A slight breeze blows the morning dew drops from the leaves of the plants surrounding the creek as a herd of herbivorous Coahomasuchus browse horsetails and ferns. These small armored reptiles are joined by a herd of large Gorgetosuchus, which bare magnificent spikes and ridges from their armored backs. These duck-billed armored herbivores or aetosaurs as they’re known are among the larger creatures to roam these forests, although they often fall prey to the many terrestrial and aquatic predators with which they coexist.
Among such predators are phytosaurs, large, scaly hunters which bask along the banks of rivers waiting to snap at any passers-by. These cranky reptiles are hardly the devils of these forests , and often are frightened away by little but a scratch from one of the Gorgetosuchus’s shoulder spikes. Mobs of proterosuchids also line the water’s edge, but prefer fish and amphibians to the well-defended terrestrial herbivores. Often the aetosaurs must be more wary of the smaller but poisonous Uatchitodon, which scurry around in search of insects and small vertebrates to eat. When threatened, the small carnivores cower in a defensive posture. The small size of the Uatchitodon make them hard to spot, and often an aetosaur gains a scar from accidental confrontation with such small poisonous reptiles.
Herds of large, cranky Placerias also pose a threat to the armored aetosaurs. The sparsely haired skulls of these cow-like herbivores bare large tusks that could easily cripple an ignorant aetosaur, and individuals from both Placerias and Gorgetosuchus herds bare evidence of confrontation with their large, herbivorous contemporaries.
The aetosaurs’ greatest foe is an aged Carnufex bull. The old predator is a giant among the inhabitants of these woods, stretching 14 feet from nose to tail. He was once longer, but a chance encounter with a 3 meter subadult Carnufex caused the old bruiser to lose a small portion of the end of his tail. The old bull has a huge territory spanning almost six square miles, and has held the area for many years. The aetosaurs are easy prey for the aged reptile, who’s instinct gives away around the spiked herbivores’ armor.
The aetosaurs, now finding themselves on a hill, start to chew through the vegetation covering the ground. Nearby is their silent enemy, the Carnufex bull, who hides behind a large boulder. The aetosaurs sense his presence, and as he appears from his bunker lower their bodies in defense. The gnarly scarred skin of the bull Carnufex gleams in the sun as he slowly creeps across the rocky soil in an austere manner, undaunted by the glimmering spikes of his targets. The bull suddenly erupts into a fury of predatory energy, latching onto the relatively unprotected head of one of the aetosaurs. His teeth sink into the aetosaurs face, blinding the poor herbivore. Disoriented, the herbivore stumbles while the other aetosaurs flee. The Carnufex bull now has the upper hand. Using his bodyweight, he pushes over the bloodied aetosaur, exposing its unprotected stomach. All the fleeing aetosaurs hear are the moans and growls of the combatants. Soon all falls silent, and another Triassic night sets in.
Eastern North America has preserved an excellent record of the Late Triassic, with many formations bearing the remains of strange creatures of lineages long gone. Among those which contain the most complete record of this time is the Pekin Formation, which outcrops in the states of North Carolina. The Pekin Formation dates to approximately 231 million years ago, preserving some of the oldest known Triassic archosaur faunas in North America (Zanno et. al., 2015). Among the larger predators of this formation was Carnufex carolinensis, a relative of the ancestor of the group crocodylomorpha, which includes all modern day crocodylians and many other clades of extinct genera. Carnufex carolinensis would have been a large predator in life. The type specimen, a juvenile, would have already measured 3 meters long in life (Zanno et. al., 2015).
The most interesting thing about Carnufex carolinensis is not its size, but where as a predator it was in time. The Triassic provided an open door for evolution, as the Permian extinction had created unstable biological communities and altered ecosystems (Roopnarine et. al., 2007; Bambach, Bush & Erwin, 2007). New types of large predatory animals had room to grow.
The skeleton of Prestosuchus, a large Triassic pseudosuchian. Pseudosuchians were among the groups which gave rise to large predators during the Triassic. Photo by the author, 2015. Note the phytosaur skull in the background.
What Carnufex carolinensis shows is that crocodylomorphs were more diverse during the Triassic than previously thought, and alongside early dinosaurs were diversifying to become both apex and non-apex predators (Zanno et. al., 2015). Carnufex carolinensis itself is the largest known terrestrial predator known from the Pekin Formation, and was much larger than the earliest known North American theropods (Zanno et. al., 2015).
Within the Pekin Formation, Carnufex carolinensis would have coexisted with both a variety of predatory and a variety of herbivorous animals. Bulky dicynodonts would have lumbered around next to the armored aetosaurs Gorgetosuchus, Coahomasuchus, and Lucasuchus (Green et. al., 2005; Heckert et. al., 2015; Heckert, 2012). Predatory animals like cynodonts and phytosaurs also inhabited the formation (Liu & Sues, 2010; Baird, 1986).
Carnufex represents a group of archosaurs responding to new opportunities in a recovering ecosystem. However, the large, terrestrial crocodylomorphs of the Triassic were not to last. The End Triassic Extinction would see the replacement of such large bodied forms by theropod dinosaurs (Zanno et. al., 2015). Carnufex and its contemporaries in the Pekin Formation ecosystem represent a bouncing back from extinction, a rise from oblivion.
Carnufex carolinensis by the author. Pencils on paper, 2016.
References
- Zanno LE, Drymala S, Nesbitt SJ, Scheider VP. 2015.Early crocodylomorph increases top tier predator diversity during rise of dinosaurs. Scientific Reports 5: 9276.
- Roopnarine PD, Angielczyk KD, Wang SC, Hertog R. 2007. Trophic Network Models Explain Instability of Early Triassic Terrestrial Communities. Proceeding of the Royal Society of London B: Biological Sciences 274: 2077–2086.
- Bambach RK, Bush AM & Erwin DH. 2007. Autecology and the Filling of Ecospace: Key Metazoan Radiations. Palaeontology 50: 1–22.
- Green JL, Schneider VP, Schweitzer M, Clarke J. 2005. New evidence for non-Placerias Dicynodonts in the Late Triassic (Carnian-Norian) of North America. Journal of Vertebrate Paleontology Programs Abstracts 25: 65-66.
- Heckert AB, Schneider VP, Fraser NC, Webb RA. 2015. A New Aetosaur (Archosauria, Suchia) from the Upper Triassic Pekin Formation, Deep River Basin, North Carolina, U.S.A., and its Implications for Early Aetosaur Evolution. Journal of Vertebrate Paleontology 35: e881831.
- Heckert AB. 2012. Two New Aetosaurs (Reptilia: Archosauria) from the Upper Triassic Pekin Formation (Deep River Basin: Newark Supergroup) of North Carolina and the Phylogeny and Distribution of Aetosaurs. Geological Society of America Abstracts with Programs 44(7): 233.
- Liu J & Sues HD. 2010. Dentition and Tooth Replacement of Boreogomphodon (Cynodontia: Traversodontidae) from the Upper Triassic of North Carolina, U.S.A. Vertebrate Paleontology Asiatica 48: 169–184.
- Baird D. 1986. Some Upper Triassic Reptiles, Footprints and an Amphibian from New Jersey. The Mosasaur 3: 125-153.
An Odyssey of Time 