Earth:Maastrichtian

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The Maastrichtian ( /mɑːˈstrɪktiən/ mahss-TRIK-tee-ən) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from 72.1 to 66 million years ago. The Maastrichtian was preceded by the Campanian and succeeded by the Danian (part of the Paleogene and Paleocene).[1] It is named after the city of Maastricht, the capital and largest city of the Limburg province in the Netherlands.

The Cretaceous–Paleogene extinction event (formerly known as the Cretaceous–Tertiary extinction event)[lower-alpha 1] occurred at the end of this age.[1] In this mass extinction, many commonly recognized groups such as non-avian dinosaurs, pterosaurs, plesiosaurs, and mosasaurs, as well as many other lesser-known groups, died out. The cause of the extinction is most commonly linked to an asteroid about 10 to 15 kilometres (6.2 to 9.3 mi) wide[2][3] colliding with Earth, ending the Cretaceous.

Stratigraphic definitions

Rendzina soil on the Maastrichtian Chalk in Kozubów Landscape Park, Poland

Definition

The Maastrichtian was introduced into scientific literature by Belgian geologist André Hubert Dumont in 1849, after studying rock strata of the Chalk Group close to the Dutch city of Maastricht. These strata are now classified as the Maastricht Formation – both the formation and stage derive their names from the city.[4] The Maastricht Formation is known for its fossils from this age, most notably those of the giant sea reptile Mosasaurus, which in turn derives its name from the nearby river Maas (mosa being Latin for the river Maas).[5][6]

The base of the Maastrichtian Stage is at the first appearance of ammonite species Pachydiscus neubergicus. At the original type locality near Maastricht, the stratigraphic record was later found to be incomplete. A reference profile for the base was then appointed in a section along the Ardour river called Grande Carrière, close to the village of Tercis-les-Bains in southwestern France.[7][8] The top of the Maastrichtian Stage is defined to be at the iridium anomaly at the Cretaceous–Paleogene boundary (K–Pg boundary), which is also characterised by the extinction of many groups of life.[9]

Subdivision

The Maastrichtian is commonly subdivided into two substages (Upper and Lower) and three ammonite biozones. The biozones are (from young to old):[10]

The Maastrichtian is roughly coeval with the Lancian North American Land Mammal Age.

Palaeogeography

The breakup of Pangaea was nearly complete in the Maastrichtian, with Australia beginning to break away from Antarctica and Madagascar breaking away from India. However, Arabia had not yet rifted away from Africa. North America was separated from Europe by rift basins, but seafloor spreading had not yet commenced between the two continents.[11]

The Pacific Plate was rapidly growing in size as the surrounding oceanic plates were consumed by subduction, and the Pacific-Izanagi Ridge was rapidly approaching Asia.[12]

Eruption of the Deccan Traps large igneous province began during the Maastrichtian, at around 67 million years ago. This is thought to be a consequence of India drifting over the Réunion hotspot.[13]

Climate

During the Maastrichtian, the global climate began to shift from the warm and humid climate of the Mesozoic to the colder and more arid climate of the Cenozoic.[13] Variation of climate with latitude also became greater. This was likely caused by a major reorganization of oceanic circulation that took place at the boundary between the early and late Maastrichtian. This reorganization was triggered by the breach of tectonic barriers in the South Atlantic, permitting deep ocean water to begin circulating from the nascent North Atlantic to the south. This initiated thermohaline circulation similar to that of the modern oceans. At the same time, the Laramide orogeny drained the Western Interior Seaway of North America, further contributing to global cooling.[14] Nonetheless, the latest Maastrichtian featured a sharp, pronounced warming,[15][16] which was caused by the activity of the Deccan Traps.[17]

South-central Alaska had a mean annual temperature of 7.42±1.2 °C, a warm monthly mean temperature of 17.08±1.6 °C, and a cold monthly mean temperature of −2.31±1.9 °C.[18][19]

Paleontology

Fossil of Hemipneustes leymeriei

Dinosaurs remained the dominant large terrestrial animals throughout the Maastrichtian, though mammals with internal organs similar to modern mammals were also present. Both ammonites and pterosaurs were in decline during the Maastrichtian well prior to being wiped out in the extinction event.[20]

Dinosaurs of the late Maastrichtian Hell Creek Formation

Dinosaurs

Ornithiscians

Hadrosaurs and ceratopsians comprised the most abundant clades of ornithiscian fauna in the Maastrichtian, with thescelosaurids, ankylosaurs and pachycephalosaurs also present.[21][22]

Sauropods

Speculative life appearance of Bruhathkayosaurus matleyi.

