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True to Life?
‘Raptors of a Feather?

Profile

Species: antirrhopus
Range: Early Cretaceous (Albian ,112-109 MYA) from Montana, Utah, Wyoming, Oklahoma
Size estimate: 10-11 ft length, 160-220 lbs
Discovery: John Ostrom, 1969
Classification: dinosauria, saurischia, therapoda, maniraptora, dromeosauridae

True to Life?

Since no one has ever seen a living dinosaur, and the missing pieces of the fossil record withhold important clues to their appearance, no artistic representation of a dinosaur ever gets it 100% right. On top of that, new discoveries can change our ideas of extinct creatures drastically. So, how close does this sculpture come to what we know of the original animal?

• The Park currently boasts four (well, three and a quarter) different depictions of this culturally, historically, and scientifically important dinosaur. Make sure to check out each of them to draw comparisons and contrasts—it’ll be like a scavenger hunt! In no particular order, and depending on which sculpture’s information you scanned first, they are found in the Rogue’s Gallery in the courtyard (and thus three and a quarter), carved into the east wall of the Stewart Museum just north of its northeast exit, in the middle of the west side of the Park—northeast of the Acrocanthosaurus, and finally on the east side of the river just west of the Diplodocus vs Allosaurus fight scene and north of the Brachiosaurus. Happy hunting! Just be sure Deinonychus isn’t hunting YOU!!
• Behind-the-Scenes: Having multiple models at the Park illustrating the historiography of Deinonychus depictions partly inspired the True to Life? feature.

Rogue’s Gallery wall mount (head only)
• Though lacking a body, this sculpture at least provides the closest to anatomically accurate head shape. Dinosaurs in general and especially small ones have much less bony heads than most mammals or even birds. Their skull bones are delicate and can get smashed and/or distorted easily. In Deinonychus’ case, like many other small dinosaurs, incomplete data has led to numerous similar-yet-not-quite-congruent restorations and artistic depictions. It’s tough to say precisely what it looked like with so many competing hypotheses and speculations. Even so, this take does get the low, but not too low, snout angle at least close. Other Deinonychus heads in the Park either get too round or too narrow and low.
• Unfortunately, it does give the snout a concave kink, harking back to Gregory Paul’s infamous 1988 insistence that Deinonychus had concave nasal bones and thus belonged in the Velociraptor genus. It doesn’t.
• Like the rest of the Rogue’s Gallery, for some reason its ears are missing. Dinosaur ears would look like an oval membrane hugging the back of the skull; lumps which signal the edge of the skull show where the ears should go, but this sculpture only provides a blank stretch of skin in that area. Hear no evil, maybe?
• Two words: cone teeth. Like many of the Park’s carnivores, this sculpt sports only the generic cones that pass for teeth in a general sense. In life and death, Deinonychus’ teeth took on bladelike shapes with serrated edges and a slight recurve that encouraged struggling prey to move towards the throat like a series of ratcheting gears.
• We can forgive this sculpture for lacking feathers since it was produced years before scientists had amassed enough evidence to determine feathers as the default for dromaeosaurs (‘raptors).
• Without some knowledge of its behavior and habits, we cannot determine the look of its eyes. Nocturnal habits or a preference for dim forest habitats might make the slit pupils seen in its fictional Jurassic Park counterparts more plausible (though owls never seem to have opted for slits, and they rank as the ultimate nocturnal avian predators). Round pupils might look a little less dramatic or alien, but scientifically they are a little more plausible.

