a b Bertelsen, E.; Pietsch, T.W. (1998). Paxton, J.R.; Eschmeyer, W.N. (eds.). Encyclopedia of Fishes. San Diego: Academic Press. pp.138–139. ISBN 0-12-547665-5. In most cars 30mph will almost always burn less fuel for a given journey than 60mph. The energy (fuel) needed to get from A to B is primarily determined by two factors: the efficiency of the car's drive chain (engine, gearbox, differential etc) and external resistance to the car's movement.

Top 10 best jumper animals". Scienceray. Archived from the original on 2012-08-10 . Retrieved 2012-06-11. The origins and evolutionary relationships between the three main groups of amphibians are hotly debated. A molecular phylogeny based on rDNA analysis dating from 2005 suggests that salamanders and caecilians are more closely related to each other than they are to frogs and the divergence of the three groups took place in the Paleozoic or early Mesozoic before the breakup of the supercontinent Pangaea and soon after their divergence from the lobe-finned fishes. This would help account for the relative scarcity of amphibian fossils from the period before the groups split. [24] Another molecular phylogenetic analysis conducted about the same time concluded that lissamphibians first appeared about 330 million years ago and that the temnospondyl-origin hypothesis is more credible than other theories. The neobatrachians seemed to have originated in Africa/India, the salamanders in East Asia and the caecilians in tropical Pangaea. [25] Other researchers, while agreeing with the main thrust of this study, questioned the choice of calibration points used to synchronise the data. They proposed that the date of lissamphibian diversification should be placed in the Permian, rather less than 300 million years ago, a date in better agreement with the palaeontological data. [26] A further study in 2011 using both extinct and living taxa sampled for morphological, as well as molecular data, came to the conclusion that Lissamphibia is monophyletic and that it should be nested within Lepospondyli rather than within Temnospondyli. The study postulated that Lissamphibia originated no earlier than the late Carboniferous, some 290 to 305 million years ago. The split between Anura and Caudata was estimated as taking place 292 million years ago, rather later than most molecular studies suggest, with the caecilians splitting off 239 million years ago. [27] A fossilized frog from the Czech Republic, possibly Palaeobatrachus gigas Direct development, where eggs hatch into juveniles like small adults, is also known in many frogs, for example, Ischnocnema henselii, [143] Eleutherodactylus coqui, [144] and Raorchestes ochlandrae and Raorchestes chalazodes. [145] Tadpoles Frogspawn development The burrowing frogs of Australia have a rather different lifestyle. The western spotted frog ( Heleioporus albopunctatus) digs a burrow beside a river or in the bed of an ephemeral stream and regularly emerges to forage. Mating takes place and eggs are laid in a foam nest inside the burrow. The eggs partially develop there, but do not hatch until they are submerged following heavy rainfall. The tadpoles then swim out into the open water and rapidly complete their development. [118] Madagascan burrowing frogs are less fossorial and mostly bury themselves in leaf litter. One of these, the green burrowing frog ( Scaphiophryne marmorata), has a flattened head with a short snout and well-developed metatarsal tubercles on its hind feet to help with excavation. It also has greatly enlarged terminal discs on its fore feet that help it to clamber around in bushes. [119] It breeds in temporary pools that form after rains. [120] Climbing Burmeister's leaf frog Group of glass frogs a b Froese, Rainer; Pauly, Daniel (eds.) (2009). " Histrio histrio " in FishBase. Sep 2009 version.Roy, Debjani (1997). "Communication signals and sexual selection in amphibians" (PDF). Current Science. 72: 923–927. Archived from the original (PDF) on 2012-09-23. Anderson, Jason S.; Reisz, Robert R.; Scott, Diane; Fröbisch, Nadia B.; Sumida, Stuart S. (2008). "A stem batrachian from the Early Permian of Texas and the origin of frogs and salamanders". Nature. 453 (7194): 515–518. Bibcode: 2008Natur.453..515A. doi: 10.1038/nature06865. PMID 18497824. S2CID 205212809. In open water, frogfishes can swim with strokes of the caudal fin. They also use jet propulsion, often used by younger frogfish. It is achieved by rhythmically gulping water and forcing it out through their gill openings, also called opercular openings, which lie behind their pectoral fins. [10] Armstrong, Cecilia E.; Roberts, William M. (1998). "Electrical properties of frog saccular hair cells: distortion by enzymatic dissociation". Journal of Neuroscience. 18 (8): 2962–2973. doi: 10.1523/JNEUROSCI.18-08-02962.1998. PMC 6792591. PMID 9526013. Bailly, Anatole (1981). Abrégé du dictionnaire grec français. Paris: Hachette. ISBN 978-2010035289. OCLC 461974285.

