Papagaios, Life & Times on a Speculative Archipelago

Extracts from Toledo S., Galvin D. 2018. ‘New fossil of predator-prey mutual death sheds light on the hunting strategy of genus Longicorpus’ Ecology and Evolution.

The lizards of the Papagaios Archipelago are split into two types: Eupapagolacertidae which tend to be small insectivores and frugivores, and Papagotitanidae whose members range from 50cm to almost four metres, according to some estimates of extinct species. The Papagotitans themselves are traditionally split into three groups – Platydonts, Petrodermids and Macrocaudates. While the latter two groups tend to stray little from the typical body plan of their group, the macrocaudates showcase a wide range of shapes, sizes and lifestyles, which goes to explaining why they are more species rich than the other two groups combined.

Several genera of macrocaudates filled the role of apex predator on their islands including Archaeocaudate, Corneops and Monolophus, with the consensus being they lived like Komodo dragons, which fits with their size and convergent anatomy. The lifestyle of an equally large but more distantly related macrocaudate, Longicorpus, has been more difficult to determine.

Longicorpus is a genus containing three species, all broadly similar in size and appearance. They share many of the typical macrocaudate features, but in proportions that are unusual. The most complete specimen is conservatively estimated at being 3m long – though most of the tail is missing so it is likely longer. The genus is strange, however, in having a torso almost three times as long as that over other macrocaudates, proportional to its overall length. It also has legs half the expected size, though with oversized feet. This would have resulted in a crocodile-like appearance.

It had therefore been assumed that Longicorpus lived much like a crocodile, hunting from and in the water. This view has been challenged from the time the first fossils were discovered, with critics pointing out Longicorpus’ lack of aquatic adaptations. A new specimen discovered by this team at the Pico Vitorioso site raises a new possibility.

The fossil shows a specimen of Longicorpus carlosi locked in combat with an as yet unidentified rhynchothrix bird. The bird would have stood at 1.5m tall and had strong legs to flee from or kick predators. In this case, however, escape seemed impossible. The L. carlosi is holding the bird’s throat in its jaws while its characteristic long body and muscular tail wrap around the bird’s torso. Several of the bird’s ribs are cracked without healing, meaning it likely occurred during the struggle. There is also a bit on the bird’s right leg that went deep enough to damage the bone.

We believe L. carlosi was an ambush predator that sprang from cover and bit the rhynchothrix on the leg, wounding it and preventing escape. L. carlosi then wrapped its body around the bird, trapping one leg as it coiled to further prevent escape. Thus, wrestling the bird into submission, the fatal blow was delivered via crushing of the windpipe. Had it not been for an untimely landslide or flashflood, the bird would have been consumed and L. carlosi gone about its day.

This method of subduing prey is similar to the constriction seen in some snake species, though the presence of legs and a thicker body relative to length would make it less effective at coiling. Instead, a partial coil combined with large grasping feet served to exhaust the prey to a point at which it was safe to kill without fear of injury. This fossil, and the relative sizes of the animals, suggest the various rhychothrix species were Longicorpus’ preferred food source, but we should be mindful of bias and consider that Longicorpus would likely be a generalist eating any large animals it could catch.