Zhelestidae is a lineage of

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

eutherian Eutheria (from Greek , 'good, right' and , 'beast'; ), also called Pan-Placentalia, is the clade consisting of placental mammals and all therian mammals that are more closely related to placentals than to marsupials. Eutherians are distingu ...

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

s. Occurring in the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent 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 ''cre ...

from the

Turonian The Turonian is, in the International Commission on Stratigraphy, ICS' geologic timescale, the second age (geology), age in the Late Cretaceous epoch (geology), Epoch, or a stage (stratigraphy), stage in the Upper Cretaceous series (stratigraphy), ...

to the

Maastrichtian The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (s ...

, they were an extremely successful group, with representatives present in Europe, Asia, India (and subsequently in

Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...

), Africa and North America, ostensibly rendering them a

cosmopolitan Cosmopolitan may refer to: Internationalism * World citizen, one who eschews traditional geopolitical divisions derived from national citizenship * Cosmopolitanism, the idea that all of humanity belongs to a single moral community * Cosmopolitan ...

clade. They were specialised towards an herbivorous lifestyle and were in fact initially considered stem-

ungulates Ungulates ( ) are members of the diverse clade Euungulata ("true ungulates"), which primarily consists of large mammals with hooves. Once part of the clade "Ungulata" along with the clade Paenungulata, "Ungulata" has since been determined to b ...

, but the presence of

epipubic 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 placentals, who lack them). They first occur in ...

s 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 distinguished ...

eutherians.

Range

The earliest zhelestid remains occur in the

Cenomanian The Cenomanian is, in the International Commission on Stratigraphy's (ICS) geological timescale, the oldest or earliest age (geology), age of the Late Cretaceous epoch (geology), Epoch or the lowest stage (stratigraphy), stage of the Upper Cretace ...

Central Asia Central Asia is a region of Asia consisting of Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan. The countries as a group are also colloquially referred to as the "-stans" as all have names ending with the Persian language, Pers ...

. 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. Campa ...

, however, they are present in

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

and

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

, and by the

India India, officially the Republic of India, 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 by population (United Nations), most populous country since ...

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

Hațeg Island Hațeg Island was a large offshore Former island, island in the Tethys Sea which existed during the Late Cretaceous period, probably from the Cenomanian to the Maastrichtian ages. It was situated in an area corresponding to the region around moder ...

where kogaionid

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 ''Oxlestes'' is an extinct mammal from the Late Cretaceous of Asia, more specifically from the Cenomanian of Uzbekistan. A carnivorous species of uncertain affinities, it is notable for its relatively large size, being among the largest of all M ...

'' 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'; ), also called Pan-Placentalia, is the clade consisting of placental mammals and all therian mammals that are more closely related to placentals than to marsupials. Eutherians are distingu ...

like for instance ''

Zalambdalestes ''Zalambdalestes'' (meaning ''much-like-lambda robber'') is an extinct genus of eutherian mammal known from the Upper Cretaceous in Mongolia. Description ''Zalambdalestes'' was a hopping animal with a long snout, long teeth, a small brain and ...

'', 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 n ...

.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.

Phylogeny

Below is a phylogeny from Gheerbrant & Teodori (2021):

References

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