In the right circumstances birds can evolve into giants. In the vast majority of cases they have done this on oceanic islands in the absence of any large land predators and most of these extinct giant birds are decidedly lacking when it comes to predatory ferocity, as birds like the moa and elephant bird attest; big, but decidedly vegetarian animals. However, a long-legged bird living in South America several million years ago, probably very similar to the living seriemas (Cariama cristata and Chunga burmeisteri), gave rise to a group of birds collectively known as terror birds (, technically known as phorusrhacids) and as their name suggests they were not the sort of feathered critters you would find nibbling nuts at a bird-table. They were big birds; the smallest of the 17 known species were at least 1m tall, while Brontornis burmeisteri stood as high as 3m and may have weighed as much as 350–400 kg, but even B. burmeisteri may have looked a bit pathetic next to an even bigger species, the skull of which was discovered by a high school student in Patagonia in 2003. There’s every possibility these animals were the largest birds ever to have lived and all of them were undoubtedly fierce predators. Why these nightmarish birds came to evolve in South America is not fully understood, as no other place on Earth has ever produced a group of predatory giant birds. Gigantism in birds is normally associated with herbivory, yet whatever conditions prevailed in South America many millions of years ago allowed the evolution of a varied group of feathered carnivores that were around for a huge stretch of time; from around 60 million years ago to about 1.8 million years ago, which goes to show how successful these birds were.
Terror birds - Phorusrhacidae
A selection of terror birds. A – Brontornis burmeisteri; B – Paraphysornis brasiliensis; C – Phorusrhacos longissimus; D – Andalgalornis steuletti; E – Psilopterus bachmanni; F – Psilopterus lemoinei; G – Procariama simplex; H – Mesembriornis milneedwardsi and the silhouette of a man (1.75 m high) for scale (Herculano M.F. Alvarenga)
Following the extinction of the dinosaurs, many niches in the Earth’s ecosystems were left wide open for the vertebrate survivors – the mammals, birds, and remaining reptiles to evolve into, and for a while, apparently, the terror birds had a power struggle with the mammals for the dominance of the terrestrial ecosystems in South America. Many of them were big and powerful enough to have been the top predators at the time, and many mammals were definitely their prey.
All but one of the terror birds paleontologists know of today have been unearthed in South America. One species (Titanis walleri) managed to reach North America, and it appears to have been quite a success, surviving for more than three million years until it disappeared around 1.8 million years ago – the last of its kind to become extinct. Even though this American species was not the biggest terror bird it must have still been a terrifying animal. Its vital statistics are impressive: 1.4 – 2.5m tall and 150kg in weight. It also had an immense, hooked bill and with such an impressive beak it could have probably swallowed a lamb-sized animal in one gulp.
Although we can piece together the skeletons of the terror birds it’s impossible to know what their plumage was like. However, we can look at living birds for clues, and if the other flightless birds are anything to go by, the terror bird’s feathers may have been rather hair-like. Like the vast majority of flightless birds, terror birds had stubby little wings, but what they lacked in the wing department they more than made up for with their long, powerful legs that ended in large feet and long claws. These legs gave these animals a good turn of speed and it has been estimated that some species of terror bird could reach speeds of 100kmh – comparable to a cheetah. The combination of running, big talons and a monstrous beak made the terror birds very effective predators. It is possible to imagine one of these birds snapping at the hooves of ancient mammals as it pursued them across the grasslands of the Americas. Smaller animals were probably immobilized with the sharp talons before being torn apart by the fearsome hooked bill or even swallowed whole after having their skull crushed in the bird’s vice-like grip. Larger prey animals may have been disemboweled with Kung-Fu styles kicks and it is even possible that crushing kicks may have been used to crack the larger bones of big prey to get at the nutritious marrow within.
