Dryolestida is an extinct order of mammals, primarily and possibly exclusively known from the
Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...
and
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
. They are considered members of the clade
Cladotheria
Cladotheria is a clade (sometimes ranked as a legion) of mammals. It contains modern therian mammals (marsupials and placentals) and several extinct groups, such as the dryolestoids, amphitheriids and peramurids. The clade was named in 1975 by M ...
, close to the ancestry of
theria
Theria (; Greek: , wild beast) is a subclass of mammals amongst the Theriiformes. Theria includes the eutherians (including the placental mammals) and the metatherians (including the marsupials) but excludes the egg-laying monotremes.
...
n mammals. It is also believed that they developed a fully mammalian jaw and also had the three middle ear bones. Most members of the group, as with most Mesozoic mammals, are only known from fragmentary tooth and jaw remains.
The taxonomic composition of the group is contested. Aside from the uncontroversial
Dryolestidae
Dryolestidae is an extinct family of Mesozoic mammals, known from the Middle Jurassic to the Early Cretaceous of the North Hemisphere. The oldest known member, '' Anthracolestes'', is known from the Middle Jurassic Itat Formation of Western Siber ...
Paurodontidae
Paurodontidae is a family of Late Jurassic to Early Cretaceous mammals in the order Dryolestida. Remains of paurodontids have been found in the United States, Britain, Portugal, and Tanzania. The group likely represents a paraphyletic group of b ...
, which were small insectivores, known from the Middle Jurassic to Early Cretaceous of Laurasia, the Meridiolestida, a diverse group of mammals including both small insectivores and mid-large sized herbivores known from the Late Cretaceous to
Miocene
The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...
of South America and possibly Antarctica, are also often included. However, in many phylogenetic analyses, Meridiolestida are recovered as an unrelated group of cladotherians.
Dryolestids were formerly considered part of
Pantotheria
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 ...
and/or
Eupantotheria
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 ...
. The clade Quirogatheria, erected by
José Bonaparte
José Fernando Bonaparte (14 June 1928 – 18 February 2020) was an Argentine paleontologist who discovered a plethora of South American dinosaurs and mentored a new generation of Argentine paleontologists
. One of the best-known Argentine paleo ...
in 1992, is often used as a synonym for Dryolestida. Originally, Quirogatheria was meant to include
Brandoniidae
Dryolestidae is an extinct family of Mesozoic mammals, known from the Middle Jurassic to the Early Cretaceous of the North Hemisphere. The oldest known member, '' Anthracolestes'', is known from the Middle Jurassic Itat Formation of Western Siber ...
, but this family is now included with the dryolestids.
Morphology
Dryolestids are mostly represented by
teeth
A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, t ...
, fragmented
dentaries
In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...
and parts of the
rostrum
Rostrum may refer to:
* Any kind of a platform for a speaker:
**dais
**pulpit
* Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects
* Rostrum (ship), a form of bow on naval ships
* Ros ...
. The
Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...
splenial
The splenial is a small bone in the lower jaw of reptiles, amphibians and birds, usually located on the lingual side (closest to the tongue) between the angular and surangular
The suprangular or surangular is a jaw bone found in most land ver ...
, but the
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
forms lack these. Another primitive feature is the presence of a
Meckelian groove The Meckelian groove (or Meckel's groove, Meckelian fossa, or Meckelian foramen, or Meckelian canal) is an opening in the medial (inner) surface of the mandible (lower jaw) which exposes the Meckelian cartilage.Meridiolestidans lost it altogether). A fundamentally modern ear is known in at least ''
Dryolestes
''Dryolestes'' is an extinct genus of Late Jurassic mammal from the Morrison Formation and the Alcobaça Formation
The Alcobaça Formation, previously known as the Guimarota Formation and also known as the Consolação Unit, is a geological fo ...
'' and
mesungulatids
Mesungulatidae is an extinct clade of meridiolestidan dryolestoid mammals from the Late Cretaceous of South America and possibly other Gondwannan landmasses. They are particularly notable for their ecological speciation and large size.
