Morganucodon

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Morganucodon
Temporal range: Late Triassic-Middle Jurassic Rhaetian–Bathonian
Restored skull of Morganucodon oehleri.jpg
Scan and reconstruction of the M. oehleri holotype skull
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Therapsida
Clade: Cynodontia
Clade: Mammaliaformes
Order:† Morganucodonta
Family:† Morganucodontidae
Genus:† Morganucodon
Kühne, 1949
Type species
†Morganucodon watsoni
Kühne, 1949
Species
  • †M. watsoni(Kühne, 1949)
  • †M. oehleri(Rigney, 1963)
  • †M. heikuopengensis(Young, 1978)
  • †M. peyeri(Clemens, 1980)
  • †M. tardus(Butler and Sigogneau-Russell, 2016)

Morganucodon ("Glamorgan tooth") is an early mammaliaform genus that lived from the Late Triassic to the Middle Jurassic. It first appeared about 205 million years ago. Unlike many other early mammaliaforms, Morganucodon is well represented by abundant and well preserved (though in the vast majority of cases disarticulated) material. Most of this comes from Glamorgan in Wales (Morganucodon watsoni), but fossils have also been found in Yunnan Province in China (Morganucodon oehleri) and various parts of Europe and North America. Some closely related animals ( Megazostrodon ) are known from exquisite fossils from South Africa. [1]

The name comes from a Latinization of Morganuc, the name for South Glamorgan in the Domesday Book, the county of Wales where it was discovered by Walter Georg Kühne, [2] giving the meaning "Glamorgan tooth".

History of discovery

Lower jaw of M. watsoni, Natural History Museum, London Morganucodon watsoni.JPG
Lower jaw of M. watsoni, Natural History Museum, London

In the summer of 1947, fieldwork was done at Duchy Quarry in Glamorgan in southern Wales. Grey conglomerate that formed fissure fill deposits within karstic voids in Carboniferous limestone was extracted. In 1949, Walter Georg Kühne noted the lower cheek tooth of a primitive mammal while examining samples of the rock. He named it Morganucodon watsoni, with the genus name being derived from Morganuc, which Kühne stated was the name of South Glamorgan in the Domesday Book, with the species name being in honour of D. M. S. Watson. [2] Additional remains of M. watsoni were described by Kühne in 1958. [3] Also in 1958, Kenneth Kermack and Frances Mussett described additional remains from Pant Quarry, about a mile from Duchy Quarry, that had been collected in 1956. [4] In August 1948, an expedition to Lufeng in Yunnan, China yielded a 1 in (2.5 cm) long skull. It was shortly sent to Beijing (then Peking) and then eventually sent out of China, and deposited with Kenneth Kermack at University College London in 1960. The specimen was preliminarily described in 1963 by Harold W. Rigney, who noted the similarity to Morganucodon from Britain, and considered it cogeneric, naming the new species Morganucodon oehleri in honor of the reverend Edgar T. Oehler, who had originally collected the specimen. [5] In 1978 C. C. Young described Eozostrodon heikuopengensis from the Hei Koa Peng locality near Lufeng, based on an associated skull and dentary, as well as a right maxilla and associated dentary. [6] A revision by William A. Clemens in 1979 assigned this species to Morganucodon, based on its close similarity to the two previously named species. [4] In 1980 Clemens named the species Morganucodon peyeri, from isolated teeth found in Late Triassic (Rhaetian) deposits near Hallau, Switzerland, with the species being named after paleontologist Bernhard Peyer. [7] In 1981, Kermack, Mussett and Rigney published an extensive monograph on the skull of Morganucodon. [8] In 2016 Percy Butler and Denise Sigogneau-Russell named the species Morganucodon tardus from an upper right molar (M34984) collected from the Watton Cliff locality near Eype in Dorset, England, dating to the late Bathonian stage of the Middle Jurassic. The species being named after the Latin tardus, late, in reference to it being the youngest member of the genus. [9]

Biology

Life restoration of M. oehleri Morganucodon.jpg
Life restoration of M. oehleri
Digram of the skull of Morganucodon, with bones labelled Morganucodon skull.svg
Digram of the skull of Morganucodon, with bones labelled

Morganucodon was a small, plantigrade animal. The tail was moderately long. According to Kemp (2005), "the skull was 2–3 cm in length and a presacral body length of about 10 cm [4 inches]. In general appearance, it would have looked like a shrew or mouse". [10] There is evidence that it had specialized glands used for grooming, which may indicate that, like present day mammals, it had fur. [11]

