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90-409: The ichthyosaurian skull is sometimes described as having a metapsid (or parapsid ) condition instead of a truly euryapsid one. In ichthyosaurs, the squamosal bone is never part of the fenestra's margin. Parapsida was originally a taxon consisting of ichthyosaurs, squamates, protorosaurs, araeoscelidans and pleurosaurs . Historically, a variety of reptiles with upper fenestrae, either alone or with

180-514: A Konservat-Lagerstätte , meaning not only the quantity, but also the quality was exceptional. The skeletons were very complete and often preserved soft tissues, including tail and dorsal fins. Additionally, female individuals were discovered with embryos. In the early twentieth century, ichthyosaur research was dominated by the German paleontologist Friedrich von Huene , who wrote an extensive series of articles, taking advantage of an easy access to

270-443: A dorsal fin . Their heads were pointed, and the jaws often were equipped with conical teeth to catch smaller prey. Some species had larger, bladed teeth to attack large animals. The eyes were very large, for deep diving. The neck was short, and later species had a rather stiff trunk. These also had a more vertical tail fin, used for a powerful propulsive stroke. The vertebral column, made of simplified disc-like vertebrae, continued into

360-467: A pre-Adamite believing that ichthyosaurs were monstrous creations by the devil: Memoirs of Ichthyosauri and Plesiosauri of 1834 and The Book of the Great Sea-Dragons of 1840. The first work was illustrated by mezzotints by John Samuelson Templeton. These publications also contained scientific descriptions and represented the first textbooks of the subject. In the summer of 1834, Hawkins, after

450-582: A prehistoric reptile is a stub . You can help Misplaced Pages by expanding it . Ichthyosaur See text Ichthyosauria is an order of large extinct marine reptiles sometimes referred to as "ichthyosaurs", although the term is also used for wider clades in which the order resides. Ichthyosaurians thrived during much of the Mesozoic era; based on fossil evidence, they first appeared around 250 million years ago ( Ma ) and at least one species survived until about 90 million years ago, into

540-505: A 2-3-3-3-3 formula for the hand , meaning that the thumb has two phalanges, whilst the other fingers each have three. In the distal phalanges of the hand the centres for the bodies appear at the distal extremities of the phalanges, instead of at the middle of the bodies, as in the other phalanges. Moreover, of all the bones of the hand, the distal phalanges are the first to ossify. The distal phalanges of ungulates carry and shape nails and claws and these in primates are referred to as

630-541: A basal, or low, position in the diapsid tree. More analyses result in their being Neodiapsida , a derived diapsid subgroup. Since the 1980s, a close relationship was assumed between the Ichthyosauria and the Sauropterygia , another marine reptile group, within an overarching Euryapsida , with one such study in 1997 by John Merck showing them to be monophyletic archosauromorph euryapsids. This has been contested over

720-417: A better understanding of their anatomy. Owen had noticed that many fossils showed a downward bend in the rear tail. At first, he explained this as a post mortem effect, a tendon pulling the tail end downwards after death. However, after an article on the subject by Philip Grey Egerton , Owen considered the possibility that the oblique section could have supported the lower lobe of a tail fin. This hypothesis

810-530: A certain branch of the evolutionary tree. This also allows one to clearly indicate all relationships between the several subgroups in a cladogram . In 1999, a node clade Ichthyopterygia was defined by Motani as the group consisting of the last common ancestor of Ichthyosaurus communis , Utatsusaurus hataii and Parvinatator wapitiensis ; and all its descendants. Within Motani's phylogeny, the Ichthyopterygia were

900-538: A distinctive build compared to "ichthyosaurs proper" that Motani excluded them from the Ichthyosauria and placed them in a basal position in a larger clade , the Ichthyopterygia . However, this solution was not adopted by all researchers. The basal forms quickly gave rise to ichthyosaurs in the narrow sense sometime around the boundary between the Early Triassic and Middle Triassic ; the earliest Ichthyosauria in

990-523: A dorsal fin, and short flippers containing many phalanges. The sister group of the Mixosauria were the more advanced Merriamosauria . By the Late Triassic , merriamosaurs consisted of both the large, classic Shastasauria and more advanced, "dolphin-like" Euichthyosauria . Experts disagree over whether these represent an evolutionary continuum, with the less specialised shastosaurs a paraphyletic grade that

