Toutes les images de la base — taxons, formations et intervalles géologiques.
⚠ La fonctionnalité de récupération des images est en cours de test, des images non pertinentes peuvent apparaître.
2,398 image(s)
A render of Miolingian (Drumian) earth with focus on the continent of Laurentia, a cyclone is visible to the north. Intended to represent Wheeler Shale deposition
Diagram of the skull of Haya griva in lateral view, reconstructed from IGM 100/2017
Life reconstruction of Maleriraptor kuttyi with the unaysaurid sauropodomorph Jaklapallisaurus asymmetricus, both from the lower Norian Upper Maleri Formation of south-central India.
Reconstruction of Camelotia borealis, a "melanorosaurid"
Size of Austroraptor cabazai compared to a human, a species of Dromaeosaurid Unenlagiinae who lived during the Cretaceous period in Argentina, more precisely in the Allen Formation.
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.
Life restoration of Alnashetri
Skeletal cast of Dilong paradoxus on display at the Milwaukee Public Museum. Part of the Tyrannosaurs: Meet the Family traveling exhibit developed by The Australian Museum.
Reconstructions of diplodocoid skulls used in this analysis. Reconstructions of Nigersaurus and Diplodocus modified from [10] and [34], respectively. All other reconstructions based on material listed in Table S1. Skulls scaled to equivalent anteroposterior lengths.
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.
Left dentary of rebbachisaurid sauropod Demandasaurus darwini gen. et sp. nov. from Late Barremian–Early Aptian, Early Cretaceous of Tenadas de los Vallejos II, Spain, MDS−RVII,443, in lateral (A) and dorsal (B) views. The arrow indicates a depressed area in a dorsolateral position.
Life reconstruction of Gremlin slobodorum
Skull of Yulong mini. The horizontal line projected through the posterodorsal corner of the antorbital fenestra is parallel to the line linking the articular end of the quadrate and the ventral margin of the premaxillae.
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.
The palatal view of the skull of NMS G.2021.6.2 and comparative assessment of the pterygoid region. The palatal region of NMS G.2021.6.2, A as seen in the ventral view. The comparative, to scale, pterosaur palatine and palatal regions in the ventral view. From left to right: B Cacibupteryx (IGO-V 208); C Parapsicephalus (GSM 3166); D Dearc (NMS G.2021.6.2); E Rhamphorhynchus (NHM R 2786); F Rhamphorhynchus (CM 11434). Abbreviations: bsp—basipterygoid; cho—choana; ec -, ectopterygoid; ipv—interpterygoid vacuity; pal—palatine; pf—posterior palatine fenestra; pte—pterygoid; stf -subtemporal fenestra; sof – suborbital fenestra; vm—vomer. Scale bar 10 mm
Life restoration of Cearadactylus atrox. Based on figure 2 of "On the systematic relationships of Cearadactylus atrox, an enigmatic Early Cretaceous pterosaur from the Santana Formation of Brazil" by D. M. Unwin Mitteilungen Museum für Naturkunde Berlin, Geowissenschaftlichen Reihe 5: 239-263
a Skeletal reconstruction of A. greppini. Elements preserved in the material and therefore providing information for the skeletal reconstruction are marked in blue. Because much information is missing from the incomplete skeletal material, the dorsal vertebrae, the proportions and morphology of the cervical vertebrae and the skull were modified from Camarasaurus. b Scaled silhouette drawings of Cetiosauriscus stewarti (in black) and A. greppini (in grey) demonstrating the significant size difference between the two taxa. Scale bar is 1 m
Artist's Impression
Goronyosaurus nigerensis - unusual tylosaurine mosasaur from maastrichtian of Niger
Fossil of Coloborhynchus, an extinct pterosaur- Took the photo at Naturalis museum, Leiden
Coelurus fragilis, a coelurosaur from the Late Jurassic of North America, pencil drawing, digital coloring
Mixosaurus sp. Anhui Geological Museum
Figure 1: Geographic distribution of Early Cretaceous iguanodontians in North America. Taxa found at each locality are as follows: (A) Dakotadon lakotaensis; (B) Osmakasaurus depressus; (C) Tenontosaurus tilletti, Tenontosaurus dossi; (D) Tenontosaurus tilletti; (E) Theiophytalia kerri; (F) Cedrorestes crichtoni, Planicoxa venenica; (G) Hippodraco scutodens; (H) Iguanacolossus fortis; (I) Tenontosaurus sp; (J) Tenontosaurus tilletti.
Numbers above nodes represent bootstrap values, whereas those beneath nodes represent Bremer decay values. Bootstrap values lower than 20 and Bremer decay values less than 2 are not shown.
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.
