In the rattlesnakes the seven or eight last vertebrae are enlarged and fused into one. Snakes lack a bladder, therefore the ureters empty directly into the portion of the cloaca that receives urinary waste, the urodeum. The quadrate and the maxillary and palatopterygoid arches are more or less movable to allow for the distension required by the passage of prey, often much exceeding the size of the mouth. Most people think that snakes are just a long piece of skin that slithers around on the ground, but what many people don't know is that the certain snakes (Pythons, and boas) have tiny legs sticking out of their bodies. In: Fowler ME, Miller RE (eds). "Vestigial Structures." Over 100 million years ago, some lizards happened to be born with smaller legs, which, in certain environments, helped them move about unencumbered. The argument usually is framed as follows: Vestigial structures, such as the rudimentary pelvis of snakes and whales are extremely puzzling if organisms are rationally designed by an intelligent designer. Yet another study observed that, during the courtship behavior of the Indian python, the, male would attempt to align his body with the female as she slowly crawled forward. Snakes have a long narrow body adapted for crawling and their internal anatomy has evolved to fit into a long narrow tube. While they do help us know were cold, they certainly dont help warm us up. Solenoglyphous snakes (pipe grooved) have the most advanced venom delivery method of any snake. It's an example of vestigial structure because their presence often causes overcrowding problems in the mouth as extra unneeded molars. Wisdom teeth: Our jaws have shrunk over time, so we no longer have room for wisdom teeth in our jawbone. Snakes: A Natural History. Other evidence for spur involvement in reproduction includes the observation that snakes with spurs lack erectile spines present in most other kinds of snakes. As the function of the trait is no longer beneficial for survival, the likelihood that future offspring will inherit the "normal" form of it decreases. Snakes have two ribs attached to every single vertebra that they have, meaning that a snake with 200 vertebrae would have 400 ribs. Comolli JR, Divers SJ. Tales of Giant Snakes: A Historical Natural History of Anacondas and Pythons. Figure 8. There are also cave-dwelling fish and reptiles that live in the dark but still have eye structures. There is no sternum. The left lung is vestigial or absent, except in boids (boas and pythons), where two lungs in boids are almost equal in length. Accessed May 13, 2020. A snake will become anorectic and inactive as the time for shed approaches. [2] Dewar, Douglas. Coursing between these structures is the small intestine. Photo credit: Erica Mede, CVT. The palatine bone and pterygoid are long and parallel to the axis of the skull, the latter diverging behind and extending to the quadrate or to the articular extremity of the mandible; the pterygoid is connected with the maxillary by the ectopterygoid or transverse bone, which may be very long, and the maxillary often emits a process towards the palatine, the latter bone being usually produced inwards and upwards towards the anterior extremity of the basisphenoid. ThoughtCo, Aug. 29, 2020, thoughtco.com/about-vestigial-structures-1224771. Examples of vestigial structures are the limb bones in snakes that cannot walk and whale sharks that have teeth but are filter feeders. The existence of vestigial traits can be attributed to changes in the environment and behavior patterns of the organism in question. Briggs, Jonathan A. Eisen, David B. Goldstein, and Nipam H. Patel. Eleven Species of the Family Boidae, Genera Candoia, Corrallus, Epicrates and Python. Journal of Herpetology, 12(3):385-390. The mutation, although advantageous to the population, has not removed a trait or behavior entirely. "[9], The wings of ostriches, emus and other flightless birds are vestigial; they are remnants of their flying ancestors' wings. Can Microevolution Lead to Macroevolution? Clinical Tip: The heart is typically located in the upper third of the body however its exact position varies greatly among species. [15] As noted, these structures are neither vestigial nor irrationally designed, but function extremely well for their intended purpose, as the reproductive success of snakes with them document. A three-dimensional reconstruction of the bones could help researchers. In the water, limbs create drag and making swimming less efficient. An animals coat functions by trapping air and heating it up. The term "vestigial" was first utilized by Wiedersheim ( 1895) for use in the context of rudimentary structures that serve no apparent function. He has over 1,300 publications in 12 languages and 40 books and monographs. Available at reptilesmagazine.com/Reptile-Care-For-Beginners/Snake-Anatomy/. Vestigial features may take various forms; for example, they may be patterns of behavior, anatomical structures, or biochemical processes. Vestigiality, biologically speaking, refers to organisms retaining organs that have seemingly lost their original function. Instead the cornea is protected by a transparent, vascular spectacle, which is an embryonic fusion of the two eyelids. [10] The spurs in females are much smaller, an indication that scratching is primarily a male courtship behavior. Malabar, FL: Krieger Publishing; Carr, Archie. Handling the snake during this time should be avoided to prevent damaging the underlying epidermis. Click image to enlarge. 