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1080-421: A giant lizard. In October 1805, a newspaper article reported the find of two additional skeletons, one discovered at Weston by Jacob Wilkinson , the other, at the same village, by Reverend Peter Hawker. In 1807, the last specimen was described by the latter's cousin, Joseph Hawker . This specimen thus gained some fame among geologists as 'Hawker's Crocodile'. In 1810, near Stratford-upon-Avon , an ichthyosaur jaw

1170-705: A larger number of articles and also brought the group to the attention of the general public. The new method of cladistics provided a means to exactly calculate the relationships between groups of animals, and in 1999, Ryosuke Motani published the first extensive study on ichthyosaur phylogenetics . In 2003, McGowan and Motani published the first modern textbook on the Ichthyosauria and their closest relatives. Two jawbones of gigantic ichthyosaur were discovered in 2016 and 2020 in Lilstock and Somerset respectively, UK. Simple scaling would suggest that this ichthyosaur has an estimated total length of up to 26 meters (82 feet),

1260-475: A lost skeleton. Conybeare considered that Ichthyosaurus had priority relative to Proteosaurus . Although this is incorrect by modern standards, the latter name became a "forgotten" nomen oblitum . In 1821, De la Beche and Conybeare provided the first systematic description of ichthyosaurs, comparing them to another newly identified marine reptile group, the Plesiosauria . Much of this description reflected

1350-448: A lower emargination, have been considered euryapsid or parapsid, and to have had their patterns of fenestration originate separately from those of diapsids. This includes araeoscelidans , mesosaurs , squamates , pleurosaurids , weigeltisaurids , protorosaurs , and trilophosaurs . With the exception of mesosaurs, which only have the lower temporal opening, all of these are universally agreed to be diapsids which either secondarily closed

1440-433: A revived interest in the group, leading to an increased number of named ichthyosaurs from all continents, with over fifty genera known. Ichthyosaurian species varied from 1 to 26 metres (3 to 85 ft) in length. Ichthyosaurians resembled both modern fish and dolphins. Their limbs had been fully transformed into flippers, which sometimes contained a very large number of digits and phalanges . At least some species possessed

1530-566: A shallow ocean during the Triassic. Several of these are in the collection of the University of California Museum of Paleontology. After a slack during the middle of the century, with no new genera being named between the 1930s and the 1970s, the rate of discoveries picked up towards its end. Other specimens are embedded in the rock and visible at Berlin–Ichthyosaur State Park in Nye County . In 1977

1620-473: A skeleton in 1819 at Whitby ; in his 1821 description, he expressed the hope that living specimens could still be found. Geologist Charles Lyell , to the contrary, assumed that the Earth was eternal so that in the course of time the ichthyosaur might likely reappear, a possibility lampooned in a famous caricature by De la Beche. Public awareness was increased by the works of the eccentric collector Thomas Hawkins ,

1710-520: A taxation by William Buckland and Gideon Mantell , sold his extensive collection, then the largest of its kind in the world, to the British Museum. However, curator Koenig quickly discovered that the fossils had been heavily restored with plaster, applied by an Italian artist from Lucca ; of the most attractive piece, an Ichthyosaurus specimen, almost the entire tail was fake. It turned out that Professor Buckland had been aware of this beforehand, and

1800-513: A young girl, secured the torso of the same specimen. Their mother, Molly Anning, sold the combined piece to squire Henry Henley for £23. Henley lent the fossil to the London Museum of Natural History of William Bullock . When this museum was closed, the British Museum bought the fossil for a price of £47/5s; it still belongs to the collection of the independent Natural History Museum and has

1890-529: Is an increase in the number of phalanges beyond the plesiomorphic mammal condition of three phalanges-per-digit. Hyperphalangy was present among extinct marine reptiles -- ichthyosaurs , plesiosaurs , and mosasaurs -- but not other marine mammals, leaving whales as the only marine mammals to develop this characteristic. The evolutionary process continued over time, and a very derived form of hyperphalangy, with six or more phalanges per digit, evolved convergently in rorqual whales and oceanic dolphins , and

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1980-491: Is based on Motani (1999): Utatsusaurus [REDACTED] Parvinatator Chaohusaurus [REDACTED] Grippia [REDACTED] Cymbospondylus [REDACTED] Mixosauria [REDACTED] Shastasauria [REDACTED] Toretocnemus Californosaurus [REDACTED] Macgowania Phalanx bone The phalanges / f ə ˈ l æ n dʒ iː z / ( sg. : phalanx / ˈ f æ l æ ŋ k s / ) are digital bones in

