Archaeocursor Temporal range: Early Jurassic, | |
---|---|
Holotype femur | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | † Ornithischia |
Genus: | † Archaeocursor Yao et al., 2025 |
Species: | †A. asiaticus |
Binomial name | |
†Archaeocursor asiaticus Yao et al., 2025 | |
Archaeocursor (meaning "old runner") is an extinct genus of basal ornithischian dinosaurs from the Early Jurassic Ziliujing Formation of China. The genus contains a single species, A. asiaticus, known from a single femur. Archaeocursor represents the oldest and most basal ornithischian described from Asia.
The Archaeocursor holotype specimen, L01-HY999, was discovered in 2022 in outcrops of the Ziliujing Formation (Dongyuemiao Member) near Chongqing Central Park in Yubei District of Chongqing Municipality, China. The collection of this bone was part of an operation by the Southeast Sichuan Geological Team to salvage paleontological materials during construction in a residential area, and it is now accessioned in the Chongqing Municipal Bureau of Planning and Natural Resources. The specimen consists of an isolated nearly complete left femur. [1]
The specimen was first mentioned in a paper describing the fossil assemblage of the type locality (named the Yuzhou Biota), which represents a lacustrine ecosystem. Well-preserved specimens of diverse plants, invertebrates, fish, and pliosaurids are also represented in the outcrops. This assemblage represents a faunal turnover shortly following the end-Triassic extinction. The discovery of an ornithischian dinosaur in this context is notable; it likely happened to be washed into the lake after its death. [2]
After being announced in December 2024 as a non-finalized preprint, Yao et al. (2025) described Archaeocursor asiaticus as a new genus and species of early ornithischians based on this fossil specimen. The generic name, Archaeocursor, combines the Latin words archaeo, meaning "archaic" or "old" and cursor, meaning "runner". The specific name, asiaticus, is a Latin word meaning "from Asia". [1]
Archaeocursor is one of the only ornithischians known from the Early Jurassic of Asia, with the armored thyreophoran Yuxisaurus being one of the few others. It is the oldest and earliest-diverging named ornithischian from Asia. [1]
Using histological methods, Yao et al. (2025) determined that the holotype femur likely belonged to an early adult individual that had not yet reached somatic maturity. Using the holotype femur (93 millimetres (3.7 in) long), they estimated the individual's body length at 1 metre (3.3 ft). [1]
In their phylogenetic analyses, Yao et al. (2025) recovered Archaeocursor as an early-diverging member of the Ornithischia, branching crownward of heterodontosaurids as the sister taxon to Eocursor . Eocursor is known from rocks of a similar age in South Africa belonging to the upper Elliot Formation. [3] Yao et al. suggest that the common ancestor of these two genera likely originated in Gondwana before dispersing northward to Laurasia and later East Asia. However, they caution that this hypothesis is tentative, given the fragmentary nature of the Archaeocursor holotype. The results of their phylogenetic analyses are displayed in the cladogram below: [1]
Lesothosaurus is a monospecific genus of ornithischian dinosaur that lived during the Early Jurassic in what is now South Africa and Lesotho. It was named by paleontologist Peter Galton in 1978, the name meaning "lizard from Lesotho". The genus has only one valid species, Lesothosaurus diagnosticus. Lesothosaurus is one of the most completely-known early ornithischians, based on numerous skull and postcranial fossils from the Upper Elliot Formation. It had a simpler tooth and jaw anatomy than later ornithischians, and may have been omnivorous in some parts of the year.
Eoraptor is a genus of small, lightly built, basal sauropodomorph dinosaur. One of the earliest-known dinosaurs and one of the earliest sauropodomorphs, it lived approximately 231 to 228 million years ago, during the Late Triassic in Western Gondwana, in the region that is now northwestern Argentina. The type and only species, Eoraptor lunensis, was first described in 1993, and is known from an almost complete and well-preserved skeleton and several fragmentary ones. Eoraptor had multiple tooth shapes, which suggests that it was omnivorous.
