''Eozostrodon'' is an extinct

morganucodont Morganucodonta ("Glamorgan teeth") is an extinct order of basal Mammaliaformes, a group including crown-group mammals (Mammalia) and their close relatives. Their remains have been found in Southern Africa, Western Europe, North America, India an ...

mammaliaform Mammaliaformes ("mammalian forms") is a clade that contains the crown group mammals and their closest extinct relatives; the group radiated from earlier probainognathian cynodonts. It is defined as the clade originating from the most recent com ...

. It 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

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 ...

. ''Eozostrodon'' is known from disarticulated bones from Wales and

South West England South West England, or the South West of England, is one of nine official regions of England. It consists of the counties of Bristol, Cornwall (including the Isles of Scilly), Dorset, Devon, Gloucestershire, Somerset and Wiltshire. Cities and ...

and estimated to have been less than in head-body length, slightly smaller than the similar-proportioned ''

Megazostrodon ''Megazostrodon'' is an extinct genus of basal mammaliaforms belonging to the order Morganucodonta. It is approximately 200 million years old.

''. ''Eozostrodon'' was described on the basis of two teeth discovered in a quarry near

Frome Frome ( ) is a town and civil parish in eastern Somerset, England. The town is built on uneven high ground at the eastern end of the Mendip Hills, and centres on the River Frome. The town, about south of Bath, is the largest in the Mendip d ...

Somerset, England ( en, All The People of Somerset) , locator_map = , coordinates = , region = South West England , established_date = Ancient , established_by = , preceded_by = , origin = , lord_lieutenant_office =Lord Lieutenant of Somerset , lord_ ...

, each originally assigned to separate species ''E. parvus'' and ''E. problematicus''. The latter was synonymized in 1971. The identity of and status of ''Eozostrodon'' is controversial. Kühne considered ''Eozostrodon'' to be "one and the same" with ''

Morganucodon ''Morganucodon'' (" Glamorgan tooth") is an early mammaliaform genus that lived from the Late Triassic to the Middle Jurassic. It first appeared about 205 million years ago. Unlike many other early mammaliaforms, ''Morganucodon'' is well represe ...

'' which he described, albeit after the published description of ''Eozostrodon'', claiming "...for a number of good reasons ''Morganucodon'' ought to be used, the name of ''Eozostrodon'' being used for sentimental reasons only or because of ignorance." Jenkins and Crompton in 1979 argued ''Morganucodon'' was a subjective synonym of ''Eozostrodon'', yet Clemens (1979) argued for the distinction. A more recent publication again distinguished the two, noting that ''Eozostrodon'' differs from ''M. watsoni'' in relative size and shape of

premolar The premolars, also called premolar teeth, or bicuspids, are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant in the permanent set of teeth, making eight premolars total in the mouth ...

structures.Z. Kielan-Jaworowska, R. L. Cifelli, and Z.-X. Luo. 2004. ''Mammals from the age of dinosaurs: Origins, evolution, and structure.'' Columbia University Press, New York 1-630. Its teeth were typical for an early mammaliaform, being differentiated into premolars and molars with triangular cusps.

References

External links

Restoration of ''Eozostrodon''
Morganucodonts Prehistoric cynodont genera Rhaetian life Late Triassic synapsids of Europe Triassic England Fossils of England Fossil taxa described in 1941 Taxa named by Francis Rex Parrington {{paleo-therapsid-stub