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The end Cretaceous extinction event did not kill the dinosaurs - well, not all of them. Of course, in the Cenozoic that followed, one group of dinosaurs - the birds - would become very successful, and over ten thousand species have survived into the modern day.
Over the course of the Cenozoic, however, some birds were particularly more dinosaur-like than others, acting as enormous apex predators, scavengers, and ecosystem engineers.
In today's video, we'll be exploring five particularly dinosaurian birds that would not have looked out of place in the Mesozoic.
Written, Researched & Presented by: Thomas McGlynn
Thanks for watching.
DISCLAIMER: All materials in these videos are used for entertainment purposes and fall within the guidelines of fair use. No copyright infringement is intended. If you are, or represent the copyright owner of materials used in this video, and have an issue with the use of said material, PLEASE email us before putting in a claim and we can resolve the issue immediately. We can be reach on this email: info@top5s.co.uk
Copyright © 2026 Top5s All rights reserved.
Over the course of the Cenozoic, however, some birds were particularly more dinosaur-like than others, acting as enormous apex predators, scavengers, and ecosystem engineers.
In today's video, we'll be exploring five particularly dinosaurian birds that would not have looked out of place in the Mesozoic.
Written, Researched & Presented by: Thomas McGlynn
Thanks for watching.
DISCLAIMER: All materials in these videos are used for entertainment purposes and fall within the guidelines of fair use. No copyright infringement is intended. If you are, or represent the copyright owner of materials used in this video, and have an issue with the use of said material, PLEASE email us before putting in a claim and we can resolve the issue immediately. We can be reach on this email: info@top5s.co.uk
Copyright © 2026 Top5s All rights reserved.
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TechTranscript
00:00The end-Cretaceous extinction event did not kill the dinosaurs.
00:04Well, not all of them.
00:06Of course, in the Cenozoic that followed, one group of dinosaurs, the birds, would become very successful,
00:12and over 10,000 species have survived into the modern day.
00:15Over the course of the Cenozoic, however, some birds were particularly more dinosaur-like than others,
00:20acting as enormous apex predators, scavengers, and ecosystem engineers.
00:25In today's video, we'll be exploring five particularly dinosaurian birds of the Cenozoic
00:30that probably wouldn't have looked too out of place in the Metazoic.
00:52Let's kick things off with one of the most dangerous birds that has ever walked the planet.
00:56Devon Senzia belonged to a group of avian dinosaurs known as the Terror Birds
01:01within the family Forrest Rachidae,
01:03which stood as the final terrestrial avian apex predators
01:05in a world that was otherwise ruled by the carnivore and mammals.
01:09One particularly large Devon Senzia individual,
01:13discovered in the early Pleistocene Rhygon formation of Uruguay,
01:16is estimated to have weighed up to 350 kilograms in life,
01:20standing roughly two and a half meters tall.
01:23Of course, at this size, there was no way Devon Senzia,
01:27or any of its closest relatives, could ever take to the skies,
01:30and they instead evolved to chase down mammalian prey
01:32across the tall pampas grasslands of ancient South America.
01:36Devon Senzia was able to evolve in the first place
01:39thanks to a notable absence of large mammalian predators in South America
01:43during the Cenozoic,
01:44bar their coexistence with several genera of Spiracodont mammals,
01:48similar to marsupials.
01:50Devon Senzia's skull, which measured up to 65 centimeters in total,
01:54was robust and powerful,
01:55with much of it being composed of a thick, hooked beak.
01:58When hunting, Devon Senzia would have used its long neck
02:02in tandem with this impressive weaponry,
02:04snatching up smaller animals from the long grasses
02:06and chasing down larger, bulkier prey when the opportunity arose.
02:11Devon Senzia's closest relatives,
02:13the much more famous terror birds,
02:14Forrest Rarkus, Titanus, and Kalenkan,
02:17were amongst the largest and most successful members of their family,
02:20and are thought to have been capable of hunting and dispatching animals
02:23as sizable as the larger notoungulates and litoptans
02:26that were endemic to South America during the end of the Cenozoic.
02:302.7 million years ago, however,
02:32North and South America became connected
02:34when the volcanic isthmus of Panama rose up from the seafloor,
02:38establishing a land bridge between the two continents.
02:41In what would become known as the Great American Biotic Interchange,
02:45animal groups that were previously absent from the North
02:47were able to travel downwards into the South and vice versa.
