INTRODUCTION & BIOLOGY[]
Cephalopods, as a whole, are a particularly weird group of animals. Looking into the strangely human eyes of an octopus or squid, one is struck by the weight of what might have been, had vertebrates not been so quick to grab the aquatic niches. On Spec, an entire world of might-have-beens, the weight of this question approaches that of a sledgehammer blow. Spec's land is home to giant dinosaurs, saved from destruction by happy coincidence, and the oceans are, for the same reason, home to a very wide range of tentacled mollusks.
AMMONOIDEA[]
Probably the most famous fossil form, the shape of ancient organism recognized by anyone in any place where such rocks occur, is the coiled ramshorn shell of an ammonoid.
Aside from the ammonoids and nautiloids, all modern cephalopods are classified as coleoids, possessing a single pair of gills and a reduced shell. This clade includes belemnoids (which still possess a shell), baleen-squids and their kin, true squids, octopuses, and vampire squids. Cuttlefishes (Sepioidea) are absent from Spec.
BELEMNOIDEA: Cleaner and hitch-hiker squids[]
Belemnoids are a group of cephalopods superficially similar to squids. They possess advanced eyes and nervous systems and an ink sac, and they bear suckers and chitinous hooks on their tentacles just like true squids. However, belemnoids have not ten tentacles, but eight, and their nether regions, which, in squids, are supported by a flimsy pen, are protected by a complex torpedo-shaped structure similar to the shell of an ammonoid. This internal shell, the belemnoid structure, is not coiled, as in most ammonoids, but straight, composed of a bullet-shaped, calcite rostrum, a chambered phragmocone, and a pro-ostracum, which extends to protect the head.
In our home time-line, belemnoids went extinct at the end of the Cretaceous, doomed by the same calamity that killed the dinosaurs and their cousins, the ammonoids. These squid-like creatures made it through the K-T extinction fairly unscathed, and diversified explosively in the Eocene. The belemnoids, which combine the swim bladder of a fish with the tentacles and siphon of a squid, could well have gone on to eclipse the teleost fish radiation, but that path was not to be. Instead, the Eocene-Oligocene extinction, destroyed most of the teleost diversity, and at the earliest baleen-squid fossils have been dated to around this time. These early fossils show close affinities to the belemnites , however, so these quirky cephalopods may not have fared so poorly after all.
In any case, today’s true belenmoids exsist in only a few specialized niches, the conservative cleaner-squids, which are found mainly in the Caribbean Reef, but may have a larger range, and the cosmopolitan hitch-hiker squids, which are found in equatorial oceans the world over.
Banded Cleaner-Squid (Utilituthis formosus)[]
Modern cleaner-squids are distinguished from their Cretaceous ancestors by several unique features. The rostrum (covered by the muscular mantel) is short and conical, forming the tip of the rear end of the animal. The phragmocone, which occupies the bulk of the cleaner-squid's hind portion, carries a number of chambers and is used by the animal to regulate buoyancy to sink or float. The pro-ostracum, on the other hand, is reduced, forming the base for a fleshy hood. As in true squids, cleaner-squids have two "fins", flexible extensions of the mantel on either side of their bodies that allow them to maneuver with great facility.
In some respects a cleaner-squid had certain advantages when they came to occupy that niche that, in our timeline, is occupied by the cleaner wrasse and shrimps. As a small cephalopod, the cleaner-squid was already the predators of small crustaceans, and were already capable of the complex signaling that the modern cleaner squid uses to advertise their services.
Hitch-hiker squids (Remorateuthis sp.)[]
Hitch-hiker squids (genus Remorateuthis) are a branch of the belemnoid tree that looked so different from their ancestors and relatives they were long considered octopuses. These small creatures use their suckers to grab on to large fish, marine reptilians or baleen squids for a free ride. Though they lack internal shells hitch-hiker squids are actually belemnites, as they have only eight short, hooked tentacles, two of which have more or less united into a flat fleshy plate.
The seas of Spec have a lot of nasty surprises in store for a would-be scuba diver. While large carnivores such as mosarks and penguins of death are among the most feared of marine organisms, some of the most most vile creatures are so small or inconspicuous you won't even think of them as threatening until it's too late. The leechsquid fits neatly in the latter category.
Leechsquid (Nosferateuthis haemophilus)[]
The leechsquids are curious tiny cousins of the hitch-hiker squids, which have gone from mere freeriders to downright parasitic bloodsuckers. The mouths of the these two to five inch long cephalopods are surrounded with stubby tentacles with suction cups and one curved claw-like hook each. The leechsquid uses these clasps to latch onto its victim before it proceeds to bite through the skin with its sharp chitious beak. When the leechsquid pierces the skin it injects an anesthetic agent into the host's tissue and bloodstream. Thanks to this chemical, the leechsquid can often feed without the host even noticing its presence. A stationary leechsquid is also very hard to see, as it can mimic the colour and texture of the surface it is resting.
(fig. 2) Leechsquid, Nosferateuthis haemophilus (Equatorial oceans)