Therapsid ears?

[Sight Reader]

Hey guys, another silly question…

Is it possible to know if therapsids have ears? Most portrayals give them these smooth, lumpy heads that look a bit like melted lava lamps. However, once they decided it was OK to portray Cynodonts with fur, the temptation to make them “look right” by adding ears seems overwhelming, but as a consequence the locations and shapes of the ears I’m seeing seem to be all over the place.

If cynodonts, dinocephalians, dicyondonts, gorgonopsians, etc etc had ears, where would they be? Would they be near the jaw joint or just above it? Naturally, fleshy ears won’t fossilize, but if those ears had muscles that could perk them in reaction to sound, might such muscles leave some trace on the bone so you could at least locate the ear correctly?

Thanks!

[John Harshman]

On 1/26/24 6:29 AM, Sight Reader wrote:
> Hey guys, another silly question…
>
> Is it possible to know if therapsids have ears? Most portrayals give them these smooth, lumpy heads that look a bit like melted lava lamps. However, once they decided it was OK to portray Cynodonts with fur, the temptation to make them “look right” by adding ears seems overwhelming, but as a consequence the locations and shapes of the ears I’m seeing seem to be all over the place.

Well, of course living therapsids do. Or do they? Do monotremes have
pinnae (which is what you mean by "ears")? I don't recall seeing any,
though aquatic lifestyle in platypodes and spines in echidnas may
confuse the issue. Still, there's a suggestion that pinnae are at least
a stem-therian invention.

[Sight Reader]

Hmmm… Firstly, thanks for introducing me to the word “pinnae”… so THAT’S what that is! Secondly, I thought, technically speaking, that “therapsid” was supposed to be a “grade”, meaning that, despite their descendents being all mammals still running around, they nevertheless went extinct when the cynodonts and dicynodonts disappeared somewhere in the Mesozoic.

I never stopped to consider the loss of ears in aquatic mammals: certainly dolphins and whales have no need for fleshy ears. However, I think all mammals have to go through the evolutionary “choke point” of the first few being the rodent-like descendents of cynodonts. Now, if those little Mesozoic pests had ears, then I think could comfidently say that pinnae are plesiomorphic (if I’m using that word right?) for mammals, meaning that those aquatic guys must have secondarily lost their ears.

What’s interesting is to wonder when these pinnae started to appear. Did the first cynodonts have them? Might fleshy ears have predated the split of cynodonts from the other therapsids, meaning that perhaps even dicynodonts, gorgonopsians or even dinocephalians might have had them? Do pinnae leave any sort of trace on the underlying bone, perhaps Sharpey’s fibers or something?

[John Harshman]

On 1/26/24 9:20 AM, Sight Reader wrote:
> On Friday, January 26, 2024 at 7:52:42 AM UTC-7, John Harshman wrote:
>> On 1/26/24 6:29 AM, Sight Reader wrote:
>>> Hey guys, another silly question…
>>>
>>> Is it possible to know if therapsids have ears? Most portrayals give them these smooth, lumpy heads that look a bit like melted lava lamps. However, once they decided it was OK to portray Cynodonts with fur, the temptation to make them “look right” by adding ears seems overwhelming, but as a consequence the locations and shapes of the ears I’m seeing seem to be all over the place.
>> Well, of course living therapsids do. Or do they? Do monotremes have
>> pinnae (which is what you mean by "ears")? I don't recall seeing any,
>> though aquatic lifestyle in platypodes and spines in echidnas may
>> confuse the issue. Still, there's a suggestion that pinnae are at least
>> a stem-therian invention.
>>> If cynodonts, dinocephalians, dicyondonts, gorgonopsians, etc etc had ears, where would they be? Would they be near the jaw joint or just above it? Naturally, fleshy ears won’t fossilize, but if those ears had muscles that could perk them in reaction to sound, might such muscles leave some trace on the bone so you could at least locate the ear correctly?
>
> Hmmm… Firstly, thanks for introducing me to the word “pinnae”… so
> THAT’S what that is! Secondly, I thought, technically speaking, that
> “therapsid” was supposed to be a “grade”, meaning that, despite their
> descendents being all mammals still running around, they nevertheless
> went extinct when the cynodonts and dicynodonts disappeared somewhere
> in the Mesozoic.