2070-443: The ungual phalanges . The term phalanx or phalanges refers to an ancient Greek army formation in which soldiers stand side by side, several rows deep, like an arrangement of fingers or toes. Most land mammals including humans have a 2-3-3-3-3 formula in both the hands (or paws ) and feet . Primitive reptiles usually had the formula 2-3-4-4-5, and this pattern, with some modification, remained in many later reptiles and in

2160-618: The Carnian and Norian , Shastosauria reached huge sizes. Shonisaurus popularis , known from a number of specimens from the Carnian of Nevada, was 15 m (49 ft) long. Norian Shonisauridae are known from both sides of the Pacific. Himalayasaurus tibetensis and Tibetosaurus (probably a synonym ) have been found in Tibet . These large (10- to 15-m-long) ichthyosaurs have by some been placed into

2250-593: The Cenomanian-Turonian boundary approximately 90 million years ago. Scientists became aware of the existence of ichthyosaurians during the early 19th century, when the first complete skeletons were found in England. In 1834, the order Ichthyosauria was named. Later that century, many finely preserved ichthyosaurian fossils were discovered in Germany, including soft-tissue remains. Since the late 20th century, there has been

2340-511: The Late Cretaceous . During the Early Triassic epoch , ichthyosaurs and other ichthyosauromorphs evolved from a group of unidentified land reptiles that returned to the sea, in a development similar to how the mammalian land-dwelling ancestors of modern-day dolphins and whales returned to the sea millions of years later, which they gradually came to resemble in a case of convergent evolution . Ichthyosaurians were particularly abundant in

2430-445: The Late Triassic and Early Jurassic periods, until they were replaced as the top aquatic predators by another marine reptilian group, the Plesiosauria , in the later Jurassic and Early Cretaceous , though previous views of ichthyosaur decline during this period are probably overstated. Ichthyosaurians diversity declined due to environmental volatility caused by climatic upheavals in the early Late Cretaceous, becoming extinct around

2520-653: The Society for Promoting Natural History as those of a crocodilian. In 1779, ichthyosaur bones were illustrated in John Walcott 's Descriptions and Figures of Petrifications . Towards the end of the eighteenth century, British fossil collections quickly increased in size. Those of the naturalists Ashton Lever and John Hunter were acquired in their totality by museums; later, it was established that they contained dozens of ichthyosaur bones and teeth. The bones had typically been labelled as belonging to fish, dolphins, or crocodiles;

2610-400: The hands and feet of most vertebrates . In primates , the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones . Toe bones or phalanges of the foot. Note the big toe has no middle phalanx. People vary; sometimes the smallest toe also has none (not shown). The phalanges are the bones that make up the fingers of

2700-460: The mammal-like reptiles . The phalangeal formula in the flippers of cetaceans (marine mammals) varies widely due to hyperphalangy (the increase in number of phalanx bones in the digits). In humpback whales , for example, the phalangeal formula is 0/2/7/7/3; in pilot whales the formula is 1/10/7/2/1. In vertebrates, proximal phalanges have a similar placement in the corresponding limbs, be they paw , wing or fin . In many species, they are

2790-491: The metacarpals of the hand or metatarsals of the foot at the metacarpophalangeal joint or metatarsophalangeal joint . The intermediate phalanx is not only intermediate in location, but usually also in size. The thumb and large toe do not possess a middle phalanx. The distal phalanges are the bones at the tips of the fingers or toes. The proximal, intermediate, and distal phalanges articulate with one another through interphalangeal joints of hand and interphalangeal joints of

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2880-401: The "hands" — the metacarpal and phalangeal bones — are elongated to the extent that they serve little use beyond locomotion. The giraffe , the largest even-toed ungulate, has large terminal phalanges and fused metacarpal bones able to absorb the stress from running. The sloth spends its life hanging upside-down from branches, and has highly specialized third and fourth digits for

2970-524: The 17-metre-long (56 ft) Triassic ichthyosaur Shonisaurus became the state fossil of Nevada. About half of the ichthyosaur genera determined to be valid were described after 1990. In 1992 Canadian paleontologist Elizabeth Nicholls uncovered the largest known specimen, a 23-metre-long (75 ft) Shastasaurus . The new finds have allowed a gradual improvement in knowledge about the anatomy and physiology of what had already been seen as rather advanced "Mesozoic dolphins". Christopher McGowan published

3060-562: The Cretaceous indicate that ichthyosaur diversity in the Late Jurassic must have been underestimated. Traditionally, ichthyosaurs were seen as decreasing in diversity even further with the Cretaceous , though they had a worldwide distribution. All fossils from this period were referred to a single genus: Platypterygius . This last ichthyosaur genus was thought to have become extinct early in

