Roughly 65 million years ago, the dinosaurs’ rule on Earth came to an end when a massive asteroid — about the size of Mount Everest — collided with the planet. This spawned forest fires, sent hefty amounts of particles into the atmosphere, and incited global cooling, which led to the wipeout of much of earthly life.
Around the same time, a period of intense volcanic eruption started in India and lasted for tens of thousands of years.
While these catastrophic events are often deemed the main driver behind the dinosaurs’ extinction at the end of the Cretaceous period, new research emerges and reveals another factor that probably helped kill off the giant creatures: the particularly long time that it took for dino eggs to hatch.
Longer Incubation Time
A new study out of the Florida State University established a timeline of three to six months for a baby dinosaur to incubate. This means that in a post-extinction event situation marked by meager resources, dinosaurs lost out when amphibians, birds, reptiles, and mammals made it through and prospered.
"We suspect our findings have implications for understanding why dinosaurs went extinct at the end of the Cretaceous period, whereas amphibians, birds, mammals and other reptiles made it through and prospered," said lead researcher Gregory Erickson, FSU professor of biological science.
Compared to reptiles, birds lay fewer, specifically larger eggs. Yet they hatch about twice as fast as reptiles: periods ranging from 11 to 85 days for the former, and weeks to many months for the latter.
Dinosaurs also existed in the form of birds, so scientists had long theorized that their eggs would hatch about the same rate.
Based on their investigation of rare fossilized dinosaur embryos, dino eggs actually took much longer to hatch. This is a virtually new finding, as this earliest growth phase is poorly known due to the rarity of dino embryos.
Erickson and the team ran the embryonic jaws through a CT scan and examined the growth of embryonic teeth in two dino species, the sheep-sized dinosaur Protoceratops and the duck-billed Hypacrosaurus. Growth lines on the teeth specimens showed how long the once-mighty animals had been developing in the eggs.
The results showed that the Protoceratops egg likely took almost three months, and the giant Hypacrosaurus egg took up to six months to hatch.
Reevaluating Dino Extinction And Behavior
These new findings showed the distinct disadvantage of dinosaurs compared to other species after the asteroid strike, considering they needed more resources to reach adulthood, took more than a year to reach maturity, and generally had slow incubation times.
Extended incubation also put eggs as well as their parents at grave risks of predation, starvation, and other environmentally driven hazards — realities that spelled grim prospects for survival.
Given their time frames for hatching and migration, it also now seems unlikely that dinosaurs made long travels back and forth from the Arctic region in between seasons, as some theories state.
The study was published in the journal Proceedings of the National Academy of Sciences.
