Largest prehistoric animals

Caseasaurs (Caseasauria) The herbivorous Alierasaurus was the largest caseid and the largest amniote to have lived at the time, with an estimated length around . Cotylorhynchus hancocki is also large, with an estimated length and weight of at least and more than . Edaphosaurids (Edaphosauridae) '' The largest edaphosaurids were Lupeosaurus at long and Edaphosaurus, which could reach even more than in length. With weights of and respectively. Sphenacodontids (Sphenacodontidae) The biggest carnivorous synapsid of the Early Permian was Dimetrodon, which could reach and . The largest members of the genus Dimetrodon were also the world's first fully terrestrial apex predators. Tappenosauridae The Middle Permian Tappenosaurus was estimated at in length, nearly as large as the largest dinocephalians. Therapsids (Therapsida) Anomodonts (Anomodontia) '' compared to a human The plant-eating dicynodont Lisowicia bojani is the largest-known of all non-mammalian synapsids, at about long, tall, and in body mass. However, in 2019 its weight was later more reliably estimated by modelling its mass from the estimated total volume of its body. These estimates varied depending on the girth of its rib cage and the amount of soft tissue modelled around the skeleton, with an overall average weight of 5.9 metric tons (6.5 short tons), and a lowermost estimate with minimal body fat and other tissues at 4.9 metric tons (5.4 short tons) and a maximum of 7 metric tons (7.7 short tons) at its bulkiest. Biarmosuchians (Biarmosuchia) The Late Permian Eotitanosuchus (a possible synonym to Biarmosuchus) may have been over in length, possibly up to and more than in weight for adult specimens. Tapinocaninus pamelae was slightly smaller, volumetric models suggesting it weighed . • The largest carnivorous non-mammalian synapsids was the anteosaurid Anteosaurus, which was long, and weighed . Fully grown Titanophoneus from the same family Anteosauridae likely had a skull of long. Rubidgea atrox is the largest African gorgonopsian, with skull of nearly long. Other large gorgonopsians include Dinogorgon with skull of ~ long, Leontosaurus with skull of almost long, • The largest known scylacosaurid was Julognathus, with an estimated skull length of . • The largest lycosuchid therocephalian may have been Scymnosaurus major, with an estimated skull length of . It was thought that Scymnosaurus was similar in size to a modern hyena. Gorynychus sundyrensis was a large lycosuchid that reached similar size, with an estimated skull length of . Another large lycosuchid was Simorhinella with the an estimated skull length of ~. Non-mammalian cynodonts (Cynodontia) • The largest known non-mammalian cynodont, as well as the largest member of Cynognathia, is Scalenodontoides, a traversodontid, which had a maximum skull length of approximately based on a fragmentary specimen. • Paceyodon davidi was the largest of morganucodontans, cynodonts close to mammals. It is known by a right lower molariform in length, which is bigger than molariforms of all other morganucodontans. • The largest known docodont was Castorocauda, almost in length. == Mammals (Mammalia) ==

