Volaticotherini is a
clade of
eutriconodont
Eutriconodonta is an order of early mammals. Eutriconodonts existed in Asia, Africa, Europe, North and South America during the Jurassic and the Cretaceous periods. The order was named by Kermack ''et al.'' in 1973 as a replacement name for the p ...
mammals from the
Mesozoic
The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretace ...
. In addition to the
type genus
In biological taxonomy, the type genus is the genus which defines a biological family and the root of the family name.
Zoological nomenclature
According to the International Code of Zoological Nomenclature, "The name-bearing type of a nominal ...
''
Volaticotherium
''Volaticotherium antiquum'' (meaning "ancient gliding beast") is an extinct, gliding, insectivorous mammal that lived in Asia during the Jurassic period, around 164 mya. It is the only member of the genus ''Volaticotherium''.
The discovery of ...
'', it includes the genera ''
Argentoconodon'', ''
Ichthyoconodon
''Ichthyoconodon'' is an extinct genus of eutriconodont mammal from the Lower Cretaceous of Morocco. It is notable for having been found in a unique marine location, and the shape of its teeth suggests an unusual, potentially fish-eating ecologi ...
'', and potentially ''
Triconolestes''.
Since most remains are primarily teeth, they are foremostly diagnosticated by their highly distinctive
molars
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 to ...
. However, the remains of one species, ''
Volaticotherium antiquum'', show that at least some members of this clade were capable of
gliding.
[ and '' Argentoconodon'' shares similar post-cranial features that also indicate aerial locomotion. As such, this clade contains some of the oldest known aerial mammals, alongside the various gliding haramiyidans.
]
Definition
Volaticotherini is phylogenetically defined as the clade derived from the most recent common ancestor of ''Argentoconodon'', ''Ichthyoconodon,'' and ''Volaticotherium''.[
]
History
''Ichthyoconodon
''Ichthyoconodon'' is an extinct genus of eutriconodont mammal from the Lower Cretaceous of Morocco. It is notable for having been found in a unique marine location, and the shape of its teeth suggests an unusual, potentially fish-eating ecologi ...
'' was the first described member of this group, back in 1995, previously usually ranked among eutriconodont
Eutriconodonta is an order of early mammals. Eutriconodonts existed in Asia, Africa, Europe, North and South America during the Jurassic and the Cretaceous periods. The order was named by Kermack ''et al.'' in 1973 as a replacement name for the p ...
s, albeit tentatively due to its atypical teeth. ''Volaticotherium
''Volaticotherium antiquum'' (meaning "ancient gliding beast") is an extinct, gliding, insectivorous mammal that lived in Asia during the Jurassic period, around 164 mya. It is the only member of the genus ''Volaticotherium''.
The discovery of ...
'', described in 2006, provided a fairly complete skeleton and led to the erection of a distinct family, Volaticotheridae, and order, Volaticotheria, to house the genus, and allowed ''Ichthyoconodon
''Ichthyoconodon'' is an extinct genus of eutriconodont mammal from the Lower Cretaceous of Morocco. It is notable for having been found in a unique marine location, and the shape of its teeth suggests an unusual, potentially fish-eating ecologi ...
'' to be recognized as a potential relative.[ Volaticotheria was considered the sister taxon of a clade comprising ]eutriconodont
Eutriconodonta is an order of early mammals. Eutriconodonts existed in Asia, Africa, Europe, North and South America during the Jurassic and the Cretaceous periods. The order was named by Kermack ''et al.'' in 1973 as a replacement name for the p ...
s, multituberculate
Multituberculata (commonly known as multituberculates, named for the multiple tubercles of their teeth) is an extinct order of rodent-like mammals with a fossil record spanning over 130 million years. They first appeared in the Middle Jurassic, a ...
s, and trechnotheres. However, not long after, an eutriconodont identity was suspected, and Volaticotheria has since fallen into disuse.[
Subsequent analyses have consistently recovered ''Argentoconodon'' as the sister taxon of ''Volaticotherium'', with ''Ichthyoconodon'' as the sister taxon of that clade and thus the basalmost volaticotherin.][ The North American genus '']Jugulator
''Jugulator'' is the thirteenth studio album by English heavy metal band Judas Priest. It was released in Japan on 16 October 1997 and the rest of the world on 28 October 1997. It was their first studio album since ''Painkiller'' in 1990 an ...
'' may be the sister taxon of Volaticotherini. These were moved to the eutriconodont
Eutriconodonta is an order of early mammals. Eutriconodonts existed in Asia, Africa, Europe, North and South America during the Jurassic and the Cretaceous periods. The order was named by Kermack ''et al.'' in 1973 as a replacement name for the p ...
family Triconodontidae
Triconodontidae is an extinct family of small, carnivorous mammals belonging to the order Eutriconodonta, endemic to what would become Asia, Europe, North America and probably also Africa and South America during the Jurassic through Cretaceous p ...
, as part of the alticonodontine assemblage, and the clade was renamed Volaticotherini accordingly.[ However, other sources consider the clade to be a separate family from Triconodontidae, as Volaticotheridae.][ This may be supported by other, more recent analyses, which find the clade to be more basally placed within Eutriconodonta.][
]
Characteristics
Since most volaticotherian remains are based on teeth, the diagnostic characteristic of the group is its molar morphology. Though classified as "triconodont" in shape, volaticotherian molars are highly atypical, possessing high, curved, backwards facing cusp
A cusp is the most pointed end of a curve. It often refers to cusp (anatomy), a pointed structure on a tooth.
Cusp or CUSP may also refer to:
Mathematics
* Cusp (singularity), a singular point of a curve
* Cusp catastrophe, a branch of bifurc ...
s aligned anteroposteriorly, lacking a cingulum.[ Canines and incisors tend to be fairly large.
