Largest prehistoric animals

The largest prehistoric animals include both vertebrate and invertebrate species. Many of them are described below, along with their typical range of size (for the general dates of extinction, see the link to each). Many species mentioned might not actually be the largest representative of their clade due to the incompleteness of the fossil record and many of the sizes given are merely estimates since no complete specimen have been found. Their body mass, especially, is largely conjecture because soft tissue was rarely fossilized. Generally the size of extinct species was subject to energetic and biomechanical constraints.

Non-mammalian synapsids (Synapsida)

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.

Sphenacodontids (Sphenacodontidae)

The biggest carnivorous synapsid of 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)

The plant-eating dicynodont '' Lisowicia bojani'' is the largest-known of all non-mammalian synapsids, at about long, tall, and in body mass.

Dinocephalians (Dinocephalia)

Among the largest carnivorous non-mammalian synapsids was the dinocephalian '' Anteosaurus'', which was long, and weighed . Fully grown ''Titanophoneus'' from the same family Anteosauridae likely had a skull of long. Another enormous dinocephalian was the Late Permian ''Eotitanosuchus'' (a possible synonym to ''Biarmosuchus''). Adult specimens could reach in length and over in weight.

Gorgonopsians (Gorgonopsia)

'' Inostrancevia latifrons'' is the largest known gorgonopsian, with a skull length of more than , a total length approaching and a mass of . '' 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, and '' Sycosaurus'' with skull of ~ long.

Therocephalians (Therocephalia)

The largest of therocephalians is '' Scymnosaurus'', which reached a size of the modern hyena.

Non-mammalian cynodonts (Cynodontia)

* The largest known non-mammalian cynodont 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 . With such parameters it surpassed in size several small theropod dinosaurs of the Early Cretaceous. '' Gobiconodon'' was also a large mammal, it weighed , had a skull of in length, and had in presacral body length.

Multituberculates (Multituberculata)

The largest multituberculate ''Taeniolabis taoensis'' is the largest non-therian mammal known, at a weight possibly exceeding .

Monotremes (Monotremata)

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* The largest known monotreme (egg-laying mammal) ever was the extinct long-beaked echidna species known as '' Murrayglossus'', 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'', it was even larger than -long ''Monotrematum sudamericanum''.
* '' Kollikodon'' was likely the largest monotreme in Mesozoic. Its body length could be up to a .

Metatherians (Metatheria)

* The largest non-marsupial metatherian was ''Thylacosmilus'', weigh , one estimate suggesting even . Proborhyaenid '' Proborhyaena gigantea'' is estimated to weigh over and possibly reached . '' Australohyaena'' is another large metatherian, weighing up to .A. M. Forasiepi, M. Judith Babot, and N. Zimicz. 2014. Australohyaena antiqua (Mammalia, Metatheria, Sparassodonta), a large predator from the Late Oligocene of Patagonia. Journal of Systematic Palaeontology 13(6):503-525 DOI: 10.1080/14772019.2014.926403
* Stagodontid mammal '' Didelphodon'' was one of the largest Mesozoic metatherians and all Cretaceous mammals. Its skull could reached over in length and a weight of complete animal was .

Marsupials (Marsupialia)

* 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 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 potoroid ever recorded was ''Borungaboodie'', which was nearly 30% bigger than the largest living species and weighted up to .

Non-placental eutherians

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 .

Leptictids (Leptictida)

The largest leptictid ever discovered is '' Leptictidium tobieni'' from the Middle Eocene of Germany. It had a skull long, head with trunk long, and tail long. Close European relatives from the same family Pseudorhyncocyonidae had skulls of in length.

Even-toed ungulates (Artiodactyla)

* The largest known land-dwelling artiodactyl was '' Hippopotamus gorgops'' with a length of , a height of , and a weight of .
* '' Daeodon'' and similar in size and morphology ''Paraentelodon''
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 skull long though the taxonomy of this genus is disputive.

* The largest of Bovinae as well as the largest bovid was '' Bison latifrons''. It reached a weight from to , in length, shoulder height of , and had horns that spanned . The North American ''Bison antiquus'' reached up to long, tall, weight of , and horn span of . The African ''Pelorovis'' reached in weight and had bony cores of the horns about long. Another enormous bovid, the african giant buffalo (''Syncerus antiquus'') reached 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 . Aside from local populations and subspecies of extant species, such as the gaur population in Sri Lanka, European bison in British Isles, Caucasian wisent and Carpathian wisent, the largest modern extinct bovid is aurochs (''Bos primigenius'') with an average height at the shoulders of in bulls and in cows, while aurochs populations in Hungary had bulls reaching . 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''.Oxworth Books. pp. 111, 126, 247–250. (1998) 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 camelid was '' Titanotylopus'' from the Miocene of North America. It possibly reached and a shoulder height of over . The Syrian camel ('' Camelus moreli'') was twice as big as the modern camels. It was at the shoulder and tall. ''Camelops'' had legs to be 20% longer than that of Dromedary, and was about tall at the shoulder and weighed about .

Cetaceans (Cetacea)

* The largest of known Eocene archeocete whales was ''Basilosaurus'' at in length.
* The largest prehistoric sperm whale, or toothed whale was '' Livyatan melvillei'' weighing in at about 57 tonnes (63 short tons).
* 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, though other studies disagree that any baleen whale grew that large in the Miocene.

Odd-toed ungulates (Perissodactyla)

* The largest known perissodactyl, and the second largest land mammal (see '' Palaeoloxodon namadicus'') of all time was the hornless rhino '' Paraceratherium''. The largest individual known 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 . Such parameters make it the largest rhino of the Quaternary. Woolly rhinoceros (''Coelodonta antiquitatis'') of the same time reached 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'') reached tall at the shoulders, 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.

Phenacodontids (Phenacodontidae)

The largest known phenacodontid is '' Phenacodus''. It was long and weighed up to .

Dinoceratans (Dinocerata)

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, in length and , the size of a rhinoceros. Despite their large size, ''Eobasileus'' as well as ''Uintatherium'' had a very small brain.

