Sauceback

Saucebacks are bipedal fauna that are descended from binucleid worms. Together with murkworms, they form a larger group called beastworms. Unlike most worms, saucebacks have an endoskeleton and can grow to be very large.

Anatomy
Saucebacks are bipedal, and all extant saucebacks have feathers. Though many appear to have a neck, this is technically a proboscis--the carapace on the back, also known as the "sauce", is also the braincase and therefore part of the head (see cephalic segment).

The inside of a sauceback's mouth, known as the oral ring, is lined with teeth, the largest pair of which--the "tusks"--being mobile and serving as jaws. Inside the oral ring, are the teeth inside the mouth, which are also mobile and are used in mastication. The number of teeth a sauceback has, including its tusks, directly corresponds to the number of nostrils it has, as the two are directly tied in development. The teeth and nostrils are also developmentally tied to the scent line, similar to a mammal's milk line. The scent line encircles the oral ring. It isn't necessarily a straight line, but you'll always be able to draw an invisible line to connect all the nostrils without crossing over itself.

Saucebacks have lungs in their tails which serve for active respiration. They breathe out of four or five pairs of spiracles on their tail or back, which may be located close to the sauce or much further back. The nostrils are not used for breathing, instead merely being scent pits which are not connected to the lungs.

The legs of modern saucebacks are pillar-erect, meaning that rather than fitting into a socket that sticks inward from the femur like the legs of mammals or dinosaurs, the entire limb is anatomically like a pillar holding up the body. In all descendants of the tusked sauceback, part of the hip girdle is formed from an internalized limb segment. In living species, the limbs are biramous--that is, they branch, forming a cloven hoof instead of the single hoof ancestral to the group.

Saucebacks have two types of vertebrae which evolved completely independently of one another. The tail vertebrae exist in all beastworms. The neck vertebrae are not homologous with these, having developed to hold up the previously soft tissue-based neck-proboscis.

Saucebacks will sometimes appear to have larger heads than they "should"--that is, proportionally larger than the head of a terran vertebrate in a similar ecological niche. This is due to the shape of their skull--as it consists of a rigid ring, saucebacks can only swallow food that fits through it, and as they can't expand it and their ability to chew is limited, having a larger head is the simplest solution.

Though commonly colored white in diagrams for visual clarity, sauceback bones are actually black due to sclerotin, which gives them their hardness.

Weak Spots
Saucebacks do not have tetrapod-like anatomy, so they have a different set of locations that can be targeted by predators or by prey defending themselves.


 * Chest: Unlike tetrapods, saucebacks have their digestive system on the front end of their body cavity.
 * A sufficiently powerful strike to a sauceback's chest can potentially rupture its intestines.
 * A slicing attack, if it gets through their gastralia, is guaranteed to disembowel.
 * Tail: The first few segments from the base of the tail contain the sauceback's entire respiratory system.
 * A strike to the base of the tail or suddenly yanking the tail sideways can knock the wind out of a sauceback, as the lungs are contained within.
 * If the spine is broken at the base of the tail, the sauceback's lungs will be paralyzed and it will suffocate.
 * Neck: Saucebacks do not automatically die from a broken neck, however it is nonetheless still a weak point for different reasons.
 * Breaking the neck will instantly blind the sauceback, as its ears or eyes no longer have communication with its brain. The mouth may still involuntarily flex and bite and respond to visual information, but it will lack proper direction from the brain.
 * Hip/Back: The sauceback's brain is contained within the hip girdle.
 * A strike to the sauce plate (above the legs in plateless species) can stun or cause a concussion.
 * Legs: Saucebacks are obligate bipeds. Breaking a leg is a death sentence in larger species unless they have a pack to take care of them.

Breathing & Blood
Saucebacks breathe actively using 4 or 5 pairs of microlungs along the flank of the tail that are designed to take in oxygen. The ancestor of the saucebacks had pores all over the body. Saucebacks have an iron based blood, which makes it red.

Some saucebacks have developed unidirectional lungs through fusion of the microlungs. Such a system is beneficial to saucebacks with highly oxygen-demanding lifestyles, similar to the evolution of unidirectional lungs in Terran birds, monitor lizards, and grasshoppers. An example of a living sauceback with unidirectional lungs is the sausophrey, which has only two pairs of spiracles--one for inhaling and the other for exhaling.

