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{{short description|Extinct genus of mammaliaforms}}
{{automatic taxobox
{{automatic taxobox
| fossil_range = [[Late Triassic]] - [[Early Jurassic]], {{fossil range|220|195}}
| fossil_range = [[Rhaetian]]-[[Hettangian]]<br>~{{fossil range|206|199}}
| image = Kuehneotherium molar terminology.png
| image = Kuehneotherium molar terminology.png
| image_caption = Upper and lower molars of ''Kuehneotherium''
| image_caption = Upper and lower molars of ''Kuehneotherium''
| taxon = Kuehneotherium
| taxon = Kuehneotherium
| authority = D.M. Kermack ''et al.'', 1968
| authority = D.M. Kermack ''et al.'', 1968
| type_species = {{extinct}}''Kuehneotherium praecursoris''
| type_species = {{Extinct}}'''''Kuehneotherium praecursoris'''''
| type_species_authority = D.M. Kermack ''et al.'', 1968
| type_species_authority = D.M. Kermack ''et al.'', 1968
| subdivision_ranks = Other species
| subdivision =
* {{Extinct}}'''''K. stanislavi''''' {{Small|Debuysschere, 2017}}<ref name="Debuysschere" />
}}
}}


'''''Kuehneotherium''''' is an early [[Mammaliaformes|mammaliaform]] [[genus]] that lived during the late [[Triassic]] period and is characterized by reversed-triangle pattern of [[Molar (tooth)|molar]] [[Cusp (anatomy)|cusps]].<ref>{{cite journal | last1 = Kermack | first1 = Doris M. | last2 = Kermack | first2 = K.A. | last3 = Mussett | first3 = Frances | year = 1968 | title = The Welsh pantothere Kuehneotherium praecursoris | url = | journal = Journal of the Linnean Society of London, Zoology | volume = 47 | issue = 312| pages = 407–423 | doi=10.1111/j.1096-3642.1968.tb00519.x}}</ref> 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 mammals indicates they were about the size of a modern-day shrew between 4 and 5.5 g at adulthood.
'''''Kuehneotherium''''' is an early [[mammaliaform]] [[genus]], previously considered a [[Holotheria|holothere]], that lived during the [[Late Triassic]]-[[Early Jurassic]] Epochs and is characterized by reversed-triangle pattern of [[Molar (tooth)|molar]] [[Cusp (anatomy)|cusps]].<ref>{{cite journal | last1 = Kermack | first1 = Doris M. | last2 = Kermack | first2 = K.A. | last3 = Mussett | first3 = Frances | year = 1968 | title = The Welsh pantothere Kuehneotherium praecursoris | journal = Journal of the Linnean Society of London, Zoology | volume = 47 | issue = 312| pages = 407–423 | doi=10.1111/j.1096-3642.1968.tb00519.x}}</ref> 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.


''Kuehneotherium'' is thought to be an [[insectivore]] that could consume only soft-bodied insects such as moths. Their teeth were shaped for vertical shearing and could not crush harder prey. They lived alongside another early mammal, ''[[Morganucodon]]'', which had teeth that could crush harder insects such as beetles. This distinction in diet shows that early mammals adapted to have a separate feeding niche so they would not compete for food.<ref>Gill, Pam, M.D. Morganucodon – lower jaw of an early mammal, Animal Bytes 13 June 2013. Web. retrieved http://animalbytescambridge.wordpress.com/2013/06/05/morganucodon-lower-jaw-of-an-early-mammal/#comments</ref><ref>{{Cite journal | doi=10.1038/nature13622| pmid=25143112| title=Dietary specializations and diversity in feeding ecology of the earliest stem mammals| journal=Nature| volume=512| issue=7514| pages=303–305| year=2014| last1=Gill| first1=Pamela G.| last2=Purnell| first2=Mark A.| last3=Crumpton| first3=Nick| last4=Brown| first4=Kate Robson| last5=Gostling| first5=Neil J.| last6=Stampanoni| first6=M.| last7=Rayfield| first7=Emily J.| bibcode=2014Natur.512..303G| hdl=2381/29192| hdl-access=free}}</ref>
''Kuehneotherium'' is thought to be an [[insectivore]] that could consume only soft-bodied insects such as moths. Its teeth were shaped for vertical shearing and could not crush harder prey. It lived alongside another early mammaliaform, ''[[Morganucodon]]'', which had teeth that could crush harder insects such as beetles. This distinction in diet shows that early mammaliaforms adapted to have separate feeding niches so they would not compete for food.<ref>Gill, Pam, M.D. Morganucodon – lower jaw of an early mammal, Animal Bytes 13 June 2013. Web. retrieved http://animalbytescambridge.wordpress.com/2013/06/05/morganucodon-lower-jaw-of-an-early-mammal/#comments</ref><ref>{{Cite journal | doi=10.1038/nature13622| pmid=25143112| title=Dietary specializations and diversity in feeding ecology of the earliest stem mammals| journal=Nature| volume=512| issue=7514| pages=303–305| year=2014| last1=Gill| first1=Pamela G.| last2=Purnell| first2=Mark A.| last3=Crumpton| first3=Nick| last4=Brown| first4=Kate Robson| last5=Gostling| first5=Neil J.| last6=Stampanoni| first6=M.| last7=Rayfield| first7=Emily J.| s2cid=4469841| bibcode=2014Natur.512..303G| hdl=2381/29192| hdl-access=free}}</ref>


