User:DrawingDinosaurs/sandbox

Kannemeyeriidae is an extinct family of dicynodonts, a group of beaked therapsids distantly related to modern mammals, including the eponymous and well known genus Kannemeyeria. Kannemeyeriids are one of three families of large dicynodonts from the Triassic period, alongside the shansiodontids and stahleckeriids. They were medium to large-sized herbivores and had a near cosmopolitan distribution with their fossils discovered in Africa, India, Europe, Asia, South America, and potentially even Antarctica. Although they were geographically widespread across the supercontinent Pangaea, all definitively dated kannemeyeriids are known only from the Middle Triassic—although the South American Acratophorus and Kannemyeria aganosteus may date to the Carnian of the Late Triassic.

Historically, palaeontologists included all of the large Triassic dicynodonts within the single family Kannemeyeriidae—equivalent to the modern use of the clade Kannemeyeriiformes today (i.e. it also included shansiodontids and stahleckeriids). Kannemeyeriidae has since been restricted to a smaller assemblage of dicynodonts more closely related to and resembling Kannemeyeria itself, although there has been debate over what genera are included and how they are related to other kannemeyeriiform subgroups. Notably, some members of Kannemeyeriidae as it is understood today have been assigned to other distinct kannemeyeriiform subgroups in the past, most notably the proposed tribe or subfamily Sinokannemeyeriini/-inae. The composition, phylogeny and taxonomy of such subgroups has been variable and inconsistent between studies, and consequently they are are not incorporated by modern kannemeyeriid systematics.

Although historically used as an important biological family by dicynodont taxonomists, modern methods of studying dicynodont evolutionary relationships (namely cladistics) have disagreed over the monophyly or paraphyly of kannemeyeriids, and consequently questioned its taxonomic validity. If kannemeyeriids are monophyletic, they form a clade in which its members are more closely related to each other than to other kannemeyeriiforms and share a unique common ancestor distinct from other groups. Alternatively, "kannemeyeriids" may instead be an evolutionary grade of individual species branching off between other clades of Triassic dicynodonts, i.e. they would be paraphyletic. The monophyly or paraphyly of Kannemeyeriidae, and so the group's validity, remains an unresolved issue in modern dicynodont research due to uncertainties over the internal relationships between individual kannemeyeriids and their evolutionary relationship to other kannemeyeriiforms, both of which are unstable between every analysis.

History of study
The first kannemeyeriid fossils were discovered in the late 19th century, namely a partial skull from South Africa that would become the type specimen of Kannemeyeria simocephalus, first named in 1888 by German palaeontologist Anton Weithofer as Dicynodon simocephalus. Kannemeyeriidae as a biological family, however, was not recognised for a further sixty years until it was coined in 1948 by another German palaeontologist, Friedrich von Huene. Huene named Kannemeyeriidae to distinguish Kannemeyeria and similar large Triassic dicynodonts that had been discovered since then from both older Permian dicynodonts and the unusual Early Triassic dicynodont Lystrosaurus. From the limited specimens of Triassic dicynodonts known at the time, Huene characterised kannemeyeriids as having a high, narrow sagittal crest, nasal bones longer than their frontal bones (i.e. a snout longer than the orbital region), a high number of sacral ribs in their hips (up to eight), and a well-developed olecranon process on the ulna in their elbow.

Subsequently, all large Triassic dicynodonts were classified under Kannemeyeriidae and by the 1960s as more species were being discovered researchers began to divide them into subgroups. In 1965 palaeontologist Christopher Barry Cox went further and split the traditional Kannemeyeriidae into three separate families, restricting Kannemeyeriidae to Kannemeyeria and its closest relatives while splitting the others into the new families Shansiodontidae and Stahleckeriidae. Cox's more exclusive concept of Kannemeyeriidae was defined by possessing narrow snouts, long temporal fenestra, a tall sagittal crest and tall, slanting occiputs (the face of the skull that attaches to the neck). Notably though, this method of using superficial physical proportions to define Kannemeyeriidae meant he incorrectly included several genera now recognised to be stahleckeriids (such as Placerias and Ischigualastia) in Kannemeyeriidae and vice versa.

