| Iyuku Temporal range: Early Cretaceous, | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | † Ornithischia |
| Clade: | † Ornithopoda |
| Clade: | † Iguanodontia |
| Genus: | † Iyuku Forster et al., 2022 |
| Type species | |
| †Iyuku raathi Forster et al., 2022 | |
Iyuku (meaning "hatchling", pronounced "eye-yoo-koo") is a genus of iguanodontian dinosaur from the Early Cretaceous Kirkwood Formation of South Africa. The type species is Iyuku raathi. [1]
Iykuku is known from a bonebed mostly containing the remains of at least 27 (inferred from non-overlapping parts of the left femora) juvenile and hatchling individuals, an occurrence never before reported. These bonebeds were excavated during three expeditions between 1995 and 1999. The remains were known as the "Kirkwood taxon" since at least 2012, until the remains were determined to represent a new genus and species in 2022, named Iyuku raathi. [2] The holotype specimen, AM 6067, consists of an incomplete, semi-articulated skeleton, including a partial skull, vertebrae, scapulae, pelvic girdle, both legs, and ribs. The generic name "Iyuku", is derived from the Xhosa word for "hatchling", in reference to the immature status of the specimens. The specific name, "raathi", honors South African paleontologist Mike Raath. [1]
The describers assigned Iyuku to the Iguanodontia. A 2015 PhD dissertation that included the then unnamed species in a cladistic analysis found it to be a member of the basal iguanodontian family Dryosauridae, with the parsimony analysis recovering Iyuku and Dysalotosaurus as sister taxa. [3] Forster et al. (2022) referenced this study but noted that the early ontogenetic stage of most of the material of Iyuku presents a major problem in placing it into a phylogenetic analysis and assigned it to Iguanodontia without providing an analysis. [1] Subsequently, four phylogenetic analyses conducted by Poole (2022) recovered Iyuku as the sister taxon to Dysalotosaurus within Dryosauridae. The cladogram below displays the results of a phylogenetic analysis by Poole (2022): [4]
| Iguanodontia |
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Fossil material from Iyuku represents at least four size classes, including three juvenile phases of growth (with the smallest likely representing the post-hatching stage) and the fourth, larger stage, likely a subadult. Two different estimates of total length were provided for an incomplete tibia of a subadult specimen collected from an unknown location in the Kirkwood cliffs: either 35 cm (14 in) or at least 42 cm (17 in) long, i.e., four or five times the length of the largest juvenile tibia from the quarry site. Fossil material from the quarry site includes mostly isolated bones (with only five instances of articulation) of hatchling to juvenile individuals of varying size in a 20–30 cm thick horizon, preserved with no apparent preferred orientation of long bones. [1]
Forster et al. (2022) noted the similarity of this finding to the reported preservation of the juvenile remains of Orodromeus , Maiasaura , and Hypacrosaurus , which might represent aggradations of mortality near nesting sites. Although the remains of Iyuku were not found in association with nests or eggshells, Forster et al. (2022) considered it possible that the concentrations of young individuals of this species represent seasonal attrition at or near a nesting site, with the scattering of bones likely caused by trampling prior to burial or bioturbation shortly after interment. Bone histology of multiple young individuals reveals rest lines indicative of temporary arrests in bone deposition, hypothesized by Forster et al. (2022) as caused by repeated, possibly environmentally induced stress during the early stages of ontogeny in these individuals, such as dry and drought-like conditions and/or repeated periods of extreme heat. [1]
Sedimentological analysis of the holotype assemblage suggests it came from a horizon transitioning into a drier climate. [1] Other animals from the Kirkwood Formation include the sauropod Algoasaurus , the stegosaur Paranthodon , the ornithomimosaur Nqwebasaurus , and several other unnamed dinosaurs.
Mussaurus is a genus of herbivorous sauropodomorph dinosaur that lived in southern Argentina during the Sinemurian stage of the Early Jurassic. It receives its name from the small size of the skeletons of juvenile and infant individuals, which were once the only known specimens of the genus. However, since Mussaurus is now known from adult specimens, the name is something of a misnomer.
Ornithomimosauria are theropod dinosaurs which bore a superficial resemblance to the modern-day ostrich. They were fast, omnivorous or herbivorous dinosaurs from the Cretaceous Period of Laurasia, as well as Africa and possibly Australia. The group first appeared in the Early Cretaceous and persisted until the Late Cretaceous. Primitive members of the group include Nqwebasaurus, Pelecanimimus, Shenzhousaurus, Hexing and Deinocheirus, the arms of which reached 2.4 m (8 feet) in length. More advanced species, members of the family Ornithomimidae, include Gallimimus, Struthiomimus, and Ornithomimus. Some paleontologists, like Paul Sereno, consider the enigmatic alvarezsaurids to be close relatives of the ornithomimosaurs and place them together in the superfamily Ornithomimoidea.