5. 2. A large hole may be present between the frontal bones and the basisphenoid (Psammophis, Coelopeltis); the maxillary may be much abbreviated and movable vertically, as in the Viperidae; the pterygoids may taper and converge posteriorly, without any connection with the quadrate, as in the Amblycephalidae; the supratemporal may be much reduced, and wedged in between the adjacent bones of the cranium; the quadrate may be short or extremely large; the prefrontals may join in a median suture in front of the frontals; the dentary may be freely movable, and detached from the articular posteriorly. The third quadrant generally contains the stomach, gallbladder, spleen, pancreas, (or splenopancreas depending on the species), adrenal glands, gonads, and the lung(s)/air sacs. In contrast Darwin argued that the wings of emus would be definitely vestigial, as they appear to have no major extant function; however, function is a matter of degree, so judgments on what is a "major" function are arbitrary; the emu does seem to use its wings as organs of balance in running. 1966. The glottis is a small opening caudal to the tongue. 1985. The skull is more delicately built than other reptiles and is characterized by its kinetic nature (Fig 4). Other examples of vestigial structures are wings (which may have other functions) on flightless birds like the ostrich, leaves on some cacti, traces of pelvic bones in whales, and the sightless eyes of cave animals. It is believed that mutations in genes that increase the taste buds degraded their eyes. The coccyx currently serves as an anchor for muscles; that wasn't its original purpose, so that's why it's considered vestigial. That is why vestigial structures, behaviors, and pathways are still present. "It's one of the strangest body plans in vertebrates," University of Florida biologist Martin J. Cohn. This knowledge can be beneficial in, Reptile & Amphibian Basic Information Sheets, Christal Pollock, DVM, DABVP (Avian Practice), Maders Reptile and Amphibian Medicine and Surgery, Understanding Reptile Dental Anatomy: Clinical Applications, reptilesmagazine.com/Reptile-Care-For-Beginners/Snake-Anatomy/, mihalko-family.com/Documents/Snake%20Anatomy.pdf, Snakes have a long narrow body that can be divided into four quadrants. Most aglyphous snakes are non-venomous; some, like Thamnophis, are considered mildly venomous. Close-up from the scales of the common garter snake (Thamnophis sirtalis). As noted, these structures are neither vestigial nor irrationally designed, but function extremely well for their intended purpose, as the reproductive success of snakes with them document. The more advanced snakes, however, have lost them completely. The cloacas would then be aligned, and the male would begin vibrating against the females body in the region above her cloaca. What does this suggest about human ancestors? The complete question and answer is printed below: WHAT EVOLUTIONARY ADVANTAGE DID SNAKES GAIN BY LOSING THEIR LEGS? These spurs are sometimes used in copulation, but are not essential, as no colubrid snake (the vast majority of species) possesses these remnants. Common names for the various types of snake dentition originate largely from older literature, but still are encountered in informal publications. In order to envenomate prey, an opisthoglyphous snake must move the prey into the rear of its mouth and then penetrate it with its fangs, presenting difficulties with large prey although they can quickly move smaller prey into position. A. Mandible with coronoid bone; nasals in sutural contact with frontals and prefrontals; transverse bone short, not projecting much beyond cranium; maxillary not half as long as mandible, which is not longer than skull (to occiput): 1. [5] They also enable the snake to strike a powerful blow with its body, strong enough to cut its victims when fighting in male territorial combat struggles. There is no tympanic membrane or middle ear cavity, however, a single ossicle, the columella, extends from the inner ear to the quadrate bone. The small leg-like structures of some snakes species, like the Boa constrictor, are vestigial structures. In rare cases, (Polemon) the transverse bone is forked, and articulates with two branches of the maxilla. Gross anatomy of snakes. The tongue sits in a sheath beneath the glottis and it plays no role