The wrong phoenix

While glaciers retreat, fossil hunting has become increasingly important in Antarctica. Many new areas are becoming ice free, allowing human drones to survey unexplored ground. Excavating with drones was complicated in the first models, but across the following centuries paleontological rovers became more effective and precise than an entire crew of scientists. Yet there is something that even rovers cannot do: finding complete fossils. Complete articulated fossils are rare in general, but 34 million years of Antarctic glacier movement and consequent fossil erosion make them even rarer.

But what does it mean to have only a fraction of an entire fossil? It means that you practically know nothing. What does it mean to have a fraction of a fossil from a continent where the paleobiota is almost unknown? It means you are groping in the dark, hoping to eventually find a speck of light.

That is what happened with a very famous and incredibly important fossil found in 2447 in the already known La Meseta Formation, from Seymour Island. This geological formation has produced fossils that span across a large portion of the Cenozoic, from the Late Paleocene to the Early Oligocene. At that time, climate was much hotter in Antarctica, with plant associations similar to those of today’s tropics and subtropics. In this environment, a relatively large number of fossilized but fragmentary vertebrates are known, including marine species like the giant penguin Anthropornis and terrestrial species like the ungulate Antarctodon.
At the end of March 2447, a stunning fossil from this formation provided evidence of something palaeontologists had guessed for centuries: the first Antarctic sebecid. This reptile group is related to modern crocodiles and looked very crocodile-like, with the exception of being land-dwelling species with serrated teeth. Sebecids are known to have lived in South America and Europe during the early Cenozoic, and since South America was united with Antarctica in the past, many scientists suspected that they lived in Antarctica at least briefly. The idea was supported by the resemblance of Antarctic biota with South American fauna, with findings proving the existence of Meridiungulata ungulates, terror birds and several marsupials. Additionally, we know that some plants (like eucalypts) and animals (both warm-blooded like marsupials and cold-blooded like meiolanids) reached Australia by crossing Antarctica from South America.

Because of this, the first undisputed evidence of sebecids in Antarctica was welcomed by the scientific community not with surprise, but with a “Boy do I hate being right” exclamation.
Despite that, the fossils of this crocodile were incredibly fragmentary, with parts of the upper cranium, some teeth and osteoderms. An interesting detail among the remains was one osteoderm in particular, a dorsal one, extremely flattened and elongated, like a paddle. It was initially speculated that most dorsal osteoderms had this shape, giving the animal an intimidating yet beautiful look, a sort of sail of scales running from head to tail, creating a giant dorsal crest. Another interesting feature of this reptile was its dentition, relatively domed and less serrated, probably an adaptation to a durophagous diet of turtles and shelled molluscs. The official scientific name, Lophosuchus cortidens (X. Whuong & M. M. Muscioni 2452), was erected five years after the discovery. The name means “crested crocodile with short teeth”. The scientific team also gave it a vernacular name, Fèntòulong, meaning Phoenix-headed dragon.

A large debate started about the usefulness of the sail-like osteoderms of this sebecid and how they were arranged on the back. Many speculative reconstructions were made, but none could find a real function for these bones beyond the usual sexual display hypothesis. Without a larger fossil record, every hypothesis was as speculative as the others.
Finally, after more than two centuries, the answer came: in 2689, in a new geological formation called San Martin Lagerstätte, a nearly complete articulated reptile tail was found. It was immediately assigned to Lophosuchus: the tail had the same flattened osteoderms seen in the holotype, but they were limited only to the posterior part. The rest of the caudal vertebrae were covered by normal osteoderms, suggesting that, unlike previous hypotheses, the sail-like osteoderms did not cover the entire back but were arranged in a "thagomizer", like the famous dinosaur Stegosaurus.

Paleopathologists also discovered that one of the flattened osteoderms had healed from a fracture, seemingly caused by the collision with something hard. It was then suggested that these osteoderms were used more like weapons during intraspecific battles. They were probably also used for defence against other predators, since Fèntòulong, despite reaching up to 3 meters in length, was not the largest predator known from the Paleocene-Eocene of Antarctica. A large terror bird, the size of an ostrich, had already been known since the 21st century, and new fossils of this animal were found in the following years. And according to other, not yet described findings, there were even larger predators dwelling in Antarctica at the start of the Cenozoic, something much more frightening than a land crocodile and a giant bird...