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Before the dinosaurs arrived on the scene, the world was a very strange place indeed. Much of the Triassic Period was something of a trial and error period for the forces of evolution, as all manner of new reptile groups took over in the wake of the End Permian Extinction. This, then, was a world filled with giant, alien predators across the seas and land, like nothing else the world had seen at that point - and today, we'll be bringing you face to face with them.
From a marine giant that dispatched its prey with immense jaws, to a crocodile relative bigger than some predatory dinosaurs, these are the terrors of the Triassic.
Written, Researched & Presented by: Thomas McGlynn
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From a marine giant that dispatched its prey with immense jaws, to a crocodile relative bigger than some predatory dinosaurs, these are the terrors of the Triassic.
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.
Category
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AnimalsTranscript
00:00Before the dinosaurs evolved, the world was a very strange place indeed.
00:04Much of the Triassic period was something of a trial and error period for the forces of evolution
00:09and all manner of new reptile groups took over in the wake of the end Permian extinction.
00:14This then was a world filled with giant alien predators across the seas and land
00:19like nothing else the world had seen at that point,
00:21and today we'll be bringing you face to face with them.
00:24From a marine giant that dispatched prey with immense jaws
00:27to a crocodile relative bigger than some predatory dinosaurs,
00:31these are the true terrors of the Triassic period.
00:52Before the dinosaurs evolved to rule their respective environments,
00:56much of the world was ruled by a group called the Rauasuchians.
01:00These often enormous, predatory reptiles are related to modern-day crocodiles,
01:05and while the name of the group is informal and unofficial in the taxonomic sense,
01:09it's still widely used to group together several large Triassic-age Pseudasuchians.
01:13While many Rauasuchians were indeed very large,
01:17none were larger than Fosolosuchus tenax,
01:19a species native to the Los Colorados formation of northwestern Argentina
01:23around 220 million years ago.
01:26Growing to lengths of 8 to 10 meters when fully grown,
01:30Fosolosuchus has earned the title of the largest known
01:32non-dinosaurian terrestrial apex predator.
01:36Fosolosuchus looked much like a laterally flattened crocodile,
01:39with longer legs and a stiff tail,
01:40that allowed it to lead a life away from the water's edge.
01:43The jaws were of course the most impressive feature of this animal,
01:47and were filled with enormous recurved, razor-sharp teeth,
01:49which were used for manipulating and crushing through the bodies of the reptiles and synapsids
01:53that shared its environment.
01:55Unlike others of its kind,
01:57Fosolosuchus possessed one large row of tough, bony osteoderms
02:01that ran along the animal's back,
02:02likely protecting it from the jaws of members of the same species.
02:06Fosolosuchus actually co-existed with some of the first dinosaurs,
02:09and given its size, stature and dental weaponry,
02:12we can assume that it most likely hunted and fed upon them too.
02:15It co-existed with Riocasaurus,
02:18a 10-metre-long prosauropod dinosaur
02:20that could have weighed up to 3,000 kilograms when fully grown.
02:24Fosolosuchus most likely utilised its giant teeth
02:26to slash into the neck and flanks of young or weak Riocasaurus,
02:30sustaining itself on a huge quantity of meat for a considerable period of time.
02:40One of the most well-documented and widespread marine predators of the Triassic period
02:44was the giant ichthyosaur Cimbospondylus.
02:47C. yungorum,
02:48the largest species within the genus
02:50and one of the largest ichthyosaurs known to science at this point in time,
02:54was capable of growing to lengths in excess of 17 metres when fully grown.
02:58That's roughly the same size as a fully grown sperm whale,
03:00a large mosasaurus and the same size as some sauropods.
03:05Cimbospondylus sat within the Cimbospondylidae family of ichthyosaurs
03:09and as a result drastically differed from those you might be familiar with from the Jurassic period.
03:14It evolved the classic large eyes and long snout that were typical for the ichthyosaurs,
03:18but its body was much longer than the likes of ichthyosaurus and ophthalmosaurus.
03:23Moreover, it may have lacked a dorsal fin altogether,
03:25resembling the sea serpent-esque mosasaurs
03:28that would arise in the late Cretaceous period more than anything else.
03:31Giant ichthyosaurs such as Cimbospondylus
03:34were akin to the whales and dolphins of the modern day
03:36and lived rather similar lives,
03:38feeding upon fish, cephalopods, large bivalves and even marine tetrapods.