As a part of the so-called sauropod hiatus, sauropods were globally less common than in the Early Cretaceous or the Jurassic Period, and are absent in some localities particularly in the northern hemisphere.[23] By the Maastritchian, large ornithiscians such as the hadrosaurs had spread to most of the Earth's landmass (excluding only India, Madagascar, Australia and Antarctica), displacing or competing with sauropods in many ecosystems.[21][24]

Nevertheless, sauropods continued to thrive throughout much of the Earth. They were especially widespread in South America, Africa, Madagascar and India. Maastrichtian sauropods are also known from parts of Europe, Asia, and North America, although many localities had limited or no Sauropod presence on those continents.[21]

Though no Maastrichtian sauropods are known from Australia and Antarctica, this may be due to lack of evidence as few Maastrichtian dinosaur fossils are known from those places in general.

Theropods

A Tarbosaurus feeding on a Deinocheirus carcass, with a group of Saurolophus visible in the background, Nemegt formation, early Maastrichtian.

Apex predator niches were commonly occupied by abelisaurids such as Carnotaurus and Majungasaurus in the southern hemisphere, and tyrannosaurids in the northern hemisphere.[21][25] The largest tyrannosaurs began to appear in North America and Asia in the late Campanian and throughout the Maastrichtian, including the famous dinosaur Tyrannosaurus.[26][27][28][29]

Medium-sized theropods included smaller ceratosaurs and tyrannosaurs, such as Masiakasaurus and Dryptosaurus, respectively, as well as dromaeosaurids[28] such as Austroraptor[30] and Dakotaraptor. [31]

Other large theropods included herbivores like therizinosaurids and the giant ornithomimosaur Deinocheirus.[28][32]

Smaller theropods included alvarezosaurids, ornithomimosaurs, troodontids, small dromaeosaurs, and oviraptosaurians such as Avimimus.[28]

Avialans (including crown birds)

Several stem-group clades of avialans (the group which includes modern birds and their close extinct relatives), such as Enantiornithes, Ichthyornithes, and Hesperornithes, persisted to the latest Maastrichtian but became extinct during the Cretaceous-Paleogene extinction event.[33][34] Modern birds belonging to Neornithes unambiguously appeared in the fossil record during the Maastrichtian, as indicated by taxa such as Asteriornis, which is suggested to be a close relative of modern fowl,[35] as well as Vegavis of uncertain affinities.[36]

Pterosaurs

Traditionally, pterosaur faunas of the Maastrichtian were assumed to be dominated by azhdarchids, with other pterosaur groups having become extinct earlier on. However, more recent findings suggest a fairly composite pterosaur diversity: at least six ("Nyctosaurus" lamegoi, a Mexican humerus, a Jordanian humerus, and several taxa from Morocco) nyctosaurs date to this period, as do a few pteranodontids, and Navajodactylus, tentatively assigned to Azhdarchidae, lacks any synapomorphies of the group.[37][38] This seems to underscore a higher diversity of terminal Cretaceous pterosaurs than previously thought.[39][40][41]

Maastrichtian landscape

Flora

The radiation of angiosperms (flowering plants) was well under way in the Maastrichtian. From 50% to 80% of all genera of land plants were angiosperms, though gymnosperms and ferns still covered larger areas of the land surface.[42][43]

Notes

  1. ↑ This designation has as a part of it a term, 'Tertiary', that is now discouraged as a formal geochronological unit by the International Commission on Stratigraphy.

