In the vast expanses of Late Cretaceous Mongolia, a truly unique dinosaur once roamed. Deinocheirus, which translates to “Terrible Hand,” is renowned as much for its distinctive and peculiar anatomy as it is for the captivating story of its discovery. This massive ornithomimosaur offers a fascinating glimpse into the ever-startling diversity of theropod dinosaurs that thrived in the twilight of the dinosaurian reign, around 70 million years ago.
Unearthed in the Nemegt Basin, Deinocheirus was first discovered by Zofia Kielan-Jaworowska in 1965 as part of a Polish expedition of paleontologists within Mongolia. Its remarkable size and unusual physical characteristics have puzzled paleontologists since its formal description by Halszka Osmólska and Ewa Roniewicz in 1970. Let’s delve into the intriguing world of Deinocheirus, exploring its origins, anatomy, and the environment it once inhabited.
Deinocheirus Key Facts
| Details | Key Facts |
|---|---|
| Pronunciation | DIE-no-KYE-rus |
| Meaning of name | Terrible Hand |
| Group | Theropoda |
| Type Species | Deinocheirus mirificus |
| Diet | Herbivorous with some omnivory |
| When it Lived | 72.1 to 66.0 MYA |
| Period | Late Cretaceous |
| Epoch | Maastrichtian |
| Length | 36.0 feet |
| Height | 15.0 feet at the top of the head when standing upright |
| Weight | 6.5 tons |
| Mobility | Bipedal – moved on two legs |
| First Discovery | 1965 by Zofia Kielan-Jaworowska |
| Described by | 1970 by Halszka Osmólska and Ewa Roniewicz |
| Holotype | ZPAL MgD-I/6 |
| Location of first find | Nemegt Basin, Mongolia |
Deinocheirus Origins, Taxonomy and Timeline
Deinocheirus, meaning “Terrible Hand,” is derived from the Greek words “deinos,” meaning terrible, and “cheir,” meaning hand. This name aptly reflects the dinosaur’s enormous and unusual forelimbs, which were unlike anything seen before. Pronounced DIE-no-KYE-rus, the name encapsulates the awe and mystery surrounding this dinosaur. The type species, Deinocheirus mirificus, is currently the only known species within the genus.
Taxonomically, Deinocheirus belongs to the group Theropoda, that group of bipedal and ultimately flighted dinosaurs that have stuck around to the present day. Within Theropoda, Deinocheirus belongs to ornithomimosaurs, or the “bird mimic” dinosaurs – so named because their slender, gracile frames, clearly built for speed, reminded palaeontologists of ostriches. However, as we will see below, Deinocheirus breaks with this mould in a rather spectacular way, possessing a unique set of characteristics that set it apart from other ornithomimosaurs.
Deinocheirus lived during the Late Cretaceous Period, specifically in the Maastrichtian Epoch, which spans from approximately 72.1 to 66.0 million years ago. This era was marked by significant evolutionary developments and a rich diversity of life forms. Understanding the timeline of Deinocheirus helps contextualize its existence within the broader narrative of dinosaur evolution during the Late Cretaceous.
Listen to Pronunciation
To listen to the correct pronunciation of this dino’s name, check out this video.
Discovery & Fossil Evidence
Deinocheirus was first discovered in 1965 at the Altan Ula III site in the Nemegt Basin, located in the South Gobi region of Mongolia. The discovery, led by Zofia Kielan-Jaworowska, was part of a significant Polish-Mongolian paleontological expedition. The holotype specimen, cataloged as ZPAL MgD-I/6, included a pair of enormous forelimbs, These forelimbs, which are among the largest of any known bipedal dinosaur, immediately captured the attention of the scientific community.
In 1970, paleontologists Halszka Osmólska and Ewa Roniewicz formally described Deinocheirus, emphasizing its unique and puzzling anatomy. However, with only a pair of giant forelimbs and a few other grahments to go by, palaeontologists were originally stumped as to what kind of dinosaur Deinocheirus really was. Most suspected it to be a giant species of heretofore unknown predatory dinosaur, but other than that there was little could be said about it.