Non-therian mammals Gobiconodonts (Gobiconodonta) '' The largest gobiconodont and the largest well-known Mesozoic mammal was Repenomamus. The known adult of Repenomamus giganticus reached a total length of around and an estimated mass of . Gobiconodon was also a large mammal, Monotremes (Monotremata) ] • The largest known monotreme (egg-laying mammal) ever was the extinct long-beaked echidna species known as Murrayglossus hacketti, known from a couple of bones found in Western Australia. It was the size of a sheep, weighing probably up to . • The largest known ornithorhynchid is Obdurodon tharalkooschild. • Kollikodon ritchiei was likely the largest monotreme in the Mesozoic. Its body length could be up to a . Metatherians (Metatheria) '' compared to a human • The largest non-marsupial metatherian, as well as the largest carnivorous metatherian, was Proborhyaena gigantea, which is estimated to have weighed weigh . Another large metatherian was Thylacosmilus atrox, weighing , with one estimate suggesting . Australohyaena is another large metatherian, weighing up to . • Stagodontid mammal Didelphodon was one of the largest Mesozoic metatherians and all Cretaceous mammals. Its skull could reach over in length and a weight of complete animal was . Marsupials (Marsupialia) '' the largest marsupial • The largest known marsupial, and the largest metatherian, is the extinct Diprotodon, about long, standing tall and weighing up to . Fellow vombatiform Palorchestes azael was similar in length being around , with body mass estimates indicating it could exceed . • The largest known carnivorous marsupial was Thylacoleo carnifex. Measurements taken from a number of specimens show they averaged in weight. The largest known koala is the giant koala (Phascolarctos stirtoni) which has an estimated weight of , which is the same weight as a large contemporary male koala. The largest ever member of the Tasmanian devil genus was Sarcophilus laniarius which were around 15% larger and 50% heavier than modern devils. • The largest known kangaroo was an as yet unnamed species of Macropus, estimated to weigh , larger than the largest known specimen of Procoptodon, which could grow up to and weigh . Some species from the genus Sthenurus were similar in size or a bit larger than the extant grey kangaroo (Macropus giganteus). The largest ever tree kangaroo, Bohra, had an estimated body mass of . • The largest potoroid ever recorded was Borungaboodie, which was nearly 30% bigger than the largest living species and weighed up to . • The largest member of the Thylacinidae is Thylacinus megiriani, which is somewhat reasonably larger than the Tasmanian wolf (Thylacinus cynocephalus), and bigger than its fellow Miocene relative Thylacinus potens, usually being 57.3 kilograms in weight. Non-placental eutherians s'' Cimolestans (Cimolesta) The largest known cimolestan is Coryphodon, high at the shoulder, long and up to of mass. Barylambda was also a huge mammal, at . Wortmania and Psittacotherium from the group Taeniodonta were among the largest mammals of the Early Paleocene. Lived as soon as half a million years after K–Pg boundary, Wortmania reached in body mass. Psittacotherium, which appeared two million years later, reached . Close European relatives from the same family Pseudorhyncocyonidae had skulls of in length. Even-toed ungulates (Artiodactyla) '' was one of the largest extinct land-dwelling artiodactyl ungulates • The largest known land-dwelling artiodactyl was Hippopotamus antiquus, estimated to be 14.1 ft (4.3 m) in length and in weight. However, volumetric models suggests it was slightly smaller, weighing . other experts consider it to be smaller than Hippopotamus antiquus. were the largest-known entelodonts that ever lived, at long and high at the shoulder. The huge Andrewsarchus from the Eocene of Inner Mongolia had a skull about long though the taxonomy of this genus is disputed. '' • The largest bovine and bovid was possibly Bison latifrons. It reached a weight from to possibly , in length, shoulder height of , and had horns that spanned . The African giant buffalo (Syncerus antiquus) may have rivaled Bison latifrons in size. It reached weight from to , measured in length from muzzle to the end of the tail, in height at the withers, in height at the hindquarters, and the distance between the tips of its horns was as large as . and horn span of . The kouprey (Bos sauveli), reaching in shoulder height, has existed since the Middle Pleistocene and is also considered to be possibly extinct. • The long-legged Megalotragus is possibly the largest known alcelaphine bovid, bigger than the extant wildebeest. The tips of horns of M. priscus were located at a distance of about from each other. '' • The extinct cervid Irish elk (Megaloceros giganteus) reached over in height, in mass and could have antlers spanning up to across, about twice the maximum span for a moose's antlers. The giant moose (Cervalces latifrons) reached high and was twice as heavy as the Irish elk but its antler span at was smaller than that of Megaloceros. North American stag-moose (Cervalces scotti) reached in length and a weight of . • The largest known giraffid, aside from the extant giraffe, is Sivatherium, with a body weight of . • The largest protoceratid was Synthetoceras, it reached long and in mass. • The largest known wild suid to ever exist was Kubanochoerus gigas, having measured up to and stood around tall at the shoulder. Megalochoerus could be similar in size, possibly weighing or . • The largest tayassuid extinct Platygonus species were similar in size to modern peccaries especially giant peccary, at around in body length, and had long legs, allowing them to run well. They also had a pig-like snout and long tusks which were probably used to fend off predators. • The largest camelid was Titanotylopus from the Miocene of North America. It possibly reached and a shoulder height of over . The Syrian camel was twice as big as the modern camels. and tall. Camelops had legs 20% longer than that of the dromedary and was about tall at the shoulder, weighing about . • The anoplotheriid Anoplotherium is thought to have been capable of reaching up to in the case of A. commune and in the case of A. latipes. A. latipes in particular could have measured more than in length and in shoulder height. Because it was probably capable of facultative bipedalism, it could have been capable of standing over tall. Cetaceans (Cetacea) '' was the heaviest archeocete , B. cetiodes (dark blue) and B. isis'' '' was a huge ancient sperm whale, the largest of the macroraptorial sperm whales. • The heaviest archeocete was Perucetus, with weight estimated at , while length is estimated at . However, Motani and Pyenson in 2024 argued that it is extremely difficult for Perucetus to rival or exceed the blue whale in weight. They discussed that since Perucetus is much shorter than the blue whale in length, it should be at least 3.375 times denser or 1.83 times fatter to weigh heavier, which is impossible for vertebrates whose whole-body density range from 0.75 to 1.2. Motani and Pyenson tested the hypotheses of Bianucci and colleagues by performing various body mass estimation methods: the regression-based and volumetric mass estimation resulted in for a length range of , though the likely body mass range would fall within . They also claimed that the previous estimation is inflated by assumed isometry, and that the effect from pachyostosis on the estimation of body mass is not negligible as it resulted in underestimation. Paul and Larramendi (2025) further downsized Perucetus to 15-16 meters in length and 35-40 tonnes in weight. The longest of known Eocene archeocete whales was Basilosaurus at in length. • The largest squalodelphinid was Macrosqualodelphis at in length. • Some Neogene rorquals were comparable in size to modern huge relatives. Parabalaenoptera was estimated to be about the size of the modern gray whale, about long. Some balaenopterids perhaps rivaled the blue whale in terms of size, • The largest macroraptorial sperm whale is Livyatan, with an estimated length of 44–57 ft (13.5–17.5 m) and an estimated weight of 62.8 short tons (57 tonnes) based on the 17.5m estimate. Odd-toed ungulates (Perissodactyla) , †Elasmotherium'', white rhino, Indian rhino, black rhino and Sumatran rhino compared to a human '' • One of the largest known perissodactyls, and the second largest land mammal (see Palaeoloxodon namadicus) is an unnamed species of Dzungariotherium which may have been even larger than has been thought, estimated to be around . Its more famous relative, Paraceratherium, also grew to large sizes. The largest individual known from the species Paraceratherium transouralicum, was estimated at tall at the shoulders, in length from nose to rump, and in weight. • Some prehistoric horned rhinos also grew to large sizes. The biggest Elasmotherium reached up to long, high and weighed . or , at the shoulder height and in length. • Metamynodon, an amynodontid, reached in length, comparable to Hippopotamus in measurement and shape. • The giant tapir (Tapirus augustus) was the largest tapir ever, at about and tall at the shoulders. Earlier, this mammal was estimated even bigger, at tall, and assigned to the separate genus Megatapirus. • One of the biggest chalicotheres was Moropus. It stood about tall at the shoulder. • Late Eocene perissodactyls from the family Brontotheriidae attained huge sizes. The North American Megacerops (also known as Brontotherium in length, and in weight.Embolotherium from Asia was equal in size. • The largest prehistoric horse was Equus giganteus of North America. It was estimated to grow to more than and at the shoulders. The largest anchitherine equid was Hypohippus at , comparable to large modern domestic horses. Megahippus is another large anchitheriine. With the body mass of it was much heavier than most of its close relatives. Previously until the naming of P. giganteum in 1994, P. magnum was considered the largest species of Palaeotherium, potentially reaching in shoulder height and in length. Another palaeothere Cantabrotherium is estimated to have weighed about . and weighed up to . Dinoceratans (Dinocerata) '' was the largest of the Dinoceratans The largest known dinoceratan was Eobasileus with skull length of , tall at the back and tall at the shoulder. Another huge animal of this group was Uintatherium, with skull length of , tall at the shoulder, Another huge bear was the giant North American short-faced bear (Arctodus simus), with the average weight of and the maximum estimated at . There is a guess that the largest individuals of this species could reached even larger mass, up to . The largest males of the possibly disrupted subspecies of brown bear (Ursus arctos), steppe brown bear (Ursus arctos priscus), is also estimated to have weighed . Another large bear was Agriotherium africanum, this species was estimated to have initially estimated to have weighed , but more recent estimates suggest it could've weighed . • The biggest odobenid and one of the biggest pinnipeds to have ever existed is Pontolis magnus, with a skull length of (twice as large as the skulls of modern male walruses) Only the modern male elephant seals (Mirounga) reach similar sizes. The second largest prehistoric pinniped is Gomphotaria pugnax with a skull length of nearly . • One of the largest of prehistoric otariids is Thalassoleon, comparable