Tyrannosaurid (or Tyrannosauridae) is a family of large theropod dinosaurs. It contains the Rockstar species the Tyrannosaurus rex, and its relatives. Tyrannosaurids are commonly classified into two subfamilies: the Albertosaurinae and the Tyrannosaurinae. Albertosaurines are characterized by
more slender builds lower skulls and proportionately longer leg bones than the tyrannosaurines. The Tyrannosaurids are well-studied. Multiple very complete remains have been discovered for most genera and their anatomy is relatively well understood. (Unlike other dinosaur groups) Now, I have to make the distinction clear that this video is about the family Tyrannosauridae, not the superfamily Tyrannosauroidae. They might all be colloquially known as “Tyrannosaur” but formally, Tyrannosauridae (or tyrannosaurids) is a specific classification within the group. And in this video, I’ll present every Tyrannosaurid ever described including possible synonyms and dubious names sorted based on
their estimated size from the smallest to the largest. 1. Raptorex the exact identity of
Raptorex is unclear the specimen comes from a juvenile individual estimated to be only 3 years old
when it died. Raptorex is only known from a
single specimen with unclear origin. The exact stratigraphic position
and age is unknown because it was smuggled out of China
by a fossil dealer. The specimen
likely originated from Mongolia from the Nemegt formation the same site where Tarbosaurus
was found. Raptorex exhibited similar proportions to juvenile tyrannosaurids particularly Tarbosaurus suggesting it may belong to the same genus in its juvenile stage. But in an analysis
in 2022 Raptorex was suggested to be a valid genus closely related to Tarbosaurus
and Tyrannosaurus. The validity of this genus remains disputed. 2. Nanotyrannus (Okay, this is a controversial one again) the holotype Nanotyrannus specimen discovered in the Hell Creek formation
in Montana was first described as a new species
of Gorgosaurus in 1946. Then, in 1988 the specimen was re-described as a new genus “Nanotyrannus”. Eleven years later, the specimen
was re-examined and was revealed to be a juvenile that might belong to Tyrannosaurus rex. During this period many juvenile tyrannosaurids were being classified as distinct species. But after the growth history of tyrannosaurids are better understood that they underwent significant
ontogenetic changes from agile to robust hunters as they age especially in Tyrannosaurus rex that experienced a dramatic growth spurt. Researchers began more accurately assigning smaller tyrannosaurid specimens as the juvenile forms of established taxa. But this was not the case for Nanotyrannus. In 2001, a more complete specimen of a juvenile tyrannosaurus was unearthed. This discovery allowed comparisons with the holotype Nanotyrannus
specimen to be made. many experts concluded that
Nanotyrannus was, in fact, a juvenile Tyrannosaurus. However, a handful of follow-up studies continued to be made on this matter both proving and disproving
the validity of Nanotyrannus. The skull of Nanotyrannus
has been found to match the growth series of Tyrannosaurus rex transitioning from its juvenile
to mature form. The alleged autapomorphic differences observed in the Nanotyrannus specimen might have been the results of individual
or ontogenetic variation or taphonomic distortion. By common consensus, we can consider Nanotyrannus invalid and close the case. But, earlier this year,
a new study was published suggesting that Nanotyrannus is valid and was found to be quite
distantly related to Tyrannosaurus. Some palaeontologists have raised
concerns about this claim. But I’ll leave it here,
we still have many genera to cover. 3. Aublysodon was first described based only
on a tooth fossil in 1868. Many names have been attributed
under this genus over the years, most of which were based
on similar tooth fossils teeth that now have been assigned to juvenile tyrannosaurids such as Daspletosaurus, Gorgosaurus, Tarbosaurus and Tyrannosaurus. The validity of this name is disputed
and is no longer commonly used. 4. Deinodon is no longer considered a valid taxon. It was described based
only on a set of teeth. Like Aublysodon, these teeth probably belonged to Gorgosaurus or other juvenile tyrannosaurids. Over the years, many specimens have been named under the genus Deinodon but they all now have been reclassified, synonymised, or considered nomina dubia. 5. Alioramus is a genus of slender,
