Fossil plant phytoliths from the digestive tract of Jeholornis prima — an extinct species of bird that lived in what is now China during the Early Cretaceous epoch, some 120 million years ago — provides direct evidence that this early bird consumed leaves from a group of flowering plants called magnoliids. The broad diet of Jeholornis prima including at least fruits and leaves marks a clear transition in the early evolution of birds in the establishment of a herbivore niche in the Early Cretaceous occupied largely by birds today.
An artist’s reconstruction of Jeholornis prima with potential angiosperm arboreal herbivorous feeding ecology. Image credit: Wu et al., doi: 10.1038/s41467-023-40311-z.
“Plant phytoliths are composed of opaline silica (silicon dioxide) deposited within and between cells formed by monosillicic acid brought into the plants through the uptake of water,” said senior author Dr. Zhiheng Li from the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences and colleagues.
“Phytoliths have a long fossil record to near the origin of plants in the Paleozoic, are resistant to dissolution, and are of particular use in paleontological and archaeological disciplines because of their highly diagnostic utility in plant taxonomy.”
“In addition to their archeological use, phytoliths have been used to reconstruct the diet of dinosaurs through analysis of their feces and dentition related residues, providing direct evidence of dinosaur-plant interactions.”
In the study, the paleontologists examined the fossilized skeleton of a subadult Jeholornis prima found near Chaoyang city in western Liaoning province, northeastern China.
“The fossils from the Jehol Biota in China show us that very early in bird evolution they switched from predatory behaviors to using their wings to fly into trees so they could eat the fruits, seeds, and leaves of plants like so many species do today,” Dr. Li said.
“To better understand early bird diets, we searched for the microscopic fossilized remnants of plants within the remains of the ancient stomach contents inside the bird skeleton, a method not attempted before.”
“We aimed to find phytoliths, which are rigid microscopic structures made of opaline silica produced by plants within and between their cells.”
The researchers recovered hundreds of phytoliths after processing the tiny samples with acid and other chemicals.
“After comparison with over 4,000 kinds of modern phytoliths, we can see that most of the identifiable fossil phytoliths from the stomach come from the leaves of magnoliids,” said first author Dr. Yan Wu, also from the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences and colleagues.
“Similar samples of the rock surrounding the fossil bird skeleton produced no phytolith remains at all, helping to confirm that the recovered phytoliths represent part of the bird’s diet.”
To further support their hypothesis of leaf eating in Jeholornis prima, the scientists compared the lower jaw of this bird to that of living birds with a wide range of diets.
“A more detailed statistical analysis of the three-dimensional shape of the lower jaw of Jeholornis prima shows similarities to the shapes of living birds that eat mostly plants including the living leaf specialist, the hoatzin from tropical forests in South America,” said co-author Dr. Han Hu, a paleontologist at Oxford University.
“Flowering plants are key to living bird diversity because many use nectar and various plant parts to fuel their energetic flight and rapid growth, and many bright feather colors come from eating plants.”
“As we can see with this extinct, vegetarian, tree-living bird, the evolution of birds has been linked to flowering plants for over 100 million years with fruits, seeds, and even leaves serving as main courses on the bird menu starting originally when birds still had teeth and long, bony dinosaurian tails,” said co-author Dr. Thomas Stidham, a paleontologist at the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences.
The results appear in the journal Nature Communications.
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Y. Wu et al. 2023. Intra-gastric phytoliths provide evidence for folivory in basal avialans of the Early Cretaceous Jehol Biota. Nat Commun 14, 4558; doi: 10.1038/s41467-023-40311-z
