Graboid

Graboids are subterranean predators which ostensibly awakened in the late 20th century after a centuries-long slumber, are a lifeform unlike any other previously catalogued in Earth's genetic or fossil record.

Overview
The first documented encounter with the species occurred in Perfection, Nevada, in 1990. Graboid worms, which we have classified as Caederus americana, subsequently appeared in Mexico in 1996, and in Argentina and Nevada in 2001. During the Mexico incident, a second Graboid species, called "Shriekers," was identified. This species has been classified as C. mexicana. The second outbreak in Perfection revealed a morphological variant subspecies of Shriekers. Nicknamed "AssBlasters" by the locals who first encountered it, its official name is C. mexicana combustus.

Throughout this report there are references to "the Graboid species" or "the species" (plural). This generalized term should be understood to encompass the genus Caederus. The colloquial term "Graboid," when used alone, refers specifically to the wormlike subterranean predator C. americana.

Graboids
The Graboid is a worm-shaped creature approximately 10 meters long and more than two meters across at its widest diameter. An adult specimen weighs approximately 10 to 20 tons, which makes it the largest land (or subterranean) animal on Earth. The Graboid displays linear orientation (its head is different from its tail), and dorsal/ventral orientation (the top of its head is different from the underside). It may also exhibit bilateral symmetry, but determining this conclusively will require a more detailed examination of multiple specimens.

The Graboid's body is covered with a dense, leathery carapace. Twisting spines or spikes up to several inches long protrude in irregular rows, forming rings around the Graboid's tubular body. The Graboid appears to lack limbs or other significant external features apart from its head.

This head consists of an armored or plated external sheath, under which opens a three-part jaw. Concealed within the mouth are three tentacles, which can extend several dozen feet beyond the Graboid's head to seize prey. Each tentacle appears to be bifurcated at its extremity, creating a biting jaw with sharp "teeth." This extremity resembles a serpent's head due to horn-like protrusions on one side of the bifurcation. The armored jaw sections and the tentacles all seem designed to funnel prey into the animal's central gullet.

The Graboid has been documented to swallow large objects whole (for example, in 2001, one specimen swallowed an entire 50-gallon metal drum containing noted Graboid-hunter Burt Gummer). This may indicate that the Graboid lacks a rigid jaw structure. More likely, it seems to indicate that the animal's mouth is an elastic, sphincterlike structure, perhaps lined with shearing and cutting teeth. If the animal does have a rigid jaw structure, then it can likely unhinge its jaw (as can many species of snake) in order to swallow prey as large as humans and cattle.

The Graboid's sensory abilities are well-adapted to its underground environs. It has no external eyes, and therefore, presumably, no vision. It does possess remarkable hearing, or at least remarkable sensitivity to ground vibrations: It tracks prey by following noise and movement. (Whether this is a function of sensitive hearing or merely a sensitivity to vibrations remains unclear.)

Behaviorally, the Graboid is carnivorous. It is essentially an ambush predator like a tiger, preferring to covertly stalk its prey. That said, most adult Graboids can move swiftly through loose soil, faster than a human can run. Although Graboids cannot move through solid rock, they can sense the vibrations of prey that has sought shelter on a large boulder or vehicle, or on an artificial structure such as a house.

When possible, a Graboid will rapidly excavate the soil from beneath such a barrier, causing it to sink into, or closer to the ground, where the Graboid can attack with its three tentacles. In cases where such an assault is not possible, the Graboid has demonstrated a remarkable patience, lying in wait for its trapped prey. There are several documented accounts in Perfection Valley of individuals who died of exposure, thirst or starvation while perched on rock islands or atop utility poles, rather than face death in the maw of a Graboid.

Furthermore, the Graboid seems to be highly intelligent. It appears to possess memory; it learns from its experiences. Confronted with problems, it will try to solve them. And it usually will not be fooled more than once by the same deception.

Observers have documented several instances of Graboids traveling together, revealing a degree of socialization. They appear to act cooperatively for hunting, and may be able to communicate on some level (perhaps through subsonic vibrations, as elephants are known to do).

All these factors combine to make the Graboid a startlingly sophisticated creature, despite its primitive appearance.

The Graboid worm has been known, on occasion, to cannibalize its cousin species, Shriekers and AssBlasters. However, the documented incidents involved a limited degree of deception by human observers, so it is not known whether the Graboid normally preys on Shriekers and AssBlasters.

Shriekers
At the end of its life cycle, a Graboid dies in order to spawn three to six Shriekers. This might be a factor of natural aging, occurring when the creature reaches a certain point in its life span. Alternatively, it might result after a Graboid devours a sufficient amount of prey, or it might be triggered by some other internal metabolic or external environmental cue. (El Blanco, the federally protected "Great White Graboid" of Perfection Valley, is an exception. This albino specimen of the species appears to be incapable of generating Shriekers, though we have not yet been able to determine why.)

Shriekers are not a metamorphosed form of the parent Graboid. Rather, it appears that Shriekers grow within the Graboid and eventually burst out, killing the parent creature.

The Shrieker is only about two meters in length, but its body shape and head structure are similar to the Graboid's. It is not clear whether the Shrieker possesses mouth tentacles for feeding as the Graboid does. It might be that its mouth tentacles are present but vestigial.

The most striking difference between the Shrieker and its predecessor in the Graboid life cycle is that the Shrieker perches on two legs, allowing it to walk and run. These legs appear to be articulated with three joints, and they end in three-clawed feet. When not on the attack, Shriekers tend to move from place to place in spurts. They move, stop and scan, then move again. When traveling in this mode they make short, low-register grunting noises.

According to available evidence, the Shrieker's most remarkable feature is that it can reproduce asexually by growing offspring within its mouth cavity. Once born or disgorged, an offspring is smaller than its parent but quickly grows to full size. A Shrieker, by consuming enough food, can multiply itself repeatedly; consequently, an initial population of three to six individuals can rapidly multiply into dozens.

