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Sparassodonta (from Greek to tear, rend; and , gen. , ' tooth) is an
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 ...
order of carnivorous metatheria
Metatheria is a mammalian clade that includes all mammals more closely related to marsupials than to placentals. First proposed by Thomas Henry Huxley in 1880, it is a more inclusive group than the marsupials; it contains all marsupials as wel ...
n mammal
A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...
s native to South America, related to modern marsupial
Marsupials are a diverse group of mammals belonging to the infraclass Marsupialia. They are natively found in Australasia, Wallacea, and the Americas. One of marsupials' unique features is their reproductive strategy: the young are born in a r ...
s. They were once considered to be true marsupials, but are now thought to be a separate side branch that split before the last common ancestor of all modern marsupials.
A number of these mammalian predators closely resemble placental predators that evolved separately on other continents, and are cited frequently as examples of convergent evolution
Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last comm ...
. They were first described by Florentino Ameghino, from fossils found in the Santa Cruz beds of Patagonia. Sparassodonts were present throughout South America's long period of "splendid isolation" during the Cenozoic
The Cenozoic Era ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterized by the dominance of mammals, insects, birds and angiosperms (flowering plants). It is the latest of three g ...
; during this time, they shared the niches for large warm-blooded predators with the flightless terror birds. Previously, it was thought that these mammals died out in the face of competition from "more competitive" placental carnivorans
Carnivora ( ) is an Order (biology), order of Placentalia, placental mammals specialized primarily in eating flesh, whose members are formally referred to as carnivorans. The order Carnivora is the sixth largest order of mammals, comprising at ...
during the Pliocene
The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Great American Interchange, but more recent research has shown that sparassodonts died out long before eutherian carnivores arrived in South America (aside from procyonids, which sparassodonts probably did not directly compete with).
Sparassodonts have been referred to as borhyaenoids by some authors, but currently the term Borhyaenoidea refers to a restricted subgroup of sparassodonts comprising borhyaenids and their close relatives.
Almost all sparassodonts have an exceptionally shortened snout—most especially thylacosmylids. Hathliacynids usually have a longer snout than the other groups. The nasal bones extend past the eye sockets, often reaching the lacrimal bone. Except for thylacosmylids beyond '' Patagosmilus'', sparassodonts feature an open eye socket, with more marginalized (though nonetheless prominent) postorbital processes which would otherwise form the postorbital bar connecting the forehead to the cheek, thus framing the eye. They exhibit marked postorbital constriction. The orbital process (between the cheek and the eye socket) is usually diminished, though the zygomatic arch (the cheekbone) is strong. They feature a prominent sagittal crest along the midline of the flattened skull, the crest strength is quite variable among borhyaenids. They have an expanded
The dental formula of sparassodonts varies considerably. In borhyaenids, it is , with three upper and lower incisors, one upper and lower canine, three upper and lower premolars, and four upper and lower
Anatomy
Almost all sparassodonts have an exceptionally shortened snout—most especially thylacosmylids. Hathliacynids usually have a longer snout than the other groups. The nasal bones extend past the eye sockets, often reaching the lacrimal bone. Except for thylacosmylids beyond '' Patagosmilus'', sparassodonts feature an open eye socket, with more marginalized (though nonetheless prominent) postorbital processes which would otherwise form the postorbital bar connecting the forehead to the cheek, thus framing the eye. They exhibit marked postorbital constriction. The orbital process (between the cheek and the eye socket) is usually diminished, though the zygomatic arch (the cheekbone) is strong. They feature a prominent sagittal crest along the midline of the flattened skull, the crest strength is quite variable among borhyaenids. They have an expanded occipital bone
The occipital bone () is a neurocranium, cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone lies over the occipital lob ...
with a well defined nuchal crest.
Sparassodonts spanned a wide range of body sizes, from 2.2-pound (1 kg) weasel or civet-like forms to '' Thylacosmilus'', which was the size of a leopard. Along with the Australian thylacoleonids, sparassodonts include some of the largest metatherian carnivores.
