would have been influenced by the types of prey available during its time. As early snakes evolved, they likely became adapted to hunting small, burrowing animals, insects, and possibly other reptiles. The development of an elongated body and reduced limbs could be seen as an adaptation for following prey into tight spaces, such as burrows or crevices, where limbed movement would be inefficient.

Arthropods and small vertebrates: During the Cretaceous, arthropods, amphibians, and small vertebrates were abundant. The small, slender body of Tetrapodophis would be well-suited for hunting these creatures in a variety of environments, from forest floors to coastal areas. The development of a snake-like body plan (with a reduced or absent pelvis and limbs) could be interpreted as an evolutionary response to exploit such prey, making burrowing and slithering a more effective form of locomotion than the sprawling movement of earlier, limbed reptiles.

3. Changes in Climate and Temperature

Warmer climates and increased CO2: The Cretaceous period was characterized by relatively warm global temperatures and higher CO2 levels, which contributed to the spread of tropical and subtropical environments. These climates would have fostered the evolution of a wide range of ectothermic (cold-blooded) reptiles like Tetrapodophis, which would have been adapted to these warm environments. The snake-like body plan of Tetrapodophis might have helped it regulate body temperature more effectively, especially in the dense and humid undergrowth where the animal could seek cooler or warmer microhabitats.

Increased rainfall and more abundant vegetation: Warm, humid conditions would have led to an increase in vegetation and rainfall, which in turn would affect the availability of prey and shelter for animals like Tetrapodophis. A limbless, elongated body could have been an advantage in navigating through thick vegetation, leaf litter, and damp environments, allowing Tetrapodophis to exploit different ecological niches from its limbed ancestors.

4. Predation Pressure and Evolution of Defense Mechanisms

Emergence of larger predators: As larger predatory dinosaurs and other reptiles evolved, smaller, more agile animals like Tetrapodophis may have been under pressure to adapt in ways that helped them avoid predation. A snake-like body could be an advantage in terms of camouflage and hiding in burrows, while reduced limbs would make the animal less visible and more difficult to catch.

Efficiency in ambush predation: The loss of limbs and the elongation of the body might have been an adaptation for ambush predation, allowing Tetrapodophis to lie in wait for unsuspecting prey. This behavior is common in modern snakes, which often use camouflage and stealth to capture prey.

5. Evolution of Sensory and Locomotive Adaptations

Sensory adaptations: With the transition to a limbless body plan, sensory adaptations, such as the development of specialized scales for gripping surfaces, likely evolved in response to the need to sense the environment and detect prey. Additionally, snakes often possess specialized jaws for feeding and highly sensitive chemoreception, which may have also developed during this period in response to environmental factors and the evolution of prey.

Adaptation to various substrates: The loss of limbs in Tetrapodophis would have enabled the animal to move more effectively across a variety of substrates, including sand, mud, water, or dense undergrowth. Its body shape and musculature would be specialized for lateral undulation, a mode of locomotion that is highly effective for traveling across diverse environments.

Conclusion

The environmental changes during the Cretaceous period—rising sea levels, increasing temperature, abundant vegetation, and diverse ecosystems—likely contributed to the evolutionary pressures that shaped Tetrapodophis' adaptations. These changes may have favored a more elongated body, reduced or absent limbs, and specialized locomotion suited to burrowing, swimming, and slithering in search of prey. The combination of ecological and climatic factors would have driven the adaptations seen in Tetrapodophis, making it an important transitional species in the evolutionary history of snakes.