==Species==
==Species==
Remains of ''Kuehneotherium praecursoris'' have been found in the Pontalun Quarry in a single fissure pocket in [[South Wales]]. The deposit found in limestone is from the Late Triassic. (Whiteside and Marshall 2008) Additional ''Kuehneotherium'' fossils have been found in rock formations of the Early Jurassic of Britain (Somerset), and the Late Triassic of France (Saint-Nicolas-de-Porte), Luxembourg, and Greenland; the ''Kuehneotherium'' specimens for Saint-Nicolas-de-Porte have been named ''K. stanislavi''.<ref>{{cite journal | last1 = Debuysschere | first1 = Maxime | year = 2016 | title = The Kuehneotheriidae (Mammaliaformes) from Saint-Nicolas-de-Port (Upper Triassic, France): a Systematic Review | url = | journal = Journal of Mammalian Evolution | volume = 24| issue = 2| pages = 127–146 | doi = 10.1007/s10914-016-9335-z }}</ref>
Remains of ''Kuehneotherium praecursoris'' have been found in the Pontalun Quarry in a single fissure pocket in [[South Wales]]. The deposit found in limestone is from the Late Triassic. (Whiteside and Marshall 2008) Additional ''Kuehneotherium'' fossils have been found in rock formations of the Early Jurassic of Britain (Somerset), and the Late Triassic of France (Saint-Nicolas-de-Porte), Luxembourg, and Greenland; the ''Kuehneotherium'' specimens for Saint-Nicolas-de-Porte have been named ''K. stanislavi''.<ref name="Debuysschere">{{cite journal | last1 = Debuysschere | first1 = Maxime | s2cid = 20444744 | year = 2017 | title = The Kuehneotheriidae (Mammaliaformes) from Saint-Nicolas-de-Port (Upper Triassic, France): a Systematic Review | journal = Journal of Mammalian Evolution | volume = 24| issue = 2| pages = 127–146 | doi = 10.1007/s10914-016-9335-z }}</ref>


==Paleoenvironment==
==Paleoenvironment==
During the Late Triassic Period the supercontinent [[Pangaea]] was intact, allowing easy interchange and migration of mammals across the connected continents. This explains the wide distribution of ''Kuehneotherium'' fossils found throughout Greenland and Europe. When the continents began to rift apart during the Jurassic, shallow seas covered the British Isles, where ''Kuehneotherium'' was first found. Mammal remains were swept into limestone caves and fissures formed by the shallow seas and were preserved as fossils in [[clastic]] sediment.
During the Late Triassic epoch the supercontinent [[Pangaea]] was intact, allowing easy interchange and migration of animals across the connected continents. This explains the wide distribution of ''Kuehneotherium'' fossils found throughout Greenland and Europe. When the continents began to rift apart during the Jurassic, shallow seas covered the British Isles, where ''Kuehneotherium'' was first found. Its remains were swept into limestone caves and fissures formed by the shallow seas and were preserved as fossils in [[clastic]] sediment.