Although such subdivision of traditional kannemeyeriids was broadly accepted, not all researchers agreed they warranted seperate families and preferred to maintain them as subgroups of the traditional, singular Kannemeyeriidae—such as Keyser and Cruickshank in 1979. Computerised cladistics were used to test the phylogenetic relationships of kannameyeriids for the first time in 2001 by Michael W. Maisch. His analysis recognised various distinct groupings and like Cox he regarded these as distinct families (including a much reduced Kannemeyeriidae). Maisch coined Kannemeyeriiformes for the clade representing the previous traditional concept of Kannemeyeriidae. Kannemeyeriids have thus remained a more restricted group by most researchers since then, although the status of the group cladistically has come under scrutiny and some analyses fail to recover its core members as a clade at all. As such, the family name is sometimes only used informally by researchers for an assemblage of non-shanshiodontid, non-stahleckeriid kannemeyeriiforms (such as in Kammerer, 2013).

Fossil record
As kannemeyeriids are currently recognised, their fossils have been discovered on almost every continent, absent only from Australia, western Europe and North America. Kannemeyeriid fossils were first discovered in South Africa with Kannemeyeria itself in 1888, followed by China in 1937 (Sinokannemeyeria), European Russia in 1951 (Rhadiodromus), and then India in 1970 (Rechnisaurus and Wadiasaurus). Most other kannemeyeriids have likewise been discovered in China, Russia, and southern Africa including (Tanzania, Namibia, and Zambia). Kannemeyeriids may also have been present in Antarctica, based on a partial skull described in 2020 that may belong to the first identifiable Antarctic kannemeyeriid, as might isolated tusks from the same rock layers.

The record of kannemeyeriids in South America has had a more complicated history. In 1966, fossils of a purported kannemeyeriid from Argentina were originally referred to a new species of Kannemeyeria, K. argentinensis. However, its affinity to Kannemeyeria was questioned by some researchers, and the species was sometimes referred to the Argentinian shansiodontid Vinceria instead, eliminating any records of kannemeyeriids from South America's fossil record. However, re-evaluation of the fossils in 2021 by Christian Kammerer and Maria de los Angeles Ordoñez re-affirmed its affinities to kannemeyeriids, albeit as a new genus which they named Acratophorus. At the same time, they recognised and named newly described material from Argentina as genuine species of Argentinian Kannemeyeria, K. aganosteus, restoring the presence of both kannemeyeriids and Kannemeyeria itself in South America.

Description
Kannemeyeriids were mid-to-large sized dicynodonts, with skulls ranging between ~20 - 45 cm in length. Like other derived bidentalian dicynodonts, they were stocky quadrupeds with beaked jaws and no teeth except for a pair of tusks in most forms. Kannemeyeriids have historically been characterised as having relatively long, narrow, and pointed snouts, and tall sagittal crests at the back of the skull relative to other kannemeyeriiforms, as in Kannemeyeria, although this crest is not ubiquitous to all kannemeyeriids (it is very low in Parakannemeyeria and Sinokannemeyeria for example) and similar crests are convergently found in some stahleckeriids (e.g. Placerias). This crest served as an enlarged attachment point for large, powerful jaw muscles. This crest is most extremely developed in the Russian kannemeyeriid Rabidosaurus, in which it is very tall, pointed and triangular, rising well above the rest of the skull.

All known kannemeyeriids had tusks of some degree, which are typically absent in the later stahleckeriids. Tusk size was variable in kannemeyeriids, from very large and well developed in Uralokannemeyeria to small and sometimes even absent in some specimens of Wadiasaurus (a potentially sexually dimorphic trait in this genus). The size and shape of the bony caniniform process (the extended platform of jawbone housing the tusks) is similarly variable, ranging from weakly developed and pointed (e.g. Wadiasaurus) to large, strongly-developed and bulbous (e.g. Sinokannemeyeria). The caniniform processes of some kannemeyeriiforms also sport prominent flanges on their sides, known as the "lateral buttress". In Rechnisaurus, these flanges are so well developed that they almost entirely obscure the tusk in side view.