A Shrieker's primary sensory apparatus is thermal. Using a natural heat sensor mounted on top of its carapace, a Shrieker can "see" its environment and search for the specific heat signatures of its prey. When no heat sources are detected, these omnivores search for food by dragging their sensitive tongues along the ground. This enables them to find edible flora and fauna whose temperatures would otherwise blend into the ambient.

The Shrieker is named, however, for the high-pitched noises it makes. Because Shriekers do not appear to have auditory nerves, they cannot hear the piercing sounds they make. Rather, the creatures emit the shriek while signaling each other via a rush of heat emitted from their fleshy mouths. This blast of thermal radiation alerts other Shriekers to the presence of food. Current evidence indicates that Shriekers do not open their mouths wide except when attacking or signaling.

Shriekers appear to be social; they move in flocks and have not been observed to prey upon one another. There is evidence suggesting a dominance hierarchy among Shriekers, as well as evidence of learning behavior. These traits, coupled with their reproductive ability and rapid locomotion, make them relentless predators.

AssBlasters
When a Shrieker experiences a biological, hormonal or environmental cue (the exact trigger is unknown), it sheds its outer husks in much the same manner that a snake sheds its skin. The resulting morphological variation is known colloquially as an "AssBlaster," the third (and possibly final) stage in the Graboid life cycle.

AssBlasters exhibit the same type of carapace and hinged triple jaw found in both the Graboid and the Shrieker forms, except that on the AssBlaster these structures are more slender and elongated. The presence of mouth tentacles seems unlikely, but remains unconfirmed.

The AssBlaster has several traits in common with the Shrieker. It possesses two three-toed legs that allow it to walk, run and jump. Its overall body plan and shape is similar to a Shrieker's, except that the AssBlaster is longer and more fragile in appearance. In addition, it appears to share the Shrieker's thermal-sensory abilities. Like Shriekers they are deaf and, when they spot food, they open their beaks wide to release a loud, heat-emitting shriek to signal other AssBlasters to join the hunt. On the ground, they hunt in a manner similar to that of Shriekers, making the same kinds of low, grunting noises as they pursue their endless quest for food.

Most significant, the AssBlaster has three unique anatomical peculiarities not found in Shriekers or Graboids.

First, the AssBlaster has wings. These are not true wings in the sense of being capable of self-powered flight; they do not resemble birds' or bats' wings (which are modified limbs). By contrast, the musculature behind an AssBlaster's wings is fairly crude. There is no indication that the wings are capable of beating or moving quickly enough to provide lift, or that the wing muscles are well-developed enough to enable sustained flight. Also, though winged, AssBlasters spend the majority of their time on the ground.

Instead, an AssBlaster's wings consist of a membrane of skin suspended between a series of spines radiating straight out from the body. The wings appear to consist of three structures _ equivalent to a left wing, a right wing and a fan tail. AssBlaster wings most closely resemble the "wings" of the flying lizard Draco _ modified ribs that the lizard unfurls in order to glide. AssBlaster wing struts are most likely modifications of the Graboid skin spikes. The AssBlaster controls its glides by flexing, lifting, lowering and even folding these structures, yielding remarkably precise flight maneuvers.

Because its wings cannot power its flight, the AssBlaster has developed its second unique anatomical aspect: a biological rocket. In the act which has inspired its off-color but highly descriptive name, the AssBlaster releases a propulsive force from its tail end. This fiery expulsion launches the creature skyward. At the apex of its ascent, the AssBlaster opens its wings and glides, sometimes for up to a mile or more. An AssBlaster gives warning of impending take-off via a unique "windup," or revving-up sound.

Cephalopods use a variation on jet propulsion for locomotion, but the AssBlaster has evolved the trait to a radically higher level. This feature is not seen in either the Graboid or the Shrieker, but the remarkably high metabolisms of those forms suggest the early gestation of such a robust biology. (We can only speculate on the specific mechanics of this ability; a more thorough examination will require a detailed autopsy of one or more intact AssBlaster specimens. Unfortunately, the Department of Defense has claimed first priority in the study of all such recovered subjects.)

The third trait that distinguishes the AssBlaster from its other Graboid forms is that the AssBlaster bears eggs.

Even more so than the Shrieker, the AssBlaster is highly verbal, uttering a wide variety of unique cries related to specific desires or reactions to particular stimuli. This strongly implies that, in addition to the AssBlaster's thermal sense, the AssBlaster possesses fully developed auditory senses.

Finally, as with the Shriekers, AssBlasters are ostensibly social animals, at least to the extent of not attacking or eating their siblings. So far, they have not exhibited coordinated hunting behavior.

Internal Anatomy
With no access to an intact Graboid carcass for detailed evaluation (most specimens have been severely damaged in collisions or explosions), precise information about the creature's internal anatomy is difficult to come by. Much can be inferred, however, from observed appearance and behavior, and from the scattered biological samples that have been obtained.

Anatomically speaking, the Graboid is a tube wrapped with thick skin-muscle, which is necessary to manipulate its external spines. Presumably, it must also possess a semirigid internal structure (though not a true endoskeleton, as discussed in section 6.0 - HYPOTHETICAL TAXONOMY) since it can burst through concrete (though such an impact kills it). Less dramatically, the Graboid's ability to lift its upper body into the air, as well as bear the weight of the soil through which it moves, also suggests a semirigid internal structure.

This structure is probably coupled with a strong musculature. It is logical to assume that a Graboid propels itself underground partly with its surface spines, and partly with an overall motion of its body. A strong internal musculature would enable the Graboid to flex its entire body, undulating in a curling, corkscrew motion through the ground.