The climate ''Kuehneotherium'' lived in was hot and dry during this part of the early [[Mesozoic]]. Conifer plants thrived and spread throughout Pangaea. As the continents rifted apart during the Early Jurassic the climate was more humid. Ferns, horsetails, cycads, and mosses were common in both the Triassic and Jurassic, however they were more prevalent in the more humid Jurassic Period.<ref>Benton, Michael J. (2005) "Vertebrate Palaeontology" pg. 138-139, 189-190, and 300-306</ref>
The climate ''Kuehneotherium'' lived in was hot and dry during this part of the early [[Mesozoic]]. Conifer plants thrived and spread throughout Pangaea. As the continents rifted apart during the Early Jurassic the climate was more humid. Ferns, horsetails, cycads, and mosses were common in both the Triassic and Jurassic, however they were more prevalent in the more humid Jurassic period.<ref>Benton, Michael J. (2005) "Vertebrate Palaeontology" pg. 138-139, 189-190, and 300-306</ref>


==Phylogeny==
==Phylogeny==
The [[phylogenetic]] position for ''Kuehneotherium'' has been widely debated. ''Kuehneotherium'' was once classified as a [[theria]]n mammal (the common ancestor of [[marsupials]], [[placentals]], and their descendants). However, additional fossils of [[Basal (phylogenetics)|basal]] mammals have been found that predate the ''Kuehneotherium'' on the geological timescale and the relationships of early mammals were re-evaluated. ''Kuehneotherium'' is now placed in the more basal clade called [[Holotheria]]. Kuehneotherium preacursoris is the earliest mammal categorized as holotherian. Holotheria includes species in which the main and accessory molar cusps are arranged in a triangle. ''Kuehneotherium''’s place in Holotheria is considered unstable, as it is difficult to determine a species characteristics based upon only mandible and dental fragments.<ref name="phylogeny">{{cite journal | last1 = Luo | first1 = Zhe-Xi | last2 = Kielan-Jaworowska | first2 = Zofia | last3 = Cifelli | first3 = Richard L. | year = 2002 | title = In quest for a phylogeny of Mesozoic mammals | url = | journal = Acta Palaeontologica Polonica | volume = 47 | issue = 1| pages = 1–78 }}</ref>
The [[phylogenetic]] position for ''Kuehneotherium'' has been widely debated. ''Kuehneotherium'' was once classified as a [[theria]]n mammal (the common ancestor of [[marsupials]], [[placentals]], and their descendants). However, additional fossils of [[Basal (phylogenetics)|basal]] mammals have been found that predate the ''Kuehneotherium'' on the geological timescale and the relationships of early mammals were re-evaluated. ''Kuehneotherium'' is now placed in the more basal clade called [[Holotheria]]. Kuehneotherium preacursoris is the earliest mammal categorized as holotherian. Holotheria includes species in which the main and accessory molar cusps are arranged in a triangle. ''Kuehneotherium''’s place in Holotheria is considered unstable, as it is difficult to determine a species characteristics based upon only mandible and dental fragments.<ref name="phylogeny">{{cite journal |last1=Luo |first1=Zhe-Xi |last2=Kielan-Jaworowska |first2=Zofia |last3=Cifelli |first3=Richard L. |year=2002 |title=In quest for a phylogeny of Mesozoic mammals |url=https://www.app.pan.pl/article/item/app47-001.html |journal=Acta Palaeontologica Polonica |volume=47 |issue=1 |pages=1–78 |s2cid=80715429 |s2cid-access=free }}</ref>


;Phylogeny ([[Zofia Kielan-Jaworowska]] et al., 2002)
;Phylogeny ([[Zofia Kielan-Jaworowska]] et al., 2002)
{{clade |style=font-size:95%;line-height:80%;
{{clade |style=font-size:95%;line-height:80%;
|label1=''[[Mammaliaformes]]''&nbsp;
|label1=[[Mammaliaformes]]&nbsp;
|1={{clade
|1={{clade
|1=&nbsp;''[[Sinoconodon]]''
|1=&nbsp;''[[Sinoconodon]]''
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|2={{clade
|2={{clade
|1=&nbsp;'''''Kuehneotherium'''''
|1=&nbsp;'''''Kuehneotherium'''''
|2=&nbsp;''[[Mammalia]]''
|2=&nbsp;[[Mammalia]]
}} }} }} }} }} }}
}} }} }} }} }} }}