Like present day mammals of similar size and presumed habit, Morganucodon was likely nocturnal and spent the day in a burrow. There is no direct fossil evidence, but several lines of evidence point to a nocturnal bottleneck in the evolution of the mammal class, and almost all modern mammals of similar size to Morganucodon are still nocturnal. [12] [13] Likewise, burrowing was widespread both in non-mammalian cynodonts and in primitive mammals. [14] [15] The logics of phylogenetic bracketing would make Morganucodon nocturnal and burrowing too. Plant material from the conifer Hirmeriella was also found in the fissure fills, indicating Morganucudon lived in, or near, a forested area.

The diet appears to have been insects and other small animals, with a preference for hard prey such as beetles. [16] Like most modern mammal insectivores, it grew fairly quickly to adult size. [17] Its eggs were probably small and leathery, a condition still found in monotremes. [18]

The teeth grew in mammalian fashion, with deciduous teeth being replaced by permanent teeth that were retained throughout the rest of the animal's life. [19] The combination of rapid growth in juveniles and a toothless stage at infancy strongly suggests that Morganucodon raised its young by lactation; indeed, it may have been among the first animals to do so. [20] The molars in the adult had a series of raised humps and edges that fit into each other, allowing for efficient chewing. However, unlike the situation in most later mammals, the upper and lower molars did not occlude properly when they first met; as they wore against each other, however, their shapes were modified by wear to produce a precise fit. [21]

A 2020 study suggests that the metabolism of Morganucodon was significantly slower than that of comparably sized modern mammals, and that it had a life-span more similar to that of reptiles, with the oldest specimen having a lifespan of 14 years. Thus it likely did not possess the fully endothermic metabolism seen in current mammals. [22]

Species

Skull and jaws of M. oehleri Morganucodon.svg
Skull and jaws of M. oehleri
SpeciesAuthorYearStatusTemporal rangeLocationFormations
Morganucodon watsoniKuehne1949 Early Jurassic (Hettangian-Sinemurian)England, WalesVarious fissure fill deposits
Morganucodon heikuopengensisYoung1978Early Jurassic (Sinemurian)Yunnan, China Lufeng
Morganucodon oehleriRigney1963Early Jurassic (Hettangian)
Morganucodon peyeriClemens1980 Late Triassic (Rhaetian)Switzerland, France Klettgau, grès infraliasiques (Saint-Nicolas-de-Port)
Morganucodon tardusButler and Sigogneau-Russel2016 Middle Jurassic (Bathonian)England Forest Marble

Classification

Life restoration of M. watsoni Morganucodon watsoni life restoration.jpg
Life restoration of M. watsoni

Morganucodon is the type genus for the order Morganucodonta, a group of generally similar mammaliaforms known from the Late Triassic to Late Jurassic epochs, [23] [24] with one possible member ( Purbeckodon ) dating to the Early Cretaceous. [25] All were small and likely insectivorous. Morganucodon is the best preserved and best understood member of Morganucodonta.

There is currently controversy about whether or not to classify Morganucodon as a mammal or as a non-mammalian mammaliaform. Some researchers limit the term "mammal" to the crown group mammals, which would not include Morganucodon and its relatives. Others, however, define "mammals", as a group, by the possession of a special, secondarily evolved jaw joint between the dentary and the squamosal bones, which has replaced the primitive one between the articular and quadrate bones in all modern mammalian groups. Under this definition, Morganucodon would be a mammal. Nevertheless, its lower jaw retains some of the bones found in its non-mammalian ancestors in a very reduced form rather than being composed solely of the dentary. Furthermore, the primitive reptile-like jaw joint between the articular and quadrate bones, which in modern mammals has moved into the middle ear and become part of the ear ossicles as malleus and incus, is still to be found in Morganucodon. [26] Morganucodon also suckled (it may have been the earliest animal to do so), had only two sets of teeth and grew rapidly to adult size and stopped growing thereafter, all typical mammalian traits. [27]

Phylogeny [28]
Mammaliaformes  

See also

Related Research Articles

<i>Megazostrodon</i> Extinct genus of mammaliaforms

Megazostrodon is an extinct genus of basal mammaliaforms belonging to the order Morganucodonta. It is approximately 200 million years old. Two species are known: M. rudnerae from the Early Jurassic of Lesotho and South Africa, and M. chenali from the Late Triassic of France.

