Sea Turtles Protection Guidelines
Turtles are diapsids of the particular order Testudines (or Chelonii) seen as a a special bony or cartilaginous shell created from their ribs plus acting as a shield. "Turtle" may refer to the order as a whole (American English) or even to fresh-water and sea-dwelling testudines (British English). The particular order Testudines includes both extant (living) and vanished species. The earliest known members of this group date from 220 million years ago, making turtles one of the earliest reptile groups and the more ancient group than snakes or crocodilians. Associated with the 356 known species alive today, some are 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 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 numerous species live in or around water. The research of turtles is called cheloniology, after the Greek word for turtle. It is usually also sometimes called testudinology, after the Latin name for turtles.
Differences exist in usage of the common terms turtle, tortoise, and terrapin, depending on the variety of English being utilized. These terms are typical names and don't reflect precise biological or taxonomic distinctions.
Turtle may either recommend to the order since a whole, or to particular turtles that create up a form taxon that is not monophyletic, or might be limited to only marine species. Tortoise usually refers to any land-dwelling, non-swimming chelonian. Terrapin can be used to describe several species of small, edible, hard-shell turtles, typically those found within brackish waters.
In North America, all chelonians are commonly called turtles. Tortoise is used only in reference to 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 fresh and brackish water, particularly the diamondback terrapin (Malaclemys terrapin). Although the users from the genus Terrapene live mostly on land, these people are known as box turtles rather than tortoises. The particular American Society of Ichthyologists and Herpetologists uses "turtle" to describe all types of the order Testudines, whether or not they are land-dwelling or sea-dwelling, and uses "tortoise" as a more specific term for slow-moving terrestrial species.
In the United Empire, the term turtle is used for water-dwelling species, including ones known in the US as terrapins, but not for terrestrial species, that are known only as tortoises.
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Types of Turtles Giant Tortoise Reptile Gardens Reptile Gardens
The word chelonian will be well-liked by veterinarians, scientists, and conservationists working with these animals like a catch-all name for any person in the superorder Chelonia, including all turtles living and extinct, as well as their 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 hand, is based on the particular Latin word for tortoise, testudo. Terrapin comes from an Algonquian word for turtle.
Some languages do not have this variation, as all of these are referred to by the particular same name. For example , within Spanish, the word tortuga is used for turtles, tortoises, and terrapins. A sea-dwelling turtle is tortuga marina, a freshwater types tortuga de río, plus a tortoise tortuga terrestre.
The largest living chelonian is the leatherback ocean turtle (Dermochelys coriacea), which reaches a shell duration of 200 cm (6. six ft) and can achieve a weight of more than 900 kg (2, 1000 lb). Freshwater turtles are usually generally smaller, but 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 largest chelonian in North The united states, which attains a shell length of up in order to 80 cm (2. 6 ft) and weighs as much as 113. four kg (250 lb).
Giant tortoises of the overal Geochelone, Meiolania, and other people were relatively widely distributed all over the world into prehistoric occasions, and they are known to have existed in North plus South America, Australia, plus Africa. They became vanished at the same time as the appearance associated with man, and it is usually assumed humans hunted all of them for food. The only surviving giant tortoises are on the Seychelles and Galápagos Islands and can grow to over 130 centimeter (51 in) in size, and weigh about 300 kg (660 lb).
The largest ever chelonian has been Archelon ischyros, a Past due Cretaceous sea turtle recognized to have been as much as 4. 6 m (15 ft) long.
Facts Discovery Sea Turtle Exploration
The tiniest turtle is the speckled padloper tortoise of South Africa. It measures simply 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 particular American mud turtles plus musk turtles that reside in an area that will ranges from Canada in order to South America. The shell duration of many species in this group is much less than 13 cm (5. 1 in) long.
