Dinosauria

Megacephalosaurus eulerti reconstructed skull in the Rocky Mountain Dinosaur Resource Center, Woodland Park, Colorado.

Graph of relative Dinosaur fossil populations from each period of geologic time in the Mesozoic, ordered by major clade

Holotype skull of the centrosaurine ceratopsian dinosaur Diabloceratops eatoni from the Late Cretaceous (Campanian) of the Wahweap Formation, Grand Staircase-Escalante National Monument, Utah. Photograph by Nick Longrich, 2023.

Fossil of Mei long (holotype), on temporary display at the Shanghai Natural History Museum as part of the exhibition "China's Dinosaur World". Shot on July 22, 2025.

Sidersaura is a rebbachisaurid sauropod dinosaur from the Late Cretaceous of Argentina. Rebbachisaurids are the last known dipldocoids, and lived alongside the titanosaurs until fairly late in the Cretaceous before disappearing from the fossil record, presumably going extinct. They have long tails and relatively short necks, by sauropod standards. Sidersaura one of the most recent rebbachisaurids yet found, living in the Cenomanian–Turonian ages of the Late Cretaceous. It was large for a rebbachisaurid, growing to about 20 m in length.

Diagram depicting the currently named Dinosauria from the Late Cretaceous Allen Formation of Argentina. Dinosaur taxa: Aeolosaurus sp. → Salitral Moreno locality, Río Negro Province.[1] Length = 15 meters.[2] Austroraptor cabazai → Santa Rosa Basin locality, Río Negro Province.[3][4] Length = 6 meters.[2] Bonapartenykus ultimus → Salitral Ojo de Agua locality, Río Negro Province.[5] Length = 2.5 meters.[5] Bonapartesaurus rionegrensis → Salitral Moreno locality, Río Negro Province.[6] Length = ∼6 meters.[1] Bonatitan reigi → Salitral de Santa Rosa locality, Río Negro Province.[7] Length = Extrapolated after relatives. Kelumapusaura machi → Cerro Matadero locality, Río Negro Province.[8] 9 meters.[8] Lamarqueavis australis → Cerro Tortugas locality, Río Negro Province.[9] Length = ∼House sparrow-sized.[9] Lapampasaurus cholinoi → Islas Malvinas locality, La Pampa Province.[10] Length = ∼7 meters.[2] Limenavis patagonica → Salitral Moreno locality, Río Negro Province.[11] Length = Extrapolated after relatives. Menucocelsior arriagadai → Salitral Ojo de Agua locality, Río Negro Province. Niebla antiqua → Cerro Matadero locality, Río Negro Province.[12] Length = 4.5 meters.[12] Panamericansaurus schroederi → Bodega Familia Schroeder locality, Neuquén Province.[13] Length = 11 meters.[2] Patagopelta cristata → Salitral Moreno locality, Río Negro Province. Quilmesaurus curriei → Salitral Ojo de Agua locality, Río Negro Province.[14] Length = 5.3 meters.[12] Rocasaurus muniozi → Salitral Moreno locality, Río Negro Province.[15] Length = Extrapolated after relatives. Excluded taxa: Willinakaqe salitralensis is considered a nomen dubium,[16] and its paratype has been reassigned to Bonapartesaurus rionegrensis.[6] Laplatasaurus araukanicus has been restricted to its lectotype which hails from the Anacleto Formation.[17] Abelisaurus comahuensis could either belong to the Allen or Anacleto formations.[12] Pellegrinisaurus powelli could either belong to the Allen or Anacleto formations.[18][19] References ↑ (2013). "The titanosaur sauropods from the late Campanian-early Maastrichtian Allen Formation of Salitral Moreno, Río Negro, Argentina". Acta Palaeontologica Polonica 58 (2): 269–284. DOI:10.4202/app.2011.0055. ↑ a b c (2007) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Random House ISBN: 9780375824197. Genus List for Holtz 2012 Weight Information ↑ (2008). "A bizarre Cretaceous theropod dinosaur from Patagonia and the evolution of Gondwanan dromaeosaurids". Proceedings of the Royal Society B: Biological Sciences 276 (1659): 