Paper Published on Crocodile with Mammal-like Teeth

Scientists writing in the journal “Nature” have reported on their research into a strange and bizarre cat-sized, ancient African crocodile that filled a particular niche in the dinosaur dominated Cretaceous ecosystem.  The teeth of this particular reptile are similar to those seen in mammals and indicate that this little animal could bite and chew its food – a behaviour not seen in extant crocodilians.

Ancient African Crocodile

Palaeontologists unearthed an almost complete specimen in 2008, since then a number of other fossils of this 100-million-year-old creature have been found at a dig site in southwestern Tanzania.  No bigger than a domestic cat, this agile reptile scampered around the undergrowth chasing insects and small mammals whilst trying to avoid the attention of larger carnivorous dinosaurs that it shared its flood plain environment with.

Researcher Patrick O’Connor of Ohio University commented on the crocodile’s most striking feature, its teeth stating:

“If someone were just to describe those teeth, the shapes and how they interact with one another or work together, most people would read that as a very mammalian-like dental series.”

The scientist went on to discuss the latest discovery, an intact skull, complete with sharp incisors at the front of the jaws – ideal for tearing meat and interlocking upper and lower molars at the back of the jaw that were used for grinding, just like the teeth in the back of our own jaws.

The crocodile has been formally described and named Pakasuchus kapilimai.  The name means “Cat Crocodile”, from Paka the word for cat in the Swahili language and Suchus coming from the Greek word for crocodile.  A CT scan of this long-limbed terrestrial animal revealed that the molar-like teeth in the top and bottom jaws met very accurately when the animal bit down.  The creature would have eaten with a chewing action, mobile jaws in Reptilia are almost unknown (until now).

An Illustration of Pakasuchus kapilimai

Picture credit: Mark Witton (University of Portsmouth)

Pakasuchus kapilimai

The teeth of modern crocodiles are relatively simple in contrast to Pakasuchus kapilimai.  All the extant species of crocodilian have sharp, pointed conical teeth, the teeth (known as the dentition), may vary in size and angle but they are all virtually the same shape, with the same function to grab and hold onto prey.  Modern crocodiles cannot chew their food, they twist their bodies (known as a crocodile roll) and tear of chunks of flesh from their victims, these pieces are then swallowed whole.

Paul Filmer, Programme Director of Geology and Palaeobiology at the U.S. National Science Foundation, which co-funded the expedition with the National Geographic Society commented:

“The crocodilians with which you and I are familiar have a very characteristic smile, as it were.  The teeth or the dentition that they have is mainly a row of conical teeth which may vary a little bit in size and angle, but they’re pretty much all the same and they basically serve that function which is to grab and tear.”

Scientists say modern crocodiles did not evolve from the prehistoric crocodile-like creature that was a species of ancient reptiles called Notosuchian crocodyliforms that died out around the same time that other land-dwelling dinosaurs became extinct.

Notosuchian crocodyliforms

Paleontologists say Notosuchians are characterised by a variety of different tooth structures and patterns.

Researcher Patrick O’Connor says the 100-million-year-old reptiles, which flourished across a southern landmass the predated the African continent, probably filled a unique ecological niche.

“Maybe there was a certain place in the ecology or in the environment where these animals lived that allowed them to experiment with the shape of the teeth.  And as evolution works, if that was a successful experiment, then a group could go on and have a very long history.”

The crocodilians have evolved into a myriad of forms over their long evolutionary history to read an article about unusual crocodile-like animals: Five “Oddball” Crocodiles from the Mesozoic.

For models and replicas of early members of the Archosauria including models of ancient crocodilians: Prehistoric Crocodile Models and Figures.

Saadanius hijazensis – New Oligocene Primate sheds light on Divergence of Apes

Saudi Arabia 30 million years ago, looked very different than it does today.  Much of this desert kingdom was a lush and verdant paradise for the rapidly diversifying mammalian species.  Bordering the last remnants of the once mighty Tethys ocean there were extensive mangrove swamps and thriving in this half-way house environment between the land and sea were a number of genera of monkeys and other arboreal creatures.  The discovery of a partial cranium (part of the skull) dating from approximately 28-29 million years ago, may have shed light on the divergence of the apes from Old World monkeys.

