Biology Science is Cool!

Biology Science is Cool!

Turtles are diapsids of the particular order Testudines (or Chelonii) characterized by a special bony or cartilaginous shell created from their ribs and acting as a shield. "Turtle" may refer in order to the order as the whole (American English) or even to fresh-water and sea-dwelling testudines (British English). The order Testudines includes each extant (living) and wiped out species. The earliest recognized members of this team date from 220 mil years ago, making turtles one of the earliest reptile groups and the more ancient group than snakes or crocodilians. Associated with the 356 known varieties alive today, some are usually highly endangered.

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

Differences exist in usage of the particular common terms turtle, tortoise, and terrapin, depending on the range of English being utilized. These terms are common names , nor reflect accurate biological or taxonomic variations.

Turtle may either relate to the order since a whole, or to particular turtles that create up a form taxon which is not monophyletic, or may be limited to only marine species. Tortoise usually relates to any land-dwelling, non-swimming chelonian. Terrapin is used in order to describe several species of 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, only those members of Testudinidae, the family of modern land tortoises. Terrapin may refer to small semi-aquatic turtles that live in refreshing and brackish water, in particular the diamondback terrapin (Malaclemys terrapin). Although the people from the genus Terrapene dwell mostly on land, they are known 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 term for slow-moving terrestrial types.

In the United Kingdom, the word turtle is used for water-dwelling species, which includes ones known in the US as terrapins, but not for terrestrial species, which are known only as tortoises.

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Lets Learn about Green sea turtles. – Journal Edge

The word chelonian is usually well-liked by veterinarians, scientists, and conservationists working with these types of animals like a catch-all name for any member of the superorder Chelonia, which includes almost all turtles living and wiped out, as well as their particular immediate ancestors. Chelonia will be based on the Ancient greek word for turtles, χελώνη chelone; Greek χέλυς chelys "tortoise" is also utilized in the formation of technological names of chelonians. Testudines, on the other hands, is based on the Latin word for tortoise, testudo. Terrapin comes from an Algonquian word with regard to turtle.

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

The largest living chelonian is the leatherback sea turtle (Dermochelys coriacea), which reaches a shell duration of 200 cm (6. six ft) and can achieve a weight of over 900 kg (2, 000 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 up to 200 cm (6. 6 ft). This dwarfs even the better-known alligator snapping turtle, the biggest chelonian in North America, which attains a cover length of up in order to 80 cm (2. 6 ft) and weighs since much as 113. four kg (250 lb).

Giant tortoises of the genera Geochelone, Meiolania, and other people were relatively widely dispersed all over the world into prehistoric occasions, and are known to have got existed in North plus South America, Australia, plus Africa. They became vanished at the same time as the appearance of man, and it will be assumed humans hunted all of them for food. The only surviving giant tortoises are usually on the Seychelles and Galápagos Islands and can grow to over 130 cm (51 in) in size, and weigh about 300 kg (660 lb).

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

turtle The Ocean Enthusiast

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

Turtles are divided into two groups, according to how they retract their necks to their shells (something the ancestral Proganochelys could not do). The mechanism of neck retraction differs phylogenetically: the particular suborder Pleurodira retracts side to side aside, anterior to shoulder girdles, while the suborder Cryptodira retracts straight back, between shoulder girdles. These types of motions are largely due to the morphology plus arrangement of cervical backbone. Of all recent turtles, the cervical column is made up of nine joints and eight vertebrae, which are usually individually independent. Since these types of vertebrae are not fused and are rounded, the particular neck is more versatile, being able to flex in the backwards and sideways directions. The major function and evolutionary implication of neck retraction will be thought to be regarding feeding rather than protection. Neck retraction and testing extension allows the turtle to achieve 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 provides the head when this is retracted is as a result not the main functionality of retraction, thus is an exaptation. As regarding the difference between the particular two methods of retraction, both Pleurodirans and Cryptodirans use the quick extension of the neck as a method of predation, therefore the difference in retraction mechanism is not due in order to a difference in ecological niche.