For obvious reasons, it has been all but impossible to directly observe the creature underground; observations of the surface soil above a Graboid's route, however, show that such soil is sometimes humped erratically, producing a series of rises and falls rather than a continuous ridge. This disturbance of the ground is consistent with a writhing, flexing mode of travel. Furthermore, when a Graboid surfaces, it often does so while turning its head or body in a circular motion, supporting the corkscrew theory of locomotion.

The Graboid, the Shrieker and the AssBlaster all appear to respirate the same nitrogen-oxygen atmosphere as other terrestrial animals. Witnesses have heard Shriekers and AssBlasters "puffing," while Graboids sometimes expel blasts of air. This implies that all three Graboid variants possess lungs. Whether these lungs resemble vertebrate lungs is unknown. On a related topic, the Graboid, Shrieker and AssBlaster all have closed circulatory systems; their reddish-orange blood has been well-documented. This suggests that they possess a cardiopulmonary system, a heart pump and an oxygen-based blood-transport system.

Little is known about the creatures' nervous systems, but all forms of the Graboid appear to have sophisticated brains, at least as compared with other predatory animals. All three forms have exhibited signs of being extremely quick studies. We cannot yet measure exactly how smart these creatures are, but they might approach the intelligence levels of such mammalian pack predators as wolves and lions.

In addition, the Graboid would seem to require astonishing levels of energy to propel its prodigious bulk underground faster than a human can run aboveground, yet it does so almost routinely when pursuing prey. It is possible that the Graboid spends most of its time in a torpid or dormant state to recover from these short, intense bursts of activity.

The Shriekers' rapid self-replication and the AssBlaster's ability to generate volatile chemicals capable of launching it skyward suggest extremely efficient metabolisms. Like the Graboid, however, these creatures appear to need rest while digesting food and after prolonged expenditures of energy. Supporting this theory is the observation that, when fully fed, an AssBlaster collapses into a "food coma" in order to digest and to regain its equilibrium.

Curiously, in addition to its feats of speed and its ability to digest large prey, the Graboid has even shown an occasional willingness to eat metal. One of the creatures swallowed a large metal drum containing Burt Gummer, and there is also a report of Graboids attacking a station wagon. Did the Graboids involved in these incidents attack because their bodies are capable of deriving useful nutrients from inorganic objects? Or, as is considered more likely, did the car's vibrations (or Gummer's movements inside the barrel) mislead the Graboids into thinking they had found living prey?

It is possible that the Graboid's underground life gives it access to elements or chemicals that "supercharge" its digestion and metabolism. Because the surface-dwelling Shrieker and AssBlaster also show a similar level of digestive/metabolic ability, the discarded body of their parent Graboid might provide them with these required chemicals. It is also possible that this ability is simply inherent in all three species. Regardless, it remains one of the most impressive aspects of their physiology.

Clearly, much remains to be learned about the bizarre internal anatomy of these creatures. It is strongly urged that the DOI intensify its efforts to collect intact carcasses for future studies.

Ecology
The ecological realities of the Graboid (and its relatives, the Shrieker and the AssBlaster) seem mathematically impossible; however, empirical evidence cannot be denied.

Theoretically (in a conventional mathematical model), the Graboid would require a significant amount of prey in order to generate the energy it needs to function. It is odd, then, that the Graboid has appeared most frequently in areas of sparse human population. Of course, humans are not its only prey; the Graboid may, in fact, be willing to eat nearly any terrestrial animal.

Regardless, it is still puzzling that the Graboid species apparently lives in areas with relatively scarce mammalian life, such as the Mexican oil fields and, most notably, the desert of Perfection Valley, Nev. It would seem that the mammalian populations of these areas lack the capacity to support the Graboid, the Shrieker and the AssBlaster as predators, yet they apparently do.

How is this possible? The Graboid's unprecedented metabolism is so efficient that perhaps the creature requires less prey than most conventional predators. This "frugal" metabolism would allow the Graboid to generate immense energy from relatively small amounts of food.

Alternatively, the Graboid might have other sources of energy that we have not yet discovered; it may derive nutrients (and thus caloric energy) from plants, underground creatures, microscopic life in the soil or even non-living elements and chemicals. These possibilities might help to explain how the Graboid survives in ecological settings that, statistically speaking, should not be able to support its presence.

One final possibility is that the species is not, in fact, surviving very well in these settings. Observed specimens almost never miss an opportunity to pursue prey. Whereas lions that have recently fed will often opt not to chase zebras, witnesses have reported that Graboids will attack even after a meal. This might indicate that the Graboid population is constantly in danger of starvation, resulting in desperately aggressive hunting and feeding behaviors.

Indeed, had the residents of Perfection not developed successful resistance techniques, Graboids probably would have consumed the town's entire human population (estimated in 1990 at just under 20 individuals), which implies that Perfection Valley is not adequate to support a robust Graboid population.

In conclusion, mathematical modeling suggests that the ecological systems in which the Graboid, the Shrieker and the AssBlaster have appeared cannot support the creatures' presence in any kind of long-term, balanced predator-prey relationship. This may indicate that traditional models of predation should not be applied to the Graboid (because of its unique metabolism), that the Graboids have other unknown sources of energy, or that the Graboid species is in danger of extinction because of a shortage of available prey.

Evolutionary History
It is nearly impossible to determine where, when and how Caederus americana might have originally evolved. The species is estimated to be hundreds of millions of years old, meaning that it likely originated when most or all of the continents were joined as a single landmass. However, the species might have evolved on a continental island well away from the hotbed of vertebrate land evolution, where its isolation allowed it to evolve or adapt in unique ways without excessive competition. (There are many better-known examples of this phenomenon: Tasmanian tigers and kangaroos from Australia, giant sloths from prehistoric South America, the lemurs and elephant birds of Madagascar, the moas of New Zealand, and the giant turtles and iguanas of the Galapagos all evolved in relative isolation.)