In the hills overlooking the Red Sea a team of scientists have unearthed the fossilised elements of a skull of an ancient creature that may be a transitional fossil showing a point in the evolution of apes from monkeys.

The skull could help palaeontologists to answer questions about the life of primates in a geological epoch that until now has provided few fossil clues.  The report on this fossil and its potential implications regarding the evolution of apes is published in the scientific journal “Nature”.

Commenting on the discovery, Iyad Zalmout, a palaeontologist with the University of Michigan and an author of the paper stated:

“It turns out it’s not an ape, it’s not a monkey, it’s something intermediate.”

The expedition were a little surprised to find the fossil, their primary objective being to explore the coastal sediments to excavate ancient whale fossils, helping to piece together the evolution of this particular group of mammals. They were not expecting to find ancient monkey/primate remains, especially skull material which could provide a fresh insight into the evolution of apes from Old World monkeys.

Fossil Discovery

Pictures show an anterior view of the skull material (view from the front) on the left and a ventral view (view from the side) on the right.  Although fragmentary, the nasal concha (hole where the nose tissue would be) is clearly visible, along with the nasal bone (links nose to the eyes) and elements of the maxilla.  The face although elongated and angular does have a flattened appearance, a characteristic of apes and of our own hominid ancestors.

This new genus has been named Saadanius hijazensis and it shares morphological features with a family of apes known as the Propliopithecoidea, an ancestor of apes and monkeys that lived more than 30 million years ago.  The fossil record of monkeys from this part of the Cenozoic is particularly poor, arboreal dwelling animals do not generally have a high potential for fossilisation to occur.  This is due to a number of factors but living in a forested environment leads to very few chances of a corpse being fossilised and preserved.  S. hijazensis lacks the advanced sinuses of extant apes and monkeys (collectively called Catarrhines), however, it does have a bony ear tube that was not fully developed in the Propliopithecoidea.

Commenting on the discovery, Erik Seiffert, an anatomist at Stony Brook University in New York said:

“This fossil is really key because it has that bony tube.”

He went on to add that comparison of the bony tube and other features such as the teeth and the forward facing position of the orbit (eye sockets) with those of other primates could help palaeontologists to build up a more complete picture of the ape/monkey family tree.

Saadanius hijazensis

Zalmout and his co-authors are confident that S. hijazensis could help scientists make sense of “competing hypothesis” about how the shape of Catarrhine skulls changed over time.  One theory put forward by palaeontologists based on the limited fossil evidence found to date is that the Catarrhines developed long, flat faces relatively early on in their evolutionary history.  Other scientists, such as comparative anatomists point out that modern, extant genera such as gibbons, have rounder faces and use this evidence to suggest that long, flat faces evolved much later.

The fragmentary Saadanius fossil has a long, flat face and this discovery has excited scientists as it lends support to the theory suggesting the evolution of the flat face very early on in ape evolution.

Erik Seiffert stated:

“This evidence [Saadanius fossil] very clearly supports the palaeontological point of view.”

However, other scientists warn on the over reliance of fossil evidence to prove a particular theory.  For example, facial features may be distorted over the long preservation and fossilisation process, geological pressure can crush, compact and distort features.  Eric Delson, a palaeontologist from Lehman College of the City University (New York), suggested that fossils may only reflect part of the diversity of a group of particular animals, making it difficult to draw precise conclusions.

All the scientists agree that the discovery of more ancient transitional fossils will help to shed light on the evolutionary relationships between different groups.  Saudi officials, keen to promote tourism have already taken steps to preserve this particular dig site.  This will afford palaeontologists the opportunity to explore the area in more depth, perhaps unearthing more fossils that can indicate how Saadanius moved around its mangrove environment and what it ate.

Delson put it succinctly stating:

“It would be interesting to know whether these primates were beginning to come down from the trees and to know something about what they were eating.”

Welcoming the news that Saudi officials want to preserve the site and to promote fossil tourism Zalmout concluded:

“In my experience, if you find one primate there should be more there.  This will be important to see the whole story about fauna in Arabia and Africa.”

We at Everything Dinosaur look forward to reading about future discoveries.

To view models of prehistoric animals including mammals from the Oligocene: Figures of Prehistoric Mammals.