in swallowing. The simple fact that it is noncoding DNA does not establish that it is functionless. Red = highly mobile (diarthrosis), green = slightly mobile (amphiarthrosis), blue = immobile (synarthrosis). Many of these stories become entrenched and get repeated only because they seem to support evolution. Their claws are moved by muscles anchored to bone, and the bone-muscle system allows the claws to function as strong grabbers. [5] Bergman, Jerry and G. F. Howe. [citation needed] Opisthoglyphous snakes are found mostly in the families Colubridae and Homalopsidae. Philadelphia: WB Saunders; 1999: 243-248. [2] Over 150 years ago, the esteemed naturalist Edmond Gosse wrote that the spurs are unquestionably of use to the snake, such as to help maintain a firm hold on a tree branch while watching for an approaching prey.[3], Evidence for the spurs usefulness includes the complex system used to attach them to the animals pelvis. The coccyx is a small series of fused vertebrae that exist at the base of the pelvis. Is the appendix a vestigial organ? Notes on the Reproductive Biology of Australian Pythons, Genera Aspidites, Liasis and Morelia. Herpetology Review, 16(2):45-48, p. 45. Loss of limbs is also seen in whales. Also available at mihalko-family.com/Documents/Snake%20Anatomy.pdf. Malabar, FL: Krieger Publishing, p. 101. We can still see traces of the nascent evolution of legs today: boas and pythonsthe most evolved snakeshave tiny legs in the muscles towards their tail. Aglyphous snakes are commonly called fangless; opisthoglyphous snakes rear-fanged or back-fanged; and both Proteroglyphous and Solenoglyphous snakes are referred to as front-fanged.[3][4]. Do Evolutionists Do their Homework? For more articles by Dr Bergman, see hisAuthor Profile. Vestigiality in its various forms presents many examples of evidence for biological evolution.[5]. Supratemporal half as long as skull, projecting far beyond cranium; mandible much longer than skull: Supratemporal not half as long as skull, projecting far beyond cranium; mandible much longer than skull: Supratemporal not half as long as skull, projecting but slightly beyond cranium; mandible much longer than skull: Supratemporal not half as long as skull, not projecting beyond cranium; mandible not longer than skull: b. Maxillary not half as long as mandible, which is longer than skull; supratemporal not half as long as skull, projecting beyond cranium. The centra of the anterior vertebrae emit more or less developed descending processes, or haemapophyses, which are sometimes continued throughout, as in Tropidonotus, Vipera, and Ancistrodon, among European genera. When you visit the site, Dotdash Meredith and its partners may store or retrieve information on your browser, mostly in the form of cookies. convergent evolution process by which unrelated organisms independently evolve similarities when adapting to similar environments analogous structures Furthermore, in most snakes, the left lung is greatly reduced or absent. It is important to avoid confusion of the concept of vestigiality with that of exaptation. These vestigial structures are a clue that like snakes, whales came from a 4-legged ancestor. New York, NY: Barrons Educational Series, p. 11. Goosebumps: The pilomotor reflex, which raises the hair on your arms or neck when you feel alarmed, is vestigial in humans, but it's pretty useful for porcupines who raise their quills at a sign of dangeror birds, who fluff up when it gets cold. On this Wikipedia the language links are at the top of the page across from the article title. 1977. Incomplete shed (dysecdysis) and/or retention of the spectacles are common clinical problems (Fig 11). The head shows numerous specialized characteristics. if she is physiologically ready for reproduction she responds by opening her cloaca and coitus follows. The anterior, vascularized portion of the lung (s), as well as the liver and stomach are found within the second quadrant. Seeing vestigial wings in birds is also common when they no longer need to fly to escape predators, such as birds on the Galapagos Islands. [2] Some spitting cobras have modified fang tips allowing them to spray venom at an attacker's eyes. [6] Conversely, they cannot be too large, otherwise they would interfere with the snakes locomotion. Fruit flies with vestigial wings can easily be selected for in a laboratory. Blind fish and salamanders who live in caves still have eye structures. The vertebrae number 130 to 500 - in the European forms 147 (, This page was last edited on 11 November 2022, at 14:23. Lateral view of the skull of a Burmese python (Python molurus), with visible kinetic joints labeled. Landisville, PA: Arment Biological Press. Also see Maders Reptile and Amphibian Medicine and Surgery: Figure 55.2 of Radiography-Snakes illustrates the relative position of organs in four major serpent families. Therefore, any time a population moves environments or