Not any more. No currently recognized taxa are grades. All clades.
Mammals are a subgroup of Therapsida. And of Cynodontia, for that matter.

> I never stopped to consider the loss of ears in aquatic mammals:
> certainly dolphins and whales have no need for fleshy ears. However,
> I think all mammals have to go through the evolutionary “choke point”
> of the first few being the rodent-like descendents of cynodonts. Now,
> if those little Mesozoic pests had ears, then I think could
> comfidently say that pinnae are plesiomorphic (if I’m using that word
> right?) for mammals, meaning that those aquatic guys must have
> secondarily lost their ears.

But what about echidnas? They're not aquatic, and they don't have pinnae
either.

> What’s interesting is to wonder when these pinnae started to appear.
> Did the first cynodonts have them? Might fleshy ears have predated
> the split of cynodonts from the other therapsids, meaning that
> perhaps even dicynodonts, gorgonopsians or even dinocephalians might
> have had them? Do pinnae leave any sort of trace on the underlying
> bone, perhaps Sharpey’s fibers or something?

Not that I know of. At least I don't recall any publication making such
a claim.

[Peter Nyikos]

On Friday, January 26, 2024 at 12:20:45 PM UTC-5, Sight Reader wrote:
> On Friday, January 26, 2024 at 7:52:42 AM UTC-7, John Harshman wrote:
> > On 1/26/24 6:29 AM, Sight Reader wrote:
> > > Hey guys, another silly question…
> > >
> > > Is it possible to know if therapsids have ears? Most portrayals give them these smooth, lumpy heads that look a bit like melted lava lamps. However, once they decided it was OK to portray Cynodonts with fur, the temptation to make them “look right” by adding ears seems overwhelming, but as a consequence the locations and shapes of the ears I’m seeing seem to be all over the place.


> > Well, of course living therapsids do. Or do they? Do monotremes have
> > pinnae (which is what you mean by "ears")? I don't recall seeing any,
> > though aquatic lifestyle in platypodes and spines in echidnas may
> > confuse the issue. Still, there's a suggestion that pinnae are at least
> > a stem-therian invention.

John may be right here, Sight Reader. Even when I was a small boy, I was aware that
frogs and snakes had no pinnae, and as I grew, one non-mammal after another
was added to the list. For a while I thought some birds might have some hidden by
feathers, but that too turned out to be wrong.

However, I still wonder about pterosaurs. In the olden days their other features
were depicted as similar to those of bats, some of which have truly enormous ears.
Even the great _Illustrated_Encyclopedia_of_Pterosaurs_, by Dr. Peter Wellnhofer,
shows them as a drab gray throughout. Yet why would they be so if they were diurnal?

On the other hand, might some of them have been nocturnal?
And if so, why not a use of echolocation, for which external ears
would have been an asset?

> > > If cynodonts, dinocephalians, dicyondonts, gorgonopsians, etc etc had ears, where would they be? Would they be near the jaw joint or just above it?

The eardrum is close to the jaw joint in therapsids, and there is a very long discussion
about the relationship between the jaw and hearing in the transition leading up to
mammals in Carroll's book on pages 394 - 395.

In summary: the jaw joint in early therapsids was formed by the tiny quadrate and
articular. In mammals, these became bones of the middle ear while the jaw joint passed
through a "double joint" stage followed by the migration of these tiny bones into the
middle ear. The quadrate became the incus ("anvil") and the articular became the malleus ("hammer").

There is a series of illustrations in Romer's _Vertebrate Paleontology_ near the beginning
of the chapter on amphibians which traces the development of the auditory region
from fish to humans. It is helpful to combine these very clear illustrations with Carroll's account,
where the illustrations are harder to make out, and are confined to the changes from
more advanced therapsids to mammals. During part of that time, the eardrum (tympanum,
or tympanic membrane) apparently emerged to replace a "reflected lamina", and became attached
to another bone, the angular, which became the tympanic bone in mammals.

It's all complicated, and it took me so long to get the details straight,
I didn't get to do nearly as many posts today as I would have liked. Oh, well, Monday is another day.