Turtles are divided into 2 groups, according to the way they retract their necks to their shells (something the our ancestors Proganochelys could not do). The mechanism of neck retraction differs phylogenetically: the particular suborder Pleurodira retracts laterally to the side, anterior to glenohumeral joint girdles, while the suborder Cryptodira retracts straight back again, between shoulder girdles. These types of motions are largely because of to the morphology and arrangement of cervical backbone. Of all recent turtles, the cervical column consists of nine joints and eight vertebrae, which are individually independent. Since these vertebrae are not fused and are rounded, the particular neck is more versatile, being able to flex in the backwards plus sideways directions. The main function and evolutionary implication of neck retraction is thought to be regarding feeding rather than security. Neck retraction and reciprocal extension allows the turtle to reach out further in order to capture prey while going swimming. Neck expansion creates suction when the head is drive forward and the oropharynx is expanded, and this particular morphology suggests the retraction function is for nourishing purposes as the suction helps catch prey. The particular protection the shell offers the head when this is retracted is consequently not the main functionality of retraction, thus is an exaptation. As for the difference between the particular two methods of retraction, both Pleurodirans and Cryptodirans use the quick extension of the neck being a method of predation, therefore the difference in retraction mechanism is just not due to a difference in environmental niche.
Head
Most turtles that spend most associated with their lives on property get their eyes looking lower at objects in front of them. Some aquatic turtles, such as snapping turtles and soft-shelled turtles, have eyes closer in order to the very best of the head. These types of turtle may hide from predators in shallow water, where these people lie entirely submerged except for their eyes and nostrils. Near their eyes, sea turtles possess intrigue that produce salty holes that rid themselves associated with excess salt consumed through the water they consume.
Turtles have rigid beaks and use their jaws to cut and munch food. Instead of getting teeth, that they appear to have lost about 150-200 million years ago, the upper and lower jaws of the turtle are usually covered by horny side rails. Carnivorous turtles usually have knife-sharp ridges for slicing through their prey. Herbivorous turtles have serrated-edged side rails that help them reduce through tough plants. They use their tongues to swallow food, but in contrast to most reptiles, they can not stick out their tongues to catch food.
ShellMain article: Turtle shellThe top shell of the turtle is known as the carapace. The particular 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 bone fragments 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 by horny scales called scutes that are part of its outer skin, or epidermis. Scutes are made up of the particular fibrous protein keratin that will also makes up the scales of other lizards. These scutes overlap the seams between the shell bones and add power towards the shell. Some turtles don’t have horny scutes; regarding example, the leatherback ocean 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. Many tortoises have a big, dome-shaped shell that makes it difficult for predators to crush the cover between their jaws. One of the few conditions is the African hot cake tortoise, which has the flat, flexible shell that will allows it to hide in rock crevices. The majority of aquatic turtles have flat, streamlined shells, which aid within swimming and diving. American snapping turtles and musk turtles have small, cross-shaped plastrons that give all of them more efficient leg motion for walking along the particular bottom of ponds and streams. Another exception is usually 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, fruit, yellow, or grey marks, often spots, lines, or irregular blotches. Probably the most colorful turtles is the eastern painted turtle, which includes a yellow plastron and a black or olive shell with red markings around the rim.
Tortoises, being land-based, have instead 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 agility. These lighter shells have got large spaces called fontanelles between the shell bones. The shells of leatherback sea turtles are extremely gentle because they lack scutes and contain many fontanelles.
It has been suggested by Jackson (2002) that will the turtle shell can function as pH barrier. To endure through anoxic conditions, such as winter periods trapped beneath glaciers 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 been shown the turtle shell both releases carbonate buffers and uptakes lactic acid solution.
River Turtle Life of Sea
Breathing Turtles
Respiration, for many amniotes, is achieved by the particular contraction and relaxation associated with specific muscles (i. electronic. intercostals, abs, and/or the diaphragm) attached to an inner rib-cage that can expand or contract the entire body wall thus assisting air flow out and in of the lung area. The ribs of Chelonians, however, are fused along with their carapace and external to their pelvic and pectoral girdles, a function unique among turtles. This particular rigid shell is not really capable of expansion, and 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 is drawn in via the negative pressure gradient (Boyle's Law). In expiration, the particular contraction of the transversus abdominis is the driving force by propelling the viscera into the lungs and expelling air under positive pressure. Conversely, the relaxing and flattening of the oblique abdominis muscle drags the transversus back down which, once more, draws air flow back into the lung area. Important auxiliary muscles utilized for ventilatory processes would be the pectoralis, which is utilized in conjunction with the particular transverse abdominis during motivation, as well as the serratus, which moves with the abdominal oblique accompanying expiration.
