▁basic ▁types ▁of ▁n ass ell arian ▁ske let ons . ▁The ▁first ▁is ▁formed ▁from ▁the ▁connection ▁of ▁three ▁el ong ate ▁sp ic ules ▁at ▁a ▁central ▁point . ▁The ▁three ▁sp ic ules ▁are ▁arranged ▁in ▁a ▁single ▁plane ▁so ▁that ▁they ▁are ▁ 1 2 0 ▁degrees ▁apart ▁from ▁each ▁other . ▁This ▁is ▁typically ▁referred ▁to ▁as ▁a ▁“ tri pod ” ▁structure . ▁The ▁second ▁ske leton ▁type ▁common ▁in ▁n ass ell ari ans ▁is ▁the ▁a for ement ioned ▁con ical , ▁por ous ▁ske leton . ▁The ▁third ▁type ▁is ▁of ▁a ▁ring ▁surrounding ▁a ▁l att iced ▁shell . ▁These ▁three ▁ske leton ▁types ▁can ▁be ▁mixed ▁and ▁matched ▁to ▁create ▁seven ▁ske leton ▁categories ▁in ▁n ass ell ari ans . ▁Even ▁the ▁simplest ▁class ifications ▁of ▁n ass ell arian ▁morph ology ▁is ▁complicated ▁because ▁of ▁the ▁wide ▁variety ▁of ▁morph ologies ▁in ▁the ▁n ass ell arian ▁order ▁even ▁when ▁compared ▁with ▁their ▁sister ▁group , ▁the ▁sp um ell ari ans . ▁The ▁inn ate ▁nature ▁of ▁the ▁n ass ell arian ▁geometry ▁l ends ▁itself ▁to ▁divers ity , ▁which ▁may ▁be ▁one ▁of ▁the ▁factors ▁leading ▁to ▁the ▁rapid ▁divers ification ▁of ▁the ▁n ass ell ari ans ▁in ▁comparison ▁to ▁the ▁sp um ell ari ans ▁during ▁the ▁C en oz o ic . ▁ ▁Many ▁n ass ell ari ans ▁are ▁segment ed , ▁meaning ▁there ▁are ▁circular ▁ske let al ▁divisions ▁that ▁exist ▁equ