▁unusual ▁for ▁a ▁di pl od oc id ; ▁it ▁is ▁compar atively ▁sl ender ▁because ▁of ▁the ▁rapidly ▁decre asing ▁height ▁of ▁the ▁verte br al ▁sp ines ▁with ▁increasing ▁distance ▁from ▁the ▁h ips . ▁A pat osa urus ▁also ▁had ▁very ▁long ▁rib s ▁compared ▁to ▁most ▁other ▁di pl od oc ids , ▁giving ▁it ▁an ▁unus ually ▁deep ▁ch est . ▁As ▁in ▁other ▁di pl od oc ids , ▁the ▁tail ▁transformed ▁into ▁a ▁wh ip - like ▁structure ▁towards ▁the ▁end . ▁ ▁The ▁lim b ▁b ones ▁are ▁also ▁very ▁robust . ▁Within ▁A pat osa ur inae , ▁the ▁sc ap ula ▁of ▁A pat osa urus ▁l ou is ae ▁is ▁intermediate ▁in ▁morph ology ▁between ▁those ▁of ▁A . ajax ▁and ▁Br ont osa urus ▁exc els us . ▁The ▁arm ▁b ones ▁are ▁st out , ▁so ▁the ▁hum er us ▁of ▁A pat osa urus ▁res emb les ▁that ▁of ▁Cam ar as aur us , ▁as ▁well ▁as ▁Br ont osa urus . ▁However , ▁the ▁hum eri ▁of ▁Br ont osa urus ▁and ▁A . ajax ▁are ▁more ▁similar ▁to ▁each ▁other ▁than ▁they ▁are ▁to ▁A . lou is ae . ▁In ▁ 1 9 3 6 ▁Charles ▁Gil more ▁noted ▁that ▁previous ▁reconst ru ctions ▁of ▁A pat osa urus ▁for el im bs ▁err one ously ▁proposed ▁that ▁the ▁radius ▁and ▁ul na ▁could ▁cross ; ▁in ▁life ▁they ▁would ▁have ▁remained ▁parallel . ▁A