Carnivores (Carnivora)

Caniformia

* The largest terrestrial mammalian carnivore and the largest known bear, as well as the largest known mammalian land predator of all time, was ''Arctotherium angustidens'', the South American short-faced bear. A humerus of ''A. angustidens'' from Buenos Aires indicates that the males of the species could have weighed and stood at least tall on their hind-limbs. Another huge bear was the giant short-faced bear ('' Arctodus simus''), with the average weight of and the maximum recorded at . There is a guess that the largest individuals of this species could reached even larger mass, up to . The extinct cave bear (''Ursus spelaeus'') was also heavier than many recent bears. Largest males weighed as much as . '' Ailuropoda baconi'' from the Pleistocene was larger than the modern giant panda (''Ailuropoda melanoleuca'').
* The biggest odobenid and one of the biggest pinnipeds to have ever existed is ''Pontolis magnus'', with skull length of (twice as large as the skulls of modern male walruses) and more than in total body length. Only the modern males of elephant seals ('' Mirounga'') reaches the similar sizes.
The second largest prehistoric pinniped is '' Gomphotaria pugnax'' with the 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''. 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). Similar in size to the jaguar, ''Megalictis ferox'' had even wider skull, almost as wide as of the black bear. ''Megalictis'' had a powerful bite force, allowing it to eat large prey and crush bones, as modern hyenas and jaguars can. Another large-bodied mustelid was the superficially cat-like '' Ekorus'' from the Miocene of Africa. At almost , the long-legged ''Ekorus'' was about the size of a wolf and filling a similar to leopards ecological niche before big cats came to the continent. Other huge mustelids include '' Perunium'' and hypercarnivorous ''Eomellivora'', both from the Late Miocene.
* The heaviest procyonid was possibly 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 extinct dire wolf (''Aenocyon dirus'') reached in length and weighed between . 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 bear-dog was a species of '' Pseudocyon'' weighing around , representing a very large individual.

Feliformia

* The largest nimravid was probably '' Quercylurus major'' as its fossils suggest it was similar in size to the modern-day brown bear and was scansorial. In 2021, '' Eusmilus'' was declared as the largest of the holplophonine nimravids, reaching the weight of nearly , comparable to a small African lion. However, the largest '' Hoplophoneus'' was estimated at .
* The biggest saber-toothed cats are '' Amphimachairodus kabir'' and '' Smilodon populator'', with the males possibly reaching and respectively. Another contender for the largest felid of all time is '' Machairodus''. ''M. horribilis'' from China was estimated at while the North American ''M. lahayishupup'' weighed up to . ''Xenosmilus'' was also a huge cat. It reached around long and weighed around .
* The heaviest known pantherine felids are the Ngangdong tiger (''Panthera tigris soloensis''), which are estimated to have weighed up to , the American lion (''Panthera atrox''), weighing up to Merriam, J. C. & Stock, C. 1932: The Felidae of Rancho La Brea. Carnegie Institution of Washington Publications 442, 1–231. and the Eurasian cave lion (''Panthera spelaea''), weighing up to . Being the ancestor of the modern jaguar, '' Panthera gombaszoegensis'' was much larger, up to in maximum weight.
* Some extinct feline felids also surpassed their modern relatives in size. The Eurasian 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 barbourofelid was ''Barbourofelis fricki'', with the shoulder height of .
* 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 fossil hyena is ''Pachycrocuta'', estimated at at the shoulder and weight. Another huge hyena with mass over is the cave hyena. It is actually a subspecies of the African spotted hyena, which is at 10% smaller than the extinct cave hyena.
* The percrocutid feliform, '' Dinocrocuta'', was two or even three times as large as the extant spotted hyena, .
* 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 hyaenodont was ''Simbakubwa'' at . Another giant hyaenodont, '' Megistotherium'' reached and had a skull of in length.

Oxyaenids (Oxyaenidae)

The largest known oxyaenid was ''Sarkastodon'' weighing in at .

Mesonychians (Mesonychia)

Some mesonychians reached a size of a bear. Such large were '' Mongolonyx'' from Asia and ''Ankalagon'' from North America. Another large mesonychian is '' Harpagolestes'' with a skull length of a half a meter in some species.

Bats (Chiroptera)

Found in Quaternary deposits of South and Central Americas, ''Desmodus draculae'' had a wingspan of and a body mass of up to . Such proportions make it the largest vampire bat that ever evolved.

Hedgehogs, gymnures, shrews, and moles (Eulipotyphla)

The largest known animal of the group Eulipotyphla was '' Deinogalerix'', measuring up to in total length, with a skull up to long.

Rodents (Rodentia)

* Several of the extinct South American dinomyids were much bigger than the modern rodents. ''Josephoartigasia monesi'' was the largest-known rodent of all time, approximately weighing an estimated . ''Phoberomys pattersoni'' weighed . Both ''Josephoartigasia'' and ''Phoberomys'' reached about tall at the shoulder. Another huge dinomyid, ''Telicomys, Telicomys gigantissimus'' had a minimal weight of .
* ''Amblyrhiza inundata'' from the family Heptaxodontidae was a massive animal, it weighed .
* The largest beaver was the Castoroides, giant beaver (''Castoroides'') of North America. It grew over 2 m in length and weighed roughly , also making it one of the largest rodents to ever exist.

Rabbits, hares, and pikas (Lagomorpha)

The biggest known prehistoric lagomorph is Menorca, Minorcan giant lagomorph ''Nuralagus rex'' at .

Primates (Primates)

* The largest known primate as well as the largest Hominidae, hominid of all time was ''Gigantopithecus blackii'', standing tall and weighing . However In 2017, new studies suggested a body mass of for this primate. Another giant hominid 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. Some ''Homo erectus'' could be as large as tall and in weight.
* The largest known Old World monkey is the prehistoric baboon, with a male specimen of ''Dinopithecus'' projected to weigh an average of and up to . It exceeds the maximum weight record of the chacma baboon, the largest extant baboon. One source projects a specimen of ''Theropithecus oswaldi'' to have weighed .
* The largest known New World monkey was ''Cartelles'', which is studied as specimen of ''Protopithecus'', weighing up to . ''Caipora bambuiorum'' is another large species, weighing up to .
* The largest Omomyidae, omomyids were ''Macrotarsius'' and ''Ourayia'' from the Middle Eocene. Both reached in weight.
* Some prehistoric Lemuriformes, 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 .Crowley, B.E., & Godfrey, L.R. (2019).
Strontium Isotopes Support Small Home Ranges for Extinct Lemurs
. Frontiers in Ecology and Evolution, 7, 490. doi: 10.1002/ajp.20817 ''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.

