The Cretaceous big five


In the first of a new series on the weird and wonderful origins of Africa’s wildlife, writer, zoologist and self-confessed dinosaur nut William Gray takes a virtual safari through the Cretaceous Sahara.

A walking safari would have been ill-advised to say the least. In fact, even the most robust 4×4 vehicle might have seemed a tad vulnerable. Back in the Cretaceous era, some 130 million years ago, the chunk of southern Sahara that is now Niger was the stomping ground for the largest, most ferocious dinosaurs ever to inhabit the continent. They would have made today’s meanest-looking Nile crocodile seem about as intimidating as a gecko.

First of the prehistoric big five was the afrovenator, a bipedal, 9m-long, 3m-high carnivore with a no-nonsense set of 6cm gnashers. The deltadromeus, another large meat-eater, had unusually long, slender limbs – perfect for running down prey across the vast floodplains that covered much of the Sahara region at the time. Rivers were the domain of the suchomimus, an 11m-long fish-eating dinosaur with huge ‘thumb claws’ which were probably used for snagging its prey.

But even this terrible trio must have quailed beside the carcharodontosaurus. Africa’s answer to T Rex, this 14m-long, 8-ton monster had a head the size of a small car and serrated teeth measuring up to 20cm in length. Muscular legs and a pair of heavily-clawed arms made it lethally well-equipped for both stalking and ambush. And if you think all that sounds bad, carcharodontosaurus may well have also hunted in packs.

With all these big bruisers knocking about, you would expect there to have been plenty of hearty, non-vegetarian options on the Cretaceous menu. Choice of main course for the likes of carcharodontosaurus and afrovenator inevitably came down to African sauropods like the jobaria (pictured above). Measuring up to 20m and weighing the equivalent of more than four adult male elephants, these long-necked, long-tailed plant-eaters probably foraged in groups, protecting youngsters in the midst of the herd and keeping a constant vigil for predators.

Proof that the jobaria was indeed firmly established in the food chain came when paleontologists discovered a juvenile skeleton with afrovenator teeth marks on its ribs. Other finds in both Niger and Morocco have included turtle shells, crayfish, petrified wood and numerous dinosaur footprints – intriguing clues that scientists have used to imagine today’s scorching Sahara as an antediluvian mosaic of plains, rivers and conifer forests.

For all their size and impressive dental credentials none of the gregarious sauropods or carnivorous dinosaurs that inhabited this lush landscape survived the mass extinction event that erased most of their lineage worldwide. The most conspicuous survivor, so commonly seen on safaris in modern-day Africa that it is rarely given a second glance, is the crocodile.

Crocodiles were no doubt lurking in rivers alongside jobaria, afrovenator and all the others. This supremely successful group of reptiles has its roots in the late Triassic Period, some 200 million years ago. Their ancestors were bipedal which explains why modern-day crocodiles have hind legs that are longer than their forelegs. A few evolutionary requirements, such as a secondary palate that can channel air above the mouth and into the throat passageway, have produced a creature that has, quite literally, stood the test of time.