and relatively small-sized Tyrannosaurid. The genus contains 2 species, both discovered in the Nemegt Formation
in Mongolia. Alioramus’ anatomy somewhat resembles those of young Tyrannosaurines and although both known specimens come from juvenile individuals we know that adult Alioramus did not grow to the proportions of larger Tyrannosaurids. Alioramus likely occupied a different niche and hunted smaller, faster moving prey separating them in resource requirements with the larger contemporaneous Tyrannosaurid, Tarbosaurus. Alioramus also coexisted with
other theropods pachycephalosauria, hadrosaurids like Saurolophus, and many other dinosaurs. 6. Nanuqsaurus Remains of Nanuqsaurus were discovered
in the Prince Creek formation in northern Alaska. Due to the incomplete nature of the Nanuqsaurus specimen, size estimates vary. From a diminutive 5-6 metres to comparable to other tyrannosaurids, at 8-9 metres. Nanuqsaurus was unique,
in that it lived in polar regions and had to endure
extreme climate conditions. With temperatures estimated to reach subzero during the winter months and 4 months of continuous
low-light conditions. Nanuqsaurus has been speculated to be covered in insulating feathers to survive the cold although the integumentary covering of tyrannosaurids in general is still highly debated. 7. Lythronax Meaning “gore king” is by far the edgiest dinosaur name
I’ve ever heard. It is a relatively small tyrannosaurid with a short snout and broad skull (the width over 40% of the length). This broad skull gave Lythronax forward facing eyes that enabled depth perception. Lythronax is only known
from a partial skeleton discovered in the Wahweap Formation
in Utah. It lived around 81.5 million years ago making it the oldest tyrannosaurid discovered so far. 8. Qianzhousaurus is a medium-sized slender tyrannosaurid closely related to Alioramus. Both genera are grouped
within the tribe Alioramini. They remained as agile, fast moving predators throughout their lives. The skull structure of Qianzhousaurus and other Alioramins indicated that
they have weaker bite force thus primarily hunting small,
particularly fast prey. This unique physiology allowed for
a niche differentiation from other larger tyrannosaurids. Qianzhousaurus was discovered
in the Nanxiong formation, China. This site is known for its abundant oviraptorosaurs and other dinosaur species. 9. Teratophoneus is a genus of tyrannosaurid
dinosaur from Utah in the Kaiparowits Formation. It was described based on several partial and fragmented specimens. In 2021, fossils belonging to four or five individuals were described to be
the remains of Teratophoneus. This fossil indicates a possibility for gregarious behaviour as the individuals seem to have died at relatively the same time. Most likely killed together
by a flooding event. 10. Thanatotheristes is a genus of tyrannosaurid
from Alberta, Canada. It means “reaper of death”
or literally “death reapers”. Sounds like the name of a metal band made by highschoolers, but okay. It was described in 2020
from an incomplete specimen. Thanatotheristes has been suggested to be closely related to Daspletosaurus and thus similar in morphology,
but of smaller size. 11. Albertosaurus was named based on the Canadian province Alberta in which its fossils were discovered. Albertosaurus is known
from more than 30 specimens of all ages the youngest being a two-year-old juvenile measuring around 2 metres and the oldest being a twenty eight-year-old, 10-metre-long specimen. They were discovered at the same site. In fact, the Dry Island bonebed contained 26 Albertosaurus specimens
of different sizes that died at the same time. This might indicate pack behaviour but the theory is contested as the aggregation of dinosaurs’ dead bodies might have been the results of
natural processes like flooding. Albertosaurus is classified into
the subfamily Albertosaurinae that had a more slender build, a smaller head and longer hindlimbs compared to
other tyrannosaurids. Based on fossilised skin impressions, Albertosaurus is known to have scales instead of feathers. Albertosaurus lived alongside other dinosaurs such as hadrosaurids, ankylosaurians, and other theropods, as well as other animals
like crocodilians and turtles. 12. Gorgosaurus was first described in 1914