3150-565: The Early Triassic. Since 1959, a second enigmatic group of ancient sea reptiles is known, the Hupehsuchia . Like the Ichthyopterygia, the Hupehsuchia have pointed snouts and show polydactyly , the possession of more than five fingers or toes. Their limbs more resemble those of land animals, making them appear as a transitional form between these and ichthyosaurs. Initially, this possibility

3240-649: The Early and Early-Middle ( Olenekian and Anisian ) Triassic strata of Canada , China , Japan , and Spitsbergen in Norway , being up to 246 million years old. These first forms included the genera Chaohusaurus , Grippia , and Utatsusaurus . Even older fossils show they were around 250 million years ago, just two million years after the Permian mass extinction. This early diversity suggests an even earlier origin, possibly late Permian. They more resembled finned lizards than

3330-557: The Jurassic-Cretaceous boundary including Acamptonectes , Sveltonectes , Caypullisaurus , and Maiaspondylus . In 2013, a Cretaceous basal thunnosaurian was revealed: Malawania . Indeed, likely a radiation during the Early Cretaceous occurred due to an increase of coastlines when the continents further broke up. The demise of the ichthyosaurs has been described as a two-step process. A first extinction event in

3420-489: The Late Triassic, ichthyosaurs attained the peak of their size and diversity. They occupied many ecological niches . Some were apex predators ; others were hunters of small prey. Several species perhaps specialised in suction feeding or were ram feeders ; also, durophagous forms are known. Towards the end of the Late Triassic, a decline of variability seems to have occurred. The giant species seemed to have disappeared at

3510-640: The Middle Jurassic. This might be a result of the poor fossil record in general of this epoch. The strata of the Late Jurassic seem to indicate that a further decrease in diversity had taken place. From the Middle Jurassic onwards, almost all ichthyosaurs belonged to the thunnosaurian clade Ophthalmosauridae . Represented by the 4 m-long (13 ft) Ophthalmosaurus and related genera, they were very similar in general build to Ichthyosaurus . The eyes of Ophthalmosaurus were huge, and these animals likely hunted in dim and deep water. However, new finds from

3600-579: The Welshman Edward Lhuyd in his Lithophylacii Brittannici Ichnographia of 1699. Lhuyd thought that they represented fish remains. In 1708, the Swiss naturalist Johann Jakob Scheuchzer described two ichthyosaur vertebrae assuming they belonged to a man drowned in the Universal Deluge . In 1766, an ichthyosaur jaw with teeth was found at Weston near Bath . In 1783, this piece was exhibited by

3690-413: The advent of stone tool-making. However, the intrinsic hand proportions of australopiths and the resemblance between human hands and the short hands of Miocene apes, suggest that human hand proportions are largely plesiomorphic (as found in ancestral species) — in contrast to the derived elongated hand pattern and poorly developed thumb musculature of other extant hominoids . In Neanderthals ,

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3780-533: The apical tufts were expanded and more robust than in modern and early upper Paleolithic humans. A proposal that Neanderthal distal phalanges was an adaptation to colder climate (than in Africa) is not supported by a recent comparison showing that in hominins , cold-adapted populations possessed smaller apical tufts than do warm-adapted populations. In non-human, living primates the apical tufts vary in size, but they are never larger than in humans. Enlarged apical tufts, to

3870-526: The beginning of the Cenomanian eliminated two of the three ichthyosaur feeding guilds still present: the 'soft-prey specialists' and the 'generalists', leaving only an unspecialized apex predator group. The second extinction event took place during the Cenomanian-Turonian boundary event , a marine ' anoxic event ', after which just a single lineage survived, Platypterygius hercynicus , which then disappeared about 93 million years ago. Ichthyosaur extinction

3960-424: The creature to the fishes, as seemed to be confirmed by the flat shape of the vertebrae. At the same time, he considered it a transitional form between fishes and crocodiles, not in an evolutionary sense, but as regarded its place in the scala naturae , the "Chain of Being" hierarchically connecting all living creatures. In 1818, Home noted some coincidental similarities between the coracoid of ichthyosaurians and

4050-421: The direction of Richard Owen. Among them were three models of an ichthyosaur. Although it was known that ichthyosaurs had been animals of the open seas, they were shown basking on the shore, a convention followed by many nineteenth century illustrations with the aim, as Conybeare once explained, of better exposing their build. This led to the misunderstanding that they really had an amphibious lifestyle. The pools in