Eozostrodon is an extinct morganucodont mammaliaform. It lived during the Rhaetian stage of the Late Triassic. Eozostrodon is known from disarticulated teeth from South West England and estimated to have been less than 10 cm (3.9 in) in head-body length, slightly smaller than the similar-proportioned Megazostrodon.

<span class="mw-page-title-main">Docodonta</span> Extinct order of mammaliaforms

Docodonta is an order of extinct Mesozoic mammaliaforms. They were among the most common mammaliaforms of their time, persisting from the Middle Jurassic to the Early Cretaceous across the continent of Laurasia. They are distinguished from other early mammaliaforms by their relatively complex molar teeth. Docodont teeth have been described as "pseudotribosphenic": a cusp on the inner half of the upper molar grinds into a basin on the front half of the lower molar, like a mortar-and-pestle. This is a case of convergent evolution with the tribosphenic teeth of therian mammals. There is much uncertainty for how docodont teeth developed from their simpler ancestors. Their closest relatives may have been certain Triassic "symmetrodonts", namely Woutersia, Delsatia, and Tikitherium.

<span class="mw-page-title-main">Mammaliaformes</span> Clade of mammals and extinct relatives

Mammaliaformes is a clade that contains the crown group mammals and their closest extinct relatives; the group radiated from earlier probainognathian cynodonts. It is defined as the clade originating from the most recent common ancestor of Morganucodonta and the crown group mammals; the latter is the clade originating with the most recent common ancestor of extant Monotremata, Marsupialia, and Placentalia. Besides Morganucodonta and the crown group mammals, Mammaliaformes includes Docodonta and Hadrocodium as well as the Triassic Tikitherium, the earliest known member of the group.

Sinoconodon is an extinct genus of mammaliamorphs that appears in the fossil record of the Lufeng Formation of China in the Sinemurian stage of the Early Jurassic period, about 193 million years ago. While sharing many plesiomorphic traits with other non-mammaliaform cynodonts, it possessed a special, secondarily evolved jaw joint between the dentary and the squamosal bones, which in more derived taxa would replace the primitive tetrapod one between the articular and quadrate bones. The presence of a dentary-squamosal joint is a trait historically used to define mammals.

<span class="mw-page-title-main">Evolution of mammals</span> Derivation of mammals from a synapsid precursor, and the adaptive radiation of mammal species

The evolution of mammals has passed through many stages since the first appearance of their synapsid ancestors in the Pennsylvanian sub-period of the late Carboniferous period. By the mid-Triassic, there were many synapsid species that looked like mammals. The lineage leading to today's mammals split up in the Jurassic; synapsids from this period include Dryolestes, more closely related to extant placentals and marsupials than to monotremes, as well as Ambondro, more closely related to monotremes. Later on, the eutherian and metatherian lineages separated; the metatherians are the animals more closely related to the marsupials, while the eutherians are those more closely related to the placentals. Since Juramaia, the earliest known eutherian, lived 160 million years ago in the Jurassic, this divergence must have occurred in the same period.

<span class="mw-page-title-main">Eutriconodonta</span> Extinct order of mammals

Eutriconodonta is an order of early mammals. Eutriconodonts existed in Asia, Africa, Europe, North and South America during the Jurassic and the Cretaceous periods. The order was named by Kermack et al. in 1973 as a replacement name for the paraphyletic Triconodonta.

<span class="mw-page-title-main">Haramiyida</span> Extinct order of mammaliaforms

Haramiyida is a possibly polyphyletic order of mammaliaform cynodonts or mammals of controversial taxonomic affinites. Their teeth, which are by far the most common remains, resemble those of the multituberculates. However, based on Haramiyavia, the jaw is less derived; and at the level of evolution of earlier basal mammals like Morganucodon and Kuehneotherium, with a groove for ear ossicles on the dentary. Some authors have placed them in a clade with Multituberculata dubbed Allotheria within Mammalia. Other studies have disputed this and suggested the Haramiyida were not crown mammals, but were part of an earlier offshoot of mammaliaformes instead. It is also disputed whether the Late Triassic species are closely related to the Jurassic and Cretaceous members belonging to Euharamiyida/Eleutherodontida, as some phylogenetic studies recover the two groups as unrelated, recovering the Triassic haramiyidians as non-mammalian cynodonts, while recovering the Euharamiyida as crown-group mammals closely related to multituberculates.

