Why might echinoderms make a more appropriate study species for making inferences about humans than other commonly studied species such as drosophila fruit flies?

Echinoderms might make more appropriate inferences about humans than other studied species such as Drosophila fruit flies because like humans, they have a thick epidermis and they evolved from animals with bilaterally symmetrical ancestors.

Moreover, the epidermis consists of cells responsible for the support and maintenance of the skeleton and some pigment cells such as melanin, carotinoids and carotein proteins.  

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