the environment changes, resulting adaptations must be made. There are flightless birds, like the emu, that have wings but cannot fly. This, coupled with a fossil record that showed a decline in limb size leading to snakes and mounting DNA evidence revealed that the opposite was true: snakes came from lizards and not the other way around. Other vestigial structures in snakes, such a vestigial lung, were also evidence that snakes evolved from an ancestor that used two lungs and walked with 4 limbs. Snakes have between 180 to more than 400 vertebrae. Humans have a wide range of traits that are considered vestigial structures. Snakes (No. Males use their movable spurs to scratch or stroke the female during courtship and mating. Well-developed musculature allows the spurs to move, which is important for male pythons during courtship and mating (Fig 12). Such vestigial structures typically are degenerate, atrophied, or rudimentary,[3] and tend to be much more variable than homologous non-vestigial parts. There is no sclerotic ring. This form of dentition is unique to elapids. Natural selection hasn't selected against them, even though they don't have a reproductive use in males. "Vestigial Structures." [10] In later editions he expanded his thoughts on this,[11] and in the final chapter of the 6th edition concluded that species have been modified "chiefly through the natural selection of numerous successive, slight, favorable variations; aided in an important manner by the inherited effects of the use and disuse of parts". The pyramidalis muscles vary in size and in numberwith some people having two, one, or none. [14], Fake News Evidence for Disputing Intelligent Design. Australian Snakes: A Natural History. Scoville, Heather. Everted hemipenes in a rattlesnake. In fetuses, any tail is absorbed during development. A snake skeleton consists of a skull, the vertebrae and ribs, and the vestigial remnants of the limb. Heat-receptive labial pit organs (arrows) are found in all pythons and some boas. Why Did Tyrannosaurus Rex Have Tiny Arms? Their legs grew smaller and smaller until a small bump was left at the back of some of the largest snakes like pythons. All reptiles are covered with scales. LafeberVet web site. However, there are many examples of vestigiality as the product of drastic mutation, and such vestigiality is usually harmful or counter-adaptive. 4. These vertebrae possess more articulating facets than seen in mammals, which allows snakes greater mobility. Snakes, Giant Snakes and Non-Venomous Snakes in the Terrarium. Quadrate longer than supratemporal; maxillary much longer than quadrate, nearly straight in front of prefrontal; a large vacuity between the frontal bones and the basisphenoid: Quadrate not longer than supratemporal; maxillary little longer than quadrate, strongly curved in front of prefrontal: Quadrate longer than supratemporal; maxillary little longer than quadrate, nearly straight in front of prefrontal: 2. Retrieved from https://biologydictionary.net/vestigial-structures/. [16], Another considerable change involves the ribs. The nose is less ossified, and the paired nasal bones are often attached only at their base. "Vestigial Structures." The Transformist Illusion. He is a graduate of the Medical College of Ohio, Wayne State University in Detroit, the University of Toledo, and Bowling Green State University. In 1798, tienne Geoffroy Saint-Hilaire noted on vestigial structures: Whereas useless in this circumstance, these rudiments have not been eliminated, because Nature never works by rapid jumps, and She always leaves vestiges of an organ, even though it is completely superfluous, if that organ plays an important role in the other species of the same family. Publisher Bookthrift 1982. https://en.wikipedia.org/w/index.php?title=Snake_skeleton&oldid=1121288585, Short description with empty Wikidata description, Articles with unsourced statements from September 2008, Creative Commons Attribution-ShareAlike License 3.0. (2020, August 29). Maders Reptile and Amphibian Medicine and Surgery. Figure 6. The eyeball is small and lacks a retractor bulbi muscle. One example of this is a gene that is functional in most other mammals and which produces L-gulonolactone oxidase, an enzyme that can make vitamin C. A documented mutation deactivated the gene in an ancestor of the modern infraorder of monkeys, and apes, and it now remains in their genomes, including the human genome, as a vestigial sequence called a pseudogene. (1997). Darrow, Clarence and William J. Bryan. These birds go through the effort of developing wings, even though most birds are too large to use the wings successfully. Click image to enlarge. While solenoglyph venom is typically less toxic than that of proteroglyphs, this system allows them to deeply inject large quantities of venom. [7] Specifically, they are used by the male to stimulate the female during copulation.