<span class="mw-page-title-main">Evolution of mammalian auditory ossicles</span> Middle ear bones evolved from jaw bones

The evolution of mammalian auditory ossicles was an evolutionary process that resulted in the formation of the bones of the mammalian middle ear. These bones, or ossicles, are a defining characteristic of all mammals. The event is well-documented and important as a demonstration of transitional forms and exaptation, the re-purposing of existing structures during evolution.

<i>Gobiconodon</i> Extinct genus of mammals

Gobiconodon is an extinct genus of carnivorous mammals belonging to the family Gobiconodontidae. Undisputed records of Gobiconodon are restricted to the Early Cretaceous of Asia and North America, but isolated teeth attributed to the genus have also been described from formations in England and Morocco dating as far back as the Middle Jurassic. Species of Gobiconodon varied considerably in size, with G. ostromi, one of the larger species, being around the size of a modern Virginia opossum. Like other gobiconodontids, it possessed several speciations towards carnivory, such as shearing molariform teeth, large canine-like incisors and powerful jaw and forelimb musculature, indicating that it probably fed on vertebrate prey. Unusually among predatory mammals and other eutriconodonts, the lower canines were vestigial, with the first lower incisor pair having become massive and canine-like. Like the larger Repenomamus there might be some evidence of scavenging.

<span class="mw-page-title-main">Morganucodonta</span> Extinct order of mammaliaforms

Morganucodonta is an extinct order of basal Mammaliaformes, a group including crown-group mammals (Mammalia) and their close relatives. Their remains have been found in Southern Africa, Western Europe, North America, India and China. The morganucodontans were probably insectivorous and nocturnal, though like eutriconodonts some species attained large sizes and were carnivorous. Nocturnality is believed to have evolved in the earliest mammals in the Triassic as a specialisation that allowed them to exploit a safer, night-time niche, while most larger predators were likely to have been active during the day.

<i>Kuehneotherium</i> Extinct genus of mammaliaforms

Kuehneotherium is an early mammaliaform genus, previously considered a holothere, that lived during the Late Triassic-Early Jurassic Epochs and is characterized by reversed-triangle pattern of molar cusps. Although many fossils have been found, the fossils are limited to teeth, dental fragments, and mandible fragments. The genus includes Kuehneotherium praecursoris and all related species. It was first named and described by Doris M. Kermack, K. A. Kermack, and Frances Mussett in November 1967. The family Kuehneotheriidae and the genus Kuehneotherium were created to house the single species Kuehneotherium praecursoris. Modeling based upon a comparison of the Kuehneotherium jaw with other mammaliaforms indicates it was about the size of a modern-day shrew between 4 and 5.5 g at adulthood.

<span class="mw-page-title-main">Triconodontidae</span> Extinct family of mammals

Triconodontidae is an extinct family of small, carnivorous mammals belonging to the order Eutriconodonta, endemic to what would become Asia, Europe, North America and probably also Africa and South America during the Jurassic through Cretaceous periods at least from 190–66 mya.

<span class="mw-page-title-main">Gobiconodontidae</span> Extinct family of mammals

Gobiconodontidae is a family of extinct mammals that ranged from the mid-Jurassic to the early Late Cretaceous, though most common during the Early Cretaceous. The Gobiconodontids form a diverse lineage of carnivorous non-therian mammals, and include some of the best preserved Mesozoic mammal specimens.

Kenneth Alexander Kermack was a British palaeontologist at University College London most notable for his work on early mammals with his wife, Doris Mary Kermack.

<i>Ichthyoconodon</i> Extinct family of mammals

Ichthyoconodon is an extinct genus of eutriconodont mammal from the Lower Cretaceous of Morocco. It is notable for having been found in a unique marine location, and the shape of its teeth suggests an unusual, potentially fish-eating ecological niche. Analysis suggests it is part of a group of gliding mammals that includes Volaticotherium.

Wareolestes rex is a mammaliaform from the Middle Jurassic (Bathonian) rocks of England and Scotland. It was originally known from isolated teeth from England, before a more complete jaw with teeth was found in the Kilmaluag Formation of Skye, Scotland.

Vilevolodon is an extinct, monotypic genus of volant, arboreal euharamiyids from the Oxfordian age of the Late Jurassic of China. The type species is Vilevolodon diplomylos. The genus name Vilevolodon references its gliding capabilities, Vilevol, while don is a common suffix for mammalian taxon titles. The species name diplomylos refers to the dual mortar-and-pestle occlusion of upper and lower molars observed in the holotype; diplo, mylos.

