Ground (giant) sloths

Main article: The history of the Earth before the appearance of hominids

Giant sloths appeared about 35 million years ago and lived in the New World, reaching a mass of several tons and a height of 6 meters. Unlike modern sloths, their giant relatives lived not on trees, but on the ground.

Giant sloths are representatives of incomplete (Latin Xenarthra) - a superorder of mammals living in South, North and Central America. The superorder includes 2 orders, 5 families and 29 species. The largest modern representative of the partial-toothed is the giant anteater (Myrmecophaga tridactyla).

Incomplete teeth either have no teeth at all, like anteaters, or their structure is simplified: there are no enamel and roots, all teeth are the same - there is no division into incisors and fangs (except for double-toed sloths having fang teeth), and grow constantly.

Giant sloths belonged to the few South American species that, after the emergence of a natural land bridge with North America, were able to spread to the northern mainland, which indicates their significant adaptation abilities.

They were probably easy prey for the first people who settled their habitat, since like their modern relatives they moved very slowly.

The following families of ground sloths are distinguished:

• Megatheriidae,
• Mylodontidae,
• Nothrotheriidae,
• Orthopodiidae и
• Scelidotheriidae.

Megatherias

Megatheria (from the Greek mega [μέγας] "huge," and therion [θηρίον], "beast") is the last and most famous of the giant ground sloths that lived 2-0.010 million years ago.

Researches

The first fossil skeleton of megatherium was discovered in Argentina in 1787. Until then, scientists could not even imagine how large prehistoric animals could reach. The indigenous people of Patagonia thought the bones belonged to a huge mole. According to local legend, he once got out of the ground and was killed by sunlight. The viceroy of the Spanish colony, Marquis Loreto, immediately sent the bones to Madrid, where he studied this skeleton in detail for several years at Joseph Garriga. In 1795, the scientist completed his work and transferred the manuscript to the printing house. After receiving the first proofread of the scientist, the governor of the French colony, San Domingo, visited and asked him for one copy of his work, in which the alleged image of the animal was also placed. Garriga, unaware of the governor's actual intentions, gave him his job. The latter immediately sent the work to the Paris Academy of Sciences, where at the next meeting the famous paleontologist Cuvier made a message about an interesting find and established that the skeleton belongs to an animal named Megatherium americanum. Thus, he was ahead of the work of I. Garriga by a whole year (his work was published only in 1796).

Garriga compared him to an elephant, since the size of the South American beast was in no way inferior to him. However, his paws with huge feet were longer and heavier than elephants, and the shape of the skull, as the scientist noted in his work, resembled the head of a sloth.

When the skeletons of megatheres were first exhibited in European museums, they caused a sensation. Then the German poet I.V. Goethe dedicated a whole essay to a giant sloth. Museums, in order to get his skeleton, were ready to give their entire annual budget. And the King of Spain Carlos IV demanded to deliver this animal to Madrid. Moreover, the ruler was indifferent whether it would be alive or dead. He naively believed that the New World, as America was then called, is still inhabited by megatheres.

In addition to hundreds of bones, scientists found petrified skin, wool and megatheria litter in caves, and prints of his paws on the muddy banks of rivers. All this helped paleontologists not only recreate the appearance of the beast, but also study in detail its diet and habits.

Megatherius did not climb trees like his modern descendant. Charles Darwin, who studied his remains in the 18th century, noted this feature of the animal in one of his works. He seemed ridiculous the idea of ​ ​ the existence of plants that could withstand such a giant.

Professor Richard Owen also participated in the study of the remains brought by Darwin from Patagonia to England. It was he who suggested that megatherium moved on the ground. When walking, a giant sloth, like a modern anteater, rested not on the entire foot, but on its edge, so as not to cling to the ground with its claws. Because of this, he moved slowly and a little clumsily.

The skeletons of the megatheria caused a stir among the public until the beginning of the 20th century, when dinosaur skeletons appeared in museums. Prior to that, European museums spent a lot of money on the purchase of these skeletons.

Appearance and lifestyle

Scientists believe that megatherias could live both in groups and individually, in caves. Most of the time they moved on four legs, but often got up and only on the back. This was usually done in order to tear fresh leaves from high branches, to which other herbivores could hardly reach.

Sloths used their short tail as an additional support to get to the foliage in the trees. Long claws reaching 17 cm helped them bend fresh greens and dig up useful roots. The powerful backbone, developed muscles and long claws made adult sloths virtually invulnerable to predators. These animals fed mainly on vegetation, but did not refuse and fell.

Until recently, scientists were sure that the sloth plucked the leaves with the help of an unusually long tongue. However, modern research has shown that the structure of his jaw prevented the formation of muscles that could keep him.

Despite the fact that megatherias could easily reach the tall branches of trees, they mainly fed on low plants, for example, yucca or agave.

According to scientists, giant sloths spent a lot of time digesting eaten food. Their stomach was able to cope with rough and fibrous food, however, the sloths had to rest a lot after eating to help the digestion process.

Megatherias were previously thought to have been covered in thick long fur, reminiscent of the outwardly huge bear, more recent studies suggest that they rather possessed very thick rough and virtually hairless skin (like modern elephants). Even saber-toothed cats did not pose a danger to sloths. Under the skin were thousands of small bone plates that protected the animal from teeth and claws in the manner of chain mail.

