Converting prehistoric animals

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Monster Junkie
BOZ--Is this thread working differently than the other conversion threads? Are we converting multiple monsters at once?

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Inventor of Super-Toast
Boz, just so you know, Apatosaurus is in the .doc I sent you. Just another reminder.

RE Shade: There really doesn't seem to be too much of a pattern to the conversion's timing (1 vs multiple). I think that the thread will settle soon enough, though.

Demiurge out.


Creature Cataloguer
First of all, stats from the 1E monster manual (I know there were some 2E stats, I’ll get those later if they’re notably different):

Apatosaurus (Brontosaurus)
MOVE: 6”
% IN LAIR: Nil
SIZE: L (70’ long)
Attack/Defense Modes: Nil

The thunder-lizard is a 40 ton plant-eater found near marshes and lakes. The creature spends much of his time in shallow water to support his bulk. It moves to deep water to avoid carnivores. Apatosaurus ignores small things, but it is prone to step on anything in its way (doing 4-40 points of damage).

Hey, I thought I heard somewhere that that “support bulk in water” thing was so much BS, because it uses its tail for balance. Feel free to inject as much current scientific theory into this as you like, but let’s not get too bogged down in science – it’s just a game, after all. ;)

And here is demiurge’s version:

Dinosaur, Apatosaurus (Brontosaurus)
Colossal Animal
Hit Dice: 20d8+166 (256 hp)
Initiative: -1
Speed: 20ft (4 squares)
Armor Class: 12 (-8 size, +10 natural), touch 2, flat-footed 12
Base Attack/Grapple: +15/+43
Attack: Tail slam +19 melee (3d8+18 plus thunderous snap)
Full Attack: Tail slam +19 melee (3d8+18 plus thunderous snap)
Space/Reach: 60ft/40ft
Special Attacks: Thunderous snap, trample 6d8+18
Special Qualities: Low-light vision, scent
Saves: Fort +23, Ref +12, Will +8
Abilities: Str 34, Dex 11, Con 27, Int 1, Wis 14, Cha 10
Skills: Listen +12, Spot +19
Feats: Alertness, Diehard, Endurance, Great Fortitude, Toughness (x2)
Environment: Warm forests, plains and hills
Organization: Solitary or pair
Challenge Rating: 10
Treasure: None
Alignment: Always neutral
Advancement: 21-60 HD (Colossal)
Level Advancement: -

This massive quadruped has a very long neck and tail, a horse-like head, a wrinkled, elephantine hide and a small row of colorful spines lining its back, like those of an iguana.

The apatosaurs are the most common species of sauropod, the unbelievably large long-necked dinosaurs.

Although they vary in size, most apatosaurs are between 70 and 80 feet in length. They are solitary, unlike their relatives Diplodocus and Seismosaurus. They feed on low-lying foliage with their long necks, and can rear up on their hind legs and tail to reach the tops of trees.

Apatosaurs are so large that they have few natural enemies, besides allosaurs and megalosaurs hunting in packs. If directly threatened, they lash out with their powerful tails, but are capable of merely walking over most opponents.

Thunderous Snap (Ex): Although they are ponderous, an apatosaurus’ whip-like tail can move faster than sound. Any creature struck by an apatosaurus’ tail slam must make a Fortitude save (DC 28) or be stunned for 1d4 rounds and deafened for 1d4 minutes. On a successful save, the creature is merely deafened for 1d4 minutes. The save DC is Constitution based.

Trample (Ex): An apatosaurus can literally run over any creatures in its way that are of Gargantuan or smaller size. Creatures trampled must make a Reflex save (DC 32 half) or take 6d8+18 damage. The save DC is Strength based.


Inventor of Super-Toast
Just to point out that I'm not totally insane, the thunderous snap is a not-terribly-uncommon scientific hypothesis, as various computer dynamics analysis have suggested that an apatosaur or similar dinosaur could move its whip-like tail at supersonic speed.

Plus it's a cool ability for a game-dino to have.
Demiurge out.


First Post
I think base size should be gargantuan. If you look at the colossal dragon on page 150 of the PH, he dwarfs the human figure in a way that I don't think even a 40 ton dinosaur could match. According to the Dragonomicon, a colossal dragon is around 640 tons.

Also, 20 HD seems slightly low-ball to me, what with this creature coming in at 3 or 4 times the weight of a 16 HD trike. Even the measly 6 ton Tyannosaurus has 18 HD. I realize HD isn't all about relative weight, but still...

As for ability scores and AC, I'd say offhand that Urge's look to be in the range of what's reasonable.


Inventor of Super-Toast
I based the 20 HD figure off of the seismosaurus, the largest and strongest of the sauropods. According to the MMII, a seismosaurus has 32 HD, and both the diplodocus and brachiosaurus are larger/more powerful than an apatosaur. Also, tonnage wasn't my comparison so much as length. An apatosaur is certainly over 64 feet in length. But by weight, hmm...