in size to the biggest extant fur seals. An estimated weight of T. mexicanus is no less than . • The biggest known mustelid to ever exist was likely the giant otter, Enhydriodon omoensis. It exceeded in length, and would have weighed in at around , much larger than any other known mustelid, living or extinct. There were other giant otters, like Siamogale, at around and Megalenhydris, which was larger than a modern-day giant river otter. Megalictis was the largest purely terrestrial mustelid (although Enhydriodon had recently been mentioned as the largest mustelid that also happens to be a terrestrial predator Other huge mustelids include Perunium and hypercarnivorous Eomellivora, both from the Late Miocene. • The heaviest procyonid was possibly the South American Chapalmalania. It reached in body length with a short tail and , comparable in size to an American black bear (Ursus americanus). Another huge procyonid was Cyonasua, which weighted about , about the same size as a medium-sized dog. • The largest canid of all time was Epicyon haydeni, which stood tall at the shoulder, had a body length of and weighed , with the heaviest known specimen weighing up to . The largest wolf (Canis lupus) subspecies ever existed in Europe is the Canis lupus maximus from the Late Pleistocene of France. Its long bones are 10% larger than those of extant European wolves and 20% longer than those of C. l. lunellensis. The Late Pleistocene Italian wolf was morphometrically close to C. l. maximus. • The largest amphicyonid (bear-dogs) was a species of Pseudocyon weighing around , representing a very large individual. Feliformia giganteus'' and the modern domestic cat '' at the La Brea Tar Pits Museum • The largest barbourofelinae, as well as the largest nimravid, was Barbourofelis fricki, with the shoulder height of and could've weighed . However, a 2024 study estimated a slightly smaller mass of . Including supplementary materials The largest nimravinae was Quercylurus major as its fossils suggest it weighed similar in size to the modern-day lion and was scansorial. The closely related Dinailurictis bondali was slightly smaller weighing , making it as large as a lioness. Eusmilus adelos is considered the largest member of the hoplophonine subfamily, reaching a weight of , comparable to a small African lion. While it was assumed that Hoplophoneus occidentalis could've weighed , A 2012 study suggested this species could've weighed . • The largest machairodont (saber-toothed cats) felid was Amphimachairodus kabir, with the males possibly reaching . Smilodon populator was a close contender, with males weighing . is estimated to weigh . Another contender was Nimravides catocopis with the largest specimen weighing up to . An unnamed species of Xenosmilus thought to have weighed between . • The heaviest known pantherine felids were the extinct leonines Panthera fossilis, which has been estimated to have maximum weight of , the American lion (Panthera atrox), weighing up to , and the Natodomeri lion of eastern Africa, which was comparable in size to large members of P. atrox. The Ngangdong tiger (Panthera tigris soloensis), was estimated to have weighed up to , however this has been contested with some estimates suggesting the largest individuals weighed . • The largest feline felid was Acinonyx pleistocaenicus, with the largest specimen weighing . Its close relative, giant cheetah (Acinonyx pardinensis), reached , approximately twice as large as the modern cheetah. The North American Pratifelis was larger than the extant cougar. • The largest viverrid known to have existed is Viverra leakeyi, which was around the size of a wolf or small leopard at . • The largest known extinct hyena was the percrocutid hyena, Dinocrocuta gigantea. It was originally estimated to have weighed . However, recent weight estimates may suggest it may have weighed less. An individual with a skull length of , is estimated to have weighed . One specimen is reported to have a skull length of . Pachycrocuta brevirostris was another large extinct hyena. It's estimated at at the shoulder and weight. Crocuta hyenas have also been known large sizes, even larger than the extant spotted hyena, most notably the extinct spotted hyena subspecies, the cave hyena, with average individuals weighing . Crocuta eturno was another large Crocuta species with estimates suggesting this species could've weighed . • The extinct giant fossa (Cryptoprocta spelea) had a body mass in range from to , much larger than the modern fossa weighs (up to for adult males). Hyaenodonts (Hyaenodonta) • The largest hyainailourid, as well as the largest hyaenodont was Megistotherium osteothlastes at . Hyainailouros was another large hyainailourid. The largest species in the genus, H. bugtiensis, which could've weighed between . Oxyaenids (Oxyaenidae) '' The largest known oxyaenid was Sarkastodon weighing in at . and Ankalagon from North America. Another large mesonychian is Harpagolestes with a skull length of a half a meter in some species. • One of the largest known fossil bats overall was Archaeopteropus from Italy. With an estimated wingspan of , it rivalled the modern spectral bat and many flying foxes in size. Hedgehogs, gymnures, shrews, and moles (Eulipotyphla) '' skeleton The largest known animal of the group Eulipotyphla was Deinogalerix, measuring up to in total length, with a skull up to long. Rodents (Rodentia) (Castoroides ohioensis) • Several of the extinct South American dinomyids were much bigger than modern rodents. Josephoartigasia monesi was the largest-known rodent of all time, approximately weighing an estimated . Phoberomys pattersoni weighed . Another huge dinomyid, Telicomys gigantissimus had a minimal weight of . • The largest old world porcupine are the Hystrix refossa was larger than living porcupines. It was approximately 20% larger than its closest relative, the living Indian porcupine (H. indica), reaching lengths of over . Rabbits, hares, and pikas (Lagomorpha) The biggest known prehistoric lagomorph is the Minorcan giant rabbit Nuralagus rex at . Pangolins (Pholidota) The largest pangolin was the extinct Manis palaeojavanica Its total length is measured up to . Primates (Primates) '' • The largest known non-hominid primate is Gigantopithecus blacki. Studies estimate heights around tall, weighing . Some suggested that it would not exceed tall with a bipedal posture. Another giant ape was Meganthropus palaeojavanicus at in body height, although it is known from very poor remains. • During the Pleistocene, some archaic humans were close in sizes or even larger than early modern humans. Neanderthals (Homo neanderthalensis) reached and in average weight for males and females, respectively, larger than the parameters of modern humans (Homo sapiens) ( and for males and females, respectively). A tibia from Kabwe (Zambia) indicates an indeterminate Homo individual of possibly in height. It was one of the tallest humans of the Middle Pleistocene and noticeably large even compared to recent humans. The tallest Homo sapiens individuals from the Middle Pleistocene of Spain reached and for males and females, respectively. • The heaviest known Old World monkey is the prehistoric baboon Theropithecus oswaldi which have weighed , some even suggested to reach . A male specimen of Dinopithecus projected to weigh an average of and up to , exceeds the maximum weight record of the chacma baboon, the largest extant baboon. • The largest omomyids were Macrotarsius and Ourayia from the Middle Eocene. Both reached in weight. • Some prehistoric lemuriform primates grew to huge sizes as well. Archaeoindris was a sloth lemur that lived in Madagascar and weighed , as large as an adult male gorilla. Palaeopropithecus from the same family was also heavier than most modern lemurs, at . Megaladapis is another large extinct lemur at in length and an average body mass of around . Other estimates suggest but its still much larger than any extant lemur. In 2024, Biswas, Chang and Tsai estimated a maximum shoulder height of over 4.5 metres (15 ft) and suggested that the body mass for 5 measured specimens ranged from 13.2 to 18.5 tonnes (29,000 to 41,000 lb) from specimens from Taiwan. The largest individual reported individual of the steppe mammoth of Eurasia (Mammuthus trogontherii) was estimated to reach at the shoulders and in weight. Stegodon zdanskyi, the biggest species of Stegodon, was in body mass. • Deinotherium was the largest proboscidean in Deinotheriidae family. Bones retrieved in Crete confirm the existence of specimen tall at the shoulders and more than in weight. The weight of Steller's sea cows is estimated to be . Its direct ancestor, the Cuesta sea cow was around 9 m (30 ft) long and possibly 10 tonnes (11 short tonnes) in weight. Embrithopods (Embrithopoda) '' The largest known embrithopod was the arsinoitheriid Arsinoitherium. A. zitteli would have been tall at the shoulders, and long. A. giganteum reached even larger size than A. zitteli. Hyraxes (Hyracoidea) Some of the prehistoric hyraxes were extremely large compared to modern small relatives. The largest hyracoid ever evolved is Titanohyrax ultimus. With the mass estimation in rage of to over it was close in size to Sumatran rhinoceros. Another enormous hyrax is Megalohyrax which had skull of in length and reached the size of tapir. More recent Gigantohyrax was three times as large as the extant relative Procavia capensis, although it is noticeably smaller than earlier Megalohyrax and Titanohyrax. Desmostylians (Desmostylia) '' skeletal diagram The largest known desmostylian was a species of Desmostylus, with skull length of and comparable in size to the Steller's sea cow. Paleoparadoxia is also known as one of the largest desmostylians, with body length of . Glyptodonts, armadillos and pampatheres (Cingulata) The largest cingulate known is Doedicurus, at long, high and reaching a mass of approximately . The largest species of Glyptodon, Glyptodon clavipes, reached in length which is as big as a bull African bush elephant. However, many studies have gotten lower estimates, with one study suggesting that was the most accurate size estimate for an adult. The closely related ground sloth, Megatherium americanum, was slightly smaller, measuring in length, and weighed based on volumetric models. • The largest known mylodontoid was Lestodon armatus, estimated to have measured in length, and weighed . • The largest extinct anteater was Neotamandua borealis, which is estimated to have weighed between . Astrapotherians (Astrapotheria) The largest astrapotherian was Hilarcotherium miyou, with an estimated weight of . Other large astrapotherians that weighed weighed about , such as the genus Granastrapotherium and some species of Parastrapotherium (P. martiale). Litopterns (Litopterna) The largest known litoptern was Macrauchenia, which had three hoofs per foot. It was a relatively large animal, with a body length of around . Notoungulates (Notoungulata) s The largest notoungulate known of complete remains is Toxodon. It was about in body length, and about high at the shoulder and resembled a heavy rhinoceros. Although incomplete, the preserved fossils suggest that Mixotoxodon were the most massive member of the group, with a weight about . Pyrotherians (Pyrotheria) The largest mammal of the South American order Pyrotheria was Pyrotherium at in length and in weight. == Reptiles (Reptilia) ==

