Paleocene ( /ˈpæliəˌsiːn, ˈpæ-, -lioʊ-/) or Palaeocene,
the "old recent", is a geologic epoch that lasted from about
66 to 56 million years ago. It is the first epoch of the
Paleogene Period in the modern
Cenozoic Era. As with many geologic
periods, the strata that define the epoch's beginning and end are well
identified, but the exact ages remain uncertain.
Paleocene Epoch is bracketed by two major events in Earth's
history. It started with the mass extinction event at the end of the
Cretaceous, known as the Cretaceous–
Paleogene (K–Pg) boundary.
This was a time marked by the demise of non-avian dinosaurs, giant
marine reptiles and much other fauna and flora. The die-off of the
dinosaurs left unfilled ecological niches worldwide. The Paleocene
ended with the Paleocene–
Eocene Thermal Maximum, a geologically
brief (~0.2 million year) interval characterized by extreme changes in
climate and carbon cycling.
The name "Paleocene" comes from
Ancient Greek and refers to the
"old(er)" (παλαιός, palaios) "new" (καινός, kainos) fauna
that arose during the epoch.
1 Boundaries and subdivisions
7 External links
Boundaries and subdivisions
The K–Pg boundary that marks the separation between
Paleocene is visible in the geological record of much of the Earth by
a discontinuity in the fossil fauna and high iridium levels. There is
also fossil evidence of abrupt changes in flora and fauna. There is
some evidence that a substantial but very short-lived climatic change
may have happened in the very early decades of the Paleocene. There
are several theories about the cause of the K–Pg extinction event,
with most evidence supporting the impact of a 10 km diameter
asteroid forming the buried
Chicxulub crater on the coast of Yucatan,
The end of the
Paleocene (~55.8 Ma) was also marked by a time of major
change, one of the most significant periods of global change during
the Cenozoic. The Paleocene–
Eocene Thermal Maximum upset oceanic
and atmospheric circulation and led to the extinction of numerous
deep-sea benthic foraminifera and a major turnover in mammals on land.
Paleocene is divided into three stages, the Danian, the Selandian
and the Thanetian, as shown in the table above. Additionally, the
Paleocene is divided into six
Paleocene was cooler and drier than the preceding
Cretaceous, though temperatures rose sharply during the
Eocene Thermal Maximum. The climate became warm and humid
worldwide towards the
Eocene boundary, with subtropical vegetation
Greenland and Patagonia, crocodilians swimming off the
coast of Greenland, and early primates evolving in the tropical palm
forests of northern Wyoming. The Earth's poles were cool and
temperate; North America, Europe,
Australia and southern South America
were warm and temperate; equatorial areas had tropical climates; and
north and south of the equatorial areas, climates were hot and
arid, not dissimilar to today's global desert belts around 30
degrees northern and southern latitude.
In many ways, the
Paleocene continued processes that had begun during
Cretaceous Period. During the Paleocene, the continents
continued to drift toward their present positions. Supercontinent
Laurasia had not yet separated into three continents -
Greenland were still connected,
North America and
Asia were still
intermittently joined by a land bridge, while
Greenland and North
America were beginning to separate. The
Laramide orogeny of the
Cretaceous continued to uplift the
Rocky Mountains in the
American west, which ended in the succeeding epoch.
North America remained separated by equatorial seas (they
joined during the Neogene); the components of the former southern
Gondwanaland continued to split apart, with Africa,
Australia pulling away from each other.
Africa was heading north towards Europe, slowly closing the Tethys
India began its migration to
Asia that would lead to a
tectonic collision and the formation of the Himalayas.
The inland seas in
North America (Western Interior Seaway) and Europe
had receded by the beginning of the Paleocene, making way for new
land-based flora and fauna.
Warm seas circulated throughout the world, including the poles. The
Paleocene featured a low diversity and abundance of marine
life, but this trend reversed later in the epoch. Tropical
conditions gave rise to abundant marine life, including coral reefs.
With the demise of marine reptiles at the end of the Cretaceous,
sharks became the top predators. At the end of the Cretaceous, the
ammonites and many species of foraminifera became extinct.
Marine fauna also came to resemble modern fauna, with only the marine
mammals and the
Carcharhinid sharks missing.
Paleocene strata immediately overlying the K–Pg boundary
is in places marked by a "fern spike": a bed especially rich in fern
fossils. Ferns are often the first species to colonize areas
damaged by forest fires; thus the fern spike may indicate
Chicxulub crater devastation.
In general, the
Paleocene is marked by the development of modern plant
species. Cacti and palm trees appeared.