Of course, if you were going by weight, the seismosaurus would be disqualified from the Colossal category (where it is), because the heaviest dinosaur was the 100 ton argentinosaurus (The MM posts Colossal at 125+ tons).

Demiurge out.

Wippit Guud

First Post
I second the vote for starting at gargantuan, keeps it more 'realistic' when comparing it to a dragon of similar strength (all but gold in the 34-35 strength cat are G). Hit dice seem about right compared to the closest thing we have to a similar creature in 3.5, triceratops (coming in at 16 to start).

But, beyond reducing the size by 1 (and remember, advancement will kick it up anyways), looks good.
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Creature Cataloguer
thanks for the links; i'll have to check them out at home (stupid work filters).

some comments:

I could see going Gargantuan – most of the beast’s length is neck and tail. And the size charts do not need to be followed verbatim: the are not minimums and maximums, rather they are strong suggestions of such.

For hit dice, yes I say 20 is too low. The original had 30 right?

Thunderous snap – hey it’s unique, I’ll keep it. :)

Wippit Guud

First Post
BOZ said:
For hit dice, yes I say 20 is too low. The original had 30 right?
Prblem is, there's several dinosaurs that are larger in size... unless you want 80HD seismosaurs in the future :)


Inventor of Super-Toast
BOZ said:
For hit dice, yes I say 20 is too low. The original had 30 right?

Yes, but the seismosaurus (the biggest and strongest of the sauropods) has 32 in MMII. So increasing them back to their original 1e number isn't the best way to go. An average of around 23-25 would probably work (since the diplodocus and brachiosaurus are larger aka more HD than the apatosaurus).

Demiurge out.


First Post
A persistent theme here is that progression is always going to make hash out of any attempt to portray these beasts realistically. I wouldn't sweat it too much.

Progression on the Seismosaurus is: 33-64 (Colossal). So Seismo is capped at double his base HD, not the usual 3X. Weird like a beard, but I checked the update booklet and this hasn't changed.

Even if we go the same route with Apatosaurus, then Demiurge's conversion still caps out at 40HD, which overlaps Seismo by quite a bit. Personally, I wouldn't worry about it, since its an unavoidable quirk of progression, and since HD take into account overall fighting ability as well as mass.

Even if we do Brachiosaurus later, I wouldn't worry about having to put him within a few HD of Seismosaurus. Brach wasn't completely out of Seismo's league in terms of mass anyway.

So personally, I wouldn't worry about bringing Apatosaurus in say 2 to 4 HD larger than Urge's 20D. But I can see the argument both ways.

As for the hypersonic tail snap, I like it too. It will make Apatosaurus something more than just a shrimpy seismo.
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Creature Cataloguer
size =/= HD either. ;)

20, IMO, is way too little. 30 might be too much though... i'll have to get a moment to compare what the other dinos' HDs were in previous editions, two what they are now to make a real determination here.


Creature Cataloguer
if i don't come up with a better answer in a day or two, then 25 it is. :)


Creature Cataloguer
Comparing 1E MM dino Hit Dice to 3.5 MM, we get these:

Elasmosaurus: 15 / 10
Triceratops: 16 / 16
Tyrannosaurus: 18 / 18

And 1E MM2:

Deionychus: 4 / 4

So, there was some decrease present, but not a whole lot. Therefore, I don’t want to do a whole lot of reduction with the other dinos. I will support sticking with the OD&D version’s 26 HD though (see below). :)

2E stats:

DIET: Herbivore

THAC0: 5
SPECIAL ATTACKS: Crush (4d10 or 5d10)
SIZE: G (70’ long)
MORALE: Steady (12)
XP VALUE: 22,000

Brontosaurus (apatosaurus)

The “thunder lizard” is a 40-ton plant-eater found near marshes and takes. The creature spends much of its time in shallow water to support its bulk (and because food is plentiful there), but never moves to deep water because the increase in pressure makes it impossible for the tremendous dinosaur to breathe.

Apatosaurus ignores small things, but it is prone to step on anything in its way (causing 4d10 points of damage).

The body of the brontosaur is 65 feet long, but the tiny head is less than two feet of that-a man with the same dimensions would stand six feet tall, but have a head only two inches long! The brontosaurus tips the scale at a mere 30 tons, rather light for a sauropod.

The front legs of the brontosaurus are shorter than those in the rear, like all sauropods except the brachiosaurus. This configuration enables sauropods to get up on their back feet to reach the topmost leaves of a tree. The brontosaurus. could also use this ability to- fight against its principal enemy, the allosaurus. The thunder lizard could tilt itself up on its long back legs, then come crashing down onto its enemy to inflict 5d10 points of damage.

The brontosaurus's tail can be whipped, causing 1d6 points of damage to any foe close enough.


