Dryolestidae was an abundant and diverse group of Mesozoic mammals. These mammals were very different from their relatives by having the following two characteristics:

  • Their upper and lower molars were shortened mesiodistally and widened labiolingually.
  • The anterior root of lower molars were more robust and bigger.
Scientific classification

Marsh, 1879

Further reading

  • 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), 380-382.
Alcobaça Formation

The Alcobaça Formation is a geological formation in Portugal. It dates back to the Oxfordian stage of the Late Jurassic. It is an important source of information on the diversity of Late Jurassic mammals.


Amblotherium is an extinct genus of Late Jurassic mammal from the Morrison Formation.

Present in stratigraphic zones 2, 3, and 5.


Amphitheriida is an order of Mesozoic mammals restricted to the Middle Jurassic of Britain. They were closely related to the Dryolestids but possessed five molars instead of the usual four in Dryolestida, (with the exception of the family Dryolestidae whose members possessed between 8 and 9 molars). The Amphitheriida contains one family, the Amphitheriidae.

Como Bluff

Como Bluff is a long ridge extending east-west, located between the towns of Rock River and Medicine Bow, Wyoming. The ridge is an anticline, formed as a result of compressional geological folding. Three geological formations, the Sundance, the Morrison, and the Cloverly Formations, containing fossil remains from the Late Jurassic of the Mesozoic Era are exposed. Nineteenth century paleontologists discovered many well-preserved specimens of dinosaurs, as well as mammals, turtles, crocodilians, and fish from the Morrison Formation. Because of this, Como Bluff is considered to be one of the major sites for the early discovery of dinosaur remains. Among the species discovered is the only known specimen of Coelurus. Significant discoveries were made in 22 different areas scattered along the entire length of the ridge. It is included on the National Register of Historic Places as well as the National Natural Landmark list.

Cronopio (mammal)

Cronopio is an extinct genus of dryolestoid mammals known from the Río Negro region of Argentina.


Crusafontia is an extinct genus of mammal from the Cretaceous El Castellar Formation and La Huérguina Formations, Spain.Crusafontia was a 10 cm (3.9 in) long creature that may have looked and lived like a squirrel, but this is uncertain, as only two teeth (an upper molar right P5) and a mandible have ever been found.The name of the animal has been given in honour of the Spanish paleontologist Miquel Crusafont Pairó.


Dryolestes is an extinct genus of Late Jurassic mammal from the Morrison Formation and the Alcobaça Formation of Portugal.

Present in stratigraphic zones 2, 5, and 6.


Dryolestida is an extinct order of mammals; most of the members are mostly known from the Jurassic to Paleogene, with one member, Necrolestes, surviving as late as the early Miocene. It has been suggested that these mammals are either the possible ancestors of therian mammals or an offshoot from the same evolutionary line. It is also believed that they developed a fully mammalian jaw and also had the three middle ear bones. Other than that, not much is known about them, this is because their fossils are made up mostly of jaw and tooth remains.

Dryolestids were formerly considered part of Pantotheria and/or Eupantotheria. The clade Quirogatheria, erected by José Bonaparte in 1992, is often used as a synonym for Dryolestida. Originally, Quirogatheria was meant to include Brandoniidae, but this family is now included with the dryolestids.

It has been suggested on the basis of morphological evidence that they may still be extant in the form of marsupial moles. However, a molecular study places marsupial moles within Euaustralidelphia, though several problems with this assessment have been addressed.


Dryolestoidea is an extinct clade of Mesozoic mammals that only contains two orders. It has been suggested that this group is closely related to modern therian mammals.

El Molino Formation

The El Molino Formation is a Maastrichtian geologic formation pertaining to the Puca Group of central Bolivia. The formation comprises fine-grained sandstones and sandy limestones with stromatolites deposited in a shallow marine to lacustrine environment. The formation has provided fossils of Dolichochampsa minima, and ichnofossils of Ankylosauria indet., Ornithopoda indet., Theropoda indet. and Titanosauridae indet. The tracksite of Cal Orcko is the best known example of the ichnofossil locations of the formation. The ichnofossil of Ligabueichnum bolivianum may be attributed to an ankylosaur. The fossil fish species Dasyatis molinoensis is named after the formation.

Garden Park, Colorado

Garden Park is a paleontological site in Fremont County, Colorado, known for its Jurassic dinosaurs and the role the specimens played in the infamous Bone Wars of the late 19th century. Located 10 km (6.2 mi) north of Cañon City, the name originates from the area providing vegetables to the miners at nearby Cripple Creek in the 19th century. Garden Park proper is a triangular valley surrounded by cliffs on the southeast and southwest and by mountains to the north; however, the name is also refers to the dinosaur sites on top and along the cliffs. The dinosaur sites now form the Garden Park Paleontological Resource Area, which is overseen by the Bureau of Land Management.


