Mammalian Croc
Jurassic crocodile
When crocodiles tried to be mammals: the Cretaceous crocodilan Pakasuchus kapilimai, complete with complex, mammal-like dentition and an unusually flexible spine, hunts dragonflies on an ancient Tanzanian floodplain
In an interesting turn of event in the field of paleontology, scientists very recently discovered the fossils of, what they are referring to as, an ancient crocodile with mammal-like teeth! Discovered in the Rukwa Rift Basin, South-Western Tanzania, which's details have been published in the August 5 issue of the journal Nature, paleontologists believe that this newly discovered species, named Pakasuchus Kapilimai, lived between 65 and 144 millions years ago during the Cretaceous period and in the region what is now known as Sub-Saharan Africa. Traditionally what is understood about crocodiles is that, all species of such kind surviving today look, as well as behave in similar fashion. That is, they live mostly in water, ambush their preys of various kinds and eventually swallow it either whole or in sizable chunks. But the discovery of the fossil of this relatively lanky, cat-sized animal with skinny legs, dog-like nose along and mammal-like teeth features only supports a growing consent that crocodiles, as species, were once far more diverse than they are today. It must be mentioned here that the fossilized remains clearly indicate that Pakasuchus (even though at only 50 centimeters or 20 inches in length) has many trademark features that clearly categorizes it as a crocodilian. But its land-based lifestyle on the African floodplains far removed from its aquatic descendants and preying on dragon flies, lizards as well as other animals only point out its distinct mammal-like characteristics which make it a stand-out one in the history of crocodile community. According to Patrick O' Connor, lead author and associate professor of anatomy, Ohio College of Osteopathic Medicine, "If you only looked at the teeth, you wouldn't think this was a crocodile. You would wonder what kind of strange mammal or mammal-like reptile it is". It is him who named the species after Kiswahili word for "cat", the Greek word for "crocodile" and in honor of the late Prof. Saidi Kapilima, who was an important member of the expedition which was funded by the U.S. National Science Foundation and the National Geographic Society.
Back in 2008, a complete skeleton of Pakasuchus was first found and the most complete specimen included a nearly complete skull. This fossil skull, which is very small as Dr. O'Connor neatly puts it, "its head would fit in the palm of your hand", was originally encased in hard, red sandstone, and the jaws were happen to be very tightly closed. This prompted the researchers to take the aid of a scanning technology called X-ray computed tomography which created detailed digital images of the Pakasuchus teeth, skull and the entire skeleton to an accurate of 45 micrometers (millionths of a meter). This reveled to the scientists, first and foremost, that Pakasuchus belonged to an extinct crocodile group called notosuchian crocodyliform. The study also discovered several other somewhat uncanny features of that species as well, most notably its teeth. It is known that all modern crocs have a snout full of consistently conical teeth which allow them snap at their prey with powerful bite before eventually swallowing them whole. But it was found that Pakasuchus had a diverse set of "chompers" including piercing canines and grinding molars along with shearing teeth like those of cats and other meat-eating mammals. The scans also revealed that this ancient creature had only 13 teeth, far fewer than its modern descendants, which were very diverse and its molars fit together extremely well enough to grind and shear food with the aid of a mobile jaw. And these traits are standard features of mammal physiology and very contradictory to the traditional crocodile structure.
Other unconventional features of Pakasuchus include its long slender legs and nostrils on the front end of its snout (indicating it primarily lived on land) whereas modern crocodiles which hunt in water have short legs and nostrils are on the top of their snout.