Squirrels are members of the family Sciuridae, a family that includes small or medium-size rodents. The squirrel family includes tree squirrels, ground squirrels, and flying squirrels. Squirrels are indigenous to the Americas, Eurasia, and Africa, and were introduced by humans to Australia. The earliest known fossilized squirrels date from the Eocene epoch, and among other living rodent families, the squirrels are most closely related to the mountain beaver and to the dormice.
Haast's eagle is an extinct species of eagle that lived in the South Island of New Zealand, commonly accepted to be the pouakai of Māori legend. It was the largest eagle known to have existed, with an estimated weight of 15 kilograms, compared to the next-largest and extant 9 kg (20 lb) harpy eagle. Its massive size is explained as an evolutionary response to the size of its prey, the flightless moa, the largest of which could weigh 230 kg (510 lb). Haast's eagle became extinct around 1400, following the arrival of the Māori, who outcompeted it for its moa prey.
Phoberomys pattersoni is an extinct rodent that lived in the ancient Orinoco River delta around 8 million years ago. It was the second-largest of the roughly seven species of its genus. Like many other rodents, Phoberomys was a herbivore with high-crowned premolars and molars.
Marmots are large ground squirrels in the genus Marmota, with 15 species living in Asia, Europe, and North America. These herbivores are active during the summer, when they can often be found in groups, but are not seen during the winter, when they hibernate underground. They are the heaviest members of the squirrel family.
Ground squirrels are rodents of the squirrel family (Sciuridae) that generally live on the ground or in burrows, rather than in trees like the tree squirrels. The term is most often used for the medium-sized ground squirrels, as the larger ones are more commonly known as marmots or prairie dogs, while the smaller and less bushy-tailed ground squirrels tend to be known as chipmunks.
Megalania is an extinct species of giant monitor lizard, part of the megafaunal assemblage that inhabited Australia during the Pleistocene. It is the largest terrestrial lizard known to have existed, reaching an estimated length of 3.5 to 7 metres, and weighing between 97–1,940 kg (214–4,277 lb), but the fragmentary nature of known remains make estimates highly uncertain.
Argentavis is an extinct genus of teratornids known from three sites in the Epecuén and Andalhualá Formations in central and northwestern Argentina dating to the Late Miocene (Huayquerian), where a good sample of fossils has been obtained. The type species, A. magnificens, is sometimes called the giant teratorn. It was among the largest flying birds ever to exist. While it is still considered the heaviest flying bird of all time, Argentavis was likely surpassed in wingspan by Pelagornis sandersi which is estimated to have possessed wings some 20% longer than Argentavis and which was described in 2014.
Spermophilus is a genus of ground squirrels in the squirrel family. As traditionally defined the genus was very species-rich, ranging through Europe, Asia and North America, but this arrangement was found to be paraphyletic to the certainly distinct prairie dogs, marmots, and antelope squirrels. As a consequence, all the former Spermophilus species of North America have been moved to other genera, leaving the European and Asian species as true Spermophilus.
Castoroides, or giant beaver, is an extinct genus of enormous, bear-sized beavers that lived in North America during the Pleistocene. Two species are currently recognized, C. dilophidus in the Southeastern United States and C. ohioensis in most of North America. C. leiseyorum was previously described from the Irvingtonian age but is now regarded as an invalid name. All specimens previously described as C. leiseyorum are considered to belong to C. dilophidus.
Plesiadapis is one of the oldest known primate-like mammal genera which existed about 58–55 million years ago in North America and Europe. Plesiadapis means "near-Adapis", which is a reference to the adapiform primate of the Eocene period, Adapis. Plesiadapis tricuspidens, the type specimen, is named after the three cusps present on its upper incisors.
Archaeoindris fontoynontii is an extinct giant lemur and the largest primate known to have evolved on Madagascar, comparable in size to a male gorilla. It belonged to a family of extinct lemurs known as "sloth lemurs" (Palaeopropithecidae) and, because of its extremely large size, it has been compared to the ground sloths that once roamed North and South America. It was most closely related to Palaeopropithecus, the second largest type of sloth lemur. Along with the other sloth lemurs, Archaeoindris was related to the living indri, sifakas, and woolly lemurs, as well as the recently extinct monkey lemurs (Archaeolemuridae). The genus, Archaeoindris, translates to "ancient indri-like lemur", even though it probably became extinct recently, around 350 BCE.
Josephoartigasia is an extinct genus of enormous dinomyid rodent from the Early Pliocene to Early Pleistocene of Uruguay. The only living member of Dinomyidae is the pacarana. Josephoartigasia is named after Uruguayan national hero José Artigas. It contains two species: J. magna, described in 1966 based on a left mandible, and J. monesi, described in 2008 based on a practically complete skull. Both are reported from the San José Member of the Raigón Formation by the Barrancas de San Gregorio along the shores of Kiyú beach.
Titanohyrax is an extinct genus of large to very large hyrax from the Eocene and Oligocene. Specimens have been discovered in modern-day Algeria, Tunisia, Egypt and Libya. Some species, like T. ultimus, are estimated to be as large as the modern rhinoceros. Titanohyrax species are still poorly known due to their rarity in the fossil record.
The largest prehistoric animals include both vertebrate and invertebrate species. Many of them are described below, along with their typical range of size. 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.
Solimoea acrensis is a prehistoric ateline monkey from the Late Miocene Solimões Formation of Brazil. It is the only known species of the genus Solimoea.
The largest animal currently alive is the blue whale. The maximum recorded weight was 190 tonnes for a specimen measuring 27.6 metres (91 ft), whereas longer ones, up to 33.6 metres (110 ft), have been recorded but not weighed. It is estimated, this individual could have a mass of 250 tonnes. The longest non-colonial animal is the lion's mane jellyfish.