4140-427: The distal phalanges of the finger, are smaller and are flattened from above downward; each presents a broad base for articulation with the corresponding bone of the second row, and an expanded distal extremity for the support of the nail and end of the toe. In the hand, the distal phalanges are flat on their palmar surface, small, and with a roughened, elevated surface of horseshoe form on the palmar surface, supporting

4230-440: The early appearance of ichthyosaurs in the fossil record, and also their lack of clear affinities with other reptile groups, as anapsids were supposed to be little specialised. This hypothesis has become unpopular for being inherently vague because Anapsida is an unnatural, paraphyletic group. Modern exact quantitative cladistic analyses consistently indicate that ichthyosaurs are members of the clade Diapsida . Some studies showed

4320-589: The end of the Norian. Rhaetian (latest Triassic) ichthyosaurs are known from England, and these are very similar to those of the Early Jurassic . A possible explanation is an increased competition by sharks , Teleostei , and the first Plesiosauria . Like the dinosaurs, the ichthyosaurs and their contemporaries, the plesiosaurs, survived the Triassic–Jurassic extinction event , and quickly diversified again to fill

4410-417: The extent they actually reflect expanded digital pulps, may have played a significant role in enhancing friction between the hand and held objects during Neolithic toolmaking. Among non-human primates phylogenesis and style of locomotion appear to play a role in apical tuft size. Suspensory primates and New World monkeys have the smallest apical tufts, while terrestrial quadrupeds and Strepsirrhines have

4500-408: The finger pulp. The flat, wide expansions found at the tips of the distal phalanges are called apical tufts. They support the fingertip pads and nails. The phalanx of the thumb has a pronounced insertion for the flexor pollicis longus (asymmetric towards the radial side), an ungual fossa, and a pair of unequal ungual spines (the ulnar being more prominent). This asymmetry is necessary to ensure that

4590-612: The fishes or dolphins to which the later, more familiar species were similar. Their bodies were elongated and they probably used an anguilliform locomotion, swimming by undulations of the entire trunk. Like land animals, their pectoral girdles and pelves were robustly built, and their vertebrae still possessed the usual interlocking processes to support the body against the force of gravity. However, they were already rather advanced in having limbs that had been completely transformed into flippers. They also were probably warm-blooded and viviparous . These very early "proto-ichthyosaurs" had such

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4680-444: The foot . Each phalanx consists of a central part, called the body , and two extremities. In the foot, the proximal phalanges have a body that is compressed from side to side, convex above, and concave below. The base is concave, and the head presents a trochlear surface for articulation with the second phalanx. The middle are remarkably small and short, but rather broader than the proximal. The distal phalanges, as compared with

4770-448: The foot differ from the hand in that they are often shorter and more compressed, especially in the proximal phalanges, those closest to the torso. A phalanx is named according to whether it is proximal , middle, or distal and its associated finger or toe. The proximal phalanges are those that are closest to the hand or foot. In the hand, the prominent, knobby ends of the phalanges are known as knuckles . The proximal phalanges join with

4860-518: The genus Shonisaurus . The gigantic Shonisaurus sikanniensis (considered as a shastasaurus between 2011 and 2013) whose remains were found in the Pardonet Formation of British Columbia , has been estimated to be as much as 21 m (69 ft) in length. Ichthyotitan , found in Somerset , has been estimated to be as much as 26 m long—if correct, the largest marine reptile known to date. In

4950-428: The hand and the toes of the foot. There are 56 phalanges in the human body, with fourteen on each hand and foot. Three phalanges are present on each finger and toe, with the exception of the thumb and big toe , which possess only two. The middle and far phalanges of the fourth and fifth toes are often fused together (symphalangism). The phalanges of the hand are commonly known as the finger bones. The phalanges of

5040-455: The insertion of the flexor pollicis longus . Another ridge at the base serves for the insertion of the extensor aponeurosis . The flexor insertion is sided by two fossae  — the ungual fossa distally and the proximopalmar fossa proximally. The number of phalanges in animals is often expressed as a "phalangeal formula" that indicates the numbers of phalanges in digits, beginning from the innermost medial or proximal. For example, humans have

5130-437: The insights of their friend, the anatomist Joseph Pentland . In 1835, the order Ichthyosauria was named by Henri Marie Ducrotay de Blainville . In 1840, Richard Owen named an order Ichthyopterygia as an alternative concept. The discovery of a hitherto unsuspected extinct group of large marine reptiles generated much publicity, capturing the imagination of both scientists and the public at large. People were fascinated by

