“The dinosaurs found themselves holding some bad cards,” Erickson told The New York Times in 2017. “They had a dead man’s hand.”
Dinosaurs like the Hypacrosaurus and the Protoceratops disappeared long after the mass extinction happened, but they are being researched until this very day.
Erickson and his team think that dinosaurs' long incubation and development times stood in the way of their continued survival, but there are likely many other factors at play.
These creatures were often large and required a lot of food to keep themselves going. They had even more disadvantages. Since they needed so much food, and so much of the planet was dying out, many likely succumbed to starvation. In addition, all dinosaurs were cold-blooded, which meant they relied on outside heat sources. With the sun covered under layers of dust and debris, freezing became a much worse threat.
Erickson has also said that dinosaurs likely took a long time to mature, even after they'd hatched. Such slow-developing creatures weren't well-equipped to take on the challenges of the post-asteroid world, and couldn't adapt in time to last.
Adjusting to change and adapting is a critical skill for all species (even humans!) and being unable to do that after such a dramatic change to the planet may have spelled the death of dinosaurs as we know them.
There are still tons of questions researchers aren't able to figure out about dinosaurs, even with Erickson's new methods. For instance, it's impossible to determine the sex of dinosaurs just from looking at their skeletons.
There have been plenty of theories, but they just haven't panned out. Erickson himself has done plenty of studies with what a lot of people consider to be living dinosaurs – alligators – that have resulted in theories being proven incorrect. “That's one of the biggest mysteries – not knowing the sex of an animal.”
Another big question is – how did dinosaurs get so big? Even compared to larger creatures that are around now, such as elephants or giraffes, dinosaurs were huge – even the herbivores. Plenty of them would tower over humans and most other animals.
Even the largest species of animal we have today – the blue whale – only just reaches the size of some of the larger dinosaurs, and the blue whale has the benefit of being an underwater creature, something that facilitates bigger sizes.