Head

Most turtles that spend most of their lives on land get their eyes looking lower at objects in front side of them. Some marine turtles, such as nipping turtles and soft-shelled turtles, have eyes closer to the top of the mind. These types of turtle can hide from predators in shallow water, where they lie entirely submerged other than for their eyes and nostrils. Near their eye, sea turtles possess intrigue that produce salty holes that rid their body associated with excess salt consumed through the water they consume.

Turtles have rigid beaks and use their teeth to cut and chew up food. Instead of having teeth, that they appear to have lost about 150-200 million years ago, the particular upper and lower teeth 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 cut through tough plants. They will use their tongues to swallow food, but in contrast to most reptiles, they can not stay out their tongues to catch food.

ShellMain article: Turtle shellTop of the shell of the turtle is known as the carapace. The lower shell that encases the belly is called the plastron. The carapace and plastron are became a member of together on the turtle's sides by bony buildings called bridges. The inner 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 from its shell. In most turtles, the outer layer of the shell is covered by horny scales called scutes which are part of the outer skin, or skin. Scutes comprise of the fibrous protein keratin that also makes up the particular scales of other reptiles. These scutes overlap the particular seams between the cover bones and add strength towards the shell. Some turtles do not have horny scutes; regarding example, the leatherback ocean turtle and the soft-shelled turtles have shells covered with leathery skin instead.

The shape of the cover gives helpful clues about how a turtle lives. The majority of tortoises have a large, dome-shaped shell that makes it difficult for predators to crush the cover between their jaws. A single of the few exclusions is the African hot cake tortoise, which has the flat, flexible shell that allows it to hide in rock crevices. Many aquatic turtles have toned, streamlined shells, which help in swimming and diving. American snapping turtles and musk turtles have small, cross-shaped plastrons that give them more efficient leg motion for walking along the particular bottom of ponds plus streams. Another exception is the Belawan Turtle (Cirebon, West Java), which has sunken-back soft-shell.

The color of a turtle's shell may vary. Shells are commonly colored brown, black, or olive green. In certain species, shells may have red, orange, yellow, or grey marks, often spots, lines, or irregular blotches. One of the most colourful turtles is the far eastern painted turtle, which contains a yellow plastron plus a black or olive shell with red marks around the rim.

Tortoises, being land-based, have instead heavy shells. In contrast, aquatic and soft-shelled turtles have lighter shells that will help them avoid sinking in water and swim faster with more agility. These lighter shells have large spaces called fontanelles between the shell bone fragments. The shells of leatherback sea turtles are really lighting because they lack scutes and contain many fontanelles.

It has been suggested by Jackson (2002) that will the turtle shell may function as pH barrier. To endure through anoxic conditions, such as winter periods trapped beneath ice or within anoxic mud at the bottom of ponds, turtles utilize two general physiological mechanisms. In the situation of prolonged periods associated with anoxia, it has already 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 associated with specific muscles (i. electronic. intercostals, abs, and/or a diaphragm) attached to an inner rib-cage that can increase or contract the entire body wall thus assisting air flow in and out of the lung area. The ribs of Chelonians, however, are fused with their carapace and exterior to their pelvic plus pectoral girdles, a function unique among turtles. This particular rigid shell is not really capable of expansion, plus by rendering their rib-cage immobile, Testudines have got to evolve special adaptations for respiration.

Turtle pulmonary ventilation occurs by making use of specific categories of abdominal muscle groups attached to their viscera and shell that draw the lungs ventrally throughout inspiration, where air will be drawn in via the negative pressure gradient (Boyle's Law). In expiration, the particular contraction of the transversus abdominis is the driving pressure by propelling the viscera into the lungs and expelling air under optimistic pressure. Conversely, the calming and flattening of the oblique abdominis muscle drags the transversus back lower which, once again, draws atmosphere back into the lung area. Important auxiliary muscles utilized for ventilatory processes would be the pectoralis, which is utilized in conjunction with the transverse abdominis during inspiration, as well as the serratus, which techniques using the abdominal oblique accompanying expiration.