03:43Cimbospondylus yungorum in particular
03:45is believed to have been an apex predator of medium to large-sized marine reptiles
03:49such as other ichthyosaurs,
03:51potentially including those belonging to the same species or genus.
03:54The bones belonging to Cimbospondylus yungorum were initially discovered
03:58in Nevada's Augusta Mountains by Paul Martin Sander in 1998,
04:02who eventually unearthed them between 2014 and 2015,
04:06naming the species formally in 2021.
04:09The genus as a whole was much more widespread,
04:11spanning Canada, the western United States,
04:14the Caribbean and southern Europe between 251 to 242 million years ago.
04:20Cimbospondylus yungorum is specifically associated with the Favret formation of Nevada,
04:25where it lived alongside up to three other species of the same genus,
04:28C. Petrinus, C. Nicholseye and C. Dwellferi.
04:32The latter three were much smaller than C. Yungorum, of course,
04:35and may have occasionally fallen victim to the jaws of the immense predator
04:38as it passed through shallow coastal waters in search of food.
04:42Cimbospondylus likely hung close to the surface waters across the oceans in which it lived
04:46due to the high quantities of oxygen in contrast with the deeper waters below,
04:50in which very little could survive due to the toxic conditions.
04:59Nothing on Earth today resembles Arizonasaurus.
05:03It looks like it's something between a dinosaur, a crocodilian,
05:07and a Permian-age synapsid such as Dimetrodon,
05:09and yet it's not really closely related to any of these groups.
05:12It is indeed an archosaur, and a pseudosuchion at that,
05:16which places it closer to crocodiles than the synapsids,
05:18but sits within the clad Poposauroidea, an unusual and highly derived group.
05:24Arizonasaurus babetii, as you might have guessed,
05:26resided in Arizona during the Middle Triassic period,
05:29roughly 243 million years ago, and was named by Samuel Paul Wells in 1947.
05:34The skeleton is rather well known,
05:37and one near-complete specimen on Earth in 2002
05:39has allowed scientists to gain a good understanding
05:42of what this animal looked like in life.
05:44Much like Spinosaurus,
05:46Arizonasaurus boasted an impressive sail atop its back
05:49that was made from elongated neural spines.
05:52This structure, much like the ones
05:53harnessed by the likes of Dimetrodon and Adaphosaurus
05:56before it in the Permian,
05:57may have been used to regulate its body temperature
05:59in the hot, arid environments of ancient Nevada's Moenkopee formation,
06:03but it could also have held a function in mating displays or communication.
06:06Large, fully grown Arizonasaurus specimens
06:09could have attained lengths of 3 metres from nose to tail,
06:12and may have weighed between 70 and 100 kilograms at that size.
06:16They were, of course, carnivores,
06:18with recurved serrated teeth lining their powerful jaws
06:20that would have been used to cut into and slash at prey,
06:23slicing through flesh with terrifying efficiency.
06:26When Arizonasaurus was alive,
06:28the Moenkopee formation was characterised
06:30by a vast, arid coastal floodplain,
06:32and an ecosystem that was still in recovery
06:34following the catastrophic events of the end Permian extinction event.
06:38Arizonasaurus most likely hunted in land,
06:40preying upon the tetrapods attempting to scrape a living
06:43in the hot, dry rocks of ancient Arizona.
06:45Its diet may have consisted of
06:47Temnospondyl amphibians,
06:48Rhynchosaurs,
06:49Dicinodonts,
06:50and Trilophosaurids such as Anisodontosaurus.
07:00Erythrosuchus africanus
07:01Erythrosuchus africanus
07:01boasted one of the most impressive skulls
07:03in all of natural history.
07:05As the largest predator of its time,
07:07growing up to lengths of between 4 and 5 metres
07:09when fully grown,
07:10it was an impressive-looking animal,
07:12but almost a quarter of its body length
07:14was made up by an immense
07:15theropod dinosaur-like head.
07:17In life, its post-cranial body
07:19would have resembled something akin
07:20to a modern-day crocodile, with legs positioned
07:23towards the underside of its body
07:24rather than adopting the sprawling,
07:26lizard-like gait seen in most large reptiles of its time.
07:29Within the immense jaws of Erythrosuchus
07:31sat a series of sharp, conical teeth
07:33that would have been used to pierce the flesh of its prey,
07:35causing puncturing and bleeding damage
07:37to the head, neck, and torso.
07:38This particular species was a resident
07:41of the early Middle Triassic period
07:42of what would eventually become South Africa,
07:45living between 249 to 244 million years ago.
