Tag: nautiloid

Eons Roundup 14

It’s been a while, but let’s catch up with some more work I’ve done for PBS Eons:

An illustration of both a fossil example and the reconstructed internal structure of the enigmatic Paleodictyon, a hexagonal network of tunnels in seafloor sediment created by an unknown organism.
Paleodictyon nodosum

The enigmatic Paleodictyon, from “Something Has Been Making This Mark For 500 Million Years”

An illustration of Loxolophus, an extinct mammal related to early ungulates. It somewhat resembles a modern coatimundi, with a slender snout, long legs with plantigrade feet and claw-like hooves, and a long bushy tail. It's reconstructed with a mottled and striped camouflage pattern of brown and cream fur.
Loxolophus hyattianus
An illustration of Arctocyon, an extinct mammal related to early ungulates. It has a dog-like head with large canine teeth, a stocky bear-like body with plantigrade legs and claw-like hooves, and a long tail. It's reconstructed with an orange-brown pelt with white stripes along its limbs.
Arctocyon primaevus
An illustration of Eoconodon, an extinct mammal related to early ungulates. It has a somewhat deer-like head, a rather cat-like body shape, claw-like hooves on its toes, and a long tail. It's reconstructed with a coat of brown fur spotted with white along its back and sides.
Eoconodon coryphaeus

The archaic ungulates Loxolophus, Arctocyon, and Eoconodon, from “How a Mass Extinction Changed Our Brains”

An illustration of Aturia, an extinct relative of modern nautiluses. It's reconstructed with an orange-brown shell patterned with zigzagging darker stripes.
Aturia sp.

And the nautilid Aturia, from “When Nautiloids Met Their Match”

Glossoceras

Although the only nautiloids living today have characteristic tightly coiled shells, earlier in their evolutionary history these cephalopods were much more diverse.

And Glossoceras gracile here is an example of one of the more unusual groups of nautloids: the ascocerids.

Living during the Late Silurian, about 422 million years ago, in wheat is now Gotland, Sweden, Glossoceras was only around 5cm long as an adult (~2″). Like other ascocerids it started out its life looking like a fairly standard early nautiloid, with a long straight shell that curved slightly upwards, but as it approached maturity things got weird – the front part of the shell grew out into a much more bulbous flask-like shape, and the old juvenile section broke off entirely.

The gas-filled buoyancy chambers of its adult shell were positioned directly above its body chamber rather than behind like in other nautiloids, giving it very good stability in the water. The shell walls were also very thin and lightweight, which would have made it a much more maneuverable swimmer.