02:51Although Devon Senzia may have been extinct by this point,
02:54the interchange would spell doom for every remaining species of terror bird
02:58as giant mammalian carnivores,
03:00who were more robust and adaptable than the birds,
03:03trickled down into their domain,
03:04out-competing them to the grave.
03:06The main offenders here are believed to have been
03:08the large sabertooth cats such as Smilodon,
03:11who hunted the same prey items as the terror birds,
03:13but with a greater degree of efficiency.
03:21We're staying in South America for this next entry
03:24as we meet the heaviest flying bird that has ever lived.
03:28Argentavis, sometimes known casually as the Giant Teratorn,
03:31was a member of the family Teratornithidae,
03:34a group of often enormous, vulture-like birds of prey
03:37that were adapted to scavenging on the remains
03:39of the huge megafauna of the Cenozoic.
03:41In larger individuals, Argentavis' wingspan
03:45may have been capable of reaching up to 6 metres across,
03:48such birds would have weighed as much as 72 kilograms.
03:52For reference, the heaviest flying bird alive today,
03:55the Kori Bustard of the African grasslands,
03:57only weighs up to 19 kilograms in extreme cases.
04:01Argentavis lived in what would eventually become
04:03central and northwestern Argentina
04:05between 9 and 7 million years ago
04:07in the late Miocene epoch.
04:09Due to the immense wing size,
04:11this colossal Teratorn may not have been able to take off
04:14from a standing start,
04:15and instead would need to use mountain slopes
04:17and high winds as leverage,
04:19leaping into the ether to scan the land far below for carrion.
04:23It's believed that a bird as large as Argentavis
04:25may have had a territory as huge as 500 square kilometres,
04:29and could have ousted threats from its territory
04:31by fanning out its massive wings on the ground,
04:33perhaps even bullying predators away from their kills in the process.
04:37Argentavis actually coexisted at the same time
04:40and in the same place with Devincenzia,
04:42and the two may have come into frequent conflict
04:44over food and territory.
04:46Scientists have theorised much about the way Argentavis lived
04:49by looking at existing birds who fill similar ecological niches,
04:53such as the Andean and California condors of today's Americas.
04:56If their habits and biology were as similar as their lifestyles,
05:00then Argentavis may have laid one or two huge eggs
05:03across a two-year period,
05:04incubating them during the winter,
05:06whilst the mated pair shared chick-rearing duties.
05:09Young Argentavis may have taken their first frightening leap
05:12into the mountain gales at around 16 months of age,
05:15but may not have become fully mature until 12 years of age.
05:24The island of Madagascar has always been something of an ecological anomaly.
05:29Isolated in the Indian Ocean,
05:31so close yet so far to Africa's eastern coastline,
05:34this land is full of animals
05:35who have been able to evolve cut off from the rest of the world.
05:39Endemic lemurs, fossa, mongoose-like carnivores,
05:42and all manner of small creatures call Madagascar home,
05:44but in the past, the island's ecosystems were filled with all manner of megafaunal oddities,
05:49among them, some of the largest avian dinosaurs ever to walk the earth.
05:54Apiornis maximus, often nicknamed the giant elephant bird,
05:58may just be the largest bird ever to have evolved,
06:00reaching three meters in height
06:02and weighing in at up to 1,000 kilograms in the case of large adults.
06:06In life, it would have looked much like an enormous emu,
06:09with a winding serpentine neck,
06:11a bulky body, two pillar-like legs,
06:13and a straight conical beak,
06:15feeding primarily on fruits, grasses and seeds
06:17across the forests and plains it called home.
06:20While the two might look drastically dissimilar,
06:23Apiornis' closest living relatives are the Kiwis of New Zealand,
06:26and like them, it may have been nocturnal,
06:29with females growing larger than the males.
06:31Amazingly, Apiornis survived late enough into the Cenozoic
06:34that it certainly encountered,
06:35and may even have been driven to extinction by,
06:38the earliest human settlers to arrive on Madagascar.
06:41While humans are believed to have hunted adult elephant birds
06:44as they quickly made their way across the island,
06:46it was Apiornis' eggs that proved the most valuable,
06:49with the remains of many
06:50having been discovered close to ancient campfires.
06:52A legendary bird from Malagasy folklore,
06:55the Varumpatch,
06:56may actually be the elephant bird itself,
06:58as stories of its existence were passed down
07:00via the oral tradition around ancient Madagascan campfires.
