| Name | Lythronax | Diet | Carnivorous |
| Name Meaning | Gore King | Height | 2.3 meters (7.5 feet) |
| Pronunciation | Lye-thro-nax | Length | 5-8 meters (16.4-26.2 feet) |
| Era | Mesozoic – Late Cretaceous | Weight | 500-2,500 kilograms (1,100-5,511 pounds) |
| Classification | Dinosauria, Saurischia, Theropoda | Location | Utah, Western North America |
Lythronax Pictures
The Lythronax
Imagine a smaller, earlier version of the famous T-Rex, and you’ll envision Lythronax, the oldest member of the tyrannosaurid group!
Lythronax remains were discovered in Utah and served as a turning point in understanding the evolution of tyrannosaurids.
Specialists confirmed that Lythronax exhibited multiple traits known in later tyrannosaurid forms, such as forward-facing eye sockets.
Other unique characteristics of the genus include a broad back of the skull and a relatively short snout.
Like other tyrannosaurids, Lythronax was a bipedal theropod that may have relied on a pursuit or ambushing hunting technique.
Its strong jaws and large teeth, along with its binocular vision, served as excellent aids in catching prey. Lythronax may have also been a scavenger.
Physical Characteristics
Lythronax had a broad skull equipped with a short snout.
Its eye sockets faced forward, similar to the orbits of Tarbosaurus and Tyrannosaurus.
In contrast, earlier forms had less forward-facing eye sockets and narrower skulls.
The teeth of Lythronax were robust, serrated, and quite long, some reaching 13 centimeters (5 inches).
Some studies show that tyrannosaurids had lips that protected the teeth.
Although this hasn’t been confirmed for Lythronax, we cannot rule out the possibility.
The postcranial skeleton of Lythronax remains poorly studied due to a lack of materials.
However, upon discovering fragmentary pubis and hindlimb remains, scientists concluded that Lythronax had a typical tyrannosaurid build.
As such, it was likely heavily built and walked on its robust hindlimbs.
Its neck was probably S-shaped and thick enough to support the broad skull.
The tail was heavy and served as a counterbalance, while the center of the mass was over the hips.
The two-fingered forelimbs were remarkably short.
Lythronax wasn’t the largest tyrannosaurid, but it was undoubtedly an efficient predator.
Scientists initially estimated a length of 7.3–8 meters (24–26.2 feet) for Lythronax.
Others, however, argued that it was much smaller, reaching only 5 meters (16.4 feet) long.
The most recent research provided a value of 6.8 meters (22.3 feet).
The weight hasn’t been fully confirmed.
At first, Lythronax supposedly weighed 2.5 metric tons (2.75 short tons), then the weight was lowered to 500 kilograms (1,100 pounds), which is quite a big difference, isn’t it?
The latest research, which proposed a length of 6.8 meters (22.3 feet), argued in favor of a weight of 1.4 metric tons (1.54 short tons).
The same scientists suggested a hip height of 2.3 meters (7.5 feet).
Compared to other members of the Tyrannosaurinae family, Lythronax was quite small.
Tarbosaurus, for instance, was 10 meters (33 feet) long, weighed 4.5–5 metric tons (5–5.5 short tons), and had a hip weight of 3 meters (9.8 feet).
Tyrannosaurus, another relative of Lythronax and probably the most famous dinosaur of all time, was almost twice as large as Lythronax, reaching 12.3–12.4 meters (40.4–40.7 feet) long.
Nanuqsaurus, on the other hand, was smaller than the T-Rex, probably 8–9 meters (26.2–29.5 feet) long.
The closest to Lythronax in size was Teratophoneus, which likely measured 6-8 meters (19.7–26.2 feet) long.
Habitat and Distribution
Lythronax fossils were discovered in the Wahweap Formation of southern Utah.
During the Late Cretaceous, when Lythronax was alive, the Western Interior Seaway divided the North American continent into two parts – Appalachia and Laramidia.
Modern-day Utah was located on Laramidia, close to the Western Interior Seaway.
Therefore, the territory inhabited by dinosaurs was filled with multiple water bodies like floodplains, lakes, and rivers and featured a wet, seasonal climate.
Behavior and Diet
Lythronax was a bipedal carnivore that fed on local herbivores, most probably hadrosaurs.
Its strong jaws and teeth made for strong bite forces that allowed Lythronax to cut flesh and crush bones.
Scientists suggest that Lythronax probably took significant advantage of the engaging field of view provided by its binocular vision.