Charact ...
.
The basal non dryolestid dryolestidan ''
Henkelotherium
''Henkelotherium'' is an extinct genus of dryolestidan mammal from the Late Jurassic (Kimmeridgian) Camadas de Guimarota, in Portugal. Unlike many other Jurassic mammals, it is known from a largely complete skeleton, and is thought to have had ...
'' from the Late Jurassic of Portugal is known from a partial articulated skeleton, and is thought to have been
arboreal
Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. The habitats pose nu ...
, adapted to climbing and living in trees.
Tooth enamel
Tooth enamel is one of the four major tissues that make up the tooth in humans and many other animals, including some species of fish. It makes up the normally visible part of the tooth, covering the crown. The other major tissues are dentin, ...
evolved differently in marsupials and eutherians. In a first phase, during the late Triassic and Jurassic, prisms separated from the interprismatic matrix, probably independently in several Mesozoic mammal lineages. More derived enamel types evolved in a second phase, during the Tertiary and Quaternary, but without replacing the old prismatic enamel, instead forming various combinations of three-dimensional structures (called schmelzmuster). Dryolestid dentition is thought to resemble the primitive mammalian dentition before the marsupial-eutherian differentiation and dryolestids are candidates to be the
last common ancestor
In biology and genetic genealogy, the most recent common ancestor (MRCA), also known as the last common ancestor (LCA) or concestor, of a set of organisms is the most recent individual from which all the organisms of the set are descended. The ...
of the two mammalian subclasses. In mesungulatids molar tooth eruption is delayed compared to other dryolestoids.
Distribution
Dryolestids are known from the Jurassic through Early Cretaceous of the Northern Hemisphere (North America, Eurasia, and North Africa) and from 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 ...
through to the
Miocene
The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...
of South America. Drylestoids are very rarely found in the Cenozoic, as are the few other Mesozoic mammals with later descendants, such as
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, ...
,
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 ...
, and
gondwanatheres
Gondwanatheria is an extinct group of mammaliaforms that lived in parts of Gondwana, including Madagascar, India, South America, Africa and Antarctica during the Upper Cretaceous through the Paleogene (and possibly much earlier, if '' Allostaff ...
.
The oldest named member of Dryolestidae is '' Anthracolestes'' from the Middle
Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...
(
Bathonian
In the geologic timescale the Bathonian is an age and stage of the Middle Jurassic. It lasted from approximately 168.3 Ma to around 166.1 Ma (million years ago). The Bathonian Age succeeds the Bajocian Age and precedes the Callovian Age.
Str ...
) aged
Itat Formation
The Itat Formation ( Russian: итатская свита) 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 ...
in western Siberia. Fragmentary remains attributable to dryolestidans are known from the equivalently aged
Forest Marble Formation
The Forest Marble is a geological formation in England. Part of the Great Oolite Group, it dates to the late Bathonian stage of the Middle Jurassic.Weishampel, David B; et al. (2004). "Dinosaur distribution (Middle Jurassic, Europe)." In: Weisha ...
of England and the
Anoual Formation
The Anoual Formation is a geological formation in the High Atlas of Morocco. It is early Bathonian
In the geologic timescale the Bathonian is an age and stage of the Middle Jurassic. It lasted from approximately 168.3 Ma to around 166.1 Ma ...
of Morocco.
The youngests fossils of Dryolestidans in the Northern Hemisphere are the dryolestids '' Crusafontia cuencana'' from
Uña
Uña is a municipality located in the province of Cuenca, Castile-La Mancha, Spain. According to the 2004 census (INE
INE, Ine or ine may refer to:
Institutions
* Institut für Nukleare Entsorgung, a German nuclear research center
* Institu ...
and the
Camarillas Formation
The Camarillas Formation is a geological formation in the Teruel Province of Aragón, Spain whose strata date back to the Early Cretaceous (Barremian stage). The sandstones, mudstones and conglomerates of the formation, that due to syn-sediment ...
