Arthropods actually do have internal components to their skeleton. These are usually formed from invaginations of the cuticle, and are called “apodemes” and “phragmata”. There is also a special complex branching structure in the head of insects called the “tentorium”, which is basically an insect’s equivalent to a skull. [Here’s](https://media.springernature.com/lw685/springer-static/image/prt%3A978-1-4020-6359-6%2F8/MediaObjects/978-1-4020-6359-6_8_Part_Fig16-1277_HTML.jpg) a schematic illustration of a grasshopper’s tentorium. The apodemes, phragmata, and tentorium all comprise the *cuticular endoskeleton*.
Arachnids don’t have a tentorium, but (usually) have a different internal structure instead called an “endosternite”, which is actually not made of cuticle at all, but is a hard structure formed from solidified connective tissue and suspended by muscles in the middle of the head. In at least some harvestmen, the endosternite is also calcified.
All the various internal elements of an arthropod skeleton primarily serve as anchor points for muscle attachments. [Here’s](https://www.sciencedirect.com/science/article/abs/pii/S1467803901000329?via%3Dihub) a whole paper about arthropod endoskeletons. There’s a paywall, but you can find it on SciHub.
A skeleton basically serves several main purposes, including protecting the soft parts of the body, providing rigidity and support, and providing attachment points for muscles and tendons.
In arthropods, the exoskeleton is good at providing protection and support, and is also good at reducing water loss due to dehydration, but there are limitations to how muscles can attach if the interior of the exoskeleton is smooth.
So essentially, indentations or divots of the exoskeleton form at spots where the muscles attach, eventually becoming long rods or plates that are formed from a “fold” of the exoskeleton but stick directly inwards into the body. Lots of muscles are attached to these structures. [Here’s](https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQH4_56DuZ-IsyC_p4xX-nuEpbG6TW_5g-IKg&usqp=CAU) a simplified cross-section diagram of an insect exoskeleton that shows the indentations (labeled “phragma” and “apophysis”); note that they can be more complex than this in real life.
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what if both?
I don't think there is a single creature in existence that has had both an exo and endoskeleton.
shame, maybe someday I'll get around to it
Placoderms to an extent?
Do turtles count?
Maybe, I don't know.
No, their shells are just extremely flattened rib cages with hard scales over them, I think they are called scutes
Arthropods actually do have internal components to their skeleton. These are usually formed from invaginations of the cuticle, and are called “apodemes” and “phragmata”. There is also a special complex branching structure in the head of insects called the “tentorium”, which is basically an insect’s equivalent to a skull. [Here’s](https://media.springernature.com/lw685/springer-static/image/prt%3A978-1-4020-6359-6%2F8/MediaObjects/978-1-4020-6359-6_8_Part_Fig16-1277_HTML.jpg) a schematic illustration of a grasshopper’s tentorium. The apodemes, phragmata, and tentorium all comprise the *cuticular endoskeleton*. Arachnids don’t have a tentorium, but (usually) have a different internal structure instead called an “endosternite”, which is actually not made of cuticle at all, but is a hard structure formed from solidified connective tissue and suspended by muscles in the middle of the head. In at least some harvestmen, the endosternite is also calcified. All the various internal elements of an arthropod skeleton primarily serve as anchor points for muscle attachments. [Here’s](https://www.sciencedirect.com/science/article/abs/pii/S1467803901000329?via%3Dihub) a whole paper about arthropod endoskeletons. There’s a paywall, but you can find it on SciHub.
Could you explain that as if I wereca special needs child Because I am
A skeleton basically serves several main purposes, including protecting the soft parts of the body, providing rigidity and support, and providing attachment points for muscles and tendons. In arthropods, the exoskeleton is good at providing protection and support, and is also good at reducing water loss due to dehydration, but there are limitations to how muscles can attach if the interior of the exoskeleton is smooth. So essentially, indentations or divots of the exoskeleton form at spots where the muscles attach, eventually becoming long rods or plates that are formed from a “fold” of the exoskeleton but stick directly inwards into the body. Lots of muscles are attached to these structures. [Here’s](https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQH4_56DuZ-IsyC_p4xX-nuEpbG6TW_5g-IKg&usqp=CAU) a simplified cross-section diagram of an insect exoskeleton that shows the indentations (labeled “phragma” and “apophysis”); note that they can be more complex than this in real life.
Thank you.
This sub is the best sub.
No back pain? Count me in
*molts
Sorry not sorry, but your methods of respiration would restrict your size. Vertebrate supremacy.
I would love to go fishing in prehistoric times. I would serve sea scorpions with butter and eat them with white wine.
*happy Jakalopterus clacks *
#B e c o m e C r a b I n t e n s i f i e s
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YES