When one hears the words “large fish-eating predator from Late Cretaceous North Africa”,
what usually comes to mind is spinosaurid dinosaurs such as Spinosaurus or Suchomimus.
But spinosaurids are not the only group of reptiles that fit this description. The fish
of these prehistoric wetlands were also terrorized by a very different group of reptiles named
the stomatosuchids. Distant relatives of crocodilians, they were part of the larger clade Crocodylomorpha.
Stomatosuchidae consisted of three species: the namesake of the group: Stomatosuchus inermis,
and two species of Laganosuchus.
Distant relatives of crocodilians, they were part of the larger clade Crocodylomorpha.
It takes only a brief look at their meter long jaws to know why Stomatosuchus means
“mouth croc” and Laganosuchus means “pancake croc”. Their meter-long jaws were incredibly
broad and flat with a U-like shape. While only the lower jaw is known from Laganosuchus
thaumastos, and even less from Laganosuchus maghrebensis, they are similar enough to Stomatosuchus’s
to indicate their upper jaws were likely similar as well. Stomatosuchus is thought to have
had a large pouch under its throat, comparable to that of a pelican’s. Whether Laganosuchus
shared this trait is currently unclear. However, the teeth of Laganosuchus and Stomatosuchus
were quite different. Stomatosuchus’s upper jaw was filled with small, conical teeth while
the lower jaw may have been toothless. However, this is difficult to verify since the only
Stomatosuchus specimen was destroyed during World War 2. Laganosuchus’s lower jaw was
instead filled with teeth shaped like straight, simple spikes. The teeth were evenly spaced
out across the jaw in both genera. Unfortunately, most stomatosuchids fossils are from the skull.
The only expection was two Stomatosuchus vertebrae that were destroyed along with the skull,
though it is presumed their bodies was similar to that of crocodilians. Based on Laganosuchus’s
jaw, current estimates give it a length ranging from 4 meters to 6 meters. Stomatosuchus was
even larger, with current estimates placing it at 10 meters long. Despite their size,
stomatosuchids would not have been capable of hunting large dinosaurs. Their jaws were
too weak and thin and their teeth too small allow them to hunt such prey. The reverse
situation was much more likely. As mentioned earlier, stomatosuchids are thought to have
instead hunted fish, though their methods of doing were very interesting. One of the
paleontologists who first found Laganosuchus’s fossils, Dr. Paul Serono, considers it to
have been the “ultimate sit-and-wait predator”. The idea is that it laid still in the water
holding its mouth open and then quickly closed it once something swam inside. The tight,
interlocking teeth would then prevent any fish, or other unfortunate animal, from escaping.
While such a strategy would likely mean long intervals between meals, like modern crocodilians,
Laganosuchus was likely ectothermic. This would mean it wouldn’t need to expend most
of its energy maintaining its body temperature, allowing it to survive with much less food.
Stomatosuchus is thought to have acquired its meals by a very different method: filter
feeding. The idea is that when chasing shoals of small fish, Stomatosuchus would trap them
in its massive mouth and then use its throat pouch to push water out. Larger objects, such
as fish, would be keep inside by its teeth, and could then be swallowed. Its potentially
toothless lower jaw may have contained a baleen-like substance to further filter the contents of
the water. If so, Stomatosuchus may not have even needed to go after fish, instead subsisting
instead on plankton. Therefore, Stomatosuchus seems to have been the crocodilian equivalent
of a baleen whale. All known stomatosuchids lived in North Africa at roughly the same
time: the Cenomanian stage of the Late Cretaceous period. This stage lasted from 101 million
years ago to 94 million years ago. Given this length of time, the different members of Stomatosuchidae
were not necessary contemporaries, potentially living millions of years apart from each other.
During the Cenomanian much of North Africa was made of wetlands, a stark contrast to
the arid climate throughout the region today. Other North African fauna from this time included
other strange crocodylomorphs such as Araripesuchus and Kaprosuchus, as well as dinosaurs such
as Rugops Carcharodontosaurus, and the famous Spinosaurus. While the prey Laganosuchus hunted
may have overlapped with that of Spinosaurus, many of the fish Spinosaurus hunted were likely
to large for Laganosuchus, reducing coemption between the two. Spinosaurus was also less
specialized than the stomatosuchids, also hunting other, larger prey. Unfortunately
for the stomatosuchids, they may have very well have found themselves on the menu. As
strange as they were, stomatosuchids were not the only crocodylomorphs who evolved pancake-like
jaws. Similar jaws convergently evolved in a genus of large caiman named Mourasuchus.
Found in South America during the Miocene, the four species of Mourasuchus are also thought
to have been filter feeders like Stomatosuchus. Overall, the stomatosuchids were impressive
animals. Even when known from so little, they show just how diverse Crocodylomorpha once
was, and how wrong the idea that they barely changed since they first evolved is. Since
they are known from such few fossils, future discoveries could find that their pancake-like
jaws are just the tip of the iceberg of these bizarre reptiles. Thank you for watching.
I hope you learned something interesting. Have a great day, and, if you enjoyed the
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