A few years ago my older brother came across the paper nautilus in one of the news sites he follows on a list of cool animals and immediately sent me the link. Since then, they've always been a particular favorite of mine in the cephalopod clade.

This is from my dad's college zoology course in 1957. It is one of my favorite books of all time, because it has fantastic (and classic) science illustrations. This is figure 23-16, "Class Cephalopoda. Loligo, squid; Sepia, cuttlefish… — This is from my dad's college zoology course in 1957. It is one of my favorite books of all time, because it has fantastic (and classic) science illustrations. This is figure 23-16, "Class Cephalopoda. *Loligo*, squid; *Sepia*, cuttlefish; *Argonauta*, paper nautilus; *Octopus*, octopus. Variously reduced."

And last week for my birthday, I decided to see if I could get myself a paper nautilus shell. I managed to find an Argonauta hians shell on Etsy, actually. It arrived this Friday and it is truly a thing of beauty. It will definitely be a treasured addition to my specimen collection. [Ed. note: I usually don't purchase or collect shells, but I don't live in an area where I could easily comb the beach to try and find one of my own. Lake Michigan foils me again.]

Naturally, I knew one of the CFF blog entries would HAVE to focus on them at some point!

The shell is secreted only by the female octopuses and is used as an egg case. Recently, however, in situ observations of living female Argonauta shows they actively capture air at the surface and then dive deep using the air to make themselves neutrally buoyant at depth. This is especially important when the female has a clutch of developing eggs in her shell and thus more mass. (J.K. Finn and M.D. Norman, 2010. "The argonaut shell: gas-mediated buoyancy control in a pelagic octopus.")
The females of this species have been known since ancient times, but male argonauts were only described in the 19th century. They do not secrete a shell and can be as little as 1/600th of the female's weight. (J.K. Finn and M.D. Norman, 2010. "The argonaut shell: gas-mediated buoyancy control in a pelagic octopus.")
The argonauts are a classic example of convergent evolution. Octopuses and chambered nautiluses evolved from a common shelled ancestor. Over the course of its evolution the octopus lineage has lost the ancestral shell. Over its evolution, the paper nautilus has secondarily evolved a secreted external shell. And it is convergent because the shape of the shell is superficially very similar to the shell of a chambered nautilus and serves the same function as the chambered nautilus shell. This shows how evolutionary pressures can lead two creatures to develop a trait that appears superficially similar. (Helen Scales, 2015. Spirals in Time: The Secret Life and Curious Afterlife of Seashells)

And finally, the art! My watercolored version of my new, absolutely beautiful shell!

Incorrectly labeled "Argonauta argo"–should be "Argonauta hians" — Incorrectly labeled "*Argonauta argo*"–should be "*Argonauta hians*"

What do you want to see featured next week? I'm thinking it might be cicada time! Leave a comment with your ideas.

Hey all!

Today I'm doing a native to my area (Chicago) species: the great horned owl, Bubo virginianus.

I grew up surrounded by owl-related art and books because they are my dad's favorite animal. When Claire (my art student) and I were at the Trailside Natural History Museum in River Forest we were lucky enough to be able to see several owl species, but this guy was the most awake when we went.

Some cool facts:

Their patterning isn't just beautiful, it serves a purpose. The barred stripes and lighter belly with a darker back help prevent prey from seeing them among tree branches.
Great horned owls roost earlier than almost all other raptors in their habitat range. Courtship will begin as early as October! So if you're looking to see owlets you can expect them earlier than other species in your area, though exact timing of egg-laying will depend on the particular area you're in (Nature Conservancy website).
The eye disc feathers serve two purposes: to protect and cover the ear holes, but also channel sound into their ears (Golden Field Guide, 1983 ed., p. 174)

Here's the field drawing I did while we were at Trailside: