What do snapping turtles eat

What do snapping turtles eat

Turtles are diapsids of the particular order Testudines (or Chelonii) seen as a a special bony or cartilaginous shell developed from their ribs and acting as a protect. "Turtle" may refer to the order as the whole (American English) or to fresh-water and sea-dwelling testudines (British English). The order Testudines includes each extant (living) and wiped out species. The earliest known members of this team date from 220 million years ago, making turtles one of the oldest reptile groups and the more ancient group than snakes or crocodilians. Of the 356 known types alive today, some are highly endangered.

Turtles are ectotherms—animals commonly called cold-blooded—meaning that their internal temp varies according to the particular ambient environment. However, since of their high metabolic rate, leatherback sea turtles have a body temp that is noticeably higher than that of the surrounding water. Turtles are usually classified as amniotes, together with other reptiles, birds, and mammals. Like additional amniotes, turtles breathe air and do not lay eggs underwater, although several species live in or even around water. The research of turtles is called cheloniology, after the Greek term for turtle. It is also sometimes called testudinology, after the Latin title for turtles.

Differences exist in usage of the common terms turtle, tortoise, and terrapin, based on the variety of English being used. These terms are common names , nor reflect precise biological or taxonomic variations.

Turtle may either refer to the order since a whole, or to particular turtles that make up a form taxon that is not monophyletic, or may be restricted to only aquatic species. Tortoise usually refers to any land-dwelling, non-swimming chelonian. Terrapin can be used in order to describe several species associated with small, edible, hard-shell turtles, typically those found within brackish waters.

In North America, all chelonians are usually commonly called turtles. Tortoise is used only within mention of the fully terrestrial turtles or, more narrowly, just those members of Testudinidae, your family of modern property tortoises. Terrapin may relate to small semi-aquatic turtles that live in new and brackish water, specifically the diamondback terrapin (Malaclemys terrapin). Although the members from the genus Terrapene dwell mostly on land, they will are referred to as box turtles rather than tortoises. The American Society of Ichthyologists and Herpetologists uses "turtle" to describe all species of the order Testudines, whether or not they are land-dwelling or sea-dwelling, and uses "tortoise" being a more specific phrase for slow-moving terrestrial varieties.

In the United Empire, the term turtle is used for water-dwelling species, including ones known in the US as terrapins, although not for terrestrial species, which are known only as tortoises.

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turtle The Ocean Enthusiast

The word chelonian will be popular among veterinarians, scientists, plus conservationists working with these types of animals being a catch-all name for any person in the particular superorder Chelonia, which includes all turtles living and extinct, as well as their particular immediate ancestors. Chelonia will be based on the Greek word for turtles, χελώνη chelone; Greek χέλυς chelys "tortoise" is also used in the formation of scientific names of chelonians. Testudines, on the other hands, is based on the Latin word for tortoise, testudo. Terrapin comes through an Algonquian word with regard to turtle.

Some languages perform not have this distinction, as all of these are referred to by the particular same name. For instance , in Spanish, the word tortuga is used for turtles, tortoises, and terrapins. A sea-dwelling turtle is tortuga marina, a freshwater types tortuga de río, and a tortoise tortuga terrestre.

The largest living chelonian is the leatherback ocean turtle (Dermochelys coriacea), which usually reaches a shell duration of 200 cm (6. 6 ft) and can achieve a weight of more than 900 kg (2, 1000 lb). Freshwater turtles are usually generally smaller, but along with the largest species, the Asian softshell turtle Pelochelys cantorii, a few people have been reported upward to 200 cm (6. 6 ft). This dwarfs even the better-known alligator snapping turtle, the biggest chelonian in North America, which attains a shell length of up in order to 80 cm (2. 6 ft) and weighs because much as 113. four kg (250 lb).

Giant tortoises of the genera Geochelone, Meiolania, and others were relatively widely distributed all over the world into prehistoric occasions, and are known to possess existed in North and South America, Australia, and Africa. They became wiped out at the same time as the appearance associated with man, and it will be assumed humans hunted them for food. The just surviving giant tortoises are on the Seychelles and Galápagos Islands and may grow to over 130 centimeter (51 in) in size, and weigh about three hundred kg (660 lb).

The largest ever chelonian has been Archelon ischyros, a Past due Cretaceous sea turtle recognized to have been up to 4. 6 m (15 ft) long.