Elephants, mammoths, and mastodons (Proboscidea)

* The largest known land mammal ever was a proboscidean called '' Palaeoloxodon namadicus'' which weighed about and measured about tall at the shoulder. The largest individuals of the steppe mammoth of Eurasia (''Mammuthus trogontherii'') estimated to reach at the shoulders and in weight. ''Stegodon zdanskyi'', the biggest species of ''Stegodon'', was in body mass. Another one enormous proboscidean is ''Stegotetrabelodon, Stegotetrabelodon syrticus'', over in height and in weight. The Columbian mammoth (''Mammuthus columbi'') was about tall at the shoulder but didn't weigh as much as other huge mammoths. Its average mass was with one unusually large specimen about . Columbian mammoths had very long tusks. The largest known mammoth tusk, long, belonged to this species.
* The largest Mammutidae, mammutid was the Neogene ''Mammut borsoni''. The biggest specimen reached tall and weighed about . This species also had the longest tusks, long from basis to tip along the curve.
* ''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.

Sea cows (Sirenia)

According to reports, Steller's sea cows have grown to long as adults, much larger than any extant species, extant sirenians. The weight of Steller's sea cows is estimated to be .

Arsinoitheres (Arsinoitheriidae)

The largest known Arsinoitheriidae, arsinoitheriid was ''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, 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)

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 .

Armadillos, glyptodonts and pampatheres (Cingulata)

The largest Cingulata, cingulate known is ''Doedicurus'', at long, high and reaching a mass of approximately . The largest species of ''Glyptodon'', ''Glyptodon clavipes'', reached in length and in weight.

Anteaters and sloths (Pilosa)

The largest known pilosan ever was ''Megatherium'', a ground sloth with an estimated average weight of and a height of which is almost as big as the African bush elephant. Several other sloths grew to large sizes as well, such as ''Eremotherium'', but none as large as ''Megatherium''.

Astrapotherians (Astrapotheria)

Some of the largest known astrapotherians weighed about , including the genus ''Granastrapotherium'' and some species of ''Parastrapotherium'' (''P. martiale''). The skeleton remains suggests that the species ''Hilarcotherium, Hilarcotherium miyou'' was even larger, with a weight of .

Litopterns (Litopterna)

The largest known Litopterna, litoptern was ''Macrauchenia'', which had three hoofs per foot. It was a relatively large animal, with a body length of around .

Notoungulates (Notoungulata)

The largest Notoungulata, 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 is not complete, the preserved fossils suggests 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)

* Giant mosasaurs are the largest-known animals within the Squamata. The largest-known mosasaur is likely ''Mosasaurus, 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 large mosasaur is ''Hainosaurus, Hainosaurus bernardi'' (could be synonymous to ''Tylosaurus''). It was once estimated at in length, but later estimates put it at around .
* The largest known prehistoric snake is ''Titanoboa, Titanoboa cerrejonensis'', estimated at in length and in weight. Another known very large fossil snake is ''Gigantophis, Gigantophis garstini'', estimated at in length, although later study shows smaller estimation about . A close rival in size to ''Gigantophis'' is a fossil snake, ''Palaeophis, Palaeophis colossaeus'', which may have been around in length. Later studies speculate that it reached a maximum length of . The largest fossil Pythonidae, python is ''Liasis dubudingala'' with length roughly . The largest viper as well as the largest venomous snake ever recorded is ''Laophis, 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 Scolecophidia, blind snake is ''Boipeba tayasuensis'' with estimated total length of .
* The largest known land lizard is probably megalania (''Varanus priscus'') at in length. As extant relatives, megalania could have been venomous and in that case this lizard was also the largest venomous vertebrate ever evolved. However, maximum size of this animal is subject to debate.

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, 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. The Cenozoic ''Titanochelon'' were also larger than extant giant tortoises, with a shell length of up to . Other giant tortoises include ''Centrochelys, Centrochelys marocana'' at in carapace length and Mesoamerican ''Hesperotestudo sp.'' at in carapace length.
* The largest trionychidae, trionychid ever recorded is indeterminate specimen GSP-UM 3019 from the Middle Eocene of Pakistan. Bony carapace of GSP-UM 3019 is long and wide indicates the total carapace diameter (with soft margin) about . ''Drazinderetes, Drazinderetes tethyensis'' from the same formation had a bony carapace long and wide. Another huge trionychid is North American ''Axestemys, Axestemys byssinus'' at over in total length.

Side-necked turtles (Pleurodira)

The largest freshwater turtle of all time was the Miocene Podocnemididae, 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 Macrobaenidae, macrobaenids were the Early Cretaceous ''Yakemys'', Late Cretaceous ''Anatolemys'', and Paleocene ''Judithemys''. All reached in carapace length.

Meiolaniformes

The largest Meiolaniidae, 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. ''Ninjemys, Ninjemys oweni'' reached in carapace length and in weight.

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 Plesiosauroidea, plesiosauroid was ''Aristonectes'', with a body length of and body mass of or even . 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. In past, ''Mauisaurus'' was considered to be more than in length, but later it was determined as ''nomen dubium''.

* There is much controversy over the largest-known of the Pliosauroidea. ''Pliosaurus, Pliosaurus funkei'', fossil remains of a pliosaur nicknamed as "Predator X" have been discovered and excavated from 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. Another very large pliosaur was ''Pliosaurus, Pliosaurus macromerus'', known from a single incomplete mandible. The Early Cretaceous ''Kronosaurus queenslandicus'' is estimated at in length and in weight. The Late Jurassic ''Megalneusaurus rex'' could reach lengths of . Close contender in size was the Late Cretaceous ''Megacephalosaurus eulerti'' with a length in range of .

Proterosuchids (Proterosuchidae)

''Proterosuchus fergusi'' is the largest known Proterosuchidae, proterosuchid with a skull length of and a possible body length of .

Erythrosuchids (Erythrosuchidae)

The largest Erythrosuchidae, erythrosuchid was ''Erythrosuchus africanus'' with a maximum length of .

Phytosaurs (Phytosauria)

Some of the largest known Phytosauria, phytosaurs include ''Redondasaurus'' with a length of and ''Smilosuchus'' with a length of more than .

