Table 1. Specimens sampled for histological analysis in this study.

All samples were derived from femoral mid-shafts in areas devoid of bone scars indicative of muscle attachments, including for those samples indicated with an * in which the element was partially preserved. Samples extracted from holotypes that consist of a single individual are indicated by a superscript H. Except for these singleton holotypes, most samples were drawn from larger specimens than those previously studied. Samples for Hyperodapedon and Herrerasaurus were extracted from the largest available specimens, which are equivalent in size to previously studied elements [15–19]. Data on habitat, diet, and estimated body mass are derived from Martínez and colleagues [6,7]. Institutional Abbreviations: PVSJ (División de Paleontología de Vertebrados del Museo de Ciencias Naturales y Universidad Nacional de San Juan, San Juan, Argentina).

Taxon	Specimen Number	Femur Length (cm)	Habitat	Diet	Mass (kg)
Archosauromorpha
Hyperodapedon sanjuanensis	PVSJ 574	21.1	Terrestrial	Herbivore	25–250 kg
Archosauriformes
Proterochampsa barrionuevoi	PVSJ 606	18.7	Aquatic	Carnivore	25–250 kg
Pseudochampsa ischigualastensis H	PVSJ 567	18.1	Aquatic	Carnivore	<25 kg
Crurotarsi
Sillosuchus longicervix H	PVSJ 085	46.5	Terrestrial	Carnivore?	25–250 kg
Saurosuchus galilei	PVSJ 047	28.5*	Terrestrial	Carnivore	>250 kg
Crocodylomorpha
Trialestes romeri	PVSJ 368	42.3	Terrestrial	Carnivore	25–250 kg
Dinosauria
Saurischia
Theropoda
Eodromaeus murphi H	PVSJ 561	16.0	Terrestrial	Carnivore	<25 kg
Sauropodomorpha
Eoraptor lunensis	PVSJ 559	14.0*	Terrestrial	Omnivore?	< 25 kg
Chromogisaurus novasi H	PVSJ 845	16.0*	Terrestrial	Herbivore	<25 kg
Herrerasauridae
Herrerasaurus ischigualastensis	PVSJ 614	24*	Terrestrial	Carnivore	25–250 kg
Sanjuansaurus gordilloi H	PVSJ 605	39.5*	Terrestrial	Carnivore	25–250 kg
Cynodontia
Exaeretodon argentinus	PVSJ 38–2002	21.7	Terrestrial	Herbivore	25–250 kg