Cassowaries are large, flightless birds that live in the rainforests of New Guinea and northeastern Australia. They bear a superficial resemblance to theropod dinosaurs like velociraptors due to their large size, long claws on their toes, and the bony casque on their heads. This leads many people to wonder – are cassowaries living dinosaurs?
The cassowary’s dinosaur-like traits
There are several features of the cassowary that make it seem prehistoric or dinosaur-like:
- Cassowaries are very large birds, standing up to 6 feet tall and weighing up to 130 pounds. This approaches the size of many theropod dinosaurs.
- They have a tall, bony casque on top of their head reminiscent of the crests on dinosaurs like Parasaurolophus.
- Their feet have three toes, the inner one bearing a long, dagger-like claw up to 4 inches long. This claws of their feet resembles the sickle-like claws on the feet of theropod dinosaurs like velociraptors.
- Cassowaries are flightless, like many theropod dinosaurs.
- They have small wings with clawed fingers, similar to the reduced arms and hands of tyrannosaurids and other large theropods.
- Their feathers lack barbicels, making them more hair-like rather than like typical bird feathers.
With these dinosaur-like qualities, it’s easy to see why people might mistakenly think the cassowary is a modern-day dinosaur. However, birds evolved from feathered theropod dinosaurs over 150 million years ago, and are classified scientifically as avian dinosaurs. Let’s take a closer look at the evidence.
Evidence that cassowaries are birds, not dinosaurs
While cassowaries share some physical traits with theropod dinosaurs, they are actually modern birds, and dinosaurs have been extinct for over 65 million years. There is overwhelming evidence that cassowaries are not dinosaurs:
- Cassowaries have beaks and feathers, which are unique to birds and not present in dinosaurs.
- They lay hard-shelled eggs, a trait of birds not shared by any dinosaurs.
- Cassowaries have a four-chambered heart, unlike the three-chambered hearts of dinosaurs.
- They share numerous skeletal and anatomical similarities with other living birds, including hollow bones, a furcula or wishbone, and pneumatic bones.
- Their genome has been studied and confirmed to be that of an avian, closely related to other ratites like ostriches and emus.
- Fossil evidence shows modern birds like cassowaries evolved from feathered theropods over 150 million years ago, while non-avian dinosaurs went extinct 65 million years ago.
- Behavioral evidence like vocalizations, nesting, and parental care are also distinctly avian in cassowaries.
While cassowaries certainly resemble theropod dinosaurs in some ways, biologically they are undeniably birds. The shared characteristics can be attributed to their evolutionary descent from theropod dinosaurs. Next, we’ll explore that connection in more detail.
The evolutionary origins of cassowaries
The evolutionary lineage of birds is well-established by the fossil record and DNA evidence. Birds evolved from small feathered theropod dinosaurs during the Jurassic Period over 150 million years ago. They retained some dinosaur-like features, like claws, through this evolutionary transition. Here are some key points about cassowary evolution:
- Cassowaries belong to a group called palaeognath birds that includes ostriches, emus, rheas, and kiwis. This group split from other birds over 80 million years ago.
- The earliest cassowary fossils date to 15-20 million years ago in Australia, but they likely diverged from emus 40-60 million years ago.
- Their closest dinosaur relatives were small feathered theropods like Anchiornis and Microraptor that lived over 150 million years ago.
- Key adaptations like loss of flight, robust legs, and sharp claws evolved later as cassowaries adapted to life in the dense rainforest.
The cassowary lineage clearly traces back to avian theropod dinosaurs in the Jurassic, not non-avian dinosaurs that went extinct at the end of the Cretaceous Period 65 million years ago. They do retain a number of primitive traits that give them a prehistoric appearance, but these represent vestiges of their ancestry, not evidence that they are somehow dinosaurs that survived extinction.
Could a cassowary be considered a living dinosaur?
While cassowaries descended from dinosaurs and retain some dinosaur-like features, most scientists argue they cannot be considered true living dinosaurs. Here are some reasons why:
- Cassowaries lack key anatomical features present in all dinosaurs, like three-chambered hearts and non-avian bone structure.
- They possess distinctly avian features like beaks, feathers, and hollow pneumatic bones not found in any dinosaurs.
- There is no fossil evidence showing non-avian dinosaurs evolving beaks, feathers, hollow bones, wishbones, or other avian traits that are present in cassowaries.
- Their genome and all genetic evidence aligns cassowaries with other living birds, not with non-avian dinosaurs.
- At most, cassowaries could be considered “avian dinosaurs,” but are very different biologically from non-avian dinosaurs.
Most experts agree there is an overwhelming amount of anatomical, fossil, genetic, and behavioral evidence showing cassowaries are modern birds, albeit with evolutionary ties to dinosaurs. They descended from avian dinosaurs, but cannot be classified as true dinosaurs themselves. However, a few dissenting scientists think their dinosaur-like traits do merit classifying them as “living dinosaurs.”
The minority argument for cassowaries as living dinosaurs
Despite the consensus that cassowaries are avian rather than non-avian dinosaurs, a minority of scientists make the argument that cassowaries deserve to be classified as “living dinosaurs” based on the following:
- Their reptilian appearance, from the casque to their dinosaur-like feet, sets them apart from other modern birds.
- Though not identical, their morphology is much closer to extinct theropods than any other living creature.
- Biologically speaking, birds are avian dinosaurs, so cassowaries are essentially dinosaurs regardless of semantics.
- Birds like cassowaries fill similar evolutionary niches to those of extinct theropods.
- Referring to them as “living dinosaurs” can help generate interest in protecting these rare and unusual birds.
However, most paleontologists counter that this is an exaggerated view that ignores major biological differences between avian and non-avian dinosaurs. The “living dinosaur” label seems based more on appearance than science. Nonetheless, a minority contends that if it looks like a dinosaur and lives like a dinosaur, cassowaries could informally be considered “honorary dinosaurs.”
Conclusion
In summary, while cassowaries do share some remarkable similarities with extinct theropod dinosaurs, the evidence overwhelmingly shows they are modern birds, not actual dinosaurs. Their dinosaur-like traits represent evolutionary vestiges from avian theropod ancestors over 150 million years ago. While a minority argues their appearance merits the “living dinosaur” label, most experts maintain they are avians, not non-avian dinosaurs. However, their uniqueness among birds keeps the debate alive for those who want to imagine encountering a real living dinosaur in the rainforests where cassowaries roam.