Findings on Dinosaurs: The Terror of the Lower Cretaceous

Kontofactual history can be driven not only with the outcome of the Second World War or the fall of Rome, but also with the history of the earth. Thoughts on the question of how life would have evolved are particularly entertaining here if, at the end of the Cretaceous period 66 million years ago, an asteroid had not completely destroyed the then dominant faunal group of dinosaurs – apart from three small groups, the ancestors of today’s birds extinguished. Wouldn’t art, war, and herbalism be run by sparsely haired mammals, then, by some lizard creature like the legendary Gorn of the 1967 Star Trek episode “Arena”?

A little more informed speculation about evolutionary events on that alternate timeline now ensues a study close, the researchers led by Matteo Fabbri from the Field Museum of Natural History in Chicago in the current issue of Nature have published. Thus, the seas of the counterfactual post-Cretaceous period might have been populated by fish- and whale-like creatures descended from dinosaurs.

Movie star with back sail

Terrestrial vertebrates have returned to the water more than thirty times, completely independently of one another, and have adapted the structural plans of their bodies to an aquatic lifestyle. This happened, for example, in the case of the evolution of whales, seals, but also plesiosaurs, which lived at the same time as dinosaurs but are not more closely related to them than simply being reptiles. They all had ancestors who walked on four legs over dry land. And the ancestors of the fish-shaped ichthyosaurs were at least amphibians. Such a return to water seems to have occurred in most large groups of animals. Only the non-bird dinosaurs, which roamed the Earth’s land masses at the top of the food chain for at least 165 million years, have stayed there forever. With one prominent exception, as Matteo Fabbri and colleagues have now been able to show: the Spinosauridae family.

Posterboy of this group is the genus Spinosaurus. If this term means nothing to you, just look around in a child’s room. In addition to T-Rexes, brontosaurs and triceratops – all of which are documented plural formations by preschool children – there is almost always a plastic figure of a Spinosaurus. The animals can be recognized by their elongated snout and the strange dorsal sail, to which they owe their name. When the paleontologist Ernst Freiherr Stromer von Reichenbach first came across fossilized skeletal remains of such a creature in Egypt in 1912, he was particularly amazed at the enormous processes of the middle dorsal vertebrae, which looked like spines (Latin spinae) to him. Stromer himself suspected that these appendages supported a fat hump, but many other researchers believe that they simply stretched out a thin flap of skin, so the biological purpose of this device is debatable: it may have served to regulate temperature to lend weight to threats against rivals or simply for peacock-like showing off to the opposite sex.