Sparassodonts have highly reduced epipubic bones (pelvic bones which support the pouch), to the point that early analysis could not even find evidence for them. This is a characteristic shared with the Australian thylacine
The thylacine (; binomial name ''Thylacinus cynocephalus''), also commonly known as the Tasmanian tiger or Tasmanian wolf, was a carnivorous marsupial that was native to the Mainland Australia, Australian mainland and the islands of Tasmani ...
, and historically argued as a synapomorphy
In phylogenetics, an apomorphy (or derived trait) is a novel Phenotypic trait, character or character state that has evolution, evolved from its ancestral form (or Plesiomorphy and symplesiomorphy, plesiomorphy). A synapomorphy is an apomorphy sh ...
, though nowadays it is considered to have developed independently for poorly understood reasons. As with thylacines, it is very likely that they possessed long cartilaginous elements instead.
Teeth
The dental formula of sparassodonts varies considerably. In borhyaenids, it is , with three upper and lower incisors, one upper and lower canine, three upper and lower premolars, and four upper and lower molars
The molars or molar teeth are large, flat tooth, teeth at the back of the mouth. They are more developed in mammal, mammals. They are used primarily to comminution, grind food during mastication, chewing. The name ''molar'' derives from Latin, '' ...
in each half of either jaw. Proborhyaenids usually only have two lower incisors instead of three, except for '' Callistoe''. Thylacosmylids have at least two upper and only two lower incisors (the uppers grew into elongated sabers), and two upper and lower premolars. Some specimens of '' Borhyaena'' and '' Arctodictis'' are also missing the last upper molar, showing that the presence of this tooth was variable in these species.
Sparassodonta is characterized by dental synapomorphies that distinguish the group from other closely related mammals. Unequivocal traits uniting the earliest Sparassodonts include:
* a snout that forms a pronounced bulge around the canine teeth when viewed from above
* a ridge on the upper molar (preparacrista) oriented anterobuccally (towards the cheek) with respect to the long axis of the tooth.
* a pronounced keel near the base of the front of the paraconid
* ridges on lower molars (postprotocristid-metacristid) parallel or oblique with respect to lower jaw axis.
* a very tall protoconid (>90% tooth length, secondarily lost in ''Hondadelphys'' and ''Stylocynus'') that bulges to the side and is wider at its midpoint than its base
* talonid (crushing end) of lower molar narrow in relation to trigonid (shearing end).
In borhyaenids, only the third premolar was ever replaced in the animal's lifetime, similar to other metatherians. In thylacosmilids, only the lower third premolar was replaced.
The cusps of the sparassodont molar correlate to a cutting function rather than a crushing one. In the upper molars, the paracone (on the lingual, or tongueward, side) is reduced and fused to the metacone (distal, towards the back of the mouth), inflating the postmetacrista (the lingual border of the metacone); and they almost always lack the stylar shelf (on the buccal, or cheekward, side) and associated stylar cusps. In the lower molars, the trigonids (the buccal shearing side) have an inflated paracristid and marginalized or absent metaconid; and the talonid (the distal, or backendwards, crushing side) is either reduced or gone.
Taxonomy
Classification
Sparassodonts can be divided into six major groups; basal sparassodonts (?earliestPaleocene
The Paleocene ( ), or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), ...
-late 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 ...
), species that cannot be easily assigned to any of the other sparassodont groups and whose teeth often exhibit adaptations for omnivory; hathliacynids (late Oligocene
The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
-early Pliocene
The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58marten to a
thylacine
The thylacine (; binomial name ''Thylacinus cynocephalus''), also commonly known as the Tasmanian tiger or Tasmanian wolf, was a carnivorous marsupial that was native to the Mainland Australia, Australian mainland and the islands of Tasmani ...
in size, and have long, fox-like muzzles and teeth strongly suited for carnivory; basal borhyaenoids (middle 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 ...
