Great photo selection with the shifty looking seal (gotta love the whites of caniform eyes) and a nice little summary of the article.
One thing about zoology and animal morphology is that we all know how important feeding is for animals but only real nerds love the digestive tract. Transport, skin, and reproduction are far more glamorous; but the mammalian sense of smell and mouth parts gave us such an advantage in the tertiary period.
It’s interesting that this sort of feeding never arose in the sea. I wonder what the ancestors of the pinnipeds who first ventured back into water ate…
Parent was trying to make a joke about weasels being also shifty, but if ancestors of ppeds were like bears/otters, they would have gone for fish trapped in tidal pools then slowly acquired a taste for nautiloids which are easier to catch
If you find this evolutionary history interesting then I can't recommend PBS Eons enough. It's a great youtube series on the subject: well researched, a dense but breezy pace, and the paleo art + fossil images help convey information without being overly dry.
"Pinnipeds evolved about thirty million years ago. They showed up first in the colder parts of the northern hemisphere, then in the Antarctic, then in temperate zones."
That's an interesting sequence, given that the continents then were about where they are now.
Maybe they evolved in both places independently, or maybe it took a couple million years for a pod of seals to make the journey from north to south, and then start dominating the local ecosystem.
Wikipedia says pinnipeds are monophyletic, so there's only a single evolutionary branch they originated from.
The travel question is much more interesting. Napkin math puts the distance between the polar circles at 12500 miles, the max swim speed of a seal at 25mph, giving a travel time of ~3 weeks of nonstop swimming as the crow flies. How does that happen? What would a pod of Arctic seals have eaten along the way, and what would have compelled them to make the trip out of familiar territory? How and why did they cross the temperate equatorial seas with a load of blubber?
The distance is not surprising, animal trackers have shown they routinely travel vast distances in the ocean [1, 2, 3].
All you need is a fluke event, once in a thousand years where they for some reason make, and survive, this trip (I say thousand to give us some scale, could be actually once in a million years).
Could an iceberg with a few seal families on it have drifted from the Arctic to the Antarctic? Presumably in the tropics the seals would have had a bad time and gone hungry and overheated, but once they got to cooler waters again, they would have been surrounded by food they love with zero competitors.
Life travels on the ocean a lot farther than people realize, and often species you'd find improbably.
Ants spread around the world by hitching rides on coconuts or waterbirds. This now means there's something like a global war among various ant colonies that invade each other this way.
I thought Wind, Wings and Waves to be a pretty interesting description of how species made it to Hawaii. Basically it either gets picked up in storms or large clumps of land make it across the ocean. Life only has to make the journey seldom or almost never and then take hold once to get to a new place.
It's my understanding the ant spreading was more related with increase in navigation than birds/floating. that'd be why the Argentine ant has spread everywhere in Europe in the last century rather than being ubiquitous since the dawn of time.
Well the ocean was filled with free floating ammonites, so maybe food wasn't an issue. Another commenter suggests a volcanic winter to lower the sea temps enough for the seals to cross.
That is interesting. I looked it up on wikipedia and the Argonaut / Paper Nautilus "shell" is a thin walled eggcase and that males do not have. It does not provide protection.
Female argonauts have the shell their whole life long, and do not only construct it when they have eggs to put in it. We may reasonably assume that it has survival value even when there are no eggs. We know, for example, that they carry bubbles in it to tune their buoyancy.
> If you’re inclined to be pedantic about the nautilus’ limbs and say that /actually/ they are “arms” and not “tentacles” because tentacles have suckers on them, then (a) congratulations on remembering that long-ago biology class, and (b) see Footnote 1, above.
Something tells me an arm is a mechanical limb composed of connected poles that turn at their joints. And a hose-like limb without suckers should have its own name. A foot is an "arm", a penis is something else.
I really enjoyed this article, but I was really disappointed. For some reason I thought it was going to evolve into a Lovecraftian epic of how the grand and horrifying civilization of the ancient cephalopods and their relatives was thwarted by another species, one who paved the way for our own ignorant and doomed civilization to thrive.
I kept this feeling until the very end [spoiler] even when it was revealed to be seals I held out hope they could be a Lovecraftian player in a grand epic saga.
One thing about zoology and animal morphology is that we all know how important feeding is for animals but only real nerds love the digestive tract. Transport, skin, and reproduction are far more glamorous; but the mammalian sense of smell and mouth parts gave us such an advantage in the tertiary period.
It’s interesting that this sort of feeding never arose in the sea. I wonder what the ancestors of the pinnipeds who first ventured back into water ate…