Styracosaurus is a genus of herbivorous ceratopsian dinosaur from the Cretaceous Period, about 75.5 to 74.5 million years ago. It had four to six long parietal spikes extending from its neck frill, a smaller jugal horn on each of its cheeks, and a single horn protruding from its nose, which may have been up to 60 centimeters long and 15 centimeters wide. The function or functions of the horns and frills have been debated for many years.
Einiosaurus is a genus of herbivorous centrosaurine ceratopsian dinosaur from the Upper Cretaceous of northwestern Montana. The name means 'buffalo lizard', in a combination of Blackfeet Indian eini and Latinized Ancient Greek sauros; the specific name (procurvicornis) means 'with a forward-curving horn' in Latin. Einiosaurus is medium-sized with an estimated body length at 4.5 metres (15 ft).
The Iguanodontia are a clade of herbivorous dinosaurs that lived from the Middle Jurassic to Late Cretaceous. Some members include Camptosaurus, Dryosaurus, Iguanodon, Tenontosaurus, and the hadrosaurids or "duck-billed dinosaurs". Iguanodontians were one of the first groups of dinosaurs to be found. They are among the best known of the dinosaurs, and were among the most diverse and widespread herbivorous dinosaur groups of the Cretaceous period.
Sinornithomimus is a genus of ornithomimid that lived in Asia during the Late Cretaceous period. The first remains were found in 1997, in the Late Cretaceous strata of the Ulansuhai Formation located at Alshanzuo Banner, Inner Mongolia Autonomous Region, Northern China.
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.
Dysalotosaurus is a genus of herbivorous iguanodontian dinosaur. It was a dryosaurid iguanodontian, and its fossils have been found in late Kimmeridgian-age rocks of the Tendaguru Formation of Lindi Region in Tanzania. The type and only species of the genus is D. lettowvorbecki. This species was named by Hans Virchow in 1919 in honor of the Imperial German Army Officer, Paul von Lettow-Vorbeck. For much of the 20th century the species was referred to the related and approximately contemporary genus Dryosaurus, but newer studies reject this synonymy.
Pararhabdodon is a genus of tsintaosaurin hadrosaurid dinosaur, from the Maastrichtian-age Upper Cretaceous Tremp Group of Spain. The first remains were discovered from the Sant Romà d’Abella fossil locality and assigned to the genus Rhabdodon, and later named as the distinct species Pararhabdodon isonensis in 1993. Known material includes assorted postcranial remains, mostly vertebrae, as well as maxillae from the skull. Specimens from other sites, including remains from France, a maxilla previously considered the distinct taxon Koutalisaurus kohlerorum, an additional maxilla from another locality, the material assigned to the genera Blasisaurus and Arenysaurus, and the extensive Basturs Poble bonebed have been considered at different times to belong to the species, but all of these assignments have more recently been questioned. It was one of the last non-avian dinosaurs known from the fossil record that went extinct during the Cretaceous-Paleogene extinction event.
Aniksosaurus is a genus of dinosaur from what is now Chubut Province, Argentina. It was a theropod, specifically a coelurosaur, which lived in the Cenomanian to Turonian of the Cretaceous period, between 96-91 million years ago. The type species, Aniksosaurus darwini, was formally described from the Bajo Barreal Formation of the Golfo San Jorge Basin by Rubén Dario Martínez and Fernando Emilio Novas in 2006; the name was first coined in 1995 and reported in the literature in 1997. The specific epithet honors Charles Darwin who visited Patagonia in 1832/1833 during the Voyage of the Beagle.
Zalmoxes is a genus of rhabdodontid ornithopod dinosaur from the Maastrichtian age of the Late Cretaceous in what is now Romania. The genus is known from specimens first named as the species Mochlodon robustum in 1899 by Franz Nopcsa before being reclassified as Rhabdodon robustum by him in 1915. In 1990, this name was corrected to Rhabdodon robustus by George Olshevsky and, in 2003, the species was once more reclassified as the type species Zalmoxes robustus. Zalmoxes refers to the Thracian deity Zalmoxis and robustus refers to the robustness of the remains. Also in 2003, another species was named, Zalmoxes shqiperorum, named for the Albanian name for Albanians.