Freshwater Turtles

The tiniest turtle is the speckled padloper tortoise of Southern Africa. It measures no more than 8 centimeter (3. 1 in) in length and weighs about 140 g (4. 9 oz). Two other species associated with small turtles are the American mud turtles and musk turtles that live in an area that will ranges from Canada to South America. The shell length of many species in this group is much less than 13 cm (5. 1 in) long.

Turtles are divided into two groups, according to the way they retract their necks to their shells (something the our ancestors Proganochelys could not do). The mechanism of neck of the guitar retraction differs phylogenetically: the particular suborder Pleurodira retracts side to side aside, anterior to shoulder girdles, while the suborder Cryptodira retracts straight back again, between shoulder girdles. These types of motions are largely because of to the morphology plus arrangement of cervical backbone. Of all recent turtles, the cervical column consists of nine joints and eight vertebrae, which are usually individually independent. Since these vertebrae are not joined and are rounded, the particular neck is more flexible, being able to flex in the backwards plus sideways directions. The major function and evolutionary inference of neck retraction is thought to be for feeding rather than safety. Neck retraction and reciprocal extension allows the turtle to reach out further to capture prey while going swimming. Neck expansion creates suction once the head is thrust forward and the oropharynx is expanded, and this morphology suggests the retraction function is for serving purposes as the suction helps catch prey. The particular protection the shell offers the head when it is retracted is therefore not the main functionality of retraction, thus is an exaptation. As regarding the difference between the two methods of retraction, both Pleurodirans and Cryptodirans use the quick expansion of the neck like a method of predation, therefore the difference in retraction mechanism is just not due to a difference in ecological niche.

Head

Most turtles that spend most associated with their lives on land get their eyes looking down at objects in front side of them. Some marine turtles, such as snapping turtles and soft-shelled turtles, have eyes closer in order to the very best of the head. These species of turtle may hide from predators in shallow water, where they will lie entirely submerged other than for their eyes and nostrils. Near their eye, sea turtles possess intrigue that produce salty holes that rid themselves of excess salt consumed through the water they drink.

Turtles have rigid beaks and use their teeth to cut and munch food. Instead of having teeth, that they appear in order to have lost about 150-200 million years ago, the upper and lower jaws of the turtle are covered by horny ridges. Carnivorous turtles usually have got knife-sharp ridges for slicing through their prey. Herbivorous turtles have serrated-edged side rails that help them reduce through tough plants. They will use their tongues to swallow food, but as opposed to most reptiles, they cannot stay out their tongues to catch food.

ShellMajor article: Turtle shellThe top shell of the turtle is called the carapace. The lower shell that encases the belly is known as the plastron. The carapace and plastron are joined up with together on the turtle's sides by bony constructions called bridges. The internal layer of a turtle's shell is made upward of about 60 bones that include portions of the backbone and the particular ribs, meaning the turtle cannot crawl away from the shell. In most turtles, the outer layer from the shell is covered simply by horny scales called scutes that are part of the outer skin, or skin. Scutes are made up of the particular fibrous protein keratin that also makes up the scales of other reptiles. These scutes overlap the seams between the covering bones and add power to the shell. Some turtles do not possess horny scutes; with regard to example, the leatherback sea turtle and the soft-shelled turtles have shells covered along with leathery skin instead.

The particular shape of the covering gives helpful clues about how exactly a turtle lives. Most tortoises have a large, dome-shaped shell that makes it difficult for potential predators to crush the cover between their jaws. One of the few conditions is the African pancake tortoise, which has the flat, flexible shell that allows it to hide in rock crevices. Many aquatic turtles have smooth, streamlined shells, which aid within swimming and diving. United states snapping turtles and musk turtles have small, cross-shaped plastrons that give all of them more efficient leg motion for walking along the bottom of ponds and streams. Another exception is the Belawan Turtle (Cirebon, West Java), which has sunken-back soft-shell.

The color of the turtle's shell may differ. Shells are commonly colored brown, black, or olive green. In some species, covers may have red, orange, yellow, or grey marks, often spots, lines, or irregular blotches. Probably the most colorful turtles is the far eastern painted turtle, which contains a yellow plastron and a black or olive shell with red marks around the rim.

