Komodo Reptile Scales

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Main article: Evolution of reptiles Origin of the reptiles [ edit ] An early reptile Hylonomus Mesozoic scene showing typical reptilian megafauna: dinosaurs including Europasaurus holgeri, iguanodonts, and Archaeopteryx lithographica perched on the foreground tree stump Russell, Anthony P.; Bauer, Aaron M. (2020). "Vocalization by extant nonavian reptiles: A synthetic overview of phonation and the vocal apparatus". The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology. 304 (7): 1478–1528. doi: 10.1002/ar.24553. PMID 33099849. S2CID 225069598. Reptiles are mainly animals of Earth’s temperate and tropical regions, and the greatest number of reptilian species live between 30° N and 30° S latitude. Nevertheless, at least two species, the European viper ( Vipera berus) and the common, or viviparous, lizard ( Lacerta vivipara, also called Zootoca vivipara), have populations that edge over the Arctic Circle (66°33′39″ N latitude). Other species of snakes, lizards, and turtles also live at high latitudes and altitudes and have evolved lifestyles that allow them to survive and reproduce with little more than three months of activity each year. Huxley, T.H. (1863). "The structure and classification of the Mammalia". Medical Times and Gazette. Hunterian lectures.

Cieri, Robert L.; Craven, Brent A.; Schachner, Emma R.; Farmer, C.G. (2014). "New insight into the evolution of the vertebrate respiratory system and the discovery of unidirectional airflow in iguana lungs". Proceedings of the National Academy of Sciences. 111 (48): 17218–17223. Bibcode: 2014PNAS..11117218C. doi: 10.1073/pnas.1405088111. PMC 4260542. PMID 25404314. Campbell, N.A. & Reece, J.B. (2006): Outlines & Highlights for Essential Biology. Academic Internet Publishers. 396 pp. ISBN 978-0-8053-7473-5 Scales mostly consist of hard beta keratins which are basically transparent. The colours of the scale are due to pigments in the inner layers of the skin and not due to the scale material itself. Scales are hued for all colours in this manner except for blue and green. Blue is caused by the ultrastructure of the scales. By itself, such a scale surface diffracts light and gives a blue hue, while, in combination with yellow from the inner skin it gives a beautiful iridescent green. The synapsid/sauropsid division supplemented another approach, one that split the reptiles into four subclasses based on the number and position of temporal fenestrae, openings in the sides of the skull behind the eyes. This classification was initiated by Henry Fairfield Osborn and elaborated and made popular by Romer's classic Vertebrate Paleontology. [16] [17] Those four subclasses were:

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a b c d e f g h Modesto, S.P.; Anderson, J.S. (2004). "The phylogenetic definition of Reptilia". Systematic Biology. 53 (5): 815–821. doi: 10.1080/10635150490503026. PMID 15545258. The origin of the reptiles lies about 310–320 million years ago, in the steaming swamps of the late Carboniferous period, when the first reptiles evolved from advanced reptiliomorphs. [33] [ failed verification]

Only three reptile species, including the yellow-bellied three-toed skink of Australia, actually combine both eggs and live birthing methods (the rarity suggests that evolution probably does not favor this in-between stage). The skink’s offspring begins life encased in an egg, the same as any other reptile. But as the embryo develops, the egg begins to thin out until all that’s left upon its birth is a small membrane. The main problem with this method is that the thin egg shells don’t contain enough calcium to nourish the offspring. The mothers appear to compensate for this by secreting calcium from the uterus so it can be absorbed by the developing embryo. The evidence suggests that the skink can choose to lay eggs a few weeks early if it seems like there’s less danger to the offspring. In harsher climates, the mother will keep the offspring insider her body for longer to protect them. Paré, Jean (11 January 2006). Reptile basics: Clinical anatomy101 (PDF). North American Veterinary Conference. Vol.20. pp.1657–1660. Molnar, Ralph E. (2004). Dragons in the Dust: The paleobiology of the giant monitor lizard Megalania. Bloomington: Indiana University Press. ISBN 978-0-253-34374-1. Gray, Brian S. (2005) The Serpent's Cast: A Guide to the Identification of shed skins from snakes of the Northeast and Mid-Atlantic States. The Center for North American Herpetology Monograph Series no. 1.Serpent's Tale Natural History Book Distributors, Lanesboro, Minnesota. Many lepidosaurs have a photosensory organ on the top of their heads called the parietal eye, which are also called third eye, pineal eye or pineal gland. This "eye" does not work the same way as a normal eye does as it has only a rudimentary retina and lens and thus, cannot form images. It is, however, sensitive to changes in light and dark and can detect movement. [112]For example, Iguanahearts, like the majority of the squamateshearts, are composed of three chambers with two aorta and one ventricle, cardiac involuntary muscles. [68] The main structures of the heart are the sinus venosus, the pacemaker, the left atrium, the right atrium, the atrioventricular valve, the cavum venosum, cavum arteriosum, the cavum pulmonale, the muscular ridge, the ventricular ridge, pulmonary veins, and paired aortic arches. [69] There is evidence that reptiles are sentient and able to feel emotions including anxiety and pleasure. [130] Defense mechanisms [ edit ] Turtles have been traditionally believed to be surviving parareptiles, on the basis of their anapsid skull structure, which was assumed to be primitive trait. [49] The rationale for this classification has been disputed, with some arguing that turtles are diapsids that evolved anapsid skulls, improving their armor. [33] Later morphological phylogenetic studies with this in mind placed turtles firmly within Diapsida. [50] All molecular studies have strongly upheld the placement of turtles within diapsids, most commonly as a sister group to extant archosaurs. [24] [25] [26] [27] Permian reptiles [ edit ] In the 13th century the category of reptile was recognized in Europe as consisting of a miscellany of egg-laying creatures, including "snakes, various fantastic monsters, lizards, assorted amphibians, and worms", as recorded by Beauvais in his Mirror of Nature. [6] 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. [105] Their poikilotherm metabolism has very low energy requirements, allowing large reptiles like crocodiles and large constrictors to live from a single large meal for months, digesting it slowly. [78]