References

  1. ↑ 1.0 1.1 Ogg, James G.; Gradstein, Felix M.; Smith, A.G. (2004). A geologic time scale 2004. Cambridge, UK: Cambridge University Press. ISBN 0-521-78142-6. https://books.google.com/books?id=rse4v1P-f9kC. Retrieved 8 May 2022. 
  2. ↑ Sleep, Norman H.; Lowe, Donald R. (9 April 2014). "Scientists reconstruct ancient impact that dwarfs dinosaur-extinction blast". American Geophysical Union. https://news.agu.org/press-release/scientists-reconstruct-ancient-impact-that-dwarfs-dinosaur-extinction-blast/. 
  3. ↑ Amos, Jonathan (15 May 2017). "Dinosaur asteroid hit 'worst possible place'". https://www.bbc.com/news/science-environment-39922998. 
  4. ↑ Jagt, J.W.M; Jagt-Yazykova, E.A. (2012). "Stratigraphy of the type Maastrichtian – a synthesis". Scripta Geologica 08: 5–32. https://repository.naturalis.nl/pub/428924. Retrieved 8 May 2022. 
  5. ↑ Hallie P. Street (2016). A re-assessment of the genus Mosasaurus (Squamata: Mosasauridae) (PDF) (PhD). University of Alberta. doi:10.7939/R31N7XZ1K.
  6. ↑ Mike Everhart (May 14, 2010). "Mosasaurus hoffmanni-The First Discovery of a Mosasaur?". http://oceansofkansas.com/mosahoff.html. 
  7. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named OdinLamaurelle2001
  8. ↑ Odin, G.S. (2001). "Chapter E5c Numerical age calibration of the Campanian-Maastrichtian succession at Tercis les Bains (landes, france) and in the Bottaccione Gorge (Italy)". Developments in Palaeontology and Stratigraphy 19: 775–782. doi:10.1016/S0920-5446(01)80068-6. ISBN 978-0-444-50647-4. Bibcode: 2001DvPSt..19..775O. 
  9. ↑ Ogg, Gradstein & Smith 2004, p. 345.
  10. ↑ Ward, Peter D.; Kennedy, W. James (1993). "Maastrichtian Ammonites from the Biscay Region (France, Spain)". Memoir (The Paleontological Society) 34 (S34): 1–58. doi:10.1017/S0022336000062223. Bibcode: 1993JPal...67S...1W. 
  11. ↑ Torsvik, Trond H.; Cocks, L. Robin M. (2017). Earth history and palaeogeography. Cambridge, United Kingdom: Cambridge University Press. pp. 220, 222, 230. ISBN 978-1-107-10532-4. 
  12. ↑ Torsvik & Cocks 2017, p. 220.
  13. ↑ 13.0 13.1 Torsvik & Cocks 2017, p. 234.
  14. ↑ Frank, Tracy D.; Arthur, Michael A. (April 1999). "Tectonic forcings of Maastrichtian ocean-climate evolution". Paleoceanography 14 (2): 103–117. doi:10.1029/1998PA900017. Bibcode: 1999PalOc..14..103F. 
  15. ↑ Olsson, R. K. (1 July 2001). "Paleobiogeography of Pseudotextularia Elegans During the Latest Maastrichtian Global Warming Event" (in en). The Journal of Foraminiferal Research 31 (3): 275–282. doi:10.2113/31.3.275. ISSN 0096-1191. Bibcode: 2001JForR..31..275O. https://pubs.geoscienceworld.org/jfr/article/31/3/275-282/76894. Retrieved 25 October 2024. 
  16. ↑ Abramovich, Sigal; Keller, Gerta (July 2003). "Planktonic foraminiferal response to the latest Maastrichtian abrupt warm event: a case study from South Atlantic DSDP Site 525A" (in en). Marine Micropaleontology 48 (3–4): 225–249. doi:10.1016/S0377-8398(03)00021-5. Bibcode: 2003MarMP..48..225A. https://www.sciencedirect.com/science/article/pii/S0377839803000215. Retrieved 25 October 2024. 
  17. ↑ Woelders, L.; Vellekoop, J.; Kroon, D.; Smit, J.; Casadío, S.; Prámparo, M. B.; Dinarès-Turell, J.; Peterse, F. et al. (30 March 2017). "Latest Cretaceous climatic and environmental change in the South Atlantic region: LATEST CRETACEOUS CHANGE SOUTH ATLANTIC" (in en). Paleoceanography and Paleoclimatology 32 (5): 466–483. doi:10.1002/2016PA003007. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016PA003007. Retrieved 7 November 2024. 