Titanis spp. skull
Skull of a terror bird (Titanis walleri). This is about 50cm long (Ross Piper)
Even if the last terror bird became extinct around 1.8 million years ago, these were successful animals that, as a group, survived for more than 50 million years, some of them even taking on the mantle of top land predator in the ecosystems in which they lived. However, around 2.5 million years ago (during the Pliocene epoch) something happened that completely changed the course of life for South America’s unique animals – the Great American Interchange. The land bridge that eventually appeared between North and South America, what is now known as the Isthmus of Panama, allowed animals from the north to migrate into South America. Among them were lots of predatory cats and it has been proposed these animals were so effective as predators that they outcompeted the terror birds. The talons and beaks of the terror birds were no match for the teeth, claws, and hunting prowess of the invaders from the north. This is a very neat answer for the cause of the extinction of the terror birds, but, the extinction of successful animals is very rarely due to one factor, but a combination of events. Perhaps climate change directly affected the terror birds by changing their habitats and the populations of their prey. Although there is a great deal we don’t know about the life and times of the terror birds we do know that one of their number somehow managed to cross into North America and spread through the southern states. For a long time it was assumed that the American terror bird spread north via the land bridge, but analysis of its ancient bones paints an alternative picture as they appear to have reached the southern states of America before the land bridge formed. Perhaps falling sea levels, due to the growth of the polar ice sheets, revealed a path of ‘stepping stones’ across islands in the gap of open ocean in what would become the Isthmus of Panama, allowing the giant birds to colonize the prehistoric North America. Maybe other species of terror bird, the remains of which are as yet undiscovered, also reached North America before following the rest of their amazing kind into the pages of earth history.
ในสถานการณ์ที่เหมาะสมนกสามารถพัฒนาเป็นยักษ์ ในกรณีส่วนใหญ่ พวกเขาได้กระทำนี้บนเกาะมหาสมุทรของล่าใด ๆ แผ่นดินใหญ่ และส่วนใหญ่ของนกยักษ์เหล่านี้สูญจะเด็ดขาดเมื่อมันมาถึงความดุร้ายโหดร้าย เป็นนกเหมือนนกโมอาและช้างนกยืนยัน สัตว์ใหญ่ แต่เด็ดเจ อย่างไรก็ตาม ขายาวนกอาศัยอยู่ในอเมริกาใต้หลายล้านปีที่ผ่านมา คงคล้าย seriemas นั่งเล่น (Cariama cristata และ Chunga burmeisteri), ให้กับกลุ่มของนกที่เรียกโดยรวมว่านกร้าย ( เป็นที่รู้จักกันทางเทคนิคแล้วเป็น phorusrhacids) และเป็นชื่อแนะนำไม่ใช่การเรียงลำดับของดูแลรักษา critters เยี่ยม จะหาถั่ว nibbling ที่นกตาราง พวกนกใหญ่ เล็กที่สุดของ 17 รู้จักพันธุ์สูง อย่างน้อย 1 เมตรขณะที่ Brontornis burmeisteri ยืนสูงถึง 3 เมตร และอาจหนัก ถึง 350-400 กก. แต่อาจได้ดู burmeisteri แม้เกิดน่าสงสารมากอยู่ติดกับสายพันธุ์แม้แต่ใหญ่ กะโหลกศีรษะซึ่งค้นพบ โดยนักเรียนมัธยมในแทสมาเนียใน 2003 มีทุกความเป็นไปได้ที่สัตว์เหล่านี้มีนกที่ใหญ่ที่สุดเคยไปมีชีวิตอยู่ และทั้งหมดถูกล่ารุนแรงอย่างไม่ต้องสงสัย ทำไมนกเหล่านี้ nightmarish มาจะพัฒนาขึ้นในอเมริกาใต้ไม่เป็นอย่างที่เข้าใจ เป็นอื่น ๆ ไม่มีในโลกเคยมีผลิตกลุ่มนกยักษ์ที่โหดร้าย Gigantism ในนกเป็นปกติเกี่ยวกับ herbivory แต่เงื่อนไขใดแผ่ขยายไปในอเมริกาใต้หลายล้านปีได้วิวัฒนาการ carnivores เยี่ยมที่สถานสำหรับยืดใหญ่เวลา กลุ่มแตกต่างกัน จากประมาณ 60 ล้านปีที่ผ่านมาประมาณ 1.8 ล้านปีที่ผ่านมา ซึ่งไปแสดงที่นกเหล่านี้ประสบความสำเร็จอย่างไรความหวาดกลัวนก - Phorusrhacidaeการเลือกนกก่อการร้าย A – Brontornis burmeisteri B – Paraphysornis brasiliensis C – Phorusrhacos longissimus D – Andalgalornis steuletti E – Psilopterus bachmanni F – Psilopterus lemoinei G – Procariama simplex H – Mesembriornis กลอรีออฟอินเดียและรูปเงาดำของมนุษย์ (1.75 เมตรสูง) สำหรับสเกล (Herculano M.F. Alvarenga)ต่อการสูญพันธุ์ของไดโนเสาร์ ตรงไหนมากในระบบนิเวศของโลกสมมติเปิดกว้างสำหรับหลอดผู้รอดชีวิต – เลี้ยงลูกด้วยนม นก และสัตว์เลื้อยคลานที่เหลือสามารถพัฒนาเป็น และในขณะ เห็นได้ชัด นกร้ายได้ต่อสู้อำนาจ ด้วยเลี้ยงลูกด้วยนมสำหรับการครอบงำของระบบนิเวศภาคพื้นในอเมริกาใต้ หลายของพวกเขามีขนาดใหญ่ และมีประสิทธิภาพพอที่จะได้รับล่าสุดเมื่อ และเลี้ยงลูกด้วยนมหลายแน่นอนมีเหยื่อของพวกเขาแต่หนึ่งของการก่อการร้ายนก paleontologists ทราบได้ถูกขุดพบในอเมริกาใต้วันนี้ ชนิดหนึ่ง (Titanis walleri) จัดการถึงทวีปอเมริกาเหนือ และเหมือนจะได้รับค่อนข้างประสบความสำเร็จ รอดมากกว่าสามล้านปีจนกว่าจะหายประมาณ 1.8 ล้านปี – สุดท้ายของชนิดของการกลายเป็นสูญ แม้สายพันธุ์อเมริกันนี้ไม่ร้ายนกที่ใหญ่ที่สุด จะต้องยังคงได้สัตว์น่ากลัว สถิติที่สำคัญน่าประทับใจ: 1.4-2.5 เมตรความสูงและน้ำหนัก 150kg นอกจากนี้ยังมีตั๋วเวิ้งว้าง ติดยาเสพติด และ ด้วยเช่นมีจะงอยปากประทับใจ นั้นอาจมีอาจกลืนกินสัตว์แกะขนาดดวดAlthough we can piece together the skeletons of the terror birds it’s impossible to know what their plumage was like. However, we can look at living birds for clues, and if the other flightless birds are anything to go by, the terror bird’s feathers may have been rather hair-like. Like the vast majority of flightless birds, terror birds had stubby little wings, but what they lacked in the wing department they more than made up for with their long, powerful legs that ended in large feet and long claws. These legs gave these animals a good turn of speed and it has been estimated that some species of terror bird could reach speeds of 100kmh – comparable to a cheetah. The combination of running, big talons and a monstrous beak made the terror birds very effective predators. It is possible to imagine one of these birds snapping at the hooves of ancient mammals as it pursued them across the grasslands of the Americas. Smaller animals were probably immobilized with the sharp talons before being torn apart by the fearsome hooked bill or even swallowed whole after having their skull crushed in the bird’s vice-like grip. Larger prey animals may have been disemboweled with Kung-Fu styles kicks and it is even possible that crushing kicks may have been used to crack the larger bones of big prey to get at the nutritious marrow within.Titanis spp. skullSkull of a terror bird (Titanis walleri). This is about 50cm long (Ross Piper)Even if the last terror bird became extinct around 1.8 million years ago, these were successful animals that, as a group, survived for more than 50 million years, some of them even taking on the mantle of top land predator in the ecosystems in which they lived. However, around 2.5 million years ago (during the Pliocene epoch) something happened that completely changed the course of life for South America’s unique animals – the Great American Interchange. The land bridge that eventually appeared between North and South America, what is now known as the Isthmus of Panama, allowed animals from the north to migrate into South America. Among them were lots of predatory cats and it has been proposed these animals were so effective as predators that they outcompeted the terror birds. The talons and beaks of the terror birds were no match for the teeth, claws, and hunting prowess of the invaders from the north. This is a very neat answer for the cause of the extinction of the terror birds, but, the extinction of successful animals is very rarely due to one factor, but a combination of events. Perhaps climate change directly affected the terror birds by changing their habitats and the populations of their prey. Although there is a great deal we don’t know about the life and times of the terror birds we do know that one of their number somehow managed to cross into North America and spread through the southern states. For a long time it was assumed that the American terror bird spread north via the land bridge, but analysis of its ancient bones paints an alternative picture as they appear to have reached the southern states of America before the land bridge formed. Perhaps falling sea levels, due to the growth of the polar ice sheets, revealed a path of ‘stepping stones’ across islands in the gap of open ocean in what would become the Isthmus of Panama, allowing the giant birds to colonize the prehistoric North America. Maybe other species of terror bird, the remains of which are as yet undiscovered, also reached North America before following the rest of their amazing kind into the pages of earth history.
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