Hundreds of animals eat fruit, from toucans to fruit bats to maned wolves to humans. But most fruit-bearing plants evolved relatively recently in Earth’s history, first appearing in the Cretaceous Period, the last period of the dinosaurs. In a new newspaper in eLife, scientists have pinpointed the first fossil evidence of fruit consumption by comparing the skull shapes and stomach contents of fossil birds. The verdict: The earliest known fruiteater was an early bird named Jeholornis that lived 120 million years ago, and it may have helped spread the plants that dominate the world today.
“This is the oldest evidence of fruit eating in any animal,” said Jingmai O’Connor, associate curator of fossil reptiles at the Field Museum in Chicago and co-author of the new eLife paper. “Fruits are an incredible resource that everyone is familiar with, and the plants that produce them are everywhere, but it wasn’t always so. This discovery about how and when birds started exploiting this resource could help explain why these types of plants are so dominant in our landscape today.”
“Birds are important fruit consumers today and play an important role in seed dispersal, but so far there is no direct evidence of fruit consumption by early birds, outside the bird crown group,” said Han Hu, a researcher at the University of Oxford and the first author. of the study. “This hinders our understanding of the origin of this important interaction between plants and animals.”
The crown group of birds is the group alive today, Neornithes, and their direct ancestors. But other birds started developing tens of millions of years earlier; the second most primitive known bird was a creature the size of a long-tailed raven named Jeholornis. The time between the first Jeholornis and the first T. rex is about the same as the time between the last T. rex and modern humans.
“The first Jeholornis fossil described in 2002 has all these plant remains scattered around it. It looks like they exploded from the stomach cavity,” O’Connor says. “This stomach contents were superficially identified as seeds, so people claimed it was eating seeds. Then 17 years later, other scientists suggested it wasn’t eating just seeds, but whole fruits, and only keeping the seeds, because they’re harder. study we wanted to find out, did it feed only on seeds or eat fruit?”
“Clarification between these two hypotheses is important because fruit consumption can lead to co-evolutionary mutualism, while seed consumption does not,” says Hu — eating fruit and pooping uncrushed seeds could help plants proliferate and evolve, but if the seeds were crushed and digested, that wouldn’t help the plants.
To solve this mystery, Hu had to examine dozens of Jeholornis specimens at China’s Shandong Tianyu Museum of Nature. She selected the one with the best-preserved skull and scanned it at the Australian Nuclear Science and Technology Organization’s (ANSTO) Australian Synchrotron, Melbourne, Australia.
The scan revealed that Jeholornis’ skull has many features that resemble a dinosaur more than a modern bird (modern birds are the only surviving group of dinosaurs). However, the skull had some features in its mouth and beak, such as reduced teeth, which are present in modern birds — features that could potentially indicate a “modern” diet of fruit.
After comparing this reconstructed skull of Jeholornis with the skulls – especially the jaws – of modern birds, including species that grind seeds; species that crack seeds; and species that eat fruit and leave the seeds whole, the analyzes rule out the seed bursting.
However, O’Connor says, “You can’t really tell different diets apart from just the mandible shape.” But other parts of the fossils may provide additional clues. “Birds that eat seeds have a stomach, a gizzard,” says O’Connor. “They swallow rocks to help them crush their food.”
Some specimens of Jeholornis have been found with gizzard stones, and some have been found with preserved seeds in their gut, but no one has found a Jerholornis with both gizzard stones and seeds at the same time. In addition, the seeds in the gastric cavities of Jeholornis are whole, not crushed.
These findings suggest that Jeholonis ate different foods at different times of the year. If fruit were available, it would have eaten whole fruit, seeds and all, and then pooped out the uncrushed seeds. If fruit wasn’t in season, it would have eaten something else — and harder — and relied on a gizzard to crush them. The Jeholornis specimens with whole seeds in their stomachs must have died during the fruit season.
This seasonal diet is consistent with a trait present in many modern birds. “Birds can drastically change the proportions of their digestive systems to adapt to whatever their diet is for a given season,” says O’Connor. “This is the first evidence of that plasticity in dinosaurs.”
Not only was Jeholornis the first known fruit eater, but it also gives scientists a glimpse into how birds helped fruit-producing plants evolve. “Birds may have been recruited for seed dispersal during their earliest evolutionary stages,” Hu says. “As highly mobile seed dispersers, early fruit-eating birds may therefore point to a possible role of bird-plant interactions during the Cretaceous terrestrial revolution,” in which angiosperm plants begin to take over the world. Birds that eat fruit and defecate seeds far away from the parent plant can help fruit-bearing plants spread like wildfire; this pattern may have started with birds like Jeholornis.
Jeholornis’ fruit eating also ties in with his traits that would have helped him fly, including a long tail that could have acted as a rudder to stabilize him in flight. “A diet of fruit may have evolutionarily pressured Jeholornis to fly better,” O’Connor says. “You can’t sit in one tree forever and eat its fruits. You have to be able to move and identify those resources by flying up and seeing where they are.”
Hu says she hopes that “our research will inspire the research of paleontologists, ecologists, zoologists and botanists interested in avian ecology, trophic interactions and the Cretaceous Terrestrial Revolution. It is also a flagship of applying multiple advanced methods simultaneously to complex palaeoecological questions, which will inspire future researchers to conduct similar analyzes to reveal the ecologies of the extinct animals.”
Researchers report evidence that fruit plants evolved to provide seed dispersers with an appealing scent
Han Hu et al, Earliest evidence for fruit consumption and possible seed dispersal by birds, eLife (2022). DOI: 10.7554/eLife.74751
Quote: The Early Bird Gets the Fruit: Fossil Provides Earliest Evidence of Fruit Eating by an Animal (2022, Aug. 16) Retrieved Aug. 16, 2022 from https://phys.org/news/2022-08-early-bird-fruit-fossil -earliest.html
This document is copyrighted. Other than fair dealing for personal study or research, nothing may be reproduced without written permission. The content is provided for informational purposes only.