KILLER BIRDS:      Ancient Predators of      South America      by Herculano Alvarenga12              South American Explo...
Some 65 million years ago, dinosaurs of many kinds and in large size that can survive on insects, seeds, and mushrooms.num...
those of large bears. But fiercer than anyof these mammal predators, an even morefearsome killer appeared: the phorusrhac-...
there are almost entire skeletons. Fossil      terror birds dwarfed in ferocity anything                                  ...
Sculpting Terror Birds                                                                                                    ...
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Killer birds. ancient predators of south america

  1. 1. KILLER BIRDS: Ancient Predators of South America by Herculano Alvarenga12 South American Explorer
  2. 2. Some 65 million years ago, dinosaurs of many kinds and in large size that can survive on insects, seeds, and mushrooms.numbers roamed the earth. Pterosaurs wheeled in the air, swoop- As the Cenozoic dawned, an important geological event wasing down on fish and small animals. Flying insects flitted across the taking place. The tectonic shifting that had split off Southmuggy swamps. In the dense undergrowth, hissing reptilesstalked America from Africa slowed. South America, now an island,their prey, huge centipedes foraged in the bogs, and snakes slithered was cut off from the rest of the world. This had significantamongst the giant ferns. This was the humid and lush world of the results: evolution in South America took a course completelyCretaceous period. independent from the rest of world. Over time some of the Suddenly, a massive meteorite, 10-12 km in diameter, crashed most unusual animals evolved--large beasts,into the Gulf of Mexico. The awesome energy released by this such as the Pyrotheria, Astrapotheria,impact threw up a vast tidal wave 100 m high, and sent it racing Notoungulata, and Litopterna. Theout in all directions. Slamming against the earth with tremendous giant herbivores like the toxodonts,force, the colossal wave swept inland, leveling whole forests and glyptodonts, several species of giantflooding vast stretches of land. The same explosive ground sloths, the macrauchenias andforce that caused the wave hurled innumer- other groups of extraordinary mammalsable tons of rock and earth high into grazed in the fields of South America. In sizethe stratosphere, darkening the sun. these mammals were much like the animals weTemperatures plummeted. Around might see on a trip to Africa, but the comparisonthe world, lakes froze and glaciers ends there. In other respects, these giants were alto-stretched down the valleys ever gether different from any mammals we know today.southward across a gloomy plan- Unfortunately it is difficult to compare these exoticet. Acid rains scorched the earth’s beasts to living animals because they all belonged tosurface, withering plant life. The orders of mammals now extinct.cataclysm wiped fully 85% of allspecies off the face of the earth.Not just the dinosaurs perished in The Carnivoreshuge numbers but also many spe- The big carnivores we know, like bears, lions,cies of marine reptiles, fish, and Drawing by Eduardo Brettas wolves, and other felids and canids (cats andmollusks. The Cretaceous period- dogs) evolved in the northern hemisphere.- the Mesozoic Era and the Age of Reptiles--was over. The world None were present in South America during the Cenozoicwould never be the same again. period. Instead, evolution gave rise to large numbers of her- The mass extinction of dinosaurs, marine reptiles and fish bivores. In time, these would become food for carnivores.that so dramatically ended the Cretaceous period marked the Scavengers would appear as well, to feed on the dead andbeginning of another--the Cenozoic era--the Age of Birds and dying. Over millions of years, several varieties of herbivo-Mammals. Remarkably, some mammals, birds, turtles, small croc- rous marsupials evolved into efficient meat-eating mammalsodiles, lizards, snakes and amphibians survived and, facing little --fleet-footed predators like the saber-toothed marsupialcompetition, multiplied in an empty world. Micro-refuges and Tylacosmilus and others of the family Boryaenidae, like thethe scarcity of food fit for large animals benefited animals of small Artodictis and Arminiheringia, which had skulls as big as Drawing by Stacey Burgess © Photo: Stacey Burgess © Number 72, Summer 2003 13