5220-740: The inventory number NHMUK PV R1158 (formerly BMNH R.1158). It has been identified as a specimen of Temnodontosaurus platyodon . In 1814, the Annings' specimen was described by Professor Everard Home , in the first scientific publication dedicated to an ichthyosaur. Intrigued by the strange animal, Home tried to locate additional specimens in existing collections. In 1816, he described ichthyosaur fossils owned by William Buckland and James Johnson . In 1818, Home published data obtained by corresponding with naturalists all over Britain. In 1819, he wrote two articles about specimens found by Henry Thomas De la Beche and Thomas James Birch. A last publication of 1820

5310-419: The larger parent clade of a smaller stem clade Ichthyosauria that was defined as the group consisting of Ichthyosaurus communis and all species more closely related to Ichthyosaurus than to Grippia longirostris . Motani's concept of the Ichthyosauria was thus more limited than the traditional one that also contained basal forms, such as Grippia , Utatsusaurus , and Parvinatator . The following cladogram

5400-415: The largest known to date marine reptile. The fossils of this individual were dated to be 202 million-year-old. The origin of the ichthyosaurs is contentious. Until recently, clear transitional forms with land-dwelling vertebrate groups had not yet been found, the earliest known species of the ichthyosaur lineage being already fully aquatic. In 2014, a small basal ichthyosauriform from the upper Lower Triassic

5490-514: The largest. A study of the fingertip morphology of four small-bodied New World monkey species, indicated a correlation between increasing small-branch foraging and reduced flexor and extensor tubercles in distal phalanges and broadened distal parts of distal phalanges, coupled with expanded apical pads and developed epidermal ridges. This suggests that widened distal phalanges were developed in arboreal primates, rather than in quadrupedal terrestrial primates. Whales exhibit hyperphalangy. Hyperphalangy

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5580-492: The late Permian or the earliest Triassic. However, establishing their position within the amniote evolutionary tree has proven difficult, due to their heavily derived morphology obscuring their ancestry. Several conflicting hypotheses have been posited on the subject. In the second half of the 20th century, ichthyosaurs were usually assumed to be of the Anapsida , seen as an early branch of "primitive" reptiles. This would explain

5670-545: The late Cretaceous, during the Cenomanian about 95 million years ago, much earlier than other large Mesozoic reptile groups that survived until the very end of the Cretaceous. Two major explanations have been proposed for this extinction including either chance or competition from other large marine predators such as plesiosaurs . The overspecialisation of ichthyosaurs may be a contributing factor to their extinction, possibly being unable to 'keep up' with fast teleost fish, which had become dominant at this time, against which

5760-470: The longest and thickest phalanx ("finger" bone). The middle phalanx also has a corresponding place in their limbs, whether they be paw , wing , hoof or fin . The distal phalanges are cone-shaped in most mammals, including most primates, but relatively wide and flat in humans. The morphology of the distal phalanges of human thumbs closely reflects an adaptation for a refined precision grip with pad-to-pad contact. This has traditionally been associated with

5850-440: The lower lobe of the tail fin. Ichthyosaurians were air-breathing, warm-blooded, and bore live young. Many, if not all, species had a layer of blubber for insulation. Like other ancient marine reptiles, such as those in the clades Mosasauria and Plesiosauria , the genera in Ichthyosauria are not part of the clade Dinosauria . The first known illustrations of ichthyosaur bones, vertebrae, and limb elements were published by

5940-410: The lower opening (araeoscelids, trilophosaurs) or lost the lower bar (squamates, pleurosaurs, protorosaurs). Euryapsida was proposed by Edwin H. Colbert as a substitute for the earlier term Synaptosauria , originally created by Edward D. Cope for a taxon including sauropterygians, turtles and rhynchocephalians. Baur removed the rhynchocephalians from Synaptosauria and Williston later resurrected

6030-517: The many specimens found in his country. The amount of anatomical data was hereby vastly increased. Von Huene also travelled widely abroad, describing many fossils from locations outside of Europe. During the 20th century, North America became an important source of new fossils. In 1905, the Saurian Expedition led by John Campbell Merriam and financed by Annie Montague Alexander , found twenty-five specimens in central Nevada , which were under