Bocaconodon is an early mammaliaform genus that lived during the Pliensbachian of Mexico. The type and only species, Bocaconodon tamaulipensis, was named and described in 2008. It is known from a single specimen, a partial right dentary bone preserving two nearly complete molar teeth and the rear portion of a third molar. The specimen was found at the Huizachal Canyon locality, "a Pliensbachian floodplain siltstone in the La Boca Formation".

<i>Kalaallitkigun</i> Extinct genus of mammaliaforms

Kalaallitkigun is an extinct genus of haramiyidan mammaliaforms from the Late Triassic of Greenland. It contains a single species, Kalaallitkigun jenkinsi, which was described in 2020 from a partial dentary found in the Fleming Fjord Formation. More specifically, it was found in the mid-late Norian Carlsberg Fjord beds of the Ørsted Dal Member. It is the oldest of several mammaliaform species discovered in the Late Triassic sediments of Greenland. It is also the oldest mammaliaform with double-rooted teeth, and its pattern of tooth cusps help to clarify the evolution of haramiyidan teeth relative to their morganucodont-like ancestors.

References

  1. ↑ Pages 21–33, 174 in Zofia Kielan-Jaworowska, Richard L. Cifelli, and Zhe-Xi Luo, Mammals from the Age of Dinosaurs: Origins, Evolution, and Structure, Columbia University Press, New York, 2004 ISBN   0-231-11918-6
  2. 1 2 Walter G. Kühne, "On a Triconodont tooth of a new pattern from a Fissure-filling in South Glamorgan", Proceedings of the Zoological Society of London, volume 119 (1949–1950) pages 345–350
  3. ↑ Kühne, Walter Georg (1958-08-01). "Rhaetische Triconodonten aus Glamorgan, ihre Stellung zwischen den Klassen Reptilia und Mammalia und ihre Bedeutung für die REICHART'sche Theorie" [Rhaetian triconodonts from Glamorgan, their position between the classes Reptilia and Mammalia and their significance for REICHART's theory.]. Paläontologische Zeitschrift (in German). 32 (3): 197–235. doi:10.1007/BF02989032. ISSN   0031-0220. S2CID   128828761.
  4. 1 2 Clemens, William A. (May 1979). "A problem in morganucodontid taxonomy (Mammalia)". Zoological Journal of the Linnean Society. 66 (1): 1–14. doi:10.1111/j.1096-3642.1979.tb01898.x.
  5. ↑ Rigney, Harold W. (March 1963). "A Specimen of Morganucodon from Yunnan". Nature. 197 (4872): 1122–1123. Bibcode:1963Natur.197.1122R. doi:10.1038/1971122a0. ISSN   0028-0836. S2CID   4204736.
  6. ↑ C.-C. Young. 1978. New materials of Eozostrodon. Vertebrata PalAsiatica16:1-3
  7. ↑ W. A. Clemens. 1980. Rhaeto-Liassic mammals from Switzerland and West Germany. Zitteliana5:51-92
  8. ↑ Kermack, K. A.; Mussett, Frances; Rigney, H. W. (January 1981). "The skull of Morganucodon". Zoological Journal of the Linnean Society. 71 (1): 1–158. doi:10.1111/j.1096-3642.1981.tb01127.x.
  9. ↑ Butler, P.M. and Sigogneau-Russell, D. 2016. Diversity of triconodonts in the Middle Jurassic of Great Britain. Palaeontologia Polonica 67, 35–65. LSID urn:lsid:zoobank.org: pub: C4D90BB6-A001-4DDB-890E-2061B4793992
  10. ↑ Kemp T.S. 2005. The origin and evolution of mammals, Oxford University Press, page 143. ISBN   0-19-850760-7.
  11. ↑ Ruben, J.A.; Jones, T.D. (2000). "Selective Factors Associated with the Origin of Fur and Feathers". American Zoologist . 40 (4): 585–596. doi: 10.1093/icb/40.4.585 .
  12. ↑ Hall, M. I.; Kamilar, J. M.; Kirk, E. C. (24 October 2012). "Eye shape and the nocturnal bottleneck of mammals". Proceedings of the Royal Society B: Biological Sciences. 279 (1749): 4962–4968. doi:10.1098/rspb.2012.2258. PMC   3497252 . PMID   23097513.