1101–7. DOI:10.1098/rspb.2008.1554. ISSN 1471-2954. ↑ (2012). "A New Specimen of Austroraptor cabazai Novas, Pol, Canale, Porfiri and Calvo, 2008 (Dinosauria, Theropoda, Unenlagiidae) from the Latest Cretaceous (Maastrichtian) of Río Negro, Argentina". Ameghiniana 49 (4): 662–667. DOI:10.5710/AMGH.30.8.2012.574. ↑ a b Federico L. Agnolin (2012). "New alvarezsaurid (Dinosauria, Theropoda) from uppermost Cretaceous of north-western Patagonia with associated eggs". Cretaceous Research 35: 33–56. DOI:10.1016/j.cretres.2011.11.014. ↑ a b (2017). "Bonapartesaurus rionegrensis, a new hadrosaurine dinosaur from South America: implications for phylogenetic and biogeographic relations with North America". Journal of Vertebrate Paleontology 37 (2): 1–16. DOI:10.1080/02724634.2017.1289381. ↑ Salgado L., Gallina P.A. and Paulina Carabajal A. 2014. "Redescription of Bonatitan reigi (Sauropoda: Titanosauria), from the Campanian–Maastrichtian of the Río Negro Province (Argentina)". Historical Biology: An International Journal of Paleobiology 27(5): 525-548 ↑ a b (2022). "A new hadrosaurid (Dinosauria: Ornithischia) from the Late Cretaceous of northern Patagonia and the radiation of South American hadrosaurids". Journal of Systematic Palaeontology. DOI:10.1080/14772019.2021.2020917. ↑ a b (2010). "[https://pdfs.semanticscholar.org/f6f4/c6eb05d224719916c0b20634f54dfeb37d3f.pdf An avian coracoid from the Upper Cretaceous of Patagonia, Argentina]". Studia Geologica Salmanticensia 46 (2): 99-119. ISSN 0211-8327. ↑ Rodolfo A. Coria, Bernardo González Riga and Silvio Casadío (2012). "Un nuevo hadrosáurido (Dinosauria, Ornithopoda) de la Formación Allen, provincia de La Pampa, Argentina". Ameghiniana 49 (4): 552–572. ↑ Clarke and Chiappe, 2001. A new carinate bird from the Late Cretaceous of Patagonia (Argentina). American Museum Novitates. 3323, 1-23. ↑ a b c d (in English) Aranciaga Rolando, Mauro (2020). "A new medium-sized abelisaurid (Theropoda, Dinosauria) from the late cretaceous (Maastrichtian) Allen Formation of Northern Patagonia, Argentina". Journal of South American Earth Sciences: 102915. DOI:10.1016/j.jsames.2020.102915. ISSN 0895-9811. ↑ (2010). "Panamericansaurus schroederi gen. nov. sp. nov. Un nuevo Sauropoda (Titanosauridae-Aeolosaurini) de la Provincia del Neuquén, Cretácico Superior de Patagonia, Argentina". Brazilian Geographical Journal: Geosciences and Humanities research medium 1: 100–115. ↑ Coria, R.A. (2001) "A new theropod from the Late Cretaceous of Patagonia" in Tanke, Darren H., ed. Mesozoic Vertebrate Life, Life of the Past, Indiana University Press, pp. 3–9 ISBN: 978-0-253-33907-2. ↑ Salgado, L. and C. Azpilicueta. 2000. Un nuevo saltasaurino (Sauropoda, Titanosauridae) de la provincia de Río Negro (Formacíon Allen, Cretácico Superior), Patagonia, Argentina archive copy at the Wayback Machine. Ameghiniana 37 (3):259-264. ↑ (2016). "Revisiting the hadrosaurid diversity of the Allen Fm.: Re-evaluation of the taxonomic validity of Willinakaqe salitralensis (Ornithopoda, Hadrosauridae) from Salitral Moreno, Río Negro Province, Argentina". Ameghiniana 53 (2): 231–237. DOI:10.5710/AMGH.25.09.2015.2943. ↑ Pablo A. Gallina & Alejandro Otero (2015) Reassessment of Laplatasaurus araukanicus (SAUROPODA: TITANOSAURIA), from the Late Cretaceous of Patagonia, Argentina. Ameghiniana 52 (5):487–501. doi:10.5710/AMGH.08.06.2015.2911. ↑ (1996). "Pellegrinisaurus powelli nov. gen. et sp. (Sauropoda, Titanosauridae) from the Upper Cretaceous of Lago Pellegrini, Northwestern Patagonia, Argentina". Ameghiniana 33 (4): 355–365. ISSN 1851-8044. ↑ Heredia, S., & Salgado, L. (2014). Posición estratigráfica de los estratos supracretácicos portadores de dinosaurios en Lago Pellegrini, Patagonia septentrional, Argentina. Ameghiniana, 36(2), 229-234.

