The composition of Euryapsida was uncertain. Ichthyosaurs were, at times, considered to have arisen independently of the other euryapsids, and given the older name Parapsida. Parapsida was later discarded as a group for the most part (ichthyosaurs being classified as incertae sedis or with Euryapsida). However, four (or three if Euryapsida is merged into Diapsida) subclasses remained more or less universal for non-specialist work throughout the 20thcentury. It has largely been abandoned by recent researchers: In particular, the anapsid condition has been found to occur so variably among unrelated groups that it is not now considered a useful distinction. [18] Phylogenetics and modern definition [ edit ] 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] The terms reptile and amphibian were largely interchangeable, reptile (from Latin repere, 'to creep') being preferred by the French. [8] J.N. Laurenti was the first to formally use the term Reptilia for an expanded selection of reptiles and amphibians basically similar to that of Linnaeus. [9] Today, the two groups are still commonly treated under the single heading herpetology.

Farmer, CG; Sanders, K (2010). "Unidirectional airflow in the lungs of alligators". Science. 327 (5963): 338–340. Bibcode: 2010Sci...327..338F. doi: 10.1126/science.1180219. PMID 20075253. S2CID 206522844. DABVP, Ryan S. De Voe DVM MSpVM DACZM. "Reptilian cardiovascular anatomy and physiology: evaluation and monitoring (Proceedings)". dvm360.com. Archived from the original on 2018-11-06 . Retrieved 2017-04-22. The dinosaurs featured in books, films, television programs, artwork, and other media have been used for both education and entertainment. The depictions range from the realistic, as in the television documentaries of the 1990s and first decade of the 21st century, to the fantastic, as in the monster movies of the 1950s and 1960s. [148] [150] [151] At the end of the ventral scales of the snake is a cloacal plate that protects the opening to the cloaca (a shared opening for waste and reproductive material to pass) on the underside near the tail. This scale has also been the anal scale, which is a misnomer since it does not cover an anus but a cloaca. This cloacal scale may be single or paired. Most authors have differentiated between single and divided cloacal scales. However, based on the origin of scales during development, a scale does not spontaneously divide, but it originates as paired structures that subsequently overlap. The part of the body beyond the cloacal scale is considered to be the tail. [13] Baker, Barry W (2006). "Forensic implications of dorsal row counts on Puff-faced Water-snakes (Colubridae: Homalopsinae: Homalopsis buccata)" (PDF). Herpetological Review. 37 (2): 171–173.The scales patterning may also be used for individual identification in field studies. Clipping of specific scales, such as the subcaudals, to mark individual snakes is a popular approach to population estimation by mark and recapture techniques. [30] Distinguishing between venomous and non-venomous snakes [ edit ] Banded Krait ( Bungarus fasciatus), an Elapid, with no loreal scale between nasal and pre-ocular scales. Despite the early proposals for replacing the paraphyletic Reptilia with a monophyletic Sauropsida, which includes birds, that term was never adopted widely or, when it was, was not applied consistently. [2] Bearded dragon ( pogona) skeleton on display at the Museum of Osteology See also: Skull roof Reptiles, from Nouveau Larousse Illustré, 1897–1904, notice the inclusion of amphibians (below the crocodiles)

Snake scales occur as a motif regularly in computer action games. [37] [38] [39] [40] A snake scale was portrayed as a clue in the 1982 film Blade Runner. [41] Snake scales also figure in popular fiction, such as the Harry Potter series (desiccated Boomslang skin is used as a raw material for concocting the Polyjuice potion), and also in teen fiction. [42] See also [ edit ] 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. While modern reptiles are predominantly carnivorous, during the early history of reptiles several groups produced some herbivorous megafauna: in the Paleozoic, the pareiasaurs; and in the Mesozoic several lines of dinosaurs. [43] Today, turtles are the only predominantly herbivorous reptile group, but several lines of agamas and iguanas have evolved to live wholly or partly on plants. [106] Directorate General Armed Forces Medical Services, India. Memorandum No 102: Snakebite. Undated.pdf available [ online]. Accessed on 21 Feb 2010. 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). [51]Evans, Susan E.; Klembara, Jozef (2005). "A choristoderan reptile (Reptilia: Diapsida) from the Lower Miocene of northwest Bohemia (Czech Republic)". Journal of Vertebrate Paleontology. 25 (1): 171–184. doi: 10.1671/0272-4634(2005)025[0171:ACRRDF]2.0.CO;2. S2CID 84097919.

a b c d e f g Greene, Harry W. (2004) Snakes – The Evolution of Mystery in Nature. University of California Press, pp. 22–23 ISBN 0520224876. Identification of cephalic scales is most conveniently begun with reference to the nostril, which is easily identified on a snake. There are two scales enclosing the nostril which are called the nasals. In colubrids, the nostril lies between the nasals, while in vipers it lies in the centre of a single nasal scale. [22] The outer nasal (near the snout) is called the prenasal while the inner nasal (near the eye) is called the postnasal. Along the top of the snout connecting the nasals on both sides of the head are scales called internasals. Between the two prenasals is a scale at the tip of the snout called the rostral scale. [22] Goodrich, E.S. (1916). "On the classification of the Reptilia". Proceedings of the Royal Society of London B. 89 (615): 261–276. Bibcode: 1916RSPSB..89..261G. doi: 10.1098/rspb.1916.0012. The scales of a snake primarily serve to reduce friction as it moves, since friction is the major source of energy loss in snake locomotion. Rainbow boas get their name from the coloration of their scales caused by iridescence.