Non-crocodylomorph pseudosuchians (Pseudosuchia)

* The largest Shuvosauridae, 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, 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)

Aegyptosuchids (Aegyptosuchidae)

The Late Cretaceous ''Aegisuchus'' is the main contender for the title of the largest Crocodylomorpha, crocodylomorph ever recorded. It reached in length by the lower estimate and as much as by the upper estimate, although a length of over 15 m is likely an overestimate.

Crocodylians (Crocodylia)

* The largest caiman and likely the largest crocodylian was ''Purussaurus, Purussaurus brasiliensis'' estimated at . According to another information, maximum estimate measure and almost in length and in weight respectively. Another giant caiman was ''Mourasuchus''. Various estimates suggest the biggest specimens reached in length and in weight or in body length.
* The largest Alligatoroidea, alligatoroid is likely ''Deinosuchus, Deinosuchus riograndensis'' at long and weighing .
* 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 Gavialidae, gavialids were Asian ''Rhamphosuchus'' at and South American ''Gryposuchus'' at in length.
* The basal crocodyloidean ''Astorgosuchus bugtiensis'' from the Oligocene was large. It estimated at in length.
* The largest known Crocodylidae, true crocodile was ''Euthecodon'' which estimated to have reached or even long. The largest species of the modern ''Crocodylus'' were Kenyan ''Crocodylus thorbjarnarsoni'' at in length, Tanzanian ''Crocodylus anthropophagus'' at in length and indeterminate species from Kali Gedeh (Java) at in length.
* Unnamed Pliocene species of ''Quinkana'' known from partial remains may have reached up to in length, although other species (known from Oligocene to Pleistocene) are smaller with length just about . It is not only the largest Mekosuchinae, mekosuchian (some studies reject it from this group) but also it could have been Australia's largest Pliocene predator. ''Paludirex'' is another large mekosuchian with length over .

Paralligatorids (Paralligatoridae)

The largest Paralligatoridae, paralligatorid was likely ''Kansajsuchus'' estimated at up to long.

Tethysuchians (Tethysuchia)

* Some extinct Pholidosauridae, pholidosaurids reached giant sizes. In the past, the ''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 (genus), Chalawan thailandicus'' could reached more than in length, although other estimates suggest .
* The largest Dyrosauridae, dyrosaurid was ''Phosphatosaurus gavialoides'' estimated at in length.

Stomatosuchids (Stomatosuchidae)

''Stomatosuchus'', a Stomatosuchidae, stomatosuchid, estimated at in length.

Notosuchians (Notosuchia)

* The largest terrestrial notosuchian crocodylomorph was very likely the Miocene Sebecidae, sebecid ''Barinasuchus'', with a skull of long, comparable in size to the -long skull of ''Daspletosaurus''. Various estimates suggest a possible length of ''Barinasuchus'' at .
* Other huge notosuchians are Brazilian ''Stratiotosuchus'' at long, and ''Baurusuchus'' at long, both from the family Baurusuchidae.

Thalattosuchians (Thalattosuchia)

* The largest thalattosuchian as well as the largest Teleosauroidea, teleosauroid was the Early Cretaceous ''Machimosaurus rex'' estimated at in length. ''Neosteneosaurus edwardsi'' (previously known as ''Steneosaurus edwardsi'') was the biggest Middle Jurassic crocodylomorph, it reached long.
* ''Plesiosuchus'' was very large Metriorhynchidae, metriorhynchid. With the length of it exseeded even some pliosaurids of the same time and locality such as ''Liopleurodon''. Other huge metriorhynchids include ''Tyrannoneustes'' at in length and ''Torvoneustes'' at in length.

Basal crocodylomorphs

''Redondavenator'' was the largest Triassic crocodylomorph ever recorded,Lindsay E. Zanno, Susan Drymala, Sterling J. Nesbitt, Vincent P. Schneider (2015
Early crocodylomorph increases top tier predator diversity during rise of dinosaurs
Scientific Reports volume 5, Article number: 9276 with a skull of at least in length. Another huge basal crocodylomorph was ''Carnufex'' at long even through that is immature.

Pterosaurs (Pterosauria)

* 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. This estimate is based on a skull long. Yet another possible contender for the title is ''Cryodrakon'' which had a wingspan. An unnamed Pterodactyloidea, pterodactyloid pterosaur from the Nemegt Formation could reach a wingspan of nearly . 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-Pterodactyloidea, pterodactyloid pterosaurs as well as the largest Jurassic pterosaur was ''Dearc'', with an estimated wingspan between and . Only a fragmentary Rhamphorhynchidae, 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 , , and , respectively.

Choristoderes (Choristodera)

The largest known choristoderan, ''Kosmodraco, Kosmodraco dakotensis'' (previously known as ''Simoedosaurus dakotensis'') is estimated to have had a total length of around .

Tanystropheids (Tanystropheidae)

''Tanystropheus'', the largest of all Tanystropheidae, tanystropheids, reached up to in length.

Thalattosaurs (Thalattosauria)

The largest species of Thalattosauria, thalattosaur, ''Miodentosaurus, Miodentosaurus brevis'' grew to more than in length. The second largest member of this group is ''Concavispina'' with a length of .

Ichthyosaurs (Ichthyosauria)

The largest known ichthyosaur and the largest marine reptile was the Late Triassic ''Shastasaurus sikanniensis'' at in length and in weight. In April 2018, paleontologists announced the discovery of a previously unknown ichthyosaur that may have reached lengths of making it one of the largest animals known, rivaling some blue whales in size. Another, larger ichthyosaur was found in 1850 in Aust. Its remains seemed to surpass the measurements of the other ichthyosaur, but the researchers commented that the remains were too fragmentary for a size estimate to be made. Another huge ichthyosaur was ''Shonisaurus popularis'' at in length and in weight. The largest Middle Triassic ichthyosaur as well as the largest animal of that time was ''Cymbospondylus youngorum'' at in length and in weight.

Tangasaurids (Tangasauridae)

The largest Tangasauridae, tangasaurid was ''Hovasaurus'' with an estimated snout-vent length of and a tail of .

Pareiasaurs (Pareiasauria)

Largest Pareiasauridae, 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. The most robust ''Scutosaurus'' had in body mass.

Captorhinids (Captorhinidae)

The heavy built ''Moradisaurus, Moradisaurus grandis'', with a length of , is the largest known Captorhinidae, 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 Sauropodomorpha, sauropodomorphs ("prosauropod") was ''Euskelosaurus''. It reached in length and in weight. Another huge sauropodomorph ''Yunnanosaurus youngi'' reached long.