Additionally, it had well-developed depth perception.
The same structure of the eye sockets (forward-facing) is known from the famous T-Rex, which is believed to have been both an efficient predator and a scavenger.
Scientists have debated its predatory behavior for years now!
It remains unknown whether Lythronax was a fully active predator or a scavenger.
Since many feeding adaptations were similar to those of a T-Rex, we cannot rule out the possibility that they had similar dietary preferences.
In short, both Lythronax and T-Rex were probably active predators and scavengers; after all, why would they refuse any meal if it appeared their way?
Let’s not forget that both Lythronax and Tyrannosaurus were confirmed to have had a puncture-and-pull feeding technique, so they probably did use this advantage to kill prey!
Besides this, studies on Tyrannosaurus rex showed that, despite not being able to reach great running speeds, it may have been quite agile in pivoting its bodies.
This ensured excellent predation if it hoped for one.
We may assume that these details were also valid for Lythronax since the two were close relatives, although millions of years separated them.
On the other hand, considering that Lythronax was much smaller than the T-Rex, we can also suspect it may have been able to run faster than its successor.
Life Cycle
Lythronax, like all dinosaurs and modern birds, reproduced by laying eggs.
Females laid two eggs at a time.
It has been confirmed that at least some theropods incubated their eggs, so we cannot rule out the possibility that Lythronax engaged in this behavior too.
Paleontologists discovered an embryonic tyrannosaur, which suggested that these creatures got their distinctive characteristics even before hatching.
Scientists estimate that neonate tyrannosaurids likely measured approximately 0.76–0.91 meters (2.5–3 feet) long upon hatching, and their skulls were the size of a mouse.
Since these remains have not been associated with a particular tyrannosaurid genus, these numbers may vary depending on the estimated size of each species.
Studies on tyrannosaurid ontogeny showed that juveniles had narrow feet and toes, which allowed them to run at fast speeds.
As they matured, the feet grew wider.
This may have slowed them down.
It has also been suggested that tyrannosaurids did not grow too fast during their first years of life and then experienced growth spurts that lasted four years.
They likely attained their maximum size at 14 years of age.
It is believed that many tyrannosaurids experienced premature deaths soon after reaching sexual maturity.
Scientists link this to the stress associated with reproduction.
Evolution and History
Lythronax is part of the Tyrannosauridae family, whose members descend from small ancestors.
Tyrannosaurids diversified more than 80 million years ago and evolved into much larger dinosaurs, most of which were apex predators in their habitats.
Further down the taxonomic tree, Lythronax is placed under Tyrannosaurinae, alongside other tyrannosaurs like Tarbosaurus, Zuchengtyrannus, and Tyrannosaurus.
Curiously enough, Lythronax is considered the oldest known tyrannosaurid, and it’s the closest relative of the youngest member of the group, Tyrannosaurus.
After paleontologists unearthed the remains of Lythronax, they realized they had stumbled upon something that would lead to breakthrough discoveries.
These fossils were proof that the evolutionary radiation of tyrannosaurids occurred much earlier than previously thought.
Upon studying the remains, paleontologists also concluded that multiple traits observed in the youngest tyrannosaurids (including T-Rex), like the feeding apparatus, stemmed from Lythronax.
Additionally, specialists argue that the discovery of Lythronax indicates there may be multiple other tyrannosaurid forms yet unknown to us.
Lythronax prompted scientists to continue studying tyrannosaurids’ diversification and geographical distribution.
As such, studies have shown that the members of the Tyrannosauridae group reached the peak of their diversification after Laramidia had been completely isolated.
The high sea levels led to the division of Laramidia into several areas of land, which further isolated various tyrannosaurids and supported their diversification.
This explains why southern tyrannosaurids, including Lythronax, were so different from the northern forms.
Once the sea levels dropped, tyrannosaurids likely dispersed into Asia.
That’s how scientists explain the link between Asian tyrannosaurids and North American forms like Lythronax.
Since we’ve mentioned the first discovery of Lythronax, why don’t we return to when it happened?
We would arrive in 2009, which isn’t that long ago! Now it’s clear why this paleontological event aroused the interest of so many scientists, considering that the tyrannosaurid evolutionary tree had looked much different for so many years!
In 2009, a paleontological expedition revealed a theropod nasal bone and leg in Utah’s Wahweap Formation.
Before this discovery, no theropod fossils had been unearthed on this territory, so the scientists from the University of Utah were quite skeptical about them.