  18. ↑ Tomsich, Carla Susanne; McCarthy, Paul J.; Fowell, Sarah J.; Sunderlin, David (15 September 2010). "Paleofloristic and paleoenvironmental information from a Late Cretaceous (Maastrichtian) flora of the lower Cantwell Formation near Sable Mountain, Denali National Park, Alaska" (in en). Palaeogeography, Palaeoclimatology, Palaeoecology 295 (3–4): 389–408. doi:10.1016/j.palaeo.2010.02.023. Bibcode: 2010PPP...295..389T. https://www.sciencedirect.com/science/article/pii/S0031018210000957. Retrieved 1 November 2024. 
  19. ↑ Fiorillo, Anthony R.; McCarthy, Paul J.; Hasiotis, Stephen T. (1 January 2016). "Crayfish burrows from the latest Cretaceous lower Cantwell Formation (Denali National Park, Alaska): Their morphology and paleoclimatic significance" (in en). Palaeogeography, Palaeoclimatology, Palaeoecology 441: 352–359. doi:10.1016/j.palaeo.2015.05.019. Bibcode: 2016PPP...441..352F. https://www.sciencedirect.com/science/article/pii/S003101821500276X. Retrieved 1 November 2024. 
  20. ↑ Torsvik & Cocks 2017, p. 238, 239.
  21. ↑ 21.0 21.1 21.2 21.3 Longrich, Nicholas; Pyron, R. Alexander; Suberbiola, Xabier; Jalil, Nour-Eddine (November 2020). "The first duckbill dinosaur (Hadrosauridae: Lambeosaurinae) from Africa and the role of oceanic dispersal in dinosaur biogeography". Cretaceous Research: 1. https://www.researchgate.net/publication/346582740_The_first_duckbill_dinosaur_Hadrosauridae_Lambeosaurinae_from_Africa_and_the_role_of_oceanic_dispersal_in_dinosaur_biogeography. 
  22. ↑ Csiki-Sava, Zoltan; Buffetaut, Eric; Ősi, Attila; Pereda-Suberbiola, Xabier; Brusatte, Stephen L. (2015-01-08). Island life in the Cretaceous - faunal composition, biogeography, evolution, and extinction of land-living vertebrates on the Late Cretaceous European archipelago. Pensoft Publishers. Pensoft Publishers. pp. 28. http://archive.org/details/islandlifecreta469csik. 
  23. ↑ Ryan, Michael J.; Evans, David C. (2018). "The first occurrence of a sauropod body fossil in Canada, with implications for the "sauropod hiatus" in North America". Journal of Vertebrate Paleontology 38: 207. https://vertpaleo.org/wp-content/uploads/2021/03/SVP-2018-program-book-V4-FINAL-with-covers-9-24-18.pdf. 
  24. ↑ Longrich, Nick (2024-07-04). Did Dinosaurs Cross Oceans?. Retrieved 2026-05-04 – via YouTube.
  25. ↑ Rowe, Andre J.; Cerroni, Mauricio A.; Rayfield, Emily J. (2026-01-21). "Southern hemisphere ceratosaurs evolved feeding mechanics paralleling those of Northern hemisphere tyrannosaurids". Scientific Reports 16 (1): 2804. doi:10.1038/s41598-025-32686-4. ISSN 2045-2322. PMID 41565728. PMC 12824262. https://pmc.ncbi.nlm.nih.gov/articles/PMC12824262/. 
  26. ↑ Hone, David W. E.; Wang, Kebai; Sullivan, Corwin; Zhao, Xijin; Chen, Shuqing; Li, Dunjin; Ji, Shuan; Ji, Qiang et al. (2011-08-01). "A new, large tyrannosaurine theropod from the Upper Cretaceous of China". Cretaceous Research 32 (4): 495–503. doi:10.1016/j.cretres.2011.03.005. ISSN 0195-6671. https://www.sciencedirect.com/science/article/pii/S0195667111000371. 
  27. ↑ Longrich, Nick (2026-03-12). A Mysterious Giant Tyrannosaur From the Campanian of New Mexico. Retrieved 2026-04-27 – via YouTube.{{cite AV media}}: CS1 maint: date and year (link)