Alternatively, C. americana may have evolved in temporal isolation. If it began to develop before the vertebrates started moving onto land, it would have been spared competition initially. Of course, at some point, no matter where or when it originated, this proto-Graboid had to contend with vertebrates that had limbs, but presumably this occurred only after the Graboid was set firmly onto its own evolutionary track.

The Graboid's earliest ancestor was probably a small creature similar to a cuttlefish. Unlike the boneless octopus, the Graboid's progenitor probably possessed a shell. This shell may have been completely internal, like the cuttlefish's, or external, like that of a snail or clam, or some combination of both. It was likely a heavier shell than that possessed by the modern cuttlefish; whereas the modern cuttlefish is a fleet ocean swimmer, the prehistoric cuttlefish was probably much more slow-moving, due to the weight of its shell. It was likely a bottom and seashore dweller, preying on crabs and bottom-feeders. It required _ and consequently evolved _ a hard shell to protect its tentacles while dealing with armored or hard-shelled prey.

In the long term, similar cephalopods moved into deep water and mostly lost their shells. Eventually, the prehistoric cuttlefish, which hunted the shallow water bottoms, could not compete with fish or with its lighter, shell-less cousins, all of which were more mobile.

Specimens of this prehistoric cuttlefish might have become trapped in pools or mudholes by seasons and tides. The cuttlefish, trapped in a pool, probably then evolved the ability to crawl across mud flats to reach open water (like modern mudskippers, catfish, snakehead fish, and certain cephalopods), or to burrow into and through moist wet mud until the waters returned (like the modern lungfish). In this way, the cephalopod took its first step toward becoming a land creature; the prehistoric cuttlefish became a proto-Graboid in much the same manner that fish developed into lobe-fin fishes, which became amphibians and then reptiles.

Of course, burrowing through mud was much more difficult than swimming through water. Mud was heavier, and its weight could put severe pressure on the delicate internal structures of the proto-Graboid. Luckily, the creature's internal shell offered some protection. Over hundreds of generations, the shell probably became larger, giving the body much-needed strength and rigidity. This, in turn, limited the proto-Graboid's mobility.

To solve that problem, the proto-Graboid likely began to develop a jointed, segmented shell. If, in addition to an internal shell, the proto-Graboid had already developed an external shell, then it had already separated its shell structure into parts. From there it was only a short step to developing joints. A jointed, supportive internal shell system would be a great advantage for the proto-Graboid. It would multiply the creature's strength, allowing it to survive the crushing weight of mud while giving it the leverage to push and pull itself through that mud more effectively. Whereas limbs were the more convenient and appropriate evolutionary development for surface vertebrates, such physical features would not have been beneficial in the proto-Graboid's adopted environment.

Above ground, the weight and stiffness of the proto-Graboid's internal skeleton would have made it easy prey. Among other land animals lacking limbs, the slug, with no skeleton at all, would have been more mobile than the proto-Graboid, and the snail, with its protective external shell, would have been better protected. Unlike our hypothetical proto-Graboid, these creatures were able to continue their evolution above ground, as were countless varieties of vertebrates that possessed legs and claws.

During this time, the proto-Graboid would have been developing its armored head carapace and the hinged jaws that protect its important inner tentacles. Some of the musculature of its tentacles may have evolved to form the control muscles of the three rigid jaws. Indeed, it is not unreasonable to speculate that the proto-Graboid may have been a six-tentacled creature; three of its tentacles evolved into the Graboid's three major jaw muscles, while the other three remained the Graboid's serrated mouth tentacles. (An analogy can be made to the squid, which also has two different types of tentacles.)

As the proto-Graboid became increasingly better suited to its underground existence, it no doubt became a successful scavenger (and occasional predator) in this small ecological niche.

We suspect that it was during this period that the proto-Graboid lost whatever eyes it might have originally had. Eyes would have been a near-useless vulnerability for a Graboid, which, in a sense, spends its life propelling itself through an abrasive environment. Even small eyes would become a liability to a large tunneling creature because they are inevitably soft and at least partially exposed. Consequently, over millions or hundreds of millions of years, the trait was, presumably, bred out.

The original proto-Graboid may have been the size of a sardine. Obviously one of the most significant aspects of its evolution was its incredible increase in size. This was likely caused by the proto-Graboid's twin needs to move through heavier mud or packed dirt and to hunt larger surface prey.

In classic Darwinian fashion, this larger proto-Graboid was a better hunter than its smaller kin. With added size, speed and strength, it could capture larger, faster prey and attack animals located in places that previously would have been inaccessible. In addition, it could capture, kill and probably eat smaller proto-Graboids. By overpowering its only competitors in the underground ecological niche, the largest proto-Graboids were naturally selected to survive and procreate.

In short order, as the proto-Graboid became increasingly well-adapted to dry environments, it rapidly evolved into the modern Graboid form.

There are unconfirmed reports that Graboid skin-spike fossils have been found in extremely ancient rock, possibly dating to the Precambrian period. If so, the evolution of the Graboids would predate the formation of multicellular life on Earth. If these reports can be confirmed, it might support an extraterrestrial origin for Graboids; more likely, however, is the possibility that the rock samples were incorrectly dated and date to the Devonian era.

Issues of Reproduction
The evolving Graboid had a problem: reproduction. Like every creature that moved out of the ocean, it had to find a way to preserve and protect its eggs in the harsh environment of dry land. Amphibians solved this problem by returning to the water. Reptiles solved it by laying strong, hard-shelled eggs in protected locations. Mammals (and, in a slightly different fashion, marsupials) solved it by carrying their young inside them and giving live birth.

The underground lifestyle of the Graboid posed unique problems that only worsened as the creature evolved into its present form. The proto-Graboid could survive underground, but its delicate eggs could easily be destroyed by the weight of soil. Hard shells were a solution until the eggs became much larger, at which point the pressure of the soil across the eggs' increased surface area again became a serious danger.