Diet & Energy
Saucebacks eat using a toothy radial mouth. Modern ones have tusk-like jaws to grab their prey, but there used to be ones who had four jaws to bite. While saucebacks were ancestrally carnivorous hunters of large game, many modern species are omnivorous or even herbivorous.

Some saucebacks will consume large amounts of chitinous flora to help build their skeletons. However, this is not a requirement for all species.

As endotherms, exceptionally small saucebacks have fairly high metabolisms and must eat very often.

Evolution
The saucebacks all evolved from the first sauceback, the golden sauceback. They quickly split into two lineages, vicious saucebacks (descended from the vicious sauceback) and what would eventually become modern saucebacks (descended from the leaping sauceback). At the time, Sagan 4 had two continents; vicious saucebacks lived on Glicker, while the ancestors of modern saucebacks lived on Wright.

In general, vicious saucebacks showed little diversity early on, while the ancestors of modern saucebacks diverged into many forms. The tusked sauceback, which elongated a pair of teeth and internalized its first limb segment, evolved in the Flischian period, and it gave rise to a handful of dead-end branches such as the twin-tailed saucebacks and aquatic swimming saucebacks. It also gave rise to the feathered sauceback--an active, warm-blooded species which would go on to produce many descendants.

When the gamma-ray burst occurred during the Martykian period, it wiped out all but two species, those being the falsequill sauceback and the long eared sauceback. The falsequill sauceback would produce a small number of descendants, mainly burrowing ambush predators, but diversity of its lineage continued to be fairly low. The long eared sauceback, on the other hand, continued its ancestral tend of diversification. One descendant, the cleaner sauceback, was the first sauceback with cloven hooves--and the last common ancestor of all modern saucebacks. The other immediate descendant, the dark sauceback, would give rise to the beach sauceback--the first sauceback to develop any form of photoreception.

When the ice comet struck in the Raptorian period, all remaining vicious saucebacks went extinct. However, the smaller feathered saucebacks continued to thrive. The beach sauceback would give rise to scorpion saucebacks and dagger saucebacks (descendants of scorpion sauceback and four dagger sauceback, respectively). Meanwhile, the cleaner sauceback and its descendants would go on to produce three major groups: polar saucebacks (descendants of snow sauceback), larvabacks (descendants of the false-larva sauceback), and waxfaces (descendants of the waxface). Larvabacks and waxfaces are more closely related to one another than to snow saucebacks, sharing a common ancestor--the foi-devourer sauceback. While snow saucebacks were simply basal cold-adapted saucebacks, the larvabacks are neotenous marine creatures while the waxfaces had internalized all their exposed carapace to protect them from chitinase.

When Sagan 4 entered its snowball event in the Bloodian period, only the snow saucebacks, waxfaces, scorpion saucebacks, and larvabacks would survive. Scorpion saucebacks notably went through a radiation of forms utilizing mimicry. However, scorpion saucebacks would go on to be wiped out by the solar flare that followed at the start of the Masonian period. Waxfaces saw a radiation on Jaydoh, where they were isolated, and they nearly became extinct due to rising sea levels; however, they were ultimately survived by the Pirate Waxface, which followed its prey out to sea. This leaves larvabacks, waxfaces, and snow saucebacks as the current living sauceback groups.

Modern Saucebacks
On the larvaback side of evolution, they diversified into a global genus of marine predators. The first finback, which has a dorsal fin-snorkel bearing its spiracles, appeared in the Darthian period.

Meanwhile, snow saucebacks, survived by the glacial sauceback, had managed to become global during the snowball event and diverged into a huge variety of new forms all over the planet once the ice receded. In fact, it holds the current record for most immediate descendants of any species of sauceback. Among its immediate descendants, the Masonian period saw the rise of megatusk saucebacks (descendants of the megatusk sauceback), which have enlarged tusks and later beaked trunks; and loafshells (descended from the loafshell), which have a segmented carapace, venom, and tridactylism.