  3. 3. those of large bears. But fiercer than anyof these mammal predators, an even morefearsome killer appeared: the phorusrhac-id, or carnivorous terror bird.The Giant Birds The Phorusrhacidae comprise a groupof flightless birds similar to and relatedto the cariamas we see today. Duringthe Cenozoic, they emerged as unrivaledpredators and ruled the roost for millionsof years. The biggest of these birds wastop predator. To date, at least 17 species of phorus-rhacid belonging to some 13 distinct gen-era have been uncovered. These TerrorBirds ran down their prey on large pow-erful legs. The Phorusrhacidae had smallwings, but enormous heads and beaks.The body of the smallest species, thePsilopterus lemoinei, was about the sizeof a harpy eagle. About 80 cm in height, itweighed some 7-8 kg, but boasted a moremassive skull and beak. The Brontornis Photo: Stacey Burgess ©burmeisteri was the largest of the species.This giant bird stood nearly 3 m tall and only ten to twenty times larger and stron- Tertiary, there were plenty of animals toweighed a whopping 500 kg. Brontornis ger. Lastly, Terror Birds were very fast. hunt. Animals of the order Litopternawas quite possibly the largest bird that An ostrich can run 40 mph for up to 30 were similar to horses or small deer--easyever walked the earth. The Phorusrhacus minutes. Some of the Terror Birds could kills for a phorusracid. In Taubaté Basin,longissimus and Paraphysornis brasil- match or surpass this. A Paraphysornis where we excavated the Paraphysornisiensis were each somewhat smaller than brasiliensis could easily run down its brasiliensis, there were also a lot ofBrontornis, but larger than an ostrich, prey and slash it to death. During the notoungulate (Taubatherium paulacoutoi)tipping the scales at 130-180 kg. Theyterrorized even the largest herbivores ofthe prehistoric South American plains. To visualize one of these giant birds,imagine an ostrich but with larger, morepowerful legs and neck, armed with mas-sive claws. Also, unlike an ostrich’s smallhead, the head of a Terror Bird was morelike that of a horse. An ostrich (the world’slargest living bird today) can swallow anapple, but a phorusrhacid could swallowa medium-sized dog in one gulp. Thebeak of a Terror Bird was massive as well,similar to the beak of a living macaw’s Photo courtesy of Paleontological Reseach Istitute (PRI), Ithaca, New York 14 South American Explorer
  4. 4. there are almost entire skeletons. Fossil terror birds dwarfed in ferocity anything remains of phorusrhacids are known you might see today on a safari to Africa. from all epochs of the Tertiary in Brazil, As efficient, bloodthirsty predators, only Uruguay and Argentina. The oldest is Tyrannosaurus rex and some of the other from Paleocene of Itaborai (southeast large dinosaurs outdid the Terror Birds. Brazil), and the most recent is from the Three million years ago, the two con- Pliocene of Uruguay. tinents of South and North America Between 1976--78, when I was young, collided. Over the land bridge that is I spent some of the most exciting times now Panama the primitive cats, dogs, of my life excavating fossils. In Taubaté and bears of North America crossed into Basin (southeastern Brazil), just 10 km South America. Among the most danger- from my home, I came across the frag- ous newcomers were the saber-toothed mentary bones of a phorusrhacid spread tiger (Smilodon) and the jaguar (Panthera out over some 100 sq. meters. After onca). The Terror Birds were no match for recovering nearly 80% of the bird, I spent these big cats. Over the following centu- the next several years assembling these ries the intruders hunted down and killed bone fragments into an almost complete entire species of Terror Birds. There was skeleton. This specimen is now known as a single exception. One of the larger pho- Paraphysornis brasiliensis and can be found rusrhacids, the Titanis walleri, reached in the Natural History Museum of Taubate North America. About the size of a large in São Paulo, Brazil. It is one of the most ostrich and weighing 120 kg, it ranged Drawing by Eduardo Brettas spectacular Terror Bird specimens we over the southwestern United States have. During these same excavations, I until the beginning of the Pleistocene.bones. This animal was about the size of uncovered several bones of Then this last member of the fantastica living capybara (Hydrochoerus), and Taubatherium, a medium-size notoungu- Phorusrhacidae family died out as well.weighed about 30-40 kg – a tasty morsel late, along with bones of other creaturesfor a hungry Terror Bird. such as fish, a small crocodile, and other The Phorusrhacidae can be divided into small mammals and birds. SUGGESTED READINGS:five sub-families, each with its own dis- The bones of Terror Birds excavated to Alvarenga, H. 1982. Uma gigantesca avetinct skeletal proportions. Differences in date allow us to speculate about the kind fossil do Cenozoico brasileiro: Physornisthe size of the tarsometatarsus (the large of life they might have led. It’s easy to brasiliensis sp. n. Anais da Academia brasil.bone in the lower part of a bird’s leg that imagine a pack of five or six phorusrhacids Ciencias, 54:697-712.connects the tibia and toes) occur in dif- ambushing a giant sloth, or other beasts as big as a bison or rhinoceros. Stalking Alvarenga, H. and E. Hofling. In press.ferent families. In the Brontornithinae, the their prey, Terror Birds might well have Systematic revision of the Phorusrhacidaetarsometatarsus is proportionally short, hunted much