def ender ▁Thomas ▁Henry ▁H ux ley ▁proposed ▁that ▁birds ▁were ▁descend ants ▁of ▁din osa urs . ▁He ▁c ited ▁ske let al ▁similar ities , ▁particularly ▁among ▁din osa urs , ▁the ▁" first ▁bird " — Arch ae opter y x — and ▁modern ▁birds . ▁ ▁However , ▁in ▁ 1 9 2 6 , ▁Ger hard ▁Heil mann ▁wrote ▁his ▁influ ential ▁book ▁The ▁Origin ▁of ▁Bird s , ▁in ▁which ▁he ▁dismiss ed ▁the ▁din osa ur – bird ▁link , ▁based ▁on ▁the ▁din osa urs ' ▁supposed ▁lack ▁of ▁a ▁fur cul a . ▁There after , ▁the ▁accepted ▁hypothesis ▁was ▁that ▁birds ▁evol ved ▁from ▁cro c ody l omorph ▁and ▁the cod ont ▁ancest ors , ▁rather ▁than ▁from ▁din osa urs . ▁This ▁removed ▁din osa urs ▁from ▁a ▁central ▁role ▁in ▁deb ates ▁about ▁the ▁origin ▁of ▁living ▁species , ▁and ▁may ▁have ▁contributed ▁to ▁the ▁decl ine ▁of ▁academic ▁interest ▁in ▁din osa ur ▁evolution . ▁ ▁This ▁situation ▁pers isted ▁until ▁ 1 9 6 4 , ▁when ▁John ▁Ost rom ▁discovered ▁a ▁small ▁car n iv orous ▁din osa ur ▁which ▁he ▁named ▁De in ony chus ▁ant ir rh opus , ▁a ▁ther op od ▁whose ▁ske let al ▁res embl ance ▁to ▁birds ▁seemed ▁un m ist ak able . ▁This ▁led ▁Ost rom ▁to ▁argue ▁that ▁H ux ley ▁had ▁been ▁right , ▁and ▁that ▁birds ▁had ▁indeed ▁evol ved ▁from ▁din osa urs .