Triconodon ("three-coned tooth") is a genus of extinct mammal from the Early Cretaceous of England and France with two known species: T. mordax and T. averianovi. First described in 1859 by Richard Owen,[1] it is the type genus for the order Triconodonta, a group of mammals characterised by their three-cusped (triconodont) molarteeth. Since then, this "simplistic" type of dentition has been understood to be either ancestral for mammals or else to have evolved multiple times, rendering "triconodonts" a paraphyletic or polyphyletic assemblage respectively, but several lineages of "triconodont" mammals do form a natural, monophyletic group, known as Eutriconodonta, of which Triconodon is indeed part of.
Triconodon, therefore, is significant in the understanding of the evolution of mammals by originating the understanding of the "triconodont" grade and eutriconodont clade. Further discoveries on its skeletal anatomy also offer further insights on the palaeobiology of Mesozoic mammals.[2]
The type specimen of Triconodon is BMNH 47764, a single mandible found in the Purbeck Group, England, pertaining to the type species (T. mordax).[1] Since then, several other specimens have been found in this region, mostly represented by skulls and jaws, making it the most common mammal fossils in this area of Britain.[2] These deposits date to the earliest Cretaceous, to the Berriasian at around 145-140 million years of age. The second species, T. averianovi, was named in 2020 based on fossils found in the Berriasian-aged Lulworth Formation, England.[3]
A single specimen has also been found in the Champblanc Quarry in France, dating to roughly the same age. It is unclear if it belongs to the same species as the British form, though given the close temporal and geographical proximity it seems likely.[4]
ClassificationEdit
Triconodon is known from two species, represented only by T. averianovi and T. mordax (though see above). Besides being the type genus and species for Eutriconodonta as seen above, it is also the type genus and species for Triconodontidae, erected in 1887 by Charles Marsh.[5] Within this group it is usually recovered in a basal position, sometimes as sister taxa to Trioracodon,[6][7] or closer to the group containing the rest of the clade, rendering Trioracodon in the basalmost position.[8]
BiologyEdit
Like most eutriconodonts, Triconodon was probably a carnivore, its triconodont teeth being well adapted for shearing, and possessing other speciations such as long canines and powerful jaw musculature.[2] It was about as large as a modern cat, suggesting that it hunted vertebrate prey such as other mammals or small dinosaurs.[9] A study detailing Mesozoic mammal diets ranks it among carnivorous taxa.[10]
Tooth replacementEdit
Triconodon is one of the few Mesozoic mammals with direct evidence of tooth eruption, thanks to a broad ontogenetic range presented by the specimens. Through several juvenile specimens we can document the replacement of its lower fourth premolar, erupting and coming into use when at least three out of its four molars were already fully erupted.[11]
BrainEdit
One of the earliest fossil brain endocast studies has been performed for Triconodon.[11] The olfactory lobe is large, with a teardrop-shaped outline, suggesting a well developed sense of smell.
The cerebral hemisphere is long, oval and flat, lacking the inflated appearance present in monotremes, multituberculates and therians. The cerebrum is neither expanded anteriorly to overlap the posterior part of the olfactory lobe, nor is it hemispherical. It is similar to that of multituberculates in that it has a large, roughly triangular bulge, now thought to be the superior cistern. The midbrain was apparently exposed to the dorsal side of the brain as with many other non-therian mammals.[2]
What this indicates about the animal's intelligence is currently unclear, though its overall brain proportions are somewhat smaller than those of more derived mammals like multituberculates and therians.[12]
^ abcdZofia Kielan-Jaworowska, Richard L. Cifelli, Zhe-Xi Luo (2004). "Chapter 7: Eutriconodontans". Mammals from the Age of Dinosaurs: origins, evolution, and structure. New York: Columbia University Press. pp. 216–248. ISBN0-231-11918-6.{{cite book}}: CS1 maint: multiple names: authors list (link)
^Kai R. K. Jäger; Richard L. Cifelli; Thomas Martin (2020). "Tooth eruption in the Early Cretaceous British mammal Triconodon and description of a new species". Papers in Palaeontology. 7 (2): 1065–1080. doi:10.1002/spp2.1329.