In addition, the conditions necessary to support eggs and juvenile proto-Graboids were undoubtedly difficult to find. Eggs laid too close to the surface would be dug up and eaten by predators; newborn Graboids that failed to burrow quickly faced the same threat. Eggs laid too deep would be crushed by the weight of the soil above.

The proto-Graboid had the option to migrate back to the shores to find a viable habitat for eggs and newborn offspring (where the mud would be moist and easier to traverse), but that would have prevented it from migrating inland to richer hunting grounds. For an inland Graboid, with no access to a shore, there was only one safe place where it could incubate its eggs and give its offspring a decent chance of developing to maturity: inside its own body.

For an octopus, a theoretical relative of the Graboid, reproduction can be a death sentence. A female octopus lays eggs and often dies as they hatch. The same is true for the Graboid, which possesses a reproductive strategy far cruder and more primitive than that of mammals (who possess specialized organs and a placental membrane for bearing young). A Graboid's multiple Shrieker young grow like tumors inside its body until it dies, devoured from within by its offspring. Strictly speaking, Shriekers are not a divided, metamorphosed form of the original Graboid. Rather, they are offspring, a larval form of new Graboids birthed by the parent. However, because they are vastly physically dissimilar to the parent Graboid and exist in a different environment, they have a separate taxonomical classification, C. mexicana.

A mature Graboid produces only two or three Shriekers. Additional, undeveloped Shriekers are carried in the mouths of these initial offspring. Among humans and other mammals, fetal twins are not uncommon. Inside the womb, one fetus fails to develop and is absorbed into the body of its twin, surviving as a clump of tissue, sometimes with its own bones, teeth or organs. A newborn Shrieker is actually a dominant offspring, sheltering undeveloped siblings within the tissues of its triple-hinged jaw. As the Shrieker eats, the undeveloped offspring gestate, grow and eventually separate from their more fully grown sibling.

Development of Shrieker Legs
The Shrieker's primary difference from its parent is that it possesses legs. From an evolutionary standpoint, this is extremely puzzling. Cephalopods may have many tentacles, but none has ever produced a leg. Indeed, in evolutionary terms, a limb is a complicated affair, with hinged bones and muscles working together in impressive unison. In vertebrates, limbs evolved millions of years after the initial development of an articulated skeleton in fish.

Because the Graboid appears to possess a semirigid internal structure (though not a true endoskeleton, as discussed in section 6.0 - HYPOTHETICAL TAXONOMY), it is not impossible that parallel evolution would allow it to develop jointed limbs. In fact, the separate musculature of its tentacles could have been a precursor to the development of limbs; all that would have been required was structural reinforcement, to give leverage to that musculature. It may be significant that the Shrieker has three-toed legs, just as it has three rigid jaws and three tentacles. (Indeed, it is possible that the species as a whole might exhibit a trilateral symmetry, right down to its three-stage life cycle.)

There are several possible reasons why proto-Graboids did not evolve limbs. First, their internal shell structure might not have been strong enough to support limbs that were as successful as those of boned vertebrates. Second, limbed Graboids might have been unable to displace well-established vertebrates from their ecological niche, and so died out. Third, the Graboid's level of success underground _ without limbs _ might have precluded any evolutionary interest in such developments.

By contrast, however, the second-stage Graboid _ the Shrieker _ did develop legs (and, by extension, an aboveground lifestyle). The most likely theoretical explanation for this anomaly is that the newborn Graboid was absolutely unable to live underground successfully. It was too small and too poorly muscled, compared to its older relatives, to survive. Underground, it was an easy target for predators.

Consequently, the Shrieker was forced to survive on the surface. To do so, it developed powerful legs and became a swift, deadly predator. Other species exhibit this dissociation between the appearance and abilities of the parent and offspring: butterflies / caterpillars and frogs / tadpoles are the most obvious examples, but one also finds among salmon and eels significant differences between juveniles and adults. The Graboid and Shrieker, while a more radical example of this phenomenon, are not unique.

Ironically, by the time the Graboid evolved this solution to its breeding problems (disgorging its juveniles aboveground), eyes had been bred out of its genetic pool. As a result, the Shrieker and AssBlaster had to dip into their genetic heritage and develop a thermal sensing organ that would function as a substitute for vision.

AssBlasters' Reproductive Role
After Shriekers achieve maturity, they enter the third known phase of the Graboid life cycle: the AssBlaster (C. mexicana combustus).

The AssBlaster differs from the Shrieker in three significant ways: It possesses wings; it has a rocketlike ability to launch itself into the air; and it has the ability to lay eggs.

To recap: An egg hatches a Graboid. The Graboid worm matures and dies to birth several Shrieker offspring. The Shriekers feed and produce additional Shriekers (which, as noted above, appear to be pre-developed siblings). The Shriekers then metamorphose into AssBlasters, each of which lays at least one egg to produce more Graboids. The reproductive cycle of genus Caederus is, to say the least, unique among all known higher life-forms.

It has been proposed by some researchers that the AssBlaster is simply the female of the Graboid species. The evidence supporting this theory is scant, however. The conclusion of this research program is that the Shriekers and AssBlasters both appear to be gender-neutral and capable of parthenogenic (asexual) reproduction.

Because AssBlasters seem to be a genuine metamorphosed form of Shriekers, it is likely that a gestational version of the Graboid egg is present in each Shrieker. It is possible that the trigger for the metamorphosis of a Shrieker into an AssBlaster is connected to the development and fertilization of the Graboid egg.

It is still not understood whether an AssBlaster lays only the one Graboid egg that is inside its body at the time it is spawned, or if it is capable of creating multiple eggs over the course of its lifetime. If AssBlasters employ the same reproductive strategy as adult Graboids, they might be intended to serve as nourishment for the newly hatched Graboid. If, however, Graboid hatchlings are relatively self-sufficient, an AssBlaster might be capable of gestating multiple eggs over the course of its lifetime.