Spotila, J.R.; O'Connor, M.P.; Dodson, P.; Paladino, F.V. (1991). "Hot and cold running dinosaurs: body size, metabolism and migration". Modern Geology. 16: 203–227. Regular shedding – Reptiles shed their skin continuously throughout their lifetimes. Shedding tends to be the most frequent during the adolescent phase, because the skin doesn’t actually grow in proportion with the body. The frequency of the shedding tends to decrease once the reptile reaches adulthood. At that point it’s mostly shed to maintain good health. The terms Sauropsida ("lizard faces") and Theropsida ("beast faces") were used again in 1916 by E.S. Goodrich to distinguish between lizards, birds, and their relatives on the one hand (Sauropsida) and mammals and their extinct relatives (Theropsida) on the other. Goodrich supported this division by the nature of the hearts and blood vessels in each group, and other features, such as the structure of the forebrain. According to Goodrich, both lineages evolved from an earlier stem group, Protosauria ("first lizards") in which he included some animals today considered reptile-like amphibians, as well as early reptiles. [12]Cisneros, Juan C.; Damiani, Ross; Schultz, Cesar; daRosa, Átila; Schwanke, Cibele; Neto, Leopoldo W.; Aurélio, Pedro L.P. (2004). "A procolophonoid reptile with temporal fenestration from the middle Triassic of Brazil". Proceedings of the Royal Society B. 271 (1547): 1541–1546. doi: 10.1098/rspb.2004.2748. PMC 1691751. PMID 15306328. a b Zardoya, R.; Meyer, A. (1998). "Complete mitochondrial genome suggests diapsid affinities of turtles". Proceedings of the National Academy of Sciences USA. 95 (24): 14226–14231. Bibcode: 1998PNAS...9514226Z. doi: 10.1073/pnas.95.24.14226. PMC 24355. PMID 9826682. Snakes have been part and parcel of culture and religion. Vivid scale patterns have been thought to have influenced early art. The use of snake-skin in manufacture of purses, apparel and other articles led to large-scale killing of snakes, giving rise to advocacy for use of artificial snake-skin. Snake scales are also to be found as motifs in fiction, art and films.

Highly developed lungs – All reptiles rely on their lungs to breathe air. Even species with permeable skin and other adaptations never completely breathe without the use of their lungs. The dorsal (or body) scales on the snake's body are arranged in rows along the length of their bodies. Adjacent rows are diagonally offset from each other. Most snakes have an odd number of rows across the body though certain species have an even number of rows e.g. Zaocys spp. [8] In the case of some aquatic and marine snakes, the scales are granular and the rows cannot be counted. [20] a b c Lee, M.S.Y. (2013). "Turtle origins: Insights from phylogenetic retrofitting and molecular scaffolds". Journal of Evolutionary Biology. 26 (12): 2729–2738. doi: 10.1111/jeb.12268. PMID 24256520. Farmer, C.G. (2000). "Parental care: The key to understanding endothermy and other convergent features in birds and mammals". American Naturalist. 155 (3): 326–334. doi: 10.1086/303323. PMID 10718729. S2CID 17932602. The reptile has rough scales or bony plates covering the skin which are shed on a regular basis. These cold-blooded creatures cannot maintain a consistent internal body temperature and rely completely on the external environment to warm up or cool down.

In the 18th century, the reptiles were, from the outset of classification, grouped with the amphibians. Linnaeus, working from species-poor Sweden, where the common adder and grass snake are often found hunting in water, included all reptiles and amphibians in class "III – Amphibia" in his Systema Naturæ. [7] Klein, Wilfied; Abe, Augusto; Andrade, Denis; Perry, Steven (2003). "Structure of the posthepatic septum and its influence on visceral topology in the tegu lizard, Tupinambis merianae (Teidae: Reptilia)". Journal of Morphology. 258 (2): 151–157. doi: 10.1002/jmor.10136. PMID 14518009. S2CID 9901649.