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Which Omnivore Dinosaur Was the Biggest?

Omnivorous dinosaurs were unique in that they consumed both plant matter and animals. You wonder about the traits of these dinosaurs, given their diet, especially their size. Were omnivorous dinosaurs particularly large, and which was the biggest?

The biggest omnivore dinosaur was the Deinocheirus, an ornithomimosaur from the Late Cretaceous Period with remains found in Mongolia’s Nemegt Foundation. It’s believed the Deinocheirus weighed 14,000 pounds, making it one huge dino species! It’s also notable for its huge forearms and claws.

If you want to learn even more about the fascinating yet exclusive group of omnivorous dinosaurs, you’ve come to the right place. In this article, we’ll talk further about the Deinocheirus as well as other omnivore species. Keep reading! 

Are Any Dinosaurs Omnivores? Which Dinosaurs Were Omnivores?

The question so much isn’t whether dinosaurs were omnivorous, as we know that some were. More so, the question is which species freely consumed plants and meat. Here is a list of those dinosaurs for your perusal.

Which-Omnivore-Dinosaur-Was-the-Biggest-AdventureDinosaurs
Gigantoraptor was an omnivorous theropod dinosaur, but it wasn’t the biggest. It had large hands with claws and its fossils were found in Mongolia – AdventureDinosaurs

Deinocheirus

Let’s start the list with the dino we already declared the biggest omnivorous dinosaur species, the Deinocheirus. As we mentioned in the intro, the Deinocheirus lived during the Late Cretaceous Period about 70 million years back. (Source)

We didn’t know too much about this dino species until 1965, when paleontologists recovered fossils in the Nemegt Foundation. The only identified species of Deinocheirus is the Deinocheirus mirificus, which is a Greek term that means “horrible hand.”

Why is it called horrible hand, you ask? The forelimbs–like a lot of the Deinocheirus–were huge! According to a 2014 USA Today article, its arms were eight feet apiece.

Let’s talk about this dinosaur’s massive size, for it’s sure to humble and impress. The Deinocheirus was believed to be 39 feet long. Its hips alone were 14 feet. It weighed up to 7.7 short tons, which is the equivalent of 14,000 pounds. 

Let us be clear – this size is not normal for omnivorous dinosaurs. You’ll see that in the rest of this section. The Deinocheirus is an anomaly.

YouTube Video About Zophia’s Monster – Deinocheirus

YouTube video by Benjamin Burger discusses the Deinocheirus discovery in detail. The video starts at 4:57 to skip to where the expedition to Mongolia starts – AdventureDinosaurs

The head of Deinocheirus is almost as captivating as its size. The dinosaur’s head almost resembles that of an ostrich or an emu with a duckbill and a long neck. Experts believe the dinosaur lacked teeth since it had a bill that allowed the Deinocheirus to catch fish from the water.  

Ornithomimus

The Ornithomimus is an ornithomimid with a name that translates to “bird mimic.” It lived in what’s modern North America during the Late Cretaceous Period. It, too, featured a long neck, lengthy arms, and a beak with no teeth. 

The length of its legs and three toes–which were made for bearing weight–suggest that the Ornithomimus would have been an excellent runner. 

Chirostenotes

From the Greek word meaning “narrow-handed,” the Chirostenotes is an oviraptosaurian that lived in today’s Alberta, Canada, during the Late Cretaceous Period roughly 76.5 million years back. 

Its single species, the Chirostenotes pergracillis, was officially named in 1924. With a wealth of fossilized remains from before and since then, we can confidently say that the Chirostenotes was a beaked dinosaur with long arms that featured straight claws.

Its rear legs would have had skinny toes, probably to augment its running ability. The average size of a Chirostenotes was about 8.2 feet, and it weighed 220 pounds, so it’s quite a deal smaller than the Deinocheirus.

Here’s something interesting too: the Chirostenotes might have been covered from head to toe in feathers! 

Avimimus

Sharing a name origin with the Ornithomimus (as the Avimimus’ name also means “bird mimic”), the Avimimus occupies a genus with other oviraptorosaurian theropods. It lived roughly 80 million years ago during the Late Cretaceous Period, with remains located in Mongolia.

Extremely tiny, the average size of the Avimimus was five feet long. Its skull wasn’t very large, but its eyes were. Its brain might have been bigger than what looked like it could have fit inside the dinosaur’s head. 

The beak of the Avimimus has been likened to that of a parrot, although it had teeth. The inclusion of teeth is what bears credence to the idea that the Avimimus was an omnivore. 