DISCUSSION

Reptiles are generally considered less intelligent than mammals and birds. [29] The size of their brain relative to their body is much less than that of mammals, the encephalization quotient being about one tenth of that of mammals, [122] though larger reptiles can show more complex brain development. Larger lizards, like the monitors, are known to exhibit complex behavior, including cooperation [123] and cognitive abilities allowing them to optimize their foraging and territoriality over time. [124] Crocodiles have relatively larger brains and show a fairly complex social structure. The Komodo dragon is even known to engage in play, [125] as are turtles, which are also considered to be social creatures, [126] and sometimes switch between monogamy and promiscuity in their sexual behavior. [ citation needed] One study found that wood turtles were better than white rats at learning to navigate mazes. [127] Another study found that giant tortoises are capable of learning through operant conditioning, visual discrimination and retained learned behaviors with long-term memory. [128] Sea turtles have been regarded as having simple brains, but their flippers are used for a variety of foraging tasks (holding, bracing, corralling) in common with marine mammals. [129] Christensen, Christian Bech; Christensen-Dalsgaard, Jakob; Brandt, Christian; Madsen, Peter Teglberg (2012-01-15). "Hearing with an atympanic ear: Good vibration and poor sound-pressure detection in the royal python, Python regius". Journal of Experimental Biology. 215 (2): 331–342. doi: 10.1242/jeb.062539. ISSN 1477-9145. PMID 22189777. S2CID 11909208. Capshaw, Grace; Willis, Katie L.; Han, Dawei; Bierman, Hilary S. (2020). "Reptile sound production and perception". In Rosenfeld, Cheryl S.; Hoffmann, Frauke (eds.). Neuroendocrine Regulation of Animal Vocalization. Academic Press. pp.101–118. ISBN 978-0128151600. a b Roos, Jonas; Aggarwal, Ramesh K.; Janke, Axel (Nov 2007). "Extended mitogenomic phylogenetic analyses yield new insight into crocodylian evolution and their survival of the Cretaceous–Tertiary boundary". Molecular Phylogenetics and Evolution. 45 (2): 663–673. doi: 10.1016/j.ympev.2007.06.018. PMID 17719245.

An older snake may shed its skin only once or twice a year, but a younger, still-growing snake, may shed up to four times a year. [18] The discarded skin gives a perfect imprint of the scale pattern and it is usually possible to identify the snake if this discard is reasonably complete and intact. [9] Arrangement of scales [ edit ] Nomenclature of head scales (top view of head) 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. Wang, Tobias; Altimiras, Jordi; Klein, Wilfried; Axelsson, Michael (2003). "Ventricular haemodynamics in Python molurus: separation of pulmonary and systemic pressures". The Journal of Experimental Biology. 206 (Pt 23): 4242–4245. doi: 10.1242/jeb.00681. PMID 14581594. Osborn, H.F. (1903). "The reptilian subclasses Diapsida and Synapsida and [the] early history of Diaptosauria". Memoirs of the American Museum of Natural History. 1: 451–507. Snakes have been a motif in human culture and religion and an object of dread and fascination all over the world. The vivid patterns of snake scales, such as the Gaboon Viper, both repel and fascinate the human mind. Such patterns have inspired dread and awe in humans from pre-historic times and these can be seen in the art prevalent to those times. Studies of fear imagery and psychological arousal indicate that snake scales are a vital component of snake imagery. Snake scales also appear to have affected Islamic art in the form of tessellated mosaic patterns which show great similarity to snake-scale patterns. [34]In the late 19th century, a number of definitions of Reptilia were offered. The traits listed by Lydekker in 1896, for example, include a single occipital condyle, a jaw joint formed by the quadrate and articular bones, and certain characteristics of the vertebrae. [14] The animals singled out by these formulations, the amniotes other than the mammals and the birds, are still those considered reptiles today. [15] The first reptiles had an anapsid type of skull roof, as seen in the Permian genus Captorhinus a b Piñeiro, Graciela; Ferigolo, Jorge; Ramos, Alejandro; Laurin, Michel (2012). "Cranial morphology of the Early Permian mesosaurid Mesosaurus tenuidens and the evolution of the lower temporal fenestration reassessed". Comptes Rendus Palevol. 11 (5): 379–391. Bibcode: 2012CRPal..11..379P. doi: 10.1016/j.crpv.2012.02.001. 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. Exposed parts of reptiles are protected by scales or scutes, sometimes with a bony base ( osteoderms), forming armor. 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. [ citation needed] The scales found in turtles and crocodiles are of dermal, rather than epidermal, origin and are properly termed scutes. [ citation needed] In turtles, the body is hidden inside a hard shell composed of fused scutes.