This situation changed dramatically in 2013, when a team led by American palaeontologist Phil Currie announced the discovery of two additional specimens of Deinocheirus. These specimens had originally been unearthed between 2006-2009 during expeditions to the Nemegt Basin. However, it transpired that these quarries had been pillaged several years earlier by fossil poachers, and it took another several years of incredibly good luck and convivial international relations before the pilfered elements were repatriated to Mongolia.
Once reunited with their poached parts, these two new specimens represented an almost complete skeleton between them – including a well preserved skull. This new fossil trove finally allowed paleontologists to put the proverbial flesh back on the enigmatic bones of Deinocheirus, revealing the extraordinary nature of this singular dino.
Reconstructed skeleton in Japan
Forelimbs and shoulder girdles of holotype specimen MPC-D 100/18 on temporary exhibit in CosmoCaixa
Cast of specimen MPC-D 100/127’s skull (the first known skull of this genus), on exhibit at Munich Fossil Show
Holotype specimen MPC-D 100/18 on exhibit in CosmoCaixa
Deinocheirus Size and Description
Description of Deinocheirus
Even amongst giants, Deinocheirus was massive by theropod standards, distinguished by its formidable size and unique anatomical features. Unlike its gracile ornithomimosaur cousins, its body structure was robust, sporting strong, elongated forelimbs with large, curved claws. In contrast to original assumptions of prey-seizing, these limbs appeared to be built more for digging up plants and as an additional support strut when wading in mud.
The most notable feature of the skull is its wide, bill-like mouth, similar to that of a duck’s. This feature is much more specialized than the mouth of other ornithomimosaurs. Indicating a mouth adapted for feeding on a variety of plant materials.
However, the most striking feature of Deinocheirus was its massive, elongate dorsal neural spines, which were fused together to form a kind “sail” extending the length of its back – similar to that seen in Spinosaurus. The function of this sail (or perhaps “hump” is a better descriptor) can currently only be guessed at, but was possibly used in display.
While direct evidence of skin is not available, the tail of Deinocheirus ended in at least two fused vertebrae, which were described as similar to the pygostyle of other derived theropods, suggesting that the tail of Deinocheirus may have sported a fan of feathers at its end. The rest of its body likewise is presumed to have been semi-if-not-fully-covered in a bird-like plumage.
Size and Weight of Deinocheirus
Deinocheirus measured approximately 36.0 feet in length and stood about 15.0 feet tall at the top of the head. Weighing around 6.5 tons, this dinosaur was one of the largest Theropods of its era and the largest known ornithomimosaurian. Its considerable size and weight suggest a creature less built for speed like other ornithomimosaurs, and one built for endurance and strength, well-suited for a herbivorous diet.
This substantial stature would have been advantageous in deterring predators and accessing various types of vegetation. The available fossil evidence provides a reliable basis for these size and weight estimates, underscoring the impressive physical presence of Deinocheirus. The extraordinary size of Deinocheirus highlights the incredible adaptability of theropod dinosaurs and the evolutionary pathways that enabled their success and staggering diversity in the Late Cretaceous.
The Dinosaur in Detail
In contrast to its massive bulk, Deinocheirus was also notable among ornithomimosaurs for the relatively compact size of its brain and the reduced size of its sclerotic rings – the bony cup which braced the eyeballs from behind. Taken together, this suggests an animal with reduced visual acuity that also didn’t need to be as nimble on its feet as its road-running cousins. This is consistent with a lumbering herbivore that possibly spent most of its time foraging in full daylight.
Moreover, the post-cranial skeleton of Deinocheirus was also amongst the most pneumatized of dinosaurs. With most of its vertebrae invaded by air sac extensions of the respiratory system. This adaptation, useful for assisting modern birds in flight, has also been correlated with gigantism in dinosaurs, and likely represented a useful mass-reduction measure in colossal bipeds like Deinocheirus.
The unique combination of physical and sensory adaptations highlights the evolutionary adaptability of Deinocheirus, showcasing its role within the complex ecosystems of the Late Cretaceous.
Contemporary Dinosaurs
Deinocheirus shared its habitat with several other notable dinosaurs, showcasing a dynamic and competitive ecosystem. Among these contemporaries were Tarbosaurus, Velociraptor, Protoceratops, and Gallimimus, each contributing to the intricate web of life during the Late Cretaceous.