Sauropods (Sauropoda)

* A mega-sauropoda, sauropod, ''Maraapunisaurus, 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. More recently, it was estimated at in length and in weight.
* 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. More accurate estimation suggests and but it still much heavier than most other sauropods.
* BYU 9024, a massive cervical vertebra found in Utah, may belong to ''Barosaurus, Barosaurus lentus'' or ''Supersaurus, Supersaurus vivianae'' of a huge size, possibly in length and in body mass. ''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 Mamenchisauridae, mamenchisaurid, reaching nearly in length and in weight. ''Xinjiangtitan shanshanesis'' from the same family had -long neck, about 55% of its total length that could be at least .
* The Middle Jurassic ''Breviparopus, Breviparopus taghbaloutensis'' was mentioned in ''The Guinness Book of Records'' as the longest dinosaur at although this animal is known only from fossil tracks. Originally thought to be a brachiosauridae, brachiosaurid, it was later identified as a huge Diplodocoidea, diplodocoid, possibly in length and in weight.

* The tallest sauropod was ''Sauroposeidon proteles'' with estimated height at . ''Asiatosaurus'' could 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 .Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press. ''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. ''Dreadnoughtus'' was estimated at in weight and in length but the most complete individual was immature when it died. ''Turiasaurus'' is considered of being the largest dinosaur from Europe, with an estimated length of and a weight of . However, with lower estimate at and it was smaller than Portuguese ''Lusotitan'' that reached in length and in weight.

Many large sauropods are still unnamed and may rival the current record holders:
* The "List of informally named dinosaurs#Archbishop, Archbishop", a large brachiosaur that was discovered in 1930. The animal was reported to get a scientific paper published by the end of 2016.
* ''Brachiosaurus nougaredi'' is yet another large brachiosaur from Early Cretaceous North Africa. The remains have been lost, but the sacrum drawing remains. They suggest 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)

* The largest Theropoda, theropod as well as the largest terrestrial (or possibly semi-aquatic) predator yet known is ''Spinosaurus, Spinosaurus aegyptiacus'', with the largest specimen known estimated at in length and around in weight. New estimates published in 2014 and 2018, based on a more complete specimen supported that ''Spinosaurus'' could reach lengths of .Supplementary Information
/ref>Molina-Pérez & Larramendi 2016. ''Récords y curiosidades de los dinosaurios Terópodos y otros dinosauromorfos'', Larousse. Barcelona, Spain p. 259 The latest estimates suggest a weight of . The List of informally named dinosaurs#White Rock spinosaurid, White Rock spinosaurid had vertebrae comparable in dimensions to ''Spinosaurus'', it was likely a huge theropod with a length over .
* Other large theropods were ''Giganotosaurus carolinii'', and ''Tyrannosaurus rex'', whose largest specimens known estimated at and in length, and weigh between and to over , respectively. 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 egg fossil, dinosaur egg. It is assigned to Oviraptorosauria, oviraptorosaurs like ''Beibeilong''.

Armoured dinosaurs (Thyreophora)

The largest-known thyreophoran was ''Ankylosaurus'' at in length and in weight.Vickaryous, M.K., Teresa Maryańska, Maryanska, T., & Weishampel, D.B. 2004. Ankylosauria. In: Weishampel, D.B., Dodson, P., & Osmólska, H. (Eds.). ''The Dinosauria'' (2nd edition). Berkeley: University of California Press. Pp. 363–392. ''Stegosaurus'' was also long but around tonnes in weight.

Pachycephalosaurs (Pachycephalosauria)

The largest pachycephalosaur was the nominate ''Pachycephalosaurus''. Previously claimed to be at in length, it was later estimated about long and a weight of about .

Ceratopsians (Ceratopsia)

The largest ceratopsian known is ''Triceratops, Triceratops horridus'', along with the closely related ''Eotriceratops, 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.

Ornithopods (Ornithopoda)

* 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 . The Mongolian ''Saurolophus'', ''S. angustirostris'', reached long and possibly more.Paul, Greg (2010). "The Princeton Field Guide to Dinosaurs". New Jersey: Princeton University Press. p. 335. Such animal could weighed up to . The largest ''Edmontosaurus'' reached in length and around in body mass. An estimated maximum length of ''Brachylophosaurus'' is resulting in weight of . PASAC-1, informally named ''"List of informally named dinosaurs#Sabinosaurus, 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 Rhabdodontidae, rhabdodontid was ''Matheronodon'', estimated at in length. ''Rhabdodon'' reached approximately and according to 2016 estimates.

Birds (Aves)

The largest known birds of all time might have been the elephant birds of Madagascar. Both were about tall and in weight. Nearly the same size was the Australian ''Dromornis stirtoni'' (Largest prehistoric animals#Dromornithiformes, see below). The tallest bird ever was the giant moa at tall.

The widest known wingspan of any flight-capable bird was ''Pelagornis sandersi'' with a wingspan of , and a body weight of . The heaviest flight-capable bird was the giant teratorn, ''Argentavis magnificens'' which had a somewhat-smaller wingspan at around but was far heavier, with accepted maximums around .

Enantiornitheans (Enantiornithes)

One of the largest Enantiornithes, enantiornitheans was ''Enantiornis'', with a length in life of around , hip height of , weight 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 .

Avisauridae

The Late Cretaceous ''Avisaurus'' was almost as large as ''Enantiornis''. It had a wingspan around , a length of , hip height of , and weight of . Even larger could be the ''Soroavisaurus''. One tibiotarsus (PVL-4033) indicates an animal with a length of , hip height of , and weight of . ''Mirarce'' was comparable in size to a Turkey (bird), turkey, much larger than most of other enantiornitheans.

Pengornithidae

One of the biggest Early Cretaceous enantiornithine bird was ''Pengornis'' at in length and skull length of .

Gargantuaviidae

''Gargantuavis'' is the largest known bird of the Mesozoic, a size ranging between the cassowary and the Common ostrich, 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.

Dromornithiformes

The largest Dromornithidae, dromornithid was ''Dromornis stirtoni'' over tall and in mass for males.

