by Qem | 2025-04-01 12:33:03+00:00
> Here, eight fragments of megafauna teeth from the Brazilian Intertropical Region were dated, in the locations of Itapipoca (Ceará State) and the Rio Miranda valley (Mato Grosso do Sul State), with the respective ages: Itapipoca – Eremotherium laurillardi (PDR-01: age = 6,161 ± 364 RC years BP; PDR-02: age = 7,415 ± 167 RC years BP), Smilodon populator (PDR-03: age = 7,803 ± 179 RC years BP), Toxodon platensis (PDR-05: age = 7,804 ± 226 RC years BP), Xenorhinotherium bahiense (PDR-06: age = 3,587 ± 112 RC years BP), Notiomastodon platensis (PDR-07: age = 7,940 ± 502 RC years BP) and Palaeolama major (PDR-09: age = 3,492 ± 165 RC years BP); Miranda river - Eremotherium laurillardi (PDR-11: age = 5,942 ± 294 RC years BP).

It appears they hit the jackpot here. Some of those ages are incredibly recent, specially for Eremotherium laurillardi[1] (5-ton giant ground sloth), ~5,900 years BP, Palaeolama major[2] (relative of current llamas, but larger) and Xenorhinotherium bahiense[3] (closely related to alien-looking macrauchenias[4], perhaps same species), both ~3,500 years BP. Please note those ages are not counted from the more familiar anno Domini (AD), before Christ (BC) or before common era (BCE) reference point, but directly before present (BP). For comparison, the Great Pyramid of Giza[5] was built circa 2600 before Christ, or 4,600 BP.

So, in addition to the mammoths stranded in Wrangel island[6], there were also remnants of american continental megafauna that survived the end of the ice age and were alive up to historical times. Awesome. I hope they manage to recover some well preserved DNA samples, whole genomes if possible, from these more recent fossils as well. I wish they had discussed this possibility in the paper.

While I'm excited with this discovery, it depresses me a bit to know those creatures were so close to being contemporary to us living right now, but yet they didn't make it. Some of them at least left smaller closely related species alive today, like three-toed tree sloths surviving giant sloths, from which they diverged some 30 Myr ago[7], even the humble house cat shares a common ancestor with Smilodon (saber-toothed tiger) from some 20 Myr ago[8], and between elephants and mammoths, 6 Myr ago[9]. But the loss of the macraucheniids was worse by comparison, as they probably didn't leave any surviving relative that shared a common ancestor less than 60 Myr ago[10], almost all the way back to the time of the dinosaurs. So, when the last Xenorhinotherium bahiense died circa 3,500 years ago, the litopterna order[11] died with it, and instead of losing a single leave, the tree of life lost a whole branch.

[1] https://en.wikipedia.org/wiki/Eremotherium

[2] https://en.wikipedia.org/wiki/Palaeolama

[3] https://en.wikipedia.org/wiki/Xenorhinotherium

[4] https://en.wikipedia.org/wiki/Macrauchenia

[5] https://en.wikipedia.org/wiki/Great_Pyramid_of_Giza

[6] https://en.wikipedia.org/wiki/Wrangel_Island

[7] https://www.sciencedirect.com/science/article/pii/S096098221...

[8] https://pmc.ncbi.nlm.nih.gov/articles/PMC7612286/pdf/openres...

[9] https://www.pnas.org/doi/pdf/10.1073/pnas.1720554115

[10] https://www.nature.com/articles/ncomms15951.pdf

[11] https://en.wikipedia.org/wiki/Litopterna