Traversodontidae is an
extinct
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually 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 ...
family
Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
of
herbivorous
A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...
cynodont
The cynodonts () (clade Cynodontia) are a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 mya), and extensively diversified after the Permian–Triassic extinction event. Cynodonts had a wide variety ...
s. Traversodonts were primarily
Gondwana
Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...
n, with many species known from
Africa
Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
and
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 southe ...
. Recently, traversodonts have also been found from
Europe
Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
and eastern
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
. Traversodonts first appeared in the
Middle Triassic
In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided in chronostratigraphy. The Middle Triassic spans the time between Ma and ...
and diversified in the
Late Triassic
The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch ...
before going extinct at the end of the epoch. The family Traversodontidae was erected by
Friedrich von Huene
Friedrich von Huene, born Friedrich Richard von Hoinigen, (March 22, 1875 – April 4, 1969) was a German paleontologist who renamed more dinosaurs in the early 20th century than anyone else in Europe. He also made key contributions about v ...
in 1936 for cynodonts first found in
São Pedro do Sul in Paleorrota,
Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
.
Description
![Dadadon FMNH](https://upload.wikimedia.org/wikipedia/commons/3/38/Dadadon_FMNH.jpg)
Traversodonts are members of
Gomphodontia
Gomphodontia is a clade of cynognathian cynodonts that includes the families Diademodontidae, Trirachodontidae, and Traversodontidae. Gomphodonts are distinguished by wide and closely spaced molar-like postcanine teeth, which are convergent wit ...
, a group of herbivorous
cynognathia
Cynognathia ("dog jaw") is one of two major clades of cynodonts, the other being Probainognathia. Cynognathians included the large carnivorous genus '' Cynognathus'' and the herbivorous traversodontids. Cynognathians can be identified by several ...
n cynodonts. As an adaptation toward eating plants, they have wide
postcanine
Cheek teeth or post-canines comprise the molar and premolar teeth in mammals. Cheek teeth are multicuspidate (having many folds or tubercles). Mammals have multicuspidate molars (three in placentals, four in marsupials, in each jaw quadrant) and ...
teeth behind large
canines. These postcanines are closely spaced with their crowns touching each other. Each is usually wider than it is long and is covered in several cusps. Because of their complexity, postcanine teeth are the primary means of identifying and distinguishing different species of traversodonts.
Traversodonts have relatively short skulls. The snout is much narrower than the back of the skull. The tip of the snout is wider than the middle, as it constricts behind the large canines. The tooth rows of the upper jaws are inset while the
maxillae
The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...
and
zygomatic arch
In anatomy, the zygomatic arch, or cheek bone, is a part of the skull formed by the zygomatic process of the temporal bone (a bone extending forward from the side of the skull, over the opening of the ear) and the temporal process of the zygomati ...
es extend outward, suggesting that traversodonts may have had cheeks. Primitive features of traversodonts include costal plates around the vertebrae, which stabilize the spine. These plates were lost in more advanced traversodonts like ''
Exaeretodon
''Exaeretodon'' is an extinct genus of fairly large, low-slung traversodontid cynodonts from the southern parts of Pangea. Four species are known, from various formations. ''E. argentinus'' is from the Carnian-age (Late Triassic) Cancha de Boch ...
''.
Phylogeny
Traversodontidae belongs to a large clade of cynodonts called
Cynognathia
Cynognathia ("dog jaw") is one of two major clades of cynodonts, the other being Probainognathia. Cynognathians included the large carnivorous genus '' Cynognathus'' and the herbivorous traversodontids. Cynognathians can be identified by several ...
. Most
phylogenetic
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
analyses place it as the
sister taxon
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 t ...
to the family
Trirachodontidae
Trirachodontidae is an extinct, possibly paraphyletic family of cynognathian cynodonts from the Triassic of China and southern Africa. Trirachodontids appeared during the Early Triassic soon after the Permian-Triassic extinction event and quick ...
, and both groups are placed in the cynognathian clade
Gomphodontia
Gomphodontia is a clade of cynognathian cynodonts that includes the families Diademodontidae, Trirachodontidae, and Traversodontidae. Gomphodonts are distinguished by wide and closely spaced molar-like postcanine teeth, which are convergent wit ...
. The analysis of Kammerer ''et al.'' (2012) found strong support for two clades within Traversodontidae: the subfamily
Gomphodontosuchinae, which had been identified in 2008, and the newly named subfamily
Massetognathinae. Below is a
cladogram
A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...
from that analysis:
Paleobiology
While most traversodonts were relatively large cynodonts, particularly Scalenodontoides with extrapolated 60cm skull making it potentially the largest nonmammalian cynodont,
some Late Triassic European forms like ''
Maubeugia
''Maubeugia'' is an extinct genus of traversodontid cynodonts from the Late Triassic of France. Isolated postcanine teeth are known from Saint-Nicolas-de-Port
Saint-Nicolas-de-Port () is a commune in the Meurthe-et-Moselle ''département'' ...
'' and ''
Habayia'' were very small. These traversodonts lived during the
Rhaetian
The Rhaetian is the latest age of the Triassic Period (in geochronology) or the uppermost stage of the Triassic System (in chronostratigraphy). It was preceded by the Norian and succeeded by the Hettangian (the lowermost stage or earliest age ...
stage of the latest Triassic when
rising sea levels
Rising may refer to:
* Rising, a stage in baking - see Proofing (baking technique)
*Elevation
* Short for Uprising, a rebellion
Film and TV
* "Rising" (''Stargate Atlantis''), the series premiere of the science fiction television program ''Starga ...
divided western Europe into an island
archipelago
An archipelago ( ), sometimes called an island group or island chain, is a chain, cluster, or collection of islands, or sometimes a sea containing a small number of scattered islands.
Examples of archipelagos include: the Indonesian Archi ...
. Traversodontids on these islands likely became smaller as a result of
insular dwarfism
Insular dwarfism, a form of phyletic dwarfism, is the process and condition of large animals evolving or having a reduced body size when their population's range is limited to a small environment, primarily islands. This natural process is disti ...
.
See also
*
Evolution of mammals
The evolution of mammals has passed through many stages since the first appearance of their synapsid ancestors in the Pennsylvanian sub-period of the late Carboniferous period. By the mid-Triassic, there were many synapsid species that looked l ...
References
* Much of this information comes fro
Traversodontidae
{{Taxonbar, from=Q972010
Middle Triassic first appearances
Late Triassic extinctions
Prehistoric therapsid families