Kannemeyeriids also often have large bosses of bone on their snouts, like many other dicynodonts. In kannemeyeriids, they form a single large nasal boss, compared to the paired and divided nasal bosses of some Permian dicynodonts and the stahleckeriid Ufudocyclops. The surface texture of these bosses is often rugose, implying that they were covered in keratin like the beak in life. These bosses can be very large and swollen, as in Kannemeyeria lophorhinus and Parakannemeyeria. Some kannemeyeriids, namely the three species of Kannemeyeria, Rechnisaurus and Shaanbeikannemeyeria also sport a long and thin crest of varying length and height running down the middle of their nasal bosses. This crest is especially emphasised in Rechnisaurus by depressions in the snout flanking either side of the crest.

The rest of the kannemeyeriid skeleton is not as distinctive as their skulls, but some potential distinguishing features have been recognised. The shoulder blades (scapula) are generally tall with relatively narrow ends (unlike the flared shoulder blades of most shansiodontids and stahleckeriids), have a relatively small and forward facing acromion (a bony process along the front of the scapula), and long but weakly developed scapular spines (a bony ridge on the face of the s capula for muscule attachment). They have also been noted to typically have relatively broad femurs at their mid-shaft compared to other kannemeyeriiforms. The head of femur is also not offset from the shaft as it is in other kannemeyeriiforms (except for Dinodontosaurus), which may be a potential synapomorphy (a unique shared trait inherited from a common ancestor) of kannemeyeriids.

Diet
Like most dicynodonts, kannemeyeriids were herbivorous, although variations and specialisations in feeding style and diet have been suggested based on the shape of their skulls. In 1965, Cox compared his interpretation of kannemeyeriids with pointed snouts and stahlackeriids with blunt snouts to browsing black and grazing white rhinos, suggesting they respectively had comparable feeding styles and diet. Arthur Cruickshank made differing speculations in the 1970s, contradictingly suggesting that the sloped and narrow occiputs of Kannemeyeria and its kin was an adaptation for lowering their heads to graze on low-lying vegetation, while other Triassic dicynodonts with straighter and broader occiputs were browsers, comparing these features to those found in modern grazing warthogs and browsing bushpigs. {GET REFS}

Notably, both of these hypotheses were based on pre-cladistic ideas of kannemeyeriiform relationships and these functional traits do not neatly correspond to distinct lineages of Triassic dicynodonts. A study of dicynodont head kinematics by Surkov and Benton in 2008 concluded that Middle Triassic dicynodonts (including many kannemeyeriids) had a variable range of head movements, but were mostly specialised as ground to mid level browsers.

Behaviour
Social herding behaviour has been suggested for kannemeyeriiforms as a whole, based on aggregates of multiple individuals preserved together. Within kannemeyeriids, Wadiasaurus is known from a bonebed of at least 23 individuals, likely more, ranging in size from large adults to young juveniles. From comparisons with other specimens of Wadiasaurus, Bandyopadhyay suggested that the bonebed consisted of only tuskless adult females and juveniles, while the more robust and tusked specimens found in isolation were males. As such, she suggested that females and juveniles may have lived in herds, possibly of mothers and their offspring, while adult males may have been solitary. A similar aggregation of nine juveniles is also known for the Chinese kannemeyeriid Xiyukannemeyeria, and is similar to the juvenile aggregations of the non-kannemeyeriid Dinodontosaurus that are suggested to be crèches.

A large tetrapod burrow discovered in the Ermaying Formation is suggested to have possibly been dug by a juvenile dicynodont, specifically the kannemeyeriids Sinokannemeyeria or Parakannemeyeria. There is no direct evidence for this association, however it is based upon similar features (size, shape, scratchmarks) to burrows known to have been dug by Lystrosaurus in South Africa. The burrow is shallowly sloping and approximately 3 m in length, 13 cm in height and 30 cm in width. Although the adult kannemeyeriids are too large to have been the burrow-maker, juvenile kannemeyeriids were favoured due to sharing more similar skeletal features to the known burrower Lystrosaurus than the contemporary and smaller dicynodont Shansiodon.

