Pseudomandibulatoidea

Pseudomandibulatidae (Fake-jaws)
"Fake-jaws" are a predatory group of Gomphiobian descent, that arelive in the Vadum Mare and are mostly specialized in taking down large armored preys.
They achieve this with their increadibily powerful "bites"...well more like death hugs...of their main characteristic features the 'thoraco-cranium'(chest-skull) and its apendage the 'mandibulomanus'(jaw-hand). But to understand what these animals are first we should take a glimps to the past to see how they are came to be.

Evolution:
Far off into the past a very basal group of Gomphiobians have adapted to an unfilled niche of stationari ambush predators, this group gave rise to a back than very diverse group the Lucatora ("wrestlers"). This group of small to medium size predators specialized in burrying their body in the soft upper sea floor, or simply just mimicing the environment they lived in, waiting for the unsuspecting prey to come close enough, quickly lunge the upper body up, and catching the prey with their highly specialized forelimbs, tackling it than delivering rapid blows with their bladed head-plates.This group, being stationary ambush hunters, had already lost theit tailfins and it was replaced with wide flattened tail plates that served as support as the animal lunged the upper body for the prey item, the second pair of fins was also strong and enlarged also pushing the body uppwards. For this movement to be possible the creature gained increased flexibility dorso-ventrally while lost movement range laterally. To detect prey abov them the sensory sistems are concentrated in the top region of the head-plate, this includes the larger parts of the eyes, and elecrtoreceptors. These features paved the path that lead to our modern day Pseudomandibulates. The Lucators diverged into many groups, but one of them called the Osteoruptoriformes or "Bone breakers" a group characterized...well...by their bone crushing front limbs proved to be the most succesful. This group contained the ancestors of the Pseudomandibulates, whom at this point looked very similar to their other bone crushing brethren, save for the more well defined jaw like structures, and a small but key feature, a stronger and more flexible tail.
Folowing an extinction event that had left the niche of large swimming predator open, the most mobile of the "Bone-breakers" took the advantage to fill it. Thanks to their relatively strong and mobile tails compared to their cousins, the basal Pseudomandibulates won the evolutionary race to fill that niche. Altough it was mostly an infighting. They diverged quickly and obtained large body sizes, but soon they faced competition from each other. Worst than that, with large armour crushing mobile and more efficient predators around, the other lineages of the "Bone-crushers" not only faced competition, but they were also preyed upon. Outcompeted and hunted the last of the other lineages went extinct.
From the chaos of the initial burst of adaptive radiation, a new world started to emerge, many of the "Fake-jaws" went extinct competing with eachother, but the strong and adaptable survived. There were those whom outcompeted their oposition by sheer size and strength, while others find alternative preys or niches to fill, unexploited by their brothers.

So now that we have learned about their evolutionary history, what makes a Pseudomandibulate?
What maintly distinguished them from their cousins is their enormous "heads". The thoraco-cranium is one functional unit that serves as the creatures de facto head, and it consists of the bony head-plate (a common trait of Gomphiobians), the muscular neck and it's thick external bony plate, an enlarged ventral "chest"-plate, and the specialized first pair of limbs icluding their extrinsic muscles (muscles that originate on the body and ataches to the limb). Altough this massive weapin has one drawback, since their head is essentialy fused to their body, they cant turn their heads.
The fake-jaw is created by the head-plate as the upper jaw and the 'mandibulomanus' as the lower jaws, their continously groving boneplates grind eachother as the animal bites, creating self sharpening edges. The muscles of the neck push the headplate downwards while the muscles of the limbs and body are pushing the "hand-jaws" upwards, giving the creature an enormous "bite" force, which is nessecary to hunt their armoured prey. Most "Fake-jaws" have a gap between the chest plate and the "mandibles" so the proboscis can move and feed freely while avoiding contact with the sharp plates of the "jaw". Most of them also does not process the food with their mouth just crack it and break it into larger peaces, this means that the shearing of flesh is the proboscis' duty, in their opening there are three tilted semi-sircle shaped saw like structure, which closes on and slides abov eachother as the proboscis suckle in on the meat, shearing chunks out of it hastening the process.

