The largest extinct animals known to date are listed here. They are arranged by their taxonomy (classification). The list only deals with individual animals; size of colonies (such as coral reefs) is not dealt with here.

Vertebrates

Fish 
 Bony fish
The largest bony fish of all time was Leedsichthys problematicus from the Middle Jurassic, at around  long. Earlier claims have been scaled down.
 Cartilaginous fish

The extinct megatoothed shark, C. megalodon is by far the biggest and most powerful shark that ever lived. This giant shark reached a length of more than . Recent higher estimates place the largest individuals of Megalodon at 20.3 meters (66 ft), making it the largest fish of all time.

Reptiles

Turtles 
The largest fossil turtle seems to be the freshwater turtle Stupendemys, with an estimated total carapace length of more than 11 feet (3.3 metres). A close contender is Archelon ischyros, a sea turtle, which reached a length of 16 feet (4.8 m) across the flippers and a weight of over 4,850 lb (2,200 kg). For comparison, the largest living turtle is the Leatherback Sea Turtle at a maximum 2000 lbs (900 kg).

Archosaurs 
 Crocodiles
While often suggested to be the largest crocodilian, Sarcosuchus imperator has been recently cut down to 4 tonnes in weight and 9 meters in length.   Deinosuchus, estimated at around , is a strong contender for the title.

Pterosaurs 
The largest pterosaur was Quetzalcoatlus northropi, at 127 kg (280 lbs) and with a wingspan of 11 m (36 ft). Another close contender is Hatzegopteryx, also with a wingspan of 11 m (this estimate is based on a skull 3 m long (10 ft).

Dinosaurs 
 Sauropods

Titanosaurs hold the world record for the size of a land animal. A recent discovery in the Argentine found Dreadnoughtus, an estimated length of 26 metres (85 feet) and weight of 59,291 kg (65.4 short tons). Its bones showed it was a sub-adult.

A notably large titanosaurid is Argentinosaurus, which is known from partially preserved remains. This sauropod has been estimated as  long and 73–99 metric tons in weight. The lack of skeletal material makes these estimates uncertain.

 Ornithopods

The very largest ornithopods, like Shantungosaurus were as heavy as medium-sized sauropods at up to 23 metric tons Lambeosaurus laticaudus appears to be close contender at around  in length.

 Theropods
The largest known theropod is Spinosaurus aegyptiacus, estimated at  in length and around 7–9 metric tons in weight. Spinosaurus aegyptiacus is also recognized as the largest terrestrial predator yet known.

A close contender in size is a giant theropod from South America, Giganotosaurus carolinii, whose holotype specimen is estimated at  in length, and another specimen is estimated at  in length. A study however presents Carcharodontosaurus as a close contender in size to Spinosaurus aegyptiacus. Some other notable giant theropods (e.g. Tyrannosaurus rex, Acrocanthosaurus, and Mapusaurus) may also have rivaled these giant theropods in size. Another very large theropod was Deinocheirus, being  tall at hips,
and weighing up to 16,000 pounds. The largest dromaeosaurid is Utahraptor. In addition to being the largest known dromaeosaurid, it was also the largest known deinonychosaur and the largest known paravian.
 Armoured dinosaurs
The largest thyreophoran was Ankylosaurus at  in length and 6.5 tons in weight. Stegosaurus was also 9 meters (30 ft) long but around 5 tons in weight.
 Ceratopsia
The largest ceratopsian known is probably the newly discovered Eotriceratops with a skull alone being  in length. Maximum size of this ceratopsian is suggested to be around  in length and 13 tonnes in weight.

Ichthyosaurs 
The largest ichthyosaur was Shonisaurus sikanniensis at ~21 metres (70 ft) in length. This would make it the largest extinct marine animal.

Plesiosaurs 
 Long-necked plesiosauridae
The largest plesiosaur was Mauisaurus haasti, growing to about 20 metres (66 ft) in length. Next behind was Elasmosaurus at 14 metres (46 ft) long.
 Pliosaurs
There is much controversy here. Fossil remains of a pliosaur nicknamed Predator X were excavated from Norway in 2008. It was about  in length and 41 metric tons in weight. However, in 2002, a team of paleontologists in Mexico discovered the remains of a pliosaur Monster of Aramberri, which is also estimated at  in length. However, this specimen is thought to be a juvenile, with evidence that it had been attacked by an even larger pliosaur. Some media claimed that Monster of Aramberri was a Liopleurodon this is unconfirmed.

Squamata 
 Snakes
The largest known prehistoric snake is Titanoboa, estimated at  in length and 1135 kg–1819 kg in weight. Another large fossil snake is Gigantophis, estimated at around  in length. Both these snakes lived in tropical rain forests. In third place is an aquatic snake,  Palaeophis colossaeus, which may have been around  in length.
 Mosasaurs
Giant mosasaurs are the largest animals in the Squamata. The largest known mosasaur is likely Mosasaurus hoffmanni, estimated at least  in length. A close contender in size is Hainosaurus bernardi, estimated at  in length. Another giant mosasaur is Tylosaurus, estimated at  in length.

Birds  

The largest birds of all time might have been the elephant birds of Madagascar. Of almost the same size was the Australian Dromornis stirtoni. Both were about 3 m tall (10 ft). The elephant birds were up to 400 kg and Dromornis was up to 500 kg in weight. The tallest bird ever was the Giant Moa (Dinornis maximus) at 12 ft tall.

The largest flight-capable bird was Argentavis magnificens which had a wingspan of 7 m (~23 ft), and a body weight of 110 kg (244 lb), or Pelagornis sandersi with a wingspan of 6.4 to 7.4 metres.

Mammals

Whales 

Basilosaurus was once recognized as one of the largest known extinct cetaceans at  in length.

The largest fossil toothed whale was the Miocene whale Livyatan melvillei which was estimated to be  in length. One notable feature of L. melvillei was its teeth which were 36 cm long and is unmatched by any other animal, extinct or alive.

However, the largest fossil whales were baleen whales (plankton feeders) from the Pliocene and Pleistocene Epochs. A notable example is the bones of a Pliocene age baleen whale, assigned the questionable name "Balaenoptera sibbaldina", which likely rivaled the modern blue whale in size.

Land mammals 

The largest perissodactyl, and land mammal, of all time was Palaeoloxodon namadicus. It stood 5.5 m (18 ft) tall at the shoulder, with a total height of 8 m (27 ft). It was 12 m (40 ft) long and may have weighed 20 tonnes (22 tons), though mass estimates vary. Some prehistoric horned rhinos also grew to large sizes. The giant woolly rhino Elasmotherium reached 20 ft long and 6.6 ft high.

Invertebrates

Myriapoda

Millipedes (Diplopoda) 
The largest by far was the giant Arthropleura. Measuring 2.5 metres (8.2 ft) and 45 centimetres (18 in) wide, it was the largest terrestrial arthropod of all time.

References 

Zoology
Fossils
Lists of animals