'Saturnalia' Skulpturengruppe von Ernesto Biondi in Buenos Aires ( im Botanischen Garten)
(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.
Reconstruction of Mochlodon suessi from the Late Cretaceous of Austria. Based on Zalmoxes by Scott Hartman
Numbers above nodes represent bootstrap values, whereas those beneath nodes represent Bremer decay values. Bootstrap values lower than 20 and Bremer decay values less than 2 are not shown.
Life restoration of the German Jurassic ichthyosaur Suevoleviathan disinteger. The dorsal and caudal fins are loosely based on those of Stenopterygius. References Maisch, M.W. (2020). "The best-preserved skeleton of Suevoleviathan integer (Bronn, 1844)(Reptilia: Ichthyosauria) from the lower Jurassic of south-western Germany, with a discussion of the genus". Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 297 (2): 153–172. Maisch, M.W. (1998). "A new ichthyosaur genus from the Posidonia Shale (Lower Toarcian, Jurassic) of Holzmaden, SW-Germany with comments on the phylogeny of post-Triassic ichthyosaurs". Neues Jahrbuch für Geologie und Paläontologie-Abhandlungen 209 (1): 47–78.
Tuarangisaurus cabazai skeleton restoration, Copenhagen
Muraenosaurus? Reedii, Sp. Nov. and Tricleidus? Laramiensis Knight, American Jurassic Plesiosaurs
Restored skeleton of Anzu wyliei (previously labelled as a specimen of Chirostenotes)
Life restoration of the mosasaurine mosasaurid Eremiasaurus, with unknown portions and soft tissues based primarily on Prognathodon and supplemented with Mosasaurus where needed. References Leblanc, A.R.H.; Caldwell, M.W.; Bardet, N. (2012). "A new mosasaurine from the Maastrichtian (Upper Cretaceous) phosphates of Morocco and its implications for mosasaurine systematics". Journal of Vertebrate Paleontology 32 (1): 82–104. Lindgren, J.; Kaddumi, H.; Polcyn, M. (2013). "Soft tissue preservation in a fossil marine lizard with a bilobed tail fin". Nature Communications 4: 2423. DOI:10.1038/ncomms3423. Konishi, T.; Brinkman, D.; Massare, J.A.; Caldwell, M.W. (2011). "New exceptional specimens of Prognathodon overtoni (Squamata, Mosasauridae) from the upper Campanian of Alberta, Canada, and the systematics and ecology of the genus". Journal of Vertebrate Paleontology 31 (5): 1026–1046. Russell, D.A. (1967). "Systematics and morphology of American mosasaurs". Bulletin of the Peabody Museum of Natural History 23: 1–241.
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.
Photo montage of different specimens of mosasaurs: Opetiosaurus Vallecillosaurus Halisaurus Plotosaurus Platecarpus Tylosaurus
Eonatator sternbergi, a mosasaur from the Late Cretaceous of Kansas. Digital.
Leptorhynchos, a small caenagnathid from the Campanian of Western North America. Original work in pencil and charcoal by Nick Longrich. Additional digital editing in Adobe Photoshop by Nick Longrich.
Paddle of the British Jurassic pliosaurid plesiosaur Eardasaurus housed at the Oxford University Natural History Museum.
Title: A descriptive catalogue of the marine reptiles of the Oxford clay. Based on the Leeds Collection in the British Museum (Natural History), London .. Identifier: descriptivecatal02brit (find matches) Year: 1910 (1910s) Authors: British Museum (Natural History). Dept. of Geology; Andrews, Charles William, 1866-1924 Subjects: Reptiles, Fossil Publisher: London, Printed by order of the Trustees Contributing Library: Smithsonian Libraries Digitizing Sponsor: Biodiversity Heritage Library View Book Page: Book Viewer About This Book: Catalog Entry View All Images: All Images From Book Click here to view book online to see this illustration in context in a browseable online version of this book. Text Appearing Before Image: CATAL.MARINE KEPT. OXFORD CLAY. PART II. PLATE I. pmcc. Text Appearing After Image: >p77ia:. G.M.Woodward del. etlibh. West, Newman imp. PLIOSAURUS FEROX. Note About Images Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.
