Importance of Carnivora
They seem to be very similar but just a more yellow than caramel colour. How large will your pet be? The process of ecdysis involves forming a new layer of skin under the old one. We put on the real movie and Alex was a happy camper for the next 3 hours. Whether you're new to breeding or an old seasoned hand, this book is sure to have something that will help you successfully incubate your valuable herps. The dinosaurs also developed smaller forms, including the feather-bearing smaller theropods. It is often also distinctly discolored compared to the rest of the body and may lack some of the external sculpting features seen in the original tail.
It was traditionally assumed that the first reptiles retained an anapsid skull inherited from their ancestors. These are the "mammal-like amniotes", or stem-mammals, that later gave rise to the true mammals. Turtles have been traditionally believed to be surviving parareptiles, on the basis of their anapsid skull structure, which was assumed to be primitive trait. With the close of the Carboniferous , the amniotes became the dominant tetrapod fauna. While primitive, terrestrial reptiliomorphs still existed, the synapsid amniotes evolved the first truly terrestrial megafauna giant animals in the form of pelycosaurs , such as Edaphosaurus and the carnivorous Dimetrodon.
In the mid-Permian period, the climate became drier, resulting in a change of fauna: The pelycosaurs were replaced by the therapsids.
The parareptiles, whose massive skull roofs had no postorbital holes, continued and flourished throughout the Permian. The pareiasaurian parareptiles reached giant proportions in the late Permian, eventually disappearing at the close of the period the turtles being possible survivors.
Early in the period, the modern reptiles, or crown-group reptiles , evolved and split into two main lineages: Both groups remained lizard-like and relatively small and inconspicuous during the Permian. The close of the Permian saw the greatest mass extinction known see the Permian—Triassic extinction event , an event prolonged by the combination of two or more distinct extinction pulses.
These were characterized by elongated hind legs and an erect pose, the early forms looking somewhat like long-legged crocodiles. The archosaurs became the dominant group during the Triassic period, though it took 30 million years before their diversity was as great as the animals that lived in the Permian. Since reptiles, first rauisuchians and then dinosaurs, dominated the Mesozoic era, the interval is popularly known as the "Age of Reptiles".
The dinosaurs also developed smaller forms, including the feather-bearing smaller theropods. In the Cretaceous period, these gave rise to the first true birds. The sister group to Archosauromorpha is Lepidosauromorpha , containing lizards and tuataras , as well as their fossil relatives. Lepidosauromorpha contained at least one major group of the Mesozoic sea reptiles: The phylogenetic placement of other main groups of fossil sea reptiles — the ichthyopterygians including ichthyosaurs and the sauropterygians , which evolved in the early Triassic — is more controversial.
Different authors linked these groups either to lepidosauromorphs  or to archosauromorphs,    and ichthyopterygians were also argued to be diapsids that did not belong to the least inclusive clade containing lepidosauromorphs and archosauromorphs. The close of the Cretaceous period saw the demise of the Mesozoic era reptilian megafauna see the Cretaceous—Paleogene extinction event.
Of the large marine reptiles, only sea turtles were left; and of the non-marine large reptiles, only the semi-aquatic crocodiles and broadly similar choristoderes survived the extinction, with the latter becoming extinct in the Miocene.
This dramatic extinction pattern at the end of the Mesozoic led into the Cenozoic. Mammals and birds filled the empty niches left behind by the reptilian megafauna and, while reptile diversification slowed, bird and mammal diversification took an exponential turn. After the extinction of most archosaur and marine reptile lines by the end of the Cretaceous, reptile diversification continued throughout the Cenozoic.
All squamates and turtles have a three-chambered heart consisting of two atria , one variably partitioned ventricle , and two aortas that lead to the systemic circulation. The degree of mixing of oxygenated and deoxygenated blood in the three-chambered heart varies depending on the species and physiological state. Under different conditions, deoxygenated blood can be shunted back to the body or oxygenated blood can be shunted back to the lungs. This variation in blood flow has been hypothesized to allow more effective thermoregulation and longer diving times for aquatic species, but has not been shown to be a fitness advantage.
Some squamate species e. This is made possible by a muscular ridge that subdivides the ventricle during ventricular diastole and completely divides it during ventricular systole. Because of this ridge, some of these squamates are capable of producing ventricular pressure differentials that are equivalent to those seen in mammalian and avian hearts.