Paleocene and later plant
fossils are generally attributed to modern genera or to closely
The warm temperatures worldwide gave rise to thick tropical,
sub-tropical and deciduous forest cover around the globe (the first
recognizably modern rainforests) with ice-free polar regions covered
with coniferous and deciduous trees. With no large browsing
dinosaurs to thin them,
Paleocene forests were probably denser than
those of the Cretaceous.
Flowering plants (angiosperms), first seen in the Cretaceous,
continued to develop and proliferate, and along with them coevolved
the insects that fed on these plants and pollinated them.
Life restoration of Titanoides
Mammals had first appeared in the Late Triassic, evolving from
advanced cynodonts, and developed alongside the dinosaurs, exploiting
ecological niches untouched by the larger and more famous Mesozoic
animals: in the insect-rich forest underbrush and high up in the
trees. These smaller mammals (as well as birds, reptiles, amphibians,
and insects) survived the mass extinction at the end of the Cretaceous
which wiped out the non-avian dinosaurs, and mammals diversified and
spread throughout the world.
While early mammals were small nocturnal animals that mostly ate soft
plant material and small animals such as insects, the demise of the
non-avian dinosaurs and the beginning of the
Paleocene saw mammals
growing bigger and occupying a wider variety of ecological niches. Ten
million years after the death of the non-avian dinosaurs, the world
was filled with rodent-like mammals, medium-sized mammals scavenging
in forests, and large herbivorous and carnivorous mammals hunting
other mammals, birds, and reptiles.
Fossil evidence from the
Paleocene is scarce, and there is relatively
little known about mammals of the time. Because of their small size
(constant until late in the epoch) early mammal bones are not well
preserved in the fossil record, and most of what we know comes from
fossil teeth (a much tougher substance), and only a few skeletons.
The brain to body mass ratios of these archaic mammals were quite
Mammals of the
Monotremes: The ornithorhynchid Obdurodon sudamericanum, in the family
that includes the platypus, is the only monotreme known from the
Marsupials: modern kangaroos are marsupials, characterized by giving
birth to embryonic young, who crawl into the mother's pouch and suckle
until they are developed. The Bolivian
Pucadelphys andinus and the
North American Peradectes are two
Multituberculates: the only major branch of mammals to become extinct
since the K–Pg boundary, this rodent-like grouping includes the
Placentals: this grouping of mammals became the most diverse and the
most successful. Members include primates, plesiadapids,
proboscideans, and hoofed ungulates, including the condylarths and the
Section of an
Because of the climatic conditions of the Paleocene, reptiles were
more widely distributed over the globe than at present. Among the
sub-tropical reptiles found in
North America during this epoch are
champsosaurs (fully aquatic reptiles), crocodilia, soft-shelled
turtles, palaeophid snakes, varanid lizards, and Protochelydra
zangerli (similar to modern snapping turtles).
Examples of champsosaurs of the
the largest champsosaur ever discovered. This creature was unusual
Paleocene non-squamate reptiles in that C. gigas became larger
than its known
Mesozoic ancestors: C. gigas is more than twice the
length of the largest
Cretaceous specimens (3 meters versus 1.5
meters). Another genus, Simoedosaurus, was similarly large; it appears
rather suddenly in the fossil record, as its closest relatives
occurred in the Early Cretaceous.
Reptiles as a whole decreased in
size after the K–Pg event. Champsosaurs declined towards the end of
Paleocene and became extinct during the Miocene.
Wannaganosuchus, a crocodilian from the Paleocene.
Paleocene crocodylians are
Leidyosuchus) formidabilis, the apex predator and the largest animal
Wannagan Creek fauna, and the alligatorid Wannaganosuchus.
Non-avian dinosaurs may have survived to some extent into the early
Danian stage of the
Paleocene Epoch circa 64.5 Mya. The controversial
evidence for such is a hadrosaur leg bone found from
in New Mexico; but such stray late forms may be derived
Several species of snakes, such as
Titanoboa and Gigantophis, grew to
over 6 meters long.
Birds began to re-diversify during the epoch, occupying new niches.
Genetic studies suggest that nearly all modern bird clades can trace
their origin to this epoch, with
Neornithes having undergone an
extremely fast, "star-like" radiation of species in the early
Palaeocene in response to the vacancy of niches left by the KT
Large flightless birds have been found in late
including the omnivorous
Europe and carnivorous terror
birds in South America, the latter of which survived until the
In the late Paleocene, early owl types appeared, such as
United States and
Berruornis in France.
^ "ICS - Chart/Time Scale". www.stratigraphy.org.