Lizards and snakes (Squamata) size estimates compared to a human • Mosasaurs are the largest-known squamates. The largest-known mosasaur is likely Mosasaurus hoffmanni, estimated at more than in length, however these estimations are based on heads and total body length ratio 1:10, which is unlikely for Mosasaurus, and probably that ratio is about 1:7. Another giant mosasaur is Tylosaurus, estimated at in length. Another mosasaur, Prognathodon reached similar sizes. • The largest known prehistoric snake is Titanoboa cerrejonensis, estimated at or even in length and . The madtsoiid Vasuki indicus may have rivaled or surpassed Titanoboa in length, however had smaller vertebral dimensions compared to it. A close rival in size to those snakes is palaeophiid marine snake Palaeophis colossaeus, which may have been around in length or even up to . Another known very large fossil snake is Gigantophis garstini, estimated at in length, although later study shows smaller estimation about . However, the authors noted that this estimate should be treated with caution. The largest fossil python is Liasis dubudingala with length roughly . The largest viper as well as the largest venomous snake ever recorded is Laophis crotaloides from the Early Pliocene of Greece. This snake reached over in length and in weight. Another huge fossil viper is indeterminate species of Vipera. With a length of around it was one of the biggest predators of Mallorca during the Early Pliocene. The largest known blind snake is Boipeba tayasuensis with estimated total length of . • The largest known terrestrial lizard is probably megalania (Varanus priscus), with the most recent studies estimating it to have been about in length. As extant relatives, megalania could have been venomous and in that case this lizard was also the largest venomous vertebrate ever evolved. Turtles, tortoises and close relatives (Pantestudines) Cryptodira • The largest known turtle ever was Archelon ischyros at long and . Possible second-largest sea turtle was Protostega at in total body length. There is even a larger specimen of this genus from Texas estimated at in total length. Another huge prehistoric sea turtle is the Late Cretaceous Gigantatypus, estimated at over in length. Psephophorus terrypratchetti from the Eocene attained in body length. • The largest tortoise was Megalochelys atlas at up to in shell length and weighing . M. margae had carapace of long; an unnamed species from Java reached at least in carapace length. Other giant tortoises include Centrochelys marocana at in carapace length and Mesoamerican Hesperotestudo sp. at in carapace length. Another huge trionychid is North American Axestemys byssinus at over in total length. Side-necked turtles (Pleurodira) '' The largest freshwater turtle of all time was the Miocene podocnemid Stupendemys, with an estimated parasagittal carapace length of and weight of up to . Carbonemys cofrinii from the same family had a shell that measured about , complete shell was estimated at . Macrobaenids (Macrobaenidae) The largest macrobaenids were the Early Cretaceous Yakemys, Late Cretaceous Anatolemys, and Paleocene Judithemys and Carbonemys. All reached in carapace length. Meiolaniformes '' The largest meiolaniid was Meiolania. Meiolania platyceps had a carapace long and probably reached over in total body length. An unnamed Late Pleistocene species from Queensland was even larger, up to in carapace length. Sauropterygians (Sauropterygia) Placodonts and close relatives (Placodontiformes) Placodus was among the largest placodonts, with a length of up to . Nothosaurs and close relatives (Nothosauroidea) The largest nothosaur as well as the largest Triassic sauropterygian was Nothosaurus giganteus at in length. Plesiosaurs (Plesiosauria) • The largest known plesiosauroid was an indeterminate specimen possibly belonging to Aristonectes (identified as cf. Aristonectes sp.), with a body length of and body mass of . Another long plesiosauroid was Albertonectes at . Thalassomedon rivaled it in size, with its length at . Other large plesiosauroids are Styxosaurus and Elasmosaurus. Both reached some more than in length. Hydralmosaurus (previously synonymized with Elasmosaurus and Styxosaurus) reached in total body length. ''. • There is much controversy over the largest-known of the Pliosauroidea. Pliosaurus funkei (also known as "Predator X") is a species of large pliosaur, known from remains discovered in Norway in 2008. This pliosaur has been estimated at in length. However, in 2002, a team of paleontologists in Mexico discovered the remains of a pliosaur nicknamed as "Monster of Aramberri", which is also estimated at in length, with shorter estimation about . This species is, however, claimed to be a juvenile and has been attacked by a larger pliosaur. Some media sources claimed that Monster of Aramberri was a Liopleurodon but its species is unconfirmed thus far. The Early Cretaceous Kronosaurus queenslandicus is estimated at in length and in weight. Close contender in size was the Late Cretaceous Megacephalosaurus eulerti with a length in range of . Proterosuchids (Proterosuchidae) Proterosuchus fergusi is the largest known proterosuchid with a skull length of and a possible body length of . Erythrosuchids (Erythrosuchidae) '' The largest erythrosuchid was Erythrosuchus africanus with a maximum length of . Phytosaurs (Phytosauria) Some of the largest known phytosaurs include Redondasaurus with a length of and Smilosuchus with a length of more than . Non-crocodylomorph pseudosuchians (Pseudosuchia) '' to a human • The largest shuvosaurid and one of the largest pseudosuchian from the Triassic period was Sillosuchus. Biggest specimens could have reached in length. • The largest known carnivorous pseudosuchian of the Triassic is loricatan Fasolasuchus tenax, which measured an estimated of . It is both the largest "rauisuchian" known to science, and the largest non-dinosaurian terrestrial predator ever discovered. Biggest individuals of Postosuchus and Saurosuchus had a body length of around . A specimen of Prestosuchus discovered in 2010 suggest that this animal also reached lengths of nearly making it one of the largest Triassic pseudosuchians. • Desmatosuchus was likely one of the largest known aetosaurs, about in length and in weight. Crocodiles and close relatives (Crocodylomorpha) , †Purussaurus'', †Gryposuchus, †Euthecodon, †Sarcosuchus, and modern Crocodylus porosus) compared to a human , †Machimosaurus, †Barinasuchus, †Sarcosuchus, modern Crocodylus porosus, and †Purussaurus'') Aegyptosuchids (Aegyptosuchidae) The Late Cretaceous Aegisuchus was originally estimated to reach in length by the lower estimate and as much as by the upper estimate although a length of over 15 m is likely a significant overestimate. However, this estimation is likely to be a result of miscalculation, and its length would be only around . Crocodylians (Crocodylia) • The largest caiman and likely one of the largest crocodylians was Purussaurus brasiliensis estimated at . According to another information, maximum estimate measure and almost in length and in weight respectively. However, a 2022 study estimated a length of 7.6–9.2 metres (25–30 ft) and a mass of 2–6.2 metric tons (2.2–6.8 short tons) using a phylogenetic approach; and a length of 9.2–10 metres (30–33 ft) and mass of 3.9–4.9 metric tons (4.3–5.4 short tons) using a non-phylogenetic approach. • Another giant caiman was Mourasuchus. Various estimates suggest the biggest specimens reached in length and in weight. but more recent estimates suggest in body length. However, the 2025 study which reclassified Deinosuchus as a eusuchian crocodylomorph stated that previous estimates may have overestimated its size as the genus has a relatively long snout, but these were based on taxa with shorter snouts (such as the American alligator). The authors estimated that D. riograndensis most likely reached total lengths of . • The largest extinct species of the genus Alligator was the Haile alligator (Alligator hailensis), which had a skull long and was similar in size to the extant American alligator (Alligator mississippiensis). • The largest gavialids were Asian Rhamphosuchus at and indeterminate species from Kali Gedeh (Java) at in length. • The largest known mekosuchian is Paludirex vincenti, which is estimated to reach up to . Partial jaw specimen from Pliocene that is attributed to Quinkana suggest an individual about in length, Paralligatorids (Paralligatoridae) The largest paralligatorid was likely Kansajsuchus, estimated at up to long. Tethysuchians (Tethysuchia) • Some extinct pholidosaurids reached giant sizes. In the past, Sarcosuchus imperator was believed to be the largest crocodylomorph, with initial estimates proposing a length of and a weight of . However, recent estimates have now shrunk to a length of and a weight of . Related to Sarcosuchus, Chalawan thailandicus could have reached more than in length, although other estimates suggest . Notosuchians (Notosuchia) • Some of largest terrestrial notosuchian crocodylomorphs were the Miocene sebecid Barinasuchus, with a skull of long, and Eocene sebecid Dentaneosuchus with estimated mandible length of . Various estimates suggest a possible length of these animals between . Using proportion of Stratiotosuchus which is also large to have long skull, Barinasuchus is estimated to have length at least . Thalattosuchians (Thalattosuchia) '' compared to a human • The largest thalattosuchian as well as the largest teleosauroid was unnamed fossil remain from Paja Formation, which may belongs to animal with length of , which is as large as outdated length estimate of the Early Cretaceous Machimosaurus rex, more recently estimated at in length. Neosteneosaurus edwardsi (previously known as Steneosaurus edwardsi) was the biggest Middle Jurassic crocodylomorph, it reached long. Other huge metriorhynchids include Tyrannoneustes at in length and Torvoneustes at in length. Basal crocodylomorphs Redondavenator was the largest Triassic crocodylomorph ever recorded, with a skull of at least in length. Another huge basal crocodylomorph was Carnufex Pterosaurs (Pterosauria) (A-B), Arambourgiania (C) and Quetzalcoatlus sp.'' (D-E) • The largest known pterosaur was Quetzalcoatlus northropi, at and with a wingspan of . Another close contender is Hatzegopteryx, also with a wingspan of or more. Yet another possible contender for the title is Cryodrakon which had a wingspan. According to various assumptions, the wingspan of Arambourgiania philadelphiae reached from to more than . South American Tropeognathus reached the maximum wingspan of . • The largest of non-pterodactyloid pterosaurs as well as the largest Jurassic pterosaur was Dearc, with an estimated wingspan between and . Only a fragmentary rhamphorhynchid specimen from Germany could be larger (184% the size of the biggest Rhamphorhynchus). Other large non-pterodactyloid pterosaurs were Sericipterus, Campylognathoides and Harpactognathus, with the wingspan of , , Tanystropheids (Tanystropheidae) , note that anatomical features based on smaller species T. longobardicus, while size is based on T. hydroides'' Tanystropheus, the largest of all tanystropheids, reached up to in length. Thalattosaurs (Thalattosauria) The largest species of thalattosaur, Miodentosaurus brevis grew to more than in length. The second largest member of this group is Concavispina with a length of . Ichthyosaurs (Ichthyosauria) '' compared to a human • The largest known shastasaur, ichthyosaur and marine reptile was Ichthyotitan, which is estimated to have measured . The Aust specimen (informally known as Aust Colossus) could've measured over . Another large shastasaur Shastasaurus sikanniensis at in length and in weight. • Although considerably smaller than Cymbospondylus youngorum, Thalattoarchon saurophagis is also reasonably large, being at and around , with a skull at . Pareiasaurs (Pareiasauria) Largest pareiasaurs reached up to in length. Such sizes had Middle Permian Bradysaurus, Embrithosaurus, and Nochelesaurus from South Africa, and the Late Permian Scutosaurus from Russia. is the largest known captorhinid. The second largest captorhinid was Labidosaurikos with the largest adult skull specimen long. == Non-avian dinosaurs (Dinosauria) ==

