My phylogeny of Temnocerans as of the release of wilds.
What are temnocerans and how do they relate to other arthropods?
The various hunters guilds and scriveners have classified monsters such as nerscylla as chelicerates (arachnids + sea scorpions), but many features of their anatomy contradict this sentiment.
Two key features that define chelicerates is their two major body segments and the namesake of the family; their chelicerae.
Chelicerates lack proper jaws, merely having a pinhole surrounded by straining hairs. This is actually a major factor that separates them from other living arthropods as the other major living arthropod group, the mandibulates (myriapods + pancrustacea), have proper jaws. The chelicerae are the first limb pair on their body (the same limb pair that forms antennas on insects) and while they act as mouthparts they are not part of the mouth proper.
Another major anatomical feature of chelicerates is the cephalothorax. Despite the name, both fossil evidence and fetal development do not support the notion that this body segment was ever a head and thorax that fused. The cephalothorax is in truth just a cephalon, a head. All of the limbs of chelicerates are locked to their head, and in fact this is a hard lock on their anatomy. Because so much of their muscular, circulatory, exoskeletal, and even endoskeletal (many arthropods do have an endoskeletal component) relies so much on their legs being on their face, they are simply unable to move those legs anywhere else or grow a neck. Because of their inability to grow a neck, many chelicerates have to create workarounds, for instance the pelican spider does not have a true neck but rather their eyes and chelicerae sit at an elevated position on their head.
So then how do temnocerans compare to actual chelicerates? Well, they violate these two rules. Not only do they have proper mouthparts, but they have a proper head, thorax, and abdomen. In fact, if Rakna-Kadaki is anything to go by, they co-opted many thoracic segments into a neck.
From left to right: A diagram of more or less an ancestral arthropod body plan and something resembling an early temnoceran body plan. As well as a hypothetical early temnoceran I’ve made called Gorgo-Kadaki.
So if temnocerans cannot reside within chelicerates, then where do they belong? Well a tentative guess could be mandibulata, as they do have jaws, but this is running on the assumption that the limbs that make up their mouthparts are not homologous to mandibulate antennas. Other people have suggested different relatives, for instance @dala-siaka has suggested they might be modern members of Megacheira, and in the past I have suggested they’re a wholly unique arthropod group. It may not be possible to determine what they are, but it’s very clear what they aren’t.
Scorpion mimic temnocerans
While traditionally classified in the crustacean monster family carapaceon, anatomical overlap with temnocerans has led me to believe that these monsters are in fact temnocerans themselves.
The basic scorpion-line temnoceran body plan. Two pairs of eyes have been ditched and the pseudo-neck has been reduced and in later forms lost entirely. Unlike early false-spiders, false-scorpions favored their biramous limb pair 8 for striking and dispatching prey. The reason I think it’s a biramous limb and not a normal arthropod claw is because the two ends of the claws on the larger scorpion monsters move independently of each other and the arm.
Kusubami: The smallest member of the family, these desert dwellers have evolved defensive armor plating over their actual body segments and raptorial limbs. This is similar to house centipedes, which have defensive plating over their actual body plates that doesn’t match up with their actual segmentation. This evolved as a defensive mechanism to better protect themselves against predators, such as Gasurabazura.
Akura Vashimu: Large desert dwelling temnocerans, these massive arthropods normally stay buried underground during the day and come out during the cool nights. It and its closest relative both house a unique mineral mixture within their bodies that can create large crystal structures. The composition of this substance is a hot topic of research, but it’s hypothesized that this is composed of minerals that they absorb from underground water veins they drink from and the bioenergy super-sugars produced by volcanic ground microbes.
Akura Jebia: The closest relative of the Akura Vashimu, these temnocerans favor more mild habits like swamps. While the two species have habitat overlap, it’s likely that the population of their common ancestor was split and separated by rising mountain ranges, and that half became stuck in what would become deserts and the other in swamps.
Spider mimic temnocerans
The basic ancestral body plan of spider-mimic temnocerans. Limb pair 8 has been ditched in favor of striking with the pseudo-neck and devastating mouthparts. Limb pairs 9-12 are the weight bearing limbs. Spider-mimics would lose or reduce limb pair 12 as they increased in size. Ironically, later spider-mimics would reduce their pseudo-neck and develop limb pair 9 into raptorial appendages not unlike the false-scorpions. They also develop silk, a common adaptation in arthropods.