^ Jones, Daniel (2003) , Peter Roach, James Hartmann and Jane
Setter, eds., English Pronouncing Dictionary, Cambridge: Cambridge
University Press, ISBN 3-12-539683-2 CS1 maint: Uses editors
^ "Paleocene". Online Etymology Dictionary.
^ Gavin A. Schmidt and Drew T. Shindell (2003). "Atmospheric
composition, radiative forcing, and climate change as a consequence of
a massive methane release from gas hydrates" (PDF). Paleoceanography.
18 (1). Bibcode:2003PalOc..18.1004S.
doi:10.1029/2002PA000757. CS1 maint: Uses authors parameter
^ "Science Notes 2003:". Scicom.ucsc.edu. Retrieved 2012-08-28.
Paleocene Climate". PaleoMap Project. Retrieved 2012-08-28.
^ a b c d Hooker, J.J., "Tertiary to Present: Paleocene", pp. 459-465,
Vol. 5. of Selley, Richard C., L. Robin McCocks, and Ian R. Plimer,
Encyclopedia of Geology, Oxford: Elsevier Limited, 2005.
^ Vajda, Vivi. "Global Disruption of Vegetation at the
Cretaceous-Tertiary Boundary – A Comparison Between the Northern and
Southern Hemisphere Palynological Signals". Gsa.confex.com. Retrieved
^ Bigelow, Phillip. "The K–T boundary In The Hell Creek Formation".
Scn.org. Archived from the original on 2006-07-12. Retrieved
^ Stephen Jay Gould, ed., The Book of Life (New York: W.W. Norton
& Company, 1993), p. 182.
^ Kazlev, M. Alan (2002) "The Paleocene". Palaeos Cenozoic. Retrieved
April 3, 2013.
^ Musser, A. M. (2003). "Review of the monotreme fossil record and
comparison of palaeontological and molecular data". Comparative
Biochemistry and Physiology A. 136: 927–942.
doi:10.1016/s1095-6433(03)00275-7. Retrieved April 3, 2013.
^ Fassett, JE, Lucas, SG, Zielinski, RA, and Budahn, JR (2001).
"Compelling new evidence for
Paleocene dinosaurs in the Ojo Alamo
Sandstone, San Juan Basin, New
Mexico and Colorado, USA" (PDF).
Catastrophic events and mass extinctions, Lunar and Planetary
Contribution. 1053: 45–46. Retrieved 2007-05-18. CS1 maint:
Multiple names: authors list (link)
^ Sullivan, RM (2003). "No
Paleocene dinosaurs in the San Juan Basin,
New Mexico". Geological Society of America Abstracts with Programs. 35
(5): 15. Retrieved 2007-07-02.
^ Linnéa Smeds, Hans Ellegren, The Dynamics of Incomplete Lineage
Sorting across the Ancient Adaptive Radiation of Neoavian Birds
Ogg, Jim (June 2004). "Overview of Global Boundary Stratotype Sections
and Points (GSSP's)". Stratigraphy.org. Retrieved December 22,
Wikimedia Commons has media related to Paleocene.
Wikisource has original works on the topic: Cenozoic#Paleogene
BBC Changing Worlds: Paleocene
Paleocene Evolutionary Radiation
John Alroy, "Evidence of a
Paleocene Evolutionary Radiation"
Paleocene Microfossils: 35+ images of Foraminifera
Petrified Wood Museum Palaeocene introduction
Geologic history of Earth
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)
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)
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)
Series 3 (497–509 Mya)
Series 2 (509–521 Mya)
Terreneuvian (521–541.0 Mya)
(541.0 Mya–2.5 Gya)
Neoproterozoic era (541.0 Mya–1 Gya)
Ediacaran (541.0-~635 Mya)
Cryogenian (~635-~720 Mya)
Tonian (~720 Mya-1 Gya)
Mesoproterozoic era (1–1.6 Gya)
Stenian (1-1.2 Gya)
Ectasian (1.2-1.4 Gya)
Calymmian (1.4-1.6 Gya)
Paleoproterozoic era (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 eon² (2.5–4 Gya)
Neoarchean (2.5–2.8 Gya)
Mesoarchean (2.8–3.2 Gya)
Paleoarchean (3.2–3.6 Gya)
Eoarchean (3.6–4 Gya)
Hadean eon² (4–4.6 Gya)
kya = thousands years ago. Mya = millions years ago.
Gya = billions
years ago.¹ =
Phanerozoic eon. ² =
Source: (2017/02). International Commission on Stratigraphy. Retrieved
13 July 2015. Divisions of Geologic Time—Major Chronostratigraphic
and Geochronologic Units USGS Retrieved 10 March 2013.