Stewart wall
• This carving reproduces the original skeletal diagram produced by John Ostrom to illustrate features of the taxon. As such, it has been superseded in some respects by new discoveries, but as a skeletal it nevertheless represents the most coldly accurate depiction of Deinonychus in the Park overall. Keep in mind that as a scientific restoration, it still represents a hypothesis and therefore requires revision if and when new discoveries contradict it. It also depicts some of the only facts about Deinonychus available to us: bones and teeth. Like science in general, it consists of facts held together by the connective tissue of the imagination and constantly tempered by rigorous testing.
• One element of this depiction that the intervening years of new fossil discoveries has overturned is the skull. Dr. Ostrom modeled his reconstruction of the incomplete skull available to him on Allosaurus, one of the best known and most complete examples of theropod skull models available in the late 1960s. As a group, however, dromaeosaurs feature a suite of skull characteristics significantly different from allosauroids. We now have good reason to believe that early dromaeosaurs coexisted with Allosaurus, naturally placing their divergence of lineage and lifestyle farther back in the Jurassic and rendering Allosaurus a poor model for dromaeosaur restoration. Considering how we benefit from an explosion of new discoveries and several hundred more known dinosaur species than Dr. Ostrom had, and which the work of his generation of scientists provided, we can appreciate his choices even while recognizing the need to revise his model into something which better fits the data available to us.
• Some may likewise criticize the posture of the arms in this bas relief as relicts superseded by new discoveries, but these arms correctly portray what we know now about Deinonychus’ arm posture. Unlike any other theropod currently known, the palms of Deinonychus’ hands would turn downward as it bent its elbows; extending its forearms at the elbow would eventually rotate the palms of its hands slightly upward at full extension. Unusual features like these hint at specialized behaviors and ecological roles, though what exactly this range of motion for Deinonychus’ arms and hands remains a mystery for the time being. The bones do not lie, however, so regardless of what led Deinonychus to adopt such unusual joints, that is nevertheless how they work. Art which depicts Deinonychus folding its arms like birds fold their wings does not reflect the reality of the fossils. Other ‘raptors likewise could not fold their forelimbs or wings (as with Microraptor) like birds either, but for different reasons—check out our other ‘raptor species for further explanations of their forelimbs. Suffice it to say that dromaeosaur forelimbs reflect greater diversity than some sources describe—they did not have bird wings even though they share a few forelimb features with their modern bird cousins.
• Unfortunately, this skeletal relief portrays only the front half of the animal. The tail of Deinonychus sports some interesting features in the form of bony rods extending across several vertebrae at a time. Scientists once considered these rods as tail stiffeners, but a couple of relatively recent discoveries—one from Utah, in fact—show that the tail retained some ability to curve. In life, the bone of the rods grew thin enough to bend like a fishing pole, hinting at its possible function. Like the wishbones of modern birds, these rods may have made the tail capable of storing kinetic energy for a second or two before releasing it. Bird wishbones do this to make flapping easier. Dromaeosaur tails may have done this to extend leaps or allow them to reposition their bodies in midair like a cat. A close slo-mo look at footage of basketball players known for their madd hopps sometimes shows them kick their heels up at the top of the arc of their jump: that slight movement sends enough momentum upward to extend their flight a few more inches. Not surprisingly, pterosaurs with long tails likewise boasted bony rods in their tails for likely the same reasons. This feature played such an important role in dromaeosaur behavior that they rewired their muscles from the typical dinosaurian design plan in order to give their tails more freedom of movement at the base. Dinosaurs usually relied on the caudofemoralis longus muscle stretching between the thighbone and along the tail to power their legs backward during strides or jumps, but dromaeosaurs relied more on their drumsticks and thigh muscles. So watch out! ‘raptors always landed on their feet (probably). If you would like to see a dromaeosaur skeleton in the Stewart Museum to rectify this unfortunate omission, contact us!

