Zhelestidae is a lineage of

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

eutherian Eutheria (; from Greek , 'good, right' and , 'beast'; ) is the clade consisting of all therian mammals that are more closely related to placentals than to marsupials. Eutherians are distinguished from noneutherians by various phenotypic tra ...

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur ...

s. Occurring in 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'', ...

from the

Turonian The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous Epoch, or a stage in the Upper Cretaceous Series. It spans the time between 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded b ...

to the

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the inte ...

, they were an extremely successful group, with representatives present in

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

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 are ...

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...

(and subsequently in

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Afric ...

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

and

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

, ostensibly rendering them a cosmopolitan clade. They were specialised towards an herbivorous lifestyle and were in fact initially considered stem-

ungulates Ungulates ( ) are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. These include odd-toed ungulates such as horses, rhinoceroses, and tapirs; and even-toed ungulates such as cattle, pigs, giraffes, ca ...

, but the presence of epipubics and "archaic" dental characters render them as non-

placental 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 distinguishe ...

eutherians.

Range

The earliest zhelestid remains occur in the

Cenomanian The Cenomanian is, in the ICS' geological timescale, the oldest or earliest age of the Late Cretaceous Epoch or the lowest stage of the Upper Cretaceous Series. An age is a unit of geochronology; it is a unit of time; the stage is a unit in ...

Central Asia Central Asia, also known as Middle Asia, is a region of Asia that stretches from the Caspian Sea in the west to western China and Mongolia in the east, and from Afghanistan and Iran in the south to Russia in the north. It includes the fo ...

. By the

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campani ...

, however, they are present in

and

, and by the

and in

( UA 8699). In Europe, then an island continent, taxa usually accepted to be zhelestids are the most common Late Cretaceous mammal remains, aside from Hateg Island where

kogaionid Kogaionidae is a family of fossil mammals within the extinct order Multituberculata. Representatives are known from the Upper Cretaceous and the Paleocene of Europe. Having started as island endemics on Hateg Island during the Upper Cretaceous, ...

multituberculates Multituberculata (commonly known as multituberculates, named for the multiple tubercles of their teeth) is an extinct order of rodent-like mammals with a fossil record spanning over 130 million years. They first appeared in the Middle Jurassic, a ...

are more common instead, though there is a single possible zhelestid tooth there as well.

Ecology

Zhelestids are well specialised towards an herbivorous diet, their teeth suited for a lateral chewing mechanism similar to that of modern ungulates. An exception to this might be forms like '' Oxlestes'' and ''

Khuduklestes ''Khuduklestes'' is a genus of extinct mammal of uncertain affinities from the Late Cretaceous of China. It is rather similar to the also carnivorous and taxonomically uncertain ''Oxlestes'', being slightly smaller. Description ''Khuduklestes'' ...

'', which are normally interpreted as carnivorous, and perhaps a few forms like '' Borisodon'' which may have been insectivorous. Ranging from mouse sized forms to ones comparable to small ungulates in size, zhelestids occupied a massive variety of ecological guilds. In contrast to their dietary divergence, the few available limb remains suggest that they weren't very specialised locomotion wise, in contrast to some other basal

eutherians Eutheria (; from Greek , 'good, right' and , 'beast'; ) is the clade consisting of all therian mammals that are more closely related to placentals than to marsupials. Eutherians are distinguished from noneutherians by various phenotypic tr ...

like for instance ''

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 wi ...

'', which was long-limbed and had several adaptations for cursoriality and hopping. There is evidence that zhelestids were in direct competition with another clade of Mesozoic herbivorous mammals, the

, being rarer in places where these were most common and vice versa. However, multituberculates eventually outlived zhelestids, surviving the K-Pg extinction event everywhere but Asia, where the niches taken by both clades in the Cretaceous would be taken by early

rodents Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...

.Wood, D. Joseph (2010). The Extinction of the Multituberculates Outside North America: a Global Approach to Testing the Competition Model (M.S.). The Ohio State University.

References

{{Taxonbar, from=Q5133135 Prehistoric eutherians Maastrichtian extinctions Turonian first appearances Mammal taxonomy Prehistoric mammal families