Later descendants into the Blargian period would produce more major groups, including harnessbacks (descendants of the harnessback), which have a more advanced respiratory system protected by enlarged back plates and even produced an eyed descendant; and Hagloxes (descendants of the haglox), which are very large muscular herbivores as well as the largest saucebacks to ever live.

Even more new groups would appear in the Bonoian period, such as shrewbacks (descendants of the Shrew Sauceback), which are very small and have high metabolisms like Terran shrews; and jewel-eyed saucebacks (a subgroup of harnessbacks descended from brighteyes), maniraptor-like and sometimes flighted saucebacks with shining "eyestrils". From the latter, flighted bird-like jewel-eyed saucebacks, dubbed "biats," diversified considerably throughout the late Bonoian and into the Huckian, rapidly establishing themselves in Sagan 4's ecosystem.

Locomotion
The vast majority of saucebacks are obligate bipeds, though a handful of species have evolved tripedalism using their tails as a third leg. Most living species walk on cloven hooves, and some are capable of flight using integumentary, bird-like wings.

The first saucebacks had no toes and their limbs were capped with a single hoof bearing cleat-like protrusions. The ancestors of modern saucebacks simplified this into a horse-like hoof, while the now-extinct vicious saucebacks elaborated the cleats into clawed toes. Technically, modern saucebacks have no toes either; rather, their limbs are biramous, meaning that the limb itself branched to form the cloven hoof.

The legs of living saucebacks would seem to resemble digitigrade or unguligrade dinosaur hindlimbs, but what's going on internally is quite different. Ancestral saucebacks had an additional limb segment that is not apparent in modern forms; this was internalized and modified beyond recognition to form the part of the hip girdle which projects and curves backwards to provide muscular support for the "femur". This segment was external and articulated in vicious saucebacks, which is what causes their limbs to appear "backwards" compared to modern saucebacks. Additionally, unlike dinosaurs, saucebacks have pillar-erect limbs--that is, instead of bending sideways to fit into a socket, the femur connects perpendicularly to a horizontal protrusion of the hip, acting quite literally like a pillar to hold up the body.

Diversity of sauceback locomotion:

Reproduction and Development
Most saucebacks are sexual reproducers, they have two sexes, and lay eggs. Some species have a larval form; ancestrally this resembles a grub and bears a complete exoskeleton, similar to ancestral thornworms, but more derived species have larvae which resemble legless, featherless adults. Several species have specialized their larvae for different lifestyles, and some have even lost the larval stage altogether, instead hatching as developed chicks. With no exception, sauceback larvae breathe air just like their parents, though a handful of species have aquatic larvae regardless. Some saucebacks are ovoviviparous.

The eggs of saucebacks are more similar to those of insects than to those of vertebrates. The earliest saucebacks had to lay their eggs somewhere moist, such as underground or in a carcass. However, somewhere along the way, the ancestors of modern saucebacks evolved a serosa, which secretes a chitinous desiccation-resistant cuticle, or shell, over the egg. While this was lost in the line leading up to larvabacks and waxfaces, it is present in most other saucebacks.

Saucebacks with larvae grow in a gradual metamorphosis, changing from larval form to adult form over time, and do not pupate. Even in species with precocial non-larval young, there can sometimes be considerable differences between juveniles and adults; for example, falcophrey chicks cannot fly and megalosheh chicks are bipedal. Some saucebacks, such as waxfaces, produce milk to feed their young.

Senses
Saucebacks' primary sense is echolocation. They have bat-like ears. All saucebacks have a very strong sense of smell. They typically use this to seek out prey from long distances. To smell, they have moist olfactory pits or "nostrils" around the mouth.

Saucebacks almost universally lack eyes, though their ring of nostrils is commonly mistaken for them. There are exceptions, however, which have been sharply rising in prominence.
 * The hearthead actually converted its nostrils into pinhole eyes by adding dark light-sensing pigments to the inside, making it the first species where the "nostrils" really are eyes.
 * The hearthead's descendants include the jewel-eyed saucebacks, which have advanced mirror-based eyes without lenses.
 * The Lipped Sauceback and the Kuraimingaku also evolved "eyestrils" independently of the hearthead. In both cases they only dedicated one or two pairs of their nostrils into visual information.
 * A group of extinct saucebacks descended from the beach sauceback had an infrared-receptor on the forehead.
 * The long extinct Sauceback Hunter had developed an organ on top of their heads that allowed them to detect the heat of prey that was close to them, but it poorly developed and only worked at close range.