Gastornid (Gastornithiformes)

Large individuals of ''Gastornis'' (also known as ''Diatryma'') reaged 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 swan of ever evolved was the Pleistocene giant swan (''Cygnus falconeri''), it reached bill-to-tail length of about , weighed around and had a wingspan of about . The New Zealand swan (''Cygnus sumnerensis'') weighed up to , much more than related black swan at only . The giant ''Annakacygna, Annakacygna yoshiiensis'' from the Miocene of Japan was much bigger than the extant mute swan.

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.

Storks and allies (Ciconiiformes)

The largest known of Ciconiiformes was ''Leptoptilos robustus'', standing tall and weighing an estimated .

Cranes (Gruiformes)

A huge 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)

''Mancallinae, Miomancalla howardi'' was the largest charadriiform of all time, weighing approximately (?) more than the great auk with a height of approximately .

Hesperornithines (Hesperornithes)

The largest known of the Hesperornithes, hesperornithines was ''Canadaga arctica'' at long.

New World vultures (Cathartiformes)

One of the heaviest flying bird ever was ''Argentavis'' from the family Teratornithidae. The immense bird had a wingspan estimated up to and a weight up to . ''Argentavis'' humerus was only slightly shorter than an entire human arm. Another huge teratorn was ''Aiolornis'', it had a wingspan around . The Pleistocene ''Teratornis, Teratornis merriami'' reached and in wingspan.Kenneth E. Campbell, Jr, Eduardo P. Tonni.
Size and Locomotion in Teratorns (Aves: Teratornithidae)
. The Auk, Volume 100, Issue 2, April 1983, pp. 390–403, https://doi.org/10.1093/auk/100.2.390 Even with lower estimates, it was larger than the observed California condor (''Gymnogyps californianus'') of nowadays.

Seriemas and allies (Cariamiformes)

The largest known-ever Cariamiformes, Cariamiforme and largest Phorusrhacidae, 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. South American ''Phorusrhacos'' stood nearly tall, and probably weighed nearly , as much as a male ostrich. The largest North American phorusrhacid is ''Titanis'', which is about tall, as tall as a forest elephant.

Accipitriforms (Accipitriformes)

The largest known Accipitriformes, 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 (''Buteogallus urubitinga, B. urubitinga''). ''Buteogallus daggetti, B. daggetti'', also known as "walking eagle", was around 40% larger than the savanna hawk (''Buteogallus meridionalis, B. meridionalis''). Eyles's harrier (''Circus eylesi'') from the Pleistocene-Holocene of New Zealand was more than twice heavier than the extant ''Circus approximans, C. approximans''.

Moa (Dinornithiformes)

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,Largest flying animals/birds in The World/Universe AllTopTens.com
/ref> and weighed approximately half as much as a large elephant bird due to its comparatively slender frame.

Tinamous (Tinamiformes)

MPLK-03, a tinamou specimen that existed during the Late Pleistocene in Argentina, possibly belongs to the modern genus ''Eudromia'' and surpacces extant ''Eudromia elegans, E. elegans'' and ''Eudromia formosa, E. formosa'' in size by 2.2-8% and 6-14%, respectively.

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.Wood, Gerald ''The Guinness Book of Animal Facts and Feats'' (1983)

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)

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 .

Pheasants, turkeys, gamebirds and allies (Galliformes)

The largest known of the Galliformes was likely the giant malleefowl, which could reach in weight.

Songbirds (Passeriformes)

The largest known Passeriformes, songbird is the extinct giant grosbeak (''Chloridops regiskongi'') at long.

Cormorants and allies (Suliformes)

* 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 darter was ''Giganhinga'' with estimated weight about , earlier study even claims .
* The largest known Plotopteridae, plotopterid, penguin-like flightless bird was ''Copepteryx, 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 Piciformes, woodpecker is the possibly extinct imperial woodpecker (''Campephilus imperialis'') with a total length of about .

Parrots (Psittaciformes)

The largest known Psittaciformes, parrot is the extinct ''Heracles inexpectatus'' with a length of about 1 meter (3.3 feet).

Penguins (Sphenisciformes)

The largest known Sphenisciformes, penguin of all time was ''Palaeeudyptes klekowskii'' of Antarctica, its body length (tip of the bill to tip of the tail) is estimated about and body weight is estimated about . Another large penguin is ''Anthropornis nordenskjoeldi'' of New Zealand and Antarctica. Its body length is estimated and was in weight. There is also an estimate that one remain of ''Anthropornis'' can reach that body length of and in weight. Similar in size were the New Zealand giant penguin (''Pachydyptes pondeorsus'') with a height of and weighing possibly around and over, and ''Icadyptes salasi'' at tall.

Owls (Strigiformes)

The largest known Strigiformes, owl of all time was the Cuban ''Ornimegalonyx'' at tall probably exceeding .

Amphibians (Amphibia)

The largest known amphibian of all time was the long temnospondyli, temnospondyl ''Prionosuchus''.

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)

* ''Andrias matthewi'' was the largest lissamphibian ever known, with total length up to .
* ''Habrosaurus'' was the largest Sirenidae, 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 amphibian is ''Prionosuchus'', which grew to lengths of . Another huge temnospondyl was ''Mastodonsaurus, Mastodonsaurus giganteus'' at long. Unnamed species of temnospondyl from Lesotho is partial, but possible body length estimation is .

Fishes (Pisces)

Fishes are a paraphyletic group of non-tetrapod vertebrates.

Jawless fish (Agnatha)

Conodonts (Conodonta)

''Iowagnathus, 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, 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 (fish), Xylacanthus grandis'', an Ischnacanthiformes, 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)

The largest known placoderm was the giant predatory ''Dunkleosteus''. The largest and most well known species was ''D. terrelli'', which grew almost in length and in weight. Its filter feeding relative, ''Titanichthys'', may have rivaled it in size. ''Titanichthys'' reached a length of though in older paper it was estimated at .

Cartilaginous fish (Chondrichthyes)

Mackerel sharks (Lamniformes)

* Species in the extinct genus ''Otodus'' were huge. A giant shark, ''Megalodon, Otodus megalodon'' is by far the biggest Lamniformes, mackerel shark ever known. Most estimates of megalodon's size extrapolate from teeth, with maximum length estimates up to and average length estimates 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. Mature male megalodon may have had a body mass of , and mature females may have been , assuming that males could range in length from and females . Related to megalodon, ''Otodus angustidens'' and ''Otodus chubutensis, 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 Hybodontiformes, hybodontiforms was the Jurassic ''Asteracanthus'' with body length of up to . ''Crassodus, Crassodus reifi'' is known from less materials, however it is estimated that reached over .

