Pronunciation: ah-VAY-tum
Meaning: Long ago
Author/s: Lovelace et al. (2025)
Synonyms: None known
First Discovery: Wyoming, USA
Discovery Chart Position: #1159
Around 200 million years ago, Earth's landmasses were all connected as a giant supercontinent called Pangaea, meaning "all land", surrounded by Panthalassa, meaning "all sea". Over time, Pangaea began to break apart, giving rise to two major landmasses: Laurasia (present-day North America, Europe, and most of Asia) in the north and Gondwana (present-day South America, Africa, Antarctica, Australia, Arabia, and the Indian subcontinent) in the south. Fossil evidence has long indicated that dinosaurs originated in the latter before spreading to the former. But the Laurasian Ahvaytum and fossil dinosaur-like footprints in slightly older rocks of the same area put the kibosh on that theory.
At 230 million years old, Ahvaytum is the oldest dinosaur from North America and the oldest Laurasian dinosaur, comparable in age to the earliest known from Gondwana, and lived during or soon after a period of immense climate change known as the Carnian pluvial episode. During that time, circa 234-232 mya, the switch from arid to tropical and then back to arid wreaked havoc on the fauna, and key herbivores such as dicynodonts and rhynchosaurs went extinct, leaving opportunistic, two-legged, omnivorous dinosaurs to explode in diversity and ecological importance and dominate the vacant niches in number if not size.
Like all early dinosaurs, Ahvaytum was small, measuring just over 1 metre from snout-tip to tail and 30cm at the hips, but likely had a smidgen room for growth, as the only known specimen isn't fully mature. Its fossils were initially described as the property of an early theropod dinosaur by Fitch, Lovelace and Stockerand in 2020. But it became the first new dinosaur of 2025 when it was named and described as a probable early sauropodomorph on January 1st of that year.
(Long Ago Dinosaur)Etymology
In the language of the Eastern Shoshone Tribe, Ahvaytum means "long ago", referring to the specimen's old age.
The species epithet, bahndooiveche (bon-do-ee-vee-chee), also in Shoshone, means "water’s young handsome man" in reference to the colourful salamanders found in the region, but also means "dinosaur". This name, created by Eastern Shoshone students, educators, and tribal Elders, is intended to honour the Eastern Shoshone people, their language, and the land to which they belong.
ZooBank registry: urn:lsid:zoobank.org:pub:538C156C-5CC1-4706-8D8A-FFA6757A6590.
Discovery
The remains of Ahvaytum were discovered in the Popo Agie Formation (Chugwater Group) at the "Garrett’s Surprise" locality, 1 km south of the confluence of the East Fork of the Wind River and Spear Creek, Wyoming, USA, by undergraduate field assistant Garrett Johnson in 2013.
The holotype (UWGM 1975) is a left ankle.
Referred material includes the top end of a left thigh bone (UWGM 7549).
Preparator
Brandon Price.