07:49It's been known to science since 1905,
07:52and early reconstructions of Erythrosuchus
07:54show an animal that essentially resembled
07:56a quadrupedal Tyrannosaurus rex,
07:58albeit one with a proportionately enormous head.
08:01It too was an archosauroform,
08:03sitting within the family Erythrosuchidae,
08:05where it was the largest of its kind,
08:06and one of the largest terrestrial apex predators
08:08of the entire Triassic period.
08:11But why did Erythrosuchus boast such a large head,
08:14a head that was in fact proportionately larger
08:16than that of any known reptile alive or extinct?
08:19Well, the skull is thought to have been the anchor point
08:21for immense jaw muscles,
08:22which afforded Erythrosuchus
08:24an exceptionally strong bite force.
08:26It likely hunted large, slow-moving animals
08:28that were tough to bring down,
08:30such as the bulky herbivorous Dicinodonts,
08:32and therefore boasting such an impressive
08:34cranial and muscle structure,
08:36with teeth shaped like steak knives,
08:37would have given it the power it needed
08:39to reliably bring down the toughest herbivores of its day.
08:42Despite the impressive size of the skull,
08:44it was relatively lightweight,
08:45with multiple weight-saving air pockets
08:47known as fenestrae lining the bone.
08:49This, when combined with an exceptionally thick
08:51and powerful neck,
08:52meant that Erythrosuchus had no trouble at all
08:54wielding such a skull as its primary weapon.
09:02With size estimates ranging from 7 to 12 meters in length,
09:07Smilosuchus Gregorii was one of the most impressive
09:09predators of the entire Mesozoic.
09:11It too resembled a crocodile,
09:13more so than any of the other entries in today's video,
09:16but it was in no way related.
09:17It was in fact a phytosaur,
09:19a member of a group of basal archosauriforms
09:21that superficially looked like crocodiles.
09:24Its generic name translates into English as knife crocodile,
09:27and given the shape and size of its teeth,
09:29that's not particularly hard to see why.
09:32This species proudly wielded immense tusk-like teeth
09:34at the front of its mouth
09:35for piercing and gripping prey items,
09:38which were then processed closer to the back of the jaws
09:40with blade-like slicing teeth.
09:42Initially described in 1995
09:44from remains that were once thought to belong
09:46to the closely related Leptosuchus,
09:48Smilosuchus lived in what is today Arizona
09:50between 221 and 205 million years ago.
09:54While three species have been named and described,
09:57Smilosuchus Gregorii is the largest,
09:59possessing a large rostral crest atop its snout,
10:02just above those immense tusk-like teeth.
10:04Its remains have been discovered
10:05in Arizona's Chinle Formation,
10:07a particularly fossil-rich site
10:08containing the remains of large reptiles,
10:10therapsids, and of course, dinosaurs.
10:13Smilosuchus was not the only large predator
10:15present in the Chinle Formation at the time it lived,
10:17and it may have faced competition
10:18from its distant terrestrial relative,
10:20Postosuchus.
10:23Smilosuchus is believed to have lain in wait
10:24in rivers and lakes just at the water's edge,
10:27while herbivores such as Placarias,
10:29the giant Dysynodon,
10:30would come down to drink.
10:31At the very last second,
10:33Smilosuchus would emerge,
10:34jaws agape,
10:35dragging its unlucky victim down to a watery grave.
10:38Also living here were innumerable numbers
10:40of Coelophysis,
10:41a primitive dinosaur that is believed
10:43to have lived in large groups,
10:44as well as Dismatosuchus,
10:46a particularly well-armored herbivore
10:48belonging to a group of archosaurs
10:49known as the Aetosaurs.
10:56The early Mesozoic then
10:57was filled with many terrifying
10:59non-dinosaurian threats,
11:01but today we've only really met a few of them.
11:04In the seas,
11:05enormous ichthyosaurs,
11:06much larger than Simba Spondylus,
11:08were beginning to spread out
11:09and diversify towards the end of the Triassic,
11:11while on land,
11:12the very first carnivorous dinosaurian apex predators
11:14such as the mighty Herrerasaurus
11:16were taken over.
11:17By the end of the Triassic,
11:19the stage was set for the dinosaurs
11:20to become the dominant group of reptiles
11:22across the entire world.
11:24Thank you so much as always
11:25for watching to the end of this video,
11:27we really, really appreciate it.
11:29Let us know in the comments
11:30what your favourite Triassic predator was.
11:32Don't forget to like, hype,
11:33and subscribe to Dinosaur Discovery,
11:35and we'll see you next time.