Echinothurioida
Echinothurioida (subclass Euechinoidea, superorder Diadematacea) An order of regular echinoids that have flexible tests and compound ambulacral plates bearing three pairs of pores. The tubercles are non-crenulate. At the present day there are many abyssal forms. They first appeared in the Upper Jurassic.
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Maxilla , max·il·la / makˈsilə/ • n. (pl. max·il·lae / makˈsilē; -ˈsilˌī/ ) Anat. & Zool. the jaw or jawbone, specifically the upper jaw in most vertebrates. I… labrum , labrum
1. In Echinozoa, a lip-like projection of the peristome.
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Echinothurioida