arthrostracous

Likely from taxonomic name Arthrostraca +‎ -ous; by surface analysis, arthro-, from Ancient Greek ἄρθρον (árthron, “joint”) + ὄστρακον (óstrakon, “shell”) + -ous^[1]

arthrostracous (not comparable) (rare, zoology)

1. Pertaining to the Arthrostraca, an obsolete grouping of crustaceans with segmented thoraxes and abdomens, bearing seven pairs of thoracic legs; included in this group are the isopods and amphipods.^[1]
   • 1889, William Dwight Whitney, The century dictionary: An encyclopedic lexicon of the english language‎^[2], page 1394:

     The Cumacea resemble the arthrostracous Crustacea in having eyes without a movable stalk; but they closely resemble the Schizopoda in the form of the body, thus corresponding with the lower developmental stages of the decapodous crustaceans.

   • 1853, Quarterly journal of microscopical science.‎^[3], page 375:

     In the important paper already mentioned, Hansen (J03) gives reason for believing that the labial segment in insects was primitively a trunk-segment, and has become secondarily associated with the head, like the segment that bears the maxillipeds in the arthrostracous Crustacea

   • 1886, E Ray Lankester, XXXI.—Professor Claus and the classification of the Arthropoda‎^[4], page n3:

     [...] and have considered the possibility of their derivation from either the Arthrostracous Crustacea or the tracheate Arachnida.

• Edriophthalma on Wikipedia.Wikipedia
• “Arthrostraca”, in Merriam-Webster Online Dictionary, Springfield, Mass.: Merriam-Webster, 1996–present.