In the two forms that do possess postcranial remains, '' Argentoconodon'' and '']Volaticotherium
''Volaticotherium antiquum'' (meaning "ancient gliding beast") is an extinct, gliding, insectivorous mammal that lived in Asia during the Jurassic period, around 164 mya. It is the only member of the genus ''Volaticotherium''.
The discovery of ...
'', we see a highly specialised femur
The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates wit ...
, lacking a femoral neck.[
'']Volaticotherium
''Volaticotherium antiquum'' (meaning "ancient gliding beast") is an extinct, gliding, insectivorous mammal that lived in Asia during the Jurassic period, around 164 mya. It is the only member of the genus ''Volaticotherium''.
The discovery of ...
'' is rather well preserved, bearing a mostly complete skeleton and soft-tissue impressions such as hair and patagia
The patagium (plural: patagia) is a membranous body part that assists an animal in obtaining lift when gliding or flight. The structure is found in extant and extinct groups of flying and gliding animals including bats, birds, some dromaeosau ...
.
Aerial locomotion
One genus of volaticotherin, ''Volaticotherium'', has clear evidence of being capable of gliding. It was the first gliding Mesozoic mammal discovered and lived at least 70 million years before the appearance of the first flying and gliding theria
Theria (; Greek: , wild beast) is a subclass of mammals amongst the Theriiformes. Theria includes the eutherians (including the placental mammals) and the metatherians (including the marsupials) but excludes the egg-laying monotremes.
...
ns.[ It preserved a large, ]fur
Fur is a thick growth of hair that covers the skin of mammals. It consists of a combination of oily guard hair on top and thick underfur beneath. The guard hair keeps moisture from reaching the skin; the underfur acts as an insulating blanket t ...
-covered patagium, extending not only between the limbs and tail, but also to the digits, "sandwiching" them. The limbs were proportionally longer than those of other Mesozoic mammals, fitting the standards in flying and gliding mammals, and the femur is uniquely specialised, allowing the leg to be extended laterally and remain steady during gliding. The tail is dorsoventrally flattened, and supports evidence of uropatagia in at least the proximal vertebrae.[ '' Argentoconodon'' shares similar femur characteristics, suggesting that it too may have been capable of gliding.][
]
Distribution
Volaticotherini was a relatively widespread and long-lived clade, with occurrences known from the Toarcian
The Toarcian is, in the ICS' geologic timescale, an age and stage in the Early or Lower Jurassic. It spans the time between 182.7 Ma (million years ago) and 174.1 Ma. It follows the Pliensbachian and is followed by the Aalenian.
The Toarcian ...
of South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sout ...
, Oxfordian of China, and Berriasian
In the geological timescale, the Berriasian is an age/stage of the Early/Lower Cretaceous. It is the oldest subdivision in the entire Cretaceous. It has been taken to span the time between 145.0 ± 4.0 Ma and 139.8 ± 3.0 Ma (million years ago ...
of Morocco
Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria t ...
. The presence of volaticotherins in Gondwana is unusual, as they are among the few known Gondwanan triconodonts (and, if aligned with triconodontids, the only representatives of the group in Gondwanna), with '' Argentoconodon'' occurring as far back as the Early Jurassic
The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-J ...
in otherwise australosphenida
The Australosphenida are a clade of mammals, containing mammals with tribosphenic molars, known from the Jurassic to Mid-Cretaceous of Gondwana. They are thought to have acquired their tribosphenic molars independently from those of Tribosphenid ...
n dominated faunas.[
]
Diet
Though highly unusual and possibly indicating atypical occlusion patterns,[ volaticotherian molars are thought to have had a shearing motion as in other eutriconodonts.][ Combined with long canines, this seems to indicate that, like their relatives, they were probably carnivorous. '']Ichthyoconodon
''Ichthyoconodon'' is an extinct genus of eutriconodont mammal from the Lower Cretaceous of Morocco. It is notable for having been found in a unique marine location, and the shape of its teeth suggests an unusual, potentially fish-eating ecologi ...
'' was fairly large by Mesozoic mammal standards, and were probably capable of tackling vertebrate prey.[ In a study about Mesozoic mammal diets '' Argentoconodon'' ranks among carnivorous species, while '']Volaticotherium
''Volaticotherium antiquum'' (meaning "ancient gliding beast") is an extinct, gliding, insectivorous mammal that lived in Asia during the Jurassic period, around 164 mya. It is the only member of the genus ''Volaticotherium''.
The discovery of ...
'' ranks among insectivorous taxa. This same result is provided almost identically in a posterior study, albeit with ''Volaticotherium'' closer to the carnivore space.
It has been noted that most gliding mammals are predominantly herbivorous, which would make volaticothere carnivory truly exceptional. In particular, ''Volaticotherium'' itself has been compared to insectivore bats
Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most bir ...
.[
]
Paleoecology
Volaticotherins, as is typical for gliding animals, were adapted for an arboreal lifestyle.[ One volaticotherin, ''Ichthyoconodon'', was recovered from marine facies and consequently initially interpreted as an aquatic animal.][ However, many terrestrial mammals are preserved in aquatic environments, so it is unclear how strong this evidence is regarding its life habits,][ though its teeth appear to not have undergone long aquatic transportation.][
]
References
{{Taxonbar, from=Q21447982
Eutriconodonts
Gliding animals
Fossil taxa described in 2006
Jurassic first appearances
Early Cretaceous extinctions
Taxa named by Jin Meng
Taxa named by Yaoming Hu
Taxa named by Yuanqing Wang
Taxa named by Xiaolin Wang (paleontologist)
Taxa named by Chuankui Li