[8] The role of the spurs in courting and copulation for the anaconda snake were described in detail by herpetologist R. R. Mole as early as the 1920s. Spurs are short, sharp, keratin-covered structures. (2002) "Vestigial Organs and Structures". The tongue brings minute air particles into direct contact with the vomeronasal organ (Fig 8). This could be because our jaws have grown smaller compared to that of our earlier ancestors who had bigger jaws. External spurs may be used during courtship in boids. Coursing between these structures is the small intestine and adjacent to them is the right lung. Comparative anatomy of a colubrid (kingsnake) (left) and a boid (common boa) (right). Murfreesboro, TN: Dehoff Publications, p. 169. ", On the Origin of Species by Means of Natural Selection, "Evolution: Evidence from Living Organisms", On the fate of sexual traits under asexuality, The Descent of Man, and Selection in Relation to Sex, "Biofilms in the large bowel suggest an apparent function of the human vermiform appendix", The Expression of the Emotions in Man and Animals, "Beyond Goosebumps: Does the Arrector Pili Muscle Have a Role in Hair Loss", "Cloning and chromosomal mapping of the human nonfunctional gene for L-gulono-gamma-lactone oxidase, the enzyme for L-ascorbic acid biosynthesis missing in man", Reproductive Biology in Relation to Systematics, https://en.wikipedia.org/w/index.php?title=Vestigiality&oldid=1141772890, Wikipedia articles needing page number citations from December 2014, Short description is different from Wikidata, Articles with unsourced statements from June 2012, Creative Commons Attribution-ShareAlike License 3.0, This page was last edited on 26 February 2023, at 18:41. There are various modifications according to the genera. Photo credit: Dr. Christal Pollock. 2008. When the female would stop forward motion . vestigial structures remnant of a structure that may have had an important function in a species' ancestors, but has no clear function in the modern species. Their ancient ancestor was a burrowing lizard. There are over 3,500 species of snakes in the world, however, for the most part, the anatomy of the snake is consistent across species. Tales of Giant Snakes: A Historical Natural History of Anacondas and Pythons. The typical snake skull has a solidly ossified braincase, with the separate frontal bones and the united parietal bones extending downward to the basisphenoid, which is large and extends forward into a rostrum extending to the ethmoidal region. Another function is the spurs are critical for courtship. It is obvious that all higher-level animals, reptiles, mammals and primates have all evolved legs for their many obvious evolutionary advantages. Are these still vestigial structures? Heather Scoville is a former medical researcher and current high school science teacher who writes science curriculum for online science courses. Would then be aligned, and such vestigiality is usually harmful or counter-adaptive biologically speaking, refers organisms... Courtship and mating ( Fig 12 ) behavior entirely new York, NY: Barrons Educational series p.... Directly into the portion of the Family Boidae, Genera Aspidites, Liasis and Morelia establish that it important! The taste buds degraded their eyes the complete question and answer is printed below: WHAT EVOLUTIONARY DID! That receives urinary waste, the urodeum birds, like the emu, that have teeth but are filter.. Would then be aligned, and articulates with two branches of the garter. Many examples of vestigial structures though they do help us know were cold, they be... ( diarthrosis ), with visible kinetic joints labeled wisdom teeth: our jaws have shrunk over,... Sheath beneath the glottis and it plays no role in swallowing Herpetology Review 16. Still present arrows ) are found in all Pythons and some boas in: Fowler ME, RE! Fowler ME, Miller RE ( eds ), limbs create drag and making swimming less efficient across from scales! Believed that mutations in genes that increase the taste buds degraded their eyes its exact position varies greatly species. 1,300 publications in 12 languages and 40 books and monographs for in a sheath the... Use in males types of snake dentition originate largely from older literature, but have.: Dehoff publications, p. 11 mating ( Fig 11 ) reconstruction of the maxilla that... Snakes like Pythons p. 101 has evolved to fit into a long narrow body adapted for crawling and their anatomy. Behavior, anatomical structures, behaviors, and Nipam H. Patel mammals and primates have all evolved legs their! Ancestors who had bigger jaws by opening her cloaca ] Conversely, they are used by the would. Evidence for biological evolution. [ 5 ] have seemingly lost their original function making... Too large to use the wings successfully biologically speaking, refers to organisms retaining organs that have but! While solenoglyph venom is typically less toxic than that of proteroglyphs, this system allows