Nqwebasaurus is a basal coelurosaur and is the basal-most member of the coelurosaurian clade Ornithomimosauria from the Early Cretaceous of South Africa. The name Nqwebasaurus is derived from the Xhosa word "Nqweba" which is the local name for the Kirkwood district, and "thwazi" is ancient Xhosa for "fast runner". Currently it is the oldest coelurosaur in Africa and shows that basal coelurosaurian dinosaurs inhabited Gondwana 50 million years earlier than previously thought. The type specimen of Nqwebasaurus was discovered by William J. de Klerk who is affiliated with the Albany Museum in Grahamstown. It is the only fossil of its species found to date and was found in the Kirkwood Formation of the Uitenhage Group. Nqwebasaurus has the unofficial nickname "Kirky", due to being found in the Kirkwood.
The Kirkwood Formation is a geological formation found in the Eastern and Western Cape provinces in South Africa. It is one of the four formations found within the Uitenhage Group of the Algoa Basin – its type locality – and in the neighbouring Gamtoos Basin. Outcrops of the Kirkwood are also found along the Worcester-Pletmos, Herbertsdale-Riversdale, Heidelberg-Mossel Bay, and Oudtshoorn-Gamtoos basin lines. At these basins the Kirkwood Formation underlies the Buffelskloof Formation and not the Sundays River Formation.
Coronosaurus is a genus of centrosaurine ceratopsian dinosaurs which lived in the Late Cretaceous, in the middle Campanian stage. Its remains, two bone beds, were discovered by Phillip J. Currie in the Oldman Formation of Alberta, Canada, and its type and only species, Coronosaurus brinkmani, was first described in 2005, as a new species within the genus Centrosaurus. Later studies questioned the presence of a direct relationship, and in 2012 it was named as a separate genus. Coronosaurus means "crowned lizard", coming from "corona", Latin for crown, and "sauros", Greek for lizard; this name refers to the unique, crown-like shape of the horns on the top of its frill.
Yulong is an extinct genus of derived oviraptorid theropod dinosaur known from the Late Cretaceous Qiupa Formation of Henan Province, central China. It contains a single species, Yulong mini. It is known from many juvenile specimens that represent some of the smallest known oviraptorids and also a single subadult specimen.
Laquintasaura is a genus of Venezuelan ornithischian dinosaur containing only the type species Laquintasaura venezuelae. The species was the first dinosaur to have been identified from Venezuela. It is known from extensive remains, all from a singular bonebed locality which has been sampled for specimen blocks over the course of several expeditions, largely led by Marcelo R Sánchez-Villagra. A small, very primitive animal, it is known for its distinct dental anatomy and for being one of the earliest and most primitive ornithischians in the fossil record. Taxonomic uncertainty has led to conflicting theories that it is either as the base of Ornithischia or at the base of the subgroup Thyreophora. In either model, its dating to around 200 million years ago, at the start of the Jurassic, existence in equatorial latitudes, and primitive nature make it a key view into early ornithischian evolution. It's thought that Laquintasaura would've lived in groups and had a possible omnivorous diet, living on a seasonal alluvial plain and being preyed about by the contemporary Tachiraptor.
Eousdryosaurus is a genus of basal iguanodontian dinosaur known from a partial skeleton discovered in Upper Jurassic rocks in western Portugal. The type, and only species, is Eousdryosaurus nanohallucis, named and described in 2014.
The Basturs Poble bonebed is a mega-bonebed of hadrosaur dinosaur fossils, discovered in Catalonia, Spain. Hundreds of hadrosaur fossils have been found at the site, which would have been on a large island during the Late Cretaceous when the animals preserved were alive. Despite the enormous amount of specimens, taxonomically informative material has been scarce at the site, leading to extensive debate as to its nature. The number of species present, age of the individuals present in the sample, and taxonomic identity of the remains have been the primary matters of debate. Previous considered to represent Koutalisaurus, Pararhabdodon, or multiple, perhaps dwarf species, it is currently thought that a single, indeterminate species of lambeosaurine was present at the site, and that individuals of many different ages were present.
Thanatotheristes is a genus of tyrannosaurid dinosaur from the Late Cretaceous of Laramidia, approximately 80.1-79.5 Ma. Thanatotheristes contains only one species, T. degrootorum. Fossils of this taxon are found in the Foremost Formation of Alberta, Canada, coexisting with medium-sized ceratopsids like Xenoceratops foremostensis and small pachycephalosaurids like Colepiocephale lambei.
Iani is an extinct genus of rhabdodontomorph iguanodontian dinosaur from the Late Cretaceous Cedar Mountain Formation of Utah, United States. The genus contains a single species, I. smithi, known from a partial skeleton including the skull. Its discovery serves as a link between the genus Tenontosaurus and the Rhabdodontidae, with both along with Iani being members of the clade Rhabdodontomorpha.
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