^J. Pouech, J.-M. Mazin, and J.-P. Billon-Bruyat. 2006. Microvertebrate biodiversity from Cherves-de-Cognac (Lower Cretaceous, Berriasian: Charente, France). 9th International Symposium on Mesozoic Terrestrial Ecosystems and Biota, Abstracts and Proceedings Volume 96-100
^O. C. Marsh. 1887. American Jurassic mammals. The American Journal of Science, series 3 33(196):327-348
^Marisol Montellano; James A. Hopson; James M. Clark (2008). "Late Early Jurassic Mammaliaforms from Huizachal Canyon, Tamaulipas, México". Journal of Vertebrate Paleontology 28 (4): 1130–1143. doi:10.1671/0272-4634-28.4.1130.
^Chun-Ling Gao, Gregory P. Wilson, Zhe-Xi Luo, A. Murat Maga, Qingjin Meng and Xuri Wang (2010). "A new mammal skull from the Lower Cretaceous of China with implications for the evolution of obtuse-angled molars and ‘amphilestid’ eutriconodonts". Proceedings of the Royal Society B: Biological Sciences 277 (1679): 237–246. doi:10.1098/rspb.2009.1014. PMC 2842676. PMID 19726475.
^Thomas Martin, Jesús Marugán-Lobón, Romain Vullo, Hugo Martín-Abad, Zhe-Xi Luo & Angela D. Buscalioni (2015). A Cretaceous eutriconodont and integument evolution in early mammals. Nature 526, 380–384. doi:10.1038/nature14905
^David M. Grossnickle, P. David Polly, Mammal disparity decreases during the Cretaceous angiosperm radiation, Published 2 October 2013. doi:10.1098/rspb.2013.2110
^ abG. G. Simpson. 1928. A Catalogue of the Mesozoic Mammalia in the Geological Department of the British Museum 1-215
^Harry Jerison, Evolution of The Brain and Intelligence, 02/12/2012
October 21, 2023
triconodon, three, coned, tooth, genus, extinct, mammal, from, early, cretaceous, england, france, with, known, species, mordax, averianovi, first, described, 1859, richard, owen, type, genus, order, group, mammals, characterised, their, three, cusped, tricono. Triconodon three coned tooth is a genus of extinct mammal from the Early Cretaceous of England and France with two known species T mordax and T averianovi First described in 1859 by Richard Owen 1 it is the type genus for the order Triconodonta a group of mammals characterised by their three cusped triconodont molar teeth Since then this simplistic type of dentition has been understood to be either ancestral for mammals or else to have evolved multiple times rendering triconodonts a paraphyletic or polyphyletic assemblage respectively but several lineages of triconodont mammals do form a natural monophyletic group known as Eutriconodonta of which Triconodon is indeed part of TriconodonTemporal range Berriasian 145 140 Ma PreꞒ Ꞓ O S D C P T J K Pg N Triconodon mordax jaw Richard Owen 1861Scientific classificationDomain EukaryotaKingdom AnimaliaPhylum ChordataClass MammaliaClade EutriconodontaFamily TriconodontidaeGenus TriconodonOwen 1859Type species Triconodon mordaxOwen 1859Other species T averianovi Jager Cifelli amp Martin 2020SynonymsTriacanthodon Owen 1871Triconodon therefore is significant in the understanding of the evolution of mammals by originating the understanding of the triconodont grade and eutriconodont clade Further discoveries on its skeletal anatomy also offer further insights on the palaeobiology of Mesozoic mammals 2 Contents 1 Discovery 2 Classification 3 Biology 3 1 Tooth replacement 3 2 Brain 4 ReferencesDiscovery EditThe type specimen of Triconodon is BMNH 47764 a single mandible found in the Purbeck Group England pertaining to the type species T mordax 1 Since then several other specimens have been found in this region mostly represented by skulls and jaws making it the most common mammal fossils in this area of Britain 2 These deposits date to the earliest Cretaceous to the Berriasian at around 145 140 million years of age The second species T averianovi was named in 2020 based on fossils found in the Berriasian aged Lulworth Formation England 3 A single specimen has also been found in the Champblanc Quarry in France dating to roughly the same age It is unclear if it belongs to the same species as the British form though given the close temporal and geographical proximity it seems likely 4 Classification EditTriconodon is known from two species represented only by T averianovi and T mordax though see above Besides being the type genus and species for Eutriconodonta