Acostega

True Wyverns with the ability to breath and EXPLODE a gas commonly referred to as Blaze, the Acostega is a formidable foe to fight, especially when you consider it's ability to use it's teeth like flint and steel, potentially causing wildfires

Physiology
The Acostega is equipped with a lengthy serpentine neck with short, upward curved (if the head was to look down) spines traveling all across it's body. At the end of it's neck is a Spinosaurus-like head, with the additions of an expanding frill and a third eyelid to protect it's eyeballs, as well as a shortened premaxilla and lower jaw. The prehensile tails on the other end have a sort of snake-like motif, ending in a diamond-like spike at the end. They possess slight underbites in order to be able to use their flint-and-steel maneuver, seeing as how their throats cannot handle a burst of heat coursing right out of their mouth. The monsters possess dexterous feet, enabling it to climb most surfaces with ease, and hunt Tobi-Kadachis. Their main body is similar in profile to said beast, and is extremely flexible, enough to bend enough to formulate a circle used in one of the creature's attacks. Their teeth are serrated, not only to cause friction for the explosions, but also to cleave flesh and send digestive enzymes into the victim, suggesting that the creature has a fairly weak digestive system.

Behavior
Acostegas are opportunistic, yet intelligent pack hunters. While they will take after a herd of Aptonoths or Apoceros with great speed, They often take time to think and formulate a plan for effective hunting. It is rare to walk on an area an Acostega has been and not be caught off guard by one of the traps that they have set up, but haven't sprung. They're pack mentality means cooperation, which requires enough grey matter to coordinate attacks for efficient kills, like when one member of the pack chases the prey into the mouth of another. They also appear to have a mischievous streak, often pulling pranks on hunters by springing some of their traps and giving a dry roar as a laugh. While most hunters don't find this funny, fellow Acostegas would give the same dry roar as a laugh.

Placement in the Food Chain
Acostegas are top predators, not being extremely powerful, but not particularly weak at all. Their frequent hunting of Rejakoris, the toughest known herbivore, makes them excellent fighters during in-species competition and what helps the monsters thrive in an ever lasting struggle for survival.

Behavior to other Monsters
Acostegas will be feared by the lesser monsters like the Jagras, but appear to have an aggressive taste toward Tobi-Kadachis for reasons currently unknown. Locked in a Prey vs Predator duel against the Rejakori, Acostegas will gauge the current blockade of the monsters and attempt to use the terrain against them, using powers of deduction to figure out the best plan of attack.

Explosion Ouroboros
Used in group attacks to lay siege upon a Rejakori's stronghold, the Acostega covers itself in it's own gas and charges. While it's running, it purposefully trips and bites both ends of it's tails to turn into a wheel. Before it bites, it zaps the gas and ignites it, turning into a flaming ball of death and exploding just short of the wall, wrecking it. They have to be taught to be able to use this ability, and overuse can cause scale damage as well as a rapid rise in body temperature. It's not particularly useful against hunters, but the splash damage is more than enough

Flint Stone Ignition
Acostegas have weak internal insulation mechanisms, and are thus unable to breath pure fire. As a result, they must belch flammable gas out of their mouths and ignite it with a method unique only to the species. By scratching their teeth together like flint and steel, the resulting friction can heat the gas majorly, causing massive BOOM instead of a gradual flame that is common with many fire-breathing reptiles. The gas can be ignited with anything that generates heat, like the shot of a gunlance, and is very problematic with people primarily focussing with range.

Explosion Package
By filling a hollow rock with the gas, sealing the hole with string and lighting it, the monster can throw a mini bomb full of their gas that explodes in a furious blaze upon making contact with the ground.

Trivia

 * The Acostega was based off the Hideous Zippleback, the Dramillion, the Spinosaurus, the Changewing from HTTYD, and the Carcharodontosaurus
 * The Hideous Zippleback was used for it's ability to create explosions, general appearance AND the digestive venom attack, the Dramillion for pack intelligence, the Spinosaurus for the head structure, the Changewing for it's ability to camouflage, and the Carcharodontosaurus for it's serrated teeth
 * The Gas the creature breaths has a noxious scent to it, suggesting it may be produced by the creature's metabolism. However, the gas is actually a mix of Ammonium Nitrate and Anhydrous Hydrazine. If you don't know what that is freshen up on chemistry.
 * Acostegas can adopt a bipedal stance temporarily for creating their explosion packages.
 * The monster's theme of Snake and Explosions was primarily thought of while the author binge watched
 * Acostegas were originally going to possess an appearance more akin to the Night Furies, but this was changed to lean toward a Zippleback, minus the dual heads. The Possibilities of there being a Night Fury Monster still remains as fair game for the creator.
 * Acostegas are able to swim very well, due to their gasses.
 * Even though they are capable of flying, Most of the time Acostegas prefer to stick to the ground, folding their wings tightly against their body. Why this is the case is because an Acostega has bad stamina up in the air, and the only time it flies is when it has to jet.
 * In one experiment, Acostegas were revealed to be able to pick locks. This doesn't seem helpful, but because of the scaly tips, an Acostega can effectively "Disarm" (Trigger the trap safely and without fear of being hit by it) mine-traps and take food from other monsters.
 * The monster is Lizard Hipped.
 * This affects the way it walks, as it moves similarly to a Komodo Dragon or a Gila Monster.
 * They were originally going to have 2 heads that followed Zippleback logic: One head breaths gas, the other sparks it. They still follow the logic, but it is confined to 1 head to do both actions.
 * For it's size, the Acostega has the loudest roar. It can be heard even through earplugs, and is often used if the creatures needs to get away. Unfortunately, if they do this powerful roar, they become hoarse and unable to communicate well, so it's mostly a last-resort.


 * Where an Acostega has adapted, it's prey, the Rejakori, will have adapted in an attempt to fight against it.
 * The Acostega's explosive flames have enough force to knock away an entire tree, but through cooperation the Rejakori can create stalwart defenses in the form of rock walls. This doesn't deter the Acostega, as it can get over these relatively small, yet steep, barricades.
 * Rejakoris have some of the most powerful charge attacks, enough to gore a Kestodon right through it's armored skull, so the Acostega has developed heightened reflexes to avoid this attack. This may not always work, as sometimes the herbivores run in rows, so if an Acostega attempted to jump the side during a row attack, it would be trampled by the next one