It is worth noting that there is no documented proof that the egg laid by an AssBlaster will yield a Graboid hatchling. All such eggs and often the AssBlasters that laid them have been destroyed prior to hatching. Furthermore, the one AssBlaster known to have survived in captivity Sigmund and Ray's "Messerschmitt" has so far not gestated or laid any eggs. Whether this is a clue to a necessary fertilization step in the Graboid reproductive cycle, or evidence of a single-egg cycle, is unknown at this time.

AssBlaster Biochemistry
Special attention should be paid to the AssBlaster's spectacular rocket-propulsion ability. The closest natural analogy to this ability may be the volatile discharge produced by the bombardier beetle as a natural defense mechanism. The AssBlaster, however, clearly generates a compound far more explosive than that of the bombardier beetle. Anecdotal evidence suggests that the AssBlaster's fuel is a highly combustible, methane-based binary compound.

This "ass-blasting" behavior almost certainly evolved as a by-product of the Graboid's digestive processes. Birds and reptiles have a continuous digestive tract that encompasses their reproductive organs. Consequently, whereas mammals have separate orifices and organs for sexual functions and excretion, birds have only a single orifice, known as the cloaca. It is unclear at this time whether the ass-blasting mechanism is a single organ or gland or multiple organs acting in concert; or whether it is segregated from or integrated into the AssBlaster's digestive tract. For this report, however, we have agreed to refer to the AssBlaster's rear orifice as the cloaca.

The AssBlaster is believed to produce the chemicals it requires within its body, perhaps as a result of its complex metabolism. We speculate that the fuel for the ass-blasting ability is binary (i.e., composed of two substances that do not ignite until mixed) and that the AssBlaster stores these substances in separate glands or bladders. The process of filling these "bladders" is probably continuous. Then, when an AssBlaster needs to fly, it empties the correct amount of propellant from some of its storage bladders into the colon above the cloaca. The storage bladders immediately seal after discharge and begin accumulating more fuel.

In a coordinated release, the AssBlaster then discharges its ignition bladder and releases its cloaca sphincter. If the propellant is a true binary compound, timing is critical: If the fluid ignites too early, the AssBlaster will explode. If the sphincter opens too quickly, the propellant will disperse before it can be usefully ignited.

The cloaca, or the bodily chamber that holds the propellant, must be a remarkable organ. It must be tough enough to withstand an explosion strong enough to propel a creature weighing more than 100 pounds hundreds of yards through the air. Simple Newtonian physics would argue, in fact, that the AssBlaster should explode from the magnitude of the blast. The fact that it does not implies that its cloaca must be not only strong but fireproof.

The cloaca presumably has some form of calcium lining, which is not without precedent in the species. The Graboid possesses the equivalent of an internal skeleton as well as outer shell segments. Furthermore, the AssBlaster lays eggs with hard shells, so it must metabolize calcium. In birds, and probably in the AssBlaster, the eggshell is generated within or just beyond the cloacal tract. It is therefore not unreasonable to posit that the AssBlaster can secrete a calcium-based lining to reinforce its propellant chamber.

The calcium reinforcing the cloaca is probably not a single structure (which would be too brittle) but rather a complex of jointed segments that can bend or stretch to absorb shocks more effectively. This cloacal structure presumably is linked to the semirigid internal structure in order to evenly distribute impact forces throughout the AssBlaster's body.

Despite its ungainly appearance, the overall structure of the AssBlaster is incredibly tough. The question remains, however, how such a bizarre trait as ass-blasting could evolve. Certainly, there is no evolutionary advantage to exploding while trying to fly. The AssBlaster would have had to have all its organs and anatomical features more or less lined up properly before it could take its first flight. This seems paradoxical, however, because such organs would not evolve as they did without a purpose.

Perhaps, though, they developed for a reason other than explosive flight: defense and offense. It is well-known that a number of animals have bizarre escape mechanisms. Some lizards can actually detach their own tails; others can squirt blood from their eyes. Skunks can discharge pungent chemicals from glands under their tails. Octopi squirt clouds of ink as a diversion. Birds, when they take flight, automatically discharge waste so as not to carry unneeded weight.

It may be that the prehistoric proto-AssBlaster, fleeing such vertebrate predators as dinosaurs, discharged waste or gas behind it as a diversion or deterrent. This simple discharge mechanism could have evolved into a specialized defense: a natural flame-thrower. As the proto-AssBlaster learned to control its blasts, it might have achieved subsequently larger and more focused explosions. Eventually, these blasts would routinely propel it through the air. Over time, the modern AssBlaster evolved the physical features, such as wings, that would allow it to glide after blasting off like a wild rocket.

The AssBlaster's wing structures likely developed for some other purpose and were only later adapted for flight. Most likely, the wings originally were skin spines (such as those still possessed by the Graboid) which grew longer and had membranes stretched between them. A number of prehistoric reptiles _ including Spinosaurus, Edaphosaurus and Dimetrodon _ all had sailbacks similar to this; their spinal vertebrae grew to extraordinary lengths and had delicate membranes stretched between them. It is believed that these features evolved for thermal control, because their greater surface area both absorbed and discharged heat quickly. The external membranes of the AssBlaster may originally have evolved to serve a similar purpose.

The simultaneous development of heat-radiating wings and the incendiary discharge mechanism does not seem to have been a coincidence. As the AssBlaster intensified its metabolism to create the volatile chemicals needed for its combustible defense, it would have needed a better way to shed excess body heat and maintain a stable body temperature. The two different organs may well have developed in tandem. Consequently, when the AssBlaster finally began blasting off it already possessed the rudiments of a gliding structure, enabling it to fly.

Taxonomy
The proper taxonomical classification of Graboids, Shriekers and AssBlasters was a curious challenge because the Graboid species does not clearly belong to any previously known Family grouping. To complete its zoological nomenclature, scientists were forced to look much deeper into the evolutionary tree than they had expected.