Rakna-Kadaki: Large temnocerans dressed in a gown of silk who call volcanic habitats their home. Rakna exhibit many basal characteristics, and even the body segments that form their jaws have not fully fused to their head.
This species stores volcanic gases in their bodies, which they can expel and ignite in self defense. Raknas have very extreme sexual dimorphism, which is to be expected with a large arthropod. Females are the large and imposing individuals that are fought, while males are virtually indistinguishable from juveniles. Female Raknas carry males and her own juveniles on her abdomen and can issue complex commands to them via hissing to better secure prey or defend herself, indicating high social intelligence for an arthropod. Females get first dibs on meals, while the young and males get the leftovers. Female Raknas exhibit no protective instincts towards their young and mates outside of carrying them on her back, and in fact she treats them as disposable and makes no effort to recover individuals separated from her. This may seem like horrible parenting to us vertebrates, but by arthropod standards she really goes above and beyond.
A subspecies is known that uses its silk like fuses on a stick of dynamite.
Lala Barina: Forest dwelling temnocerans known for their red paralyzing silk and hairs, as well as their resemblance to flowers. Barinas curiously have 9 eyes and 3 pairs of mouthparts (although it’s unclear if it’s a unique limb pair, a duplication of the bottom jaws, or if those mouth parts are biramous). Their arms are also triramous, giving the appearance of three fingered claws.
Barinas have urticating hairs that they can rub off themselves and scatter around the area in defense. These hairs are coated in a neurotoxin and are called Lala Barina Florets, and interestingly they grow from five multi-segmented body parts arranged radially around the space between the thorax and abdomen. It’s unknown what these structures are derived from, be it legs, multiple additional abdomens, or if they’re wholly novel structures.
Barinas also have a stinger on their abdomens, which can extend thanks to a hydraulic system using their blood which then snaps back into place thanks to their tissues being saturated in elastin. Their reproductive habits are unknown.
Nerscylla: A common temnoceran inhabiting a wide range of habitats with a venomous bite. Nerscylla are rather weak to electricity, such as that emitted by the parave Khezu which it has habitat overlap with. So as a defense they sometimes prey on the parave Gypceros, which they then skin and drape themselves with its rubbery hide as defense (this is flipped in the subspecies, which is resistant to electricity and will drape themselves in Khezu hide). The poisons from Gypceros may also dry out and form toxic spines as Nerscylla rest upside down.
These temnocerans may either sneak up on prey and inject a narcotic via their stingers, or administer a venom via their first pair of jaws. These jaws can extend using the same system as Lala Barina’s stinger, which is a key feature uniting the two as each other’s closest relatives.
Nerscylla can inhabit a wide array of habitats, from snowy caves, to swamps, and even volcanic areas. Such a wide temperature tolerance could indicate that the species can regulate their body temperature, which is almost unheard of in arthropods.
While their mating habits aren’t well documented, we do know of their parental habits. Mother nerscylla allow their young (which can number up to 50) to stay in her nest and have free rein to any of her stored meals for their first several molts. She exhibits no cannibalistic tendencies, but also no direct protection, and she may even trample her own young by accident. For an arthropod, that’s mother of the year.
Other notes
Puppet spiders: Initially believed to be temnocerans, a closer look at their anatomy revealed that they are actually spiders. Likely giant jumping spiders.
Baelidae: Despite being grouped in with the crab monsters and not the more spider-like temnocerans, there are many parts of its anatomy that line up with arachnids.
The mouth, aside from the teeth, has mouthparts like normal chelicerates. Now there is the question of if those teeth are just modified limbs or derived from the labium and endites. It does seem to have a cephalothorax that’s covered in multiple ridges. The very base of Baelidae’s legs seem to have two segments between the body cavity and the first visible segment, which would bring the leg segment number up to 7 like chelicerates. And lastly there even seems to be a thick pedicel connecting the cephalothorax and abdomen. It’s very likely that Baelidae might be a primitive or stem spider, meaning that it is the only true spider monster we ever fight.