from a nearly complete skeleton. Over the years, other near complete skeletons were discovered. To date, dozens of Gorgosaurus
specimens of varying sizes have been excavated from
the Dinosaur Park formation. Making Gorgosaurus one of
the best-represented Tyrannosaurids in the fossil record. Gorgosaurus is very similar to Albertosaurus they’re the only known members of
the subfamily Albertosaurinae. By examining the growth curve of tyrannosaurids we can see that Gorgosaurus
also changed from agile juveniles to robust adults roughly
in the middle of its life. Fossil evidence indicated that juvenile Gorgosaurus relied on speed and agility to hunt much smaller prey
and was a solitary hunter. The ontogenetic changes
led to a dietary shift that allowed Gorgosaurus to hunt larger prey at the later half of its life. Gorgosaurus remains
have never been found in groups showing no sign of gregariousness except for a specimen
with facial bite injuries that might have been inflicted
by a different species anyway. Gorgosaurus lived in a subtropical climate with diverse fauna including many other dinosaurs. It coexisted with a rarer species of tyrannosaurid, Daspletosaurus. The evidence of niche differentiation
is unclear it might have been geographical. 13. Dynamoterror was described in 2018
based on a partial and fragmented skeleton. The validity of the taxon
has been put to question since it was described from
very limited remains. A more complete specimen of dynamoterror has been identified in 2021 but it has not been described in detail. 14. Bistahieversor This genus was described in 2010 based on specimens discovered
in the 90s and in 2000. The specimens were initially assigned to the now defunct genus “Aublysodon'' before they were re-examined
and finally given a new name “Bistahieversor”. The classification of this genus is not clear Bistahieversor was initially described as a eutyrannosaurian tyrannosauroid but later it was considered a tyrannosaurine. This discrepancy in classification still persists in other newer related papers. 15. Daspletosaurus The genus Daspletosaurus
contains three species and additional materials
have been discovered that have been assigned to this genus but not to the species level. Some specimens assigned to other genera such as “Bistahievestor” and “Thanatotheristes” have also been suggested to represent separate species of Daspletosaurus. Daspletosaurus had a massive,
heavily-constructed skull with fused bones to improve strength. Like other tyrannosaurids, Daspletosaurus’ skull had large fenestrae
or openings to reduce weight. The teeth were long and thick. It had a muscular body with
a long, heavy tail for balance. Its forelimbs, despite being tiny, are the longest in proportion
amongst other tyrannosaurids. Potential for social behaviours has been observed in Daspletosaurus bite marks present in the skull could’ve been inflicted by another Daspletosaurus. Remains of several individuals
of different sizes buried together have been found in Daspletosaurus. But evidence of cooperative
pack hunting behaviour is uncertain and it has been found to be cannibalistic. Daspletosaurus would’ve been
the apex predator in its ecosystem although it coexisted with the similarly sized but more lightly built
and more common Gorgosaurus there is some evidence of niche differentiation between the two but is not apparent. Daspletosaurus lived in a diverse
ecosystem of vast floodplains along the western shore
of the interior seaway. The Two Medicine and
Judith River formations have yielded incredible diversity
of vertebrate fossils thanks to a combination of natural phenomena ideal for fossilisation. 16. Zhuchengtyrannus was a large tyrannosaurid found in China. Materials of Zhuchengtyrannus
were discovered in 2010. The specimen consists of
partial skull remains. Zhuchengtyrannus, Tarbosaurus, and Tyrannosaurus are closely-related they form a tribe called the tyrannosaurini. Based on the close relationship
of these genera, it is indicative that the North American Tyrannosaurus was an immigrant from Asia although tyrannosaurid geographical dispersal is still unclear. 17. Tarbosaurus was a large tyrannosaurid from Asia. Tarbosaurus anatomy is well-understood, thanks to more than 30
discovered specimens including several quite complete skeletons. It had a big head, long muscular legs
