Late Cretaceous

Short description: Subdivision of Cretaceous Period

Late/Upper Cretaceous

100.5 – 66.0 Ma

PreЄ

Chronology

Cretaceous graphical timeline

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Late J

Paleocene

Berriasian

Valanginian

Hauterivian

Barremian

Aptian

Albian

Cenoman.

Turonian

Coniacian

Santonian

Campanian

Maastricht.

K-Pg mass
extinction

Subdivision of the Cretaceous according to the ICS, as of 2021.[1]
Vertical axis scale: millions of years ago.

Etymology
Chronostratigraphic name| Upper Cretaceous
Geochronological name| Late Cretaceous
Name formality| Formal
Usage information
Celestial body| Earth
Regional usage| Global (ICS)
Time scale(s) used| ICS Time Scale
Definition
Chronological unit| Epoch
Stratigraphic unit| Series
Time span formality| Formal
Lower boundary definition| FAD of the Planktonic Foraminifer Rotalipora globotruncanoides
Lower boundary GSSP| Mont Risoux, Hautes-Alpes, France
[ ⚑ ] 44°23′33″N 5°30′43″E﻿ / ﻿44.3925°N 5.5119°E﻿ / 44.3925; 5.5119
GSSP ratified| 2002[2]
Upper boundary definition| Iridium enriched layer associated with a major meteorite impact and subsequent K-Pg extinction event.
Upper boundary GSSP| El Kef Section, El Kef, Tunisia
[ ⚑ ] 36°09′13″N 8°38′55″E﻿ / ﻿36.1537°N 8.6486°E﻿ / 36.1537; 8.6486
GSSP ratified| 1991

The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after creta, the Latin word for the white limestone known as chalk. The chalk of northern France and the white cliffs of south-eastern England date from the Cretaceous Period.[3]

## Contents

* 1 Climate
* 2 Geography
* 3 Vertebrate fauna
* 3.1 Non-avian dinosaurs
* 3.2 Birds
* 3.3 Pterosaurs
* 3.4 Mammals
* 3.5 Marine life
* 4 Flora
* 5 Cretaceous–Paleogene mass extinction discovery
* 6 See also
* 7 References

## Climate

During the Late Cretaceous, the climate was warmer than present, although throughout the period a cooling trend is evident.[4] The tropics became restricted to equatorial regions and northern latitudes experienced markedly more seasonal climatic conditions.[4]

## Geography

Late Cretaceous Map (Turonian)

Due to plate tectonics, the Americas were gradually moving westward, causing the Atlantic Ocean to expand. The Western Interior Seaway divided North America into eastern and western halves; Appalachia and Laramidia.[4] India maintained a northward course towards Asia.[4] In the Southern Hemisphere, Australia and Antarctica seem to have remained connected and began to drift away from Africa and South America.[4] Europe was an island chain.[4] Populating some of these islands were endemic dwarf dinosaur species.[4]

## Vertebrate fauna

### Non-avian dinosaurs

In the Late Cretaceous, the hadrosaurs, ankylosaurs, and ceratopsians experienced success in Asiamerica (Western North America and eastern Asia). Tyrannosaurs dominated the large predator niche in North America.[4] They were also present in Asia, although were usually smaller and more primitive than the North American varieties.[4] Pachycephalosaurs were also present in both North America and Asia.[4] Dromaeosaurids shared the same geographical distribution, and are well documented in both Mongolia and Western North America.[4] Additionally therizinosaurs (known previously as segnosaurs) appear to have been in North America and Asia. Gondwana held a very different dinosaurian fauna, with most predators being abelisaurids and carcharodontosaurids; and titanosaurs being among the dominant herbivores.[4] Spinosaurids were also present during this time.[5]

### Birds

Birds became increasingly common, diversifying in a variety of enantiornithe and ornithurine forms. Early Neornithes such as Vegavis[6] co-existed with forms as bizarre as Yungavolucris and Avisaurus.[7] Though mostly small, marine Hesperornithes became relatively large and flightless, adapted to life in the open sea.[8]

### Pterosaurs

Though primarily represented by azhdarchids, other forms like pteranodontids, tapejarids (Caiuajara and Bakonydraco), nyctosaurids and uncertain forms (Piksi, Navajodactylus) are also present. Historically, it has been assumed that pterosaurs were in decline due to competition with birds, but it appears that neither group overlapped significantly ecologically, nor is it particularly evident that a true systematic decline was ever in place, especially with the discovery of smaller pterosaur species.[9]

### Mammals

Several old mammal groups began to disappear, with the last eutriconodonts occurring in the Campanian of North America.[10] In the northern hemisphere, cimolodont, multituberculates, metatherians and eutherians were the dominant mammals, with the former two groups being the most common mammals in North America. In the southern hemisphere there was instead a more complex fauna of dryolestoids, gondwanatheres and other multituberculates and basal eutherians; monotremes were presumably present, as was the last of the haramiyidans, Avashishta.

