Kannemeyeriiformes is a group of large-bodied

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

dicynodont Dicynodontia is an extinct clade of anomodonts, an extinct type of non-mammalian therapsid. Dicynodonts were herbivores that typically bore a pair of tusks, hence their name, which means 'two dog tooth'. Members of the group possessed a horny, t ...

s. As a

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

, Kannemeyeriiformes has been defined to include the species '' Kannemeyeria simocephalus'' and all dicynodonts more closely related to it than to the species '' Lystrosaurus murrayi''.

Evolutionary history

Despite being the most species-rich group of dicynodonts in the Triassic Period, kannemeyeriiforms exhibit much less diversity in terms of their anatomy and ecological roles than the dicynodonts from the

Permian Period The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...

. Lystrosauridae is thought to be the most closely related group (

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 ...

) to Kannemeyeriiformes, and since the earliest lystrosaurids are known from the

Late Permian Late or LATE may refer to: Everyday usage * Tardy, or late, not being on time * Late (or the late) may refer to a person who is dead Music * ''Late'' (The 77s album), 2000 * Late (Alvin Batiste album), 1993 * Late!, a pseudonym used by Dave Groh ...

, the divergence of these two groups must have occurred at least as far back as this time, implying that a long ghost lineage must exist. Although no kannemeyeriiforms have been found in the Late Permian yet, the recent discovery of '' Sungeodon'' helps fill a gap in the early fossil record of the group by showing that kannemeyeriiforms diversified right after the Permian-Triassic extinction event.

Classification

Four families have been included in the group: Kannemeyeriidae, Shansiodontidae, Stahleckeriidae, and Dinodontosauridae. Occasionally some of these families are not recognized, with most kannemeyeriiforms being placed in Kannemeyeriidae. Recent

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

analyses suggest that these families represent similar body plans or morphotypes rather than true evolutionary groupings.

Phylogeny

Below is a

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 ...

from Szczygielski & Sulej (2023):

References

Triassic synapsids Induan first appearances Rhaetian extinctions Taxa named by Friedrich von Huene {{anomodont-stub