#external ear

[er-cryptid]

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[er-cryptid]

External Ear

-- made of the auricle and the external auditory canal

-- auricle is also called pinna

-- auricle is the outer visible earflap

-- external auditory canal is a curving tube leading inward through the temporal bone to the tympanic membrane

-- auricle is made of skin and cartilage

-- auricle provides protection and directs sound waves into the auditory canal

-- auditory canal is lined with modified sweat glands

-- sweat glands secrete earwax

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[artes-magicae]

Normal Ear Anatomy

Lateral skin: dense, adherent, and thin

Medial skin: loose, fibrofatty, and thick

By age 3, at 85% of its adult size

Width reaches mature size in boys at 7 years and in girls at 6 years

Length matures in boys at 13 years and in girls at 12 years

Age makes cartilage stiffer and more calcified

Cartilage is much floppier and more malleable in neonates

[alphynix]

Can (or could) another group of chordates develop external ears like mammals or derived synapsids?

I really don’t see why not. Just because no other groups have developed external ears (to our knowledge) doesn’t mean it’s impossible. Evolutionary innovation happens.

For example: if a random mutation caused a small external flap of skin to arise around the ears of a non-mammalian animal, and the slight sound-funneling effect from that gave it a survival advantage so it could pass down the useful trait to its offspring, then that species could end up eventually evolving much more sophisticated external ear structures. They might convergently become very similar to mammal ears, but might also be very different.

Also, interestingly, crocodylians already have external ears! Sort of. Their ears are positioned right behind their eyes, usually visible as a small teardrop-shaped slit – and they have movable folds of skin that close off these openings when they submerge underwater. Something like that could certainly be a potential starting point for speculative external ear evolution…

[nessuxq027-blog]

Pet King Brand Zymox Otic Enzymatic Solution for Pet Ears, 1.25 Ounces

Pet King Brand Zymox Otic Enzymatic Solution for Pet Ears, 1.25 Ounces ZYMOX Otic is used in dogs and cats for the treatment of acute and chronic inflammation of the external ear caused by bacterial, viral and yeast infections. Treat once a day for 7 days for acute infection and once a day for 14 days for chronic infection. Do not use in conjunction with other topical ear medications or cleaners.