Types

• Megatherium altiplanicum
• Megatherium tarijense
• Megatherium medinae
• Megatherium istilarti
• Megatherium parodii
• Megatherium sundti
• Megatherium gallardoi
• Megatherium americanum

Eremotherium

Eremotherium (Latin Eremotherium, from other Greek ἐρῆμος θηρίον "a lonely living beast") is an extinct genus of giant sloths, a representative of the megafauna, who lived from the Pliocene to the Pleistocene, 2.5 million - 11,000 years ago. Named by Spillmann in 1948.

With a length of 6 m and a weight of more than 3 tons, eremotheria is comparable in size to megatherium, but was wider, up to the state of the USA South Carolina, which makes it one of the largest sloths in North America. Eremotherium was found in the USA, Mexico, Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica, Panama, Venezuela, Ecuador, Peru, Brazil and Bolivia.

Eremotherium laurillardi mounted skeleton at Washington National Museum of Natural History

Types

According to the Fossilworks website, as of January 2019, 4 extinct species are included in the genus:

• Eremotherium eomigrans - described in 1999. Found only in Florida. He lived 4.9 million - 300,000 years ago.

• Eremotherium elenense (Hoffstetter, 1949) синоним Schaubia elenensis

• Eremotherium laurillardi, synonymous with Megatherium laurillardi, was described by Lund in 1842. Found in Brazil and nearby places. This species lived 780,000-11,000 years ago. E. mirabile (Leidy, 1855) and E. rusconii (Schaub, 1935) are recognized as synonyms to E. laurillardi.

• Eremotherium sefvei (De Iuliis and Saint-Andre, 1997)

Mylodontidae

Mylodontidae is an extinct family of ground sloths that existed from 23 million to 11 thousand years ago.

Mylodontinae includes five genera:

• Lestodon,
• Thinobadistes,
• Mylodon,
• Paramylodon,
• Glossotherium.

The Milodons

These sloths were somewhat inferior in size to megatheres. The largest representatives of the genus of the same name reached a three-meter length and corresponded in size to modern bulls. Their remains were first discovered in 1895. This happened in Chilean Patagonia, in the vicinity of the small pride of Puerto Natales, in one of the caves. Scientists suggest that the Milodons left Earth no later than 9 thousand years BC.

The genus Scelidotherium, which lived in South America from the early Pliocene until the end of the Pleistocene, differed in the special structure of the skull compared to other Milodons. There was also a genus Lestodon.

Glossotherium

A species of Glossotherium harani whose remains were found near Los Angeles in the United States on La Bray Ranch in asphalt pits.

Glossotherium robustum was endemic to South America and weighed about 1,500 kg.

Glossotherium robustum at Vienna Museum

Bone plate jewelry from the skin of giant sloths Glossotherium, made by the ancient inhabitants of the continent, was found in Santa Elina in the Brazilian state of Mato Grosso.

Excavation site in Santa Elina, left. Sloth bones with drilled holes (right)

In 2017, they were dated 23.12 thousand years ago^[1]. Dating baffles scientists who traditionally believe that South America was inhabited no earlier than 13 thousand years ago.

A human encounter with a megafauna representative (possibly a giant sloth) at one of the rock paintings in Brazil's Serra da Capivara National Park

Thalassoknus - water sloths

In addition, there was also a giant sloth thalassoknus, which lived off the coast of modern Peru and led a aquatic or, possibly, semi-aquatic lifestyle. Unfortunately, there is very little material for this sloth and they belong to the Miocene and Pliocene. Presumably, these aquatic giant sloths fed mainly on coastal grass and seaweed. Over time, they began to consume less shallow vegetation, switching to deeper water. Presumably, they used their powerful claws for this, which kept their bodies near the bottom, as modern marine iguanas do. This genus was also close to megateria^[2].

Megaloknus

The remains of giant sloths (megaloknus) were found in the Caribbean. During his lifetime, the animal weighed up to 90 kilograms. Two species are distinguished - M. rodens from Cuba and M. zile from Haiti.

Megaloknus on the island of Cuba survived to the Holocene and became extinct about 2960 years BC^[3]a thousand years after the first people appeared on the island.

The ancestors of sloths living on the islands of the Caribbean penetrated here even in the Oligocene (33-23 million years ago) or at the very beginning of the Miocene. Pleistocene species were mostly massive terrestrial forms, however they retained signs of their ancestors' arboreal lifestyles - much like gorillas among monkeys, for example. Their hands and feet were twisted inward so that they walked with their fingers resting on the back. The structure of the pelvis and hind limbs indicates the ability to hold the semi-bipedal (bipedal, but supported by the front legs on trunks and branches) body position, which made it possible to eat up tall trees.

Megalocnus rodens. American Museum of Natural History in New York

Cuban ground sloths survived their continental counterparts for several thousand years - megalonychid, megateriid and milodontid, extinct about 9-8 thousand years BC. The last sloth in Cuba was megaloknus, whose tooth from the location of Solapa de Siles in the province of Havana has a radiocarbon date of 4190±40 years ago. Thus, this species coexisted for at least a thousand years with people who appeared in the Greater Antilles in about 3200 BC.

Search for sloth survivors

Indian legends tell about the Mapinguari creature, which is described as coinciding with a huge sloth. Intrigued by these legends, cryptozoologists tried to find surviving individuals in the Amazon basin, but they failed.

Notes