Tortoises, being land-based, have rather heavy shells. In comparison, aquatic and soft-shelled turtles have lighter shells that will help them avoid settling in water and swim faster with more speed. These lighter shells have large spaces called fontanelles between the shell bones. The shells of leatherback sea turtles are extremely light because they lack scutes and contain many fontanelles.

It has been recommended by Jackson (2002) that will the turtle shell can function as pH barrier. To endure through anoxic conditions, such as winter season periods trapped beneath ice or within anoxic dirt at the bottom of ponds, turtles utilize two general physiological mechanisms. In the case of prolonged periods of anoxia, it has been shown that the turtle shell both releases carbonate buffers and uptakes lactic acid.

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Breathing Turtles

Respiration, for many amniotes, is achieved by the particular contraction and relaxation of specific muscle groups (i. e. intercostals, abs, and/or a diaphragm) attached with an inner rib-cage that can expand or contract the entire body wall thus assisting airflow in and out of the lungs. The ribs of Chelonians, however, are fused with their carapace and external to their pelvic plus pectoral girdles, a function unique among turtles. This particular rigid shell is not capable of expansion, and by rendering their rib-cage immobile, Testudines have experienced to evolve special adaptations for respiration.

Turtle pulmonary ventilation occurs by making use of specific groups of abdominal muscle groups attached to their viscera and shell that pull the lungs ventrally during inspiration, where air is usually drawn in via a negative pressure gradient (Boyle's Law). In expiration, the contraction from the transversus abdominis is the driving pressure by propelling the viscera into the lungs plus expelling air under positive pressure. Conversely, the comforting and flattening of the particular oblique abdominis muscle draws the transversus back down which, once again, draws air flow back into the lung area. Important auxiliary muscles utilized for ventilatory processes are the pectoralis, which is utilized in conjunction with the particular transverse abdominis during motivation, and the serratus, which movements using the abdominal oblique associated expiration.

The lungs associated with Testudines are multi-chambered plus attached their entire size over the carapace. The amount of chambers may differ in between taxa, though most commonly they will have three lateral chambers, three medial chambers, and another terminal chamber. As mentioned earlier on, the act of specific abdominal muscles pulling lower the viscera (or pressing back up) is what allows for respiration within turtles. Specifically, it will be the turtles large liver that pulls or pushes on the lungs. Ventral to the lungs, in the coelomic cavity, the liver of turtles is attached directly to the right lung, and their belly is directly attached in order to the left lung simply by the ventral mesopneumonium, that is attached to their liver organ by the ventral mesentery. When the liver is pulled down, inspiration begins. Supporting the lungs is the particular post-pulmonary septum, that is discovered in all Testudines, and it is thought to prevent the lungs from collapsing.

The Baby Turtle Free National Geographic Pix

Turtles Skin and molting

As pointed out above, the outer level of the shell is usually part of the pores and skin; each scute (or plate) on the shell corresponds to a single altered scale. The remainder of the skin has a lot smaller scales, like the epidermis of other reptiles. Turtles do not molt their skins all at once as snakes do, yet continuously in small parts. When turtles are held in aquaria, small sheets of dead skin can be seen in the particular water (often appearing to be a thin piece of plastic) having been sloughed off when the particular animals deliberately rub on their own against an item of wood or stone. Tortoises also shed skin, but dead pores and skin is permitted to accumulate in to thick knobs and dishes that provide protection in order to parts of the entire body outside the shell.

Simply by counting the rings formed by the stack of smaller, older scutes on top of the larger, newer ones, it is possible to estimate the age group of a turtle, if one knows how many scutes are produced in per year. This method is not very accurate, partly because growth rate is not really constant, but also since some of the scutes eventually fall away from the shell.

Turtles Braches

Terrestrial tortoises have short, sturdy feet. Tortoises are popular for moving slowly, simply because of their weighty, cumbersome shells, which restrict stride length.

Skeleton associated with snapping turtle (Chelydra serpentina)

Amphibious turtles normally have got limbs similar to the ones from tortoises, except that the particular feet are webbed and often have long paws. These turtles swim making use of all four feet in a way similar to the dog paddle, along with the feet on the left and right side of the particular body alternately providing drive. Large turtles tend in order to swim less than smaller ones, and the very big species, such as alligator snapping turtles, hardly swim at all, preferring in order to walk along the bottom associated with the river or lake. As well as webbed feet, turtles have really long claws, used in order to help them clamber on to riverbanks and floating records upon which they bask. Male turtles tend in order to have particularly long paws, and these appear to be utilized to stimulate the women while mating. While most turtles have webbed foot, some, such as the pig-nosed turtle, have true flippers, along with the digits being joined into paddles as well as the claws being relatively small. These types of species swim in the same way as sea turtles do (see below).