Cryolophosaurus is a genus of large theropod dinosaur known from only a single species Cryolophosaurus ellioti, from the early Jurassic of Antarctica. It was one of the largest theropods of the Early Jurassic, with the subadult being estimated to have reached 6–7 metres (20–23 ft) long and weighed 350–465 kilograms (772–1,025 lb).
Algoasaurus is a genus of sauropod dinosaur from the Berriasian-early Valanginian-age Early Cretaceous Upper Kirkwood Formation of Cape Province, South Africa, specifically near a town called Despatch. Only one species, A. bauri, is known.
Yingshanosaurus is an extinct genus of stegosaurian dinosaurs from the Middle Jurassic of what is now Southwestern China. The genus contains a single species, Yingshanosaurus jichuanensis. It is known from one partial skeleton discovered in 1983 including back, sacrum, and tail vertebrae, forelimb and hindlimb bones, shoulder and hip bones, and several osteoderms including plates and a spine. At 4–5 metres (13–16 ft) long, it was a medium-sized stegosaur. After its discovery and scientific description, the validity of Yingshanosaurus was questioned by some paleontologists who were unaware of the research published on the species in China.
Pisanosaurus is an extinct genus of early dinosauriform, likely an ornithischian or silesaurid, from the Late Triassic of Argentina. It was a small, lightly built, ground-dwelling herbivore, that could grow up to an estimated 1 m (3.3 ft) long. Only one species, the type, Pisanosaurus mertii, is known, based on a single partial skeleton discovered in the Ischigualasto Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina. This part of the formation has been dated to the late Carnian, approximately 229 million years ago.
Heterodontosauridae is a family of ornithischian dinosaurs that were likely among the most basal (primitive) members of the group. Their phylogenetic placement is uncertain but they are most commonly found to be primitive, outside of the group Genasauria. Although their fossils are relatively rare and their group small in numbers, they have been found on all continents except Australia and Antarctica, with a range spanning the Early Jurassic to the Early Cretaceous.
The Ziliujing Formation is a geological formation in China, It is Early Jurassic in age. It is part of the stratigraphy of the Sichuan Basin. The dinosaur Gongxianosaurus and indeterminate theropod material are known from the Dongyuemiao Member of the formation, as well as dinosaur footprints, Zizhongosaurus and indeterminate prosauropods from the Da'anzhai Member. The basal sauropod Sanpasaurus is known from the Maanshan Member. The basal ornithschian Archaeocursor is known from the formation. A possible unnamed stegosaur and the pliosauroid plesiosaur Sinopliosaurus are also known from this formation but they were found an indeterminate member. An unnamed teleosaurid known from a complete skull has also been found in the formation, pending a formal description. The deposition environment during the Da'anzhai Member in the lower Toarcian is thought to have been that of a giant freshwater lake encompassing the whole of the Sichuan basin, around 3 times larger than Lake Superior, coeval with the Toarcian Oceanic Anoxic Event around 183 Ma. The Sinemurian-Pliensbachian boundary event has been recorded on the top of the Dongyuemiao Member, while lower parts of this member are of Earliest Sinemurian age.
Eocursor is genus of basal ornithischian dinosaur that lived in what is now South Africa during the Early Jurassic. Remains of this animal have been found in the Upper Elliot Formation and it is among the most completely known early ornithischians, shedding new light on the origin of the group.
Glacialisaurus is a genus of sauropodomorph dinosaur from the Early Jurassic period of Antarctica. It is known from two specimens; the holotype, a partial tarsus (ankle) and metatarsus, and a partial left femur. The fossils were collected by a team led by paleontologist William R. Hammer during a 1990–91 field expedition to the central region of the Transantarctic Mountains. They come from sedimentary rocks of the Hanson Formation and date to the Pliensbachian stage of the Early Jurassic, around 186 to 182 million years ago. The fossils were described in 2007, and made the basis of the new genus and species Glacialisaurus hammeri. The genus name translates as “icy” or "frozen lizard”, and the specific name honors Hammer.
