Some Sauropod Dinosaurs Laid Eggs Smaller Than a Football Despite Weighing 70 Tonnes

The Cretaceous-Paleogene (K-Pg) extinction event 66 million years ago did not only kill non-avian dinosaurs — it eliminated approximately 75% of all species on Earth, including many marine reptiles (mosasaurs, plesiosaurs), flying pterosaurs, ammonites, and countless plant and invertebrate species. Survivors included small mammals, birds, crocodilians, turtles, snakes, and frogs — groups that could shelter underground, burrow, or tolerate the sudden darkness and cold.

Despite being featured alongside dinosaurs in popular media, pterosaurs were not dinosaurs. They were archosaurs — the same broad group that includes dinosaurs and crocodilians — but evolved flight independently on their own lineage. The first pterosaur appeared around 228 million years ago. The largest, Quetzalcoatlus, had a wingspan of up to 10–11 metres and stood as tall as a giraffe, making it the largest known flying animal in Earth's history.

Micropachycephalosaurus ('tiny thick-headed lizard') from Late Cretaceous China holds the record for the longest dinosaur name at 23 letters. Ironically, it was one of the smallest known dinosaurs, estimated at under 1 metre long. It belonged to the pachycephalosaur family and was first described in 1978 by Chinese palaeontologist Dong Zhiming. Its name is a paradox — meaning small, yet bearing one of the most unwieldy labels in all of palaeontology.

Pachycephalosaurus wielded a dome-shaped skull up to 25 centimetres thick, made of solid bone. Debate continues about whether it used this for head-butting rivals (like bighorn sheep) or flank-butting. Analysis of bone texture reveals healed lesions consistent with high-impact head-to-head contact. Some researchers suggest the domes also served as species and sex recognition signals, as they varied greatly in size and shape between individuals.