6120-599: The museum was forced to reach a settlement with Hawkins, and gave the fake parts a lighter colour to differentiate them from the authentic skeletal elements. Ichthyosaurs became even more popular in 1854 by the rebuilding at Sydenham Hill of the Crystal Palace , originally erected at the world exhibition of 1851 . In the surrounding park , life-sized, painted, concrete statues of extinct animals were placed, which were designed by Benjamin Waterhouse Hawkins under

6210-525: The niches previously occupied by ichthyosaurs, although they had coexisted for 19 million years. The extinction was most likely the result of ecological change and volatility that caused changes in migration, food availability, and birthing grounds. This part of the Cretaceous was one in which many other marine extinctions occurred, including those of some types of microplankton , ammonites , belemnites , and reef-building bivalves . In modern phylogeny , clades are defined that contain all species forming

6300-423: The park were at the time subjected to tidal changes , so that fluctuations in the water level at intervals submerged the ichthyosaur statues, adding a certain realism. Remarkably, internal skeletal structures, such as the scleral rings and the many phalanges of the flippers, were shown at the outside. During the nineteenth century, the number of described ichthyosaur genera gradually increased. New finds allowed for

6390-404: The sense Motani gave to the concept, appear about 245 million years ago. These later diversified into a variety of forms, including the still sea serpent -like Cymbospondylus , a problematic form which reached ten metres in length, and smaller, more typical forms like Mixosaurus . The Mixosauria were already very fish-like with a pointed skull, a shorter trunk, a more vertical tail fin,

6480-485: The sit-and-wait ambush strategies of the mosasauroids proved superior. This model thus emphasised evolutionary stagnation, the only innovation shown by Platypterygius being its ten fingers. Recent studies, however, show that ichthyosaurs were actually far more diverse in the Cretaceous than previously thought. Fragments previously referred to "Platypterygius" have been found to be from several different taxa. As of 2012, at least eight lineages are known to have spanned

6570-468: The sternum of the platypus . This induced him to emphasize its status as a transitional form, combining, like the platypus, traits of several larger groups. In 1819, he considered it a form between newts , like the olm , and lizards; he then gave a formal generic name: Proteo-Saurus . However, in 1817, Karl Dietrich Eberhard Koenig had already referred to the animal as Ichthyosaurus , "fish saurian" from Greek ἰχθύς , ichthys , "fish". This name at

6660-448: The strange build of the animals, especially the large scleral rings in the eye sockets, of which it was sometimes erroneously assumed these would have been visible on the living animal. Their bizarre form induced a feeling of alienation , allowing people to realise the immense span of time passed since the era in which the ichthyosaur swam the oceans. Not all were convinced that ichthyosaurs had gone extinct: Reverend George Young found

6750-439: The support of the nail and end of the toe. The phalanx ends in a crescent-shaped rough cap of bone epiphysis  — the apical tuft (or ungual tuberosity/process) which covers a larger portion of the phalanx on the volar side than on the dorsal side. Two lateral ungual spines project proximally from the apical tuft. Near the base of the shaft are two lateral tubercles. Between these a V-shaped ridge extending proximally serves for

6840-431: The taxon, including only Sauropterygia ( Nothosauria and Plesiosauria ) and Placodontia in it. The terms Enaliosauria and Halisauria have also been used for a taxon including ichthyosaurs and sauropterygians. Some 21st century studies have found that ichthyosaurs, thalattosaurs and sauropterygians were close relatives, either as stem-archosaurs or as stem-saurians. [REDACTED] This article about

6930-402: The teeth had been seen as those of sea lions. The demand by collectors led to more intense commercial digging activities. In the early nineteenth century, this resulted in the discovery of more complete skeletons. In 1804, Edward Donovan at St Donats uncovered a four-metre-long (13 ft) ichthyosaur specimen containing a jaw, vertebrae, ribs, and a shoulder girdle. It was considered to be

7020-414: The thumb pulp is always facing the pulps of the other digits, an osteological configuration which provides the maximum contact surface with held objects. In the foot, the distal phalanges are flat on their dorsal surface. It is largest proximally and tapers to the distal end. The proximal part of the phalanx presents a broad base for articulation with the middle phalanx, and an expanded distal extremity for

7110-407: The time was an invalid nomen nudum and was only published by Koenig in 1825, but was adopted by De la Beche in 1819 in a lecture where he named three Ichthyosaurus species. This text would only be published in 1822, just after De la Beche's friend William Conybeare published a description of these species, together with a fourth one. The type species was Ichthyosaurus communis , based on

