“ Life is at its harshest in the far north and south of planet Earth. Dinosaurs, however, have managed to colonize these polar regions. In the far north of America, this tiny hunter, a dromaeosaur, has managed to survive three months of near-total darkness. And now, at last, spring has come. ”
Dromaeosaurus[DN 1] (Running Lizard) is a genus of dromaeosaurid theropod dinosaur that lived in western North America 80 - 69 million years ago, from the Campanian to the Maastrichtian stage of the Late Cretaceous Period. Prehistoric Planet's depiction of the species is likely based on the remains of teeth comparable to those of D. albertensis.[1][2]
“ She has a coat of feathers, for she's able to generate heat in her body, and needs to retain all she can, a challenge for all dinosaurs in these cold latitudes. ”
Dromaeosaurus is the type species of the dromaeosaurs, a group of small, predatory maniraptoran theropod dinosaurs known for the sickle claws on the second toes of their feet, as well as their close relationship with birds. By the standards of its group, Dromaeosaurus is medium-sized (equivalent to a coyote), possessing a height of around 60 centimeters (2 feet), an approximate length of 2 meters (6 feet, 7 inches), and a mass of 16 kilograms (35.3 pounds).[7][8] It was only slightly larger than its relative, Velociraptor, though it is notably more heavily-built for a dromaeosaur its size.
Jaws and Dentition[]
Befitting its more robust physique compared to dromaeosaurs of similar size, Dromaeosaurus has a short yet massive skull, with only 42.1% of its total surface area lightened up by fenestrae (skull openings).[10] It had a deep mandible and robust teeth that, based on how heavily-worn they are, were likely used for crushing and tearing more than merely slicing flesh. This suggests that Dromaeosaurus had a bite force thrice that of Velociraptor, and therefore relied more on its jaws than on its sickle claws to kill prey. A study in 2019 suggests that Dromaeosaurus, along with its cousin Saurornitholestes, can feed on bone and take on larger, tougher prey than their cousins, the more gracile troodontids, almost like miniature versions of the tyrannosaurs they lived alongside.[11][12] This is further supported by a 2022 study that estimates the bite forces of some dinosaurs, suggesting that a Dromaeosaurus with a skull width of 10.3 centimeters (4.1 inches) exerted a bite force of 443 newtons or 45.4 kilograms (100 pounds) in the front of its jaws, and 885 newtons or 90.72 kilograms (200 pounds) in the back of its jaws.[9]
It is believed that gracile dromaeosaur snouts like those of Velociraptor are a basal trait, inherited from the last common ancestor of dromaeosaurs and troodontids (which still retained slender snouts), while more robust rostrums like those of Dromaeosaurus and Deinonychus were more derived. The temporal muscle group of Dromaeosaurus possessed a mechanical advantage of 0.242, and its quadrate muscle group had a mechanical advantage of 0.395.[10] Lower mechanical advantages indicate that an animal's jaws prioritized closure speed, while higher mechanical advantages like those of Dromaeosaurus prioritized bite forces. Furthermore, the jaws of Dromaeosaurus had a mesh-weighted arithmetic mean of 309 microstrain, indicating that it experienced low stress when biting, and therefore had a very high resistance to its own bite force.[10] By comparison, a Velociraptor with a skull width of 9.1 centimeters (3.6 inches) possesses an anterior (front) bite force of 131 newtons or 13.61 kilograms (30 pounds), a posterior (back) bite force of 304 newtons or 31 kilograms (68.34 pounds),[9] and a low mesh-weighted arithmetic mean of 360 microstrain. As is the case for modern-day birds and mammals, it is believed that carnivores with high bite force resistance were scavengers, more reliant on processing carrion, while those with low bite force resistance were more reliant on freshly-killed prey. These indicate that, while Dromaeosaurus had the adaptations to overpower and kill live prey when needed, it possibly preferred to scavenge rather than hunt.[10]
Prehistoric Planet's Portrayal[]
Dromaeosaurus concept art by Gaëlle Seguillon. The image's original filename indicates that this was intended to be a female.