The lungs of Testudines are multi-chambered plus attached their entire duration down the carapace. The number of chambers can differ among taxa, though most often they have three lateral compartments, three medial chambers, and something terminal chamber. As mentioned earlier on, the act of particular abdominal muscles pulling lower the viscera (or pressing back up) is exactly what allows for respiration in 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 connected 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 with the ventral mesentery. When the liver is pulled down, inspiration begins. Helping the lungs is the particular post-pulmonary septum, which is found in all Testudines, and it is thought to prevent the particular lungs from collapsing.
Facts about turtles!
Turtles Pores and skin and molting
As mentioned above, the outer level of the shell will be part of the skin; each scute (or plate) on the shell corresponds to a single revised scale. The remainder associated with the skin has a lot smaller scales, like the pores and skin of other reptiles. Turtles do not molt their particular 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 in order to be a thin item of plastic) having been sloughed off when the particular animals deliberately rub by themselves against some wood or even stone. Tortoises also lose skin, but dead epidermis is permitted to accumulate into thick knobs and plates that provide protection in order to parts of the entire body outside the shell.
Simply by counting the rings created by the stack associated with smaller, older scutes along with the larger, newer types, you are able to estimate the age of a turtle, if one knows the number of scutes are produced in per year. This method is not really very accurate, partly due to the fact 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 well-known for moving slowly, in part because of their large, cumbersome shells, which restrict stride length.
Skeleton associated with snapping turtle (Chelydra serpentina)
Amphibious turtles normally possess limbs similar to those of tortoises, except that the particular feet are webbed plus often have long paws. These turtles swim making use of all four feet in a way similar in order to the dog paddle, along with the feet on the left and right side of the body alternately providing thrust. Large turtles tend in order to swim less than smaller ones, and the really big species, such as alligator snapping turtles, barely swim whatsoever, preferring in order to walk across the bottom associated with the river or lake. As well as webbed feet, turtles have extremely long claws, used in order to help them clamber onto riverbanks and floating records upon which they bask. Male turtles tend to have particularly long claws, and these appear to be used to stimulate the woman while mating. While the majority of turtles have webbed ft, some, such as the pig-nosed turtle, have true flippers, along with the digits being fused into paddles and the claws being relatively small. These species swim in the same way since sea turtles do (see below).
Sea turtles are usually almost entirely aquatic plus have flippers instead associated with feet. Sea turtles fly with the water, using the particular up-and-down motion of the particular front flippers to create thrust; the back feet are not used for propulsion yet can be utilized as rudders with regard to steering. Compared with freshwater turtles, sea turtles have very limited mobility on land, and in addition to the dash from the nest to the sea as hatchlings, male sea turtles normally never leave the sea. Women must come back on to land to lay ovum. They move very slowly and laboriously, dragging by themselves forwards using their flippers.
Habits of Turtles
Senses of Turtles are thought to get exceptional night eyesight due to the unusually large number of rod cells within their retinas. Turtles have 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 only in predators that hunt quick-moving prey, but carnivorous turtles are able in order to move their heads quickly to snap.
Turtles Communication
The Arrau turtle has a sizable vocal repertoire.
While typically thought of since mute, turtles make different sounds when communicating. Tortoises may be vocal when dating and mating. Various species of both freshwater plus sea turtles emit many types of calls, frequently short and low rate of recurrence, from the time these are in the egg in order to if they are adults. These vocalizations may serve in order to create group cohesion when migrating.
