▁to ▁its ▁origin ▁from ▁the ▁Z ang j ia z hu ang ▁Qu ar ry . ▁ ▁Description ▁ ▁The ▁hum er us ▁Z J Z - 5 7 ▁( when ▁viewed ▁from ▁the ▁front ) ▁measures ▁ ▁long , ▁ ▁wide ▁at ▁the ▁top , ▁ ▁wide ▁at ▁mid sh aft , ▁and ▁ ▁wide ▁at ▁the ▁bottom . ▁It ▁can ▁be ▁identified ▁by ▁the ▁extreme ▁width ▁of ▁its ▁top ▁end ▁compared ▁to ▁other ▁tit an osa urs , ▁which ▁is ▁ 0 . 5 5 ▁times ▁its ▁whole ▁length . ▁This ▁figure ▁is ▁closest ▁to ▁the ▁ 0 . 4 9 ▁of ▁Salt as aur us ▁and ▁the ▁ 0 . 5 6 ▁of ▁O pis th oco el ica ud ia . ▁Con sequently , ▁the ▁robust ness ▁index ▁( RI ) ▁( the ▁ratio ▁between ▁the ▁average ▁of ▁the ▁three ▁width ▁measurements ▁and ▁the ▁length ) ▁is ▁also ▁quite ▁high , ▁at ▁ 0 . 3 9 ; ▁Salt as aur us ▁has ▁an ▁R I ▁of ▁ 0 . 3 5 , ▁while ▁O pis th oco el ica ud ia ▁has ▁an ▁R I ▁of ▁ 0 . 3 8 . ▁The ▁width ▁ar ises ▁from ▁the ▁inner ▁edge ▁of ▁the ▁b one , ▁which ▁is ▁ang led ▁more ▁sharp ly ▁in wards ▁at ▁the ▁top ▁end ▁of ▁the ▁b one ▁than ▁the ▁bottom ▁end . ▁ ▁Further ▁below , ▁the ▁sh aft ▁of ▁the ▁b one ▁is ▁cyl ind rical ▁in ▁cross - section , ▁with