Gigantoraptor

The massive Gigantoraptor certainly gives the Deinocheirus a run for its money in the size department. Gigantoraptor was about 29 feet long and weighed 2.7 tons, so it’s not quite as large. This species was also recovered in Mongolia, specifically the Iren Dabasu Formation. It lived in what is now Asia in the Late Cretaceous Period. (Source)

Experts believe the Gigantoraptor had a rhamphotheca, which is a type of beak. It’s not clear whether the Gigantoraptor had teeth as well, but none have been recovered from this large dinosaur species. 

It shares traits with other omnivores, as discussed in this section. For instance, the Gigantoraptor had a long neck, a sturdy body, lengthy arms, and strong hind legs. It also might have featured feathers from its head along its body and covering its arms.

Interestingly, expeditions are still taking place in Mongolia in the exact places where Gigantoraptor and other Mongolian dinosaurs have been found (Source).

Khaan

The last omnivorous dinosaur we want to talk about in this section is the Khaan, an oviraptorid that lived about 75 million years ago during the Late Cretaceous Period. Its remains have been recovered in Mongolia’s Djadochta Formation. 

Believed to have consumed mollusks and plants, the Khaan also munched on tiny dinos, lizards, and other small mammals that crossed its path. Paleontologists and other experts are surer compared to most dinosaurs that the Khaan was very much feathered. It also had a blunt beak. 

How Can You Tell If a Dinosaur Was Omnivorous?

How did experts classify the above dinosaur species as likely omnivores? 

Well, as you read the last section, you probably noticed some similarities. One obvious reason is that every omnivore on this list lived during the Late Cretaceous Period, which lasted as long as 100 million years ago (although in the case of many dinosaurs, it was between 70 and 85 million years ago).

Many remains of the above omnivorous dinosaurs were recovered around Mongolia. Compared to other environments during the Cretaceous Period, Mongolia at the time is preserved well, so we have a lot of details about what it was like. 

The lands were dry, but some greenery existed. For the dinosaurs that lived in Mongolia’s Mount Altai, food wasn’t particularly prosperous. Dinosaurs, including oviraptors, competed with Velociraptors to eat. 

Could this have been what drove the dinosaurs of the age to become omnivorous? Perhaps they started as carnivores but later adapted to eat plant materials as well to ensure their survival. Vice-versa could have been true too.

Other shared traits among omnivorous dinosaurs are long arms (often with claws) and the presence of beaks. Some omnivorous dinos had teeth inside their beaks, but most were believed to be toothless.

Beaks could have allowed a dinosaur to tear through flesh and possibly crunch through bone, but that would have depended on the bite force of the dinosaur in question. Recalling that most omnivores were smaller dinosaurs, we don’t think their bite force would have been too tremendous. Maybe the Deinocheirus could have bitten through bone, though.

Omnivorous dinosaurs could have used their beaks to scoop up fish until they could rest and eat, which is a behavior that some modern-day bird species will exhibit. We also know through today’s birds that beaks can separate plants from mud or dirt so they can pluck only what they want. 

What Is the Strongest Omnivore Dinosaur? What Was the Smallest Omnivore Dinosaur? 

Since omnivore dinosaurs relied on two food sources to survive, it reasons to assume that these species would be quite strong. We’re not saying an omnivore would go toe-to-toe with a T. Rex or anything like that, but other predators might have stood down when in a particularly strong omnivore dinosaur’s presence.

There’s only one omnivore that fits the bill, and we think you know what it is. That’s right, and it’s the Deinocheirus. This dinosaur outsized other omnivores by such a drastic margin that, of course, its strength would be far more tremendous as well. 

Which omnivorous dinosaur would have the distinction of being the teeny-tiniest? 

That title goes to a dinosaur we have yet to discuss in this post, the Fruitadens haagarorum. Fruitadens are very small dinosaurs believed to have lived in the Late Jurassic Period. Their remains have been traced to Colorado’s Morrison Foundation, which is a far cry from Mongolia.

An ABC Science article from 2009 states that the Fruitadens haagarorum was an ornithischian that measured just 70 centimeters or 27.55 inches. In its mouth were rows of teeth ideal for crunching on insects and small animals. 

It’s believed that the Fruitadens’ teeth were not uniform throughout its entire mouth, which means it could have relied on some teeth for eating plants and others for chewing on meat. 

Conclusion 

Omnivores are unique dinosaurs in a very exclusive club that could eat meat and plants and digest both types of food. Most omnivorous dinosaurs were incredibly small, but one species, the Deinocheirus, remains the biggest of this special group. 

Although we still have plenty to learn about omnivorous dinosaurs, the information we have now is completely captivating! 

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