Taxonomy
Under classical ranked Linnean taxonomy, Kannemeyeriidae is a family of dicynodonts under the infraorder Dicynodontoidea. The family was conceived by von Huene in 1948 to encompass all large Triassic dicynodonts (i.e. what is now Kannemeyeriiformes) and to taxonomically distinguish them from the Early Triassic Lystrosauridae and the various Permian dicynodonts grouped under Dicynodontidae. Both the unity and distinction of kannemeyeriids was broadly accepted by most researchers (though Romer (1956) maintained them as individual genera under Dicynodontidae), but there has historically been uncertainty and disagreement over the relationships between kannemeyeriid genera. In 1956, Charles Camp (known for describing Placerias) was the first highlight evidence for at least two distinct evolutionary lineages within the traditional Kannemeyeriidae, as did Ailing Sun in 1963. Lehman elaborated on Camp's ideas in 1961 and formally named two subfamilies of traditional Kannemeyeriidae, 'Kannemeyeroinae' and 'Stahleckeroinae' (later emended to Kannemeyeriinae and Stahleckeriinae in 1979 by Keyser & Cruickshank), with 'Kannemeyeroinae' including Kannemeyeria and similar genera with tall sagittal crests.

The origin of the modern, more restricted concept of Kannemeyeriidae was introduced by Cox in 1965 when he elevated the two subfamilies to individual families each (as well as introducing Shansiodontidae), with Kannemeyeriidae now equivalent to what was 'Kannemeyeroinae'. Cox's primarily diagnosed Kannemeyeriidae by having narrow snouts, and included the genera Kannemeyeria, Sinokannemeyeria, Parakannemeyeria, Placerias, Ischigualastia, and Barysoma (a junior synonym of Stahleckeria). Despite these three families ultimately forming the basis of modern kannemeyeriiform systematics, some researchers continued to use the traditional all encompassing Kannemeyeriidae (such as Keyser & Cruickshank (1979) and Lucas & Harris (1996)), but nonetheless recognised equivalent subdivisions as subfamilies. This was due to, in part, the disagreements over kannemeyeriiform relationships and evolutionary history, and indeed Cox's interpretation of Kannemeyeriidae does not wholly correspond to its modern contents. A novel taxonomic proposal by Gillian King in 1988 disregarded Kannemeyeriidae as family entirely, instead placing all curent kannemeyeriiforms in a single equivalent subfamily of Dicynodontidae, Kannemeyeriinae. King further recognised various subgroups as individual tribes, including a Kannemeyeriini roughly equivalent to Cox's Kannemeyeriidae and Cruickshank's Kannemeyeriinae. Notably though, she also split some kannemeyeriids into a new tribe of their own, Sinokannemeyeriini (see below).

Kannemeyeriidae, in the restricted sense of Cox (1965), returned to the family level when Maisch erected the clade Kannemeyeriiformes in 2001, albeit with a much reduced contents and placing several genera currently recognised as kannemeyeriids in a separate family and clade (see below). Owing to the uncertain phylogenetic relationships of these genera in subsequent analyses, researchers have not formally re-defined Kannemeyeriidae in a cladistic sense. However, the name remains used in kannemeyeriiform systematics. As currently recognised, the family Kannemeyeriidae encompasses most of the non-shansiodontid and non-stahleckeriid kannemeyeriiforms that typically lie between the two groups on the evolutionary tree. If not as a clade, these forms form a consistent cline of genera that share a common morphology to which the name Kannemeyeriidae continues to be applied, albeit in an informal sense.

