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The clade Australosphenida was proposed by Luo ''et al.'' (2001, 2002) and was initially left unranked, as the authors do not apply the [[Linnaean taxonomy|Linnaean hierarchy]]. In Benton (2005), it is ranked as a '[[Linnaean taxonomy#Taxonomic ranks|superdivision]]', i.e. one or two levels below the [[infraclass]]. |
The clade Australosphenida was proposed by Luo ''et al.'' (2001, 2002) and was initially left unranked, as the authors do not apply the [[Linnaean taxonomy|Linnaean hierarchy]]. In Benton (2005), it is ranked as a '[[Linnaean taxonomy#Taxonomic ranks|superdivision]]', i.e. one or two levels below the [[infraclass]]. |
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== Australosphenid teeth == |
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The grouping embodies a hypothesis about the evolution of [[molar (tooth)|molar]] teeth in mammals. Living monotremes are toothless as adults, but the juvenile platypus, fossil monotremes and Ausktribosphenida all share a pattern of three molar [[cusp (dentistry)|cusps]] arranged in a triangle or V shape, which is known as the [[Tribosphenic molar|tribosphenic]] type of molar. Tribosphenic molars have long been held to characterize the subclass [[Theria]] ([[marsupial]]s, [[placental]]s and their extinct relatives), while monotremes were thought to be related to fossil groups with a linear alignment of cusps: [[morganucodon]]tids, [[docodont]]s, [[triconodont]]s and [[multituberculate]]s, all of which were united with the monotremes into the 'subclass [[Prototheria]]'. Defined in this way, the 'Prototheria' is no longer recognised as a valid clade, since the linear cusp pattern is a primitive condition within Mammalia and cannot supply the shared derived character, which is required to establish a subgroup. Instead, the available evidence suggests that the monotremes descend from a [[Mesozoic]] radiation of tribosphenic mammals in the southern continents (hence the name Australosphenida, meaning 'southern wedges'), but this interpretation is highly controversial. |
The grouping embodies a hypothesis about the evolution of [[molar (tooth)|molar]] teeth in mammals. Living monotremes are toothless as adults, but the juvenile platypus, fossil monotremes and Ausktribosphenida all share a pattern of three molar [[cusp (dentistry)|cusps]] arranged in a triangle or V shape, which is known as the [[Tribosphenic molar|tribosphenic]] type of molar. Tribosphenic molars have long been held to characterize the subclass [[Theria]] ([[marsupial]]s, [[placental]]s and their extinct relatives), while monotremes were thought to be related to fossil groups with a linear alignment of cusps: [[morganucodon]]tids, [[docodont]]s, [[triconodont]]s and [[multituberculate]]s, all of which were united with the monotremes into the 'subclass [[Prototheria]]'. Defined in this way, the 'Prototheria' is no longer recognised as a valid clade, since the linear cusp pattern is a primitive condition within Mammalia and cannot supply the shared derived character, which is required to establish a subgroup. Instead, the available evidence suggests that the monotremes descend from a [[Mesozoic]] radiation of tribosphenic mammals in the southern continents (hence the name Australosphenida, meaning 'southern wedges'), but this interpretation is highly controversial. |
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Greek: Ά ά Έ έ Ή ή Ί ί Ό ό Ύ ύ Ώ ώ Α α Β β Γ γ Δ δ Ε ε Ζ ζ Η η Θ θ Ι ι Κ κ Λ λ Μ μ Ν ν Ξ ξ Ο ο Π π Ρ ρ Σ σ ς Τ τ Υ υ Φ φ Χ χ Ψ ψ Ω ω {{Polytonic|}}
Cyrillic: А а Б б В в Г г Ґ ґ Ѓ ѓ Д д Ђ ђ Е е Ё ё Є є Ж ж З з Ѕ ѕ И и І і Ї ї Й й Ј ј К к Ќ ќ Л л Љ љ М м Н н Њ њ О о П п Р р С с Т т Ћ ћ У у Ў ў Ф ф Х х Ц ц Ч ч Џ џ Ш ш Щ щ Ъ ъ Ы ы Ь ь Э э Ю ю Я я ́
IPA: t̪ d̪ ʈ ɖ ɟ ɡ ɢ ʡ ʔ ɸ β θ ð ʃ ʒ ɕ ʑ ʂ ʐ ç ʝ ɣ χ ʁ ħ ʕ ʜ ʢ ɦ ɱ ɳ ɲ ŋ ɴ ʋ ɹ ɻ ɰ ʙ ⱱ ʀ ɾ ɽ ɫ ɬ ɮ ɺ ɭ ʎ ʟ ɥ ʍ ɧ ʼ ɓ ɗ ʄ ɠ ʛ ʘ ǀ ǃ ǂ ǁ ɨ ʉ ɯ ɪ ʏ ʊ ø ɘ ɵ ɤ ə ɚ ɛ œ ɜ ɝ ɞ ʌ ɔ æ ɐ ɶ ɑ ɒ ʰ ʱ ʷ ʲ ˠ ˤ ⁿ ˡ ˈ ˌ ː ˑ ̪ {{IPA|}}
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