Anachlysictis
Encyclopedia
Anachlysictis is an extinct genus
of carnivorous mammal
belonging to the group Sparassodonta
, related to the current metatherian marsupial
s that inhabited South America
during the Cenozoic
. Unlike other remains assigned to the family Thylacosmilidae (group of marsupial predators equipped with "saber tooth") had been found until its discovery, Anachlysictis is the first record of such borhyaenoids in northern South America, and also most primitive and ancient in the family (in fact, is the first confirmed record that did not belong to the genus Thylacosmilus, until the official publication of Patagosmilus in 2010). This species was found in the Villavieja Formation in the area of La Venta
in Colombia
, a famous fossil deposit in the mid-Miocene
(13-11 million years ago), based on fragments that include a front portion of the lower jaw, with an incipient molar tooth and a piece of carnasial from the front of the maxilla.
Anachlysictis, unlike its better known relative, Thylacosmilus
, was smaller, weighing around 18 kilograms, and the specialized features of the latter as the flanges on the lower jaw to adjust the fangs were smaller (due to the upper canines were not so long, in terms of proportions) and lacked the rim of the eye socket, which would give to the skull
a flattened profile. Otherwise it can be assumed that their anatomy was generally not as specialized as that of his later relatives, but it had carnassial
teeth to process more effectively meat and flat fangs, located just below the nose, without being cross-rounded as in other unspecialized mammal carnivores, while the accommodation area of the masseter muscle (involved in the movements of the jaw) it was reduced This is because as in other predatory saber-toothed more derivated, such as Thylacosmilus and the cat Smilodon
, this muscle is reduced, leaving more space for the jaw joint to increase its opening angle, which although affecting mandibular power, is compensated because they do not need an impressive bite force to use their canines, because they let the well-developed neck muscles are responsible to bring down the skull and allow the fangs to cross through the flesh of their prey.
Notably, until its discovery was supposed that Thylacosmilus was a close relative of the family Borhyaenidae
, or even a specialized member of the same, having emerged in the late Miocene; the most primitive characteristics and age of Anachlysictis suggest a previous origins of the thylacosmilids at the base of the superfamily Borhyaenoidea, whose monophyly
needs review. In fact, the pattern of the molars of Anachlysictis is very similar to the little known methatherian Hondadelphys, also from the La Venta that was considered early as a rare species of opossum and now considered a primitive member of the Sparassodonta
, so Hondadelphys could well represent the sister clade of Thylacosmilidae.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of carnivorous 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...
belonging to the group Sparassodonta
Sparassodonta
Sparassodonta is an extinct order of carnivorous metatherian mammals native to South America. They were once considered to be true marsupials, but are now thought to be a sister taxon to them. A number of these mammalian predators closely resemble placental predators that evolved separately on...
, related to the current metatherian marsupial
Marsupial
Marsupials are an infraclass of mammals, characterized by giving birth to relatively undeveloped young. Close to 70% of the 334 extant species occur in Australia, New Guinea, and nearby islands, with the remaining 100 found in the Americas, primarily in South America, but with thirteen in Central...
s that inhabited South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
during the Cenozoic
Cenozoic
The Cenozoic era is the current and most recent of the three Phanerozoic geological eras and covers the period from 65.5 mya to the present. The era began in the wake of the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and...
. Unlike other remains assigned to the family Thylacosmilidae (group of marsupial predators equipped with "saber tooth") had been found until its discovery, Anachlysictis is the first record of such borhyaenoids in northern South America, and also most primitive and ancient in the family (in fact, is the first confirmed record that did not belong to the genus Thylacosmilus, until the official publication of Patagosmilus in 2010). This species was found in the Villavieja Formation in the area of La Venta
La Venta (Colombia)
La Venta is a settlement between the modern Tolima Department and Huila Department, Colombia. Nearby, one of the richest Neogene fossil assemblages in the whole of South America is known...
in Colombia
Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...
, a famous fossil deposit in the mid-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...
(13-11 million years ago), based on fragments that include a front portion of the lower jaw, with an incipient molar tooth and a piece of carnasial from the front of the maxilla.
Anachlysictis, unlike its better known relative, Thylacosmilus
Thylacosmilus
Thylacosmilus was a genus of sabre-toothed metatherian predators that first appeared during the Miocene. Remains of the animal have been found in parts of South America, primarily Argentina...
, was smaller, weighing around 18 kilograms, and the specialized features of the latter as the flanges on the lower jaw to adjust the fangs were smaller (due to the upper canines were not so long, in terms of proportions) and lacked the rim of the eye socket, which would give to the skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
a flattened profile. Otherwise it can be assumed that their anatomy was generally not as specialized as that of his later relatives, but it had carnassial
Carnassial
Carnassials are large teeth found in many carnivorous mammals, used for shearing flesh and bone in a scissor- or shear-like way. In the Carnivora, the carnassials are the modified last upper premolar and the first molar, but in the prehistoric creodonts, the carnassials were further back in the...
teeth to process more effectively meat and flat fangs, located just below the nose, without being cross-rounded as in other unspecialized mammal carnivores, while the accommodation area of the masseter muscle (involved in the movements of the jaw) it was reduced This is because as in other predatory saber-toothed more derivated, such as Thylacosmilus and the cat Smilodon
Smilodon
Smilodon , often called a saber-toothed cat or saber-toothed tiger, is an extinct genus of machairodonts. This saber-toothed cat was endemic to North America and South America, living from near the beginning through the very end of the Pleistocene epoch .-Etymology:The nickname "saber-tooth" refers...
, this muscle is reduced, leaving more space for the jaw joint to increase its opening angle, which although affecting mandibular power, is compensated because they do not need an impressive bite force to use their canines, because they let the well-developed neck muscles are responsible to bring down the skull and allow the fangs to cross through the flesh of their prey.
Notably, until its discovery was supposed that Thylacosmilus was a close relative of the family Borhyaenidae
Borhyaenidae
The borhyaenids, members of the Borhyaenidae family of metatherians , were a carnivorous group of otter/wolverine-shaped marsupials in the order Sparassodonta. They lived in the Miocene of South America . Like most metatherians, they had a pouch to carry their offspring around...
, or even a specialized member of the same, having emerged in the late Miocene; the most primitive characteristics and age of Anachlysictis suggest a previous origins of the thylacosmilids at the base of the superfamily Borhyaenoidea, whose monophyly
Monophyly
In common cladistic usage, a monophyletic group is a taxon which forms a clade, meaning that it contains all the descendants of the possibly hypothetical closest common ancestor of the members of the group. The term is synonymous with the uncommon term holophyly...
needs review. In fact, the pattern of the molars of Anachlysictis is very similar to the little known methatherian Hondadelphys, also from the La Venta that was considered early as a rare species of opossum and now considered a primitive member of the Sparassodonta
Sparassodonta
Sparassodonta is an extinct order of carnivorous metatherian mammals native to South America. They were once considered to be true marsupials, but are now thought to be a sister taxon to them. A number of these mammalian predators closely resemble placental predators that evolved separately on...
, so Hondadelphys could well represent the sister clade of Thylacosmilidae.