7200-937: The vacant ecological niches of the early Jurassic. During the Early Jurassic, the ichthyosaurs still showed a large variety of species, ranging from 1 to 10 m (3 to 33 ft) in length. Many well-preserved specimens from England and Germany date to this time and well-known genera include Eurhinosaurus , Ichthyosaurus , Leptonectes , Stenopterygius , and the large predator Temnodontosaurus . More basal parvipelvians like Suevoleviathan were also present. The general morphological variability had been strongly reduced, however. Giant forms, suction feeders and durophagous species were absent. Many of these genera possessed streamlined, dolphin-like thunniform bodies, although more basal clades like Eurhinosauria , which include Leptonectes and Eurhinosaurus , had longer bodies and long snouts. Few ichthyosaur fossils are known from

7290-517: The years, with the Euryapsida being seen as an unnatural polyphyletic assemblage of reptiles that happen to share some adaptations to a swimming lifestyle. However, more recent studies have shown further support for a monophyletic clade between Ichthyosauromorpha , Sauropterygia, and Thalattosauria as a massive marine clade of aquatic archosauromorphs originating in the Late Permian and diversifying in

7380-641: Was announced, a small species with a short snout, large flippers, and a stiff trunk. Its lifestyle might have been amphibious. Motani found it to be more basal than the Ichthyopterygia and named an encompassing clade Ichthyosauriformes . The latter group was combined with the Hupesuchia into the Ichthyosauromorpha . The ichthyosauromorphs were found to be diapsids. The proposed relationships are shown by this cladogram: Hupehsuchia Cartorhynchus Ichthyopterygia The earliest ichthyosaurs are known from

7470-485: Was confirmed by new finds from Germany . In the Posidonia Shale at Holzmaden , dating from the early Jurassic , already in the early nineteenth century, the first ichthyosaur skeletons had been found. During the latter half of the century, the rate of discovery increased to a few hundred each year. Ultimately, over four thousand were uncovered, forming the bulk of ichthyosaur specimens displayed. The sites were also

7560-403: Was dedicated to a discovery by Birch at Lyme Regis. The series of articles by Home covered the entire anatomy of ichthyosaurs, but highlighted details only; a systematic description was still lacking. Home was very uncertain how the animal should be classified. Though most individual skeletal elements looked very reptilian, the anatomy as a whole resembled that of a fish, so he initially assigned

7650-479: Was described that had been discovered in China with characteristics suggesting an amphibious lifestyle. In 1937, Friedrich von Huene even hypothesised that ichthyosaurs were not reptiles, but instead represented a lineage separately developed from amphibians. Today, this notion has been discarded and a consensus exists that ichthyosaurs are amniote tetrapods , having descended from terrestrial egg-laying amniotes during

7740-482: Was evolving into the more advanced forms, or whether the two were separate clades that evolved from a common ancestor earlier on. Euichthyosauria possessed more narrow front flippers, with a reduced number of fingers. Basal euichthyosaurs were Californosaurus and Toretocnemus . A more derived branch were the Parvipelvia , with a reduced pelvis, basal forms of which are Hudsonelpidia and Macgowania . During

7830-509: Was found that was combined with plesiosaur bones to obtain a more complete specimen, indicating that the distinctive nature of ichthyosaurs was not yet understood, awaiting the discovery of far better fossils. In 1811, in Lyme Regis , along the Jurassic Coast of Dorset , the first complete ichthyosaur skull was found by Joseph Anning , the brother of Mary Anning , who in 1812 while still

7920-403: Was largely neglected because the Hupehsuchia have a fundamentally different form of propulsion, with an extremely stiffened trunk. The similarities were explained as a case of convergent evolution. Furthermore, the descent of the Hupehsuchia is no less obscure, meaning a possible close relationship would hardly clarify the general evolutionary position of the ichthyosaurs. In 2014, Cartorhynchus

8010-441: Was likely associated with another wave of signaling within the interdigital tissues. In ungulates (hoofed mammals) the forelimb is optimized for speed and endurance by a combination of length of stride and rapid step; the proximal forelimb segments are short with large muscles, while the distal segments are elongated with less musculature. In two of the major groups of ungulates, odd-toed and even-toed ungulates, what remain of

8100-533: Was thus a pair of abrupt events rather than a long decline, probably related to the environmental upheavals and climatic changes in the Cenomanian and Turonian . Competition with early mosasaurs is unlikely to have been a contributing factor since large mosasaurs did not appear until 3 million years after the ichthyosaur extinction, filling the resulting ecological void left by the extinction of ichthyosaurs. Plesiosaurian polycoltylids perhaps also filled some of

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