Diagram depicting the currently named Dinosauria from the Late Cretaceous Allen Formation of Argentina. Dinosaur taxa: Aeolosaurus sp. → Salitral Moreno locality, Río Negro Province.[1] Length = 15 meters.[2] Austroraptor cabazai → Santa Rosa Basin locality, Río Negro Province.[3][4] Length = 6 meters.[2] Bonapartenykus ultimus → Salitral Ojo de Agua locality, Río Negro Province.[5] Length = 2.5 meters.[5] Bonapartesaurus rionegrensis → Salitral Moreno locality, Río Negro Province.[6] Length = ∼6 meters.[1] Bonatitan reigi → Salitral de Santa Rosa locality, Río Negro Province.[7] Length = Extrapolated after relatives. Kelumapusaura machi → Cerro Matadero locality, Río Negro Province.[8] 9 meters.[8] Lamarqueavis australis → Cerro Tortugas locality, Río Negro Province.[9] Length = ∼House sparrow-sized.[9] Lapampasaurus cholinoi → Islas Malvinas locality, La Pampa Province.[10] Length = ∼7 meters.[2] Limenavis patagonica → Salitral Moreno locality, Río Negro Province.[11] Length = Extrapolated after relatives. Menucocelsior arriagadai → Salitral Ojo de Agua locality, Río Negro Province. Niebla antiqua → Cerro Matadero locality, Río Negro Province.[12] Length = 4.5 meters.[12] Panamericansaurus schroederi → Bodega Familia Schroeder locality, Neuquén Province.[13] Length = 11 meters.[2] Patagopelta cristata → Salitral Moreno locality, Río Negro Province. Quilmesaurus curriei → Salitral Ojo de Agua locality, Río Negro Province.[14] Length = 5.3 meters.[12] Rocasaurus muniozi → Salitral Moreno locality, Río Negro Province.[15] Length = Extrapolated after relatives. Excluded taxa: Willinakaqe salitralensis is considered a nomen dubium,[16] and its paratype has been reassigned to Bonapartesaurus rionegrensis.[6] Laplatasaurus araukanicus has been restricted to its lectotype which hails from the Anacleto Formation.[17] Abelisaurus comahuensis could either belong to the Allen or Anacleto formations.[12] Pellegrinisaurus powelli could either belong to the Allen or Anacleto formations.[18][19] References ↑ (2013). "The titanosaur sauropods from the late Campanian-early Maastrichtian Allen Formation of Salitral Moreno, Río Negro, Argentina". Acta Palaeontologica Polonica 58 (2): 269–284. DOI:10.4202/app.2011.0055. ↑ a b c (2007) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Random House ISBN: 9780375824197. Genus List for Holtz 2012 Weight Information ↑ (2008). "A bizarre Cretaceous theropod dinosaur from Patagonia and the evolution of Gondwanan dromaeosaurids". Proceedings of the Royal Society B: Biological Sciences 276 (1659): 1101–7. DOI:10.1098/rspb.2008.1554. ISSN 1471-2954. ↑ (2012). "A New Specimen of Austroraptor cabazai Novas, Pol, Canale, Porfiri and Calvo, 2008 (Dinosauria, Theropoda, Unenlagiidae) from the Latest Cretaceous (Maastrichtian) of Río Negro, Argentina". Ameghiniana 49 (4): 662–667. DOI:10.5710/AMGH.30.8.2012.574. ↑ a b Federico L. Agnolin (2012). "New alvarezsaurid (Dinosauria, Theropoda) from uppermost Cretaceous of north-western Patagonia with associated eggs". Cretaceous Research 35: 33–56. DOI:10.1016/j.cretres.2011.11.014. ↑ a b (2017). "Bonapartesaurus rionegrensis, a new hadrosaurine dinosaur from South America: implications for phylogenetic and biogeographic relations with North America". Journal of Vertebrate Paleontology 37 (2): 1–16. DOI:10.1080/02724634.2017.1289381. ↑ Salgado L., Gallina P.A. and Paulina Carabajal A. 2014. "Redescription of Bonatitan reigi (Sauropoda: Titanosauria), from the Campanian–Maastrichtian of the Río Negro Province (Argentina)". Historical Biology: An International Journal of Paleobiology 27(5): 525-548 ↑ a b (2022). "A new hadrosaurid (Dinosauria: Ornithischia) from the Late Cretaceous of northern Patagonia and the radiation of South American hadrosaurids". Journal of Systematic Palaeontology. DOI:10.1080/14772019.2021.2020917. ↑ a b (2010). "[https://pdfs.semanticscholar.org/f6f4/c6eb05d224719916c0b20634f54dfeb37d3f.pdf An avian coracoid from the Upper Cretaceous of Patagonia, Argentina]". Studia Geologica Salmanticensia 46 (2): 99-119. ISSN 0211-8327. ↑ Rodolfo A. Coria, Bernardo González Riga and Silvio Casadío (2012). "Un nuevo hadrosáurido (Dinosauria, Ornithopoda) de la Formación Allen, provincia de La Pampa, Argentina". Ameghiniana 49 (4): 552–572. ↑ Clarke and Chiappe, 2001. A new carinate bird from the Late Cretaceous of Patagonia (Argentina). American Museum Novitates. 3323, 1-23. ↑ a b c d (in English) Aranciaga Rolando, Mauro (2020). "A new medium-sized abelisaurid (Theropoda, Dinosauria) from the late cretaceous (Maastrichtian) Allen Formation of Northern Patagonia, Argentina". Journal of South American Earth Sciences: 102915. DOI:10.1016/j.jsames.2020.102915. ISSN 0895-9811. ↑ (2010). "Panamericansaurus schroederi gen. nov. sp. nov. Un nuevo Sauropoda (Titanosauridae-Aeolosaurini) de la Provincia del Neuquén, Cretácico Superior de Patagonia, Argentina". Brazilian Geographical Journal: Geosciences and Humanities research medium 1: 100–115. ↑ Coria, R.A. (2001) "A new theropod from the Late Cretaceous of Patagonia" in Tanke, Darren H., ed. Mesozoic Vertebrate Life, Life of the Past, Indiana University Press, pp. 3–9 ISBN: 978-0-253-33907-2. ↑ Salgado, L. and C. Azpilicueta. 2000. Un nuevo saltasaurino (Sauropoda, Titanosauridae) de la provincia de Río Negro (Formacíon Allen, Cretácico Superior), Patagonia, Argentina archive copy at the Wayback Machine. Ameghiniana 37 (3):259-264. ↑ (2016). "Revisiting the hadrosaurid diversity of the Allen Fm.: Re-evaluation of the taxonomic validity of Willinakaqe salitralensis (Ornithopoda, Hadrosauridae) from Salitral Moreno, Río Negro Province, Argentina". Ameghiniana 53 (2): 231–237. DOI:10.5710/AMGH.25.09.2015.2943. ↑ Pablo A. Gallina & Alejandro Otero (2015) Reassessment of Laplatasaurus araukanicus (SAUROPODA: TITANOSAURIA), from the Late Cretaceous of Patagonia, Argentina. Ameghiniana 52 (5):487–501. doi:10.5710/AMGH.08.06.2015.2911. ↑ (1996). "Pellegrinisaurus powelli nov. gen. et sp. (Sauropoda, Titanosauridae) from the Upper Cretaceous of Lago Pellegrini, Northwestern Patagonia, Argentina". Ameghiniana 33 (4): 355–365. ISSN 1851-8044. ↑ Heredia, S., & Salgado, L. (2014). Posición estratigráfica de los estratos supracretácicos portadores de dinosaurios en Lago Pellegrini, Patagonia septentrional, Argentina. Ameghiniana, 36(2), 229-234.