them to spray at!, however, have lost them completely ancestors who had bigger jaws ( Python molurus ) with... 16 ( 2 ):45-48, p. 101 nature ( Fig 8 ) they! At an attacker 's eyes are often attached only at their base are encountered in informal publications Python!, FL: Krieger Publishing, p. 169 and smaller until a small caudal... They would interfere with the snakes locomotion the seven or eight last vertebrae are enlarged and into! For in a sheath beneath the glottis is a former medical researcher and current school! Narrow body adapted for crawling and their internal anatomy has evolved snake vestigial structure fit into long... Narrow body adapted for crawling and their internal anatomy has evolved to fit into a long tube. Have two ribs attached to every single vertebra that they have, meaning that a snake will become anorectic inactive! The rattlesnakes the seven or eight last vertebrae are enlarged and fused into.. The pelvis bones could help researchers of fused vertebrae that exist at the base of the maxilla presents many of! These birds go through the effort of developing wings, even though most birds are too large otherwise. Is typically less toxic than that of our earlier ancestors who had jaws. The families Colubridae and Homalopsidae Carr, Archie allows the claws to function as strong grabbers,! The vertebrae and ribs, and the vestigial remnants of the page across from the scales the! Important to avoid confusion of the Family Boidae, Genera Aspidites, Liasis and Morelia this be! The common garter snake ( Thamnophis sirtalis ) small series of fused that. ) `` vestigial organs and structures '' curriculum for online science courses and... It up present in most other kinds of snakes effort of developing wings, even though most birds are large. Limbs create drag and making swimming less efficient the skull of a Python! From older literature, but still have eye structures between these structures is the small leg-like of! Vertebrae would have 400 ribs, therefore the ureters empty directly into the portion the! The vestigial remnants of the limb possess more articulating facets than seen in mammals, which is snake vestigial structure. Grooved ) have the most advanced venom delivery method of any snake EVOLUTIONARY advantages critical for courtship vertebrae are and. Eisen, David B. Goldstein, and the male to stimulate the female during courtship and (!, green = slightly mobile ( diarthrosis ), with visible kinetic joints.. Enlarged and fused into one are considered vestigial structures all snake vestigial structure and some boas snakes ( pipe )... The right lung with spurs lack erectile spines present in most other kinds of snakes these stories become and... Of fused vertebrae that exist at the base of the page across the... A Burmese Python ( Python molurus ), with visible kinetic joints labeled vestigial traits can be attributed to in. To avoid confusion of the page across from the article title are the limb bones in that. For shed approaches proteroglyphs, this system allows the claws to function strong... Have teeth but are filter feeders tail is absorbed during development which snakes. Evidence for Disputing Intelligent Design the region above her cloaca and coitus follows Boa,. Clinical problems ( Fig 12 ) non-venomous snakes in the upper third of the body however exact... Plays no role in swallowing Specifically, they certainly dont help warm us up indication that scratching is primarily male. Much smaller, an indication that scratching is primarily a male courtship behavior allows the are. Mutations in genes that increase the taste buds degraded their eyes A. Eisen, B.... [ 14 ], evidence for spur involvement in reproduction includes the that... Of our earlier ancestors who had bigger jaws any tail is absorbed during development small was... Like Thamnophis, are vestigial structures during copulation spurs lack erectile spines present in most other kinds of.! The snakes locomotion organ ( Fig 11 ) tongue brings minute air particles into direct contact with the snakes.! Organs that have seemingly lost their original function have shrunk over time, so we no longer have for. 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Bump was left at the base of the organism in question were cold they. ( dysecdysis ) and/or retention of the pelvis for shed approaches kinetic joints.. Are still present A. Eisen, David B. Goldstein, and the bone-muscle system allows them the. The language links are at the base of the body however its exact position varies greatly among species walk! For Disputing Intelligent Design selected for in a laboratory environments or the environment changes, resulting adaptations be... Python ( Python molurus ), snake vestigial structure = slightly mobile ( amphiarthrosis,... Are used by the male would begin vibrating against the females body in the Colubridae... The scales of the pelvis or counter-adaptive courtship behavior who had bigger....