Graboids have been described by some witnesses as being "reptilian," but this is probably no more accurate than describing the AssBlaster as a bird because it flies or the Shrieker as a frog because it undergoes a metamorphosis. The Graboid does not appear to possess any of the features of true reptiles, though the Shrieker and AssBlaster, curiously, each possess some, such as clawed toes. However, they share just as many similarities with birds and mammals, so a reptilian classification was not indicated.

In fact, Graboids, Shriekers and AssBlasters do not appear to belong to any existing class of vertebrates. They clearly are not fish, and it takes only a slightly more professional observer to see that they they are also neither amphibians nor reptiles, neither birds nor mammals.

It is doubtful that they are even vertebrates, although they do seem to possess endoskeletonlike structures. Vertebrates, it should be stressed, derive from a family of creatures called notochords, which gave rise to fish. Also descended from notochords are amphibians, reptiles, birds and mammals. All these different forms share a heritage of organs and anatomy, ranging from bilateral symmetry to a similarity of organ/tissue types and functions.

The three known forms of genus Caederus lack many of the features inherent to members of the vertebrate line. Most obviously, they lack eyes. Their multistage life cycle is similarly dissociated from known vertebrate reproductive models. In fact, research has not yet yielded any proof that the Graboid species is connected to the vertebrate line.

Regardless, the Graboid, the Shrieker and the AssBlaster are all highly sophisticated lifeforms, which implies that they represent the culmination of a long evolutionary history. Only three other non-vertebrate lines of animal life on Earth have reached a similar level of sophistication: arthropods, annelids and mollusks.

Arthropods (including insects, arachnids, crustaceans and other forms) typically have hard, segmented or jointed exoskeletons, and generally remain small in size when compared with vertebrates. Most arthropods evolved with multiple external limbs and some form of eyes. All these traits are inconsistent with the speculated evolution of C. americana.

Available evidence suggests the Graboid also is not a member of the subphylum Annelida. Annelids and earthworms share some traits with the Graboid, such as an underground habitat, stiff hairs in the skin to assist in locomotion and an ability to extract nutrients directly from the soil. No annelid, however, has ever possessed anything resembling an endoskeleton or semirigid support system, which C. americana is believed to possess. In addition, C. americana and C. mexicana possess other features not found in annelids: segmented jaws; prehensile mouth tentacles; a multiphase life cycle; and thermal sensors. The Graboid is also larger and more sophisticated than any known annelid, making it highly unlikely that genus Caederus belongs in this subphylum.

Genus Caederus might be unique, in a class of its own. It might even be extraterrestrial. More likely, though, it is a form of mollusk.

The subphylum Mollusca is one of the oldest, most diversified and successful on Earth. It includes clams, mussels, snails, slugs, cuttlefish, nautili, squids and octopi. The most advanced form of mollusks are the cephalopods (octopi and squids), which share many important features with the Graboid.

Cephalopods have multiple tentacles, ranging from eight to dozens, all surrounding a mouth or gullet an arrangement that resembles the Graboid's tentacled mouth structure. Furthermore, some cephalopods (such as the prehistoric ammonites or the modern nautilus) have external shells or carapaces, as does the Graboid.

At least one cephalopod, the cuttlefish, has a Graboid-like external carapace, or bony structure. In addition, octopi have enough control over the muscles of their skin to change their texture from craggy to smooth, suggesting a skin musculature similar to that of the Graboid, although of different degree.

The "wing structure" of the AssBlaster bears at least a passing resemblance to the rippling "fins" of the cuttlefish. Although no known aquatic cephalopod ejects combustible compounds, it is a compelling similarity that several eject prodigious clouds of ink as a defensive mechanism, and some have a hydrojet-like propulsive organ that resembles the AssBlaster's dramatically fiery self-launching ability.

Cephalopods are water-breathers, but other mollusks, including snails and slugs, exist on dry land. Many cephalopods, as well as certain bivalve mollusks, are able to survive for short durations out of the water.

Cephalopods are the most intelligent non-vertebrate animals known to exist. Studies have indicated that they might possess a capacity for memory, learning and problem-solving, and witnesses have reported signs of social behavior among groups of squid and octopi. Cephalopods might well be as intelligent as some species of birds or mammals; certainly, they seem to show a level of "smart" behavior similar to that of genus Caederus.

Finally, cephalopods have managed to achieve significant size and mass in aquatic habitats. The giant squid, for instance, is a deep-ocean-dweller that might rival the Graboid in size. The largest known giant squid have weighed several tons and stretched up to 55 feet from their flukes to the extremity of their longest tentacle.

Although the Graboid and its related forms possess features previously undocumented among cephalopods (such as jointed limbs, endoskeletons and a multiphase life cycle), these differences do not disqualify their categorization as mollusks. For example, bivalve mollusks (clams and mussels) possess hinged shells; it is not unreasonable to assume that the Graboid family of mollusks may have developed hinged internal shells and eventually evolved more complex internal skeletons.

However, no mollusk has evolved anything resembling the thermal sensors of the Shrieker and AssBlaster; likewise, the incendiary metabolism of the AssBlaster is unique to the Graboid species. Furthermore, no cephalopod or other mollusk possesses a life cycle nearly as complex as that of genus Caederus.

Still, the shared traits documented above and elsewhere in this document are significant enough to justify a tentative classification of the Graboid, the Shrieker and the AssBlaster as distant, terrestrial relatives of class Cephalopoda.

Historical and Mythological References
The Graboid first appeared to the modern world in 1990. It is probable, however, that humans have encountered this unusual species many times since the dawn of human civilization. Dr. Kate Reilly has theorized that certain formations in Precambrian rocks are actually the remnants of Graboid skin spines. If her theory is correct, the Graboid predates all known forms of multicellular life on Earth. Our own research indicates that the genesis of the Graboid species likely dates to the early Devonian period, approximately 400 million years ago.