Mammals, though generally small, ranged into a variety of ecological niches, from carnivores (Deltatheroida), to mollusc-eater (Stagodontidae), to herbivores (multituberculates, Schowalteria, Zhelestidae and Mesungulatidae) to highly atypical cursorial forms (Zalambdalestidae, Brandoniidae).

True placentals evolved only at the very end of the epoch; the same can be said for true marsupials. Instead, nearly all known eutherian and metatherian fossils belong to other groups. [11]

### Marine life

In the seas, mosasaurs suddenly appeared and underwent a spectacular evolutionary radiation. Modern sharks also appeared and penguin-like polycotylid plesiosaurs (3 meters long) and huge long-necked elasmosaurs (13 meters long) also diversified. These predators fed on the numerous teleost fishes, which in turn evolved into new advanced and modern forms (Neoteleostei). Ichthyosaurs and pliosaurs, on the other hand, became extinct during the Cenomanian-Turonian anoxic event.

## Flora

Near the end of the Cretaceous Period, flowering plants diversified. In temperate regions, familiar plants like magnolias, sassafras, roses, redwoods, and willows could be found in abundance.[4]

## Cretaceous–Paleogene mass extinction discovery

Main article: Earth:Cretaceous–Paleogene extinction event

The Cretaceous–Paleogene extinction event was a large-scale mass extinction of animal and plant species in a geologically short period of time, approximately 66 million years ago (Ma). It is widely known as the K–T extinction event and is associated with a geological signature, usually a thin band dated to that time and found in various parts of the world, known as the Cretaceous–Paleogene boundary (K–T boundary). K is the traditional abbreviation for the Cretaceous Period derived from the German name Kreidezeit, and T is the abbreviation for the Tertiary Period (a historical term for the period of time now covered by the Paleogene and Neogene periods). The event marks the end of the Mesozoic Era and the beginning of the Cenozoic Era.[12] "Tertiary" being no longer recognized as a formal time or rock unit by the International Commission on Stratigraphy, the K-T event is now called the Cretaceous—Paleogene (or K-Pg) extinction event by many researchers.

Asteroids of only a few kilometers wide can release the energy of millions of nuclear weapons when colliding with planets (artist's impression).

Non-avian dinosaur fossils are found only below the Cretaceous–Paleogene boundary and became extinct immediately before or during the event.[13] A very small number of dinosaur fossils have been found above the Cretaceous–Paleogene boundary, but they have been explained as reworked fossils, that is, fossils that have been eroded from their original locations then preserved in later sedimentary layers.[14][15][16] Mosasaurs, plesiosaurs, pterosaurs and many species of plants and invertebrates also became extinct. Mammalian and bird clades passed through the boundary with few extinctions, and evolutionary radiation from those Maastrichtian clades occurred well past the boundary. Rates of extinction and radiation varied across different clades of organisms.[17]

Many scientists hypothesize that the Cretaceous–Paleogene extinctions were caused by catastrophic events such as the massive asteroid impact that caused the Chicxulub crater, in combination with increased volcanic activity, such as that recorded in the Deccan Traps, both of which have been firmly dated to the time of the extinction event. In theory, these events reduced sunlight and hindered photosynthesis, leading to a massive disruption in Earth's ecology. A much smaller number of researchers believe the extinction was more gradual, resulting from slower changes in sea level or climate.[17]