07:10Another contender for the heaviest and tallest bird of all time
07:13can be found in ancient Australia.
07:16Dromornis stertanii,
07:17whose adult males reach sizes of up to 3 metres tall,
07:20and weights in excess of 500 kilograms,
07:23lived in the late Miocene Epoch,
07:25between 8 and 15 million years ago.
07:27Known colloquially as thunderbirds,
07:29the Dromornithids resembled bulkier renditions of ostriches,
07:33but were in fact most closely related to the ducks and geese of the modern day.
07:36The remains of this avian giant were discovered in 1979
07:40in the Alcuta fossil beds of Australia's Northern Territory,
07:44which to this date have provided the only certain occurrence of the bird in the fossil record.
07:48Based on analysis of the Alcuta site,
07:51Dromornis may have favoured semi-arid open woodlands
07:54with seasonal rainfalls and lakes in which it could locate food.
07:57While it was herbivorous using its blunt beak
08:00to feed on a variety of seeds, fruits, leaves and freshwater plants,
08:04some paleontologists have suggested that it might have been a particularly aggressive species,
08:08violently defending its territory from marsupials
08:11and other birds which may have intended on stealing its eggs.
08:14As the largest animal known from its environment,
08:17adult Dromornis stertini would have faced little to no competition from predators,
08:21whereas youngsters may have faced threats from the wolf-like thylacine species of the time,
08:25as well as the medium-sized cat-like ambush predator, Wacaleo.
08:29Dromornis may have been ousted from its position at the forefront of its ecosystem
08:33by the emergence of other large birds,
08:35likely subsequent species of Dromornithids,
08:38as the Cenozoic pressed on.
08:40With less food available due to competition from other species
08:43and a slow reproductive rate due to their immense size,
08:46Dromornis sadly may not have been able to keep up with the rapidly changing conditions
08:50and disappeared into the fossil record forever.
08:58While we might see modern penguins as cute and cuddly,
09:01this prehistoric penguin was a little different.
09:04Kumimanu Baisie, an early genus of penguin from around 56 to 60 million years ago,
09:10was almost tall enough to look a fully grown human in the eye
09:12and hunted with a sharp harpoon-like beak.
09:15Its fossils were discovered in what is today New Zealand,
09:18and this species was quick to emerge after the extinction of the non-avian dinosaurs,
09:23growing large off the abundance of fish in the warmer waters of the early Cenozoic.
09:27It should come as no surprise then, that in the Maori language,
09:30Kumimanu translates to monster bird,
09:33and adults of this species would have measured just under 2 metres in height,
09:36weighing in at just over 100 kilograms.
09:39Kumimanu would have hunted in the shallow seas surrounding New Zealand in the Paleocene epoch,
09:43where it darted gracefully under the water after large fish and cephalopods.
09:47Its powerful flipper-like wings would have allowed it to effortlessly push itself through the waves,
09:52whereas on land, like modern penguins, it would have been clumsy and ungainly.
09:56With no large marine reptiles in the wake of the end-Cretaceous extinction,
10:00and before the time of the whales and dolphins,
10:03Kumimanu's only adversary would have been the occasional shark,
10:06which, depending on the species, it may have been able to out-swim or even overpower.
10:11Kumimanu was not the only giant penguin thriving in the early stages of the Cenozoic,
10:15and this group were particularly fast to evolve many large, powerful predators.
10:19Paleoediptes, for one, was a successful genus of giant penguins,
10:23which managed to last until the Oligocene epoch,
10:25whose four species masterfully hunted large fish around the waters of Oceania and South America.
10:31Another genus, Anthropornis, may have been amongst the largest seabirds to ever live,
10:35closely resembling the emperor penguin of today as it shot through the waters of Antarctica like a living torpedo.
10:46The age of the dinosaurs then did not end with the Chixscalub impact.
10:51All across the world, Cenozoic dinosaurs were continuing to make the mark on the land around them,
10:56spreading out into all manner of ecological niches and across every environment on the planet.
11:01Today, avian dinosaurs are some of the most successful vertebrates in the world,
11:05thriving in wetlands, rainforests, mountains, grasslands and even the frozen poles.
11:10Who knows what the future could have in store for the dinosaurs then?
11:14Thank you so much for watching to the end of today's video, we really appreciate it.
11:19Let us know in the comments what your favourite Cenozoic avian dinosaur was.
11:22Don't forget to like, hype and subscribe to Dinosaur Discovery and we'll see you next time.