Sea turtles are almost entirely aquatic plus have flippers instead of feet. Sea turtles travel through the water, using the up-and-down motion of the particular front flippers to create drive; the back feet are not used for propulsion but can be used as rudders with regard to steering. Compared with fresh water turtles, sea turtles possess very limited mobility upon land, and apart from the dash from the nest to the sea as hatchlings, male sea turtles normally never leave the sea. Females must come back on to land to lay ovum. They move very slowly and laboriously, dragging themselves forwards with their flippers.

Behavior of Turtles

Senses of Turtles are thought to get exceptional night vision because of the unusually large number of rod cells within their retinas. Turtles have got color vision with the wealth of cone subtypes with sensitivities ranging from the near ultraviolet (UVA) to red. Some land turtles have very bad pursuit movement abilities, which are normally found only in predators that quest quick-moving prey, but carnivorous turtles are able in order to move their heads quickly to snap.

Turtles Communication

The particular Arrau turtle has a sizable vocal repertoire.

Whilst typically thought of since mute, turtles make numerous sounds when communicating. Tortoises may be vocal when dating and mating. Various species of both freshwater and sea turtles emit numerous types of calls, frequently short and low rate of recurrence, from the time they are in the egg to if they are adults. These types of vocalizations may serve in order to create group cohesion whenever migrating.

Turtle Cleverness

See furthermore: Animal cognition

It provides been reported that wooden turtles are better than white rats at studying to navigate mazes. Case studies exist of turtles playing. They are doing, however, have got a very low encephalization quotient (relative brain in order to body mass), and their particular hard shells enable these to live without fast reflexes or elaborate predator prevention strategies. In the laboratory, turtles (Pseudemys nelsoni) may learn novel operant jobs and also have demonstrated a long-term memory of at least 7. 5 months.

Turtle Mating Techniques

An illustration of mounting behavior within turtles

Turtles are known for displaying a wide variety of mating behaviours, however , they are not known for forming pair-bonds or for being component of a social group. Once fertilization has happened and an offspring has been produced, neither mother or father will provide care for the offspring once it's hatched. Females generally outnumber males in various turtle species (such as Green turtles), and as a result, most males will participate in multiple copulation with multiple partners throughout their lifespan. However, because of to the sexual dimorphism present in most turtle species, males must develop different courting strategies or even use alternate methods in order to gain access to a potential mate. Most terrestrial types have males that are usually bigger than females, and combating between males often decides a hierarchical order within which the higher upward the order an individual is, the better the chance is of the individual getting access to the potential mate. For most semi-aquatic species and bottom-walking aquatic species, combat happens less often. Males belonging to semi-aquatic and bottom-walking species instead often make use of their larger size advantage to forcibly mate using a female. In fully marine species, males are usually smaller than females plus therefore they can not use the particular same strategy as their semi-aquatic relatives, which relies on overpowering the females with strength. Males in this category resort to using courtship displays in an attempt to gain mating access to a female.

Fighting Between Males Turtles

Saddle back Galapagos tortoise

Wood turtles are an example of the terrestrial species where the males have a hierarchical ranking system based upon dominance through fighting, and it's shown that the particular males with the greatest rank and thus the most wins in fights have the most offspring.

Galapagos tortoises are another example of a varieties which has a hierarchical rank which is determined simply by dominance displays, and accessibility to food and partners is regulated by this dominance hierarchy. Two male saddle backs most frequently compete for access to cactus trees, which is their own source of food. The particular winner is the person who stretches their neck of the guitar the highest, which individual gets access to the cactus tree, which can attract potential mates.

Push Mating Turtles

Male (left) and female (right) radiated tortoise

The male scorpion dirt turtle is an instance of a bottom-walking aquatic species that relies on overwhelming females with its bigger size as a mating strategy. The male techniques the feminine from the back, and often resorts to aggressive methods for example biting the female's tail or even hind limbs, followed by a mounting behavior in which usually the male clasps the particular edges of her carapace with his forelimbs plus hind limbs to keep her in position. The male follows this action by laterally waving his mind and sometimes biting the female's head in an attempt to get the girl to withdraw her go to her shell. This exposes her cloaca, and with it exposed, the man can attempt copulation simply by seeking to insert his holding tail.