Central Museum of Mongolian Dinosaurs, Ulaanbaatar. Complete indexed photo collection at WorldHistoryPics.com.

Map of the localities in the Bauru Basin where the sauropod dinosaurs were collected.

(A) A phylogenetic principal-component analysis (PCA) represents the projection of the Dinosauria supertree (STAR Methods) into a PCA of climatic variables. PC1 axis shows strong positive correlation with maximum temperature ([temp max), low positive correlation with precipitation seasonality ( precip season), strong negative correlation with minimum temperature (Ytemp min), and strong negative correlation with minimum precipitation (Yprecip min). PC2 axis shows strong positive correlation with minimum temperature ([temp min) and negative correlation with precipitation seasonality (Yprecip season). Shadows around points highlight the relative density in the principal compo- nent space of non-dinosaurian Dinosauromorpha (gray), Ornithischia (blue), Sauropodomorpha (green), and Theropoda (red). (B) Lower left plot shows 95% confidence interval convex hulls for each dinosauromorph subclade. Blue thermometer (top left corner) symbolizes the direction of the vector in the PC space region for cold temper- atures; yellow thermometer (top right corner) indicates the direction of the vector in PC space for warm tem- peratures; brown shrub (top right corner) depicts dry conditions, while the same with a gray, rainy cloud (mid, lower side of the graph) illustrates seasonal conditions. Silhouettes represent the following taxa (clockwise from the higher left corner): Minmi, Edmontosaurus, Pachyrhinosaurus, Tyrannosaurus, Asilisaurus, Graci- liceratops, Harpymimus, Altirhinus, Gobititan, Suz- housaurus, Marasuchus, Pampadromaeus, Herrer- asaurus, Vulcanodon, Diplodocus, Giraffatitan, Coelophysis, Dromomeron, Gondwanatitan, Tapuiasaurus, Anchisaurus, Siamotyrannus, Diodorus, Suchomimus, Phuwiangosaurus, Ouranosaurus, Irritator, Tangvayosaurus, Nanshiungosaurus, Aeolosaurus, Rebbachisaurus, Chuxiongosaurus, Tethyshadros, Koreanosaurus. Genyodectes, Mapusaurus, Vegavis, Goyocephale, and Rhoetosaurus.