-late Miocene), borhyaenoids which are unable to be easily classified into the families Borhyaenidae, Thylacosmilidae, or Proborhyaenidae
Proborhyaenidae is an extinct Family (biology), family of metatherian mammals of the order Sparassodonta, which lived in South America from the Eocene (Mustersan) until the Oligocene (Deseadan). Sometimes it has been included as a subfamily of th ...
and range in form and size; borhyaenids (early-late Miocene), the sparassodont group most specialized for running, but not as much as living carnivorans
Carnivora ( ) is an Order (biology), order of Placentalia, placental mammals specialized primarily in eating flesh, whose members are formally referred to as carnivorans. The order Carnivora is the sixth largest order of mammals, comprising at ...
or even thylacines; proborhyaenids (middle Eocene-late Oligocene
The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
), robust, wolverine
The wolverine ( , ; ''Gulo gulo''), also called the carcajou or quickhatch (from East Cree, ''kwiihkwahaacheew''), is the largest land-dwelling species, member of the family Mustelidae. It is a muscular carnivore and a solitary animal. The w ...
-like forms with ever-growing upper and lower canines; and thylacosmilids (early Miocene-late Pliocene), another terrestrially specialized group with ever-growing saber-like upper canines.
The taxonomic classification below follows the latest review of the group, that of Prevosti and Forasiepi (2018), with additions from more recent studies. Although ''Mayulestes'' was originally described as a sparassodont, later phylogenetic analyses have shown that it most likely does not belong to this group; however more recent studies show it to be closely related to sparassodonts. Similarly, while basal borhyaenoids such as ''Lycopsis'' and ''Prothylacynus'' were once thought to belong to a distinct family (Prothylacynidae), phylogenetic analyses have found that these animals do not represent a monophyletic
In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria:
# the grouping contains its own most recent co ...
group. The exact age of most Eocene species of sparassodonts is uncertain, given the lack of precise stratigraphic information associated with most specimens and the recent division of the Casamayoran SALMA into the Vacan and Barrancan SALMAs.
* Order Sparassodonta
** Genus '' Allqokirus''
***''Allqokirus australis'' (earliest Paleocene
The Paleocene ( ), or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), ...
, Tiupampan SALMA)
** Genus '' Mayulestes''
***''Mayulestes ferox'' (earliest Paleocene
The Paleocene ( ), or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), ...
, Tiupampan SALMA)
** Genus '' Argyrolestes''
** Genus '' Nemolestes''
***''Nemolestes spalacotherinus'' (late middle 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 ...
, Barrancan SALMA)
** Genus '' Patene''
***''Patene campbelli'' (late ?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 ...
, Santa Rosa local fauna)
***''Patene coloradensis'' (middle 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 ...
)
***''Patene coluapiensis'' (middle 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 ...
, Barrancan SALMA)
***''Patene simpsoni'' (late Paleocene
The Paleocene ( ), or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), ...
/early 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 ...
, Itaboraian SALMA)
** Genus '' Procladosictis''
***''Procladosictis anomala'' (late 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 ...
, Mustersan SALMA)
** Family Hondadelphidae
*** Genus '' Hondadelphys''
****''Hondadelphys fieldsi'' (late 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 ...
, Laventan SALMA)
*** Genus '' Stylocynus''
****''Stylocynus paranensis'' (latest 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 ...
, Huayquerian SALMA)
** Family Hathliacynidae
*** Genus '' Acyon''
****''Acyon ?herrerae'' (early 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 ...
, Colhuehuapian SALMA)
****''Acyon myctoderos'' (late 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 ...
, Laventan SALMA)
****''Acyon tricuspidatus'' (late early 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 ...
, Santacrucian SALMA)
*** Genus '' Australogale''
****''Australogale leptognathus'' (late 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 ...
, Laventan SALMA)
*** Genus '' Borhyaenidium''
****''Borhyaenidium altiplanicus'' (latest 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 ...
, Huayquerian SALMA)
****''Borhyaenidium riggsi'' (unknown, either early or late Pliocene
The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Montehermosan
The Montehermosan age is a period of geologic time (6.8–4.0 Mya (unit), Ma) within the Miocene and Pliocene epochs of the Neogene used more specifically with South American Land Mammal Ages. It follows the Huayquerian and precedes the Chapadmalal ...
or Chapadmalalan
The Chapadmalalan age is a period of geologic time (4.0–3.0 Ma) within the Pliocene epoch of the Neogene used more specifically with South American Land Mammal Ages. It follows the Montehermosan and precedes the Uquian age.