Turtle Cleverness
See furthermore: Animal cognition
It provides been reported that wood turtles are better compared to white rats at understanding to navigate mazes. Situation studies exist of turtles playing. They do, however, have got a very low encephalization quotient (relative brain in order to body mass), and their own hard shells enable them 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 Methods
An instance of mounting behavior in turtles
Turtles are known for displaying a broad variety of mating behaviors, nevertheless , they are not known for forming pair-bonds or for being component of a social team. Once fertilization has occurred and an offspring provides been produced, neither parent will provide care with regard to the offspring once is actually hatched. Females generally outnumber males in various turtle species (such as Green turtles), and thus, most men will take part in multiple copulation with multiple partners all through their lifespan. However, because of to the sexual dimorphism present in most turtle species, males must develop different courting strategies or use alternate methods in order to gain access to a potential mate. Most terrestrial types have males that are usually bigger than females, and battling between males often establishes a hierarchical order in which the higher upward the order an individual is, the better the particular chance is of the person 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 use their larger size advantage to forcibly mate having a female. In fully aquatic species, males are usually smaller than females plus therefore they can not use the same strategy as their semi-aquatic relatives, which depends on overpowering the females with power. Males in this class resort to using courtship displays in an attempt to gain mating accessibility to a female.
Combating Between Males Turtles
Saddle back Galapagos tortoise
Wood turtles is surely an example of a terrestrial species where the males have a hierarchical ranking system based upon dominance through fighting, plus it's shown that the males with the maximum rank and thus the most wins in battles have the most children.
Galapagos tortoises are one more example of a varieties which has a hierarchical rank which is determined by dominance displays, and access to food and partners is regulated by this particular dominance hierarchy. Two male saddle backs most frequently compete for access to cactus trees, that is their own source of food. The winner is the individual who stretches their throat the highest, which individual gets access to the cactus tree, which may attract potential mates.
Pressure Mating Turtles
Male (left) plus female (right) radiated tortoise
The male scorpion dirt turtle is an example of a bottom-walking marine species that relies on overpowering females with its larger size as a mating strategy. The male techniques the feminine from the back, and often resorts to aggressive methods like gnawing at the female's tail or hind limbs, then a mounting behavior in which usually the male clasps the edges of her carapace with his forelimbs and hind limbs to hold her in position. The male follows this action simply by laterally waving his head and sometimes biting the female's head in a good attempt to get the girl to withdraw her go to her shell. This unearths her cloaca, and along with it exposed, the male can attempt copulation simply by wanting to insert his holding tail.
Male radiated tortoises will also be known to make use of the force mating technique wherein they use surrounding vegetation to trap or prevent females from getting away, then pin them lower for copulation.
Turtles Courtship Shows
Red-eared sliders are an sort of a fully aquatic species where the male works a courtship behavior. In this case the male extends his forelegs with 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 green sea turtles, aren't always receptive. As a result, they've evolved certain behaviors to avoid the male's attempts at copulation, such as going swimming away, confronting the man followed by biting, or a refusal position within which the female assumes a vertical position with her limbs widely outspread and her plastron dealing with the male. If the water is too superficial to perform the refusal position, the females may resort to beaching on their own, which is a verified deterrent method, as the particular males will not follow all of them ashore.
Ecology and life history of turtles
Sea turtle swimming
Although many turtles spend large amounts of their lives marine, all turtles and tortoises breathe air and must surface at regular time periods to refill their lung area. They can also invest much or all of their lives on dried out land. Aquatic respiration within Australian freshwater turtles will be currently being studied. Some species have large cloacal cavities that are lined numerous finger-like projections. These projections, called papillae, have a rich blood supply and increase the surface region of the cloaca. The turtles can take upward dissolved oxygen from the particular water providing a few papillae, within much the same method that fish use gills to respire.
Like other reptiles, turtles lay ovum that are slightly soft and leathery. The eggs from the major species are spherical while the ovum of the rest are usually elongated. Their albumen is usually white and contains a different protein from bird ovum, such that it will certainly not coagulate when cooked. Turtle eggs prepared to eat consist mainly of yolk. In some species, temperature determines whether an egg cell develops into a man or perhaps a female: a increased temperature causes a female, the lower temperature the man. Large numbers of ovum are deposited in holes dug into mud or 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. When the turtles hatch, they squirm their way to the surface and head against the water. There are no known species in which the mom cares for her young.
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 years to achieve breeding age, plus in many cases, breed every few years rather than annually.
Researchers have lately learned a turtle's internal organs tend not to gradually break down or become less efficient over time, unlike most other animals. It had been found that the liver, lungs, and kidneys associated with a centenarian turtle are usually almost indistinguishable from those of its immature equal. This has inspired genetic researchers to get started evaluating the turtle genome for longevity genes.