West end duo
• Some pundits have described these sculptures as quaint relics of a bygone age and woefully inaccurate. They aren’t wrong, but detail-for-detail, these statues don’t get things as wrong as first impressions might suppose. Their tail-dragging posture may produce much of that first impression, especially since Deinonychus illustrations since Ostrom’s description have always portrayed it as more active and alert than the sluggish relicts so popular with the scientific progressivism of yesteryear. Perhaps the artist drew influence from the “old school” when planning their poses, but since these sculptures use a concrete-and-steel construction, engineering needs may also have played a role in the posture choice.
• These ‘raptor’s skull shape might rank as the second best depictions in the Park after the Rogue’s Gallery bust; a real Deinonychus head may have looked a little like a cross between the two.
• Whether these ‘raptors bore lizard lips or not remains unclear. Studies have found that Velociraptor’s face may have grown a sort of half beak, half crocodilian sort of design, but we don’t yet know whether that applies to any other dromaeosaur.
• Yes, Deinonychus’ exceptional arm joints allowed it to point its palms downward, but NOT when its arms fully extended. Unlike humans, its wrist motion seems tied to its elbows, and when extended, its palms would have angled slightly upwards, not down like a zombie. Moreover, theropod shoulders—Deinonychus included this time—could not angle very far forwards With perhaps a few exceptions among the weird megaraptoran dinosaurs, even long-armed theropods proved as helpless as Tyrannosaurus when it came to reaching their mouths with their hands. Instead, they might bend their heads down to meet their hands coming up, but that’s about it. These arms also measure a little on the long side proportionally.
• The following point applies to all the dromaeosaurs of the Park, but I’ll mention it here since Deinonychus is a sort of flagship for the group: yes, ‘raptors walked on two toes while they held their big inner toe claws up away from the ground. Fossil trackway evidence has confirmed this.
• Unfortunately, the tails on these guys are too short and thick. Their curvature, however, may not cross any structural taboos—refer to the entry on the bas relief above for more information on dromaeosaur tails.
• Okay, they’re not feathered. They don’t follow the default pattern for dromaeosaur skin established by the currently available set of fossil evidence. However, they don’t bear scales over most of their bodies either but opt for bare skin instead. I’ve critiqued the bare skin trope evident in many of our sculptures elsewhere, and the chapped sort of wrinkling visible here doesn’t help matters, but one of Deinonychus’ relatives does preserve evidence of bare skin with scales on its feet as shown here. Granted, Santanaraptor, a Brazilian tyrannosauroid, doesn’t come especially close to Deinonychus on the dinosaur family tree, but it may have filled a similar ecological role. So while these sculptures misrepresent Deinonychus’ skin covering, they do inadvertently represent the broad strokes of an actual dinosaur fossil.
• So yeah, oddly accurate in some details, not unlike the nearby Arctodus. But also yeah, they look really weird . . . again, not unlike the nearby Arctodus.
• Behind the Scenes: When first placed in the Park, these sculptures occupied part of the Wayment Amphitheater to the east, menacing the Stegosaurus and its hatchling. Such a brazen anachronism may have resulted from a series of miscommunications about a Russian discovery from the early 1990s. Scientists there reported finding a number of Jurassic taxa including an unidentified stegosaur from Cretaceous rocks. Given how the Cretaceous spans about 14 million years longer than the entire Cenozoic era, but not many people know that offhand (now you do, so go have fun with it at parties and stuff), it’s easy to see how someone might see that and consider a Stegosaurus a contemporary of any other Cretaceous dinosaur. Disentangling the narrative with recent discoveries and a little research, then, we find that the stegosaurs reported from Asia are new taxa—for example, Mongolostegus, NOT Stegosaurus itself—from the earliest Cretaceous, still tens of millions of years older than a taxon limited to the mid-Cretaceous of North America. Further, while Deinonychus would never have menaced Stegosaurus thanks to the intervention of tens of millions of years, some other dromaeosaur may have done so: ‘raptors probably originated in the Middle Jurassic, and we do have some tooth evidence suggesting their presence in Stegosaurus’ stomping grounds, the infamous Morrison Formation. Again, no cigar, but closer than these sculptures have any right to be.

East end trio
• This trio of Deinonychus borrows heavily from Gregory S. Paul’s 1988 book, Predatory Dinosaurs of the World. As a result, they primarily reflect his views on the taxon, views which most scientists did not share and which Paul himself has since rejected. Even more so than the Deinonychus sculptures on the west side of the Park, these statues reflect a very, very particular subset of the zeitgeist that formed them.
• It’s also worth noting that Predatory Dinosaurs of the World contributed to Michael Crichton’s research when he wrote Jurassic Park. Paul’s book argued in about a paragraph’s worth of argumentation that scientists ought to regard Deinonychus as a species of Velociraptor. Though few, if any scientists accepted the synonymy (Paul himself has since rejected it), the Jurassic Park novel does refer to its characters as Velociraptor antirrhopus. As a result, these sculptures essentially portray big, beefy Velociraptors. You may enjoy comparing them with the fictional and realistic Velociraptor sculptures featured on the Lost Trail on the westernmost side of the Park.
• As mentioned in the main sign text, the head presents one of the most readily apparent departures from the fossil evidence. To illustrate one reason most scientists didn’t accept the synonymy presented by Predatory Dinosaurs of the World, it presented an imprecise, truncated, and generalized summary of one opinion founded more on experience than detailed study. Thanks to Jurassic Park, enthusiasts and laypeople alike began to accept Deinonychus as Velociraptor despite the fact that science must stand on the evidence and not the say-so of a single author. The burgeoning popularity of V. antirrhopus may have prompted a rebuttal: ten years after the publication of Paul’s book, dromaeosaur experts Rinchen Barsbold and Halzska Osmolska produced a ten page paper which detailed numerous differences between the skulls of Velociraptor and Deinonychus, justifying their generic separation. Among the key differences: Paul insisted that the nasal bones of Deinonychus followed a depressed curve like Velociraptor’s, but Barsbold, Osmolska, and numerous others found Deinonychus bore straight nasals instead.
• Some credit Paul with predicting that dromaeosaurs had feathers. Again, though some treat Predatory Dinosaurs of the World as a classic of scientific literature, it was never peer reviewed, nor does it detail sufficient evidence to make a scientifically defensible case for its claims. In the case of feathered ‘raptors, Paul’s speculation did foreshadow discoveries which have since made feathers the default assumption for dromaeosaurs, but holes in the reasoning presented in Predatory Dinosaurs of the World limited the veracity of those predictions to the simple presence of feathers. As a result, the illustrations presented in the book and elsewhere during that period did not accurately anticipate other factors like size, type, degree of coverage, or arrangement of the feathers, among others. Moreover, in a larger sense, scientists have considered feathers showing up before birds a distinct possibility since the days of Aldous Huxley and the Victorian period, which is when the first fossil feathers known to science were discovered and described. Many scientists rejected the notion of dinosaurs bearing feathers because they did not consider dinosaurs ancestral to birds due to their apparent lack of a wishbone. We have since found and identified dinosaur wishbones (furculae), but it took some doing because dinosaurs used their furculae for completely different reasons than birds do. In fact, Richard Owen considered birds to be dinosaurs’ closest living relatives when he first coined the term dinosaur, but that’s a story for another time.