Fossil content
...
SALMA)
****''Borhyaenidium musteloides'' (latest 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 ...
, Huayquerian SALMA)
*** Genus '' Chasicostylus''
****''Chasicostylus castroi'' (early late 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 ...
, Chasicoan SALMA)
*** Genus '' Cladosictis''
****''Cladosictis centralis'' (early 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 ...
, Colhuehuapian SALMA)
****''Cladosictis patagonica'' (late early to earliest 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 ...
, Santacrucian- Friasian SALMA)
*** Genus '' Notictis''
****''Notictis ortizi'' (latest 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 ...
, Huayquerian SALMA)
*** Genus '' Notocynus''
****''Notocynus hermosicus'' (early Pliocene
The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Montehermosan
The Montehermosan age is a period of geologic time (6.8–4.0 Mya (unit), Ma) within the Miocene and Pliocene epochs of the Neogene used more specifically with South American Land Mammal Ages. It follows the Huayquerian and precedes the Chapadmalal ...
SALMA)
*** Genus '' Notogale''
****''Notogale mitis'' (late Oligocene
The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
, Deseadan SALMA)
*** Genus '' Pseudonotictis''
****''Pseudonotictis chubutensis'' (early 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 ...
, Colloncuran SALMA)
****''Pseudonotictis pusillus'' (late early 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 ...
, Santacrucian SALMA)
*** Genus '' Perathereutes''
****''Perathereutes pungens'' (late early 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 ...
, Santacrucian SALMA)
*** Genus '' Sallacyon''
****''Sallacyon hoffstetteri'' (late Oligocene
The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
, Deseadan SALMA)
*** Genus '' Sipalocyon''
****''Sipalocyon externus'' (early 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 ...
, Colhuehuapian SALMA)
****''Sipalocyon gracilis'' (late early 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 ...
, Santacrucian SALMA)
****''Sipalocyon "obusta"'' (late early 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 ...
, Santacrucian SALMA)
** Superfamily Borhyaenoidea
*** Genus '' Angelocabrerus''
****''Angelocabrerus daptes'' (middle 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 ...
)
*** Genus '' Chlorocyon''
****''Chlorocyon phantasma'' (late 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 ...
, Mustersan SALMA)
*** Genus '' Dukecynus''
****''Dukecynus magnus'' (late 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 ...
, Laventan SALMA)
*** Genus '' Eomakhaira''
****''Eomakhaira molossus'' (early Oligocene
The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
, ? Tinguirirican SALMA)
*** Genus '' Fredszalaya''
****''Fredszalaya hunteri'' (late Oligocene
The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
, Deseadan SALMA)
*** Genus '' Lycopsis''
****''Lycopsis longirostrus'' (late 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 ...
, Laventan SALMA)
****''Lycopsis padillai'' (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 ...
, Colloncuran SALMA)
****''Lycopsis torresi'' (early 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 ...
, Colhuehuapian SALMA)
****''Lycopsis viverensis'' (early late 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 ...
, Chasicoan SALMA))
*** Genus '' Pharsophorus''
****''Pharsophorus lacerans'' (middle to late Oligocene
The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
, La Cantera Local Fauna to Deseadan SALMA)
****''Pharsophorus tenax'' (late Oligocene
The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
, Deseadan SALMA)
*** Genus '' Plesiofelis''
****''Plesiofelis schlosseri'' (late 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 ...
, Mustersan SALMA)
*** Genus '' Prothylacynus''
****''Prothylacynus patagonicus'' (late early to earliest 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 ...
, Santacrucian- Friasian SALMA)
*** Genus '' Pseudolycopsis''
****''Pseudolycopsis cabrerai'' (early late 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 ...
, Chasicoan SALMA
*** Genus '' Pseudothylacynus''
****''Pseudothylacynus rectus'' (early 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 ...
, Colhuehuapian SALMA)
*** Family Borhyaenidae
**** Genus '' Acrocyon''
*****''Acrocyon riggsi'' (early 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 ...
, Colhuehuapian SALMA)
