Khankhuuluu, new tyrannosauroid from Upper Cretaceous of Mongolia

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Ben Creisler

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Jun 11, 2025, 12:09:23 PMJun 11
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Ben Creisler

A new paper:

Khankhuuluu mongoliensis gen. et sp. nov.

Jared T. Voris, Darla K. Zelenitsky, Yoshitsugu Kobayashi, Sean P. Modesto, François Therrien, Hiroki Tsutsumi, Tsogtbaatar Chinzorig & Khishigjav Tsogtbaatar (2025)
A new Mongolian tyrannosauroid and the evolution of Eutyrannosauria
Nature (advance online publication)
doi: https://doi.org/10.1038/s41586-025-08964-6
https://www.nature.com/articles/s41586-025-08964-6


Eutyrannosaurians were large predatory dinosaurs that dominated Asian and North American terrestrial faunas in latest Cretaceous times. These apex predators arose from smaller-bodied tyrannosauroids during the ‘middle’ Cretaceous that are poorly known owing to the paucity of fossil material. Here we report on a new tyrannosauroid, Khankhuuluu mongoliensis gen. et sp. nov., from lower Upper Cretaceous deposits of Mongolia that provides a new perspective on eutyrannosaurian origins and evolution. Phylogenetic analyses recover Khankhuuluu immediately outside Eutyrannosauria and recover the massive, deep-snouted Tyrannosaurini and the smaller, gracile, shallow-snouted Alioramini as highly derived eutyrannosaurian sister clades. Khankhuuluu and the late-diverging Alioramini independently share features related to a shallow skull and gracile build with juvenile eutyrannosaurians, reinforcing the key role heterochrony had in eutyrannosaurian evolution. Although eutyrannosaurians were mainly influenced by peramorphosis or accelerated growth, Alioramini is revealed as a derived lineage that retained immature features through paedomorphosis and is not a more basal lineage as widely accepted. Our results reveal that Asian tyrannosauroids (similar to Khankhuuluu) dispersed to North America, giving rise to Eutyrannosauria in the mid-Late Cretaceous. Eutyrannosauria diversified and remained exclusively in North America until a single dispersal to Asia in the latest Cretaceous that established Alioramini and Tyrannosaurini. Stark morphological differences between Alioramini and Tyrannosaurini probably evolved due to divergent heterochronic trends—paedomorphosis versus peramorphosis, respectively—allowing them to coexist in Asia and occupy different ecological niches.

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Mickey Mortimer

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Jun 12, 2025, 9:12:05 AMJun 12
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Funny that within that long abstract they couldn't say the one thing that puts Khankhuuluu in context to theropod workers- that it's not new, but rather Perle's 1977 supposed Alectrosaurus skeletons that became the de facto exemplars of the taxon until Carr's 2005 thesis redescribing the holotype. "The maxilla, dentary and jugal ... could not be relocated for this study." Sad.

And it emerges just one node closer to eutyrannosaurs than Alectrosaurus in their phylogeny, showing Perle wasn't that off.  The only difference from Alectrosaurus noted is "metatarsal III lacks the hyperextension of the plantar distal articular surface."

Mickey Mortimer

Thomas Richard Holtz

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Jun 12, 2025, 9:16:02 AMJun 12
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Mickey writes:
> Funny that within that long abstract they couldn't say the one thing that puts Khankhuuluu in context to theropod workers- 
> that it's not new, but rather Perle's 1977 supposed Alectrosaurus skeletons that became the de facto exemplars of the taxon 
> until Carr's 2005 thesis redescribing the holotype. "The maxilla, dentary and jugal ... could not be relocated for this study." Sad.

Indeed. You have to go several paragraphs in to find out this "new" specimen is the mysterious cf. Alectrosaurus material of Perle!

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Tim Williams

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Jun 13, 2025, 1:24:00 AMJun 13
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Mickey Mortimer <therizino...@gmail.com> wrote:

> And it emerges just one node closer to eutyrannosaurs than Alectrosaurus in their phylogeny, showing Perle wasn't that off.  The only difference from Alectrosaurus noted is "metatarsal III lacks the hyperextension of the plantar distal 
> articular surface."

Is this character included in the 'Phylogenetic Character List of Tyrannosauroidea' (e.g., is it covered by #362??).

Although not the raison d'etre of the study, the supplementary information weighs in other issues concerning tyrannosaur(o)id taxonomy:
_Nanotyrannus lancensis_ is regarded as a junior synonym of _Tyrannosaurus rex_.  (Voris &c even have an explanation for the reduction in tooth count.)
_T. mcraensis_ is also sunk into _T. rex_, because the allegedly diagnostic characters of the former are covered by intraspecific variation in the latter. 
_Daspletosaurus wilsoni_ is sunk into _D. torosus_, for similar reasons.
A trio of Asian genera are proposed to be likely or possible junior synonyms of _Tarbosaurus bataar_: these are _Raptorex_, _Jinbeisaurus_, and _Asiatyrannus_.  Like _Shanshanosaurus_ and _Maleevosaurus_ before them, they are regarded as immature specimens.  
(Note that earlier this year, Cau and Paterna regarded _Sinotyrannus_ as a junior synonym of _Huaxiagnathus_, with the latter based on an immature specimen.)
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