Toxodonta
Encyclopedia
Toxodonta is a suborder of the extinct
mammal
ian order Notoungulata
. The group is named after Toxodon
, the first example of the group to be discovered. The suborder includes the largest known notoungulates, members of the family Toxodontidae
. Toxodontids first appeared during the Oligocene
in the form of Proadinotherium. Another well-known toxodontid is Nesodon
, a medium-sized Miocene
toxodontid descended from Proadinotherium which had converted its second upper incisor
s into tusks. Toxodon itself evolved during the Pliocene
alongside the related Trigodon
, an equally large mammal
which possessed a horn
projecting from its forehead
, in the same way as a modern rhinoceros
. Toxodon was a huge herbivore
(about the size of a modern black rhinoceros
) with four toes on each hoof.
Closely related to the toxodontids are two additional families: the Leontiniidae
of the Eocene
through Miocene and the Notohippidae
. The last surviving notohippid was Colpodon from the late Oligocene, which was medium-sized but heavily built. Notohippids possessed molars
that were superficially like those of modern horse
s.
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
ian order Notoungulata
Notoungulata
Notoungulata is an extinct order of hoofed, sometimes heavy bodied mammalian ungulates which inhabited South America during the Paleocene to Pleistocene, living from approximately 57 Ma to 11,000 years ago.-Taxonomy:...
. The group is named after Toxodon
Toxodon
Toxodon is an extinct mammal of the late Pliocene and Pleistocene epochs about 2.6 million to 16,500 years ago. It was indigenous to South America, and was probably the most common large-hoofed mammal in South America at the time of its existence....
, the first example of the group to be discovered. The suborder includes the largest known notoungulates, members of the family Toxodontidae
Toxodontidae
Toxodontidae is an extinct family of notoungulate mammals known from the Oligocene through the Pleistocene of South America, with one genus, Mixotoxodon, also known from the Pleistocene of Central America. They somewhat resembled rhinoceroses, and had teeth with high crowns and open roots,...
. Toxodontids first appeared during the Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
in the form of Proadinotherium. Another well-known toxodontid is Nesodon
Nesodon
Nesodon is a genus of Miocene mammal belonging to the extinct order Notoungulata which inhabited southern South America during the Late Oligocene to Miocene living from 29.0—16.3 Ma and existed for approximately .-Taxonomy:...
, a medium-sized Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
toxodontid descended from Proadinotherium which had converted its second upper incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
s into tusks. Toxodon itself evolved during the Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
alongside the related Trigodon
Trigodon
Trigodon gaudryi is an extinct species of the family Toxodontidae, a large bodied notoungulate which inhabited South America during the Miocene living from 11.61—7.25 Ma and existed for approximately ....
, an equally large mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
which possessed a horn
Horn (anatomy)
A horn is a pointed projection of the skin on the head of various animals, consisting of a covering of horn surrounding a core of living bone. True horns are found mainly among the ruminant artiodactyls, in the families Antilocapridae and Bovidae...
projecting from its forehead
Forehead
For the Arsenal striker see GervinhoIn human anatomy, the forehead is the fore part of the head. It is, formally, an area of the head bounded by three features, two of the skull and one of the scalp. The top of the forehead is marked by the hairline, the edge of the area where hair on the scalp...
, in the same way as a modern rhinoceros
Rhinoceros
Rhinoceros , also known as rhino, is a group of five extant species of odd-toed ungulates in the family Rhinocerotidae. Two of these species are native to Africa and three to southern Asia....
. Toxodon was a huge herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
(about the size of a modern black rhinoceros
Black Rhinoceros
The Black Rhinoceros or Hook-lipped Rhinoceros , is a species of rhinoceros, native to the eastern and central areas of Africa including Kenya, Tanzania, Cameroon, South Africa, Namibia, Zimbabwe, and Angola...
) with four toes on each hoof.
Closely related to the toxodontids are two additional families: the Leontiniidae
Leontiniidae
Leontiniidae is an extinct family comprising six genera of notoungulate mammals known from the middle Eocene through middle Miocene of South America .-References:...
of the Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
through Miocene and the Notohippidae
Notohippidae
Notohippidae is an extinct family of notoungulate mammals from South America. Notohippids are known from the Eocene and Oligocene epochs....
. The last surviving notohippid was Colpodon from the late Oligocene, which was medium-sized but heavily built. Notohippids possessed molars
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
that were superficially like those of modern horse
Horse
The horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...
s.