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Largest Mesozoic Mammals

June 12, 2016

Schowalteria clemensi: Known only from one skull, but seems comparable to latter taeniodonts in size, ranging somewhere between 10 to 50 kg. A specialised herbivore.

2. Bubodens magnus: Represented by a single tooth. It is enormous by multituberculate standards, and probably indicative of an animal above 16 kg (it is described as “beaver sized”). Presumably a specialised herbivore.

3. Repenomamus giganticus: Only “giant” Mesozoic mammal known from fairly good material. Measuring about a meter long and weighting at least up to 14 kg. A specialised carnivore.

4. Kollikodon ritchiei: Conflicting sources on this one. It may have been up to a meter long, certainly putting it above R. giganticus (monotremes are proportionally much more robust), but some sources also list it as “platypus size”. A molluscivore or piscivore.

5. Oxlestes grandis: Possibly slightly smaller than R. giganticus. There is some debate about how large its skull was (10 vs 7.5 centimeters), though the former seems to be the most convincing measurements for now. A carnivore.

6. Khuduklestes bohlini: “Subequal” in size to O. grandis. Possibly carnivorous.

7. Mesungulatids: Most sources are rather vague on estimated sizes (in part due to the lack of modern analogues, in part due to how rare postcranial material is), but the larger forms likeColoniatherium seem to be around 6-13 kg. Specialised herbivores.

8. Vintana sertichi: Known from only one skull. Estimated to be around 9 kilos. Specialised herbivore.

9. Altacreodus magnus: Known from various specimens. At around 9 kilos, it is the largest of the Hell Creek mammals. Specialised carnivore.

10. Didelphodon vorax: Known from several remains. The largest of the Hell Creek metatherians at 6-9 kilos. Molluscivore or carnivore.

6 Comments leave one →
  1. June 22, 2016 12:27 am

    I think your article needs some corrections, contrary to what was previously written in Wikipedia, Schowalteria clemensi is never compared in size to latter taeniodonts by Fox and Naylor (2003) but to Didelphodon vorax and “Cimolestes” magnus, which you say were 6-9kg, however I do wonder what is the source of those estimates, Scott and Fox (2015) mention that Altacreodus magnus weighted 0.6kg.

    Using relatives I estimate the mandible of Schowalteria clemensi at ~69mm long, inferior in size to Rapenomamus robustus, which was, realistically 2kg (It is pretty logical that averaging skull and head-body length estimates for an animal known to be big-headed is inevitably going to result in an overestimate, even the head-body length estimate would be exaggerated by the big head, the same applies to 14kg for R. giganticus.)

    In regards to Oxlestes grandis, what makes the former estimate more convincing? Do note that the claim in Wikipedia of recent contesting of the estimate by Averianov and Archibald (2005) is completely made up (I checked the reference provided). Even then, a 10cm skull is not “slightly smaller” than that of R. giganticus, but rather indicative of an animal 1/4th its size assuming similar proportions.

    At last, Kollikodon ritchiei, the Wikipedia article seems to be the origin of the claim that this animal was 1m long and none of the sources in that article mention such estimate, two of them (out of 3), including the initial description, call it platypus-sized.

    • June 22, 2016 11:46 am

      Interesting. On Schowalteria’s size, it was admitely hearsay on some third party sources, that deem it “larger than Repenomamus”.

      Averianov et al 2005 has been contested numerous times (not surprisingly, but that’s a story for another day), given the methodology utilised.

      • June 24, 2016 6:48 pm

        Yeah, the methodology itself is not bad but the animal they used for comparison was, definitely. I’m interested in what publications specifically address the problems with the estimate of Averianov et al. (2005), the one provided in Wikipedia didn’t mention it.

    • June 22, 2016 11:52 am

      See also “Mammalian palaeobiology: Living large in the Cretaceous”, where some of the claims for Svjowalteria and Kollikodon may have originated

  2. Johannes Hilmes permalink
    September 26, 2016 3:25 pm

    What about Nanocuris?

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