The sensory systems of this group is very similar to their ancient Lucatora relatives, most of the sensors are concentrated on the top of the head plate, so it can detect more efficiently what is abow it. This means that most of them still prefers to aproach their target from below if possible, finishing unsuspecting prey with one crushing bite. Altough their eyes are quite interesting. Their compound eyes are separated into three pairs, commonly sitting on dome like structures, the pair closet to the fron of the animan are usually the largest and they almost face forwards, the second pair is usually located further up on the plate but looking more side ways, while the third pair is located on the widened caudal part of the head plate directe more upwards. The arangement of the eye pairs is believed to help the creatures judge distances based on how each eye precieves a given target.
These creatures are not just heavily armed but armoured as well. It is both a remnant feature from their evolutionary past when they were preyed upon more often, and also a deffence mechanism againts members of its own family. Their backs and sides are covered with large interlocking plates that allow dorso-ventral movement, but restricts lateral movement, the plates sometimes have bony protrusions both some for display some for defence. The unarmored parts of the body is covered with bony squamous skin, these scales are small and non overlapping but they are strengthened with larger osteoderms in regions where there is not much motion going on, the scales are even smaller or may disapeared under the joints and areas that are important in movement. Some species have some armor on the ventral side as well but this is usually smaller thiner but also less restrictive than the back plates, altough most species only have hardened squamosal skin on the underside similar to their normal skin but with larger thicker scales.
As you can imagine, such an armored armorhunter (in most cases) won't be the fastest creature around, but altough not particularly fast they are quite agile given their size, stature and body covering. This is achieved by very strong enlarged second pair of fin-like limbs (a trait that originated in their wrestling ancestors), which is mainly used for manuevering but it can also be a powerful tool of propultion if higher speed is needed (say for example...if you want to ram something from bellowe befor it has the time to notice you). However these creatures use dorsoventral Thunniform swimming style (like that of dolphins) as the main tool of propultion, they swing their massive tails ending in large-surfaced crest-shaped bony plates up and down (some with more grace than others), the end ot the bends downwards as it is lifted up so the plates became more vertical and as such they create less resistance, when the tail is swunged down however the interlocking plates will not allowe such degree of bending an the almost horizontal "tailfins" push a large amount of water backwards propelling the animal forwards. The mid section of the tail is stiff, acting as a leaver, while the strong muscled base of the tail alongside with most muscles of the creatures hind section of torso generates the force required to move it. The third and fourth pair of limbs are also fin-like but much smaller and not nearly as powerful, mainly their just stabilizing the animal. The membrans of the fins are strengthened with fiberous structures.