Crocodilians have an anatomically four-chambered heart, similar to birds , but also have two systemic aortas and are therefore capable of bypassing their pulmonary circulation. Modern non-avian reptiles exhibit some form of cold-bloodedness i. Due to a less stable core temperature than birds and mammals , reptilian biochemistry requires enzymes capable of maintaining efficiency over a greater range of temperatures than in the case for warm-blooded animals.
As in all animals, reptilian muscle action produces heat. In large reptiles, like leatherback turtles , the low surface-to-volume ratio allows this metabolically produced heat to keep the animals warmer than their environment even though they do not have a warm-blooded metabolism.
The benefit of a low resting metabolism is that it requires far less fuel to sustain bodily functions. By using temperature variations in their surroundings, or by remaining cold when they do not need to move, reptiles can save considerable amounts of energy compared to endothermic animals of the same size. It is generally assumed that reptiles are unable to produce the sustained high energy output necessary for long distance chases or flying.
Energetic studies on some reptiles have shown active capacities equal to or greater than similar sized warm-blooded animals. All reptiles breathe using lungs. Aquatic turtles have developed more permeable skin, and some species have modified their cloaca to increase the area for gas exchange. Lung ventilation is accomplished differently in each main reptile group.
In squamates , the lungs are ventilated almost exclusively by the axial musculature. This is also the same musculature that is used during locomotion. Because of this constraint, most squamates are forced to hold their breath during intense runs. Some, however, have found a way around it. Varanids, and a few other lizard species, employ buccal pumping as a complement to their normal "axial breathing".
This allows the animals to completely fill their lungs during intense locomotion, and thus remain aerobically active for a long time. Tegu lizards are known to possess a proto- diaphragm , which separates the pulmonary cavity from the visceral cavity. While not actually capable of movement, it does allow for greater lung inflation, by taking the weight of the viscera off the lungs. Crocodilians actually have a muscular diaphragm that is analogous to the mammalian diaphragm.
The difference is that the muscles for the crocodilian diaphragm pull the pubis part of the pelvis, which is movable in crocodilians back, which brings the liver down, thus freeing space for the lungs to expand. This type of diaphragmatic setup has been referred to as the " hepatic piston ". The airways form a number of double tubular chambers within each lung. On inhalation and exhalation air moves through the airways in the same direction, thus creating a unidirectional airflow through the lungs.
A similar system is found in birds,  monitor lizards  and iguanas. Most reptiles lack a secondary palate , meaning that they must hold their breath while swallowing. Crocodilians have evolved a bony secondary palate that allows them to continue breathing while remaining submerged and protect their brains against damage by struggling prey. Skinks family Scincidae also have evolved a bony secondary palate, to varying degrees.
Snakes took a different approach and extended their trachea instead. Their tracheal extension sticks out like a fleshy straw, and allows these animals to swallow large prey without suffering from asphyxiation. How turtles and tortoises breathe has been the subject of much study.
To date, only a few species have been studied thoroughly enough to get an idea of how those turtles breathe. The varied results indicate that turtles and tortoises have found a variety of solutions to this problem. The difficulty is that most turtle shells are rigid and do not allow for the type of expansion and contraction that other amniotes use to ventilate their lungs. Some turtles, such as the Indian flapshell Lissemys punctata , have a sheet of muscle that envelops the lungs.
When it contracts, the turtle can exhale. When at rest, the turtle can retract the limbs into the body cavity and force air out of the lungs. When the turtle protracts its limbs, the pressure inside the lungs is reduced, and the turtle can suck air in. Turtle lungs are attached to the inside of the top of the shell carapace , with the bottom of the lungs attached via connective tissue to the rest of the viscera. By using a series of special muscles roughly equivalent to a diaphragm , turtles are capable of pushing their viscera up and down, resulting in effective respiration, since many of these muscles have attachment points in conjunction with their forelimbs indeed, many of the muscles expand into the limb pockets during contraction.
Breathing during locomotion has been studied in three species, and they show different patterns. Adult female green sea turtles do not breathe as they crutch along their nesting beaches.
They hold their breath during terrestrial locomotion and breathe in bouts as they rest. North American box turtles breathe continuously during locomotion, and the ventilation cycle is not coordinated with the limb movements. The last species to have been studied is the red-eared slider, which also breathes during locomotion, but takes smaller breaths during locomotion than during small pauses between locomotor bouts, indicating that there may be mechanical interference between the limb movements and the breathing apparatus.
