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Among the most famous dinosaurs of all time, they were agile, active, feathery predators of habitats all over the world during the Cretaceous Period. This episode, we discuss the diverse lifestyles and notorious mysteries of Dromaeosaurs.
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Dromaeosauridae
Dromaeosaurs are a group of predatory theropod dinosaurs which includes some of the most famous fossil species of all time, such as Deinonychus, Microraptor, and Velociraptor. During the Cretaceous Period, these dinosaurs lived in a variety of habitats all over the world, and they ranged from the size of ravens (as in Microraptor and Rahonavis) to the size of grizzly bears (as in Utahraptor and Achillobator).
Art by Fred Wierum, CC BY-SA 4.0
Typical dromaeosaur features include: long arms, large hands, flexible shoulder and wrist joints, long stiff tails, a diverse array of feathers across the body, and – most famously – a large, retractable, sickle-shaped claw on the inner toe of each foot.
Top right: Fossil of Microraptor. Image from Hone et al. 2010, CC BY 2.5
Bottom: Skeleton of Deinonychus. Image by Jonathan Chen, CC BY-SA 4.0
Dromaeosaurs belong to a group called Eumaniraptora, alongside Avialae (the lineage of true birds) and Troodontidae. Dinosaurs in all three groups share many distinguishing features, and in fact, the early members of these lineages are so similar that paleontologists often have a hard time sorting out their relationships to each other. Early dromaeosaurs would have been very difficult to tell apart from early birds.
Claws and Wings
Dromaeosaurs’ feathery arms and legs might have served a variety of functions, from insulation to display, and a few species – such as Microraptor and Rahonavis – have been interpreted as fliers, or at least capable gliders. Currently, it’s unclear how airborne these dromaeosaurs could be, or how widespread flight was within the group; some scientists have even suggested that flight might have been common among small dromaeosaurs.
Over the decades, many hypotheses have been proposed and tested regarding the function of dromaeosaurs’ sickle claws. These include slashing open large prey, pinning down or crushing small prey, stabbing at each other in competitive fights, climbing trees, digging out burrows, and more. Most recent research has found that dromaeosaur feet and claws likely weren’t well-suited for slashing or digging, but that they have a lot in common with modern birds of prey, which use their talons to grip and pin food, and with birds like cassowaries and sandhill cranes, which use enlarged claws for defensive stabbing kicks.
Perhaps the most famous hypothetical behavior of dromaeosaurs is pack hunting. This idea became popular in the scientific literature in the 1960s-70s when it was proposed as a possible lifestyle for Deinonychus, which, in addition to being an agile wolf-sized predator with a fairly large brain, had a habit of being fossilized nearby the large herbivore Tenontosaurus. This hypothesis later became globally famous thanks to the pack-hunting velociraptors of Jurassic Park. However, this idea has been questioned due to a lack of convincing fossil evidence and the rarity of true pack hunting in most animals. There is evidence from footprints and skeletal assemblages to support the idea that some dromaeosaurs lived and moved in groups, but whether they hunted in a coordinated fashion like wolves or lions isn’t clear.
Top: Microraptor coming in for a landing. Image by Durbed, CC BY-SA 3.0
Bottom: Velociraptor restraining dinosaur prey. Image by Durbed, CC BY-SA 3.0
Right: Natovenator swimming and hunting in water. Image from Lee et al 2022, CC BY 4.0
Most dromaeosaurs were small-ish predators on land, like Dromaeosaurus and Velociraptor, but some, like Microraptor or Rahonavis, might have been semi-arboreal, spending time in trees (or in the air between them!), and some were even semi-aquatic – it has recently been discovered that Halszkaraptor and Natovenator had very duck-like bodies and were probably adept at aquatic hunting.
Learn More
Newly Discovered Swimming Dinosaur Is Delightfully Bizarre
Cretaceous Bird-Like Dinosaur Had Adaptations for Swimming and Diving
Testing the function of dromaeosaurid ‘sickle claws’ (technical, open access)
Morphological Variations within the Ontogeny of Deinonychus antirrhopus (technical, open access)
Ontogenetic dietary shifts in Deinonychus antirrhopus (technical)
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If you enjoyed this topic and want more like it, check out these related episodes:
- Episode 37 – Evolution of Birds
- Episode 42 – Spinosaurs
- Episode 120 – Tyrannosaurs
- Episode 183 – Feathers
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