Fossil samples – e.g. ‘primitive’ bony fish (1, 2), a skull of a temnospondyl ‘amphibian’ (probably a metoposauroid) in dorsal view (3), a skull of an archosaur of the crocodile lineage (probably a phytosaur) in palatal view (4), holotype of the “gliding reptile” Icarosaurus siefkeri [1] (5) and Atreipus-Grallator-type dinosaur tracks (bottom right) – from the Newark Supergroup, i.e. a series of mainly Late Triassic to Early Jurassic sedimentary rocks of eastern North America ↑ Edwin H. Colbert: A gliding reptile from the Triassic of New Jersey. American Museum Novitates, 2230. American Museum of Natural History, New York 1966, digitallibrary.amnh.org, cf. fig. 3 therein.

Diuqin is an unenlagiine dinosaur from the Late Cretaceous of what is now Argentina. Unenlagiines, known exclusively from South America, are usually classified as dromaeosaurs though this is sometimes debated. Like dromaeosaurs, they were covered in feathers, carnivorous, and had the large sickle-like claw on the inner toe of each foot. Unique to unenlagiines is their elongated snout, suggesting a piscivorous diet. Diuqin was a medium-sized unenlagiine, at about 4 m in length.

Figure 1. Evolution of macroecological traits in Dinosauria. Large scale event in dinosaur evolution (a); the origin of dinosaurs (star), hyperthermals (volcano), the earliest fossil Avialae (bird), the earliest fossil angiosperm (flower), the Cretaceous/Palaeogene mass extinction (asteroid). Phylogeny of dinosaurs (b) redrawn from Sereno and adapted to the current consensus and upon which an ancestral state reconstruction of temperature niche (mean annual temperature) after Chiarenza et al. is plotted; Mesozoic palaeogeographies (c) for Triassic (T), Jurassic (J) and Cretaceous (K). Silhouette colours symbolize body mass for each of the taxa represented; information on dietary habits are plotted after Barrett and Zanno & Makovicky; numbers represent clades discussed through this study: 1, Ornithischia; 2, Thyreophora; 3, Ornithopoda; 4, Hadrosauroidea; 5, Marginocephalia; 6, Ceratopsia; 7, Saurischia; 8, Sauropodomorpha; 9, Sauropoda; 10, Theropoda; 11, Ceratosauria; 12, Tetanurae; 13, Coelurosauria; 14, Maniraptoriformes; 15, Maniraptora; 16, Deinonychosauria; 17, Avialae; 18, Ornithothoraces. Palaeogeographies modified from original plots via R package ‘mapast’ using plate models by Scotese.

Diagram illustrating the "Temporal paradox" in paleontology. First given it's nickname by Alan Feduccia, the paradox is made up by the fact that almost all feathered dinosaurs are dated to have lived millions of years after Archaeopteryx, the oldest bird (late Jurassic, believed to have existed about 150 million years ago). Only a few of the feathered dinosaurs/birdlike dinosaurs are given an older date than Archaeopteryx.

Montage of eight different representatives of coelurosaurian dinosaurs: (Clockwise from upper left) GIN 100/42 which may represent Citipati or a different oviraptorosaur, Sinosauropteryx prima, Nothronychus mckinleyi, Tyrannosaurus rex, Bambiraptor feinbergi, Passer domesticus, Struthiomimus altus, Microraptor gui. This is a collection of eight different works already found in Wikimedia Commons (see source field below).

Simplified cladogram of Dinosauria with the distribution of feathers according to the fossil record. Despite its more ancient origin, it was only in maniraptoriformes that modern-type feathers (pennaceous feathers) have arisen (Based in Xu & Guo, 2009; Clarke, 2013; Godefroit et al., 2013; Han et al., 2014; Koshchowitz et al., 2014).