Male radiated tortoises will also be known to make use of the force mating strategy wherein they use encircling vegetation to trap or prevent females from escaping, then pin them straight down for copulation.

Turtles Courtship Displays

Red-eared sliders are an sort of a fully aquatic species where the male performs a courtship behavior. Within this case the male extends his forelegs with all the palms facing out plus flutters his forelegs in the female's face. Female options are important in this method, and the females of several species, such as eco-friendly sea turtles, aren't always receptive. Therefore, they've progressed certain behaviors to prevent the male's attempts at copulation, such as swimming away, confronting the male followed by biting, or even a refusal position within which the female presumes a vertical position with her limbs widely outspread and her plastron facing the male. If the particular water is too shallow to perform the refusal position, the females may resort to beaching on their own, which is a confirmed deterrent method, as the particular males will not follow all of them ashore.

Ecology and life history of turtles

Sea turtle swimming

Although numerous turtles spend large quantities of their lives underwater, all turtles and tortoises breathe air and should surface at regular time periods to refill their lungs. They can also invest much or all of their lives on dried out land. Aquatic respiration within Australian freshwater turtles is currently being studied. A few species have large cloacal cavities that are covered with many finger-like projections. These projections, called papillae, have a rich blood provide and improve the surface area of the cloaca. The particular turtles can take up dissolved oxygen from the water providing a few papillae, in much the same method that fish use gills to respire.

Like additional reptiles, turtles lay ovum that are slightly gentle and leathery. The eggs from the greatest species are spherical while the ovum of the rest are usually elongated. Their albumen is white and contains a different protein from bird ovum, such that it may not coagulate when cooked. Turtle eggs ready to eat consist mainly of yolk. In some species, temperature determines whether an egg develops into a male or perhaps a female: a higher temperature causes a female, the lower temperature causes a male. Large numbers of ovum are deposited in holes dug into mud or even sand. They are after that covered and left to incubate on their own. Depending upon the species, the ovum will typically take 70–120 days to hatch. Once the turtles hatch, they squirm their way to the particular surface and head toward the water. There are simply no known species where the mother cares for her youthful.

Sea turtles lay their particular eggs on dry, exotic beaches. Immature sea turtles are not cared with regard to by the adults. Turtles can take many many years to achieve breeding age, plus in many cases, breed every few years ınstead of annually.

Researchers have recently uncovered a turtle's internal organs usually do not little by little break lower or become less effective over time, unlike many other animals. It was found that the liver, lungs, and kidneys of a centenarian turtle are usually almost indistinguishable from those of its immature version. This has inspired hereditary researchers to start analyzing the turtle genome regarding longevity genes.

A group of turtles is actually a bale.

Turtles Diet

A green sea turtle grazing on

A turtle's diet varies greatly determined by the atmosphere by which it lives. Grownup turtles typically eat aquatic plants; (citation needed) invertebrates such as insects, snails, plus worms; and have already been reported to occasionally eat dead marine animals. Many small freshwater species are usually carnivorous, eating small fish and a wide variety of aquatic life. However, protein is important to turtle growth plus juvenile turtles are purely carnivorous.

Sea turtles usually feed on jellyfish, sponges, and other soft-bodied organisms. Some species with better jaws have been noticed to eat shellfish, whilst others, such as the green sea turtle, do not eat meat at all plus, instead, possess a diet largely made up of algae.

Systematics and evolution of Turtles

Main article: Turtle classification

See|Observe|Notice} also: List of Testudines families

Life restoration associated with Odontochelys semitestacea, the earliest known turtle relative along with a partial shell

"Chelonia" from Ernst Haeckel's Kunstformen der Natur, 1904

Centered on body fossils, the particular first proto-turtles are believed to have existed in the particular late Triassic Period of the Mesozoic era, about 220 million years ago, and their shell, which has remained a remarkably stable body plan, is thought to have evolved through bony extensions of their own backbones and broad steak that expanded and grew together to form the complete shell that offered protection at every stage of its evolution, also when the bony element of the shell was not really complete. This is supported by fossils of the particular freshwater Odontochelys semitestacea or "half-shelled turtle with teeth", from the late Triassic, which have been discovered near Guangling in south west China. Odontochelys displays a complete bony plastron plus an incomplete carapace, comparable to an early stage of turtle embryonic advancement. Prior to this discovery, the earliest-known fossil turtle ancestors, like Proganochelys, were terrestrial and had a complete covering, offering no clue in order to the evolution of this exceptional anatomical feature. By the past due Jurassic, turtles had extended widely, and their fossil history becomes simpler to read.