Armor Class: 5
Hit Dice: 26
Move: 60' (20')
Attacks: 1 bite/1 tail
Damage: 2-12/3-18
No. Appearing: 0 (1-3)
Save As: Fighter: 13
Morale: 8
Treasure Type: Nil
Alignment: Neutral

A brontosaurus is one of the largest of all dinosaurs. It has a massive body with a small head, long neck, and a strong, tapering tail. The creature is 65' to 75' long and weighs more than 30 tons.

A brontosaurus is so heavy that it needs to spend most of its time in water, so that the water helps support its weight. If only its neck shows above water, the brontosaurus may be mistaken for a plesiosaur or sea serpent. This dinosaur eats plants, and can only be found in deep marshes or on the edge of swamps.
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Creature Cataloguer
hmm, and did we agree to make them Gargantuan also? or were we going to stick with Colossal?

he gets more skills & feats with 6 more HD, as well as the other usuall accompanying changes.

let me make a few comparisons between demiurge's suggested conversion and the original bronto D&D sources. that's really the bulk of what we'll be doing in this thread, at least for the ones that he or someone else has personally converted.

All D&D versions of the bronto had AC 5. I was thinking we would need to up its natural armor, but then a size decrease will increase the AC overall of course.

The AD&D version had them appearing in groups of 1-6, while the OD&D version had them in groups of 1-3. does science speak of these things moving around in small herds or should we stick with “Solitary or pair”?

Regular physical attacks is another thing that varies. The OD&D bronto had two attacks, clearly spelled out: 1 bite (2-12 damage) and 1 tail (3-18). The 1E bronto also had them listed as doing 3-18 damage, but does not suggest what sort of attack that is. The 2E bronto also has the 3-18 attack, but adds a 1-6 damage attack, although this attack is identified as a tail slap. Ahhhh! :)

The weight for this animal is listed alternatively as 30 tons or 40 tons.

There is also a stamping attack listed in both AD&D versions (which does not seems to require that the beast be running – it simply steps on smaller creatures): 1E has 4-40 points of damage, and 2E adds an intentional rearing back to crush opponents that is 5-50 damage.

Also, all three sources mention finding bronto most commonly in a marsh or shallow aquatic environment. This could be a holdover from the “needs to be in water to support its weight” theory, but I think scientists to agree that while it didn’t need to be in water, it often was anyway.

Other than those items, I think it’s just fine as is. Now of course, we don’t have to actually use all or even any of this stuff – it’s just something to think about. Just ask Shade – I’m always this critical. ;) of course, I expect a return favor…
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Creature Cataloguer
to have a good look at the "competition", here is the text of the dinos that mortis posted links to.

Mortis said:
Hi Guys,

A 3e version of the Brontosaurus can be found here:

voila (this is a conversion of the OD&D bronto, as is the one below):
by Trevor Mellis
Type and Size: Gargantuan beast
Hit Dice: 26d10+182 (364 hp)
Initiative: +1
Speed: 20'
AC: 11 (+4 natural, -4 size, +1 Dex.)
Attacks: 1 bite +31 melee, 1 tail +27 melee
Damage: 2d8 +12 bite, 1d8 +12 tail
Face/Reach: 30' x 30' / 15'
Special Attacks: Trample, capsize
Special Qualities: Scent, immunities
Saves: Fort +22 Ref +15 Will +8
Abilities: Str. 35, Dex. 11, Con. 25, Int. 1, Wis. 10, Cha. 9
Skills: Listen +6, Spot +6
Feats: None

Climate/Terrain: Prehistoric Aquatic
Organisation: Solitary (1) or group (1-3)
Challenge Rating: 11
Treasure: None
Alignment: Neutral
Advancement: -

The brontosaurus is one of the largest of all dinosaurs. It has a long, tapering tail and a massive body that supports a long neck and small head. The creature is 65-75 feet long and weighs more than 30 tons.

A brontosaurus is so heavy that it needs to spend most of its time in water, so that the water helps support its weight. If only its neck shows above water, the brontosaurus may be mistaken for a plesiosaurus, elasmosaurus, or a sea serpent. This dinosaur eats plants, and can only be found in deep marshes or on the edges of swamps.

Trample (Ex): A brontosaurus can trample Large-sized or smaller creatures for 2d8+12 points of damage if fighting on solid ground or in shallow water. Opponents who do not make attacks of opportunity against the brontosaurus may attempt a Reflex save (DC 20) for half damage.

Capsize (Ex): A submerged brontosaurus that surfaces under a boat or ship less than 20 feet long capsizes the vessel 95% of the time. It has a 50% chance to capsize a vessel from 20 to 30 feet long, and a 20% chance to capsize a vessel 30 to 60 feet long.

Immunities: A brontosaurus is immune to all disease and poisons that do not cause damage.

other dinosaurs may be found on this page under 'd':

thanks, we'll keep that in mind. :)

couldn't get the formatting right to post it, but here's a more specific link:

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