extinct
Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
genus
Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
The first fossils of ''Megadolodus'' were uncovered from the Villavieja Formation, in the fossil locality
La Venta
La Venta is a pre-Columbian archaeological site of the Olmec civilization located in the present-day Mexican state of Tabasco. Some of the artifacts have been moved to the museum "Parque - Museo de La Venta", which is in nearby Villaherm ...
, in what is today
Colombia
Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...
, in terrains dated from the Middle
Miocene
The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
, between 13.5 and 11.8 millions of years ago. The genus was described in 1956 after the
holotype
A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...
UCMP 39270, consisting in a left mandible preserving the fourth premolar, the first molar and roots from the second molar, and discovered during an expedition organized by the
University of California
The University of California (UC) is a public university, public Land-grant university, land-grant research university, research university system in the U.S. state of California. Headquartered in Oakland, California, Oakland, the system is co ...
Malcolm McKenna
Malcolm Carnegie McKenna (1930–2008) was an American paleontologist and author on the subject.
Paleontologist
McKenna began his paleontology career at the Webb School of California (grades 9-12) in Claremont, California, under noted paleontolo ...
,Malcolm C. McKenna. Survival of primitive notoungulates and condylarths into the Miocene of Colombia. ''American Journal of Science'', Vol. 254, December 1956, P.736-743 who described them in his 1956 article, to believe they originated from a late surviving
Didolodontidae
Didolodontidae is a possibly paraphyletic family of "condylarth" mammals known from the Paleogene of South America, with most specimens known from Argentina. They were generally small-medium in body size, and had a bunodont dentition. A close rel ...
, a family of primitive ungulates that went extinct during the end of the
Eocene
The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...
, 25 millions of years before the apparition of ''Megadolodus'' in the fossil record; hence its genus name, meaning "large '' Didolodus''", a characteristic genus from this family. This classification supported the theory that the South American tropical zone acted as a refuge for primitive species during the
Neogene
The Neogene ( ,) is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period million years ago. It is the second period of th ...
.
New remains of ''Megadolodus'' were only uncovered during the 1980s from the Honda Group, in the
Magdalena River Valley
The Magdalena River (, ; less commonly ) is the main river of Colombia, flowing northward about through the western half of the country. It takes its name from the biblical figure Mary Magdalene. It is navigable through much of its lower reaches, ...
of Colombia, including parts of the legs, mandibles, teeths,
vertebrae
Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal ...
, pelvis and ribs, permitting a better understanding of the general anatomy of the animal, and allowing to compare it with
litoptern
Litopterna (from "smooth heel") is an extinct order of South American native ungulates that lived from the Paleocene to the Pleistocene-Holocene around 62.5 million to 12,000 years ago (or possibly as late as 3,500 years ago), and were also pres ...
s, resulting in its reclassification as an unusual Proterotheriidae. The discovery of a similar proterotheriid, ''
Bounodus
''Bounodus'' is an extinct genus of ungulates native from South America, belonging to the order Litopterna. Its remains were found in Miocene rocks from the Urumaco Formation of northern Venezuela. The genus is only known from its holotype, AMU-C ...
enigmaticus'' from
Venezuela
Venezuela, officially the Bolivarian Republic of Venezuela, is a country on the northern coast of South America, consisting of a continental landmass and many Federal Dependencies of Venezuela, islands and islets in the Caribbean Sea. It com ...
, confirmed that they belonged to a lineage of specialized litopterns from northern South America, classified in its own subfamily, the Megadolodinae. In 2024, partial mandible and teeth of ''Megadolodus'' are discovered from the Ipururo Formation of
Peru
Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...
.
Description
''Megadolodus'' was a member of the Proterotheriidae, a family of small and medium-sized litopterns who produced in a few derived genera forms loosely evoking
horses
The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 milli ...
, such as the well known genera ''
Thoatherium
''Thoatherium'' (meaning "active swift-beast") is an extinct genus of litoptern mammals from the Early Miocene of Argentina. Fossils of the genus have been found in the Santa Cruz Formation in Argentina.Diadiaphorus''. ''Megadolodus molariformis'', the only known species from its genus, was itself characterized by its shorter and stronger limbs, its large
tusk
Tusks are elongated, continuously growing front teeth that protrude well beyond the mouth of certain mammal species. They are most commonly canine tooth, canine teeth, as with Narwhal, narwhals, chevrotains, musk deer, water deer, muntjac, pigs, ...
-like
canine
Canine may refer to:
Zoology and anatomy
* Animals of the family Canidae, more specifically the subfamily Caninae, which includes dogs, wolves, foxes, jackals and coyotes
** ''Canis'', a genus that includes dogs, wolves, coyotes, and jackals
** Do ...
s which sharpened each other, and a large
hypocone
A cusp is a pointed, projecting, or elevated feature. In animals, it is usually used to refer to raised points on the crowns of teeth.
The concept is also used with regard to the leaflets of the four heart valves. The mitral valve, which has ...
on the third molar. The genus had only 10 to 11
thoracic vertebrae
In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebra (anatomy), vertebrae of intermediate size between the ce ...
, and 5
lumbar vertebrae
The lumbar vertebrae are located between the thoracic vertebrae and pelvis. They form the lower part of the back in humans, and the tail end of the back in quadrupeds. In humans, there are five lumbar vertebrae. The term is used to describe t ...
.Richard L. Cifelli, Carlos Villarroel, 1997. Paleobiology and Affinities of ''Megadolodus''. ''In Vertebrate Paleontology in the Neotropics. The Miocene Fauna of La Venta, Colombia''. Edited by Richard F. Kay, Richard H. Madden, Richard L. Cifelli, and John J. Flynn. Smithsonian Institution Press. Washington and London.
Like some
perissodactyl
Perissodactyla (, ), or odd-toed ungulates, is an order of Ungulate, ungulates. The order includes about 17 living species divided into three Family (biology), families: Equidae (wild horse, horses, Asinus, asses, and zebras), Rhinocerotidae ( ...
s such as
tapir
Tapirs ( ) are large, herbivorous mammals belonging to the family Tapiridae. They are similar in shape to a Suidae, pig, with a short, prehensile nose trunk (proboscis). Tapirs inhabit jungle and forest regions of South America, South and Centr ...
s, ''Megadolodus'' had three toes on each limb, with the axis on the third toe, while the second and fourth toe were smaller and located in each side of the leg, without touching the ground. Weight estimates based on the comparison of its limbs with those of extant mammals suggest a weight between 30 and 200 kg, probably more precisely between 65 and 80 kg. The fact that its body was not as slender than other proterotheriids, along with its canines and its
bunodont
The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone tooth ...
molars similar to modern-day
peccaries
Peccaries (also javelinas or skunk pigs) are pig-like ungulates of the family Tayassuidae (New World pigs). They are found throughout Central and South America, Trinidad in the Caribbean, and in the southwestern area of North America. Peccari ...
suggest that it was an animal similar in habits to modern
Suidae
Suidae is a family (biology), family of Even-toed ungulate, artiodactyl mammals which are commonly called pigs, hogs, or swine. In addition to numerous fossil species, 18 Extant taxon, extant species are currently recognized (or 19 counting domes ...
, living in forested environments such as La Venta, and eating roots and fruits.