Groebertherium is a genus of dryolestoid mammal from the Late Cretaceous Los Alamitos and Allen Formations of Argentina. It is not closely related to other contemporary dryolestoids, all of which are part of the clade Meridiolestida.

Itat Formation

The Itat Formation is a geologic formation in western Siberia. It was deposited in the Bajocian to Bathonian ages of the Middle Jurassic. Dinosaur remains are among the fossils that have been recovered from the formation, including the proceratosaurid Kileskus, caudata Urupia monstrosa, therapsida Amphibetulimus, Itatodon, Simpsonodon, Hutegotherium, Sineleutherus and dryolestidae Anthracolestes.

Ksar Metlili Formation

The Ksar Metlili Formation is a geological formation in eastern High Atlas of Morocco, it is late Tithonian to Berriasian in age. It is approximately 80 metres (260 ft) thick and primarily consists of mudstone and sandstone, with thin calcareous beds. One of these calcareous beds near the middle of the sequence is an important microvertebrate locality.


Leonardus is an extinct mammal genus from the Late Cretaceous (Late Santonian to Maastrichtian) of South America. It is a meridiolestidan dryolestoid, closely related to the also Late Cretaceous Cronopio and the Miocene Necrolestes, and potentially also modern marsupial mole.

Lourinhã Formation

The Lourinhã Formation is a fossil rich geological formation in western Portugal, named for the municipality of Lourinhã. The formation is Late Jurassic in age (Kimmeridgian/Tithonian) and is notable for containing a fauna similar to that of the Morrison Formation in the United States and the Tendaguru beds in Tanzania. The stratigraphy of the formation and the basin in general is disputed, with the constituent member beds belonging to the formation varying between different authorsBesides the fossil bones, Lourinhã Formation is well known for the fossil tracks and fossilized dinosaur eggs.The Lourinhã Formation includes several lithostratigraphic units, such as Praia da Amoreira-Porto Novo Members and the Sobral Unit.

Lulworth Formation

The Lulworth Formation is a geologic formation in England. It dates from the late Tithonian to the mid Berriasian. It is a subunit of the Purbeck Group. It consists of three members, which are in ascending order, the Mupe Member, the Ridgway Member, and the Warbarrow Tout Member. The Mupe Member is typically 11 to 16 m thick and largely consists of marls and micrites with interbeds of calcareous mudstone. The Ridgeway Member is about 3 to 7 m thick and consists of in its western portion carbonaceous muds, marls and micrites, in the east the muds are replaced by micritic limestone. The Warbarrow Tout Member is 17 to 39 m thick and consists of limestone at the base and micrite and mudstone for the rest of the sequence, this member is the primary source of the vertebrate fossils within the formation.

Mammal classification

Mammalia is a class of animal within the Phylum Chordata. Mammal classification has been through several iterations since Carl Linnaeus initially defined the class. No classification system is universally accepted; McKenna & Bell (1997) and Wilson & Reader (2005) provide useful recent compendiums. Many earlier ideas from Linnaeus et al. have been completely abandoned by modern taxonomists, among these are the idea that bats are related to birds or that humans represent a group outside of other living things. Competing ideas about the relationships of mammal orders do persist and are currently in development. Most significantly in recent years, cladistic thinking has led to an effort to ensure that all taxonomic designations represent monophyletic groups. The field has also seen a recent surge in interest and modification due to the results of molecular phylogenetics.

George Gaylord Simpson's classic "Principles of Classification and a Classification of Mammals" (Simpson, 1945) taxonomy text laid out a systematics of mammal origins and relationships that was universally taught until the end of the 20th century.

Since Simpson's 1945 classification, the paleontological record has been recalibrated, and the intervening years have seen much debate and progress concerning the theoretical underpinnings of systematization itself, partly through the new concept of cladistics. Though field work gradually made Simpson's classification outdated, it remained the closest thing to an official classification of mammals. See list of placental mammals and list of monotremes and marsupials for more detailed information on mammal genera and species.


Pantotheria is an abandoned taxon of Mesozoic mammals. This group is now considered an informal "wastebasket" taxon and has been replaced by Dryolestida as well as other groups. It is sometimes treated as an infraclass and older books refer to it as being related to symmetrodonts.


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