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''Kuehneotherium'' dentition shows a significant link between [[mammaliaform]] triconodont shaped teeth used for in a puncture-crushing pattern, to modern crown therian molars that chew vertically and chew horizontally.<ref name="phylogeny"/> Therian mammals such as marsupials and placentals shared a common ancestor that was characterized by an upper molar with three main cusps arranged in a triangle that fits into the lower molar that has a reversed triangle and basin-like heel. Later discovery of the earlier more basal mammal [[Woutersia]], provided additional information on this dental transition.<ref>{{cite journal |last1=Godefroit |first1=Pascal |last2=Sigogneau-Russell |first2=Denise |title=Kuehneotheriids from Saint-Nicolas-de-Port (late Triassic of France) |journal=Geologica Belgica |date=1 January 1999 |id={{ProQuest|51112892}} |url=https://popups.uliege.be/1374-8505/index.php?id=1779 }}</ref>
''Kuehneotherium'' dentition shows a significant link between [[mammaliaform]] triconodont shaped teeth used for in a puncture-crushing pattern, to modern crown therian molars that chew vertically and chew horizontally.<ref name="phylogeny"/> Therian mammals such as marsupials and placentals shared a common ancestor that was characterized by an upper molar with three main cusps arranged in a triangle that fits into the lower molar that has a reversed triangle and basin-like heel. Later discovery of the earlier more basal mammal [[Woutersia]], provided additional information on this dental transition.<ref>{{cite journal |last1=Godefroit |first1=Pascal |last2=Sigogneau-Russell |first2=Denise |title=Kuehneotheriids from Saint-Nicolas-de-Port (late Triassic of France) |journal=Geologica Belgica |date=1 January 1999 |id={{ProQuest|51112892}} |url=https://popups.uliege.be/1374-8505/index.php?id=1779 }}</ref>
''Kuehneotherium'', like other mammals had 2 sets of teeth during its life. It is speculated that they may have had up to 6 lower molars with the last molar being added to the back later in life. The evidence for this is that the post canine tooth row shifts backwards as the animal grew. They had 5-6 premolars; the first four premolars are single rooted. Anterior premolars would have been shed in late adulthood and not replaced. The lower jaw is a more basal [[morphology (biology)|morphology]] with a prominent postdentary groove where more developed postdentary bones would attach. The enamel microstructures of ''Kuehneotherium'' teeth were [[synapsid]] columnar enamel characterized by a pattern of columnar, prism-less structures.<ref>{{cite book |last1=Kielan-Jaworowska |first1=Zofia |last2=Cifelli |first2=Richard L. |last3=Luo |first3=Zhe-Xi |title=Mammals from the Age of Dinosaurs: Origins, Evolution, and Structure |date=2005 |publisher=Columbia University Press |isbn=978-0-231-11918-4 }}{{pn|date=July 2020}}</ref>
''Kuehneotherium'', like other mammals had two sets of teeth during its life. It is speculated that they may have had up to six lower molars with the last molar being added to the back later in life. The evidence for this is that the postcanine tooth row shifts backwards as the animal grew. They had 5-6 premolars; the first four premolars are single rooted. Anterior premolars would have been shed in late adulthood and not replaced. The lower jaw is a more basal [[morphology (biology)|morphology]] with a prominent postdentary groove where more developed postdentary bones would attach. The enamel microstructures of ''Kuehneotherium'' teeth were [[synapsid]] columnar enamel characterized by a pattern of columnar, prism-less structures.<ref>{{cite book |last1=Kielan-Jaworowska |first1=Zofia |last2=Cifelli |first2=Richard L. |last3=Luo |first3=Zhe-Xi |title=Mammals from the Age of Dinosaurs: Origins, Evolution, and Structure |date=2005 |publisher=Columbia University Press |isbn=978-0-231-11918-4 |pages=361–362 }}</ref>

==Metabolism==
Alongside ''[[Morganucodon]]'', ''Kuehneotherium'' appears to have had a lower metabolism than modern mammals, having a long lifespan.<ref>{{cite journal |last1=Newham |first1=Elis |last2=Gill |first2=Pamela G. |last3=Brewer |first3=Philippa |last4=Benton |first4=Michael J. |last5=Fernandez |first5=Vincent |last6=Gostling |first6=Neil J. |last7=Haberthür |first7=David |last8=Jernvall |first8=Jukka |last9=Kankaanpää |first9=Tuomas |last10=Kallonen |first10=Aki |last11=Navarro |first11=Charles |last12=Pacureanu |first12=Alexandra |last13=Richards |first13=Kelly |last14=Brown |first14=Kate Robson |last15=Schneider |first15=Philipp |last16=Suhonen |first16=Heikki |last17=Tafforeau |first17=Paul |last18=Williams |first18=Katherine A. |last19=Zeller-Plumhoff |first19=Berit |last20=Corfe |first20=Ian J. |title=Reptile-like physiology in Early Jurassic stem-mammals |journal=Nature Communications |date=12 October 2020 |volume=11 |issue=1 |pages=5121 |doi=10.1038/s41467-020-18898-4|pmc=7550344 |pmid=33046697 |doi-access=free }}</ref>