Sauropodomorphs (Sauropodomorpha) The largest of non-sauropod sauropodomorphs ("prosauropod") was Euskelosaurus. It reached in length and in weight. Another huge sauropodomorph Yunnanosaurus youngi reached long. Sauropods (Sauropoda) dinosaurs (from left to right): Supersaurus, Argentinosaurus, Diplodocus, Mamenchisaurus, and Sauroposeidon • A mega-sauropod, Maraapunisaurus fragillimus (previously known as Amphicoelias fragillimus), is a contender for the largest-known dinosaur in history. It has been estimated at in maximum length and in weight. Unfortunately, the fossil remains of this dinosaur have been lost. • Known from the incomplete and now disintegrated remains, the Late Cretaceous Bruhathkayosaurus matleyi was an anomalously large sauropod. Informal estimations suggested as huge parameters as in length and in weight. Some estimates, however, suggest and but it's still much heavier than most other sauropods. More recent estimations by Gregory Paul in 2023 has placed its weight range around to a . If true, it would make Bruhathkayosaurus the single largest terrestrial animal to have walked the earth and would have rivalled the largest blue whale recorded. • BYU 9024, a massive cervical vertebra found in Utah, may belong to a Barosaurus lentus or Supersaurus vivianae Supersaurus vivianae itself may have been the longest dinosaur yet discovered as a study of 3 specimens suggested length of or over . '' • Mamenchisaurus sinocanadorum was likely the largest mamenchisaurid, reaching nearly in length and in weight. Originally thought to be a brachiosaurid, it was later identified as a huge diplodocoid, possibly in length and in weight. • The tallest sauropod was Sauroposeidon proteles with estimated height at . Asiatosaurus could potentially reach in height, but this animal is known only from teeth. Giraffatitan was estimated at in height. '' Other huge sauropods include Argentinosaurus, Alamosaurus, and Puertasaurus with estimated lengths of and weights of . Patagotitan was estimated at in length and in average weight, and was similar in size to Argentinosaurus and Puertasaurus. Giant sauropods like Supersaurus, Sauroposeidon, and Diplodocus probably rivaled them in length but not in weight. Turiasaurus is considered the largest dinosaur from Europe, • Brachiosaurus nougaredi is yet another large brachiosaur from Early Cretaceous North Africa. The remains have been lost, but the sacrum drawing remains. It suggests a sacrum of almost long, making it the largest dinosaur sacrum discovered so far, except those of Argentinosaurus and Apatosaurus. • In 2010, the femur of a large sauropod was discovered in France. The femur suggests an animal that grew to immense sizes. Non-avian theropods (Theropoda) dinosaurs (from left to right): Spinosaurus, Giganotosaurus, Tyrannosaurus, Mapusaurus, and Carcharodontosaurus • The largest individual theropod as well as the largest individual terrestrial predator yet known is a Tyrannosaurus rex specimen nicknamed Scotty (RSM P2523.8), located at the Royal Saskatchewan Museum and reported to measure 13 m (43 ft) in length. Using a mass estimation technique that extrapolates from the circumference of the femur, Scotty was estimated as the largest known specimen at 8.87 metric tons (9.78 short tons) in body mass • Other large theropods of comparable size were Giganotosaurus carolinii, and Spinosaurus aegyptiacus, whose largest specimens known estimated at and in length, and weigh between and 14 m (46 ft) in length and 7.4 metric tonnes (8.2 short tons) respectively (which makes Spinosaurus the longest terrestrial carnivore). Some other notable giant theropods (e.g. Carcharodontosaurus, Acrocanthosaurus, and Mapusaurus) may also have rivaled them in size. • Macroelongatoolithus, ranging from in length, is the largest known type of dinosaur egg. Armoured dinosaurs (Thyreophora) The largest-known thyreophoran was Ankylosaurus at in length and in weight. Stegosaurus was also long but around tonnes in weight. Marginocephalians (Marginocephalia) Pachycephalosaurs (Pachycephalosauria) The largest pachycephalosaur was the eponymous Pachycephalosaurus. Previously claimed to be at in length, Ceratopsians (Ceratopsia) (from left to right): Nasutoceratops, Styracosaurus, Centrosaurus, Pachyrhinosaurus, Triceratops, Pentaceratops, Chasmosaurus, and Anchiceratops The largest ceratopsian known is Triceratops horridus, along with the closely related Eotriceratops xerinsularis both with estimated lengths of . Pentaceratops and several other ceratopsians rival them in size. Titanoceratops had one of the longest skull of any land animal, at long. A recently discovered Torosaurus (nicknamed "Adam") may exceed this size with a skull length of meters. Ornithopods (Ornithopoda) , Magnapaulia laticaudus, Edmontosaurus annectens, Saurolophus angustirostris, Hypsibema missouriensis, Charonosaurus jiayinensis, Iguanodon bernissartensis'' • The very largest known ornithopods, like Shantungosaurus were as heavy as medium-sized sauropods at up to , and in length. Magnapaulia reached in length, or, according to original description, even . Such animal could weighed up to . An estimated maximum length of Brachylophosaurus is resulting in weight of . PASAC-1, informally named "Sabinosaurus", is the largest well-known North American saurolophine, around long, that is about 20% larger than other known specimens. Hypsibema missouriensis was up to long. The Late Cretaceous Charonosaurus was estimated around in length and in weight. • The largest ornithopod outside of Hadrosauroidea was likely the Iguanodon. Biggest specimens reached in length and weighed around . Another large ornithopod is Iguanacolossus, with in length and in weight. • The largest rhabdodontid was Matheronodon, estimated at in length. Rhabdodon reached approximately and according to 2016 estimates. == Birds (Aves) ==