Box turtles have also been observed to breathe while completely sealed up inside their shells. Reptilian skin is covered in a horny epidermis , making it watertight and enabling reptiles to live on dry land, in contrast to amphibians. Compared to mammalian skin, that of reptiles is rather thin and lacks the thick dermal layer that produces leather in mammals.
In lepidosaurians , such as lizards and snakes, the whole skin is covered in overlapping epidermal scales. Such scales were once thought to be typical of the class Reptilia as a whole, but are now known to occur only in lepidosaurians. Lacking a thick dermis, reptilian leather is not as strong as mammalian leather. It is used in leather-wares for decorative purposes for shoes, belts and handbags, particularly crocodile skin.
Reptiles shed their skin through a process called ecdysis which occurs continuously throughout their lifetime. In particular, younger reptiles tend to shed once every 5—6 weeks while adults shed times a year.
Once full size, the frequency of shedding drastically decreases. The process of ecdysis involves forming a new layer of skin under the old one. Proteolytic enzymes and lymphatic fluid is secreted between the old and new layers of skin. Consequently, this lifts the old skin from the new one allowing shedding to occur. Traumatic injuries on the other hand, form scars that will not allow new scales to form and disrupt the process of ecdysis.
Excretion is performed mainly by two small kidneys. In diapsids, uric acid is the main nitrogenous waste product; turtles, like mammals , excrete mainly urea. Unlike the kidneys of mammals and birds, reptile kidneys are unable to produce liquid urine more concentrated than their body fluid. This is because they lack a specialized structure called a loop of Henle , which is present in the nephrons of birds and mammals. Because of this, many reptiles use the colon to aid in the reabsorption of water.
Some are also able to take up water stored in the bladder. Excess salts are also excreted by nasal and lingual salt glands in some reptiles. In all reptiles the urinogenital ducts and the anus both empty into an organ called a cloaca. In some reptiles, a midventral wall in the cloaca may open into a urinary bladder, but not all. It is present in all turtles and tortoises as well as most lizards, but is lacking in the monitor lizard , the legless lizards.
It is absent in the snakes, alligators, and crocodiles. Many turtles, tortoises, and lizards have proportionally very large bladders. Turtles have two or more accessory urinary bladders, located lateral to the neck of the urinary bladder and dorsal to the pubis, occupying a significant portion of their body cavity.
The right section is located under the liver, which prevents large stones from remaining in that side while the left section is more likely to have calculi.
Most reptiles are insectivorous or carnivorous and have simple and comparatively short digestive tracts due to meat being fairly simple to break down and digest. Digestion is slower than in mammals , reflecting their lower resting metabolism and their inability to divide and masticate their food.
While modern reptiles are predominantly carnivorous, during the early history of reptiles several groups produced some herbivorous megafauna: Herbivorous reptiles face the same problems of mastication as herbivorous mammals but, lacking the complex teeth of mammals, many species swallow rocks and pebbles so called gastroliths to aid in digestion: The rocks are washed around in the stomach, helping to grind up plant matter.
The reptilian nervous system contains the same basic part of the amphibian brain, but the reptile cerebrum and cerebellum are slightly larger.
Most typical sense organs are well developed with certain exceptions, most notably the snake 's lack of external ears middle and inner ears are present. There are twelve pairs of cranial nerves. Reptiles are generally considered less intelligent than mammals and birds. Larger lizards, like the monitors , are known to exhibit complex behavior, including cooperation.
The Komodo dragon is even known to engage in play,  as are turtles, which are also considered to be social creatures, [ citation needed ] and sometimes switch between monogamy and promiscuity in their sexual behavior. Most reptiles are diurnal animals. The vision is typically adapted to daylight conditions, with color vision and more advanced visual depth perception than in amphibians and most mammals.
In some species, such as blind snakes , vision is reduced. Some snakes have extra sets of visual organs in the loosest sense of the word in the form of pits sensitive to infrared radiation heat. Such heat-sensitive pits are particularly well developed in the pit vipers , but are also found in boas and pythons. These pits allow the snakes to sense the body heat of birds and mammals, enabling pit vipers to hunt rodents in the dark. Reptiles generally reproduce sexually , though some are capable of asexual reproduction.