Back to feathers: acceptance of Paul’s speculation, therefore, came slowly, mainly following patterns revealed by direct evidence discovered later, and naturally it remains conditional to this day and beyond because of its incompleteness. For many years afterward during the Dinosaur Renaissance, scaly dromaeosaur depictions coexisted with a host of feathered ones depicting wildly varying opinions on what a feathered ‘raptor would look like. They all turned out to be wrong. We now know that true birdlike feathers originated in a common ancestor of dromaeosaurs and birds, that both birds and dromaeosaurs bear the same arrangement of feathers on their forelimbs into primaries and secondaries, etc., and that they played an important role in dromaeosaur behavior even though we don’t know what those behaviors were. We still do not know if any dromaeosaurs bore, for example, elaborate arrangements of tail feathers or extendable crests like a cockatoo, let alone whether birdlike contour feathers constituted a norm for non-volant (ground-based) ‘raptors or if they usually bore a more down-like fluff.

These sculptures bear a neutral rough skin texture, skirting many of those issues and accurately reflecting the ambiguity of our current knowledge. The rough texture uniformly covers the body, unlike the hybrid scales/feathers favored by some artists of the period, a detail which recent evidence bears out: dinosaurs which bore feathers do not seem to have learned how to grow scales on their shins like modern birds do. Once they went feathered, they seem to have gone feathered all the way. These statues do lack the winglike fans of feathers on the forearms which some scientists prefer to call “pennebrachia” in order to distinguish them from bird wings, which are radically different in terms of skeletal structure. Nobody seems to have predicted dinosaurs close to birds would bear winglike appendages either, despite Archaeopteryx clearly bearing birdlike wings, so speculation clearly has a limited predictive value, which many other examples among dinosaur art alone bears out. We don’t know if Deinonychus’ unusual arm posture affected how its pennebrachial fan may or may not have grown, though, so unlike other ‘raptors, there is a possibility that its arms would have appeared as skinny as shown here, and maybe not even birdlike at all. As for other speculative feathery appendages like tail fans or head crests, check out our other ‘raptor sculptures’ supplemental signs for more info on their likelihood. Suffice it to say here that Deinonychus fossils preserve precious little information on their skin, same as most dinosaurs, so speculating on them is just taking shots in the dark.
• Speaking of the arms, the ones on this sculpture seem to take some cues from the standard theropod model, not Deinonychus itself. With its elbows bent, a Deinonychus’ palm should start angling toward the ground, contrary to the inward-facing medial orientation typical of other theropods. The individual clawing away at the poor Tenontosaurus gets things a little closer to correct, but not exactly.
• The posture and overall proportions of the body in these sculptures matches the fossils well. Deinonychus’ species name refers to the counterbalancing function of the tail, which the westernmost sculpture illustrates particularly nicely. To raise its torso while maintaining its balance on the run, Deinonychus may well have needed to raise its tail as well. Even if it did not engage in such behavior, this kind of speculation at least provides some nice characterization that breathes some life into the statue.

‘Raptors of a Feather?