Their specific ancestry has been disputed. It had been believed they are the only surviving branch associated with the ancient evolutionary quality Anapsida, which includes groupings such as procolophonids, millerettids, protorothyrids, and pareiasaurs. All anapsid skulls lack a temporal opening while all additional extant amniotes have temporal openings (although in mammals, the hole has become the zygomatic arch). The particular millerettids, protorothyrids, and pareiasaurs became extinct in the particular late Permian period plus the procolophonoids during the particular Triassic.

However , it was later suggested that this anapsid-like turtle head may be due to reversion rather than to anapsid descent. More recent morphological phylogenetic studies with this in mind placed turtles firmly within diapsids, slightly closer to Squamata than to Archosauria.[55][56] All molecular studies possess strongly upheld the positioning of turtles within diapsids; some place turtles inside Archosauria, or, more generally, as a sister team to extant archosaurs,[58][59][60][61] though an analysis performed by Lyson et al. (2012) recovered turtles because the sister group of lepidosaurs instead. Reanalysis of prior phylogenies suggests that they classified turtles as anapsids both because they assumed this particular classification (most of them studying what sort of anapsid turtles are) and because they did not sample fossil and extant taxa broadly enough for constructing the cladogram. Testudines were suggested to have diverged from other diapsids in between 200 and 279 million years ago, though the particular debate is far through settled. Even the conventional placement of turtles outdoors Diapsida cannot be dominated out at this stage. A combined analysis associated with morphological and molecular information conducted by Lee (2001) found turtles to become anapsids (though a relationship with archosaurs couldn't end up being statistically rejected).[64] Similarly, a morphological research conducted by Lyson ainsi que al.. (2010) recovered them as anapsids most closely related to Eunotosaurus. A molecular analysis of 248 nuclear genes from sixteen vertebrate taxa suggests that turtles are a sister group to birds and crocodiles (the Archosauria).[66] The date of separation of turtles and wild birds and crocodiles was estimated to be 255 mil years ago. The most current common ancestor of residing turtles, corresponding towards the split between Pleurodira and Cryptodira, was estimated to get occurred around 157 million yrs ago. The oldest definitive crown-group turtle (member from the modern clade Testudines) will be the species Caribemys oxfordiensis from the late Jurassic period (Oxfordian stage). Through utilizing the first genomic-scale phylogenetic analysis associated with ultraconserved elements (UCEs) to investigate the placement of turtles within reptiles, Crawford et al. (2012) also suggest that turtles are the sister group to parrots and crocodiles (the Archosauria).

The first genome-wide phylogenetic analysis was completed by Wang et al. (2013). Using the draft genomes of Chelonia mydas and Pelodiscus sinensis, the group used largest turtle information set to date in their own analysis and concluded that turtles are likely a sister group of crocodilians and birds (Archosauria). This particular placement within the diapsids suggests that the turtle lineage lost diapsid skull characteristics as it right now possesses an anapsid-like head.

The earliest known fully shelled member of the particular turtle lineage is the particular late Triassic Proganochelys. This genus already possessed many advanced turtle traits, plus thus probably indicates numerous millions of years of preceding turtle evolution; this particular is further supported by evidence from fossil tracks from the Early Triassic of the United Says (Wyoming and Utah) plus from the Middle Triassic of Germany, indicating that proto-turtles already existed as early as the Early Triassic. Proganochelys lacked the opportunity to draw its head into its shell, had a long neck, and had the long, spiked tail ending in a club. While this body form is similar to that of ankylosaurs, this resulted from convergent advancement.

Turtles are divided in to two extant suborders: Cryptodira and Pleurodira. The Cryptodira is the larger of the two groups plus includes all the marine turtles, the terrestrial tortoises, and many of the freshwater turtles. The Pleurodira are sometimes known as the particular side-necked turtles, a guide to how they retract their own heads to their shells. This smaller group consists mainly of various freshwater turtles.