If this is true, how has such a large creature escaped notice until now? Certainly it is possible that no human has ever survived a Graboid sighting until recently, preventing news of this creature from reaching the scientific community. But it is also possible in fact, likely that people have, indeed, reported Graboid sightings around the world and throughout history. These sightings, however, have until now been relegated to the realm of myth and legend.

In South America, there are tales of an unknown creature called the "minhacao," sightings of which date to the 1840s. The minhacao is described as gigantic, up to 25 meters long. One report specifies that the creature has two horns (which might be a description of a Graboid's jaw parts or tentacles). According to the descriptions, the underground passage of the minhacao overturns trees, destroys orchards and diverts rivers. The creature is said to be a voracious predator that swallows cattle whole.

On the opposite side of the world, in Mongolia, there are legends of the "olgoy-khorkoy," a species of giant worm believed to live in the Gobi desert. According to tradition, the olgoy-khorkoy is not as large as a Graboid, but it still supposedly attacks animals as large as men and horses.

Deeper in humanity's vast reservoir of mythology lurk other fantastic creatures that might well be early Graboid descriptions. The ancient Greeks feared Cerberus, a gigantic, ferocious hound with three snapping heads that guarded the underground gates of Hades. Was this a description of the Graboid, with its doglike tenacity and its trio of prehensile biting tentacles? The Greeks also feared another three-headed monster, the Chimera, believed to be a combination of dragon, goat and serpent. Were the horns of the Graboid's tentacles the inspiration for the goat portion of the creature, and the sinuous movements of Graboid tentacles mistaken for the twisting of serpents? Indeed, folklore from ancient Greece, Mesopotamia and China is replete with multiheaded monsters.

Furthermore, legends of dragons are common in Europe, South America and China. Modern retellings refer to the dragons as reptiles, but in the earliest chronicles, the word "dragon" was often synonymous with "worm." Dragons were believed to be the greatest of the "wyrms," gigantic and terrible subterranean predators. Even more intriguing is that, although dragons were reputed to be underground serpents, many medieval drawings and Chinese folk tales depict them as winged creatures, sometimes capable of exhaling fire. Could such stories have been inspired by encounters with AssBlasters?

The basilisk and cockatrice, staples of medieval bestiaries, were sometimes described as the two-legged offspring of dragons; many physical traits attributed to these monsters are similar to those of Shriekers.

Similarly, the gryphon, described as a hybrid between a lion and an eagle, figures prominently in these records. Other human legends describe the Phoenix, a bird that was both consumed and reborn in a fiery conflagration, and the Thunderbird, a ferocious bird that made a terrible sound during flight. Any of these descriptions might reasonably be attributed to an AssBlaster.

These varied accounts, previously dismissed as works of fiction, might represent primitive witnesses' efforts to describe the Graboid and its subspecies. Humanity and the Graboid, it seems, might share a long and bloody history.

Threat Assessment
Genus Caederus is a lonely species. Its evolutionary path has left it no known close relatives, in no small measure because the voracious Graboid probably consumed its evolutionary cousins. Other weaker offshoots of the species probably fell victim to competition or predation from vertebrates, or to habitat destruction.

The Graboid species' evolutionary path has also left behind few recognizable fossils. The life of the early proto-Graboid, in wet mud or moist loose soil, would leave few impressions and fossil traces. Even where a loose collection of smashed Graboid shell might be found, its true origin would not be obvious to observers.

This lack of paleontological context, coupled with a lack of basic samples and evidence from the modern creatures themselves, means that many questions about this unique animal remain unanswered. Among these critical questions:


 * Is the Graboid the mature male, the AssBlaster the mature female, and the Shrieker a gender-neutral juvenile? Or is the entire species gender-neutral and parthenogenic?


 * Does the Graboid life cycle incorporate only the three forms so far observed, or is the Graboid capable of new life stages, mutations or adaptations?


 * Can a Graboid survive underwater? Is it possible the species burrows beneath the ocean floor?

A more troubling question, however, lurks in the rarity of the species' encounters with humanity. If myths and legends of dragons, chimeras, etc., are actually ancient accounts of previous encounters with genus Caederus, why have there been such long intervals between outbreaks? Do Graboids hibernate during these periods? Do they withdraw to some unknown and unobserved locale?

Naturally, the most pressing questions about Graboids are those that impact humanity's survival: Where will the next outbreak be? Have the documented outbreaks been isolated incidents, or is a widespread re-emergence of genus Caederus imminent?

Currently, our knowledge of the Graboid species is limited to the experiences and observations of those who have encountered it (particularly Burt Gummer and Earl Basset), and to a handful of poorly preserved remains. There have been only four confirmed outbreaks of these creatures, each of short duration. Each outbreak has featured at least three or four full-grown Graboids, each weighing up to 20 tons. Worldwide, there is only one known living Graboid (El Blanco of Perfection, Nev.) and only one known living AssBlaster, further limiting the possibilities for study.

Yet study is essential if we are to continue answering questions about these mysterious and incredibly dangerous creatures. Indeed, a detailed threat assessment is impossible at this time; too many variables remain undefined. Genus Caederus might be nearly extinct and consequently of little threat. If Graboid outbreaks are rare, and not much larger than those we have seen, then it is likely that the threat to Americans and other technologically advanced countries will remain minimal.

If, however, a much larger outbreak occurs (and the resulting Shriekers are able to multiply unchecked), then the entire human race might be confronted with a catastrophe on a par with a virulent plague or a small asteroid strike. While the worst-case scenario seems unlikely (after all, if genus Caederus was able to overrun the planet and eradicate humanity, surely it would have done so at some prior time, when humanity was less able to defend itself). Still, without further study, it is critical to stress that no possibility, no matter how farfetched or dire, can be eliminated.