Armavenator tremendus (Arma "armor" - Venator "hunter", tremendus "tremendous/gigantic/dreaded/dreadful"):
If we ignore it's massiv size, Armavenator is your average generic Pseudomanidbulate. In fact it is a product of the race for the large bodied predator niche that kicked in the groups swimming career. It has a massive had (as you would expect) and the largest lower "jaws" both relative to its body and compared to any other 'mandibulomanus'. On the cranial half of the torso armor is thick but fragmented especially along the side, the armor on caudal half of the torso however fused together into one single unit. The belly is also protected with armor plates, and the second ventral plate is especially enlarged, this may have given it some evolutionary advantage againts other Pseudomandibulates, providing limited protection from below. The armor is ridled with bony knobs they are more defined and spike-like in juveniles, but they become comperatively smaller and blunter as the animal ages, for it will grow to such sizes that it will have no natural predators.
Speaking of size and age, let's take a look at this creatures less generic aspects. The creature starts its life as a quite defenseless small thing in the water, as its armor is quite fragmented and fragile right after birth with the exception of the thoraco-cranium. But what they lack in strength they make up in numbers. However in the early years of their life they grow incredibly fast (at least compared to what happens after), from less than half a meter long, the juveniles grow to around 6-7m and fully armored sub-adults in the first two years of their life. From this point on however their growth-rate switches from exponential to linear. In the next fifteen to twenty years they will almost double theirs size and have reached sexual maturity, and then again their growth slows down but now exponentially. The average length of an adult A. tremendus is between 13-16m (their size not only depends on the age but also how nutrient rich is the individuals environment), however individuals above 18m has been recorded. This massive size is achieved through the fact that they never stop growing, altough these giants are extremely rare and tought to be around 120-150 years old. These individuals are even more bulky, amassing muscle and fat so much that the gaps in their armor plating start to apear, sometimes even the fused hind armor is strart to crack. But such a massive size requires a massive amount of food. Indeed most adult's death is caused by the inability to sustain their massive bodies.
The favoured prey of Armavenators are large slow moving armoured creatures mostly of Panoplovitan descent. Altough they will eat anything they can catch, they need to hunt armoured prey to sustain the sufficient growth of their own armor especially the constantly growing plates of the "jaws". Their favoured hunting method is to swim below the target and ambush it from below, cripling it with one crushing hug so it can't put up much of a fight. This method of hunting is favoured because it onserves a lot of energi, energi that its massive body needs. After the kill has been made Armavenators tend to swim to the shallows, where they can rest while feeding on the carcass. The massive jaws crakck the bony armor apart while the proboscis feed upon the flesh and small enough armor fragments to goble up. Armavenators have glands on the inner surfaces of their proboscis that excreet saliva-like mucus and enzimes that help digesting the bone-plates. After the feast they tend to rest sometimes for days, expending the nutrients for regeneration and growth and storing the energie mainly as fat-like tissue spread in thin layer across the whole body and larger blubbers on the unarmored sides.
Outside of hunting they are peaceful creatures, not both intra- and extaspecific violence is incredibily rare. They live in symbiosis with a wide warieti of small creatures, some seek shelter on its back plates while feeding on its parasites, others tend to clean its jaws and proboscis after a messy feast.
Adults have large teritories but as they are realy slow paced creatures multiple adults teritory can overlap without them even noticing. Scarcity of food is what usualy reveals this to the parties involved and according to its severity the dispute will be resolved most of the time non-violentl. Sometimes size is enough to deter a rival, othertimes a friendly pushing contest is needed to secure ones rights over a given piece of water, and there are unfortunate circumstances that involve one or two individuals on the verge of starvation, where one (or both) of the contenders must fall.
During mating season so many of these creature are in the same place that no ecosystem could suply them, this is being solved by them not eating during this time, however this means that all of the stored up fat an energi is burnt away and sometimes even more. Males contest for the females in a wrestling contest, larger males can deter smaler ones by sheer size, but if two more or less equaly sized male finds each other the match begins: they will to get abov their opponent and push him down with their massive head to the sea floor of the shallow water, this ensures that non of the contenders sufer major damage. Altough the championship is not the most violent thing, not eating for a long period of time while contatly using up energi takes a toll mainly on the males, but this also ensures that only the fittest survive. The mating season lasts for about two weaks and afterwards the fertilised eggs are left in the shallows unguarded, providing food for some lucky thiefs. Those eggs that survive will hatch into the small fragile creatures that continue to write the story of armoured giants.