Most reptiles have copulatory organs , which are usually retracted or inverted and stored inside the body. In turtles and crocodilians, the male has a single median penis , while squamates, including snakes and lizards, possess a pair of hemipenes , only one of which is typically used in each session.
Tuatara, however, lack copulatory organs, and so the male and female simply press their cloacas together as the male discharges sperm. Most reptiles lay amniotic eggs covered with leathery or calcareous shells. An amnion , chorion , and allantois are present during embryonic life. The eggshell 1 protects the crocodile embryo 11 and keeps it from drying out, but it is flexible to allow gas exchange. The chorion 6 aids in gas exchange between the inside and outside of the egg.
It allows carbon dioxide to exit the egg and oxygen gas to enter the egg. The albumin 9 further protects the embryo and serves as a reservoir for water and protein. The allantois 8 is a sac that collects the metabolic waste produced by the embryo.
Founder and President of the International Crocodile Society. Biography by Hylander, C. He received many honorary degrees and continued writing until close to his death. He was impatient of careless work and generalizations based on insufficient data. Autobiographical notes and bibliography, Field Museum Library.
XYZ Return to Names main page. Copyright and all rights reserved by Ellin Beltz, One general cause of dystocia may be due to the inability of the eggs to pass through the oviduct and cloaca. There may be an obstruction, the eggs may be too large or malpositioned, the pelvis may be misshapen, or there may be obstructive masses such as abscesses or cystic calculi.
Two or more eggs may be bound together, or a single egg may be exceptionally large or misshapen. Dystocias can occur in the absence of obstructions or malformations. It is theorized that such retentions may be the result of one or more factors including poor husbandry, improper nesting site, improper temperatures, poor or inadequate diet malnutrition , dehydration, and poor physical condition of the female.
This latter is easily caused in, and remedied, in captivity. Captive reptiles lead a very sedentary lifestyle compared to their wild counterparts, thus lack the muscle strength or tone to get all the eggs into position for laying and expelling them in a timely matter from first egg to last. It is not uncommon, for example, for the last egg or two to be retained despite the successful and apparent ease with which the rest of the clutch was expelled by oviparous snakes.
In my experience, egg-binding in iguanas happens most frequently to females who are enclosed in cages that do not allow for sufficient climbing, being either too short or they are fed at their basking sites and often physically removed by the owner for defecation elsewhere.
Iguanas housed in enclosures at least ft high and who must climb up and down for eating, drinking and defecation appear to have fewer incidences of dystocia. Snakes In smaller snakes, recent oviposition the repositioning of the eggs prior to laying and the visible appearance of the swelling caused by the mass of eggs is a clue to the presence of eggs.
In larger species such as pythons, eggs, especially retained eggs, are more difficult to see. It is more difficult to determine the retention of fetuses especially since entire clutches may be retained rather than just a few. Prolonged laying or birthing efforts and cloacal or oviductal prolapse eversion of cloacal or oviductal tissue through the vent are other signs of dystocia.
Recently, improved ultrasonography techniques have been successfully used to determine the viability of fetuses in viviparous snakes, enabling the veterinarian to take the steps necessary to alleviate the situation by removing the nonviable tissue.
Lizards The most common cause of dystocia in lizards is the absence of a suitable nesting site and media. A lizard progressing normally through the period of carrying gestating eggs or fetus will not be eating, but will be alert and active.
Their usually physical grace may be compromised, especially as their lower half becomes swollen with the developing eggs or fetuses, but they are able to move around, climbing and roosting as usual.
A lizard suffering from dystocia, on the other hand, will become lethargic, depressed, nonresponsive. If the laying media is not of the right consistency, the lizard may spend hours kicking the dirt out, then wandering around, making digging attempts almost anywhere. This latter activity is more frenzied, and the lizard grows weaker and more visibly stressed, as the pressure to lay the eggs mounts. Straining may be seen, as may the prolapse of cloacal or oviductal tissue.
Lizards can tolerate dystocias for considerably less time than can snakes, often only a matter of days, and so should be evaluating medically soon after such signs are observed. Many lizards can produce and lay eggs, just as can chickens and humans, without being mated.
Chelonians Egg masses are all but impossible to detect by the inexperienced, and the presence of one or two retained eggs may not be felt even then. Retention is very difficult to detect in chelonians due to their being hidden not only within the turtle or tortoise's body, but the whole covered by the shell.