==See also==
==See also==
Line 58: Line 65:


==Further reading==
==Further reading==
*{{cite journal |last1=Fraser |first1=N. C. |last2=Walkden |first2=G. M. |last3=Stewart |first3=V. |title=The first pre-Rhaetic therian mammal |journal=Nature |date=March 1985 |volume=314 |issue=6007 |pages=161–163 |id={{ProQuest|51337243}} |doi=10.1038/314161a0 }}
*{{cite journal |last1=Fraser |first1=N. C. |last2=Walkden |first2=G. M. |last3=Stewart |first3=V. |s2cid=4280751 |title=The first pre-Rhaetic therian mammal |journal=Nature |date=March 1985 |volume=314 |issue=6007 |pages=161–163 |id={{ProQuest|51337243}} |doi=10.1038/314161a0 |bibcode=1985Natur.314..161F }}
*{{cite book |last1=Gingerich |first1=Philip D. |chapter=Patterns of evolution in the mammalian fossil record |pages=469–500 |chapterurl=https://books.google.com/books?id=q7GjDIyyWegC&pg=PA469 |title=Patterns of evolution, as illustrated by the fossil record |date=1977 |publisher=Elsevier |isbn=978-0-08-086846-2 }}
*{{cite book |last1=Gingerich |first1=Philip D. |chapter=Patterns of evolution in the mammalian fossil record |pages=469–500 |chapter-url=https://books.google.com/books?id=q7GjDIyyWegC&pg=PA469 |title=Patterns of evolution, as illustrated by the fossil record |date=1977 |publisher=Elsevier |isbn=978-0-08-086846-2 }}
*{{cite journal | pmc=1644176 | pmid=5063423 | volume=65 | issue=4 | title=Evolution of mastication | year=1972 | journal=Proc. R. Soc. Med. | pages=392–6 | last1 = Mills | first1 = JR | doi=10.1177/003591577206500440}}
*{{cite journal |last1=Mills |first1=J R E |title=Evolution of Mammalian Dental Structures |journal=Proceedings of the Royal Society of Medicine |date=September 2016 |volume=65 |issue=4 |pages=392–396 |doi=10.1177/003591577206500440 |pmid=5063423 |pmc=1644176 }}
*{{cite journal | last1 = Kermack | first1 = K. A. | year = 1972 | title = The origin of mammals and the evolution of the temporomandibular joint | url = | journal = Proceedings of the Royal Society of Medicine | volume = 65 | issue = 4| pages = 389–92 | pmid = 5063422 | pmc = 1644161 | doi = 10.1177/003591577206500439 }}
*{{cite journal |last1=Kermack |first1=K A |title=Evolution of Mammalian Dental Structures |journal=Proceedings of the Royal Society of Medicine |date=September 2016 |volume=65 |issue=4 |pages=389–392 |doi=10.1177/003591577206500439 |pmid=5063422 |pmc=1644161 }}
*{{cite journal | last1 = Parrington | first1 = F. R. A | year = 1978 | title = Further Account of the Triassic Mammals | url = | journal = Philosophical Transactions of the Royal Society of London B: Biological Sciences | volume = 282 | issue = 989| pages = 177–204 | doi=10.1098/rstb.1978.0012| doi-access = free }}
*{{cite journal |last1=Parrington |first1=Francis Rex |title=A Further Account of the Triassic Mammals |journal=Philosophical Transactions of the Royal Society of London. B, Biological Sciences |date=January 1997 |volume=282 |issue=989 |pages=177–204 |doi=10.1098/rstb.1978.0012 |doi-access= }}
*{{cite journal | last1 = Setoguchi | first1 = T. | last2 = Tsubamoto | first2 = T. | last3 = Hanamura | first3 = H. | last4 = Hachiya | first4 = K. | year = 1999 | title = An early late Cretaceous mammal from Japan, with reconsideration of the Evolution of tribosphenic molars | url = | journal = Paleontological Research | volume = 3 | issue = 1| pages = 18–28 }}
*{{cite journal | last1 = Setoguchi | first1 = T. | last2 = Tsubamoto | first2 = T. | last3 = Hanamura | first3 = H. | last4 = Hachiya | first4 = K. | year = 1999 | title = An early late Cretaceous mammal from Japan, with reconsideration of the Evolution of tribosphenic molars | url = https://www.jstage.jst.go.jp/article/prpsj1997/3/1/3_1_18/_article | journal = Paleontological Research | volume = 3 | issue = 1| pages = 18–28 }}