, †Megalapteryx didinus, †Euryapteryx curtus, Casuarius casuarius, †Pachyornis elephantopus, Rhea americana, Struthio camelus, †Dinornis novaezealandiae, †Aepyornis maximus'' The largest bird in the fossil record may be the extinct elephant bird species Aepyornis maximus of Madagascar, whose closest living relative is the kiwi. Giant elephant birds exceeded in height, and average a mass of The largest fowl was the mihirung Dromornis stirtoni of Australia. It exceeded in height, and average a mass of The tallest recorded bird was Pachystruthio dmanisensis, a relative of the ostrich. This particular species of bird stood at tall and average a mass of and wingspan comparable to some of the modern gulls, around . Gurilynia was the largest Mesozoic bird from Mongolia, with a length of , hip height of , and weight of . Pengornithidae One of the biggest Early Cretaceous enantiornithine bird was Pengornis at in length Gargantuaviidae Gargantuavis is the largest known bird of the Mesozoic, a size ranging between the cassowary and the ostrich, and a mass of like modern ostriches. In 2019 specimens MDE A-08 and IVPP-V12325 were measured at in length, in hip height, and in weight. and in mass for males. Gastornid (Gastornithiformes) Large individuals of Gastornis reached up to in height. Weight of Gastornis ranges from to and sometimes to for European specimens and from to for North American. Waterfowl (Anseriformes) '' Possibly flightless, the Miocene Garganornis ballmanni was larger than any extant members of Anseriformes, with in body mass. Another huge anseriform was the flightless New Zealand goose (Cnemiornis). It reached , approaching in size to small species of moa. Swans (Cygnini) The largest known swan was the Pleistocene giant swan (Cygnus falconeri), which reached a bill-to-tail length of about , a weight of around , and a wingspan of . The New Zealand swan (Cygnus sumnerensis) weighed up to , compared to the related extant black swan at only . The large marine swan Annakacygna yoshiiensis from the Miocene of Japan far exceeded the extant mute swan in both size and weight. Anatinae Finsch's duck (Chenonetta finschi) reached in weight, surpassing related modern Australian wood duck (). Pelicans, ibises and allies (Pelecaniformes) • The Early Pliocene Pelecanus schreiberi was larger than most extant pelicans. Pelecanus odessanus from the Late Miocene was probably the same size as P. schreiberi, its tarsometatarsus is long. • The largest heron was the Bennu heron (Ardea bennuides). Based on remains discovered, it was approximately tall and had a wingspan up to , thus surpassing the size of the largest living species in the heron family, the goliath heron. • The Jamaican ibis (Xenicibis xympithecus) was a large ibis, weighing about 2 kg (70 oz). Storks and allies (Ciconiiformes) '' compared in size to a human The largest known of Ciconiiformes was Leptoptilos robustus, standing tall and weighing an estimated . Cranes (Gruiformes) A large true crane (Gruinae) from the late Miocene (Tortonian) of Germany was equal in size to the biggest extant cranes and resembled the long-beaked Siberian crane (Leucogeranus leucogeranus). Shorebirds (Charadriiformes) Miomancalla howardi was the largest known charadriiform of all time, weighing approximately 0.6 kg (1.3 lb) more than the second-largest member, the great auk (Pinguinus impennis). Hesperornithines (Hesperornithes) The largest known of the hesperornithines was Canadaga arctica at long. New World vultures (Cathartiformes) '' One of the heaviest flying birds of all time was Argentavis, a Miocene teratornithid. The immense bird had a wingspan estimated up to and a weight up to . Another huge teratorn was Aiolornis, with a wingspan of around . The Pleistocene Teratornis merriami reached and in wingspan, with lower size estimates still exceeding the largest specimens of California condor (Gymnogyps californianus). Seriemas and allies (Cariamiformes) '' and a human The largest known-ever Cariamiforme and largest phorusrhacid or "terror bird" (highly predatory, flightless birds of America) was Brontornis, which was about tall at the shoulder, could raise its head above the ground and could have weighed as much as . The immense phorusrhacid Kelenken stood tall with a skull long ( of which was beak), had the largest head of any known bird. The largest North American phorusrhacid was Titanis, which reached a height of approximately 2.5 m (8.2 ft), slightly taller than an African forest elephant. Accipitriforms (Accipitriformes) , the largest bird of prey, attacking moa The largest known bird of prey ever was the enormous Haast's eagle (Hieraaetus moorei), with a wingspan of , relatively short for their size. Total length was probably up to in female and they weighed about . Another giant extinct hawk was Titanohierax about that lived in the Antilles and The Bahamas, where it was among the top predators. An unnamed late Quaternary eagle from Hispaniola could be 15–30% larger than the modern golden eagle (Aquila chrysaetos). Some extinct species of Buteogallus surpassed their extant relatives in size. Buteogallus borrasi was about 33% larger than the modern great black hawk (B. urubitinga). B. daggetti, also known as "walking eagle", was around 40% larger than the savanna hawk (B. meridionalis). Eyles's harrier (Circus eylesi) from the Pleistocene-Holocene of New Zealand was more than twice heavier than the extant C. approximans. Moa (Dinornithiformes) (Dinornis robustus) was the tallest known bird. The tallest known bird was the South Island giant moa (Dinornis robustus), part of the moa family of New Zealand that went extinct about 500 years ago. It stood up to tall, and weighed approximately half as much as a large elephant bird due to its comparatively slender frame. Elephant birds (Aepyornithiformes) The largest bird in the fossil record may be the extinct elephant birds (Vorombe, Aepyornis) of Madagascar, which were related to the ostrich. They exceeded in height and in weight. Ostriches (Struthioniformes) With in body mass, Pachystruthio dmanisensis from the lower Pleistocene of Crimea was the largest bird ever recorded in Europe. Despite its giant size, it was a good runner. A possible specimen of Pachystruthio from the lower Pleistocene of Hebei Province (China) was about in weight, twice heavier than the common ostrich (Struthio camelus). Remains of the massive Asian ostrich (Struthio asiaticus) from the Pliocene indicate a size 20% bigger than adult male of the extant Struthio camelus. Pigeons and doves (Columbiformes) from the early 1600s. The largest pigeon relative known was the dodo (Raphus cucullatus), possibly exceeding in height and weighing as much as , although recent estimates have indicated that an average wild dodo weighed much less at approximately . Songbirds (Passeriformes) The largest known songbird is the extinct giant grosbeak (Chloridops regiskongi) at long. Cormorants and allies (Suliformes) or Pallas's Cormorant (Phalacrocorax perspicillatus) • The largest known cormorant was the spectacled cormorant of the North Pacific (Phalacrocorax perspicillatus), which became extinct around 1850 and averaged around and . • The largest known plotopterid, penguin-like flightless bird was Copepteryx titan that is known from long femur, almost twice as long as that of emperor penguin. Grebes (Podicipediformes) The largest known grebe, the Atitlán grebe (Podylimbus gigas), reached a length of about . Bony-toothed birds (Odontopterygiformes) The largest known of the Odontopterygiformes— a group which has been variously allied with Procellariiformes, Pelecaniformes and Anseriformes and the largest flying birds of all time other than Argentavis were the huge Pelagornis, Cyphornis, Dasornis, Gigantornis and Osteodontornis. They had a wingspan of and stood about tall. Exact size estimates and judging which one was largest are not yet possible for these birds, as their bones were extremely thin-walled, light and fragile, and thus most are only known from very incomplete remains. Woodpeckers and allies (Piciformes) The largest known woodpecker is the possibly extinct imperial woodpecker (Campephilus imperialis) with a total length of about . Parrots (Psittaciformes) The largest known parrot is the extinct Heracles inexpectatus with a length of about 1 meter (3.3 feet). Penguins (Sphenisciformes) '' One of the heaviest penguins ever known is Kumimanu fordycei, with a body mass estimate of , derived from humerus measurements. Another example is Palaeeudyptes klekowskii of Antarctica, with a bill-to-tail length estimated at and an estimated body weight of , slightly smaller than previous estimates. The Eocene Anthropornis nordenskjoeldi is comparable in size, and was once estimated to reach lengths of and a weight of . However, recent estimation from humerus measurements put A. nordenskjoeldi more in the range of in weight. == Amphibians (Amphibia) ==