Sinokannemeyeriini/-inae
Sinokannemeyeriini, or Sinokannemeyeriinae, is a now defunct but notable subgroup of kannemeyeriiforms that was consistently recognised in dicynodont systematics during the 1990s and early 2000s. The group was named by King in 1988 as an additional new tribe of her Kannemeyeriinae, Sinokannemeyeriini (along with Placeriini). King coined Sinokannemeyeriini for a clade of kannemeyeriiforms with relatively small temporal fenestra, broad and flat-topped snouts, and only a slight parietal crest. Sinokannemeyeriini included the kannemeyeriids Sinokannemeyeriia, Parakannemeyeria, Uralokannemeyeria, and Rhadiodromus (plus Dinodontosaurus), while other kannemeyeriids remained in the tribe Kannemeyeriini (comprising Kannemeyeria, Shaanbeikannemeyeria, Dolichuranus, and Wadiasaurus—along with the stahleckeriid Moghreberia).

Sinokannemeyeriini was typically upheld as a valid group by later researchers, including Lucas & Harris (1996), Surkov (2000) and Liu (2003). The group was also recognised by Maisch using computerised cladistics in 2001, wherein he formally elevated the tribe to a subfamily as Sinokannemeyeriinae at the same time he erected Kannemeyeriiformes. However, rather than including them as a subfamily of Kannemeyeriidae, Sinokannemeyeriinae was placed under a new family closer to stahleckeriids, the Dinodontosauridae. Further, he restricted the subfamily to only Sinokannemeyeria and Parakannemeyeria (and tentatively Rabidosaurus), while Rhadiodromus (including Uralokannemeyeria) was split off into a second dinodontosaurid subfamily with Rechnisaurus and the stahleckeriid Sangusaurus as Rechnisaurinae. A later analysis by Cristina Vega-Dias, Maisch, and Cesar Leandro Schultz in 2004 found Maisch's Dinodontosauridae to be paraphyletic but retained a monophyletic Sinokannemeyeriinae, while the status of Rechnisaurinae could not be analysed. In 2009, Romala Govender and Adam Yates elevated its rank yet again to a family as Sinokannemeyeriidae, and used the name for a clade equivalent to Maisch's Dinodontosauridae.

More recent studies since then utilising comprehensive phylogenetic analyses, namely that of Kammerer et al. (2011) and its derivatives, have not incorporated the name Sinokannemeyeriinae. Instead, genera historically referred to Sinokannemeyeriinae and similar subgroups have been grouped under kannemeyeriids owing to the uncertainties and lack of resolution of their relationships. As such, the aforementioned subfamilies and tribes, including Sinokannemeyeriinae, have yet to be formally recognised under modern phylogenetic and cladistic systematics.

Phylogeny
The first cladistic analysis of kannemeyeriiforms was performed by hand by King in 1988 and grouped kannemeyeriid genera into two distinct subgroups, the tribes Kannemeyeriini and Sinokannemeyeriini, with the latter closer to stahleckeriinins and placeriinins (i.e. Stahleckeriidae). The first computerised cladistic analysis of kannemeyeriids was later performed by Maisch in 2001, and included a restrictive Kannemeyeriidae clade (equivalent to King's Kannemeyeriini) that only contained Kannemeyeria, Wadiasaurus and tentatively Rabidosaurus (characterised by the middle of the skull being narrow and drawn up into a high sagittal crest between the temporal fenestra), whereas Parakannemeyeria, Sinokannemeyeria, Rechnisaurus and Rhadiodromus were grouped into Dinodontosauridae, closer to Stahleckeriidae. An analysis by Govender and Yates (2009) found a similar clade that they referred to as Sinokannemeyeriidae, however unlike Maisch they did not recover a Kannemeyeriidae clade at all, with Wadiasaurus and Kannemeyeria split as individual branches leading up to Sinokannemeyeriidae and Stahleckeriidae.

