Body-Mass Evolution of “Thunder Beasts”

Thi Minh Phuong Duong
Ton Duc Thang University

May 29, 2023

Brontotheres, rhinoceros-like creatures, experienced a significant size change over 22 million years. Within 16 million years, these mammals, initially no bigger than cats or coyotes, underwent a rapid transformation, becoming enormous creatures weighing a metric ton or even more. Due to this extraordinary transformation, scientists gave these mammals the name “Thunder beasts,” derived from the Greek bronte, “thunder,” and Greek therion, “beast, wild beast, hunted animal.” The remarkable evolution in size of these “Thunder beasts” took place following the extinction of dinosaurs, and it can be said that the rapid diversification of body size in brontotheres is widely regarded as one of the most remarkable achievements in mammalian evolution [1].

Illustration: The picture illustrates the Megacerops kuwagatarhinus, one of the brontotheres. These creatures were known to attain staggering weights, often exceeding a metric ton or even greater. Retrieved from Elise [1].

One explanation for the remarkable body-mass transformation of “Thunder beast” came from Cope’s rule, which emphasizes the inclination of organisms in evolving lineages to increase in size progressively. Early scientists believed that brontotheres became bigger due to an internal driving force that pushed them to become larger, regardless of their environmental conditions [2].

However, the recent study conducted by Sanisidro et al. in 2023 challenged Cope’s rule and looked at different ways that “Thunder beasts” evolved over time. The scientists examined the relationships between the size of brontotheres, their habitat, and the likelihood of extinction or speciation. The findings indicate that smaller brontothere species in highly competitive ecological settings faced a higher risk of extinction. The increased size of the larger brontotheres enhanced their chances of survival and population expansion [1, 3].

This observed increase in body size among the brontotheres can be understood as a response to selective pressures imposed by the environment and the availability of resources. It is believed that larger species exhibited higher survival rates, likely due to reduced competition with other herbivores in their ecological niches. Therefore, the long-term directional change in body size among the “Thunder beasts” is believed to have resulted from the higher survival rates of larger lineages within less-crowded herbivore communities [2].

Considering these findings through the lens of the mindsponge theory, in conjunction with BMF analytics, it becomes evident that there is a mutual connection between the cognitive abilities of organisms and the profound influence exerted by interactions with the external environment. These cognitive abilities equip organisms to learn, adapt, and evolve based on their acquired information [4, 5].


[1] Elise C. (2023). ‘Thunder beast’ fossils show how some mammals might have gotten big. ScienceNews.

[2] Cope ED. (1986). The primary factors of organic evolution. Open Court Publishing Company.

[3] Sanisidro O, Mihlbachler MC, Cantalapiedra JL. (2023). A macroevolutionary pathway to megaherbivory. Science, 380(6645), 616-618.

[4] Vuong QH. (2023). Mindsponge Theory. De Gruyter.

[5] Vuong QH, Nguyen MH, La VP. (2022). The mindsponge and BMF analytics for innovative thinking in social sciences and humanities. De Gruyter.

tags:   Thunder Beasts