Introduction During the Triassic period,
before the reign of the dinosaurs, the ancestors of the crocodilians were small, terrestrial
animals. The niche of semi-aquatic ambush predator was instead held by a different group of reptiles
called phytosaurs. While they may have looked similar to today’s crocodilians, the phytosaurs
were actually only very distant relatives who independently converged upon a crocodilian-like
appearance and lifestyle. Among the largest of the phytosaurs was Smilosuchus. Smilosuchus is a
genus that consists of three species: Smilosuchus gregorii, Smilosuchus adamanensis, and Smilosuchus
lithodendrorum. They lived in what is now the southwestern United States between 220 to 205
million years ago during the Late Triassic period. The different species of Smilosuchus varied
in size. Smilosuchus adamanensis was about five meters long. Smilosuchus gregorii was much larger.
Its total body length was at least seven meters long, and some estimates place it up to twelve
meter long. Such a length is longer than many of the later mega-crocs like Deinosuchus. However,
even if Smilosuchus gregorii was that long, phytosaurs had proportionally longer tails than
crocodilians do. Therefore, it wouldn’t have been as deadly as an equally long
Deinosuchus. Still, Smilosuchus gregorii was at least far larger than any modern reptile.
Though Smilosuchus may have looked, and in many ways acted, similar to crocodilians, there
were some key differences besides tail length. Crocodilians have extensive bony plates on their
bodies called osteoderms. Phytosaurs also had osteoderms, but theirs’s were even more extensive.
Like other phytosaurs, Smilosuchus’s skull wasn’t as wide as those of most
crocodilians. While there are crocodilians with thin snouts, Smilosuchus’s snout was deeper than
these species and the end was slightly downturned. Additionally, Smilosuchus had a large nasal crest,
likely to attract mates. Its nostrils were on these crests, close to its eyes. This is in
contrast to crocodilians, whose nostrils are at the end of the snout. The teeth of modern
crocodilians are fairly uniform in shape. While this was true for most of Smilosuchus’s teeth,
the teeth at the front of the jaw were long and tusk-like. While they were part of the same genus,
the different species of Smilosuchus held very different niches, or ecological roles.
This was due to them splitting up the resources in their environment
by specializing to catch different types of prey, which is referred to as niche partitioning. Each
of the three species of Smilosuchus serve as an example of the three basic phytosaur
morphotypes. The snout of Smilosuchus adamanensis is slender and filled with small, conical teeth,
placing it in the dolichorostral morphotype. These phytosaurs were fish-eating specialist.
Modern crocodilians with similar ecologies include the gharial and slender-snouted crocodiles.
It should be noted that these crocodilians do not exclusively eat fish but also invertebrates and
small terrestrial animals. The same was likely also true for the dolichorostral
phytosaurs like Smilosuchus adamanensis. On the other hand, the teeth of Smilosuchus gregorii
are larger and serrated, making them ideal for cutting through flesh. Its skull is also deeper
and broader than that of Smilosuchus adamanensis, which would have made it more resistant against
struggling prey and provided space for powerful jaw muscles. Phytosaurs with these traits are
called brachyrostral. Brachyrostral phytosaurs are generally considered to have specialized in
hunting large animals. With its massive size, Smilosuchus gregorii would have been able to
hunt the largest animals in its environment. If rauisuchids like Postosuchus were the Triassic
equivalent of the lion, Smilosuchus gregorii was the Triassic equivalent of the Nile crocodile.
While it may have caught its prey in a manner much like the crocodiles of today, it likely
used a very different method to kill them. When crocodilians attack large animals, they hold onto
them and then drag them into the water to drown. While the conical teeth of crocodilians are well
suited for holding onto their prey, its serrated teeth suggest Smilosuchus gregorii dispatched prey
in a more direct fashion. Once it grabbed onto its victims with its front, tusk-like teeth, it could
use its serrated teeth to create grievous wounds. Since its main method of dispatching its victims
didn’t require the water, it is probable that Smilosuchus gregorii also hunted on land. This is
supported by its robust femur, which suggests it spent more time on land than most crocodilians do.
Finally, Smilosuchus lithodendrorum seems to have been altirostral. Altirostral phytosaurs
were generalists who were between the two other, more extreme phytosaur morphotypes. A good modern
equivalent is the American crocodile. As powerful as Smilosuchus was, life is not easy for even the
deadliest of predators. The limb bones of one Smilosuchus gregorii specimen have numerous
paleopathologies. A paleopathology is evidence of disease or injury in a fossilized creature.
In the case of the Smilosuchus specimen, its limbs bones have extensive signs
of osteomyelitis, swelling in the bone. Osteomyelitis can be caused by an injury
or an infection that spread to the bones from elsewhere in the body. Based on its progression,
it is thought the Smilosuchus survived for at least a few months and perhaps years with
these lesions. Its paleopathologies are more extensive than on any other recorded phytosaur,
or even among their more distant relations from the Triassic period. While a significant
discovery, this would have been little comfort for the unfortunate Smilosuchus who had them.
Though Smilosuchus may have survived to the very end of the Triassic Period, all phytosaurs
perished during the mass extinction between the Triassic and Jurassic period. However, when it
was alive, this single genus showcased a wide amount of diversity within just a few species,
including one of the deadliest predators of the Triassic Period. Thank you for watching. I hope
you learned something interesting. Also, I used a new microphone to record the narration for this
video, so feedback on whether you think the audio quality has improved from this is appreciated. As
always, have a great day, and, if you enjoyed the video, please remember to hit the like button.