A examine of fossil eggs in China means that dinosaurs weren’t very various and declined total, even earlier than their extinction round 66 million years in the past.
The long-term decline in international dinosaur range and the continued low numbers of their lineages over the previous few million years might outcome from local weather fluctuations and an enormous volcanic eruption from the Deccan Traps in India, researchers mentioned.
These elements could have induced widespread instability within the ecosystem, thus leaving non-bird dinosaurs susceptible to mass extinctions that coincided with asteroid impacts, he mentioned.
A big asteroid that struck Earth on the finish of the Cretaceous interval – 145 to 66 million years in the past – is believed to have contributed to the worldwide extinction of the dinosaurs, leaving birds as their solely surviving descendants.
It is extensively debated whether or not dinosaurs have been at their peak or in decline earlier than their demise.
Most of the scientific knowledge on the final days of dinosaurs comes from North America.
Although some revealed research recommend that dinosaur populations have been rising properly earlier than the extinction, different detailed analysis has instructed that dinosaurs have been in decline, which set the stage for his or her mass extinction.
Researchers from the Chinese Academy of Sciences studied the eggs and eggshells of greater than 1,000 fossil dinosaurs from the Shenyang Basin in central China.
These fossils got here from a rock sequence with a complete thickness of about 150 m.
The analysis, just lately revealed within the journal PNAS, analyzed greater than 5,500 geological samples and utilized laptop modeling to acquire detailed age estimates of the rock layers.
This allowed scientists to attract a timeline of about 2 million years on the finish of the Cretaceous – with a decision of 100,000 years – representing the interval simply earlier than the extinction.
This timeline permits for direct comparability with knowledge from all over the world. The researchers recognized a decline in dinosaur range based mostly on Shenyang Basin knowledge.
For instance, the 1,000 dinosaur egg fossils collected from the basin characterize solely three totally different species: Macrolithus yaotunensis, Elongatolithus elongatus and Stromatolithus pinglingensis, he mentioned.
The researchers additionally discovered that two of the three dinosaur eggs are from a bunch of toothless dinosaurs referred to as oviraptors, whereas the opposite is from a bunch of plant-eating hadrosaurids, often known as duck-billed dinosaurs.
He mentioned some further dinosaur bones from this space recommend that tyrannosaurs and sauropods additionally lived within the space between 66.4 and 68.2 million years in the past.
According to the researchers, this low range of dinosaur species continued in central China for the previous 2 million years earlier than the mass extinction.
These outcomes, mixed with knowledge from North America, recommend that dinosaurs have been in all probability declining globally previous to their extinction, he mentioned.
With inputs from TheIndianEXPRESS