*****''Acrocyon sectorius'' (late early 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 ...
, Santacrucian SALMA)
**** Genus '' Arctodictis''
*****''Arctodictis munizi'' (late early 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 ...
, Santacrucian SALMA)
*****''Arctodictis sinclairi'' (early 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 ...
, Colhuehuapian SALMA)
**** Genus '' Australohyaena''
*****''Australohyaena antiquua'' (late Oligocene
The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
, Deseadan SALMA)
**** Genus '' Borhyaena''
*****''Borhyaena macrodonta'' (early 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 ...
, Colhuehuapian SALMA)
*****''Borhyaena tuberata'' (late early 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 ...
, Santacrucian SALMA)
**** ?Genus '' Eutemnodus''
*** Family Proborhyaenidae
Proborhyaenidae is an extinct Family (biology), family of metatherian mammals of the order Sparassodonta, which lived in South America from the Eocene (Mustersan) until the Oligocene (Deseadan). Sometimes it has been included as a subfamily of th ...
**** Genus '' Arminiheringia''
**** Genus '' Callistoe''
*****''Callistoe vincei'' (middle 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 ...
, Vacan- Barrancan SALMA)
**** Genus '' Paraborhyaena''
*****''Paraborhyaena boliviana'' (late Oligocene
The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
, Deseadan SALMA)
**** Genus '' Proborhyaena''
*****''Proborhyaena gigantea'' (late Oligocene
The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
, Deseadan SALMA)
***Unranked clade Thylacosmiliformes
**** Genus '' Dimartinia''
*****''Dimartinia pristina'' (late 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 ...
, Chasicoan SALMA)
**** Family Thylacosmilidae
***** Genus '' Anachlysictis''
******''Anachlysictis gracilis'' (late 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 ...
, Laventan SALMA)
***** Genus '' Patagosmilus''
******''Patagosmilus goini'' (early 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 ...
, Colloncuran SALMA)
***** Genus '' Thylacosmilus''
******''Thylacosmilus atrox'' (latest 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 ...
to late Pliocene
The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Huayquerian-
The early history of the Sparassodonta is poorly known, as most
Sparassodonts were carnivorous, and with the exception of some basal members of all members of this group were hypercarnivorous (having diets composed of more than 70% meat). Only ''Hondadelphys'' and ''Stylocynus'' appear to have exhibited adaptations for omnivory, and even then ''Stylocynus'' may have had a more mesocarnivorous diet similar to canids than an omnivorous one. Medium-to-large caviomorph rodents and rodent-like mammals (e.g., small notoungulates) appear to have been common prey items of sparassodonts. The subadult holotype of '' Lycopsis longirostrus'' preserves remains of the dinomyid ''Scleromys colombianus'' as fossilized gut contents. Sparassodont coprolites from the Santa Cruz Formation preserve the bones of chinchillid and octodontoid rodents inside them. Bite marks from medium-sized sparassodonts have been found on the small notoungulate '' Paedotherium''. Stable isotope data from the early late Miocene '' Lycopsis viverensis'' and '' Thylacosmilus atrox'' suggests that these species fed on C3 grazers in open habitats, likely notoungulates.
Bite marks likely pertaining to hathliacynid sparassodonts have been found on the remains of penguins and flightless marine ducks in ancient seabird nesting colonies, suggesting that sparassodonts raided seabird colonies for eggs, carrion, and other prey like many predatory mammals do today.
Borhyaenid and proborhyaenid sparassodonts have been interpreted as being capable of crushing bones similar to modern hyenas, wolverines, or the Tasmanian devil (''Sarcophilus harrisii'') based on their deep jaws, bulbous premolars with deep roots and pronounced wear at their tips, extensive fused or interlocking mandibular symphyses, large masseteric fossae, microfractures in their tooth enamel, and high estimated bite forces. ''Australohyaena antiquua'' shows particularly pronounced adaptations for bone-cracking, with a very deep jaw and strongly arched nasals similar to what is seen in modern
Chapadmalalan
The Chapadmalalan age is a period of geologic time (4.0–3.0 Ma) within the Pliocene epoch of the Neogene used more specifically with South American Land Mammal Ages. It follows the Montehermosan and precedes the Uquian age.
