Crown Marsupials are 20 million years younger than Crown Placentals. Interesting, I did not know that. BTW, female kangaroos even have another option - they can pause the development of small embryos, almost like suspended animation in sci-fi. Not sure how many other marsupials can do it / how far back it goes....
@@commondescent Here is another fact stranger than fiction - we've all heard of the cordyceps fungus that parasitizes ants. It turns out there are so many ants & other insects parasitized by cordyceps, another fungus evolved to parasitize the cordyceps, and it saves the ants' lives in the process!
@@commondescent I need to correct myself too. In the chat I said "my favorite fact that is stranger than fiction is, there is a fungus that infects ants already infected with cordyceps fungus, and feeds off the cordyceps & in doing so saves the life of the ant." I looked it up & it does not work like that. There is a "hyper parasitic fungus" or "secondary parasite" that feeds on cordyceps. However, it feeds on cordyceps after cordyceps kills the ant & after cordyceps erupts its spore producing stalk out of the ant's head. This other fungus does "save ants" in the sense that by preventing cordyceps from releasing its spores, it keeps other ants from getting infected & dying, but it does save the ants already infected.
@@commondescent Strangely, the "hyper parasitic fungus" not only smothers the cordyceps fruiting body, it goes out of its way to chemically sterilize the spores of the cordyceps. Since it is a secondary parasite that depends on cordyceps fruiting bodies for its food source, so you would think it would want cordyceps to spread as far & wide as possible. It may be that if cordyceps spreads too fast, it can actually wipe out the local ant colony which would leave the "hyper parasitic fungus" with no more cordyceps in the local area.
is it possible that there's sort of a hybrid situation going on with the osteichthyse/condrichthyse split? The way you describe it, we have placoderms (fish with a partially ossified exterior and cartilaginous internal supports), then some blank space on the timeline, then condrichthyse (fish with only cartilaginous internal supports) and osteichthyse (fish with ossified internal supports). Is it possible that what's actually going on is that, following whatever environmental change in around the end-Devonian caused the placoderm form to diminish and then disappear, the ancestors of osteichthyse internalized the formerly-external bone in some sense, while the ancestors of condrichthyse discarded it? That is, what's wrong with assuming that the ancestors of both osteichthyse and condrichthyse were placoderms and that they just went in different directions when ... let's call it "placodermy" ... was for whatever reason no longer viable, as opposed to assuming that one must have given rise to the other?
What you're describing sounds similar to what the authors of the paper suggest. It's long been suspected that cartilaginous fish split off before bones arose in the lineage leading to bony fish, but the new research suggests bones may have originated and been partially lost in cartilaginous fish. More thorough discussion here: www.theguardian.com/environment/2020/sep/07/fossil-upends-theory-of-how-shark-skeletons-evolved-say-scientists
@@commondescent Huh. I'm still confused by the guardian article; a little less so than the abstract to the actual paper (I don't have access to the paper itself). The article implies an assumption that this particular fossil find indicates that *all* placoderms, or at least those that gave rise to eugnathostomes (condrichthyse + osteichthyse), must have had similar internal skeletal structures. The abstract talks about their analysis placing this fossil at or near the start of gnathostomes generally, which would support that claim, though it would have been nice if that was a little more explicit, and I'm certainly curious as to why that hypothesis is favored over the idea that eugnathostomes are not monophyletic, just as placoderms aren't monophyletic.
Genetic evidence says 160 million years, but there's no fossil evidence going back that far ..... what about the fossil Juramaia? Wasn't that estimated at 166 million years old? They say it's the oldest placental fossil (or close relative of placentals). Presumably other mammals at that time would have been metatherian, or prototherian, right? Isn't that evidence of a split?
Yes! Juramaia isn't on the marsupial line, but the placental line, and is fossil evidence of an early split. So, yes, that does match up with genetic evidence suggesting there would be metatherian mammals at that time.
Idea for ep. 100 - This is a BIG number right? How about a BIG topic like GIGANTISM! ;)
That is a fittingly BIG topic - onto the list, for Ep 100 or otherwise!
"Next month is October. I hear there's a popular holiday in it". Yeah, it's called Croctober that celebrates crocodilians around the world! 😂🐊🎃
Learning about Marsupial sex was wild.
Like I'm planning out a fantasy series with a Kangaroo based race.... I have to rethink some lore now...