More comprehensive analyses of kannemeyeriiform relationships were performed by Christian Kammerer and colleagues in 2011 and 2013 which recovered taxa referred to Kannemeyeriidae and Sinokannemeyeriinae as an "assemblage" or evolutionary grade of Kannemeyeria-like genera spread more broadly in between shansiodontids and stahleckeriids. These results suggested "Kannemeyeriidae" as recognised is paraphyletic. However, more recent and expanded iterations of this dataset have found Kannemeyeria and similar taxa to group back together as monophyletic clade, such as Olivier et al. (2019) and Kammerer and Ordoñez (2021), to which the name Kannemeyeriidae has sometimes been applied.

Below are two cladograms depicting two recent and differing phylogenetic interpretations of Kannemeyeriidae that include the majority of valid kannemeyeriid species. The cladogram on the left depicts an example of a paraphyletic Kannemeyeriidae from Kammerer et al. (2013), while the right cladogram depicts a monophyletic Kannemeyeriidae as recovered by Kammerer and Ordoñez (2021) (also note the differing relationships between individual kannemeyeriid taxa on each tree):

Although taxa that have been taxonomically classified as kannemeyeriids have had their relationships tested phylogenetically, Kannemeyeriidae itself has never been formally defined as a clade—although Olivier and colleagues proposed a definition in 2019: "the clade comprising Kannemeyeria simocephalus and all taxa more closely related to it than to Stahleckeria potens, Placerias hesternus, or Shansiodon wangi". This is largely because of uncertainty over the overarching higher taxonomy of Kannemeyeriiformes, which is currently unresolved, as well as a lack of stability for the internal relationships between kannemeyeriids (as demonstrated by the two cladograms above). The status of Kannemeyeriidae as a clade is generally only weakly supported in phylogenetic analyses, although nonetheless Kenneth Angielczyk and colleagues (2018) have commented that it was still one of the most well-supported clades of Kannemeyeriiformes and identified four synapomorphies (unique shared traits).

Evolution and extinction
Kannemeyeriids likely arose from the shansiodontid grade or a similar ancestor among early kannemeyeriiforms. Acratophorus, identified as a basal kannemeyeriid by Kammerer and Ordoñez (2021), was noted to combine some shansiodontid-like characteristics of its skeleton (such as shorter processes of the ilium) with a skull that was more like those of other kannemeyeriids. The presence of a similar set of mixed-features in Dinodontosaurus (typically considered to be a close relative of the stahleckeriids) may then suggest that shansiodontid-like features could have been ancestral to both kannemeyeriids and stahleckeriids. Angielczyk and colleagues (2018) inferred kannemeyeriids to have predominantly radiated in Laurasia, based upon the topology of their phylogenetic analysis. In this scenario, kannemeyeriids quickly dispersed into Gondwana by the early Middle Triassic and achieved a nearly global distribution across the supercontinent Pangaea. By contrast, a study in 2023 by Polish palaeontologists Tomasz Szczygielski and Tomasz Sulej concluded from their topology that kannemeyeriids evolved in southern and eastern Africa, from which they dispersed into South America and Laurasia on multiple independent occasions. In Gondwana, they ranged across South Africa to Tanzania, Argentina, India, and possibly as far south as Antarctica. In Laurasia, kannemeyeriids are mostly known from China and European Russia. Curiously, they appear to be absent from intermediate regions.

Kannemeyeriids diversified during the Middle Triassic but seemingly did not persist beyond this epoch, with only the related stahleckeriids surviving into the Late Triassic (although Acratophorus and K. aganosteus may be dated to the Carnian based on U–Pb dating of the underlying strata). Because stahleckeriids were primarily known from the Late Triassic, it was suggested that their diversification may have been a 'slow fuse' that could only occur after other kannemeyeriiforms, namely kannemeyeriids, had gone extinct in the Middle Triassic. However, the discovery of definitive Middle Triassic stahleckeriids suggest that their diversification was concurrent with the kannemeyeriids, rather than inhibited by them until their extinction. Nonetheless, the extinction of kannemeyeriids may have benefited early stahleckeriids in local ecosystems. An example of this may have occurred in the Karoo Basin of South Africa, where Kannemeyeria is replaced by the stahleckeriid Ufudocyclops in the fossil record following just such an ecological turnover.