Fossil content
...
SALMA)
Several other metatherian taxa have been suggested to be sparassodonts or closely related to sparassodonts. The australian Murgon taxa '' Archaeonothos'' has been noted as being similar to sparassodonts, but currently its relationships are not fully concluded. Carneiro (2018) recovered the genus '' Varalphadon'' from the Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...
of North America as a basal member of Sparassodonta. However, this interpretation of ''Varalphadon'' as a sparassodont has not been supported by later phylogenetic analyses, and most of the purported synapomorphies between ''Varalphadon'' and sparassodonts are not actually present in ''Varalphadon'' or have been suggested to be due to convergent evolution. Sparassodonts have sometimes been considered closely related to the " Gurlin Tsav skull" an unnamed metatherian known from a partial skull found in the Late Cretaceous Nemegt Formation of Mongolia.
The following cladogram
A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...
of sparassodont interrelationships is after Engelman ''et al.'', 2020. Not all studies agree on the sister group
In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree.
Definition
The expression is most easily illustrated by a cladogram:
Taxon A and ...
relationship between Thylacosmilidae and Borhyaenidae recovered here, with other studies finding thylacosmilids to be within Proborhyaenidae
Proborhyaenidae is an extinct Family (biology), family of metatherian mammals of the order Sparassodonta, which lived in South America from the Eocene (Mustersan) until the Oligocene (Deseadan). Sometimes it has been included as a subfamily of th ...
. The relationships among hathliacynids are also relatively unstable.
Within Metatheria
Metatheria is a mammalian clade that includes all mammals more closely related to marsupials than to placentals. First proposed by Thomas Henry Huxley in 1880, it is a more inclusive group than the marsupials; it contains all marsupials as wel ...
, a 2016 phylogenetic analysis group found that borhyaenids form a clade with the Asian "Gurlin Tsav skull" as well as other South American taxa. The same phylogeny found that marsupials group among various North American Cretaceous species. The phylogenetic tree is reproduced below.
Evolution
The early history of the Sparassodonta is poorly known, as most Paleocene
The Paleocene ( ), or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), ...
and 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 ...
members of this group are only known from isolated teeth and fragmentary jaws. However, one species, the middle 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 ...
''Callistoe vincei'', is known from a nearly complete, articulated skeleton. As ''Callistoe'' belongs to one of the most specialized groups of sparassodonts, this indicates that the other major groups (e.g. borhyaenids, hathliacynids, etc.) must have also arisen by this time. Originally, the early Paleocene metatherian '' Mayulestes'' was considered to be the earliest known member of the Sparassodonta, but phylogenetic analyses suggest that this species represents an independent radiation of carnivorous metatheria
Metatheria is a mammalian clade that includes all mammals more closely related to marsupials than to placentals. First proposed by Thomas Henry Huxley in 1880, it is a more inclusive group than the marsupials; it contains all marsupials as wel ...
ns more closely related to '' Pucadelphys''; however, recent studies show that these taxa were closely related to borhyaenids. As of this writing, the earliest known true sparassodonts are either ''Allqokirus australis'', a species from the same site as ''Mayulestes'' that may turn out to not be a sparassodont, and an isolated astragalus from the earliest Paleocene site of Punta Peligro, Argentina
Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...
.
Sparassodonts have been suggested to be related to a variety of other groups of metatherians. Florentino Ameghino, who first described fossils of the group, thought that sparassodonts were closely related to creodonts and were a transitional group between metatherians and carnivorous placentals (including modern carnivorans
Carnivora ( ) is an Order (biology), order of Placentalia, placental mammals specialized primarily in eating flesh, whose members are formally referred to as carnivorans. The order Carnivora is the sixth largest order of mammals, comprising at ...
