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Kelenken guillermoi

By Scott Reid

Etymology: For Kélenken, the Bird of Prey Spirit of the Tehuelche Tribe

First Described By: Bertelli et al., 2007

Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Saurischia, Eusaurischia, Theropoda, Neotheropoda, Averostra, Tetanurae, Orionides, Avetheropoda, Coelurosauria, Tyrannoraptora, Maniraptoromorpha, Maniraptoriformes, Maniraptora, Pennaraptora, Paraves, Eumaniraptora, Averaptora, Avialae, Euavialae, Avebrevicauda, Pygostaylia, Ornithothoraces, Euornithes, Ornithuromorpha, Ornithurae, Neornithes, Neognathae, Neoaves, Inopinaves, Telluraves, Australaves, Cariamiformes, Phorusrhacoidea, Phorusrhacidae, Phorusrhacinae

Status: Extinct

Time and Place: Between 15.5 and 13.8 million years ago, in the Langhian age of the Miocene of the Neogene

Kelenken is known from the Collón Curá Formation of Rio Negro Province, Argentina

Physical Description: Kelenken was a Terror Bird, a type of large flightless terrestrial dinosaur from the late Cenozoic era, mostly in South America though a few reached North America when the continents collided. These were some of the top predators of their environments, built for chasing down food over long distances and then using their monstrous beaks to tear into flesh. Kelenken was one of the biggest members of the group, about two meters tall, and it had one of the largest known skulls of any bird, with fused bones to give it significant strength in its head and strong bire force. Its limbs were very robust, probably allowing for powerful movements of the legs. It had very small wings, as other Terror Birds did, and as such they probably weren’t used very much (think of the arms of Carnotaurus but the bird version). It had a long, winding neck, and its head was mostly beak. The beak was hooked at one end. It had a short tail, though we don’t have any feather impressions to know if it had any sort of feather decoration at the end of it. It would have had a huge bite force, and it possibly was a faster runner than other Terror Birds.

Diet: Kelenken primarily fed on large animals, especially faster moving ones such as hoofed mammals

Behavior: Kelenken probably spent most of its time chasing down its prey, though it’s uncertain how. It’s possible that it would chase down prey, catch it, and shatter its bones with its beak by repeatedly pecking at it (if… pecking is an accurate word to use with such a huge beak doing the pecking). It’s also possible that it would chase down smaller prey, pick it up, and shake it vigorously to break the prey’s back. It also possibly scavenged off of prey. Honestly, it seems likely that Kelenken would utilize all these strategies, and those not even come up with, to get any prey it could in an opportunistic fashion.

By Michael B. H.

Kelenken was a fairly fast animal, and probably able to run for longer distances. As its environment was transitioning to an open grassland rather than a forest, this ability to run moreso than its earlier relatives was probably a direct adaptation for that open habitat. As such, Kelenken would have been extremely alert and on the lookout, both for food and for potential dangers, as it was tall enough to poke out above the grass and be visible to anything looking for it. Kelenken could fight with others of its species and against other animals both with its beak and with its feet, as it had very robust legs that would have been good for kicking, possibly very rapid and sharp kicks.

As only a few specimens of Kelenken are known, it’s difficult to determine its social behavior, especially since its closest living relatives are the Seriemas - a much smaller sort of dinosaur. Still, it’s possible to at least glean some behavioral patterns from seriemas. It’s possible that, like living seriemas, Kelenken only spent its time in pairs and small groups, which may have worked together cooperatively to take down larger mammalian sources of prey. It’s also possible that it may have been territorial over its nests, with breeding pairs avoiding other Kelenken and fighting with those they come across. This is all speculative, but would make sense given the environment and size of the animals. Kelenken, being a bird, almost decidedly took care of its young, though we cannot know if both parents took care of the young as in modern Seriemas, or if only one parent did the job at a time as in modern flightless birds. More fossils might be able to clear up this picture, though of course, it’s possible we’ll never know.

By Ripley Cook

Ecosystem: Kelenken lived in the part of the Miocene that was the hottest, called the Middle Miocene Climatic Optimum. This was immediately followed by drastic cooling. Thus, Kelenken lived in a uniquely warm period of the time in which Terror Birds dwelled. The formation was surrounded by extensive rivers and lakes, as basins formed in South America due to tectonic plates separating. This environment was a growing grassland, with the pampa overtaking the old deciduous forest that had once been there.

Kelenken is the only dinosaur known from the formation, but there were many different types of mammals present. There were the heavy-bodied hoofed mammals Protypotherium, Epipatriarchus, and Interatherium; the smaller hoofed mammals Hegetotherium and Pachyrukhos; the weird fast hoofed mammal related to Macrauchenia, Theosodon; armadillo relatives such as Proeutataus, Paraeucinepeltus, Peltephilus, Prozaedyus, and Stenotatus; the anteater relative Neotamandua; the rodents Galileomys, Guiomys, Maruchito, Microcardiodon, Neosteiromys, Protacaremys, Acarechimys, Alloiomys, Megastus, Neoreomys, Prolagostomus, and Stichomys; the new-world monkey Proteropithecia; the sabre-toothed marsupial Patagosmilus; and the extinct shrew opossum relative Abderites. There were also reptiles such as boa relatives like Waincophis, lizards, and turtles like Chelonoidis. There was also the horned frog Wawelia.

Kelenken probably would have hunted a variety of these things, especially the hoofed mammals, though some would have been too big for it to eat. It definitely would have been in direct competition with Patagosmilus, which probably would have specialized on different prey than Kelenken.

Other: Kelenken is most closely related to phorusrhacids such as Phorusrhacos and Titanis, two of the other more famous genera in this group.

~ By Meig Dickson

Sources under the Cut

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