|Image: Dr. Steve O'Shea|
Now that belemnites, ammonites and the rest are extinct, there are 7 main groups of cephalopod alive today:
|Image: Michael Vecchione|
There are almost zero pictures of living Spirula
There are about 300 species of octopus and one, lonesome species of Vampire Squid, both of which are in the superorder Octopodiformes.
|Tip of a Spirula tentacle. Look at all the tiny suckers!|
|Image: Udo Schmidt|
The loosely coiled shell of Spirula
Video: Emma Saying
The word "Spirula" in action
They're not well known, probably because they're less than 5 cm (2 inches) long and live in the deep sea. However, embedded in their back end is a spiralling shell which is both extremely buoyant and surprisingly tough...
|Image: Fritz Geller-Grimm|
Spirula is one of the many deep sea creatures that embark on vertical migrations each day. During the daylight hours they hang out in dark, comparatively safe waters as much as 1,000 metres (3,280 ft) deep. At night, they rise up to depths of just 100 to 300 metres (330 to 980 ft). Even algae go through this nocturnal escapade, but Spirula is probably less interested in the algae and more interested in eating the things that eat the algae.
|Image: Rachel Caauwe (check out her other stuff!)|
It probably doesn't have a loudspeaker which says "this vehicle is now reversing", so no-one is quite sure what it's for. It's thought that Spirula live in large schools in various parts of the tropics, so perhaps it's for communication or some such.
|Image: Ewald Rübsamen|
Look at those little fins!
Tough sheathe of fossil Spirulirostra
Young Spirula have been trawled up from waters as deep as 1,750 m (5,740 ft). It could be that evolutionary history casts its shadow such that Spirula has to descend to the sea floor to breed and lay eggs, like how sea turtles commune with their ancient ancestors when they haul themselves up a beach to nest.
It looks like the loss of that heavy armour was the best thing that ever happened to Spirula. Isn't that just life all over? One minute the best thing to do is sit safe and snug in thick layers of iron and steel, the next minute you're better off dropping it all and floating away. Bah! Fickle! At least something out there knows what's going on!
Thanks to Dimitri and Lear's Fool who both suggested this one!