Haramiyida

Haramiyida Temporal range: Late Triassic-Middle Jurassic, 216.5–183Ma PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Clade:	†Haramiyida Hahn, Sigogneau-Russell & Wouters, 1989
Subgroups
†Haramiyoidea †Haramiyidae †Haramiya †Haramiyaviidae †Haramiyavia †Kirtlingtonia †Millsodon †Theroteinida †Theroteinidae †Theroteinus †Euharamiyida †Eleutherodon †Sineleutherus †Arboroharamiya †Shenshou †Xianshou

Haramiyidans seem to be the earliest known herbivores amongst basal mammals. Their teeth, which are by far the most common remains, resemble those of the multituberculates. The jaw however, based on Haramiyavia, 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.^[1]

Relationships

Haramiyids show certain similarities to multituberculates, a group of mammals that have survived until about 40 million years ago. So it's 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,^[2] although some scientists still unite haramiyids (or at least Euharamiyids) and multituberculates in the Allotheria hypothesis.^[3]

Taxonomy

For a long time it was unknown if haramiyids were crown-group mammals, or if they should be placed in the stem-group Mammaliaformes. This uncertainty stems from the fact that haramiyid remains were mostly restricted to teeth and jaw fragments. However, new discoveries of much more complete haramiyid fossils have settled the issue—haramiyids are undoubtedly crown-group mammals. For example, the specimens show evidence of a typical mammalian middle ear, the area just inside the eardrum that turns vibrations in the air into ripples in the ear's fluids.^[4] The middle ears of mammals are unique in that they have three bones, as evidenced in the new fossils.

Lifestyle

Haramiyids seem to have been the first herbivores among the basal mammals. At least some species were very good climbers and were similar to modern day squirrels.^[5]

Range

Most fossils have been reported from Europe, but some are known from Africa and Greenland. Since 2005 the published range extended to Mongolia and China. The age of haramiyid fossils range from Upper Triassic up to Upper Jurassic. This has important implications: the fact that haramiyids were present in the Late Triassic supports the idea that crown-group mammals originated at least 208 million years ago, much earlier than some previous research suggests.

Notes

External links

• Palaeos, Mammaliaformes: Allotheria
• John H Burkitt, Mammals, A World Listing of Living and Extinct Species
• Time Scale (Mesozoic) - DinoData
• Mikko K Haaramo, Haramiyida

References

• Zofia Kielan-Jaworowska, Richard L. Cifelli, and Zhe-Xi Luo, Mammals from the Age of Dinosaurs: Origins, Evolution, and Structure (New York: Columbia University Press, 2004), 249-260.