  28. ↑ 28.0 28.1 28.2 28.3 Glut, Donald F. (1997). Dinosaurs: The Encyclopedia (1st ed.). McFarland, Incorporated, Publishers, 1997 (published Jul 1, 1997). pp. 186-187, 257-259, 333-334, 376-377, 568-570, 618-619, 946-47, et al.. ISBN 0899509177, 9780899509174. 
  29. ↑ Witton, Mark (May 13, 2025). King Tyrant: A Natural History of Tyrannosaurus rex. Princeton University Press. ISBN 9780691245584. 
  30. ↑ Novas, Fernando E.; Pol, Diego; Canale, Juan I.; Porfiri, Juan D.; Calvo, Jorge O. (2009-03-22). "A bizarre Cretaceous theropod dinosaur from Patagonia and the evolution of Gondwanan dromaeosaurids". Proceedings. Biological Sciences 276 (1659): 1101–1107. doi:10.1098/rspb.2008.1554. ISSN 0962-8452. PMID 19129109. PMC 2679073. https://pmc.ncbi.nlm.nih.gov/articles/PMC2679073/. 
  31. ↑ DePalma, Robert A.; Burnham, David A.; Martin, Larry D.; Larson, Peter L.; Bakker, Robert T. (2015). "The First Giant Raptor (Theropoda: Dromaeosauridae) from the Hell Creek Formation". Paleontological Contributions 14: 1–16. doi:10.17161/paleo.1808.18764. 
  32. ↑ Joyce, Christopher (2014-10-22). "Bigger Than A T. Rex, With A Duck's Bill, Huge Arms And A Hump" (in en). NPR. https://www.npr.org/2014/10/22/357622139/bigger-than-a-t-rex-with-a-ducks-bill-huge-arms-and-a-hump. 
  33. ↑ Longrich, Nicholas R.; Tokaryk, Tim; Field, Daniel J. (13 September 2011). "Mass extinction of birds at the Cretaceous–Paleogene (K–Pg) boundary". Proceedings of the National Academy of Sciences 108 (37): 15253–15257. doi:10.1073/pnas.1110395108. PMID 21914849. Bibcode: 2011PNAS..10815253L. 
  34. ↑ "Primitive Birds Shared Dinosaurs' Fate | Yale News" (in en). 2011-09-19. https://news.yale.edu/2011/09/19/primitive-birds-shared-dinosaurs-fate. 
  35. ↑ Padian, Kevin (18 March 2020). "Poultry through time" (in en). Nature 579 (7799): 351–352. doi:10.1038/d41586-020-00766-2. PMID 32188944. Bibcode: 2020Natur.579..351P. 
  36. ↑ Irazoqui, Facundo; Acosta Hospitaleche, Carolina; Paulina-Carabajal, Ariana; Bona, Paula; Vega, Nahuel (January 30, 2026). "New species of Vegavis (Neornithes) from Antarctica highlights unexpected Cretaceous Antarctic diversity" (in en). Diversity 18 (2): 82. doi:10.3390/d18020082. ISSN 1424-2818. 
  37. ↑ Wilton, Mark P. (2013). Pterosaurs: Natural History, Evolution, Anatomy. Princeton University Press. ISBN 0691150613.
  38. ↑ Barrett, P. M., Butler, R. J., Edwards, N. P., & Milner, A. R. (2008). Pterosaur distribution in time and space: an atlas. Zitteliana: 61–107.[1].
  39. ↑ Carroll, N. REASSIGNMENT OF MONTANAZHDARCHO MINOR AS A NON-AZHDARCHID MEMBER OF THE AZHDARCHOIDEA, SVP 2015.
  40. ↑ Agnolin, Federico L.; Varricchio, David (2012). "Systematic reinterpretation of Piksi barbarulna Varricchio, 2002 from the Two Medicine Formation (Upper Cretaceous) of Western USA (Montana) as a pterosaur rather than a bird". Geodiversitas 34 (4): 883–894. doi:10.5252/g2012n4a10. https://zenodo.org/record/5376780. 
  41. ↑ Longrich, Nicholas R.; Martill, David M.; Andres, Brian (2018). "Late Maastrichtian pterosaurs from North Africa and mass extinction of Pterosauria at the Cretaceous-Paleogene boundary". PLOS Biology 16 (3). doi:10.1371/journal.pbio.2001663. PMID 29534059. 
  42. ↑ Torsvik & Cocks 2017, p. 238.
  43. ↑ "GEOL 102 The Late Mesozoic: The Cretaceous". https://www.geol.umd.edu/~tholtz/G102/lectures/102cretaceous.html. 

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