On Prehistoric Planet, Dromaeosaurus is depicted with thick plumage, black on the back and white on the underside. This is known as countershading, which helps an animal, be it predator or prey, to blend with the light when viewed from above or the shadows when viewed from below. Their arms have brown wing feathers, and their pygostyles (tail fans) come in a striking shade of blue, faintly resembling the simpler, proportionally smaller tail fan of Deinocheirus. On the tip of their tails are a pair of white, elongated feathers that end in diamond-shaped structures. Like the unidentified Alaskan troodontid, Atrociraptor, and Imperobator, Dromaeosaurus is depicted with legs that are heavily-feathered like those of a booted eagle, in contrast with other paravians in the series like Velociraptor, which have bare legs. This trait is likely an adaptation for the cold environment it lived in. Official concept art by Gaëlle Seguillon shows that the conceived design (which originally had the pair of long diamond-shaped tail feathers in the same shade of blue as the rest of the pygostyle) was originally meant to depict the female, though the dromaeosaurs seen on Prehistoric Planet do not appear to have any discernible differences, indicating that the show may not have intended to depict Dromaeosaurus as a sexually dimorphic species.[PhP 1]
“ Although at this time in Earth's history, the polar regions are relatively warm, these lands are nonetheless ruled by extreme seasonal change. When the sun rises for the first time in almost three months, every animal must be ready to make the most of the daylight, and the warmer days that are to come. ”
Dromaeosaurus was originally discovered in the Dinosaur Park Formation, which dates back to 77 - 74 million years ago. Based on teeth, Dromaeosaurus is also known to have lived 81 - 80 million years ago in the Aguja Formation, which stretches from Texas, USA to Chihuahua and Coahuila, Mexico.[6] On the show, Dromaeosaurus (again, on the basis of teeth) is also depicted as having lived 71 - 69 million years ago in the Prince Creek Formation, a polar woodland that experienced 120 days of winter darkness, with temperatures dropping as low as 2 - 4 degrees Celsius (36 - 39 degrees Fahrenheit) during the cold months. More teeth and more fragmentary remains found in the Hell Creek, Lance, and Scollard Formations indicate that it lived up to the end of the Cretaceous Period, 66 million years ago, and thus witnessed the Cretaceous-Paleogene Extinction Event, a catastrophe that wiped out three-quarters of life on Earth, including all non-avian dinosaurs.[3][4][5]
Hunting Tactics and Feeding Preferences[]
A pair of Dromaeosaurus nuzzling
“ As she moves quickly over the surface of the snow, she checks on the places where she has found food in the past. In this icy world, no opportunity is too small to be ignored. And to succeed, as usual, you need good... timing. ”
Like Velociraptor, Dromaeosauruses are portrayed as solitary hunters of small prey that cooperate in certain situations to hunt greater prey, with individuals greeting each other with a nuzzle. The dromaeosaurs are also shown to use their predatory cunning to secure their prey, be it by judging an insect's flight path and timing a jump to intercept or catch it, or by spreading fear and panic in a herd of animals hundreds of times their mass, all the way down to letting greater forces of nature, like a raging river, claim the lives of their target for them, conserving effort and power on their part.
Prehistoric Planet depicts Dromaeosaurus hunting during dawn as well as in broad daylight. This behavior is supported by a study in 2021, where a comparison with the alvarezsaur Shuvuuia suggested that Dromaeosaurus and Tyrannosaurus primarily hunted during daytime.[13][14] This is in sharp contrast with Velociraptor, which had large scleral rings that indicated that it was a nocturnal animal.[15]
Appearance[]
The first segment of Ice Worlds begins with a view of the aurora borealis in the far north of America. Footprints are seen in the snow, leading to the one who left them. In the early hours of the first morning of spring, a sleeping Dromaeosaurus wakes up, scratches herself for a while, and rushes off into the forest, digging through the snow and the rocky ground in hopes of getting a meal where she has found food before. Focusing on a beetle as it climbs up a branch, flipping its wings in preparation for takeoff, she prepares her attack, jumping and snapping up at the beetle just as it flew off the branch, getting her first meal in a long while.