> > > Naturally, fleshy ears won’t fossilize, but if those ears had muscles that could perk them in reaction to sound, might such muscles leave some trace on the bone so you could at least locate the ear correctly?

> > >
> Hmmm… Firstly, thanks for introducing me to the word “pinnae”… so THAT’S what that is! Secondly, I thought, technically speaking, that “therapsid” was supposed to be a “grade”, meaning that, despite their descendents being all mammals still running around, they nevertheless went extinct when the cynodonts and dicynodonts disappeared somewhere in the Mesozoic.

On the thread about platypuses begun by Popping Mad, I had occasion to talk about
the grade of non-mammalian therapsids, and even John Harshman is familiar
with the grade of "nonavian dinosaurs." However, if his wish of "Aves" being attached to
the crown group of birds is granted, he may have to settle for "non-avialan dinosaurs" to be logical.

> I never stopped to consider the loss of ears in aquatic mammals: certainly dolphins and whales have no need for fleshy ears. However, I think all mammals have to go through the evolutionary “choke point” of the first few being the rodent-like descendents of cynodonts. Now, if those little Mesozoic pests had ears, then I think could comfidently say that pinnae are plesiomorphic (if I’m using that word right?) for mammals, meaning that those aquatic guys must have secondarily lost their ears.
>
> What’s interesting is to wonder when these pinnae started to appear. Did the first cynodonts have them? Might fleshy ears have predated the split of cynodonts from the other therapsids, meaning that perhaps even dicynodonts, gorgonopsians or even dinocephalians might have had them? Do pinnae leave any sort of trace on the underlying bone, perhaps Sharpey’s fibers or something?

These are certainly interesting questions, but I'm as much in the dark
about the answers as John.


Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of South Carolina
https://people.math.sc.edu/nyikos

[trolidous]

On 1/26/24 06:29, Sight Reader wrote:
> Hey guys, another silly question…
>
> Is it possible to know if therapsids have ears?

Is the meaning of the word 'ear' knowable?

If not, then it may not be possible to know
if anyone or anything has 'ears'?

Does this bird have 'ears'? Who can really know?

https://en.wikipedia.org/wiki/Eurasian_eagle-owl

[John Harshman]

The meaning was clear from context in the OP. As for your last two
questions, yes, it does, and I can.

Interestingly, eared nightjars have ears, but so do all the other
nighjars. Eared grebes have ears, but so do all the other grebes. Though
not in the sense the OP meant.

[jillery]

The OP phrased its point poorly, failing to distinguish between "ear",
an organ that senses balance and atmospheric vibrations, and "external
ear" aka pinna, a mammalian invention that improves acoustic
directionality. Not all therapsids are mammals, and non-mammal
therapsids certainly had ears but probably not external ears. This
does not suggest all mammals have pinna.

Also, birds are not therapsids, and their mention doesn't inform the
OP.

[John Harshman]

But they're theropods, which sounds very similar to those who have ears.

[trolidous]

Would you admit that the word 'ear' might have subtly different
meanings in different parts of the thread?

[jillery]

On Wed, 31 Jan 2024 01:57:40 -0800, trolidous <trol...@go.com>
wrote:

That would make an earful.

[John Harshman]

Let's face it, ears are everywhere. The walls have ears, ears of corn,
dogears, wood ears, rabbit ears, the Big Ear. It's downright eerie.

[erik simpson]

Eagles nest in aeries, dond't they? I think we're on the verge of
uncovering as vast conspearacy.

[trolidous]

Yea I remember something like five years or so ago noticing
that roaches were responding to sound, and then looking it
up and finding that much of their sound detecting abilities
were in their legs.

Then there is the lateral line of fish as well.

Such phenomena can tend to be on different locations on
an organism. Sound might be at a higher frequency than
touch but who knows.

[Sight Reader]

Hey, thanks everyone for ‘earing my question out. Sorry I couldn’t respond: we’re getting a lot of drama here at work with a lot of long, complex, high stakes emails. Yes, I was actually asking about pinnae but I didn’t know the word for th fleshy part of ears are called. Someone on Facebook commented on how odd Triassic cynodonts looked without “ears” (pinnae) which is what led me down this rabbit-hole (which didn’t include the rabbit’s ears).