## See also

* Flora and fauna of the Maastrichtian stage
* Hațeg Island

## References

1. ↑ Super User. "ICS - Chart/Time Scale". http://www.stratigraphy.org/index.php/ics-chart-timescale.
2. ↑ Kennedy, W.; Gale, A.; Lees, J.; Caron, M. (March 2004). "The Global Boundary Stratotype Section and Point (GSSP) for the base of the Cenomanian Stage, Mont Risou, Hautes-Alpes, France". Episodes 27: 21–32. doi:10.18814/epiiugs/2004/v27i1/003. https://stratigraphy.org/gssps/files/cenomanian.pdf. Retrieved 13 December 2020.
3. ↑ "Cretaceous Period | Definition, Climate, Dinosaurs, & Map" (in en). https://www.britannica.com/science/Cretaceous-Period.
4. ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 4.12 "Dinosaurs Ruled the World: Late Cretaceous Period." In: Dodson, Peter & Britt, Brooks & Carpenter, Kenneth & Forster, Catherine A. & Gillette, David D. & Norell, Mark A. & Olshevsky, George & Parrish, J. Michael & Weishampel, David B. The Age of Dinosaurs. Publications International, LTD. Pp. 103-104. ISBN 0-7853-0443-6.
5. ↑ Churcher, C. S; De Iuliis, G (2001). "A new species of Protopterus and a revision of Ceratodus humei (Dipnoi: Ceratodontiformes) from the Late Cretaceous Mut Formation of eastern Dakhleh Oasis, Western Desert of Egypt". Palaeontology 44 (2): 305–323. doi:10.1111/1475-4983.00181. Bibcode: 2001Palgy..44..305C.
6. ↑ Clarke, J.A.; Tambussi, C.P.; Noriega, J.I.; Erickson, G.M.; Ketcham, R.A. (2005). "Definitive fossil evidence for the extant avian radiation in the Cretaceous". Nature 433 (7023): 305–308. doi:10.1038/nature03150. PMID 15662422. Bibcode: 2005Natur.433..305C. http://www.digimorph.org/specimens/Vegavis_iaai/nature03150.pdf. Supporting information
7. ↑ Cyril A. Walker; Gareth J. Dyke (2009). "Euenantiornithine birds from the Late Cretaceous of El Brete (Argentina)". Irish Journal of Earth Sciences 27: 15–62. doi:10.3318/IJES.2010.27.15. http://www.ria.ie/RIA/files/40/40a4c454-eef2-4de0-922d-48ae0c42037f.pdf.
8. ↑ Larry D. Martin; Evgeny N. Kurochkin; Tim T. Tokaryk (2012). "A new evolutionary lineage of diving birds from the Late Cretaceous of North America and Asia". Palaeoworld 21: 59–63. doi:10.1016/j.palwor.2012.02.005.
9. ↑ Prondvai, E.; Bodor, E. R.; Ösi, A. (2014). "Does morphology reflect osteohistology-based ontogeny? A case study of Late Cretaceous pterosaur jaw symphyses from Hungary reveals hidden taxonomic diversity". Paleobiology 40 (2): 288–321. doi:10.1666/13030. Bibcode: 2014Pbio...40..288P. http://real.mtak.hu/21860/1/Prondvai_et_al.2014_reposit1_u_110445.946242.pdf.
10. ↑ Fox Richard C (1969). "Studies of Late Cretaceous vertebrates. III. A triconodont mammal from Alberta". Canadian Journal of Zoology 47 (6): 1253–1256. doi:10.1139/z69-196.
11. ↑ Halliday Thomas J. D. (2015). "Resolving the relationships of Paleocene placental mammals". Biological Reviews 92 (1): 521–550. doi:10.1111/brv.12242. PMID 28075073. PMC 6849585. http://discovery.ucl.ac.uk/1473028/1/Halliday_et_al-Biological_Reviews.pdf.
12. ↑ Fortey R (1999). Life: A Natural History of the First Four Billion Years of Life on Earth. Vintage. pp. 238–260. ISBN 978-0375702617.
13. ↑ "The extinction of the dinosaurs in North America". GSA Today 15 (3): 4–10. 2005. doi:10.1130/1052-5173(2005)015<4:TEOTDI>2.0.CO;2.
14. ↑ Sloan RE; Rigby K; Van Valen LM; Gabriel Diane (1986). "Gradual dinosaur extinction and simultaneous ungulate radiation in the Hell Creek formation". Science 232 (4750): 629–633. doi:10.1126/science.232.4750.629. PMID 17781415. Bibcode: 1986Sci...232..629S.
15. ↑ "Compelling new evidence for Paleocene dinosaurs in the Ojo Alamo Sandstone San Juan Basin, New Mexico and Colorado, USA". International Conference on Catastrophic Events and Mass Extinctions: Impacts and Beyond. 1053. Vienna, Austria. 9–12 July 2000. pp. 45–46. http://www.lpi.usra.edu/meetings/impact2000/pdf/3139.pdf.
16. ↑ Sullivan RM (May 8, 2003). "No Paleocene dinosaurs in the San Juan Basin, New Mexico". 35. 15. http://gsa.confex.com/gsa/2003RM/finalprogram/abstract_47695.htm.
17. ↑ 17.0 17.1 MacLeod N, Rawson PF, Forey PL, Banner FT, Boudagher-Fadel MK, Bown PR, Burnett JA, Chambers, P, Culver S, Evans SE, Jeffery C, Kaminski MA, Lord AR, Milner AC, Milner AR, Morris N, Owen E, Rosen BR, Smith AB, Taylor PD, Urquhart E, Young JR (1997). "The Cretaceous–Tertiary biotic transition". Journal of the Geological Society 154 (2): 265–292. doi:10.1144/gsjgs.154.2.0265. Bibcode: 1997JGSoc.154..265M.