Balve
Balve is a town in the Märkischer Kreis district, North Rhine-Westphalia, Germany. It is located in ''Hönnetal'', a narrow valley created by the river Hönne, which is near the Sorpe Dam, formerly part of Balve, and at the north end of the Sau ...
, Germany, which all date to the
Barremian
The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 129.4 ± 1.5 Ma (million years ago) and 121.4 ± 1.0 Ma). It is a subdivision of the Early Cretaceous Epoch (or Lower Cretaceous Series). It is precede ...
- Aptian stages of the Early Cretaceous, though a fragmentary lower molar from the late Cretaceous
Mesaverde Formation
The Mesaverde Group is a Late Cretaceous stratigraphic group found in areas of Colorado, New Mexico, Utah, and Wyoming, in the Western United States.
History
The Mesaverde Formation was first described by W.H.Holmes in 1877 during the Hayden ...
in Wyoming has been tentatively attributed to Dryolestidae. In South America, by contrast, Meridiolestida thrived in the Late Cretaceous, diversifying in a myriad of forms such as the saber-toothed '' Cronopio'' and the herbivorous
mesungulatids
Mesungulatidae is an extinct clade of meridiolestidan dryolestoid mammals from the Late Cretaceous of South America and possibly other Gondwannan landmasses. They are particularly notable for their ecological speciation and large size.
Charact ...
, becoming some of the most ecologically diverse Mesozoic South American mammals. ''
Groebertherium
''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.
Class ...
'' from the Late Cretaceous of South America has a more primitve morphology similar to Northern Hemisphere dryolestids and may be more closely related to the North Hemisphere dryloestidans than to Meridiolestida.
With the advent of the Cenozoic, dryolestoids declined drastically in diversity, with only the large dog-sized herbivore ''
Peligrotherium
''Peligrotherium'' is an extinct meridiolestidan, and the sole member of the family Peligrotheriidae, from the Paleocene of Patagonia, originally interpreted as a stem-ungulate (though it did co-exist with early meridiungulates). Its remains hav ...
'' being known from the Palaeocene. The exact reasons for this decline are not clear; most likely they simply did not recover from the K-Pg event. Nonetheless, meridiolestidans would continue to survive until the
Miocene
The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...
, from when ''
Necrolestes
''Necrolestes'' ("grave robber" or "thief of the dead") is an extinct genus of mammals, which lived during the Early Miocene in what is now Argentine Patagonia. It is the most recent known genus of Meridiolestida, an extinct group of mammals m ...
'' is known; a gap of 50 million years exists between it and ''
Peligrotherium
''Peligrotherium'' is an extinct meridiolestidan, and the sole member of the family Peligrotheriidae, from the Paleocene of Patagonia, originally interpreted as a stem-ungulate (though it did co-exist with early meridiungulates). Its remains hav ...
''. A tooth fragment, now lost, found in the Eocene aged
La Meseta Formation
The La Meseta Formation is a sedimentary sequence deposited during the Eocene. The formation is found on Seymour Island, Antarctica.
Description
La Meseta Formation lies unconformably on the Cretaceous Lopez de Bertodano Formation. It is an a ...
of the Antarctic peninsula, is possibly a meridiolestidan.
Dryolestidae
Dryolestidae is an extinct family of Mesozoic mammals, known from the Middle Jurassic to the Early Cretaceous of the North Hemisphere. The oldest known member, '' Anthracolestes'', is known from the Middle Jurassic Itat Formation of Western Siber ...
**''
Amblotherium
''Amblotherium'' is an extinct genus of Late Jurassic and Early Cretaceous mammal. The type species ''Amblotherium pusillum'' is from the Lulworth Formation of southern England, while the referred species ''Amblotherium gracile'' is from strati ...
''
**''
Comotherium
''Comotherium'' is an extinct genus of Late Jurassic (Kimmeridgian - Tithonian) mammal from the Morrison Formation.
Present in stratigraphic zone 5.Foster, J. (2007). "Appendix." ''Jurassic West: The Dinosaurs of the Morrison Formation and Their ...
