Sauropodomorpha (/ˌsɔːrəˌpɒdəˈmɔːrfə/[3] SOR-ə-POD-ə-MOR-fə; from Greek, meaning "lizard-footed forms") is an extinct clade of long-necked, herbivorous, saurischian dinosaurs that includes the sauropods and their ancestral relatives.

Sauropods generally grew to very large sizes, had long necks and tails, were quadrupedal, and became the largest animals to ever walk the Earth.

The sauropodomorphs were the dominant terrestrial herbivores throughout much of the Mesozoic Era, from their origins in the Late Triassic (approximately 230 Ma) until their decline and extinction at the end of the Cretaceous.

[citation needed] One of the earliest known sauropodomorphs, Saturnalia, was small and slender (1.5 metres, or 5 feet long); but, by the end of the Triassic, they were the largest dinosaurs of their time, and throughout the Jurassic and Cretaceous they kept on growing.

Ultimately the largest sauropods, like Supersaurus, Diplodocus hallorum, Patagotitan, and Argentinosaurus, reached 30–40 metres (98–131 ft) in length, and 60,000–100,000 kilograms (65–110 US short tons) or more in mass.

[citation needed] Initially bipedal, as their size increased they evolved a four-legged graviportal gait adapted only to walking slowly on land, like elephants.

However, sauropodomorphs also share a number of characteristics with the Ornithischia, so a small minority of palaeontologists, like Bakker, have historically placed both sets of herbivores within a group called "Phytodinosauria" or "Ornithischiformes".

Recent cladistic analyses suggest that the clade Prosauropoda, which was named by Huene in 1920 and was defined by Sereno, in 1998, as all animals more closely related to Plateosaurus engelhardti than to Saltasaurus loricatus,[9] is a junior synonym of Plateosauridae as both contain the same taxa.

[12] The phylogenetic analysis of Otero et al., 2015 found Sauropodomorpha to be in a polytomy with Agnosphitys and Theropoda within Eusaurischia, with Herrerasauridae and Eoraptor external to it within Saurischia.

Fossil ISI R277 Panphagia Guaibasaurus Chromogisaurus Saturnalia Pantydraco Thecodontosaurus Nambalia Efraasia Plateosauravus Ruehleia Plateosauridae Riojasauridae Anchisauria Massospondylidae Below is a cladogram of basal sauropodomorpha after Müller, 2019.

Nambalia Arcusaurus Pantydraco Thecodontosaurus Plateosauravus Ruehleia Efraasia Plateosaurus Jaklapallisaurus Macrocollum Unaysaurus Anchisaurus Adeopapposaurus Leyesaurus Sarahsaurus Xingxiulong Massospondylus kaalae Pradhania Massospondylus carinatus Coloradisaurus Glacialisaurus Lufengosaurus Yunnanosaurus Jingshanosaurus Eucnemesaurus Riojasaurus Seitaad Mussaurus Yizhousaurus Meroktenos Aardonyx Sefapanosaurus More derived taxa Comparisons between the scleral rings of several sauropodomorph genera (Diplodocus, Lufengosaurus, Nemegtosaurus, Plateosaurus, and Riojasaurus) and modern birds and reptiles suggest that they may have been cathemeral, active throughout the day at short intervals.