like the big cats, hyenas, or (Aves: Ralliformes). Papeis Avulsos dewhich makes them slow runners, like the wild dogs of today. Zoologia; public. of the Museu de ZoologiaParaphysornis brasiliensis. Much like the But there’s a difference. The lion (the da Univ. S. Paulo.hyenas we see in Africa, Brontornithinaeprobably scavenged for food, preying on largest of the African carnivores) weighs in Marshall, L. 1994. The Terror Birdsthe sick and the young. The sub-families about 200 kg, a leopard about 80 kg, and of South America. Scientific American,Phorusrhacinae and Patagornithinae all a cheetah 70 kg. These look like impres-had large tarsometatarsi. While not as big sive weights until compared with theas the Brontornithinae, this feature would Phorusrhacidae It would take at least twomake them faster. These were, no doubt, lions to equal the weight of a Brontornis Hercilano Alvarenga is the directorthe best hunters among these giant birds. burmeisteri, the largest of these fowl, of the Museu de História Natural deToday, in South America, there are caria- which weighed in at a hefty 400-500 kg. Taubaté, (SP-Brazil) where he worksmas (family Cariamidae) that, in pairs, or Even the smaller Devincenzia weighed on existing and fossil birds and thein small groups, forage for food in small some 200 kg, while an adult Paraphysornis paleontology of the Taubaté Basin.fields and scrubs. Although there is little brasiliensis weighed about 180 kg, and the He has done research in museums insupporting paleontological evidence, it’s Phorusrhacos longissimus 130 kg. North America, Africa, Europe andpossible that phorusrhacids also hunted The Terror Birds of Cenozoic South South America, and has publishedin small groups, using their huge beaks America were far and away the most ter- more than fifty scientific papers, amongand large claws to kill their prey. They rifying and ferocious creatures of that age them a complete systematic revision ofhunted more like the Cretaceous dinosaurs --far more fearsome than any lion, tiger, the Phorusrhacids (2003). He can beVelociraptor and Deinonychus than pres- or bear we know today. For 62 million emailed at: carnivores such as bears, lions, years during the Cenozoic period, thesepumas, or jaguars. giant killer birds reigned supreme in The fossil record of these giant birds is South America, outrunning and slashingincomplete. For some species, all we have to death any prey that crossed their a few bone fragments, but for others The spectacular battles of these huge lllll Number 72, Summer 2003 15
  5. 5. Sculpting Terror Birds Photo: Stacey Burgess © have been in English). So I had to improvise. I used some nice skeletal reconstructions of existing birds along with written descriptions of Andalgalornis and Titanis. I start with the armature. This serves as the skeleton of the animal and is made of copper and steel wire. I then build up layers of poly- mer clay over this to simulate the muscles of a real bird. For the musculature, I referred to the Manual of Ornithology, a wonderful book on avian anatomy with detailed illustrations of the musculature of Rails. Rails are mod- ern day birds that are somewhat similar to Phorusrhacids in build. Once I finish the musculature I start on theby Stacey Burgess who’ve done the original investigations. details. I do this using a small stylus. Since I know of no feather impressions of Terror Not all prehistoric animals are well known, birds the integument was an educated guess I start all of my sculptures by research- however, and this was the case with the on my part. I used images of the feathers ofing the subject of the drawing. I like to Terror Birds. I was unable to get copies of the the Seriemas, the closest living relative ofwork from images of the original fossils or original papers published on Andalgalornis Andalgalornis and also my own pet birds.from skeletal diagrams drawn by scientists (and even if I could have they would not I have a Yellow Naped Amazon and two Cockatiels; these guys served as the greatest inspiration for the details of my sculpture. And I used my Amazon as a model as I sculpted the feathers one feather at a time. As pigment is rarely or (in the case of this bird) not at all preserved, I had to speculate on the coloration. I wanted something that was flashy but was also realistic a bright pink or green predator would have hard time catching prey. In the end I decided on the black and white after watching how well native chickadees vanish into the grass. Andalgalornis may have needed to hide in grass and forests and a dark and muted color- ation would help it do this. And that is basically how I built this model. All art depicting extinct animals involves a good deal of speculation. One can never be entirely certain of how an animal looks when it’s been extinct for over 2 million years. Nonetheless, I feel that my sculptures are relatively accurate representations of the Photo: Stacey Burgess © South American Terror Birds. 16 South American Explorer