''
**''
Crusafontia
''Crusafontia'' is an extinct genus of mammal from the Cretaceous Camarillas, El Castellar and La Huérguina Formations of Spain. The name of the animal was given in honour of the Spanish paleontologist Miquel Crusafont Pairó.
''Crusafontia ...
''
**''
Dryolestes
''Dryolestes'' is an extinct genus of Late Jurassic mammal from the Morrison Formation and the Alcobaça Formation
The Alcobaça Formation, previously known as the Guimarota Formation and also known as the Consolação Unit, is a geological fo ...
''
**''
Groebertherium
''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.
Class ...
Laolestes
''Laolestes'' is an extinct genus of dryolestid mammal. Fossil remains are known from the Morrison Formation, in stratigraphic zones 5 and 6.,Foster, J. (2007). "Appendix." ''Jurassic West: The Dinosaurs of the Morrison Formation and Their Wor ...
Phascolestes
''Phascolestes'' is a genus of extinct mammal from the Berriasian epoch of Early Cretaceous Southern England. The type and only species is ''Phascolestes mustelulus'', which was named by Richard Owen in 1871 for dental material from the Lulw ...
Paurodontidae
Paurodontidae is a family of Late Jurassic to Early Cretaceous mammals in the order Dryolestida. Remains of paurodontids have been found in the United States, Britain, Portugal, and Tanzania. The group likely represents a paraphyletic group of b ...
**?''
Brancatherulum
''Brancatherulum'' is an extinct genus of Late Jurassic (Kimmeridgian - Tithonian) mammal from the Tendaguru Formation of Lindi Region of Tanzania. It is based on a single toothless dentary 21 mm in length. It is currently considered either a ste ...
''
**''
Dorsetodon
''Dorsetodon'' is an extinct genus of mammal from the Early Cretaceous ( Berriasian) Purbeck Group of Britain. It is represented by isolated lower molars.P. C. Ensom and D. Sigogneau-Russell, 1998. New dryolestoid mammals from the basal Cretaceo ...
''
**''
Drescheratherium
''Drescheratherium'' is an extinct genus of mammal from the Late Jurassic (Kimmeridgian) Camadas de Guimarota of Leiria, Portugal. It is represented by fairly complete upper jaws with teeth. It bears elongated upper canines, though not to the e ...
''
**''
Euthlastus
''Euthlastus'' is an extinct genus of Late Jurassic (Kimmeridgian - Tithonian) mammal from the Morrison Formation.
Present in stratigraphic zones 5 and 6.Foster, J. (2007). "Appendix." ''Jurassic West: The Dinosaurs of the Morrison Formation and ...
''
**''
Henkelotherium
''Henkelotherium'' is an extinct genus of dryolestidan mammal from the Late Jurassic (Kimmeridgian) Camadas de Guimarota, in Portugal. Unlike many other Jurassic mammals, it is known from a largely complete skeleton, and is thought to have had ...
''
**''
Paurodon
''Paurodon'' is an extinct genus of Late Jurassic mammal from the Morrison Formation of the Western United States.
Taxonomy
''Paurodon'' is the type genus of the dryolestidan group Paurodontidae. ''Araeodon'', ''Archaeotrigon'', ''Foxraptor'', ...
''
**''
Tathiodon
''Tathiodon'' is an extinct genus of Late Jurassic (Kimmeridgian - Tithonian) mammal from the Morrison Formation.
Present in stratigraphic zone 5.Foster, J. (2007). "Appendix." ''Jurassic West: The Dinosaurs of the Morrison Formation and Their ...
Leonardus
''Leonardus'' is an extinct mammal genus from the Late Cretaceous ( Late Santonian to Maastrichtian) of South America.
''
**''
Necrolestes
''Necrolestes'' ("grave robber" or "thief of the dead") is an extinct genus of mammals, which lived during the Early Miocene in what is now Argentine Patagonia. It is the most recent known genus of Meridiolestida, an extinct group of mammals m ...