). Contemporary authors in the late 19th and early 20th century rejected this hypothesis and considered sparassodonts to be closely related to Australian thylacines and dasyurids. The most popular hypothesis for much of the 20th century was that sparassodonts were closely related to opossums. In 1990, Marshall et al. (1990) considered the Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...
stagodontids to be members of Sparassodonta, but this was criticized by later authors. Marshall and Kielan-Jaworowska (1992) considered sparassodonts to be closely related to deltatheroidans, but this was also criticized. Most of these hypotheses were based on similar adaptations for carnivorous diets in sparassodonts, opossums, dasyuromorphians, stagodonts, and deltatheroidans, which are highly prone to convergent evolution within mammals. Szalay (1994) considered sparassodonts to be closely related to paucituberculatans based on features of the ankle. In recent years there has been a growing consensus that sparassodonts are positioned just outside of crown-group Marsupialia, in a broader clade ( Pucadelphyida) including pucadelphyids as well as sparassodonts.
Sparassodonts are presently regarded as an endemic
Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...
South American group, and have not even been found in nearby continents like Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...
(where other groups native to South America such as litopterns
Litopterna (from "smooth heel") is an extinction, 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 we ...
, astrapotheres, microbiotheres, and polydolopids) are present.
Paleobiology
Diet
Sparassodonts were carnivorous, and with the exception of some basal members of all members of this group were hypercarnivorous (having diets composed of more than 70% meat). Only ''Hondadelphys'' and ''Stylocynus'' appear to have exhibited adaptations for omnivory, and even then ''Stylocynus'' may have had a more mesocarnivorous diet similar to canids than an omnivorous one. Medium-to-large caviomorph rodents and rodent-like mammals (e.g., small notoungulates) appear to have been common prey items of sparassodonts. The subadult holotype of '' Lycopsis longirostrus'' preserves remains of the dinomyid ''Scleromys colombianus'' as fossilized gut contents. Sparassodont coprolites from the Santa Cruz Formation preserve the bones of chinchillid and octodontoid rodents inside them. Bite marks from medium-sized sparassodonts have been found on the small notoungulate '' Paedotherium''. Stable isotope data from the early late Miocene '' Lycopsis viverensis'' and '' Thylacosmilus atrox'' suggests that these species fed on C3 grazers in open habitats, likely notoungulates.
Bite marks likely pertaining to hathliacynid sparassodonts have been found on the remains of penguins and flightless marine ducks in ancient seabird nesting colonies, suggesting that sparassodonts raided seabird colonies for eggs, carrion, and other prey like many predatory mammals do today.
Borhyaenid and proborhyaenid sparassodonts have been interpreted as being capable of crushing bones similar to modern hyenas, wolverines, or the Tasmanian devil (''Sarcophilus harrisii'') based on their deep jaws, bulbous premolars with deep roots and pronounced wear at their tips, extensive fused or interlocking mandibular symphyses, large masseteric fossae, microfractures in their tooth enamel, and high estimated bite forces. ''Australohyaena antiquua'' shows particularly pronounced adaptations for bone-cracking, with a very deep jaw and strongly arched nasals similar to what is seen in modern hyaenids
Hyenas or hyaenas ( ; from Ancient Greek , ) are feliformia, feliform carnivoran mammals belonging to the Family (biology), family Hyaenidae (). With just four extant species (each in its own genus), it is the fifth-smallest family in the orde ...
.
Based on studies of the postcranial skeleton, it appears as though most sparassodonts were scansorial (adapted for climbing), although terrestrial adaptations evolved in '' Lycopsis longirostrus'', borhyaenids, proborhyaenids, and thylacosmilids. Most sparassodonts were plantigrade, ''Borhyaena'' has been suggested to have been digitigrade but this has been questioned. The one exception was '' Thylacosmilus'', which has been interpreted as having a digitigrade forefoot and a semiplantigrade hindfoot, this has been supported by fossil tracks.
One unusual aspect of sparassodont paleoecology is that at most fossil localities their remains are nearly ten times rarer than would be expected based on comparisons with carnivorous mammals at fossil sites in other parts of the world. The exact reasons for this are not clear, though this appears to be a broader pattern applicable to other groups of Cenozoic South American terrestrial carnivores (i.e., terror birds).