Phylogenetic relationships, chronostratigraphic, and paleoecological implications of M. intrepidus. a Graphic illustrating temporal range of North American tyrannosauroids including species-level range prior to the discovery of M. intrepidus, extension of current range, and hypothesized range based on isolated teeth12. The current gap in the North American tyrannosauroid record spans from the Tithonian to the Aptian. Faunal composition of Late Cretaceous ecosystems was established between the Albian and Turonian, as recognized by the stratigraphic appearance of major clades (see refs. 7,12 and references therein). b generalized phylogenetic relationships of Tyrannosauroidea, showing the appearance of select traits related to cursoriality in tyrannosaurs that are newly optimized as a result of the discovery of M. intrepidus. Tree topology follows this study using the modified dataset of Carr and colleagues27. Coelurus and Tanycolagreus are grafted as basal tyrannosauroids following Brusatte and colleagues5. c Stratigraphic distribution of Allosauria in North America (incl. Megaraptora but see ref. 70 for alternative hypotheses regarding this clade) documents overlap with M. intrepidus in early Late Cretaceous ecosystems leading to (d) refined calibration on the origin of late diverging tyrannosauroids and clade-level faunal turnover within apex predator roles throughout the Late Jurassic–Late Cretaceous of North America. Colored polygons are stylized call-outs and are not intended to reflect two-dimensional data. Temporal data corresponding to this figure are available in Supplementary Table 5
Réplica expuesta en CaixaForum Sevilla. Neuquensaurus australis último de los titanosaurios. Encontrado en Cinco Saltos, Neuquén por Santiago Roth. Ocho metros de longitud y tres mil kilos de peso.
Rhomaleosaurus cramptoni fossil, Natural History Museum, London
Carinodens acrodon holotype left maxilla (MHNM.KHG.1510) (A) compared to Xenodens calminechari holotype left maxilla (MHNM.KHG.331) (B), in lateral view; both from Sidi Chennane, Oulad Abdoun Basin, Morocco; Phosphates, Upper Couche III, uppermost Maastrichtian [9,24]. Scales = 50 mm.
Holotype of Rexarthuria or "Palaeornis" clifti, PV OR 2353. Proximal extremity of left humerus.
Phylogenetic position of Akainacephalus johnsoni in (A), a strict consensus of 21 equally most parsimonious trees, including the wildcard taxon Ahshislepelta minor, placing A. johnsoni within a large polytomy, consisting of crown group taxa that include Asian and all Laramidian ankylosaurids; and (B), the resulting strict consensus of six equally most phylogenetic trees, from which the wildcard taxon Ahshislepelta minor has been pruned. The crown group taxa are slightly better resolved in the pruned analysis, in which Akainacephalus johnsoni forms a clade with its sister taxon Nodocephalosaurus kirtlandensis, nested within the clade that also includes the Asian taxa Minotaurasaurus ramachandrani, Tarchia kilanae, and Shanxia tianzhenensis, suggesting a close taxonomic relationship with Nodocephalosaurus kirtlandensis and Asian taxa.
Phylogenetic position of Akainacephalus johnsoni in (A), a strict consensus of 21 equally most parsimonious trees, including the wildcard taxon Ahshislepelta minor, placing A. johnsoni within a large polytomy, consisting of crown group taxa that include Asian and all Laramidian ankylosaurids; and (B), the resulting strict consensus of six equally most phylogenetic trees, from which the wildcard taxon Ahshislepelta minor has been pruned. The crown group taxa are slightly better resolved in the pruned analysis, in which Akainacephalus johnsoni forms a clade with its sister taxon Nodocephalosaurus kirtlandensis, nested within the clade that also includes the Asian taxa Minotaurasaurus ramachandrani, Tarchia kilanae, and Shanxia tianzhenensis, suggesting a close taxonomic relationship with Nodocephalosaurus kirtlandensis and Asian taxa.
IdentificatieTitel(s): Pootafdruk en een spoor van een staart. Brontozoum Sillimanium and B. Minisculum (titel op object). Caudal Trail? (titel op object)Objecttype: foto bladzijde Objectnummer: RP-F-2001-7-1066-4Opschriften / Merken: nummer, recto, gedrukt: ‘Plate XVI. Fig. 1. Fig. 2.’Omschrijving: Links de pootafdruk van een Brontozoum Sillimanium en Brontozoum Minisculum, rechts (vermoedelijk) een spoor van de staart van een Platypterna.VervaardigingVervaardiger: fotograaf: J.L. Lovell (vermeld op object)Plaats vervaardiging: AmherstDatering: ca. 1858 - in of voor 1863Materiaal: fotopapier Techniek: albuminedrukAfmetingen: pagina: h 313 mm × b 232 mmOnderwerpWat: foot-print, trackVerwerving en rechtenCredit line: Aankoop met steun van de Mondriaan Stichting, het Prins Bernhard Cultuurfonds, het VSBfonds, het Paul Huf Fonds/Rijksmuseum Fonds en het Egbert KunstfondsVerwerving: aankoop 2001Copyright: Publiek domein
Clidastes propython, a mosasaur from the Late Cretaceous of Kansas, digital.
Protoceratops andrewsi skeleton at Carnegie Museum of Natural History.