Birds are the only living descendants of dinosaurs. While most modern birds have evolved to have feet suited to their lifestyles, such as perching feet or webbed feet, some birds retain anatomical features that connect them to their dinosaur ancestors. One such bird is the cassowary, which has feet that look strikingly similar to those of theropod dinosaurs.
What are the key features of dinosaur feet?
Theropod dinosaurs like Velociraptor and Tyrannosaurus rex walked on two powerful hind legs. Their feet had three forward-facing toes, with sharp claws for grasping prey. The first toe was often reduced or absent. Theropods are thought to have been active, agile predators. Their feet allowed them to run swiftly after prey.
Three functional toes
The three main toes on theropod feet gave them stability and balance for running. The asymmetry, with one toe being more reduced, may have given them greater maneuverability than creatures with four or five symmetrical toes on each foot.
Sharp claws
The claws on theropod toes could grow up to several inches long and were likely used as weapons. Some dinosaurs may have used their toe claws to slash or grip prey. Others like Velociraptor may have used their sickle-shaped claw for climbing.
Upright posture
Unlike many other reptiles, theropods stood upright on straight legs. This gave them an active, agile gait. It also freed up their forelimbs to be used as arms for grasping, ripping up prey, and balancing.
Digitigrade stance
Theropods walked on their toes with their heels off the ground. This digitigrade stance helped give them greater speed and range of motion than a flat-footed posture would allow.
How do cassowary feet compare to dinosaur feet?
Cassowaries are large, flightless birds that live in the forests of Australia and New Guinea. They are one of the closest living relatives to the theropod dinosaurs. Cassowary feet retain many of the key features that enabled theropods to become such successful predators.
Three-toed foot
Like theropod dinosaurs, cassowaries have three main forward-facing toes on each foot. Their inner toe is the largest and bears the most weight. The middle toe is slightly smaller with a long, straight claw used for defense. The outer toe is the smallest and highest up off the ground.
Sharp claw
The cassowary’s dagger-like middle claw can grow up to 5 inches long. They use this claw as a defensive weapon, slashing when they kick out with their feet. The claw is deadly enough to easily eviscerate predators and humans if provoked.
Powerful legs and upright stance
A cassowary’s legs are thick and muscular, allowing it to run up to 31 miles per hour. The cassowary’s upright posture and long legs are analogous to the theropods’ body plan.
Digitigrade feet
Cassowaries walk on the balls of their feet with their heels elevated, just as theropod dinosaurs did. This digitigrade stance facilitates speed and agility in the dense rainforest.
| Dinosaur Foot Feature | Cassowary Foot Feature |
|---|---|
| Three asymmetric toes | Three asymmetric toes |
| Sharp claws for slashing | Long dagger-like middle claw |
| Upright digitigrade stance | Upright digitigrade stance |
| Powerful legs for speed | Thick muscular legs for speed |
What other birds have dino-like feet?
While the cassowary’s feet most closely resemble a theropod dinosaur’s, other birds retain primitive features reminiscent of their dinosaur ancestors:
Ostriches and emus
Ostriches and emus are large, flightless birds that live in Australia and Africa respectively. They have long, powerful legs with two toes that allow them to run at speeds over 30 mph. The loss of one toe per foot is similar to the theropod footprint.
Chickens
The common chicken retains the dinosaur three-toed foot, though the outer toe is higher up like the cassowary’s. Chickens use their toes and claws for scratching, grasping, and balance while moving quickly in short bursts.
Turkeys
Turkeys have three unbalanced toes per foot, though weaker claws than chickens. The angles of their toe joints closely match those of theropod dinosaurs.
Rheas
Rheas are large, flightless birds from South America. They have three toes, but the outer toe is missing the claw, similar to some theropod dinosaurs like the ornithomimids.
Songbirds
Most perching songbirds have an anatomical feature called a hind toe that points backwards to grip branches. Though not weight-bearing, this vestigial toe offers evidence of the four-toed ancestral theropod foot.
Conclusion
The cassowary’s three-toed foot tipped with a long dagger claw makes it the modern bird with feet most similar to a dinosaur’s. Ostriches, emus, and other flightless birds also retain anatomical vestiges of their theropod ancestry. While adapted for perching or swimming, even common birds like chickens and turkeys echo some dinosaur traits in their feet. This enduring connection to their past emphasizes that birds truly are the only living dinosaurs.