Lissamphibians (Lissamphibia) Frogs and toads (Anura) '' The largest known frog ever was an as yet unnamed Eocene species that was about . The Late Cretaceous Beelzebufo grew to at least (snout-vent length), which is around the size of a modern African bullfrog. Salamanders, newts and allies (Urodela) '' size comparison • Andrias matthewi was the largest lissamphibian ever known, with total length up to . • Habrosaurus was the largest sirenid. It reached long. Diadectomorphs (Diadectomorpha) '' The largest known diacectid, herbivorous Diadectes, was a heavily built animal, up to long, with thick vertebrae and ribs. Anthracosauria The largest known anthracosaur was Anthracosaurus, with skull about in length. Embolomeri '' The longest member of this group was Eogyrinus attheyi, species sometimes placed under genus Pholiderpeton. Its skull had length about . Temnospondyls (Temnospondyli) '' The largest known temnospondyl, as well as the largest amphibian, was Prionosuchus, which grew to lengths of . Unnamed species of temnospondyl from Lesotho is partial, but possible body length estimation is . Another huge temnospondyl was Mastodonsaurus giganteus at long. Another large temnospondly was Koolasuchus, which measured in length and weighed . == Fishes (Pisces) ==

Fishes are a paraphyletic group of non-tetrapod vertebrates. Jawless fish (Agnatha) Conodonts (Conodonta) Iowagnathus grandis is estimated to have length over . Heterostracans (Heterostraci) Some members of Psammosteidae such as Obruchevia and Tartuosteus are estimated to reached up to . Thelodonts (Thelodonti) Although known from partial materials, Thelodus parvidens (=T. macintoshi) is estimated to reached up to . Cephalaspidomorphs (Cephalaspidomorphi) A species of Parameteoraspis reached up to . Spiny sharks (Acanthodii) The largest of the now-extinct Acanthodii was Xylacanthus grandis, an ischnacanthiform based on a ~ long jaw bone. Based on the proportions of its relative Ischnacanthus, X. grandis had an estimated total length of . Placoderms (Placodermi) '' skull The largest known placoderm was the giant predatory Dunkleosteus. The largest and most well known species was D. terrelli, was initially estimated to be in length and in weight. However, more recent reconstructions suggest estimates over is poorly supported. Instead the largest D. terrelli probably measured in length and weighed . Another large placoderm, Titanichthys clarki, may have rivaled it in size. Recent reconstructions suggest T. clarki was estimated to have a length around . is by far the biggest mackerel shark as well as non-tetropod fish ever known. Most estimates of megalodon's size extrapolate from teeth, with maximum length estimates up to with a 2025 study estimating a maximum length estimate of and modal length estimates based on individuals from all ontogenetic stages (life stages) of . Due to fragmentary remains, there have been many contradictory size estimates for megalodon, as they can only be drawn from fossil teeth and vertebrae. With the 2025 study suggesting that the animal had a more elongated slender appearance. Related to megalodon, Otodus angustidens and O. chubutensis reached the large sizes too. Each was estimated at and , respectively. • Other giant mackerel sharks were Pseudoscapanorhynchidae from the Cretaceous period. Cretodus had a size range of (for C. crassidens), Leptostyrax reached lengths of . • The Cenozoic Parotodus reached up to in length. • The heaviest thresher shark was likely Alopias grandis. It was similar in size or even larger than the extant great white shark and probably did not have an elongated dorsal tail, characteristic of modern relatives. Ground sharks (Carcharhiniformes) The Cenozoic Hemipristis serra was considerably larger than its modern-day relatives and had much larger teeth. Its total length is estimated to be at long. Hybodonts (Hybodontiformes) One of the largest hybodontiforms was the Jurassic Asteracanthus with body length of up to . Crassodus reifi is known from less materials, however it is estimated that reached over . Ctenacanthiformes The largest member of ctenacanthiformes is Saivodus striatus with estimated length around . Eugeneodonts (Eugeneodontida) '' The largest known eugeneodont is an as-yet unnamed species of Helicoprion discovered in Idaho. The specimens suggest an animal that possibly exceeded in length. Another fairly large eugeneodont is Parahelicoprion. Being slimmer than Helicoprion, it reached nearly the same size, although these numbers originate from non-academic amateur researchers and are not supported by scientific literature. Lobe-finned fish (Sarcopterygii) Coelacanths (Actinistia) The largest coelacanth is Cretaceous Mawsonia gigas with estimated total length up to . Jurassic Trachymetopon may have reached size close to that, about . An undetermined mawsoniid from the Maastrichtian deposits of Morocco probably reached in length. Stem-tetrapods (Tetrapodomorpha) '' '' • Not only the largest known rhizodont, but also the largest lobe-finned fish was the long Rhizodus. • Tristichopterid Hyneria reached length up to . • The largest known fossil sturgeon is "Acipenser" gigantissimus known from fragmentary remains, which is estimated to reach up to . • The largest known fossil paddlefish is unnamed remain from Judith River Formation, it may exceeded , known remains exceeded size of recently extinct Chinese paddlefish, which scientifically reported to exceed . Amiiformes The largest bowfins Melvius length of over , and there is even larger abdominal centra which is wide. Maliamia Estimates put the body length of M. gigas between 1.8 (based on Calamopleurus) and 3.5 meters (based on Amia), making it the largest known member of Vidalamiinae. Pachycormiformes fish The largest known ray-finned fish and largest bony fish of all time was the pachycormid, Leedsichthys problematicus, at around long. Earlier estimates have had claims of larger individuals with lengths over . Ichthyodectiformes (1), Ichthyodectes (2), Cladocyclus (3), Chirocentrites'' (4) The largest known of ichthyodectiform fish was Xiphactinus, which measured up to long. Ichthyodectes reached long, twice lesser than Xiphactinus. Pycnodontiformes The largest known pycnodontiform was Gyrodus circularis, with length up to . Bichirs (Polypteriformes) The Late Cretaceous Bawitius was likely the largest bichir of all time. It reached up to in length. Opahes, ribbonfishes, oarfishes and allies (Lampriformes) Megalampris was likely the largest fossil opah. This fish was around in length when alive, which is twice the length of the largest living opah species, Lampris guttatus. Salmon and trout (Salmoniformes) The largest salmon was Oncorhynchus rastrosus, varying in size from and to and . • Some extinct species of Balistes like B. vegai and B. crassidens are estimated to have total length up to . Lizardfishes (Aulopiformes) The largest lizardfish was Stratodus which could reach length of . == Echinoderms (Echinodermata) ==

Crinozoa '' Sea lilies (Crinoidea) The longest stem of Seirocrinus subangularis reached over . Asterozoa Starfish (Asteroidea) Helianthaster from Hunsrück Slate had a radius of about . == Graptolites (Graptolithina) ==

The longest known graptoloid graptolite is Stimulograptus halli at . It was found in Silurian deposits of the United Kingdom. == Kinorhynchs (Kinorhyncha) ==

Cambrian kinorhynchs from Qingjiang biota, also known as "mud dragons", reached in length, much larger than extant relatives that grow only a few millimeters in length. == Arthropods (Arthropoda) ==

