The first large land predators survived because they became better killers
The precursors of mammals dominated the earth for about 60 million years, long before the emergence of the first dinosaurs. They evolved into the most important terrestrial predators between 315 and 251 million years ago.
Researchers examined the jaw anatomy and body size of carnivorous synapsids and used these features to reconstruct the likely feeding habits of these ancient predators and chart their ecological evolution over time. They discovered a major change in synapsid jaw function about 270 million years ago that was associated with a significant change in predatory behavior that had important implications for the evolution of our earliest ancestors.
As herbivores grew larger and faster, carnivores adapted to become larger and more survivable predators.
Infographic showing differences in functional jaw anatomy and body size, as well as possible ecological conclusions found when studying more mammal-like behaviors in ancient predatory synapsids. Illustration by Suresh A. Singh. Photo credit: Kruger Sightings HD.
“Early synapsid predators like the famous veil-backed Dimetrodon had fairly long jaws with lots of teeth to ensure that once their prey was caught, they couldn’t escape,” explained lead author Dr. Suresh Singh from the School of Bristol Earth Sciences. “However, we saw a shift in jaw function toward shorter jaws with greater muscle efficiency and fewer teeth concentrated at the front of the jaw; These were jaws adapted for deep and powerful bites.
“The change shows that later synapsid carnivores placed more emphasis on seriously injuring their prey and thus killing them more quickly.” Among these later synapsids were the first saber-toothed carnivores! “This change makes it clear that predators were exposed to new selection pressure from their prey.”
This finding provides important context for an important step in synapsid evolution. “The reorganization of the synapse jaws over this time is considered an important step in mammalian evolution,” added Dr. Armin Elsler, an employee of the study, added. “These changes not only make the jaw more powerful; They also mark the very early development of the jaw, which also gave rise to the complex hearing of mammals. What was the trigger for this first step? “Our study suggests that it was driven in part by the ecological pressures of its prey.”
These later synapsids included the first saber-toothed carnivores.
Co-author Dr. Tom Stubbs said: “The timing of the change in jaw function corresponds to the evolution of new, larger and faster herbivores that would have presented a greater challenge to predators.”
“Carnivores’ risk of being injured or killed increased, so some synapsid carnivores became larger and better killers to overcome these risks.”
This change reflects new dynamics in predator-prey interactions, showing that life on land was moving faster.
“The Late Paleozoic was the period when animals began to live, feed and reproduce entirely on land,” said Professor Mike Benton, co-leader of the study.
“They became fully terrestrial, colonizing new habitats and further inland exploiting new resources from the waters on which they previously depended.
“Our results show how selective pressures on these early land animals changed as they became better adapted to life on land: it is much harder to catch another animal that can move quickly and grow to larger sizes than to catch a small slippery fish or an amphibian.”
Professor Emily Rayfield was also co-supervisor of the study. She added: “Interactions between predators and prey are now a key determinant of animal behavior. Therefore, it is very special to observe this influence in anatomical evolution over millions of years and to find that they may be responsible for the development of some large animals’ own evolutionary history.
“It shows how paleontologists can use the relationship between form and function to explore how different prehistoric animals lived, which can tell us so much about the evolution of life on Earth.”
The researchers also found that the morphological diversity of synapsid carnivores increased after the shift, with the addition of new functional groups adapted for faster bite speeds or even stronger bites in the Middle to Late Permian, about 265 to 251 million years ago . By studying how the sizes of these new carnivorous species compared over time in different communities, they found that these communities may have begun to closely resemble those of modern carnivorous mammals.
REFERENCE
The ecomorphology of predatory synapsids signals a growing dynamism of late Paleozoic terrestrial ecosystems