Which mole? The afrotherian golden mole?
The insectavorian mole?
The zenathrian pink arm armadillo mole?
The amphibian mole frog?
Crown Marsupials are 20 million years younger than Crown Placentals. Interesting, I did not know that. BTW, female kangaroos even have another option - they can pause the development of small embryos, almost like suspended animation in sci-fi. Not sure how many other marsupials can do it / how far back it goes....
Yes! Pretty sure that's fairly common among marsupials.
@@commondescent How about a video about the tree kangaroos of Papua New Guinea? :)
@@commondescent Here is another fact stranger than fiction - we've all heard of the cordyceps fungus that parasitizes ants. It turns out there are so many ants & other insects parasitized by cordyceps, another fungus evolved to parasitize the cordyceps, and it saves the ants' lives in the process!
@@commondescent I need to correct myself too. In the chat I said "my favorite fact that is stranger than fiction is, there is a fungus that infects ants already infected with cordyceps fungus, and feeds off the cordyceps & in doing so saves the life of the ant." I looked it up & it does not work like that. There is a "hyper parasitic fungus" or "secondary parasite" that feeds on cordyceps. However, it feeds on cordyceps after cordyceps kills the ant & after cordyceps erupts its spore producing stalk out of the ant's head. This other fungus does "save ants" in the sense that by preventing cordyceps from releasing its spores, it keeps other ants from getting infected & dying, but it does save the ants already infected.
@@commondescent Strangely, the "hyper parasitic fungus" not only smothers the cordyceps fruiting body, it goes out of its way to chemically sterilize the spores of the cordyceps. Since it is a secondary parasite that depends on cordyceps fruiting bodies for its food source, so you would think it would want cordyceps to spread as far & wide as possible. It may be that if cordyceps spreads too fast, it can actually wipe out the local ant colony which would leave the "hyper parasitic fungus" with no more cordyceps in the local area.
Seems like there's a lot of gaps in early arachnid evolution.
is it possible that there's sort of a hybrid situation going on with the osteichthyse/condrichthyse split? The way you describe it, we have placoderms (fish with a partially ossified exterior and cartilaginous internal supports), then some blank space on the timeline, then condrichthyse (fish with only cartilaginous internal supports) and osteichthyse (fish with ossified internal supports). Is it possible that what's actually going on is that, following whatever environmental change in around the end-Devonian caused the placoderm form to diminish and then disappear, the ancestors of osteichthyse internalized the formerly-external bone in some sense, while the ancestors of condrichthyse discarded it? That is, what's wrong with assuming that the ancestors of both osteichthyse and condrichthyse were placoderms and that they just went in different directions when ... let's call it "placodermy" ... was for whatever reason no longer viable, as opposed to assuming that one must have given rise to the other?
What you're describing sounds similar to what the authors of the paper suggest. It's long been suspected that cartilaginous fish split off before bones arose in the lineage leading to bony fish, but the new research suggests bones may have originated and been partially lost in cartilaginous fish. More thorough discussion here: www.theguardian.com/environment/2020/sep/07/fossil-upends-theory-of-how-shark-skeletons-evolved-say-scientists
@@commondescent Huh. I'm still confused by the guardian article; a little less so than the abstract to the actual paper (I don't have access to the paper itself). The article implies an assumption that this particular fossil find indicates that *all* placoderms, or at least those that gave rise to eugnathostomes (condrichthyse + osteichthyse), must have had similar internal skeletal structures. The abstract talks about their analysis placing this fossil at or near the start of gnathostomes generally, which would support that claim, though it would have been nice if that was a little more explicit, and I'm certainly curious as to why that hypothesis is favored over the idea that eugnathostomes are not monophyletic, just as placoderms aren't monophyletic.
marsupials are weird and the arm hypothesis is my favorite to explain
Now do Monotremes
Onto the list!
Genetic evidence says 160 million years, but there's no fossil evidence going back that far ..... what about the fossil Juramaia? Wasn't that estimated at 166 million years old? They say it's the oldest placental fossil (or close relative of placentals). Presumably other mammals at that time would have been metatherian, or prototherian, right? Isn't that evidence of a split?
Yes! Juramaia isn't on the marsupial line, but the placental line, and is fossil evidence of an early split. So, yes, that does match up with genetic evidence suggesting there would be metatherian mammals at that time.