The lungs associated with Testudines are multi-chambered and attached their entire size down the carapace. The quantity of chambers can differ in between taxa, though most often these people have three lateral chambers, three medial chambers, and another terminal chamber. As earlier mentioned, the act of particular abdominal muscles pulling down the viscera (or pushing back up) is what allows for respiration within turtles. Specifically, it is usually the turtles large liver organ that pulls or forces on the lungs. Ventral to the lungs, in the coelomic cavity, the liver of turtles is attached directly to the correct lung, and their abdomen is directly attached to the left lung simply by the ventral mesopneumonium, which is attached to their liver by the ventral mesentery. Whenever the liver is taken down, inspiration begins. Supporting the lungs is the post-pulmonary septum, that is discovered in all Testudines, and it is thought to prevent the particular lungs from collapsing.

turtle The Ocean Enthusiast

Turtles Skin and molting

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

Simply by counting the rings shaped by the stack associated with smaller, older scutes on top of the larger, newer types, you are able to estimate the age group of a turtle, when one knows the number of scutes are produced in a year. This method is not really very accurate, partly due to the fact growth rate is not really constant, but also because some of the scutes eventually fall away from the shell.

Turtles Limbs

Terrestrial tortoises have short, durable feet. Tortoises are well-known for moving slowly, in part because of their large, cumbersome shells, which restrict stride length.

Skeleton of snapping turtle (Chelydra serpentina)

Amphibious turtles normally possess limbs similar to those of tortoises, except that the particular feet are webbed and often have long paws. These turtles swim using all four feet in a way similar to the dog paddle, with the feet on the particular right and left side of the particular body alternately providing drive. Large turtles tend to swim less than smaller sized ones, and the really big species, such since alligator snapping turtles, barely swim whatsoever, preferring to walk along the bottom associated with the river or river. As well as webbed feet, turtles have very long claws, used in order to help them clamber onto riverbanks and floating logs upon which they bask. Male turtles tend in order to have particularly long claws, and these seem to be utilized to stimulate the women while mating. While most turtles have webbed ft, some, like the pig-nosed turtle, have true flippers, along with the digits being fused into paddles and the paws being relatively small. These species swim in the same manner because sea turtles do (see below).

Sea turtles are almost entirely aquatic plus have flippers instead associated with feet. Sea turtles travel with the water, using the up-and-down motion of the front flippers to generate thrust; the back feet are certainly not used for propulsion yet may be used as rudders for steering. Compared with fresh water turtles, sea turtles have got very limited mobility on land, and in addition to the dash from the nest towards the sea as hatchlings, man sea turtles normally never ever leave the sea. Women must come back on to land to lay eggs. They move very gradually and laboriously, dragging themselves forwards using their flippers.

Behavior of Turtles

Senses of Turtles are thought to get exceptional night eyesight due to the unusually large quantity of rod cells in their retinas. Turtles have got color vision with a wealth of cone subtypes with sensitivities ranging from the near ultraviolet (UVA) to red. Some land turtles have very poor pursuit movement abilities, which usually are normally found just in predators that search quick-moving prey, but carnivorous turtles are able to move their heads rapidly to snap.

Turtles Communication

The particular Arrau turtle has the sizable vocal repertoire.

While typically thought of since mute, turtles make different sounds when communicating. Tortoises might be vocal when dating and mating. Various varieties of both freshwater plus sea turtles emit many types of calls, usually short and low frequency, from the time these are in the egg to whenever they are adults. These vocalizations may serve in order to create group cohesion whenever migrating.

Turtle Intelligence

See furthermore: Animal cognition

It provides been reported that wood turtles are better than white rats at understanding to navigate mazes. Situation studies exist of turtles playing. They do, however, possess a very low encephalization quotient (relative brain to body mass), and their particular hard shells enable these to live without fast reflexes or elaborate predator avoidance strategies. In the laboratory, turtles (Pseudemys nelsoni) can learn novel operant duties and have demonstrated a long lasting memory of at least 7. 5 months.

