A paper came out recently describing a new genus of mammal. Named Patagomaia, it was noted for three reasons. First, it was found in Cretaceous rocks, which puts it in the same layers of rocks where dinosaurs are found. Second, it was large for a mammal, at least, compared to most mammals found alongside dinosaurs, having an estimated mass of 14 kg. This was no “squirrel” running and chattering among the trees: it was closer to the size of a small dog. Finally, it was classified as a therian.[1] Theria is the broad group of mammals that includes the placentals and marsupials but excludes other mammals, such as monotremes (platypus and echidna). In other words, it is more “advanced” compared to most other mammals found alongside dinosaurs.
It may be appealing to take Patagomaia and use it to “take down” the theory of evolution. After all, it is a large creature that belongs to the group of living mammals and it is found alongside dinosaurs. In contrast, the evolutionary narrative has claimed that dinosaurs were so successful, they dominated the world and forced mammals to remain small, insignificant, and primitive for the duration of their reign. Patagomaia destroys that entire narrative, right?
Not quite. First, the narrative of dinosaurs dominating mammals is not as simple as we may think. For one, it has been acknowledged for a long time that therians lived alongside dinosaurs. Marsupials and even placentals have long been acknowledged to be found in layers of rock containing dinosaurs.[2] Thus, in the evolutionary narrative, mammals were evolving and advancing under the feet of the dinosaurs: they were not stagnant and suppressed. In fact, one author actually suggested that while dinosaurs dominated the mid- to large sized classes of animals, mammals dominated the small sized classes of animals.[3] In other words, mammals were not so much suppressed as they were dominating their own domain.
The issue is further complicated because evolutionists have been reluctant to talk about the “domination” of dinosaurs over mammals. Sure, the thought comes up in textbooks,[4] but when it is, it is given as a single sentence with no elaboration. There is no reference to studies of how and why dinosaurs dominated mammals, there is just a passing comment that it appears that is what happened. Other textbooks do not mention the domination of dinosaurs over mammals at all.[5] What these observations indicate is that dinosaur domination over mammals is not a key tenant of the theory of evolution. The theory of evolution does not hang on the “fact” of dinosaur domination. I would describe the difference as predictive versus observational. The theory of evolution does not predict that dinosaurs dominated mammals. Rather, scientists observed that mammal fossils found alongside dinosaurs were small and so concluded that dinosaurs may have dominated mammals. When the observations changed, the idea was free to change with it, without affecting the theory of evolution.
By the way, Patagomaia did not break any molds for mammals. As already mentioned, it has been acknowledged that therians lived alongside dinosaurs, so Patagomaia did not upset that trend. As for its size, it did not upset the trend of “small mammals” either. That trend was broken back in 2005 with the naming of Repenomamus giganticus. This large mammal was found with the remains of small dinosaurs in its stomach, not only demonstrating that there were large mammals found alongside dinosaurs, but that some of them were large enough to prey on dinosaurs. With an estimated body mass of 12 to 14 kilograms,[6] Repenomamus giganticus was in the same size range as Patagomaia.
One more thing to note about Patagomaia: its remains are fragmentary. Very fragmentary. That is why it is classified as a therian and not as a marsupial or a placental: there are not enough details from its skeleton to tell which one it is.[7]
Thus we have a fragmentary, unidentifiable mammal of an unusually large size for a Mesozoic mammal. It does not break any trends or molds and thus cannot overturn any established evolutionary mantra. Even then, that mantra is not a key component of the theory of evolution, so even if the mantra is overturned, it will leave no lasting mark on the theory of evolution. In short, Patagomaia is no threat to the theory of evolution and cannot be made to be a threat to the theory of evolution.
I still find Patagomaia fascinating. It is still an unusual mammal to find Cretaceous rocks, and its fragmentary remains mean it may turn out to be an even more special. Maybe future discoveries will reveal that it belongs to one of the extant families of mammals. Of course, it could just as easily turn out to belong to a completely new family of mammals that were unknown before now. That is where much of the fascination lies: in what it could be. Until more material is found, however, we will just have to curb our imaginations and acknowledge that, right now, Patagomaia is not that significant of a discovery.
Thoughts from Steven
[1]Chimento, Nicolás; Frederico Agnolín; Jordi García-Marsà; Makoto Manabe; Takanobu Tsuihiji; Fernando Novas (2024) Scientific Reports 14: 2854
[2]Carroll, Robert (1988) Vertebrate Paleontology and Evolution W. H. Freeman, New York, New York, pg. 430 and Benton, Michael (2005) Vertebrate Paleontology 3rd ed. Blackwell, Malden, Massachusetts, pg. 308-312
[3]Paul, Greory (1988) Predatory Dinosaurs of the World Touchstone, New York, New York, pg.54
[4]Carroll, Robert (1988) Vertebrate Paleontology and Evolution W. H. Freeman, New York, New York, pg. 410
[5]Benton, Michael (2005) Vertebrate Paleontology 3rd ed. Blackwell, Malden, Massachusetts, pg. 288-313
[6]Hu, Taoming; Jin Meng; Yuanqing Wang; Chuankui Li (2005) “Large Mesozoic mammals fed on young dinosaurs” Nature 433: 149-152
[7]Chimento, Nicolás; Frederico Agnolín; Jordi García-Marsà; Makoto Manabe; Takanobu Tsuihiji; Fernando Novas (2024) Scientific Reports 14: 2854
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