Skates and allies (Rajiformes)

The giant Sclerorhynchidae, sclerorhynchid ''Onchopristis'' reached about in length.

Eugeneodont (Eugeneodontida)

The largest known Eugeneodontida, 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 more slimmer than ''Helicoprion'', it reached nearly the same size, possibly up to in length. Both had the largest sizes among the animals of Paleozoic era.

Lobe-finned fish (Sarcopterygii)

Coelacanths (Actinistia)

The largest coelacanth is Cretaceous ''Mawsonia (fish), Mawsonia gigas'' with estimated total length up to . Jurassic ''Trachymetopon'' may have reached size close to that, about . An undetermined Mawsoniidae, mawsoniid from the Maastrichtian deposits of Morocco probably reached in length.

Lungfish (Dipnoi)

Cretaceous ''Ceratodus'' sp. from Western Interior Seaway, Western Interior is estimated to had a length around .

Stem-tetrapods (Tetrapodomorpha)

* Not only the largest known Rhizodontida, rhizodont, but also the largest lobe-finned fish was the long ''Rhizodus''. Another large rhizodonts were ''Strepsodus'' with estimated length around and ''Barameda'' estimated at in length.
* Tristichopteridae, Tristichopterid ''Hyneria'' reached length up to .

Ray-finned fish (Actinopterygii)

Pachycormiformes

The largest known Actinopterygii, ray-finned fish and largest bony fish of all time was the pachycormid, ''Leedsichthys problematicus'', at around long.Liston, J., Newbrey, M., Challands, T., and Adams, C., 2013, "Growth, age and size of the Jurassic pachycormid ''Leedsichthys problematicus'' (Osteichthyes: Actinopterygii) in: Arratia, G., Schultze, H. and Wilson, M. (eds.) ''Mesozoic Fishes 5 – Global Diversity and Evolution''. Verlag Dr. Friedrich Pfeil, München, Germany, pp. 145–175 Earlier estimates have had claims of larger individuals with lengths over .

Ichthyodectiformes

The largest known of ichthyodectiform fish was ''Xiphactinus'', which measured up to long. ''Ichthyodectes'' reached long, twice lesser than ''Xiphactinus''.

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 .

Pufferfishes, boxfishes, triggerfishes, ocean sunfishes and allies (Tetraodontiformes)

* ''Austromola angerhoferi'' had total body length about , and total height , comparable with largest ocean sunfish.
* Some extinct species of ''Balistes'' like ''B. vegai'' and ''B. crassidens'' are estimated to have total length up to .

Lizardfishes (Aulopiformes)

The largest Aulopiformes, lizardfish was ''Stratodus'' which could reach length of .

Echinoderms (Echinodermata)

Crinozoa

Sea lilies (Cricoidea)

Longest stem of ''Seirocrinus, Seirocrinus subangularis'' reached over .

Asterozoa

Starfish (Asteroidea)

''Helianthaster'' from Hunsrück Slate had radius about .

Graptolites (Graptolithina)

The longest known graptoloid graptolite is ''Stimulograptus, Stimulograptus halli'' at . It found in Silurian deposits of the United Kingdom.

Kinorhynchs (Kinorhyncha)

Cambrian Kinorhyncha, 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, Omnidens amplus'' is estimated to have been . It is also known as the largest Cambrian animal known to exist.

Radiodont (Radiodonta)

The largest known Radiodonta, radiodont is ''Aegirocassis benmoulai'', estimated to have been at least long.

Chelicerata

Sea spiders (Pycnogonida)

The largest fossil sea spider is ''Palaeoisopus, Palaeoisopus problematicus'' with legspan about .

Horseshoe crabs and allies (Xiphosura)

* ''Willwerathia'' reached in carapace width and was the largest species of basal ("Synziphosurina, synziphosurine") xiphosurans. However, the Devonian ''Maldybulakia'' reached nearly and was assigned to xiphosurans in 2013.
* Horseshoe crab trackway Trace fossil, icnofossil ''Kouphichnium, Kouphichnium lithographicum'' from Cerin in Ain indicates length of animal .

Chasmataspidids (Chasmataspidida)

The largest Chasmataspidida, chasmataspidids were the Ordovician ''Hoplitaspis'' at in length and similar in size range ''Chasmataspis''.

Eurypterids (Eurypterida)

* The largest known Eurypterida, eurypterid was ''Jaekelopterus rhenaniae'' at in length, which is also the largest arthropod known to exist. ''Erettopterus, Erettopterus grandis'' possibly reached this same length but this is based on an incomplete telson only. A close contender was ''Acutiramus, Acutiramus bohemicus'' at in length. The largest Megalograptidae, megalograptid as well as the largest Ordovician eurypterid was ''Pentecopterus''. It reached up to in length. All these were Eurypterina, eurypterine eurypterids.
* The largest Stylonurina, stylonurine eurypterid was ''Hibbertopterus'', with in length.

Arachnids (Arachnida)

* There are three contenders for largest-known arachnid as well as the largest scorpions of all time: ''Pulmonoscorpius kirktonensis'', ''Brontoscorpio, Brontoscorpio anglicus'' and ''Praearcturus, Praearcturus gigas''. Each was estimated to have been , 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, 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''. An unnamed species ''M. sp.'' had a carapace of in length and in width, comparable or even larger than the extant ''Mastigoproctus'' have.
* The largest Ricinulei to ever exist was ''Curculioides, Curculioides bohemondi'' with a body length of .
* The largest fossil Acariformes, acariform mite and also the largest Erythraeoidea, erythraeoid mite ever recorded was ''Immensmaris, Immensmaris chewbaccei'' with idiosoma of more than in length.
* The largest known Trigonotarbida, trigonotarbid was ''Kreischeria'' with a minimal length of . The second largest was ''Pleophrynus'' at in length.

Artiopods (Artiopoda)

''Retifacies'' probably reached up to . ''Tegopelte'' is another one example of large non-trilobite artiopod, reached long and was the largest of the Burgess Shale bilaterians, surpassing all other benthic organisms by at least twice.

Trilobites (Trilobita)

Some of these extinct marine arthropods exceeded in length. A nearly complete specimen of ''Isotelus, Isotelus rex'' from Manitoba attained a length over , and an ''Ogyginus, Ogyginus forteyi'' from Portugal was almost as long. Fragments of trilobites suggest even larger record sizes. An isolated pygidium of ''Hungioides, Hungioides bohemicus'' implies that the full animal was long.