*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), 361-362.
{{Mammaliaformes|H.}}
{{Cynodontia|M.}}
{{Taxonbar|from=Q6441861}}
{{Taxonbar|from=Q6441861}}


⚫
[[Category:Extinct mammals of Europe]]
[[Category:Mammaliaformes]]
[[Category:Mammaliaformes]]
[[Category:Triassic mammals]]
[[Category:Hettangian genus extinctions]]
[[Category:Jurassic mammals]]
[[Category:Rhaetian genus first appearances]]
⚫
[[Category:Late Triassic synapsids of Europe]]
[[Category:Early Jurassic synapsids of Europe]]
[[Category:Jurassic England]]
[[Category:Jurassic France]]
[[Category:Jurassic Wales]]
[[Category:Fossils of England]]
[[Category:Fossils of France]]
[[Category:Fossils of Luxembourg]]
[[Category:Fossils of Wales]]
[[Category:Fossil taxa described in 1968]]
[[Category:Fossil taxa described in 1968]]

Latest revision as of 19:54, 29 March 2024

Kuehneotherium
Temporal range: Rhaetian-Hettangian
~206–199 Ma
Upper and lower molars of Kuehneotherium
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Therapsida
Clade: Cynodontia
Clade: Mammaliaformes
Family: †Kuehneotheriidae
Genus: †Kuehneotherium
D.M. Kermack et al., 1968
Type species
†Kuehneotherium praecursoris
D.M. Kermack et al., 1968
Other species
  • †K. stanislavi Debuysschere, 2017[1]

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.[2] 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.

Kuehneotherium is thought to be an insectivore that could consume only soft-bodied insects such as moths. Its teeth were shaped for vertical shearing and could not crush harder prey. It lived alongside another early mammaliaform, Morganucodon, which had teeth that could crush harder insects such as beetles. This distinction in diet shows that early mammaliaforms adapted to have separate feeding niches so they would not compete for food.[3][4]

Species[edit]

Remains of Kuehneotherium praecursoris have been found in the Pontalun Quarry in a single fissure pocket in South Wales. The deposit found in limestone is from the Late Triassic. (Whiteside and Marshall 2008) Additional Kuehneotherium fossils have been found in rock formations of the Early Jurassic of Britain (Somerset), and the Late Triassic of France (Saint-Nicolas-de-Porte), Luxembourg, and Greenland; the Kuehneotherium specimens for Saint-Nicolas-de-Porte have been named K. stanislavi.[1]

Paleoenvironment[edit]

During the Late Triassic epoch the supercontinent Pangaea was intact, allowing easy interchange and migration of animals across the connected continents. This explains the wide distribution of Kuehneotherium fossils found throughout Greenland and Europe. When the continents began to rift apart during the Jurassic, shallow seas covered the British Isles, where Kuehneotherium was first found. Its remains were swept into limestone caves and fissures formed by the shallow seas and were preserved as fossils in clastic sediment.

The climate Kuehneotherium lived in was hot and dry during this part of the early Mesozoic. Conifer plants thrived and spread throughout Pangaea. As the continents rifted apart during the Early Jurassic the climate was more humid. Ferns, horsetails, cycads, and mosses were common in both the Triassic and Jurassic, however they were more prevalent in the more humid Jurassic period.[5]

Phylogeny[edit]

The phylogenetic position for Kuehneotherium has been widely debated. Kuehneotherium was once classified as a therian mammal (the common ancestor of marsupials, placentals, and their descendants). However, additional fossils of basal mammals have been found that predate the Kuehneotherium on the geological timescale and the relationships of early mammals were re-evaluated. Kuehneotherium is now placed in the more basal clade called Holotheria. Kuehneotherium preacursoris is the earliest mammal categorized as holotherian. Holotheria includes species in which the main and accessory molar cusps are arranged in a triangle. Kuehneotherium’s place in Holotheria is considered unstable, as it is difficult to determine a species characteristics based upon only mandible and dental fragments.[6]

Phylogeny (Zofia Kielan-Jaworowska et al., 2002)
Mammaliaformes 

Significance to the evolution of mammalian dentition[edit]

Study of the initial development of molar cusp triangulation in Kuehneotherium preacursoris was key in the early understanding of the transition between triconodont and crown therian molars.

