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Phytosauria

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Phytosaurs were a group of large, mostly semiaquatic reptiles from the Late Triassic period.

Phytosaur skull
Phytosaur skull

They belonged to the order Phytosauria and are sometimes called parasuchians. These animals are famous for their remarkable resemblance to modern crocodilians. This similarity in size, appearance, and lifestyle is an example of convergence, or parallel evolution. Even though they look like crocodiles, they are distinct biological groups. Phytosaurs were highly successful predators that lived in many different environments around the world.

Phytosaurs exhibited diverse skull shapes that related to their specific feeding habits. One type was the dolichorostral phytosaur, which possessed a long, slender snout. These animals had many conical, homodont teeth, meaning all their teeth were the same shape. They were likely piscivores, or fish-eaters, adapted to catching fast prey in the water. Examples include the genera Paleorhinus, Rutiodon, and Mystriosuchus.

Paleorhinus
Paleorhinus

Another type was the brachyrostral phytosaur, which had a massive, broad snout. These animals were heterodont, possessing different types of teeth. They had prominent fangs in the front and blade-like teeth in the rear for slicing meat. Taxa like Nicrosaurus and Smilosuchus used these powerful jaws to hunt terrestrial animals.

Smilosuchus adamanensis
Smilosuchus adamanensis

Finally, altirostral phytosaurs, such as Pseudopalatus, had intermediate snout shapes. These were likely generalist feeders that could eat a variety of different foods.

Despite their crocodile-like appearance, phytosaurs had several unique anatomical differences. One major difference was their nostril placement. Unlike modern crocodiles, which have nostrils at the tip of the snout, phytosaurs had nostrils located near or above the eyes. This adaptation allowed them to breathe easily while most of their body remained submerged.

Smilosuchus-reconstructions-Jeff-Martz-600-px-tiny-Oct-2014-Tetrapod-Zoology
Smilosuchus-reconstructions-Jeff-Martz-600-px-tiny-Oct-2014-Tetrapod-Zoology

They were also heavily armored. Phytosaurs possessed bony scutes for protection and a dense arrangement of gastralia, or abdominal ribs, to reinforce their bellies. Their ankle structure was also much more primitive than that of any modern crocodile. Additionally, they lacked the true bony secondary palate that helps crocodiles breathe with full mouths.

Phytosaur teeth also featured unique characteristics. A study by William L. Abler found that phytosaur teeth had very fine serrations. These serrations were so thin they resembled tiny cracks in the tooth. Unlike the dinosaur Albertosaurus, phytosaurs lacked an ampulla, which is a round void at the base of a serration. In other animals, an ampulla helps distribute force and prevents cracks from spreading through the tooth. Because phytosaurs lacked this feature, their teeth were vulnerable to crack propagation. Based on tooth wear, most phytosaurs were carnivores or piscivores, though some specialized in eating hard invertebrates.

Rutiodon validus 21DB
Rutiodon validus 21DB

Phytosaurs had a nearly global distribution during the Triassic period.

Nicrosaurus1Zittel
Nicrosaurus1Zittel

Fossil evidence has been recovered from Europe, North America, India, Morocco, Thailand, Brazil, Greenland, and Madagascar. Some fossils may even extend their range into the Early Jurassic. In China, the specimen Diandongosuchus might represent a phytosaur, though this is not yet certain. This wide distribution shows they were capable of thriving in many different geographic regions.

Researchers have also studied how these animals moved and lived. While many were aquatic, some evidence suggests they could move on land. The Apatopus ichnofossil indicates they may have had an erect gait, similar to their archosaur relatives. Some species even moved toward different lifestyles. The genus Nicrosaurus evolved longer limb bones and a deeper pelvis, suggesting a more terrestrial lifestyle.

Smilosuchus adamanensis flipped
Smilosuchus adamanensis flipped

Conversely, the genus Mystriosuchus became highly specialized for marine environments. Mystriosuchus had paddle-like limbs and a laterally compressed tail used for swimming in the sea.

Understanding the history of phytosaur discovery is also important. The first fossils were found in the early 1800s, but scientists were initially mistaken about their diet. In 1828, G. Jaeger named a species "Cylindricodon," believing the animals were herbivores because of mud in their teeth.

Angistorhinus grandis
Angistorhinus grandis

It was later realized they were actually meat eaters. In 2005, Paul Sereno helped provide a clearer definition of the Phytosauria clade. He defined it using Rutiodon carolinensis as a reference point. Today, scientists continue to study how these reptiles relate to the evolutionary split between crocodile-line archosaurs and bird-line archosaurs.

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🖼️ Images & Media (30)
File:Smilosuchus-reconstructions-Jeff-Martz-600-px-tiny-Oct-2014-Tetrapod-Zoology.jpg
Smilosuchus-reconstructions-Jeff-Martz-600...
File:Phytosaur skull.jpg
Phytosaur skull.jpg
File:Angistorhinus grandis.jpg
Angistorhinus grandis.jpg
File:Belodon.jpg
Belodon.jpg
File:Calamosuchus arenaceus (holotype, SMNS 80737).jpg
Calamosuchus arenaceus (holotype, SMNS 80737).jpg
File:Diandongosuchus fuyuanensis.jpg
Diandongosuchus fuyuanensis.jpg
File:Rutiodon validus 21DB.jpg
Rutiodon validus 21DB.jpg
File:Nicrosaurus1Zittel.jpg
Nicrosaurus1Zittel.jpg
File:Paleorhinus.jpg
Paleorhinus.jpg
File:Protome batalaria.jpg
Protome batalaria.jpg
File:Redondasaurus bermani at CMNH 04.jpg
Redondasaurus bermani at CMNH 04.jpg
File:Rutiodon BW.jpg
Rutiodon BW.jpg

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