“ The little dromaeosaurs must work together if they are to take on big prey. And here comes their first chance of the season; a herd of hadrosaurs. These duckbilled dinosaurs pass through here every year, nomads in search of the fresh vegetation brought by the spring. They're huge. The only chance the dromaeosaurs will have is to work as a team. ”
As the sun rises over the mountains of Alaska for the first time in almost three months, two dromaeosaurs nuzzle each other before turning their attention to the bellows of a herd of dinosaurs in the distance.
“ As winter slackens its grip, meltwater begins to flow with great power. The herd must wade through this deep, fast-flowing water. The leaders try to select the safest crossing. The herd follow cautiously. Young keep close to their parents. Putting a foot wrong here could cost them their life. The adults awaiting their turn grow nervous, and this bottleneck gives the dromaeosaurs a chance. ”
The Edmontosaurus herd, arriving for food that comes up during spring, faces an icy river, enlarged and made faster and stronger by the melting ice. The dromaeosaurs aware that some of the hadrosaurs won't survive the river crossing. Seeing the cautious herd held up by the river's icy bank, hesitant on traversing the hazardous river crossing, three dromaeosaurs make their way down the snowy cliff face of the upland forest, rushing at some of the juveniles in the herd, harassing and intimidating them. This, in turn, causes panic to spread through the whole herd, and soon, every member is frantically running and wading through the collapsing ice of the river. In the chaos, some of the juvenile hadrosaurs are left by their parents on the other side of the river.
One mother watches as her calf is dragged away by the currents, and tries to keep up with her offspring in hopes that it would make it. Fortunately, the young hadrosaur manages to climb up the snowy bank of the river, almost slipping off back into the river before successfully hauling itself up to reunite with its parent. Finally, both join the herd as they continue on their journey, leaving the dromaeosaurs on the other side of the raging rapids.
“ The dromaeosaurs seem to have missed their chance. But the river has done their work for them. There are always casualties. It's a feast, and more food than these hunters have had all winter. In the ice world, seasonal opportunity is brief, spring is short, and summer will soon be over. There's a lot to be done before the challenges of winter return. ”
Not everyone is lucky to have survived. The three dromaeosaurs rush down the rocky banks of the river to claim the reward of their combined efforts and the river's unforgiving power, a dead juvenile hadrosaur. The three begin feasting on the body, with one briefly squabbling with another before going back to eating. The segment ends with the hadrosaurs, among them the lucky calf and its mother, traveling onwards alongside the frozen, fragile ice covering the massive river they just crossed.
Trivia[]
Dromaeosaurus is the first animal featured on Prehistoric Planet that was named outside of the actual show, with its identity being confirmed by Dr. Darren Naish, Prehistoric Planet's lead consultant.[DN 1] It was only referred to by the generic term "dromaeosaur" in its sole appearance in the first segment of Ice Worlds.
↑ 5.05.1Synopsis of the Hell Creek (uppermost Cretaceous) dinosaur assemblage
↑ 6.06.1Listed as cf. Dromaeosaurus sp. in "Dinosaur distribution (Late Cretaceous; North America; Texas)." Weishampel, et al. (2004). Page 582.
↑ 7.07.17.2Flaig, Peter P., Stephen T. Hasiotis, and Anthony R. Fiorillo. "A paleopolar dinosaur track site in the Cretaceous (Maastrichtian) Prince Creek Formation of Arctic Alaska: Track characteristics and probable trackmakers." Ichnos 25.2-3 (2018): 208-220.
↑ 8.08.18.2Brown, Caleb Marshall, et al. "Evidence for taphonomic size bias in the Dinosaur Park Formation (Campanian, Alberta), a model Mesozoic terrestrial alluvial‐paralic system." Palaeogeography, palaeoclimatology, palaeoecology 372 (2013): 108-122.
↑Prehistoric Planet Character Designs by Gaëlle Seguillon. The original filename of the Dromaeosaurus image is "gaelle-seguillon-gaelle-seguillon-prehistoric-planet-iceworld-dromaesaurus-female-web.jpg", indicating that the design seen on the show was originally intended to be for the female.