But it turned out that the nasal bone had indeed belonged to a tyrannosaur, one much older than the others known to paleontology!
Before formally naming and describing the tyrannosaur, scientists called it the Nipple Butte Tyrannosaur.
In 2013, the fossils were attributed to a tyrannosaur called Lythronax argestes.
The name comes from the Greek words for gore and king.
The king part is a reference to the T-Rex, while the gore part indicates Lythronax‘s predatory nature.
Interactions with Other Species
Lythronax lived alongside a myriad of other creatures, among them hadrosaurs like Adelolophus and Acristavus and ceratopsians like Diabloceratops.
Ankylosaurs and pachycephalosaurs were quite common, too.
The Wahweap Formation revealed remains that belonged to at least 15 mammalian genera, among which were marsupials, placental insectivores, cladotherians, and multituberculates (rodent-like mammals).
Since the territory was predominantly aquatic, as it featured multiple rivers, lakes, and other water sources, marine creatures were quite abundant.
Sharks like Cantioscyllium and Chiloscyllium were inhabitants of prehistoric western North America.
It remains unknown whether Lythronax had any predators.
As far as paleontologists know, it was the largest predator in the ecosystem.
The fact that tyrannosaurids were usually apex predators in their respective habitats supports this theory.
On the other hand, who knows what future findings will show?
Cultural Significance
The discovery of Lythronax is the first evidence of tyrannosaurids featuring larger and more forward-directed orbits, suggesting that these characteristics appeared before 80 million years ago, much earlier than previously thought.
Many traits known in later tyrannosaurid genera may have their origins in Lythronax.
Furthermore, Lythronax remains are proof that there may be multiple other, possibly older, tyrannosaur genera that have not been discovered yet.
Another curiosity aroused by the discovery of Lythronax is related to the geographic distribution of tyrannosaurids.
If Lythronax shares the same lineage as later Asian forms like Tarbosaurus and Zhuchengtyrannus, how did the latter reach Asia?
In short, we cannot deny that Lythronax is possibly one of the most important theropod genera.
Hopefully, paleontological expeditions will reveal other specimens that will shed light on the evolution of tyrannosaurids!
On the other hand, Lythronax isn’t nearly as popular as the T-Rex in the universe of media productions.
It appears only in Jurassic World: Alive and Jurassic World: The Game.
How amazing would it be to see Lythronax featured in new productions portraying the evolution of tyrannosaurids?
Conclusion
Lythronax is the oldest known tyrannosaurid, which existed 81 million years ago during the Late Cretaceous.
Its discovery brought to scientists’ attention the fact that, as opposed to their previous assumptions, tyrannosaurids diversified earlier than 80 million years ago!
Upon discovering the fossils and assessing their importance in outlining the evolutionary history of tyrannosaurids, paleontologists put a lot of effort into describing the genus.
As such, they discovered that Lythronax had some unique features, among which were a remarkably wide back of the skull and a short snout.
Additionally, its eye sockets were almost forward-facing (similar to the eye sockets of the T-Rex), providing it with binocular vision.
Like other tyrannosaurids, Lythronax was probably the apex predator of its habitat and preyed on herbivores.
We cannot rule out the possibility of scavenging behavior.
Let’s not forget that Lythronax, the oldest member of the tyrannosaurid group, was a close relative of the youngest member of the group, Tyrannosaurus!
Can you believe that they were separated by roughly 13 million years?
FAQs
Was Lythronax feathered?
Earlier members of the Tyrannosauroidea may have been feathered, but this trait has not been confirmed in Lythronax.
Sources:
- https://en.wikipedia.org/wiki/Lythronax
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3819173/
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2396186/
- https://www.searchanddiscovery.com/pdfz/documents/2009/30088jinnah/ndx_jinnah.pdf.html
- https://en.wikipedia.org/wiki/Tyrannosaurus
- https://www.theguardian.com/science/2013/nov/06/lythronax-argestes-tyrannosaurs
- https://www.theguardian.com/science/2013/nov/06/king-gore-tyrannosaurus-rex-lythronax-argestes-dinosaur
- https://www.researchgate.net/publication/356879440_The_Origin_and_Evolution_of_Tyrannosaurids_Part_2_by_George_Olshevsky_and_Tracy_Ford_1995_Dino_Frontline
- https://archive.unews.utah.edu/news_releases/newly-discovered-predatory-dinosaur-king-of-gore-reveals-the-origins-of-t-rex/
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