I'm currently designing an mesothermic reptilian sapiens for my world, that have evolved from a deinonychus-type of dinosaur and developed flexible hands with opposable thumbs, but still possessing arms that are shorter and weaker than human arms.

I imagine them to be potentially very quick and agile in battle. Able to jump into attack with spears, sickle claws and even tail and jaw. They are also intelligent and creative, and possesses certain magical capacities as well.

But being mesothermic, I don't expect them to have as much endurance as humans. Don't think they would be at advantage pushing against shield walls for hours. And due to their shorter arms I don't think they are able to be that efficient with bows, javelins or slings.

They have also failed to domesticate any animal that can be used in battle, though they may have access to slave soldiers.

I can easily visualize such reptile warriors defeating human warriors in warfare on a tribal level. But when it comes to organized armies, imagine for example facing an army of phalanxes, heavy cavalry and archers.

Could my reptiles then stand a chance in open battle? How? They are crafty enough to employ whatever solutions that exist in an antique context.

  • $\begingroup$ I think we need additional information about your reptilians to provide a useful answer. How large are they? How much do they weigh? How FAST are they? What kind of terrain are they fighting in? Are they attacking or defending (or both)? Certainly they wouldn't be using anything that developed from thrown weapons for humans (spears, bows, slings). Those wouldn't be useful for them and never would have been developed. You have to start by thinking of what tools would help them be better, more successful HUNTERS, and develop from there. That's how humans did it. $\endgroup$ Jul 16, 2019 at 19:51
  • $\begingroup$ Mesothermic army would not be able to push far away from the tropics. The winter would kill it more certainly than humans. $\endgroup$
    – Alexander
    Jul 16, 2019 at 19:58
  • $\begingroup$ How advanced are the deinonychus-like creatures? Do they have the wheel language, agriculture, the societal concept of kingdoms of other large governments? Should we assume they are technologically and socially similar to humans $\endgroup$ Jul 18, 2019 at 17:26

7 Answers 7


In open battle, yes

And the answer takes two vital components - speed and strength. Your idea of weapons for these deinos revolve around human ones. But that's not the correct approach, it's talons. Large, wicked sharp talons that the deinos have on their feet which gives them better reach. They would attack humans by leaping in the air and landing on them, savagely carving through the lines of humans. To do this, the deinos would need to be adjusted a bit by evolution to have more ostrich-like speed, but essentially what you'd turn them into is cavalry-turned-shock-troopers once they hit enemy lines. They'd crash trough anything short of a shieldwall backed by spears.

Which is were the problems start. See, these things are cavalry. So the best counter is just a spearwall. Nothing too fancy. Any human commander would just order his troops to deploy spears and impale the charging deinos. Archery would work as well, up to a point, at any rate. Gambeson is good enough to stop a few arrows, and deinos have built-in scales, so they can take one or two volleys of arrows. Javelins are a bit tougher, but manageable.

Now, this is were the counter-strategy comes into play. If the deinos would lose a head-on attack, then they don't need to bother with one. A deino with ostrich like speed can run up to 40 mph, which means that a massed deino army has one of the most dangerous abilities at their disposal - encirclement. Normally, it takes some serious tactical acumen, but I don't see why an army of fast knights can't simply pull it off using speed. And when it works, it works. Overall numerical disadvantages stop being a problem, spears become hard after the first deino charge because you can pressure the enemy too close together, and enemy morale plummets.

Unfortunately, this won't work if the enemy is say, using natural formations to their advantages, defending forts, or fighting in caves. And if you're fighting, say, the Golden Horde of the Mongols, you're dead because cavalry archers are OP in ancient combat.


As has been stated already, these creatures weapons and strategies would build upon their physiology.

Those tails could power slings, while accuracy is hard to judge since its a matter of eye-tail coordination, in mass they could be quite dangerous.

Their basic shape would engender the use of the atlatl-like tools, held in their jaws. They could then charge the enemy and at the proper moment, curling their necks and torsos and hips forward, throw heavy darts and javelins.

They could employ hand-held crossbows that they cock with their powerful legs. And, since they, as has been noted, essentially cavalry they could fight as dragoons -- charging the enemy discharging crossbows and running away.

I would think that their armored troopers would have heavily armored undersides so they could run at enemy lines and leap into their midst where their powerful hind legs would give them a great advantage in hand-to-claw combat.

Lastly, they might attach wicked scythe-like weapons to the tips of their tails and yield them like cavalry sabers when facing lightly armored troops like archers and muleskinners handling the supply train.

And, these guys would probably eat what they kill so their logistical requirements would greatly favor them over humans.