Myriapods (Myriapoda)

The largest known Myriapoda, 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 Cyclida, 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 every living Remipedia, remipedes which could reach up to .

Insects (Insecta)

Sawflies, wasps, bees, ants and allies (Hymenoptera)

* The largest known of this group was the giant ant ''Titanomyrma, Titanomyrma giganteum'' with Eusociality, 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, Ypresiosirex orthosemos'' reached in length including the incomplete ovipositor. Another example of giant sawfly is ''Hoplitolyda duolunica'', with wingspan over .

Fleas (Siphonaptera)

The largest known in Siphonaptera was probably ''Pseudopulex, Pseudopulex magnus'', growing to in length.

Earwigs (Dermaptera)

Extinct as recently as after 1967 and also submitted as the Holocene subfossils, the Saint Helena earwig, Saint Helena giant earwig (''Labidura herculeana'', with synonym ''Labidura loveridgei'') reached in length uncluding forceps long.

Chresmodidae

Chresmodidae had long specialized legs like of the modern Gerridae family. One of the Chresmodidae, ''Chresmoda, Chresmoda obscura'' could reached a size of about .

Beetles (Coleoptera)

One of the largest known fossil beetles in the taxonomic rank, superfamily Scarabaeoidea is ''Protognathinus, Protognathinus spielbergi''. It had total length including mandibles about . The largest fossil Scarabaeidae, scarabaeid was ''Oryctoantiquus, 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, Gigatitan vulgaris'' was up to . ''Clatrotitan, Clatrotitan andersoni'' also reached a huge size, having a forewing of 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)

* Some Carboniferous cockroach-like insects grouping in Blattoptera like ''Archoblattina beecheri'' and ''Necymylacris (Xenoblatta) scudderi'' could reach around 9 centimetres in total length, which is comparable to a modern ''Megaloblatta longipennis''.
* Cretaceous cockroach ''Ptiloteuthis, Ptiloteuthis foliatus'' had long wing.
* Found in the Miocene of Austria, the giant termite ''Gyatermes, 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 single wing of . ''Meganeura'' had a long wing.
* Triadotypidae, Triadotypid odonatan ''Reisia, Reisia gelasii'' (=''Triadotypus guillaumei'') from Triassic had long wing, and wingspan can be .

Mayflies (Ephemeroptera)

* The largest known mayfly is Permian ''Ponalex, Ponalex maximus'', with long hindwing. Cretaceous ''Epicharmeropsis, Epicharmeropsis quadrivenulosus'' had long forewing.
* Although ''Bojophlebia, 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 subcircular wing known from Piesberg Quarry belongs to palaeodictyopteran, it possibly had single wing length at least .

Archaeognatha (jumping bristletails) and other wingless primitive insects

* The largest known Machilidae, machilid is Triassic ''Gigamachilis'', with body length not counting the length of the Cercus, 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 -long silverfish, it was later considered that classification is uncertain and just treated as Crown group, stem group insect.
* Wingless early insect ''Carbotriplura'' had body length about without tail filaments.

Ringed worms (Annelida)

''Websteroprion'' is the largest known fossil eunicidan Annelida, annelid, with estimated length ranges , however comparison with closely related extant taxa indicates length around . It also had the biggest scolecodonts of any prehistoric polychaete, up to in length and possibly larger.

Molluscs (Mollusca)

Snails and slugs (Gastropoda)

* The largest known Gastropoda, gastropods were in the genus ''Campanile (gastropod), Campanile'', with the extinct ''Campanile giganteum'' having shell lengths up to or even more than .
* The largest known cowrie is ''Vicetia (gastropod), 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.Wesselingh F. P. (2006). "Molluscs from the Miocene Pebas Formation of Peruvian and Colombian Amazonia". ''Scripta Geologica'' 133: 19-290. Figure 274
abstractPDF
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Bivalves (Bivalvia)

* The largest known bivalve ever as well as the largest Inoceramidae, 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 Alatoconchidae, alatoconchid genus like ''Shikamaia'' had shell length about . Previous estimation reconstructed length of ''Shikamaia'' around .
* The longest Ostreida, ostreid is ''Konbostrea'', with shell height reaching up to .
* Rudists, Rudist ''Titanosarcolites'' had overall size around .

Tusk shells (Scaphopoda)

* Complete shell length of tusk shell ''Prodentalium, Prodentalium onoi'' is estimated to be over .

Cephalopods (Cephalopoda)

Nautiloids (Nautiloidea)

The largest and longest known of Nautiloidea, nautiloids was ''Endoceras, Endoceras giganteum'' with a shell length of . There is a record of 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, 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)

* Octopus, Octopod ''Enchoteuthis, Enchoteuthis melanae'' (considered as specimen of ''Tusoteuthis, Tusoteuthis longa'') had mantle length up to , comparable to the modern-day giant squid. Previously, this taxon is considered as animal like giant squid, with total length including arms over . However, considering other fossil relatives, total length including arms is estimated to be around .
* Both non-octopod ''Yezoteuthis'' and Squid, teuthid ''Haboroteuthis'' are estimated to be similar in size to the modern-day giant squid.

Brachiopods (Brachiopoda)

The largest brachiopod ever evolved was ''Striatifera, 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, 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, Cordubia gigantea'', with diameter of . Specimens from the Cambrian of Wisconsin reached in length.

Vendobionts (Vendobionta)

Petalonamids (Petalonamae)

Longest specimens of ''Trepassia, Trepassia wardae'' (also known as ''Charnia wardi'') reached in length.M. LAFLAMME, G. M. NARBONNE, C. GREENTREE & M. M. ANDERSON. 2016
Morphology and taphonomy of an Ediacaran frond: Charnia from the Avalon Peninsula of Newfoundland
Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, Ontario, Canada K7L 3N6
Archived copy
from 18 August 2022. ''Charnia, Charnia masoni'' is known from specimens as small as only , up to the largest specimens of in length.

Proarticulata

''Dickinsonia, Dickinsonia rex'' 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

* Dinosaur size
* Largest organisms
* Megafauna

References

Sources

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External links

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{{DEFAULTSORT:Largest Prehistoric Organisms
Lists of prehistoric animals
Lists of largest animals, Prehistoric