Turtle Mating Techniques

An instance of mounting behavior in turtles

Turtles are identified for displaying a broad variety of mating actions, however , they are not really known for forming pair-bonds or for being part of a social group. Once fertilization has happened and an offspring offers 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 Eco-friendly turtles), and thus, most males will participate in multiple copulation with multiple partners all through their lifespan. However, because of to the sexual dimorphism present in most turtle species, males must create different courting strategies or use alternate methods in order to gain access to any mate. Most terrestrial species have males that are usually bigger than females, and combating between males often decides a hierarchical order in which the higher up the order an person is, the better the chance is of the individual getting access to a potential mate. For many semi-aquatic species and bottom-walking aquatic species, combat occurs 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 aquatic species, males are frequently smaller than females and 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 group resort to using courtship displays in an try to gain mating entry to a female.

Fighting Between Males Turtles

Saddle back Galapagos tortoise

Wood turtles are an example of a terrestrial species where the males have a hierarchical ranking system based on dominance through fighting, and it's shown that the males with the highest rank and thus the most wins in battles have the most children.

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

Pressure Mating Turtles

Male (left) plus female (right) radiated tortoise

The male scorpion mud turtle is an example of a bottom-walking aquatic species that depends on overpowering females with its larger size as a mating strategy. The male methods the female from the back, and often resorts to aggressive methods for example biting the female's tail or even hind limbs, then a mounting behavior in which the male clasps the edges of her carapace with his forelimbs and hind limbs to hold the girl in position. The man 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 head into her shell. This unearths her cloaca, and along with it exposed, the male can attempt copulation simply by seeking to insert his grasping tail.

Male radiated tortoises may also be known to use the force mating strategy wherein they use surrounding vegetation to trap or even prevent females from getting away, then pin them lower for copulation.

Turtles Courtship Displays

Red-eared sliders are an example of a fully aquatic species where the male works 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 technique, and the females of a few species, such as eco-friendly sea turtles, aren't always receptive. As a result, they've progressed certain behaviors to avoid the male's attempts from copulation, such as swimming away, confronting the man followed by biting, or even a refusal position in which the female assumes a vertical position along with her limbs widely outspread and her plastron dealing with the male. If the particular water is too superficial to perform the refusal position, the females will certainly resort to beaching themselves, 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 several turtles spend large amounts of their lives marine, all turtles and tortoises breathe air and must surface at regular periods to refill their lungs. They can also spend much or all associated with their lives on dried out land. Aquatic respiration in Australian freshwater turtles is usually currently being studied. Some species have large cloacal cavities that are covered numerous finger-like projections. These types of projections, called papillae, have got a rich blood supply and improve the surface region of the cloaca. The turtles can take up dissolved oxygen from the particular water providing a few papillae, in much the same method that fish use gills to respire.

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

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

Researchers have lately uncovered a turtle's internal organs do not slowly but surely break down or become less efficient over time, unlike many other animals. It was found that the liver, lungs, and kidneys associated with a centenarian turtle are virtually indistinguishable from individuals of its immature equal. This has inspired hereditary researchers to start examining the turtle genome regarding longevity genes.

A team of turtles is known as a bale.

Turtles Diet

A green ocean turtle grazing on

A turtle's diet differs greatly determined by the atmosphere in which it lives. Mature turtles typically eat aquatic plants; (citation needed) invertebrates like insects, snails, and worms; and have already been reported to occasionally consume dead marine animals. A number of small freshwater species are usually carnivorous, eating small seafood and a wide variety of aquatic existence. However, protein is important to turtle growth plus juvenile turtles are solely carnivorous.

