Table 1. Major (35+) hindlimb muscles of Archosauria, with names for homologous muscles in Crocodylia and Aves/Phasianidae and corresponding abbreviations used here.

Suspected main “actions” are listed. Moment arms about toe joints were not studied so muscles such as the EDB and FDB were not analyzed in this study. Different homologies of the EDL/TA and FDL/FHL have been proposed recently (50), but, as their moment arms were similar, these would not fundamentally alter our results or conclusions.

Muscles (Crocodylia)	Abbreviation	Muscles (Aves/Phasianidae)	“Main” action
M. caudofemoralis longus	CFL	M. caudofemoralis pars caudalis	Hip extensor
M. caudofemoralis brevis	CFB	M. caudofemoralis pars pelvica	Hip extensor
M. iliofibularis	ILFB	M. iliofibularis	Hip extensor/knee flexor
M. adductor femoris 1	ADD1	M. puboischiofemoralis medialis	Hip adductor/hip extensor
M. adductor femoris 2	ADD2	M. puboischiofemoralis lateralis	Hip adductor/hip extensor
M. flexor tibialis internus 1	FTI1	Lost between Avialae-Aves	Hip extensor/knee flexor
M. flexor tibialis internus 2	FTI2	Lost in Dinosauromorpha—not reconstructed	Hip extensor/knee flexor
M. flexor tibialis internus 3	FTI3	M. flexor cruris medialis	Hip extensor/knee flexor
M. flexor tibialis internus 4	FTI4	State in fossil taxa ambiguous— not reconstructed	Hip extensor/knee flexor
M. flexor tibialis externus	FTE	M. flexor cruris lateralis pars pelvica	Hip extensor/knee flexor
State in fossil taxa ambiguous—not reconstructed	-	M. flexor cruris lateralis pars accessoria	Hip extensor
M. ischiotrochantericus	ISTR	M. ischiofemoralis	Hip extensor/hip lateral rotator
M. ambiens 1	AMB1	M. ambiens	Hip flexor/knee extensor
M. ambiens 2	AMB2	Absent; presumed autapomorphy of Crocodylia	Hip flexor/knee extensor
M. iliotibialis 1	IT1	M. iliotibialis cranialis	Hip flexor/knee extensor
M. iliotibialis 2	IT2	M. iliotibialis lateralis pars preacetabularis	Hip flexor/knee extensor
M. iliotibialis 3	IT3	M. iliotibialis lateralis pars postacetabularis	Hip extensor/knee extensor
M. puboischiofemoralis externus 1	PIFE1	M. obturatorius lateralis	Hip flexor/hip lateral rotator
M. puboischiofemoralis externus 2	PIFE2	M. obturatorius medialis	Hip flexor/hip lateral rotator
M. puboischiofemoralis externus 3	PIFE3	Lost between Avialae-Aves	Hip flexor/hip lateral rotator
M. puboischiofemoralis internus 1	PIFI1	M. iliofemoralis internus	Hip flexor/hip medial rotator
M. puboischiofemoralis internus 2	PIFI2	M. iliotrochantericus cranialis	Hip flexor/hip medial rotator
State in fossil taxa ambiguous—not reconstructed	-	M. iliotrochantericus medius	Hip flexor/hip medial rotator
M. iliofemoralis	IF	M. iliofemoralis externus	Hip abductor
Evolved in Dinosauromorpha	ITC	M. iliotrochantericus caudalis	Hip abductor/hip medial rotator
M. femorotibialis externus	FMTE	M. femorotibialis lateralis	Knee extensor
State in fossil taxa ambiguous—not reconstructed	-	M. femorotibialis intermedius	Knee extensor
M. femorotibialis internus	FMTI	M. femorotibialis medialis	Knee extensor
M. gastrocnemius lateralis	GL	M. gastrocnemius (pars) lateralis	Knee flexor/ankle plantarflexor
M. gastrocnemius medialis	GM	M. gastrocnemius (pars) medialis	Ankle plantarflexor
State in fossil taxa ambiguous—not reconstructed	-	M. gastrocnemius (pars) intermedius	Ankle plantarflexor
M. extensor digitorum longus	EDL	Split into M. tibialis cranialis— caput femorale and caput tibiale in Aves	Ankle dorsiflexor (knee extensor?)
M. extensor hallucis longus	EHL	M. extensor hallucis longus	Ankle dorsiflexor
M. extensor digitorum brevis	EDB	Ancestral TA and EDB fused in Aves to form M. extensor digitorum longus; EDB not reconstructed for fossils	Toe extensor
M. tibialis anterior	TA		Ankle dorsiflexor
M. flexor digitorum longus	FDL	M. flexor digitorum longus	Ankle plantarflexor/toe flexor
M. flexor hallucis longus	FHL	M. flexor hallucis longus	Ankle plantarflexor
M. flexor digitorum brevis	FDB	State in fossil taxa ambiguous— not reconstructed	Toe flexor
M. pronator profundus	PP	Lost in Dinosauromorpha—not reconstructed	Tibiofibular rotator
M. interosseus cruris	IC	Lost in Neotheropoda (only M. popliteus part left)—not reconstructed	Tibiofibular rotator
M. fibularis longus	FL	M. fibularis longus	Ankle plantarflexor
M. fibularis brevis	FB	M. fibularis brevis	Ankle dorsiflexor?