Size
Saucebacks have ranged from 9 m Long all the way down to 3 cm Long.

Extant
All living saucebacks are double-hoofed saucebacks descended from the Cleaner Sauceback. They differ from earlier forms in that they have biramous limbs, resulting in the appearance of two hooves instead of one. Some groups have additional "toes", but these are separate structures from the hooves, usually derived spurs.

Waxfaces are saucebacks descended from the waxface which lack any external chitinous plates, even walking on padded feet instead of hooves. Their namesake feature is the production of wax which covers their faces and jaws, allowing them to feed on organisms which use chitinase as a defense. Living species also use their wax to waterproof their feathers.

Loafshells are often venomous saucebacks descended from the loafshell with distinct downwards-pointing jaws and segmented, "loaf-like" shells. A spur on the back of the foot is elaborated into a third toe in some species.

Hagloxes are giant armored herbivores descended from the haglox, they include some of the largest saucebacks to have ever evolved among their ranks.

Harnessbacks are descendants of the harnessback which have chitinous ceres around their spiracles which provide support for their lungs, granting them more stamina than other saucebacks.

Megatusk saucebacks are descendants of the Megatusk Sauceback which, as their name implies, have massive jaws used like a mobile version of an elephant's tusks. Many species are also armored and have long mouths tipped with specialized teeth that function as beaks.

Shrewbacks are descendants of the Shrew Sauceback which are small and, as adults, have high metabolisms, much like Terran shrews. Their ectothermic larvae are among the most independent of any living saucebacks.

Jewel-eyed saucebacks are a subgroup of harnessbacks descended from the brighteyes which have evolved mirror eyes derived from their nostrils. Some species are capable of flight.

Biats are a subgroup of jewel-eyed saucebacks descended from the interbiat which resemble birds and are capable of powered flight.

Larvabacks are secondarily aquatic cousins of waxfaces descended from the False-Larval Sauceback which resemble the larvae of some earlier sauceback groups.

Finbacks are pelagic larvabacks descended from the finback which resemble fish.

Extinct
Vicious saucebacks, sometimes misleadingly referred to as jawed saucebacks, were basal ectothermic saucebacks descended from the Vicious Sauceback which had four jaws, as opposed to the two found in tusked saucebacks. They died out as a result of the ice comet impact event.

Scorpion saucebacks were single-hoofed saucebacks descended from the Scorpion Sauceback which evolved biramous limbs independently of true double-hoofed saucebacks. They killed prey with their tails, which were arched over their backs like the tail of a scorpion. They died out at the end of the snowball event.

Dagger saucebacks were descendants of the Four Dagger Sauceback which used their jaws and extensions of their sauce plate as blades and impaled their prey on them to kill them. They died out as a result of the snowball event.

Two-tailed saucebacks were basal tusked saucebacks descended from the Two-Tailed Sauceback which, as their name implied, had two tails. They were wiped out by the gamma ray burst.

Succeeded
The types shown here technically still have living descendants, but they have deviated so strongly from their extinct ancestors that they are no longer regarded as the same type.

The basal featherless tusked saucebacks descended from the Tusked Sauceback lacked the feather covering of their living descendants. These basal forms became extinct as a result of the gamma ray burst.

Single-hoofed feathered saucebacks descended from the Feathered Sauceback lacked the biramous limbs of later groups. This basal grade became extinct at the end of the snowball event.

Meta

 * For a time, Sauceback clones were very common in Spore-based worldbuilding projects.
 * Saucebacks have been subject to a great amount of misinterpretation compared to other lineages.
 * It is very common for the nostrils around the face to be misinterpreted as eyes. The "eyestrils" of the hearthead are a light-hearted reference to this phenomenon.
 * As a result of a woefully inaccurate skeletal diagram being added to this very page, for a time it became extremely common for saucebacks to be misinterpreted as having completely toothless mouths apart from immobile tusks. Some extant branches, such as hagloxes, are still afflicted by the lingering effects of this misinterpretation.