(ORDO NEWS) — Paleontologists have found that primitive birds from the genus Jeholornis, which lived about 120 million years ago, ate fruits and scattered seeds.
The results of the study helped paleontologists explain the widespread distribution of fruits and fruit-like structures during a period of dramatic increase in biodiversity known as the Cretaceous Land Revolution.
This is the earliest evidence for an evolutionary relationship between plants and birds. The work was published in eLife magazine.
Modern frugivorous birds help plants reproduce by dispersing seeds in their droppings. This close relationship between birds and plants has evolved over millions of years, but scientists have not been able to explain how it began.
Birds are known to have become diverse and numerous around 135 million years ago, and shortly thereafter new species of fruit plants appeared.
However, paleontologists have not yet had evidence of the consumption of fruits by primitive birds that lived before the emergence of the crown group.
In 2002, a long-tailed Jeholornis fossil was found in Liaoning province in northeast China. The find is a well-preserved skull, elements of the spine, pelvic bones and fragments of the hind limbs.
The specimen was assigned to the species Jeholornis prima. In addition, seeds were found in the abdominal region of the specimen, and due to the deep lower jaw, the researchers concluded that the extinct bird was a granivorous. 17 years later, another team of scientists suggested that Jeholornis may have eaten fruits.
This is because among the frugivores, there are species that grind or split seeds to extract the necessary nutrients, and species that eat fruit by swallowing the seeds whole.
British paleontologist Han Hu of Oxford University, along with Chinese, American and Australian colleagues, analyzed a specimen of Jeholornis taken from the Shandong Tianyu Nature Museum in China.
To do this, the skull of a fossil bird was scanned using synchrotron tomography and created an accurate and almost complete 3D reconstruction.
As a result of the morphometric analysis of the skull and lower jaw, scientists immediately ruled out the option of cracking seeds, but could not distinguish between grinding seeds and eating fruits.
Next, using high-resolution computed tomography, they compared the seeds found in Jeholornis with seeds eaten by some modern birds, both granivorous and frugivorous.
Food in the alimentary canals of modern seed-eating birds is in a worn form and is found together with gastroliths.
In contrast, in frugivorous birds, the seeds are intact, rarely dispersed in the digestive tract, and are accompanied by a few tiny gastroliths.
Paleontologists have concluded that the seed remains found by Jeholornis are most indicative of frugality, as they are intact and finely dispersed compared to gastroliths preserved in other individuals.
This suggests that Jeholornis ate the whole fruit for at least part of the year. The bird may have changed its food source when fruits were not available, which corresponds to the climate of the western Liaoning region in the Early Cretaceous. Such feeding behavior is also characteristic of modern fruit-eating birds.
As a result of the study, and given that the fossil bird lived during a period of dramatic increase in plant biodiversity, the scientists concluded that Jeholornis is the earliest and only evidence of co-evolution of plants and birds in the Mesozoic.
Paleontologists attribute the lack of other evidence to the fact that food samples of fossil birds are rare: preserved intestinal contents have been found in only a few individuals from Early Cretaceous deposits in China and Europe.
In this regard, researchers sometimes do not immediately succeed in correctly determining the type of nutrition of fossil species.
We recently wrote about the Mesozoic insectivorous bird Longipteryx, which was originally considered to be a fish-eating bird.
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