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Geological history of Earth

Cenozoic era
(present–66.0 Mya)|

| Quaternary (present–2.588 Mya)|

* Holocene (present–11.784 kya)
* Pleistocene (11.784 kya–2.588 Mya)

|

Neogene (2.588–23.03 Mya)|

* Pliocene (2.588–5.333 Mya)
* Miocene (5.333–23.03 Mya)

Paleogene (23.03–66.0 Mya)|

* Oligocene (23.03–33.9 Mya)
* Eocene (33.9–56.0 Mya)
* Paleocene (56.0–66.0 Mya)

Mesozoic era
(66.0–251.902 Mya)|

| Cretaceous (66.0–145.0 Mya)|

* Late (66.0–100.5 Mya)
* Early (100.5–145.0 Mya)

|

Jurassic (145.0–201.3 Mya)|

* Late (145.0–163.5 Mya)
* Middle (163.5–174.1 Mya)
* Early (174.1–201.3 Mya)

Triassic (201.3–251.902 Mya)|

* Late (201.3–237 Mya)
* Middle (237–247.2 Mya)
* Early (247.2–251.902 Mya)

Paleozoic era
(251.902–541.0 Mya)|

| Permian (251.902–298.9 Mya)|

* Lopingian (251.902–259.8 Mya)
* Guadalupian (259.8–272.3 Mya)
* Cisuralian (272.3–298.9 Mya)

|

Carboniferous (298.9–358.9 Mya)|

* Pennsylvanian (298.9–323.2 Mya)
* Mississippian (323.2–358.9 Mya)

Devonian (358.9–419.2 Mya)|

* Late (358.9–382.7 Mya)
* Middle (382.7–393.3 Mya)
* Early (393.3–419.2 Mya)

Silurian (419.2–443.8 Mya)|

* Pridoli (419.2–423.0 Mya)
* Ludlow (423.0–427.4 Mya)
* Wenlock (427.4–433.4 Mya)
* Llandovery (433.4–443.8 Mya)

Ordovician (443.8–485.4 Mya)|

* Late (443.8–458.4 Mya)
* Middle (458.4–470.0 Mya)
* Early (470.0–485.4 Mya)

Cambrian (485.4–541.0 Mya)|

* Furongian (485.4–497 Mya)
* Miaolingian (497–509 Mya)
* Series 2 (509–521 Mya)
* Terreneuvian (521–541.0 Mya)

Proterozoic eon
(541.0 Mya–2.5 Gya)|

| Neoproterozoic (541.0 Mya–1 Gya)|

* Ediacaran (541.0–~635 Mya)
* Cryogenian (~635–~720 Mya)
* Tonian (~720 Mya–1 Gya)

|

Mesoproterozoic (1–1.6 Gya)|

* Stenian (1–1.2 Gya)
* Ectasian (1.2–1.4 Gya)
* Calymmian (1.4–1.6 Gya)

Paleoproterozoic (1.6–2.5 Gya)|

* Statherian (1.6–1.8 Gya)
* Orosirian (1.8–2.05 Gya)
* Rhyacian (2.05–2.3 Gya)
* Siderian (2.3–2.5 Gya)

Archean eon (2.5–4 Gya)|

| Eras|

* Neoarchean (2.5–2.8 Gya)
* Mesoarchean (2.8–3.2 Gya)
* Paleoarchean (3.2–3.6 Gya)
* Eoarchean (3.6–4 Gya)

|

Hadean eon (4–4.6 Gya)|

|  |

|

kya = thousands years ago. Mya = millions years ago. Gya = billions years ago.
See also: Geologic time scale

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