Northern Dinosaurs?

Although the Arctic, 70 million years ago, didn't have a big polar icecap, it would still have been a pretty hostile place for a dinosaur. Dinosaur fossils have been found in the far North but it had been assumed they were summer visitors. Gregory Erickson (Florida State University) and colleagues used sieving techniques on Upper Cretaceous deposits of the Prince Creek Formation in Northern Alaska. They found tiny fossils from very young dinosaurs of 7 different types (both herbivores and predators). The evidence, they suggest, means dinosaurs lived and raised their young in the Arctic (https://www.theguardian.com/science/2021/jun/24/dinosaur-fossils-eggs-arctic-research). In a paper, in Current Biology, Erickson and colleagues speculate that some of the Arctic dinosaurs may have hibernated or even have been warm-blooded. The Viper (Vipera berus) is also a reptile that can currently be found almost up to the Arctic circle. It certainly does hibernate. Although, Erickson talks mainly about egg-laying by his dinosaurs, it's conceivable that some became ovoviviparous (producing live young). The Viper does this (meaning the species can breed in the far North) and some of the Cretaceous marine reptiles also developed this ability. Ichthyosaurs couldn't return to land to lay eggs.