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 6–7 m (20–23 ft). Cotylorhynchus hancocki is also large, with an estimated length and weight of at least 6 m (20 ft) and more than 500 kg (1,100 lb).
Edaphosaurids (Edaphosauridae)
The largest edaphosaurids were Lupeosaurus at 3 m (9.8 ft) long and Edaphosaurus, which could reach even more than 3 m (9.8 ft) in length. With weights of 166 kg (366 lb) and 300 kg (660 lb) respectively.
Sphenacodontids (Sphenacodontidae) The biggest carnivorous synapsid of the Early Permian was Dimetrodon, which could reach 4.6 m (15 ft) and 250 kg (550 lb). 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 5.5 m (18 ft) 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 4.5 m (15 ft) long, 2.6 m (8 ft 6 in) tall, and 9,000 kg (20,000 lb) 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 2.5 m (8 ft 2 in) in length, possibly up to 6 m (20 ft) and more than 600 kg (1,300 lb) in weight for adult specimens.
Dinocephalians (Dinocephalia)
Perhaps the largest known dinocephalian was the titanosuchid Jonkeria truculenta, with volumetric models suggesting it could have weighed 985 kg (2,172 lb). Tapinocaninus pamelae was slightly smaller, volumetric models suggesting it weighed 892.63 kg (1,967.9 lb). The largest carnivorous non-mammalian synapsids was the anteosaurid Anteosaurus, which was 5–6 m (16–20 ft) long, and weighed 500–600 kg (1,100–1,300 lb). Fully grown Titanophoneus from the same family likely had a skull of 1 m (3.3 ft) long.
Gorgonopsians (Gorgonopsia)
Inostrancevia latifrons is the largest known gorgonopsian, with a skull length of more than 60 cm (24 in), a total length approaching 3.5 m (11 ft) and a mass of 300 kg (660 lb). Rubidgea atrox is the largest African gorgonopsian, with skull of nearly 45 cm (18 in) long. Other large gorgonopsians include Dinogorgon with skull of ~40 cm (16 in) long, Leontosaurus with skull of almost 40 cm (16 in) long, and Sycosaurus with skull of ~38 cm (15 in) long.
Therocephalians (Therocephalia)
The largest whaitsiid, as well as the largest eutherocephalian and therocephalian, was Megawhaitsia, which had an estimated skull length of 40–50 cm (16–20 in). The largest known scylacosaurid was Julognathus, with an estimated skull length of 43 cm (17 in). The largest lycosuchid therocephalian may have been “Scymnosaurus major”, with an estimated skull length of 40 cm (16 in). It was thought that “Scymnosaurus” was similar in size to a modern hyena. Another large lycosuchid was Simorhinella with the an estimated skull length of ~37 cm (15 in). Gorynychus sundyrensis was a large basal therocephalian with an estimated skull length of 35–40 cm (14–16 in).
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 61.7 centimetres (24.3 in) based on a fragmentary specimen. Paceyodon davidi was the largest of morganucodontans, cynodonts close to mammals. It is known by a right lower molariform 3.3 mm (0.13 in) in length, which is bigger than molariforms of all other morganucodontans. The largest known docodont was Castorocauda, almost 50 cm (20 in) 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 1 m (3 ft 3 in) and an estimated mass of 12–14 kg (26–31 lb). With such parameters it surpassed in size several small theropod dinosaurs of the Early Cretaceous. Gobiconodon was also a large mammal, it weighed 5.4 kilograms (12 lb), had a skull of 10 cm (3.9 in) in length, and had 35 cm (14 in) in presacral body length.
Multituberculates (Multituberculata) The largest multituberculate, Taeniolabis taoensis is the largest non-therian mammal known, at a weight possibly exceeding 100 kg (220 lb).
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 30 kg (66 lb). 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 1 m (3 ft 3 in).
Metatherians (Metatheria)
… excerpt ends here. Continue reading the full article.
