Haramiyida is a possibly polyphyletic order of mammaliaform cynodonts or mammals of controversial taxonomic affinites.[2] Their teeth, which are by far the most common remains, resemble those of the multituberculates. However, based on Haramiyavia, the jaw is less derived; and at the level of evolution of earlier basal mammals like Morganucodon and Kuehneotherium, with a groove for ear ossicles on the dentary.[3] Some authors have placed them in a clade with Multituberculata dubbed Allotheria within Mammalia.[4][5] Other studies have disputed this and suggested the Haramiyida were not crown mammals, but were part of an earlier offshoot of mammaliaformes instead.[6] It is also disputed whether the Late Triassic species are closely related to the Jurassic and Cretaceous members belonging to Euharamiyida/Eleutherodontida, as some phylogenetic studies recover the two groups as unrelated, recovering the Triassic haramiyidians as non-mammalian cynodonts, while recovering the Euharamiyida as crown-group mammals closely related to multituberculates.[7]
Haramiyids show certain similarities to multituberculates, a group of mammals that survived until about 40 million years ago. It is possible that haramiyids are ancestral to multituberculates, although the available evidence is insufficient to be conclusive. Certain characteristics of the teeth seem to rule out a special relationship between the two groups,[8] although some studies still unite haramiyids (or at least euharamiyids) and multituberculates in the Allotheria hypothesis.[9]
In a 2018 study, haramiyidans have been found to be a monophyletic group of non-mammalian Mammaliaformes. In this study, gondwanatheres – usually interpreted as mammals, and derived multituberculates in particular – have been found to be deeply nested among them.[10]
Order †Haramiyida[11][12] Hahn, Sigogneau-Russell & Wouters, 1989 [Haramiyoidea Hahn, 1973 sensu McKenna & Bell, 1997]
Haramiyids seem to have generally been herbivorous or omnivorous, possibly the first mammalian herbivores; however, the sole haramiyid tested in a study involving Mesozoic mammal dietary habits, Haramiyavia, ranks among insectivorous species.[16] At least some species were very good climbers and were similar to modern day squirrels;[17] and several others have more recently been reassessed as possibly arboreal. General arboreal habits might explain their rarity in the fossil record.[18]
Several euharamiyidans, Maiopatagium, Xianshou, Vilevolodon and Arboroharamiya, took it one step further and developed the ability to glide, having extensive membranes similar to those of modern colugos. In many of these taxa, the coracoid bones (absent in modern therians but present in many other mammal groups, albeit highly reduced) are remarkably large and similar to those of birds and pterosaurs, presumably due to impact stresses at landing.[19][20]