Tarbosaurus, a massive predatory dinosaur and T-rex relative, was one of the dominant carnivores in the region. Its presence would have posed a significant threat to Deinocheirus, influencing its behavior and survival strategies. In fact, some Deinocheirus bones show evidence of predation by Tarbosaurus. The interactions between these two giants provide insights into the predator-prey dynamics that shaped their environment.
Another contemporary is Velociraptor, known for its agility and hunting prowess. Though smaller in size, Velociraptor was a formidable predator, possibly capable of taking down larger prey through coordinated pack hunting. The coexistence of Deinocheirus and Velociraptor underscores the diversity of predatory strategies in the Late Cretaceous.
Protoceratops, a small herbivorous dinosaur, also inhabited the same region. Its presence indicates a rich and varied plant life that supported multiple herbivorous species. The interactions between Deinocheirus and Protoceratops would have centered around competition for vegetation. Highlighting the complex ecological relationships within their shared habitat.
Also present in this period is Gallimimus, a fast and agile near-relative of Deinocheirus. Gallimimus was likely more omnivorous than Deinocheirus, chasing down small prey when the opportunity availed itself. A distinction of feeding strategies may have reduced direct competition. The diversity of theropods like Gallimimus and Deinocheirus illustrates the adaptations allowing these dinosaurs to thrive in the Late Cretaceous.
Interesting Points about Deinocheirus
- Despite its massive size, Deinocheirus was a herbivore, adapted to feeding on a variety of plant materials. However, the presence of fish-scales in association with its fossils suggests that Deinocheirus was possibly omnivorous. With a diet including plants, small animals, and fish.
- The first discovery of Deinocheirus included only its forelimbs, leading to much speculation about its full appearance.
- Deinocheirus lived alongside other famous dinosaurs like Tarbosaurus and Velociraptor, creating a diverse and dynamic ecosystem.
- It had unique physical adaptations, including a duckbill-like mouth and large back sail/hump, distinguishing it from more streamlined ornithomimosaurs.
Deinocheirus in its Natural Habitat
Deinocheirus inhabited the Nemegt Basin in what is now Mongolia. A region characterized by varied landscapes and rich biodiversity during the Late Cretaceous. The climate was warm, with seasonal variations that influenced the availability of water and vegetation. This environment supported a wide range of plant life, providing ample food sources for herbivorous dinosaurs like Deinocheirus.
As a herbivore, Deinocheirus primarily fed on plants, using its powerful forelimbs to manipulate food. The bill-like mouth was well-suited for cropping vegetation,. Its large size made it necessary to consume significant quantities of plant matter. These feeding habits would have influenced the local vegetation patterns, as Deinocheirus played a role in shaping the landscape. However, recent findings indicate that Deinocheirus may have had an omnivorous diet. Consuming not only plants but possibly also small animals and fish nabbed from the water’s margins.
The social behavior of Deinocheirus is not well understood. However, it is possible that it lived in groups or herds, as many large herbivores do. Likely congregating during egg-laying periods. This social structure would have provided protection from predators and facilitated efficient foraging. Additionally, the sensory adaptations of Deinocheirus, such as reduced visual acuity, suggests an animal that practiced a more diurnal than nocturnal lifestyle.
Frequently Asked Questions
Deinocheirus was first discovered in 1965 by Zofia Kielan-Jaworowska in the Nemegt Basin, Mongolia.
The name Deinocheirus means “Terrible Hand,” derived from Greek words describing its large forelimbs.
Deinocheirus was a herbivore, primarily feeding on a variety of plants and vegetation available in its habitat. However, recent studies indicate that Deinocheirus had an omnivorous diet, consuming not only plants but also small animals and fish.
Deinocheirus measured about 36.0 feet in length, stood 15.0 feet tall, and weighed around 6.5 tons.
Deinocheirus lived during the Late Cretaceous Period, approximately 72.1 to 66.0 million years ago.
Deinocheirus had enormous forelimbs with large claws, a bill-like mouth, and pronounced back sail/hump.
Sources
The information in this article is based on various sources, drawing on scientific research, fossil evidence, and expert analysis. The aim is to provide a comprehensive and accurate overview of Deinocheirus.
Article last fact checked: Joey Arboleda, 06-07-2024
Featured Image Credit: PaleoNeolitic, CC BY 4.0, via Wikimedia Commons