  13. ↑ Muchlinski, Magdalena N. (June 2010). "A comparative analysis of vibrissa count and infraorbital foramen area in primates and other mammals". Journal of Human Evolution. 58 (6): 447–473. doi:10.1016/j.jhevol.2010.01.012. PMID   20434193.
  14. ↑ Damiani, R.; Modesto, S.; Yates, A.; Neveling, J. (22 August 2003). "Earliest evidence of cynodont burrowing". Proceedings of the Royal Society B: Biological Sciences. 270 (1525): 1747–1751. doi:10.1098/rspb.2003.2427. PMC   1691433 . PMID   12965004.
  15. ↑ KIELAN, ZOFIA; GAMBARYAN, PETR P. (December 1994). "Postcranial anatomy and habits of Asian multituberculate mammals". Lethaia. 27 (4): 300. doi:10.1111/j.1502-3931.1994.tb01578.x. S2CID   85021289.
  16. ↑ Gill, Pamela G.; Purnell, Mark A.; Crumpton, Nick; Robson-Brown, Kate; Gostling, Neil J.; Stampanoni, M.; Rayfield, Emily J. (21 August 2014). "Dietary specializations and diversity in feeding ecology of the earliest stem mammals". Nature . 512 (7514): 303–305. Bibcode:2014Natur.512..303G. doi:10.1038/nature13622. hdl: 2381/29192 . PMID   25143112. S2CID   4469841.
  17. ↑ Chinsamy, A.; Hurum, J.H. (2006). "Bone microstructure and growth patterns of early mammals" (PDF). Acta Palaeontologica Polonica. 51 (2): 325–338. Retrieved 30 August 2013.
  18. ↑ Parente, Raphael Câmara Medeiros; Bergqvist, Lílian Paglarelli; Soares, Marina Bento; Filho, Olimpio Barbosa Moraes (2011). "The history of vaginal birth". Archives of Gynecology and Obstetrics. 284 (1): 1–11. doi:10.1007/s00404-011-1918-6. PMID   21547459. S2CID   22997887.
  19. ↑ Alexander F. H. van Nievelt and Kathleen K. Smith, "To replace or not to replace: the significance of reduced functional tooth replacement in marsupial and placental mammals", Paleobiology, Volume 31, Issue 2 (June 2005) pages 324–346
  20. ↑ Kielan-Jaworowska, Zofia; Cifelli, Richard L.; Luo, Zhe-Xi (2004). Mammals from the age of dinosaurs : origins, evolution, and structure. New York: Columbia University Press. pp. 148–153. ISBN   978-0231119184.
  21. ↑ Crompton, A. W.; Jenkins, F. Jr. (1968). "Molar occlusion in late Triassic mammals". Biological Reviews. 43 (4): 427–458. doi:10.1111/j.1469-185x.1968.tb00966.x. PMID   4886687. S2CID   1044399.
  22. ↑ Newham, Elis; et al. (2020). "Reptile-like physiology in Early Jurassic stem-mammals". Nature Communications. 11 (1): 5121. Bibcode:2020NatCo..11.5121N. doi: 10.1038/s41467-020-18898-4 . PMC   7550344 . PMID   33046697.
  23. ↑ Martin, T.; Averianov, A. O.; Jäger, K. R. K.; Schwermann, A. H.; Wings, O. (2019). "A large morganucodontan mammaliaform from the Late Jurassic of Germany" (PDF). Fossil Imprint. 75 (3–4): 504–509. doi: 10.2478/if-2019-0030 .
  24. ↑ pages 511–512, Malcolm C. McKenna and Susan K. Bell, Classification of Mammals Above the Species Level, Columbia University Press, 1997. ISBN   0-231-11012-X
  25. ↑ P. M. Butler, D. Sigogneau-Russell and P. C. Ensom (2011). "Possible persistence of the morganucodontans in the Lower Cretaceous Purbeck Limestone Group (Dorset, England)". Cretaceous Research. 33: 135–145. doi:10.1016/j.cretres.2011.09.007.
  26. ↑ Kermack, K. A.; Mussett, Frances; Rigney, H. W. (1981). "The skull of Morganucodon". Zoological Journal of the Linnean Society. 71: 1–158. doi:10.1111/j.1096-3642.1981.tb01127.x.
  27. ↑ Mammals of the Mesozoic: The least mammal-like mammals
  28. ↑ Close, Roger A.; Friedman, Matt; Lloyd, Graeme T.; Benson, Roger BJ (2015). "Evidence for a mid-Jurassic adaptive radiation in mammals". Current Biology. 25 (16): 2137–2142. doi: 10.1016/j.cub.2015.06.047 . PMID   26190074.
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