and a heavy tail for counter balance. Tarbosaurus had the smallest arms proportionally among other tyrannosaurids. Most Tarbosaurus specimens were found from the Nemegt formation in Mongolia. But just like other dinosaur fossils
from the region Tarbosaurus fossils have been stolen
and smuggled out to be sold in private auctions for lucrative prices. But fortunately, after a court case the stolen fossils have been
returned to Mongolia. Tarbosaurus is closely related to Tyrannosaurus from North America but Tarbosaurus had more teeth
and a narrower skull. Analysis of Tarbosaurus’ brain case
revealed a keen sense of smell and hearing, but relatively poor eyesight. Evidence of both scavenging and active predation has been observed. Tarbosaurus was the largest predator
in the area and would have hunted large dinosaurs
such as titanosaurs and hadrosaurs. It had a bone-crushing bite force,
and the skull was more rigid possibly an adaptation for hunting
the massive titanosaurid sauropods that inhabited the same ecosystem. 18. Tyrannosaurus is the largest tyrannosaurid and
the most massive predator to have ever walked the earth. The type species, tyrannosaurus rex
is the most popular dinosaur and is an icon in pop-culture. It is the only dinosaur to be popularly known with its specific name included. Currently, there are 2 valid species
within this genus: Tyrannosaurus rex and the newly-named Tyrannosaurus mcraeensis. However, throughout the years, numerous species of Tyrannosaurus
have been named with most considered dubious or synonymous with Tyrannosaurus rex. Tyrannosaurus fossils were abundant, and some nearly complete skeletons
of various ages have been found. This enabled significant research
into its biology making it the most well-studied dinosaur. Histological analysis showed that Tyrannosaurus might have lived up to 28 years and underwent a dramatic growth curve experiencing a sudden growth spurt
in the middle of their lives. Changing from agile, slender juveniles… to robust, heavy-weight adults
in just 4 years. At their peak, it has been estimated that they gained on average 600 kilos of body weight every year. This growth rate also indicates
that Tyrannosaurus, and by extension, dinosaurs in general, are endothermic or warm-blooded animals. Various evidence of active predation in Tyrannosaurus has been documented such as healed wound marks
in triceratops and edmontosaurus inflicted by Tyrannosaurus. Tyrannosaurus has been calculated to possess the most powerful bite force of any terrestrial animal capable of crushing bones. They might have employed both
active predation and scavenging as their feeding strategy. Tyrannosaurus was also cannibalistic,
at least in a scavenging capacity. Evidence gathered from
various specimens suggests opportunistic feeding behaviour
in tyrannosaurids that cannibalised members
of their own species. Tyrannosaurus is estimated to
have had a large population size spanning from the North to South Laramidia occupying the role of apex predator
in many different ecosystems. In the Hell Creek formation, Tyrannosaurus coexisted with
many other iconic dinosaurs such as triceratops, ankylosaurus, pachycephalosaurus, and the giant edmontosaurus. Tyrannosaurus rex lived until
the end of the Cretaceous marked by the K-Pg extinction event that ended the reign of all non-avian dinosaurs. Now, before we go into
the size comparison, There are still some obscure
invalid tyrannosaurid genera. Many of them are misnomers. Most, if not all, of the specimens
attributed to these names have been reassigned
to other tyrannosaurid genera. And those are all of the Tyrannosaurid genera that have been formally described to date. The relative abundance of
tyrannosaurid fossils has allowed us to reveal the spectacular nature of these ancient beasts. They evolved and diversified
in the late Cretaceous and quickly filled the niche of apex predators that has been left out by the preceding, more ancient carnosaurs. Tyrannosaurids are notable for
their large size, robust skulls, bipedal stance on long, muscular hindlimbs, and disproportionately small,
two-fingered arms. Tyrannosaurids are iconic
and it’s easy to see why. Many of them were apex predators
in their ecosystems and their dominance over their environment was absolute. Tyrannosaurids evolved into some
of the most powerful and most recognizable terrestrial predators to have ever lived.
