Comparison of the metatarsal bones from prehistoric mammals. Credit: Case Western Reserve University
An expert from Case Western Reserve University has discovered that prehistoric horse-like mammals from South America have evolved differently to their Northern Hemisphere counterparts, despite similar climate and ecosystem changes.
Darin Croft from Case Western Reserve, who led the research, stated that this discovery could reveal an previously unknown bias in the Northern Hemisphere when studying ancient animals. He said that scientists could use this bias to predict how animals will adapt to climate change in the future.
Croft is a leader researcher in neotropical paleomammalogy. This is the study of South America’s prehistoric mammals. Croft's primary job is in anatomy at CWRU. These findings were published in the PLOS ONE open-access journal.
Croft worked with Malena Lorente, an Argentinian colleague at the Universidad Nacional de La Plata to study how legs of extinct hoofed mammalsSouth American native ungulates (notoungulates and litopterns) evolved between 23 million years ago and 12,000 year ago.
Croft, Lorente and others then compared the changes to the evolution of similar animals in Eurasia and North America during the same period.
Both horses' northern relatives evolved longer legs to run faster and more efficiently in both regions. They also had longer teeth to graze as they adapt to changing habitats from dense forests to open pastures.
Croft stated that this did not happen in South America even though evidence suggests that the animals had also moved from forests to grasslands. This suggests that not all patterns of mammal evolutionary are driven by climate change or changes in habitats.
"So, maybe the universal patterns we consider to be mammal evolution aren't universal at all."
Challenge a Northern Hemisphere bias
Croft stated that assessments of South American mammal adaptions may be partly based on what we consider normala scientific baseline informed a persistent northern bias.
Croft stated that "Our understanding of the broad patterns in mammal fossil records is mainly based upon North American and Eurasianstudiesnot South America in any significant way." "Our understanding of the past and projections of how animals might react to future changes is incomplete," Croft said.
Croft explained that paleontologists often focus on North American fossils and Eurasian fossils for a variety of reasons. These regions are rich sources of fossil deposits. There are also more countries that have supported paleontology in the past.
Croft stated that the result is due to a geographic bias, which could lead to incorrect assumptions. Croft stated that he will continue to test for this bias in his ongoing investigation into South America’s prehistoric mammals. He also suggested that other scientists might have to deal with it in their future research.
Croft's website, www.dcpaleo.org/, states that South America was geographically remote for the majority of the past 66 millions years. This fossil record makes it an ideal place to "investigate topics like mammal adaptation and diversification and community ecology".
Croft stated that South America was unaffected by mammals from other continents over millions of years and that the solutions it's native mammals found were often more effective than those created by mammals from elsewhere. It is an interesting and important place to study.
Croft stated that he will examine the skeletons of other animals to determine which habitats they lived in.
"This information will help to clarify the 'why' He said that the information would help to clarify the "why?" behind the pattern he had found. It would also clarify how biased explanations of patterns on other continents may be given by the current world.
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More information: Darin. A. Croft and colleagues, No evidence of parallel evolution among Neogene South American native unungulates (SANUs), PLoS ONE (2021). Information from the Journal: PLoS ONE Darin Croft et.al, No evidence for parallel evolutionary of cursorial limb adapts among Neogene South American native ungulates. (2021). DOI: 10.1371/journal.pone.0256371
