Zalambdalestidae is a clade of

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...

n eutherians occurring during the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

. Once classified as

Glires Glires (, Latin ''glīrēs'' 'dormice') is a clade (sometimes ranked as a grandorder) consisting of rodents and lagomorphs ( rabbits, hares, and pikas). The hypothesis that these form a monophyletic group has been long debated based on morp ...

, features like

epipubic bones Epipubic bones are a pair of bones projecting forward from the pelvic bones of modern marsupials, monotremes and fossil mammals like multituberculates, and even basal eutherians (the ancestors of placental mammals, who lack them). They first oc ...

and various cranial elements have identified these animals as outside of

Placentalia Placental mammals (infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguished ...

, representing thus a specialised clade of non-placental eutherians without any living descendants, and potentially rather different from modern placentals in at least reproductive anatomy.

Taxonomy

The exact position of Zalambdalestidae within Eutheria varies, though they are generally agreed to be more basal than zhelestids. Currently, the clade includes the genera ''

Zalambdalestes ''Zalambdalestes'' (meaning ''much-like-lambda robber'') was a eutherian mammal, most likely not a placental due to the presence of an epipubic bone, living during the Upper Cretaceous in Mongolia. ''Zalambdalestes'' was a hopping animal with ...

'', '' Alymlestes'', '' Anchilestes'', '' Barunlestes'', '' Kulbeckia'', '' Zhangolestes'' and '' Zofialestes''.

Palaeobiology

Zalambdaltestids were insectivores, having

zalambdodont The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone ...

molars much as various modern insectivorous species. They are uniquely suited to a saltatorial, cursorial lifestyle, bearing long, semi-digitigrade limbs and a spinal column similar to that of modern

lagomorphs The lagomorphs are the members of the taxonomic order Lagomorpha, of which there are two living families: the Leporidae ( hares and rabbits) and the Ochotonidae (pikas). The name of the order is derived from the Ancient Greek ''lagos'' (λα� ...

. Like most non-placental mammals, the presence of epipubic bones probably meant that they gave birth to poorly developed young much like modern marsupials and

monotremes Monotremes () are prototherian mammals of the order Monotremata. They are one of the three groups of living mammals, along with placentals (Eutheria), and marsupials ( Metatheria). Monotremes are typified by structural differences in their br ...

References

{{Taxonbar, from=Q144978 Prehistoric eutherians Natural history of Mongolia Late Cretaceous mammals of Asia Djadochta fauna Prehistoric mammal families