#and I love critters and the wackiness of biology

[thenecropolix]

@sketch-pencilpoint @/notsozenzeneth [Cracks Knuckles] you two gave me an inch and now I'm going a mile

OK so off the bat when I started thinking "what would a train look like if it was a biological organism" I turned to the obvious that was crustaceans, with lobsters in particular what with their multiple legs (in place of wheels), armored bodies, and the way said legs look when they move

I wanted to keep it as realistic as possible, so instead of mammals, I immediately thought of these guys, which then quickly diverted me to insects, specifically millipedes

So we have a general basis for how a biological engine should look, but now comes the issues of wheels; while we have animals that roll their entire body as a form of locomotion (e.g. armadillo) or roll things (e.g. dung beetle), we have no critter that could be said to have wheels in place of legs in the taxonomic domain eukarya. Ergo, I decided to take a page out of Nintendo's book and turn towards making train wheels into skin patterns that would go on the train's feet.

Enter the humble caterpillar

Barring the first couple set of legs, you'll notice the "feet" of a caterpillar are rather round; that's because they're more like little suction cups that help them stick to the surface of things; what I'm getting at is that train "wheels" would instead be more like these suction cup feet that are patterned in such a way that resemble said wheels.

I want to quickly give a shout out to @theflyingkipper for this next point as their monster engine series introduced to me the concept of turning the funnel of trains into blowholes that release steam. I thought it was a very clever design, but I realize it could be taken a step further if we consider the funnel to be a horn; more specifically, I thought about the parasaurolophus

A thing to make note is that these guys' iconic horns were thought to act as an amplifier for their calls; I figured the same could be applied to trains, boiling down to 2 possibilities:

The blowhole is placed either in front of or in back of the horn, thus creating the illusion of a steam-blowing funnel

The funnel itself has the nostrils on the end like a trunk shaped horn, thus housing another airway aside from the mouth where steam is released

This brings us to the topic of steam and feel source; as much as I find the idea of flesh-eating trains fun, I do think realistically, their diet would be the same as the fuel used to light their fires. I think of how some of the largest animals on earth are primarily herbivores (or in the case of the whale, filter feeders) and how even if they don't eat meat, that doesn't make them any less frightening that say a tiger or wolf.

Henceforth, I like the thought of living trains grazing on grass and being fed coal by their drivers and firemen, but it bets the question: how do they get nutrients? Initially I thought they'd be literal gastroliths and actually eat the coal they're given, but given how most stones are consumed half of the time to aide in digestion rather than be digested themselves, I figured perhaps something else could be at play.

Enter the volcanic snail

These little guys are amazing because they are found in hydrothermal vents, aka underwater volcanoes. They were actually one of the first guys I thought of with train armor because their foot and shell contain iron, which I think makes for a fun comparison of biological organisms and engines with steel bodies. But back to my initial point, these guys are chemoautotrophs, aka organisms that get their nutrients from chemical reactions through a process called chemosynthesis. Ergo, it wouldn't be entirely unrealistic for engines to technically get nutrients from steam itself rather than what produces the steam, but that begs the question: how do they produce the steam?

After much thinking, I deduced that they could "eat" coal by swallowing it whole and they lighting it up from the inside using a pyrophoric liquid contained in a separate chamber that gets "leaked" into the chamber where the fuel is, thus producing steam that then is released through the funnel/blowhole. And as crazy as it sounds, there is some potential due to the inspiration for this idea: the bombardier beetle

Cute right?

This little fella uses chemistry to ward off predators: essentially there are 2 chambers in its abdomen that contain 2 separate liquids that upon contact, produce a chemical reaction that reaches the boiling the point of water, to which is then expelled as a scalding liquid that causes irritation upon contact. Let me repeat that again: a bug is mixing 2 volatile liquids to create a new liquid as hot as 212 degrees Fahrenheit (100 degrees Celsius) and is then spraying it at everyone else.

From this, I figured the inside of a train would be just as heavily armored as its outside in order to prevent internal scarring from its own pyrophoric liquid once it ignites; I'm comparing it to what the bombardier beetle does in that rather than releasing the explosive reaction, it keeps it inside and and instead releases the byproduct (steam). That being said, I enjoy the thought of an engine "breathing" fire by expelling this liquid not unlike a spitting cobra as a scare tactic.

On a final note, I think if the buffers of trains weren't just elaborate body gear akin to what horses wear when pulling goods or people, I could see them as modified spikes seen on a thorny devil or the kentrosaurs, pointing forwards not unlike a boar's tusk and used in combat and perhaps be subjected to being dulled with tennis balls to prevent accidents like one does with goats.

If by some chance anyone reads this and gets this far, I'd like to both thank and applaud you for taking time to listen to this nonsensical rambling of mine as I've quickly gone down the mine that is ttte and creature design.