Frogs have three-chambered hearts, a feature they share with lizards. Oxygenated blood from the lungs and de-oxygenated blood from the respiring tissues enter the heart through separate atria. When these chambers contract, the two blood streams pass into a common ventricle before being pumped via a spiral valve to the appropriate vessel, the aorta for oxygenated blood and pulmonary artery for deoxygenated blood. [70]The crab-eating frog ( Fejervarya cancrivora) is a frog native to south-eastern Asia including Taiwan, [2] China, the Philippines and more rarely as far west as Orissa in India. [3] It has also been introduced to Guam, most likely from Taiwan. [4] It inhabits mangrove swamps and marshes and is one of 144 known modern amphibians which can tolerate brief excursions into seawater, and is possibly the only extant marine amphibian. [5] Frogs that live in or visit water have adaptations that improve their swimming abilities. The hind limbs are heavily muscled and strong. The webbing between the toes of the hind feet increases the area of the foot and helps propel the frog powerfully through the water. Members of the family Pipidae are wholly aquatic and show the most marked specialization. They have inflexible vertebral columns, flattened, streamlined bodies, lateral line systems, and powerful hind limbs with large webbed feet. [113] Tadpoles mostly have large tail fins which provide thrust when the tail is moved from side to side. [114] Burrowing

Slow-motion photography shows that the muscles have passive flexibility. They are first stretched while the frog is still in the crouched position, then they are contracted before being stretched again to launch the frog into the air. The fore legs are folded against the chest and the hind legs remain in the extended, streamlined position for the duration of the jump. [50] In some extremely capable jumpers, such as the Cuban tree frog ( Osteopilus septentrionalis) and the northern leopard frog ( Rana pipiens), the peak power exerted during a jump can exceed that which the muscle is theoretically capable of producing. When the muscles contract, the energy is first transferred into the stretched tendon which is wrapped around the ankle bone. Then the muscles stretch again at the same time as the tendon releases its energy like a catapult to produce a powerful acceleration beyond the limits of muscle-powered acceleration. [105] A similar mechanism has been documented in locusts and grasshoppers. [106] Bullfrog". Ohio Department of Natural Resources. Archived from the original on 2012-08-18 . Retrieved 2012-06-19. Joel, Lucas (2020-04-23). "Fossil Shows Cold-Blooded Frogs Lived on Warm Antarctica". The New York Times. ISSN 0362-4331. Archived from the original on 2020-04-23 . Retrieved 2020-05-13. a b c d "Frog's internal systems". TutorVista.com. 2010. Archived from the original on 2008-01-21 . Retrieved 2012-06-04. Wallace's Flying Frog Rhacophorus nigropalmatus". National Geographic: Animals. 2010-09-10. Archived from the original on January 18, 2010 . Retrieved 2012-06-05.Lee, Deborah (2010-04-23). " Telmatobius culeus". AmphibiaWeb. University of California, Berkeley . Retrieved 2012-07-09. Ren, Z., Zhu, B., Ma, E., Wen, J., Tu, T., Cao, Y., Hasegawa, M. & Zhong, W. (2015). Complete nucleotide sequence and gene arrangement of the mitochondrial genome of the crab-eating frog Fejervarya cancrivora and evolutionary implications. Gene, 441: 148-155. Inger, Robert F. (1966). The Systematics and Zoogeography of the Amphibia of Borneo. Chicago (IL): Field Museum of Natural History. ISBN 983-99659-0-5. Faivovich, J.; Haddad, C. F. B.; Garcia, P. C. A.; Frost, D. R.; Campbell, J. A.; Wheeler, W. C. (2005). "Systematic review of the frog family Hylidae, with special reference to Hylinae: Phylogenetic analysis and revision". Bulletin of the American Museum of Natural History. 294: 1–240. CiteSeerX 10.1.1.470.2967. doi: 10.1206/0003-0090(2005)294[0001:SROTFF]2.0.CO;2. S2CID 83925199.

The eyes of most frogs are located on either side of the head near the top and project outwards as hemispherical bulges. They provide binocular vision over a field of 100° to the front and a total visual field of almost 360°. [80] They may be the only part of an otherwise submerged frog to protrude from the water. Each eye has closable upper and lower lids and a nictitating membrane which provides further protection, especially when the frog is swimming. [81] Members of the aquatic family Pipidae have the eyes located at the top of the head, a position better suited for detecting prey in the water above. [80] The irises come in a range of colours and the pupils in a range of shapes. The common toad ( Bufo bufo) has golden irises and horizontal slit-like pupils, the red-eyed tree frog ( Agalychnis callidryas) has vertical slit pupils, the poison dart frog has dark irises, the fire-bellied toad ( Bombina spp.) has triangular pupils and the tomato frog ( Dyscophus spp.) has circular ones. The irises of the southern toad ( Anaxyrus terrestris) are patterned so as to blend in with the surrounding camouflaged skin. [81] In many arboreal frogs, a small "intercalary structure" on each toe increases the surface area touching the substrate. Furthermore, many arboreal frogs have hip joints that allow both hopping and walking. Some frogs that live high in trees even possess an elaborate degree of webbing between their toes. This allows the frogs to "parachute" or make a controlled glide from one position in the canopy to another. [54]Frogs are used for dissections in high school and university anatomy classes, often first being injected with coloured substances to enhance contrasts among the biological systems. This practice is declining due to animal welfare concerns, and "digital frogs" are now available for virtual dissection. [219] Tan, W.-H.; Tsai, C.-G.; Lin, C.; Lin, Y. K. (2014-06-05). "Urban canyon effect: storm drains enhance call characteristics of the Mientien tree frog". Journal of Zoology. 294 (2): 77–84. doi: 10.1111/jzo.12154. ISSN 0952-8369. I have to admit that I was thoroughly excited when I heard the news of Sea Frogs impending release of a water housing designed specifically for surf photography. Sea Frogs new housing would not only overcome the short comings of the older standard dive housing but it would also offer a host of extra features that we would normally only associate with top line highly expensive water housings.