Dinocaridida Gilled lobopodians ''. Based on the findings of mouthparts, the Cambrian gilled lobopodian Omnidens amplus is estimated to have been . Radiodont (Radiodonta) The largest known radiodont is Aegirocassis benmoulai, estimated to have been at least long. Chelicerata Sea spiders (Pycnogonida) The largest fossil sea spider is Palaeoisopus problematicus with legspan about . Horseshoe crabs and allies (Xiphosura) • Willwerathia reached in carapace width and was the largest species of basal ("synziphosurine") xiphosurans. However, the Devonian Maldybulakia reached nearly and was assigned to xiphosurans in 2013. Chasmataspidids (Chasmataspidida) The largest chasmataspidids were the Ordovician Hoplitaspis at in length and similar in size range Chasmataspis. Eurypterids (Eurypterida) s • The largest known eurypterid was Jaekelopterus rhenaniae at in length, which is also the largest arthropod known to exist. Erettopterus grandis possibly reached this same length but this is based on an incomplete telson only. A close contender was Acutiramus bohemicus at in length. The largest megalograptid as well as the largest Ordovician eurypterid was Pentecopterus. It reached up to in length. All these were eurypterine eurypterids. and up to , respectively. • Mongolarachne jurassica is the largest described fossil spider, with the total body length of female is approximately while the front legs reach about in length. Dinodiplura ambulacra had larger body length, combined length of carapace and opisthosoma reaches . • The largest of prehistoric whipscorpions and possibly the largest-known whipscorpion ever discovered was Mesoproctus rayoli. The type specimen has body length reaching with a carapace of in length, while another specimen has a carapace of in length and in width, comparable or even larger than the extant Mastigoproctus. • The largest Ricinulei to ever exist was Curculioides bohemondi with a body length of . • The largest fossil acariform mite and also the largest erythraeoid mite ever recorded was Immensmaris chewbaccei with idiosoma of more than in length. • The largest known trigonotarbid was Kreischeria with a minimal length of . The second largest was Pleophrynus at in length. Tegopelte is another one example of large non-trilobite artiopod, reached long Trilobites (Trilobita) Some of trilobites exceeded in length. A nearly complete specimen of Isotelus rex from Manitoba attained a length over , and an Ogyginus forteyi from Portugal was almost as long. Fragments of trilobites suggest even larger record sizes. An isolated pygidium of Hungioides bohemicus implies that the full animal was long. Myriapods (Myriapoda) '' The largest known myriapod by far was Arthropleura. Measuring long and wide. Some specimens could have been even larger, up to in length and in weight. Non-hexapod crustaceans (Crustacea) Cycloids (Cyclida) The largest cyclid was Opolanka decorosa, the Late Triassic Halicyne-like cycloid which reached over across the carapace. Remipedes (Remipedia) Tesnusocaris had body length at least , larger than all living remipedes which can reach up to . Insects (Insecta) Sawflies, wasps, bees, ants and allies (Hymenoptera) '' with rufous hummingbird for scale • The largest known of this group was the giant ant Titanomyrma giganteum with queens growing to . It had a wingspan of . • Apis lithohermaea is one of the largest honey bees ever found, comparable in size to the modern Apis dorsata. • The giant horntail Ypresiosirex orthosemos reached in length including the incomplete ovipositor. Another example of a giant sawfly is Hoplitolyda duolunica, with wingspan over . Fleas (Siphonaptera) The largest known in Siphonaptera was probably Pseudopulex magnus, growing to in length. Earwigs (Dermaptera) '' (St. Helena earwig) specimen Extinct as recently as after 1967 and also submitted as the Holocene subfossils, the Saint Helena giant earwig (Labidura herculeana, with synonym Labidura loveridgei) reached in length including forceps long. Beetles (Coleoptera) One of the largest known fossil beetles in the superfamily Scarabaeoidea is Protognathinus spielbergi. It had total length including mandibles about . The largest fossil scarabaeid was Oryctoantiquus borealis with an estimated body length of . Titanopterans (Titanoptera) '' Related to modern orthopterans, titanopterans from the Triassic period were much larger. The wingspan of Gigatitan vulgaris was up to . Clatrotitan andersoni also reached a huge size, having a forewing long. Antlions and related net-winged insects (Neuroptera) Makarkinia adamsi from the Crato Formation is estimated to have the longest forewings of any neuropteran species, estimated at . Cockroaches, termites, mantises and allies (Dictyoptera) • The largest known roachoid, cockroach-like stem dictyopteran, is Opsiomylacris sp., with wing length of , which is comparable to a modern Megaloblatta longipennis. • Cretaceous cockroach Ptiloteuthis foliatus had a long wing. • Found in the Miocene of Austria, the giant termite Gyatermes styriensis reached in body length and had a wingspan of . Dragonflies, damselflies and griffinflies (Odonatoptera) '' • The largest known odonatopteran insect was Meganeuropsis permiana with a single wing of . Meganeura had a long wing. • Triadotypid odonatan Reisia gelasii (=Triadotypus guillaumei) from Triassic had long wing, and wingspan can be . Mayflies (Ephemeroptera) • The largest known mayfly is Permian Ponalex maximus, with long hindwing. Cretaceous Epicharmeropsis quadrivenulosus had long forewing. • Although Bojophlebia prokopi from the Upper Carboniferous of Moravia (Czech Republic) with a wingspan of is described as the largest mayfly, later study shows that this insect is not related to mayflies. Palaeodictyoptera The largest known palaeodictyopteran was Mazothairos, with an estimated wingspan of up to . If a subcircular wing known from Piesberg Quarry belongs to a palaeodictyopteran, it possibly had single wing length at least . Archaeognatha (jumping bristletails) and other wingless primitive insects • The largest known machilid is Triassic Gigamachilis, with body length not counting the length of the filament, and estimated total length about . • The largest specimens of the extinct suborder Monura reached or more, not counting the length of the filament. • Although Ramsdelepidion was once considered as a -long silverfish, it was later considered that classification is uncertain and just treated as stem group insect. • The wingless early insect Carbotriplura had body length about without tail filaments. ==Arrow worms (Chaetognatha)==

The Cambrian stem-chaetognathan Timorebestia koprii had reached up to in body length and including the antennae. Capinatator had a third of length, about , but it is not considered as stem member and still had length similar to the largest modern arrow worms. == Ringed worms (Annelida) ==

Websteroprion is the largest known fossil eunicidan annelid, with estimated length ranges , however comparison with closely related extant taxa indicates length around .{{Cite journal |last1=Eriksson |first1=Mats E. |last2=Parry |first2=Luke A. |last3=Rudkin |first3=David M. |date=February 2017 |title=Earth's oldest "Bobbit worm" – gigantism in a Devonian eunicidan polychaete == Molluscs (Mollusca) ==

Snails and slugs (Gastropoda) '' shell • The largest known gastropods were in the genus Campanile, with the extinct Campanile giganteum having shell lengths up to or even more than . • The largest known cowrie is Vicetia bizzottoi, with shell length of . • Pebasiconcha immanis is the largest land snail ever known, shell height is with a partial specimen that may exceed in height. Bivalves (Bivalvia) • The largest known bivalve ever as well as the largest inoceramid was Platyceramus platinus, a giant that usually had an axial length of , but some individuals could reach an axial length of up to . Another large prehistoric bivalve was Inoceramus. In 1952, -long specimen of Inoceramus steenstrupi was found in the Late Cretaceous deposits of Greenland. • Some Permian alatoconchid genus like Shikamaia had shell length about . Previous estimation reconstructed length of Shikamaia around . • The longest ostreid is Konbostrea, with shell height reaching up to . • Rudist Titanosarcolites had overall size around . Cephalopods (Cephalopoda) '' shell Nautiloids (Nautiloidea) The largest and longest known of nautiloids was Endoceras giganteum with a shell length of . There is a record of an individual whose shell length had reached , but it is doubtful. Ammonites (Ammonoidea) The largest known ammonite was Parapuzosia seppenradensis. A partial fossil specimen found in Germany had a shell diameter of , but the living chamber was incomplete, so the estimated shell diameter was probably about and weighed about when it was alive. However, a later study estimates shell diameter up to around . Belemnites (Belemnoidea) The largest known belemnite was Megateuthis gigantea, reaching about in maximum diameter and length of rostrum, respectively. Squids, octopuses, cuttlefishes and allies (Neocoleoidea) • In 2026, the finned octopus Nanaimoteuthis haggarti was estimated to be between 7 and 19 m long, making it possibly the largest animal in the Late Cretaceous oceans and the largest known invertebrate. • A specimen of Octopod, a member of family Muensterellidae and Enchoteuthinae, Enchoteuthis melanae (NDGS 241) which was previously attributed to Tusoteuthis longa (another more dubious member), had a mantle length of up to , comparable to the modern-day giant squid. Previously, this taxon was considered similar to the giant squid, with total length including arms over . However, considering other fossil relatives, the total length including arms is estimated to be less than , to be realistic and reasonable. • Both non-octopod Yezoteuthis and teuthid Haboroteuthis are estimated to be similar in size to the modern-day giant squid. Incomplete jaw specimen from Yezo Group (KMNH IvP 902007) is twice as large as those of Yezotuethis. == Brachiopods (Brachiopoda) ==

'' The largest brachiopod ever evolved was Striatifera striata from Akkermanovka Quarry, Russia, with height up to . Another huge brachiopod was the Carboniferous Gigantoproductus giganteus, with shell width from to over . Titanaria costellata had large and long shell in width, nearly as large as Gigantoproductus. == Hyoliths (Hyolitha) ==

The largest hyolith is Macrotheca almgreeni, with length about . == Cnidarians (Cnidaria) ==

Jellyfishes and allies (Medusozoa) The largest fossil jellyfish is Cambrian Cordubia gigantea, with diameter of . Specimens from the Cambrian of Wisconsin reached in length. == Vendobionts (Vendobionta) ==

Petalonamids (Petalonamae) '' Longest specimens of Trepassia wardae (also known as Charnia wardi) reached in length. Charnia masoni is known from specimens as small as only , up to the largest specimens of in length. Proarticulata Dickinsonia tenuis reached in length, that makes it one of the largest precambrian organisms. == Sponges (Porifera) ==

The largest known Permian sponge Gigantospongia had diameter up to . == See also ==