Kuehneotherium dentition shows a significant link between mammaliaform triconodont shaped teeth used for in a puncture-crushing pattern, to modern crown therian molars that chew vertically and chew horizontally.[6] Therian mammals such as marsupials and placentals shared a common ancestor that was characterized by an upper molar with three main cusps arranged in a triangle that fits into the lower molar that has a reversed triangle and basin-like heel. Later discovery of the earlier more basal mammal Woutersia, provided additional information on this dental transition.[7] Kuehneotherium, like other mammals had two sets of teeth during its life. It is speculated that they may have had up to six lower molars with the last molar being added to the back later in life. The evidence for this is that the postcanine tooth row shifts backwards as the animal grew. They had 5-6 premolars; the first four premolars are single rooted. Anterior premolars would have been shed in late adulthood and not replaced. The lower jaw is a more basal morphology with a prominent postdentary groove where more developed postdentary bones would attach. The enamel microstructures of Kuehneotherium teeth were synapsid columnar enamel characterized by a pattern of columnar, prism-less structures.[8]

Metabolism[edit]

Alongside Morganucodon, Kuehneotherium appears to have had a lower metabolism than modern mammals, having a long lifespan.[9]

See also[edit]

References[edit]

  1. ^ a b Debuysschere, Maxime (2017). "The Kuehneotheriidae (Mammaliaformes) from Saint-Nicolas-de-Port (Upper Triassic, France): a Systematic Review". Journal of Mammalian Evolution. 24 (2): 127–146. doi:10.1007/s10914-016-9335-z. S2CID 20444744.
  2. ^ Kermack, Doris M.; Kermack, K.A.; Mussett, Frances (1968). "The Welsh pantothere Kuehneotherium praecursoris". Journal of the Linnean Society of London, Zoology. 47 (312): 407–423. doi:10.1111/j.1096-3642.1968.tb00519.x.
  3. ^ Gill, Pam, M.D. Morganucodon – lower jaw of an early mammal, Animal Bytes 13 June 2013. Web. retrieved http://animalbytescambridge.wordpress.com/2013/06/05/morganucodon-lower-jaw-of-an-early-mammal/#comments
  4. ^ Gill, Pamela G.; Purnell, Mark A.; Crumpton, Nick; Brown, Kate Robson; Gostling, Neil J.; Stampanoni, M.; Rayfield, Emily J. (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.
  5. ^ Benton, Michael J. (2005) "Vertebrate Palaeontology" pg. 138-139, 189-190, and 300-306
  6. ^ a b Luo, Zhe-Xi; Kielan-Jaworowska, Zofia; Cifelli, Richard L. (2002). "In quest for a phylogeny of Mesozoic mammals". Acta Palaeontologica Polonica. 47 (1): 1–78. S2CID 80715429.
  7. ^ Godefroit, Pascal; Sigogneau-Russell, Denise (1 January 1999). "Kuehneotheriids from Saint-Nicolas-de-Port (late Triassic of France)". Geologica Belgica. ProQuest 51112892.
  8. ^ Kielan-Jaworowska, Zofia; Cifelli, Richard L.; Luo, Zhe-Xi (2005). Mammals from the Age of Dinosaurs: Origins, Evolution, and Structure. Columbia University Press. pp. 361–362. ISBN 978-0-231-11918-4.
  9. ^ Newham, Elis; Gill, Pamela G.; Brewer, Philippa; Benton, Michael J.; Fernandez, Vincent; Gostling, Neil J.; Haberthür, David; Jernvall, Jukka; Kankaanpää, Tuomas; Kallonen, Aki; Navarro, Charles; Pacureanu, Alexandra; Richards, Kelly; Brown, Kate Robson; Schneider, Philipp; Suhonen, Heikki; Tafforeau, Paul; Williams, Katherine A.; Zeller-Plumhoff, Berit; Corfe, Ian J. (12 October 2020). "Reptile-like physiology in Early Jurassic stem-mammals". Nature Communications. 11 (1): 5121. doi:10.1038/s41467-020-18898-4. PMC 7550344. PMID 33046697.

Further reading[edit]

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