All the fossil evidence we have indicates that dinosaurs were the precursor species to modern birds, which are most certainly homeothermic. So, we can presume that this mesothermy is such that the dinos need not bask in the sun to maintain body temperature.

Mesothermy has nothing to do with endurance. In fact, the relationship may actually be inverted: the dinos with their lower basal metabolisms for a given body mass than placental mammals (much as marsupial mammals have) would use less energy for the basic processes of life, and activity would generate body heat and raised body temperatures which they would be better able to tolerate despite potentially worse thermoregulatory capability than humans.

As a side note, there is practically no creature on earth that is as good at getting rid of excess body heat as humans... but getting rid of excess heat is not the only way to cope with body heat, the other way is to simply tolerate it, and continue to function despite an increased body temperature. The nature of thermodynamics is that the higher the difference in temperature between two environments, the faster heat will be radiated away from the hotter object. So, the dinos body temperatures may vary by several degrees during exertion, but unlike mammals, they can simply put up with it.

A dromaeosaur descendant would have a largely horizontal spine, much like birds which also are thought to have descended from dromaeosaurs, though the possibility certainly exists for them to rotate their hips so that they are standing more upright.

The dromaeosaur body plan includes legs with muscular thighs, slender calves, and a digitigrade posture with extended foot bones, making them a cursorial species. Humans are the fastest of the apes in bipedal locomotion (though apes which move quadrupedally may be faster), and can run at up to 37 kph or so. However, humans' relatively short foot and bulky calf muscles do not allow as efficient or as rapid running as the dromaeosaur body plan. While ostriches can run at up to 80 kph, I would expect that a dromaeosaur such as the OP's dinos would be able to run at around 60 kph or so, and could conceivably leap two or more metres upwards and perhaps up to ten metres laterally.

While humans are effectively unarmoured and have no claws or fangs, medieval humans such as the OP mentions are able to supplement their meagre natural weapons and armor with manufactured weapons and armor. On the other hand, the dinos, being carnivorous predatory beings, would have tough skin overlaid by feathers, as well as long claws on the fingers and a particularly large claw on each foot. Additionally, the OP has said that dinos have a humanlike ability to make their own technological innovations. This could include their own armour and enhanced weapons such as razor sharp claw sheaths.

Given a dino's long, narrow body plan and well-made metal armour, I would expect that arrows and other thrusting weapons would be more likely to deflect from their armour than is the case with a tall, broad human figure. This, combined with dinos' great mobility, would render the mainstay of late medieval military armament - pike and shot - far less effective than it is against humans. Dinos could reasonably expect arrows or spears to deflect from their armour, and combined with their mobility, they could either throw all but the most disciplined phalanx into disarray simply by flanking, and if the phalanx sacrificed its own mobility and formed a circle, the dinos could still duck under or leap over the spears and once inside the range of the spears, their enhanced natural weapons would quickly break the phalanx.

A unit of sword wielding humans would stand a better chance against the dinos than pike and shot, as swords are inherently more maneuverable weapons.

Human cavalry would have speed approaching that of the dinos, but lower maneuverability.

The main advantage that the dinos have is that they have intelligence comparable to that of humans. Combined with their superior natural weapons, they could maneuver humans into situations where the dinos advantages could be exploited to the fullest.


The effectiveness of our dinos directly correlates with a tactical acumen. But before we look at the best tactics we should look at how to arm them.

Because of their physiological make-up, they are pretty much cavalry without any further need for anything but a lance. Due to being armed with natural claws, additional hand to hand weapons are not needed, making them extremely light cavalry. Their scales serve as natural armor, probably sturdy enough to be considered equivalent with chainmail or light plate. Adding additional armour, probably from skin or leather, what's turn our light cavalry dinos into heavy armoured light cavalry.

If these deinonychus mastered domestication of other reptiles, then they could field auxilia comprised of Dinosaurs riding on bigger Dinosaurs. These would serve as linebreaker if these heavier dinosaurs might be ankylosaurus or very large vegetarian dinosaurs like brontosaurus.

Due to their speed they can employ fast encirclement tactics and swift charges into the flanks of the humans. Another tactic they can easily employ is skirmishing, fast assaults and immediately retreating to break formations. With their smaller frame than humans and a natural camouflage coloration of their scales, they also make adapt ambushers.


I see 4 issues

Packing problem (why tails are a problem in close order combat) Human formations can be very dense. In a phalanx, troops can be placed less than a foot behind the line in front of them. They can still effectively use their spears to strike. They can support each other and bring a large number of weapons to bear.

