Pterosaurs Were Not Dinosaurs — They Were Flying Reptile Cousins

Despite being the largest land animals ever, sauropod dinosaurs laid surprisingly small eggs relative to their body size. The largest known dinosaur eggs (Macroelongatoolithus) were about 45–60 cm long, yet the adults that laid them might weigh 40–70 tonnes. This is because eggshell thickness is limited by the need for oxygen exchange — a larger egg would suffocate the embryo. Hatchlings were therefore tiny compared to adults, growing at astonishing rates throughout their lives.

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.

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.