Austrotriconodon
''Austrotriconodon'' is a mammal genus from the Campanian and Maastrichtian of South America. It currently contains only the type species, ''A. mckennai''. Originally assumed to be a eutriconodont, more recent studies have recovered it as a mer ...
''
**†
Brandoniidae
Dryolestidae is an extinct family of Mesozoic mammals, known from the Middle Jurassic to the Early Cretaceous of the North Hemisphere. The oldest known member, '' Anthracolestes'', is known from the Middle Jurassic Itat Formation of Western Siber ...
Donodontidae
Cladotheria is a clade (sometimes ranked as a legion) of mammals. It contains modern therian mammals (marsupials and placentals) and several extinct groups, such as the dryolestoids, amphitheriids and peramurids. The clade was named in 1975 by M ...
***''
Donodon
''Donodon'' is an extinct genus of mammal from the Ksar Metlili Formation of Talssint, Morocco, which has been dated to the Late Jurassic to Early Cretaceous epochs ( Tithonian–Berriasian ages). The type species ''D. prescriptoris'' was descr ...
''
**†
Mesungulatoidea
Meridiolestida is an extinct clade of mammals known from the Cretaceous and Cenozoic of South America and possibly Antarctica. They represented the dominant group of mammals in South America during the Late Cretaceous. Meridiolestidans were mor ...
***†
Mesungulatidae
Mesungulatidae is an extinct clade of meridiolestidan dryolestoid mammals from the Late Cretaceous of South America and possibly other Gondwannan landmasses. They are particularly notable for their ecological speciation and large size.
Charact ...
Coloniatherium
''Coloniatherium'' is a meridiolestid mammal from the Late Cretaceous of Argentina. The single species, ''Coloniatherium cilinskii'', was a large member of the family Mesungulatidae.
Taxonomy
''Coloniatherium'' was named in 2009 by Guillermo ...
Peligrotheriidae
''Peligrotherium'' is an extinct meridiolestidan, and the sole member of the family Peligrotheriidae, from the Paleocene of Patagonia, originally interpreted as a stem-ungulate (though it did co-exist with early meridiungulates). Its remains have ...
****''
Peligrotherium
''Peligrotherium'' is an extinct meridiolestidan, and the sole member of the family Peligrotheriidae, from the Paleocene of Patagonia, originally interpreted as a stem-ungulate (though it did co-exist with early meridiungulates). Its remains hav ...
''
***†
Reigitheriidae
''Reigitherium'' was a mammal that lived during the Late Cretaceous, in the (Late Campanian-Maastrichtian). Its fossils have been found in the Los Alamitos Formation, Los Alamitos and the La Colonia Formation, La Colonia Formation (geology), Form ...
****''
Reigitherium
''Reigitherium'' was a mammal that lived during the Late Cretaceous, in the (Late Campanian-Maastrichtian). Its fossils have been found in the Los Alamitos and the La Colonia Formations of Argentina.
Description
The original specimen of ''Re ...
''
A phylogenetic analysis conducted by Rougier ''et al.'' (2012) indicated that meridiolestidans might not be members of Dryolestida but instead slightly more closely related to the
placental mammals
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 ...
,
marsupial
Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a ...
s and amphitheriids. Paurodontids were also recovered as not belonging to Dryolestida, but instead as a sister group of Meridiolestida in this analysis. An analysis conducted by Averianov, Martin and Lopatin (2013) did not recover meridiolestidans as members of Dryolestida as well, but it found them to be the sister group of
spalacotheriid
Spalacotheriidae is a family of extinct mammals belonging to the paraphyletic group ' Symmetrodonta'. They lasted from the Early Cretaceous to the Campanian in North America, Europe, Asia and North Africa.
Spalacotheriids are characterised by ha ...
" symmetrodonts" instead. However, paurodontids were recovered as members of Dryolestida in this analysis. On the other hand, an analysis conducted by Chimento, Agnolin and Novas (2012) did recover meridiolestidans as members of Dryolestida.