Raptors have these long tails that stick out behind them several feet, in all raptors were 11 ft long. If a raptor turns its body the tail swings side to side further increasing the amount of space to the side that needs to be set aside for it. Basically a raptor takes up as much space as 2 horses but is far lighter and weaker. This says the closest raptors could fight and still be effective is in a tight line followed by another line more than a yard behind.

The lack of density reduces the power of a charge (mass matters) A 1,540 horse with 200 -300 lbs of armored knight hits a spear wall much harder than a 200 lbs raptor.

Also a charge from a 9-11ft 1/2 ton tall knight + horse is much more intimidating than a charge from a 3ft raptor that is only 200lbs

Reach In a phalanx with 7 - 15 foot spears the first 3-5 rows would be able to engage the raptor in front of them. Only the front line of raptors would be able to hit the humans, and only after fighting through being stabbed-by spears for 7 - 15 feet.

Shields and armor Arms let you use shields which are a great defense, they are easier to make than armor and can cover more of the body, raptors would have to rely on armor only.

These raptors have a lot more surface area then humans (11 feet long x3 ft high vs 6ft high x8 inches deep) which means armoring them well will be very heavy and likely impractical.

Range It seems like the raptors would have trouble building effective ranged weapons. Combined with their lack of armor and large targets would make them vulnerable to range attack. Which means they have to attack aggressively.

Conclusions Raptors would be effective as light cavalry their walking pace is estimated to be 6mph x2 a humans, but there low reach, low mass, low armor and inability to form tight formations would reduce their effectiveness as shock/heavy cavalry or any kind of infantry.


Easily, by working together more effectively. An army of 100,000 D-men will slaughter 5,000 humans. By having superior organisation and, crucially, not always fighting among themselves while sowing discord among their human foes, the D-men can overcome any minor physiological disadvantage they might have.

Human are, as Dunbar suggests best working in groups of 150. If D-men have a clan, tribe or even species-wide loyalty so that they can easily work together in much larger units, then the humans are likely to be completely outmatched. Humanity has always consisted of badly-coordinated warring groups. Imaginean empire consisting of an entire race of beings, all working together for the common cause. They could field armies much larger than their divided human neighbours.

Nobody says the Romans won because they were bigger and stronger or physically superior to their foes, just better organised.

Secondly, the moral is to the physical as three to one, as Boney once quipped> Being who know no fear, and whose ferocity is greater than human, who cannot be broken by heavy casualties or impossible odds, will be practically unbeatable whatever their physical limitations. They may simply terrify the hell out of any humans who try to oppose them, phalanxes scattering as their approach.

Thirdly, if they are built differently to use, there will be places they work better. It's also a matter or choosing your terrain. Are D-men better adapted to marshes, or deep forest, or rocky slopes than humans? if so, that's where you fight your battles. Are they more effective in the dark with their own peculiar senses? How amphibious are they?

Fourthly, amateurs study strategy, professionals study logistics. What key advantages do D-men have when it comes to keeping an army supplied in the field? How easily can they live off the land?

Finally: breeding and maturation. If they lay 100 eggs at a time like turtles, and come to maturity in a few years, then they can absorb massive casualties and keep coming back stronger, while their human opponents get rapidly worn down.

In summary: look beyond simple physiology. That's not what soldiering is about.


On an open field they'd likely get beaten no matter what. Their bones aren't as dense as ours. Best chance of success attacking even a small human military unit would be in forest or alpine terrain, using hit-and-run tactics to either shield themselves or knock humans to their deaths

  • $\begingroup$ OP's post specifically said they DO have disposable thumbs, and I'm not sure why you're assuming their bones wouldn't be as dense as ours. $\endgroup$ Jul 16, 2019 at 19:48
  • $\begingroup$ I missed that, thanks for reminding me. These dinos are on the same evolutionary branch that eventually leads to birds IIRC, so it's reasonable to assume they've at least started to evolve less dense bone structures $\endgroup$
    – Cygnus X-1
    Jul 16, 2019 at 19:52
  • $\begingroup$ @Cygnus X-1 that isn't really how evolution works. The evolutionary branch that included deinonychus also included the ancestors of modern birds,. But that doesn't mean that the whole branch was evolving toward bird-like structures. Consider that if we go back far enough, there will be a branch of vertebrates that includes the ancestors of both birds and tortoises - but that doesn't mean the species within that branch were evolving towards either feathers or thick shells. $\endgroup$
    – Penguino
    Jul 17, 2019 at 1:03
  • $\begingroup$ Low density bones are an adaptation to flight. I don't recall the OP mentioning that these dinos fly. $\endgroup$
    – Monty Wild
    Jul 17, 2019 at 1:04

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