Kayentachelys is an extinct genus of turtle known only from the "silty facies" of the Lower Jurassic Kayenta Formation in northeastern Arizona on the lands of the Navajo Nation.
Tonganosaurus is a genus of mamenchisaurid sauropod dinosaur, similar to Omeisaurus. It is known from one specimen consisting of twenty vertebrae, a front limb and pectoral girdle, and a complete hind limb with partial hip. It was discovered in the Yimen Formation, China. The horizon of the specimen and the age of the Yimen Formation is controversial. The formation has been divided into three levels, and Tonganosaurus appears to be of late Early Jurassic (Pliensbachian) age. Tonganosaurus is the oldest known member of the mamenchisaurids, being almost 15 million years older than the next-oldest members of the group. It was first named by Li Kui, Yang Chun-Yan, Liu Jian and Wang Zheng-Xin in 2010 and the type species is Tonganosaurus hei.
Diodorus is a genus of silesaurid dinosauromorph that lived during the Late Triassic in what is now Morocco. Fossils were discovered in the Timezgadiouine Formation of the Argana Basin, and were used to name the new genus and species Diodorus scytobrachion. The genus name honors the mythological king Diodorus and the ancient historian Diodorus Siculus; the specific name is ancient Greek for 'leathery arm' and also honors the mythographer Dionysius Scytobrachion. The holotype specimen is a partial dentary bone (front of the lower jaw), and assigned specimens include isolated teeth, two humeri (upper arm bones), a metatarsal (foot bone), and femur (thigh bone).
Laquintasaura is a genus of Venezuelan ornithischian dinosaur containing only the type species Laquintasaura venezuelae. It is known for being one of the most primitive ornithischians in the fossil record, as well as the first dinosaur to have been identified from Venezuela. The name is derived from the La Quinta Formation, where it was discovered, and the feminine Greek suffix for lizard, with the specific name referring to the country of Venezuela. It is known from hundreds of fossil elements, all derived from a single extensive bonebed locality. Initially discovered by French palaeontologists, numerous expeditions have been conducted to excavate from the bonebed, largely led by Marcelo R Sánchez-Villagra. Once thought to represent remains of Lesothosaurus, it was formally named in a 2014 study; much of the abundant material was not yet prepared at the time and research remains ongoing.
Bashanosaurus is an extinct genus of stegosaurian dinosaur from the Middle Jurassic Shaximiao Formation of Yunyang County, China. The genus contains a single species, Bashanosaurus primitivus, known from incomplete skeletons belonging to three individuals. It is one of the basalmost stegosaurs, as well as one of the oldest known stegosaurs, along with Adratiklit, Isaberrysaura, and Thyreosaurus.
Gamatavus is a genus of silesaurid dinosauriform from the Middle Triassic Santa Maria Formation of Dilermando de Aguiar Municipality, Brazil. The genus contains a single species, G. antiquus, known from a partial ilium. Gamatavus represents one of the oldest silesaurids known from South America, alongside the roughly coeval Gondwanax.
Mambachiton is an extinct genus of basal avemetatarsalian from the Middle/Upper Triassic Makay Formation of Madagascar. The genus contains a single species, M. fiandohana, known from a partial skeleton with articulated osteoderms.
Musankwa is an extinct genus of massopodan sauropodomorph dinosaur from the Late Triassic (Norian) Pebbly Arkose Formation of Zimbabwe. The genus contains a single species, M. sanyatiensis, known from a partial leg. Musankwa represents the fourth dinosaur genus to be named from Zimbabwe.
Ahvaytum is an extinct genus of probable basal sauropodomorph saurischian dinosaurs from the Late Triassic Popo Agie Formation of Wyoming, United States. The genus contains a single species, A. bahndooiveche, known from fragmentary hindlimb bones. Ahvaytum represents the oldest known named dinosaur of the ancient Laurasian landmass.