After Jurassic Park catapulted Velociraptor into pop stardom, many among the general public tend to conflate all small meat-eating dinosaurs with the ‘raptor group (technically they’re known as the dromaeosaurs, which means “emu lizards,” and belong to a larger group called maniraptors, which means “grabby hands”). However, ‘raptors show a bunch of features that set them apart from other small carnivorous dinosaurs like Coelophysis or Ornitholestes. Does calling small theropods in general “‘raptors” of a feather really stick together? For answers to that and to get a better “grip” on Deinonychus itself, check out these cool tidbits:

• What’s the real difference between maniraptors and other small theropods? The main difference lies in the crescent moon-shaped bone of the wrist that gives maniraptors more flexibility with their hands. Dromaeosaurs had the distinctive toe claws and bony rods in their tails that give this animal its name, which means “counterbalanced terror claw.”
• True ‘raptors also lived during the late Jurassic through the Cretaceous. Deinonychus itself lived in the early Cretaceous along with Acrocanthosaurus and Tenontosaurus; Coelophysis and Ornitholestes both lived much earlier than Deinonychus.
• Fossil impressions of some dromaeosaurs show that they bore true feathers which closely resemble the basic structure of those found on modern birds. Small theropods as a group bore a much wider variety of skin coverings ranging from scales to fuzz (scientists call this stuff monofilamentous integument, but it superficially resembles hair) to feathers ranging from downy to birdlike, along with at least one example (Santanaraptor: see below) apparently going with mostly naked skin. Considering how complex feathers are, we should expect the fossil record to produce a wide variety of skin coverings like this, representing so-called false starts, evolutionary experiments, or spinoffs that left no modern analogs. Indeed, recent finds from China show that some dinosaurs bore extinct feather types not found on any modern bird. For example, a group given the tongue-twisting name of scansoriopterigidae (say it five times fast—you know you want to!) bore tail feathers shaped like paintbrushes.
• The most basal ‘raptors currently known—those which most closely resemble the hypothetical ancestor of the whole group, like Microraptor—developed the ability to glide, an ability shared only with birds and possibly the scansoriopterigids. In addition, contrary to early descriptions of their big toe claws as “killing claws” used to slash prey, recent studies have found that dromaeosaurs primarily used them for climbing. Given how these two features correlate with one another, many scientists now hypothesize that tree climbing may have played an important role in ‘raptor behavior and ecology despite their evident ground-dwelling habits, much like this behavior does for modern leopards, jaguars, or cougars. One study even goes so far as to suggest that juvenile Deinonychus may have retained some degree of their ancestral gliding ability, though it didn’t seriously test this speculation. It remains to be seen whether baby Deinonychus bore feathers at all, or if those feathers were downy, or if they were stiff enough to bear the animal’s weight. Some studies have found that dinosaur feathers, even in adults, consisted of alpha keratin; birds developed stiffer beta keratin (not to be confused with beta kerotene) to deal with the rigors of flight and which they generally adopt when fully fledged, as opposed to the alpha-keratin-based feathers many of them grow as hatchlings. Scientists can’t yet say how widespread a tree-dwelling habit might have been among ‘raptors, and if they had it, what might have driven them to largely abandon flight, but if they never developed beta keratin like modern birds, it would have made them second best to birds in the race to conquer the skies (which pterosaurs had already conquered by that point in the first place).
• Another problem for the gliding baby Deinonychus model: at least as adults, the species’ forelimbs feature unusual joints that may have reoriented the feathers on its forelimbs (if it had any large enough) in ways that made them unsuitable as airfoils. A distinct lack of data makes it impossible to reconcile competing reconstructions, so it’s best at this point to take this speculation with a healthy degree of skepticism and watch for further discoveries.
• One point that supports at least an occasional tree-dwelling habit for Deinonychus occurs in its feet: they both retract far enough to wrap around branches thick enough to bear its weight; they also angle towards one another when they retract. Despite lacking an opposing digit like many perching birds, these features make a tree-perching Deinonychus plausible.
• Delving into details like this illustrates how small differences in body shape can lead to a wide variety of survival strategies and abilities even among closely-related groups. Though the skeletons of small carnivorous dinosaurs may all look alike in a general sense, in life these dinosaurs likely employed a staggering array of different behaviors and inhabited diverse habitats. If we could see them alive, we might chuckle at any notion of calling all of them ‘raptors!
• Bonus: Up until the discovery of Utahraptor in 1993, Deinonychus weighed in as the real bruiser of the raptor clan at up to 11 feet and a whopping 160-220 pounds. Since the discoveries of giant raptors like Utahraptor, Dakotaraptor, Austroraptor, and Achillobator, it fits into the mid-sized range.
• ‘Nuther bonus: Evidence of Deinonychus has been discovered in Utah, although it mainly consists of scattered bone fragments and teeth, not any major skeletal remains so far.