Novaculos truculentus (Novacula "razor" - Os "mouth", truculentus "ferocious/brutal"):
One of the strangest and most derived Pseudomandibulates, Novaculos or "Razormouths" are almost every exception to the rule. When the great strugle for the biggest meantest armorhunter had been going on and its ancesters found themself on the loosing side, something like a miracle happened. Most "Fake-jaws" are born with fragmented and softer bony plates with the exception of the head, and a lineage of them started to hone in on this pedomorf trait. As the first thing to notice when you look at a "Razormouth" is its distinctive lack of armor compared to others of its family. Thanks to this trait it could specialise in to niches that none of its kind manadged before, namely soft but fast moving prey. "Razormouths" have a very flexible body due to not having interlocking plates of armor, but it does have stong muscles and the unique swiming style of its kind. To further increase its speed, a fiberous membrane stetches across it's thin tail spikes, increasing surface while decreasing weight. The strong second pair of limbs can give it aditional bursts of speed and provide excelent manueverability, while the barely moveable hind limbs are used as stabilizers. These adaptations make them excelent pursuit predators. But what is this great speed for you may ask? Well it is to propell a giant devastating head. While it does not have the largest lower jaw, it does have a very large head powerful neck muscles and the highest bite force to weight ratio (altough they are comperatively light to other members of the family). Their head is short, which alowes them to deliver powerful bites rapidly. Indeed their mouth cavity contrary to other Pseudomandibulates are almost fully closed with negligible space between the chest plate and the "mandibles". This way it can process soft meaty food in its "mouth" without creating large amount of waste. The proboscis are therofre shorter and usually not ejected out of the jaws (especially not during feeding), instead they suck up large chunks of meat from the mouth cavity that the sharp bone plates has sliced off. The saw like meet slicing structures in their proboscis are reduced further decreasing the size limit on what it can gobble up. To suplement the growth of their head-gear "Razormouths" also need to consume bone, but seen as they have much less armor it is only a fraction of the quantity that other members of its family need. It is enough to rarely hunt some armoured prey, or simply graze upon the bony plates of Polyspeculates. Its bony head-plate is more round than that of other members of its family, almost half-sphere like, and the sensory organs are also spread along its entire surface instead of being concentrated on the top giving them a wider area of sense.
Another unusual trait of Novaculos species that they, unlike other Pseudomandibulates, are sexually dimorfic. Males tned to be a bit bigger, but far more colorful than the dull orange-brown females, males have a base coat of bright orange with glistening azure srtipes and spots and and fin mambrains. They also poses bony protrusions on their head and neck plate. These are simply display structures, the healtyer the male the more excess energi it has to grow these structures and produce pigments.
During mating males contest by a ritualistic swim-dance called flshing, the males try to swim a way as the sun reflect off of their azure marks and fins the most, twigling their body and vibrate their fins to create flashing lights. This atracts mates and scares off rivals, and so the brightest and flashiest of the males can procreate. they are mostly solitary, but can form adhoc packs to take down larger prey, but with no coordination what so ever, only multiple individuals independently attacking the same target.
Novaculos species has fast metabolism, which is also a pedomorf trait but they keep it for life. Because of this they folow a 'Live fast, die young' strategy. Thanks to their high metabolic rate they can be more active but also require more food compared to their sizes. They must hunt multiple times a day. If they are near starvation, their body kicks in to a panic like feeding-frenzy mode (mostly trough hormonal system) and they attack almost anything on sight including members of its own species.

Captoforfex inopinatum (Capto "grabing/catching" - forfex "scissors", inopinatum "unexpected"):
Captoforfex is a relic of the past, a reminder of what was before the "Fake-jaws" went to take a swim. It has an extremely basal bodyplan, so uch so that if not for its fully fledged thoraco-cranium and genetics it could be mistaken for an other lineage of Osteorupturiform or even Lucator. It is a stationary ambush preadtor using the same techniques as its ancestors used for so long. However it has a key difference to its ancestors and similar lifestyled relatives, mainly that it survived to present day. But how? How did it survived what wiped off the very similar relatives. Adaptability and generalism. Catoforfex is a generalist, while most "Bonebreaker" went extinct because the Pseudomandibulates were better at catching heavily armoured prey, Captoforfex didn't realy had that problem, because it and its ancestors always caught and ate whatever it could catch. The other reason is that most of its relatives were specialised for larger prey, while Captoforfex prefered small to medium sized preys. This wider variety of food source made it possible for this species to remain alive to present day.
Altough the body of Captoforfex is extremely primitive, it has all the key features of its fake-jawed relatives, all except one, namely the massive jaw. Instead they have barbed scissor or forceps like manuses wich can be closed on the spiky sharpened edge of the deadplate. The 'mandibulomanus' of Captoforfex relatively weak compared to any other Pseudomandibulate but they are much more flexible even capable of limited pronation and supination, and as they are capabla of independent movement (as almost all Pseudomandibulates' mandibulomanus can) they are excelet precision tools for grabing, holding and manipulating prey, while the proboscis make short work on the flesh.
Its body is very reminsicent of ancient Lucatorans with flattened wide body and reduced back plates. It does not swim often, it does not swim well, but if needed it can burst at high speed for short distances with swings of its long flat tail, mainly to escape potential predators.
It survived its similarly built peers, Captoforfex is in a slow but steay decline."Keep it in the family". Altough rarely but it is preyed upon by larger swiming forms of "Fake-jaws",( if for example a hungry and unfortunate one reveales itself before an equaly hungry subadult Armavenator when atempting to catch some prey), but the main problem stems from the relatively young Novaculos species, with which it's selection of prey items has a greater overlap (mostly with the smaller species N. agilis). The the unarmored part of the small to medium sized prey of this ambush predator are also on the menu of the very efficient and very hungry "Razorjaws".