as seen above it is also the type genus and species for Triconodontidae erected in 1887 by Charles Marsh 5 Within this group it is usually recovered in a basal position sometimes as sister taxa to Trioracodon 6 7 or closer to the group containing the rest of the clade rendering Trioracodon in the basalmost position 8 Biology EditLike most eutriconodonts Triconodon was probably a carnivore its triconodont teeth being well adapted for shearing and possessing other speciations such as long canines and powerful jaw musculature 2 It was about as large as a modern cat suggesting that it hunted vertebrate prey such as other mammals or small dinosaurs 9 A study detailing Mesozoic mammal diets ranks it among carnivorous taxa 10 Tooth replacement Edit Triconodon is one of the few Mesozoic mammals with direct evidence of tooth eruption thanks to a broad ontogenetic range presented by the specimens Through several juvenile specimens we can document the replacement of its lower fourth premolar erupting and coming into use when at least three out of its four molars were already fully erupted 11 Brain Edit One of the earliest fossil brain endocast studies has been performed for Triconodon 11 The olfactory lobe is large with a teardrop shaped outline suggesting a well developed sense of smell The cerebral hemisphere is long oval and flat lacking the inflated appearance present in monotremes multituberculates and therians The cerebrum is neither expanded anteriorly to overlap the posterior part of the olfactory lobe nor is it hemispherical It is similar to that of multituberculates in that it has a large roughly triangular bulge now thought to be the superior cistern The midbrain was apparently exposed to the dorsal side of the brain as with many other non therian mammals 2 What this indicates about the animal s intelligence is currently unclear though its overall brain proportions are somewhat smaller than those of more derived mammals like multituberculates and therians 12 References Edit a b R Owen 1859 Palaeontology Encyclopedia Britannica 8th ed 17 91 176 P Wagner P Wagner a b c d Zofia Kielan Jaworowska Richard L Cifelli Zhe Xi Luo 2004 Chapter 7 Eutriconodontans Mammals from the Age of Dinosaurs origins evolution and structure New York Columbia University Press pp 216 248 ISBN 0 231 11918 6 a href Template Cite book html title Template Cite book cite book a CS1 maint multiple names authors list link Kai R K Jager Richard L Cifelli Thomas Martin 2020 Tooth eruption in the Early Cretaceous British mammal Triconodon and description of a new species Papers in Palaeontology 7 2 1065 1080 doi 10 1002 spp2 1329 J Pouech J M Mazin and J P Billon Bruyat 2006 Microvertebrate biodiversity from Cherves de Cognac Lower Cretaceous Berriasian Charente France 9th International Symposium on Mesozoic Terrestrial Ecosystems and Biota Abstracts and Proceedings Volume 96 100 O C Marsh 1887 American Jurassic mammals The American Journal of Science series 3 33 196 327 348 Marisol Montellano James A Hopson James M Clark 2008 Late Early Jurassic Mammaliaforms from Huizachal Canyon Tamaulipas Mexico Journal of Vertebrate Paleontology 28 4 1130 1143 doi 10 1671 0272 4634 28 4 1130 Chun Ling Gao Gregory P Wilson Zhe Xi Luo A Murat Maga Qingjin Meng and Xuri Wang 2010 A new mammal skull from the Lower Cretaceous of China with implications for the evolution of obtuse angled molars and amphilestid eutriconodonts Proceedings of the Royal Society B Biological Sciences 277 1679 237 246 doi 10 1098 rspb 2009 1014 PMC 2842676 PMID 19726475 Thomas Martin Jesus Marugan Lobon Romain Vullo Hugo Martin Abad Zhe Xi Luo amp Angela D Buscalioni 2015 A Cretaceous eutriconodont and integument evolution in early mammals Nature 526 380 384 doi 10 1038 nature14905 Triconodon fossil mammal genus David M Grossnickle P David Polly Mammal disparity decreases during the Cretaceous angiosperm radiation Published 2 October 2013 doi 10 1098 rspb 2013 2110 a b G G Simpson 1928 A Catalogue of the Mesozoic Mammalia in the Geological Department of the British Museum 1 215 Harry Jerison Evolution of The Brain and Intelligence 02 12 2012 Retrieved from https en wikipedia org w index php title Triconodon amp oldid 1173353063, wikipedia, wiki, book, books, library,