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

Systematics and evolution of Turtles

Major article: Turtle classification

See|Observe|Notice} also: List of Testudines family members

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

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

Centered on body fossils, the first proto-turtles are believed to have existed in the late Triassic Period of the Mesozoic era, regarding 220 million years ago, and their shell, which has remained a remarkably stable body plan, will be thought to have evolved through bony extensions of their particular backbones and broad ribs that expanded and grew together to form the complete shell that offered protection at every stage of its evolution, even when the bony element of the shell was not complete. This is supported by fossils of the particular freshwater Odontochelys semitestacea or even "half-shelled turtle with teeth", from the late Triassic, which have been found near Guangling in southwest China. Odontochelys displays the complete bony plastron and an incomplete carapace, similar to an early stage of turtle embryonic advancement. Just before this discovery, the earliest-known fossil turtle ancestors, like Proganochelys, were terrestrial together a complete covering, offering no clue in order to the evolution of this amazing anatomical feature. By the past due Jurassic, turtles had radiated widely, and their precious history becomes easier to go through.

Their precise ancestry provides been disputed. It was believed they are the only surviving branch associated with the ancient evolutionary quality Anapsida, which includes organizations like procolophonids, millerettids, protorothyrids, and pareiasaurs. All anapsid skulls lack a temporary opening while all additional extant amniotes have temporary openings (although in mammals, the hole has turn out to be the zygomatic arch). The millerettids, protorothyrids, and pareiasaurs became extinct in the particular late Permian period and the procolophonoids during the particular Triassic.

Nevertheless , it was later suggested that the anapsid-like turtle head might be due to reversion rather than to anapsid descent. More recent morphological phylogenetic studies with this in mind placed turtles firmly within diapsids, somewhat closer to Squamata in order to Archosauria.[55][56] All molecular studies possess strongly upheld the positioning of turtles within diapsids; some place turtles within 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 since the sister group of lepidosaurs instead. Reanalysis of earlier phylogenies suggests that these people classified turtles as anapsids both because they assumed this classification (most of all of them studying what sort associated with anapsid turtles are) and because they did not sample fossil and extant taxa broadly enough for constructing the cladogram. Testudines were suggested to get diverged from other diapsids among 200 and 279 mil years ago, though the particular debate is far from settled. Even the conventional placement of turtles outside Diapsida cannot be ruled out at this stage. A combined analysis associated with morphological and molecular information conducted by Lee (2001) found turtles to be anapsids (though a partnership with archosaurs couldn't end up being statistically rejected).[64] Similarly, a morphological study conducted by Lyson et al.. (2010) recovered them as anapsids most carefully related to Eunotosaurus. The molecular analysis of 248 nuclear genes from 16 vertebrate taxa suggests that turtles are a sister team to birds and crocodiles (the Archosauria).[66] The date of separation of turtles and birds and crocodiles was approximated to be 255 million in years past. The most latest common ancestor of residing turtles, corresponding towards the split between Pleurodira and Cryptodira, was estimated to have occurred around 157 million yrs ago. The oldest defined crown-group turtle (member of the modern clade Testudines) may be the species Caribemys oxfordiensis from your late Jurassic period (Oxfordian stage). Through utilizing the first genomic-scale phylogenetic analysis of ultraconserved elements (UCEs) to investigate the placement of turtles within reptiles, Crawford ainsi que al. (2012) also suggest that turtles are the sister group to wild birds and crocodiles (the Archosauria).

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

The earliest known completely shelled member of the turtle lineage is the particular late Triassic Proganochelys. This particular genus already possessed numerous advanced turtle traits, and thus probably indicates several millions of years of preceding turtle evolution; this particular is further supported simply 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 since early as the first Triassic. Proganochelys lacked the ability to draw its head into the shell, had a long neck, and had a long, spiked tail ending in a club. Could body form is similar to that of ankylosaurs, it resulted from convergent evolution.

Turtles are divided in to two extant suborders: Cryptodira and Pleurodira. The Cryptodira is the larger of the two groups and includes all the ocean turtles, the terrestrial tortoises, and lots of of the fresh water turtles. The Pleurodira are usually sometimes known as the particular side-necked turtles, a reference to the way they retract their own heads to their shells. This particular smaller group consists mainly of various freshwater turtles.