Sociality
Little is known of the behavior and biology of sparassodonts outside of general locomotor and dietary habits. Argot (2004) proposed that ''Thylacosmilus atrox'' may have exhibited protracted parental care after weaning of the offspring, given that saber teeth in general have been suggested to require long juvenile periods for the young to gain the skill necessary to use them effectively. However, this has not been tested further. Sparassodonts have relatively large and complex brains for metatherians, comparable to those of some Australian marsupials like Australian possums, though the body masses used to produce these estimates of relative brain size are low compared later studies suggesting these values could be overestimated. Wounds have been documented on the face of specimens of ''Borhyaena tuberata'' and ''Sipalocyon gracilis'', potentially suggesting aggressive habits similar to the modern Tasmanian devil (''Sarcophilus harrisii'').Senses
Sparassodonts appear to have had very little binocular vision, with borhyaenids having the greatest degree of depth perception (but still lower than modern carnivorans) and the eyes of '' Thylacosmilus'' facing almost completely to the sides. However, later studies have found that ''Thylacosmilus'' likely held its head in a downward-facing position, which would have allowed for more binocular vision than previously thought.Pathology
Several specimens of hathliacynids (''Sipalocyon'' and ''Cladosictis'') show a pathological disorder characterized by the presence of growths on the surface of the mandible, which in the most extreme cases can result in the loss of several teeth due to bony pathological growths. The exact cause of this condition (i.e., infection, virus, parasite) and why it seems to only occur in small sparassodonts is unknown, though this condition has also been documented in microbiotherians.Extinction
After the middle Miocene, sparassodonts began to slowly decline in diversity. Basal borhyaenoids are last known from the early late Miocene (''Pseudolycopsis cabrerai'' and ''Lycopsis viverensis''), and after this time were at least partially replaced by large-bodied basal sparassodonts such as ''Stylocynus''. Some have proposed that this shift in dominance was because of the more omnivorous habits of basal sparassodonts, which may have been more adapted to the more seasonal South American climates of the lateNeogene
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 ...
. Borhyaenids are last known from the latest 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 ...
, though only fragmentary remains of this group are known from this period. Later remains assigned to this group have since been reidentified as thylacosmilids or procyonids. By the Pliocene
The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Hathliacynidae and the Thylacosmilidae. Pliocene hathliacynid remains are rare, and it is possible that these animals may have competed with the large carnivorous didelphids such as '' Lutreolina'' that appeared around this time. Hathliacynids are last definitively known from the early Pliocene, though their remains are rare.
The thylacosmilids, on the other hand, were more successful and abundant, being some of the only large mammalian carnivores in South America during the Pliocene, before dying out during a faunal turnover in the middle of the epoch (the youngest specimens of thylacosmilids are ~3.3 Ma). It is still not certain why Sparassodonta declined in diversity and became extinct during the late Cenozoic, but it appears as though competition from eutherian
carnivorans
Carnivora ( ) is an Order (biology), order of Placentalia, placental mammals specialized primarily in eating flesh, whose members are formally referred to as carnivorans. The order Carnivora is the sixth largest order of mammals, comprising at ...
was not a factor, as the placental analogues of sparassodonts ( dogs, weasels, and saber-toothed cats) did not enter South America until the middle Pleistocene, several million years after their sparassodont counterparts became extinct. Sparassodonts did coexist with '' Cyonasua''-group procyonids during the late Miocene and Pliocene, but '' Cyonasua''-group procyonids appear to have been primarily omnivorous and filled ecological niches that sparassodonts never occupied, which may be one reason that these animals were able to colonize South America despite the diverse predator guild in the late Miocene. The overall decline in sparassodont diversity from the Late Miocene to the end of the Pliocene may be linked to the climatic cooling that characterised the Late Neogene and the onset of the Quaternary glaciation
The Quaternary glaciation, also known as the Pleistocene glaciation, is an alternating series of glacial period, glacial and interglacial, interglacial periods during the Quaternary period that began 2.58 Year#SI prefix multipliers, Ma (million ...
. Additionally, the increased aridity of South America caused by the uplift of the Andes was likely responsible as well.
References
Further reading
* *External links
{{Taxonbar, from=Q133041 Prehistoric metatherians Sparassodonta Cenozoic mammals of South America Paleocene first appearances Pliocene extinctions Fossil taxa described in 1894