A team of turtles is known as a bale.
Turtles Diet
A green sea turtle grazing on
A turtle's diet varies greatly determined by the atmosphere by which it lives. Adult turtles typically eat aquatic plants; (citation needed) invertebrates such as insects, snails, plus worms; and have already been reported to occasionally consume dead marine animals. Several small freshwater species are carnivorous, eating small fish and many aquatic existence. However, protein is essential to turtle growth plus juvenile turtles are solely carnivorous.
Sea turtles generally feed on jellyfish, sponges, and other soft-bodied microorganisms. Some species with more powerful jaws have been noticed to eat shellfish, while others, including the green ocean turtle, do not eat meat at all plus, instead, possess a diet mainly made up of algae.
Systematics and evolution of Turtles
Main article: Turtle classification
See|Observe|Notice} also: List of Testudines households
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 particular first proto-turtles are believed to have existed in the particular late Triassic Period associated with the Mesozoic era, about 220 million years ago, and their shell, which has remained a remarkably stable body plan, will be considered to have evolved through bony extensions of their backbones and broad steak that expanded and grew together to form a complete shell that provided protection at every phase of its evolution, even when the bony element of the shell was not really complete. This is supported by fossils of the freshwater Odontochelys semitestacea or even "half-shelled turtle with teeth", from the late Triassic, which have been discovered near Guangling in southwest China. Odontochelys displays the complete bony plastron and an incomplete carapace, similar to an early stage of turtle embryonic growth. Prior to this discovery, the earliest-known fossil turtle ancestors, like Proganochelys, were terrestrial together a complete shell, offering no clue to the evolution of the exceptional anatomical feature. By the late Jurassic, turtles had radiated widely, and their fossil history becomes simpler to study.
Their specific ancestry offers been disputed. It has been believed they are the particular only surviving branch associated with the ancient evolutionary quality Anapsida, which includes organizations such as procolophonids, millerettids, protorothyrids, and pareiasaurs. All anapsid skulls lack a temporary opening while all other extant amniotes have temporary openings (although in mammals, the hole has become the zygomatic arch). The millerettids, protorothyrids, and pareiasaurs became extinct in the particular late Permian period plus the procolophonoids during the Triassic.
Nevertheless , 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 have got strongly upheld the placement 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 conducted by Lyson et al. (2012) recovered turtles since the sister group of lepidosaurs instead. Reanalysis of before phylogenies suggests that they will classified turtles as anapsids both because they assumed this classification (most of them studying what sort of anapsid turtles are) plus because they did not sample fossil and extant taxa broadly enough with regard to constructing the cladogram. Testudines were suggested to have diverged from other diapsids among 200 and 279 mil years ago, though the debate is far through settled. Even the conventional placement of turtles outdoors Diapsida cannot be ruled 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 shows that turtles are a sister team to birds and crocodiles (the Archosauria).[66] The date of splitting up of turtles and wild birds and crocodiles was estimated to be 255 million years ago. The most recent common ancestor of residing turtles, corresponding towards the split between Pleurodira and Cryptodira, was estimated to get happened around 157 million years ago. The oldest definitive crown-group turtle (member of the modern clade Testudines) is the species Caribemys oxfordiensis through the 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 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 group used the largest turtle information set to date in their analysis and concluded that turtles are likely a sister group of crocodilians and birds (Archosauria). This placement within the diapsids suggests that the turtle lineage lost diapsid skull characteristics as it 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, plus thus probably indicates many millions of years of preceding turtle evolution; this is further supported simply by evidence from fossil paths from the Early Triassic of the United Says (Wyoming and Utah) plus from the Middle Triassic of Germany, indicating that will proto-turtles already existed since early as the first Triassic. Proganochelys lacked the opportunity to pull its head into its shell, had a lengthy neck, and had the long, spiked tail ending in a club. Could body form is comparable to those 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 sea turtles, the terrestrial tortoises, and many of the fresh water turtles. The Pleurodira are usually sometimes known as the side-necked turtles, a guide to how they retract their particular heads into their shells. This particular smaller group consists primarily of various freshwater turtles.