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THE OULED ABDOUNE BASIN FOSSIL BEDS OF MOROCCO

I am fortunate to have in my collection representative fossils of the phosphate beds of the Ouled Abdoune Basin of Morocco: Enchodus lybicus and Mosasaur beaugei from the Upper Cretaceous Period near Ouled Abdoune and an assortment of sand shark teeth from the Paleocene Epoch of the Khouribga portion of the phospate beds, both time periods represented in fossil bed’s stratigraphy shown below. However much I value my Moroccan teeth collection, I shall discuss them briefly as I have all my other specimens, in context with the fossils within the geological stratigraphy they were found. In the case of Ouled Abdoune and the fossil beds found in Khouribga, the discoveries have inspired many paleontologists and geologists to call this corner of the Sahara another Burgess Shale. This claim might seem like an exaggeration, since most of the Moroccan species are not unique, but the phosphate beds are considered to be one of the most important paleontological discoveries made in Africa.

Ouled AbdounE: Africa’s Version of the Burgess Shale

The fossils found in the Ouled Abdoune Basin have several important features for the professional and amateur paleontologist: they are plentiful, remarkably diversified and well preserved, and they attest to key periods in vertebrate evolution, chronicled in logical succession in the phosphate beds. In terms of the ICS Time Scale, as shown in the following chart, the fossil sequence begins in the Santonian stage of the Upper Cretaceous period, continuing through the Maastrichtian stage and ending in the Danian stage of the Paleogene at what the Standard Geological Scale would indicate as the demarcation point between the end of the Cretaceous period and beginning of the Tertiary period or Paleocene epoch. Since many scientists believe that this time interval saw the extinction of the dinosaurs, the ICS Time Scale’s smaller increments of time encourage paleontologists and geologists to see in the Danian (earliest Paleocene) an almost seamless point for the KT boundary (K=Cretaceous and T=Tertiary). Whatever theory is recognized—comet collision, virus attack, egg-eating mammals, etc—recent discoveries in New Mexico indicate that not all dinosaurs became suddenly extinct when the geological dial moved into the Danian stage. Yet nowhere else in the world is there a site where the dinosaurs and giant reptiles transition into the Age of Mammals in such a logical, complete sequence. Evolution is seen clearly in the barren Sahara rock, where primitive forms evolved into more advanced forms—proof-positive of the principle of faunal succession.

Stratigraphy of the Ouled Abdoune Phosphate Beds

Creatures of the oULED ABDOUNE Phosphate Beds

Because the setting for Ouled Abdoun’s diverse creatures was a shallow sea that bordered dry land, the outcrops at this site reflect both a marine and terrestrial environment. The richest vertebrate marine fauna known to science also includes, after recent discoveries, dinosaur fossils, along with bony fishes, crocodiles, early mammals, and birds in the Maastrichtian stage of the Upper Cretaceous, as well as more advanced mammals, new crocodile species, and sea birds in the Danian stage of the Paleocene Epoch. The Ouled Abdoun Phosphate Beds have also yielded the oldest known modern birds (Neornithes), shedding light on the evolution of this important subclass. One of the mammal specimens found in the Danian levels, Eritherium, who is considered by many paleontologists to be the ancestor of elephants, is also the oldest known placental mammal of Africa. Among the signficant finds at Ouled Abdoun, Enchodus lybicus, a saber-tooth relative of the modern salmon, was discovered in both the Upper Cretaceous and succeeding Tertiary levels of the phosphate beds. Unlike the dinosaurs and marine reptiles, this fish survived the Upper Cretaceous extinction and is found, along with other fossil fish, throughout the beds. Mosasaur beaugei, which didn’t survive into the Tertiary period, probably included juvenile Enchodus in his diet. The fact that such giant fish as Enchodus and large crocodiles, such as Arambourgisuchus, as well, as many land mammals and reptiles survived the KT extinction has made me a skeptic of the theory that a comet wiped out the dinosaurs. Nevertheless, whatever it was that wiped out the dinosaurs and marine reptiles, the transitioning layers of the phospate beds appear to add weight to a general and sudden end. At the top portion of the Maastrichtian stage in various outcrops there are still an assortment dinosaur and marine reptile bones, and then, quite abruptly, in the earliest Danian, where the Tertiary period begins and the Cenozoic Era launches the Age of Mammals, the Age of the Dinosaur and Marine Reptiles is suddenly over. The upper levels also present advanced species of mammals and birds and the continued existence of Enchodus in the marine outcrops.

Note: To zoom in and out on one set of teeth, click on one the photos below:

Mosasaur beaugei Enchodus lybicus Sand Shark