HOME

TheInfoList



OR:

Olson's Extinction was a
mass extinction An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp fall in the diversity and abundance of multicellular organisms. It occ ...
that occurred in the late
Cisuralian The Cisuralian, also known as the Early Permian, is the first series/epoch of the Permian. The Cisuralian was preceded by the Pennsylvanian and followed by the Guadalupian. The Cisuralian Epoch is named after the western slopes of the Ural Mou ...
or early
Guadalupian The Guadalupian is the second and middle Series (stratigraphy), series/Epoch (geology), epoch of the Permian. The Guadalupian was preceded by the Cisuralian and followed by the Lopingian. It is named after the Guadalupe Mountains of New Mexico an ...
epoch of the
Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...
period, predating the much larger
Permian–Triassic extinction event The Permian–Triassic extinction event (also known as the P–T extinction event, the Late Permian extinction event, the Latest Permian extinction event, the End-Permian extinction event, and colloquially as the Great Dying,) was an extinction ...
. The event is named after American paleontologist Everett C. Olson, who first identified the gap in fossil record indicating a sudden change between the early Permian and middle/
late Permian Late or LATE may refer to: Everyday usage * Tardy, or late, not being on time * Late (or the late) may refer to a person who is dead Music * ''Late'' (The 77s album), 2000 * Late (Alvin Batiste album), 1993 * Late!, a pseudonym used by Dave Groh ...
faunas. Some authors also place a hiatus in the continental fossil record around that time, but others disagree. This event has been argued by some authors to have affected many taxa, including embryophytes, marine metazoans, and
tetrapod A tetrapod (; from Ancient Greek :wiktionary:τετρα-#Ancient Greek, τετρα- ''(tetra-)'' 'four' and :wiktionary:πούς#Ancient Greek, πούς ''(poús)'' 'foot') is any four-Limb (anatomy), limbed vertebrate animal of the clade Tetr ...
s.


Identification

The first evidence of extinction came when Everett C. Olson noted a hiatus between early Permian faunas dominated by
pelycosaurs Pelycosaur ( ) is an older term for basal or primitive Late Paleozoic synapsids, excluding the therapsids and their descendants. Previously, the term mammal-like reptile was used, and Pelycosauria was considered an order, but this is now thoug ...
and therapsid-dominated faunas of the middle and late Permian. First considered to be a preservational gap in the fossil record, the event was originally dubbed 'Olson's Gap'. To compound the difficulty in identifying the cause of the 'gap', researchers were having difficulty in resolving the uncertainty which exists regarding the duration of the overall extinction and about the timing and duration of various groups' extinctions within the greater process. Theories emerged which suggested the extinction was prolonged, spread out over several million years or that multiple extinction pulses preceded the Permian–Triassic extinction event. The impact of Olson's Extinction amplified the effects of the Permian–Triassic extinction event and the final extinction killed off only about 80% of species alive at that time while the other losses occurred during the first pulse or the interval between pulses. During the 1990s and 2000s researchers gathered evidence on the biodiversity of plants, marine organisms and tetrapods that indicated an extinction pulse preceding the Permian–Triassic extinction event had a profound impact on life on land. On land Sahney and Benton showed that even discounting the sparse fossil assemblages from the extinction period, the event can be confirmed by the stages of time bracketing the event since well preserved sections of the fossil record from both before and after the event have been found and they referred to the event as 'Olson's Extinction'. The 'Gap' was finally closed in 2012 when Michael Benton confirmed that the terrestrial fossil record of the Middle Permian is well represented by fossil localities in the American Southwest and European Russia and that the gap is not an artifact of a poor rock record since there is no correlation between geological and biological records of the Middle Permian. Despite the closure of Olson's Gap, the presence of an extinction event at the
Kungurian In the geologic timescale, the Kungurian is an age or stage of the Permian. It is the latest or upper of four subdivisions of the Cisuralian Epoch or Series. The Kungurian lasted between and million years ago (Ma). It was preceded by the Arti ...
Roadian In the geologic timescale, the Roadian is an age or stage of the Permian. It is the earliest or lower of three subdivisions of the Guadalupian Epoch or Series. The Roadian lasted between and million years ago (Ma). It was preceded by the Kun ...
boundary was still disputed. It was argued that the observed decrease in diversity might be due to the shift in the location of greatest sample size from the palaeo-equatorial to the palaeo-temperate regions: equatorial regions tend to have a higher diversity in most modern groups. However, a thorough review of the tetrapod-bearing formations during the Kungurian and the Roadian found evidence that the faunal turnover at this time is not a result of the shift in sampling locality; the early Permian temperate faunas are more similar to the early Permian equatorial faunas than the middle Permian temperate faunas. It was also shown that throughout the Permian, the highest diversity was found in temperate regions rather than equatorial regions, and therefore the fall in diversity could not be due to increased sampling of temperate latitudes.


Possible causes

There is no widely accepted theory for the cause of Olson's Extinction. Recent research has indicated that climate change may be a possible cause: extreme environments were observed from the Permian of Kansas which resulted from a combination of hot climate and acidic waters particularly coincident with Olson's Extinction.


Extinction patterns


On land


Plants

Plants showed large turnover in the mid-to-late Permian and into the Triassic. The duration of higher extinction rates (>60%) in land plants was about 23.4 Myr, starting from Olson's Extinction and into the early Middle Triassic. Olson's Extinction represents the third highest peak of extinction rates seen in plants throughout the Paleozoic, and the number of genera fell by 25%. The extinction was particularly severe among free-sporing plants; seed plants seem to have been largely unaffected.


Tetrapods

The Permian was a time of rapid change for tetrapods; in particular there was a major changeover from faunas dominated by basal synapsids ("
pelycosaurs Pelycosaur ( ) is an older term for basal or primitive Late Paleozoic synapsids, excluding the therapsids and their descendants. Previously, the term mammal-like reptile was used, and Pelycosauria was considered an order, but this is now thoug ...
”) and reptiliomorphs (''
Diadectes ''Diadectes'' (meaning ''crosswise-biter'') is an extinct genus of large reptiliomorphs or synapsids that lived during the early Permian period ( Artinskian- Kungurian stages of the Cisuralian epoch, between 290 and 272 million years ago). ''Dia ...
'') to faunas dominated by therapsids (
Dinocephalia Dinocephalians (terrible heads) are a clade of large-bodied early therapsids that flourished in the Early and Middle Permian between 279.5 and 260 million years ago (Ma), but became extinct during the Capitanian mass extinction event. ...
, Anomodontia,
Gorgonopsia Gorgonopsia (from the Greek Gorgon, a mythological beast, and 'aspect') is an extinct clade of Saber-toothed predator, sabre-toothed therapsids from the Middle Permian, Middle to the Upper Permian, roughly between 270 and 252 million years ago. ...
, and
Cynodontia Cynodontia () is a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 mya), and extensively diversified after the Permian–Triassic extinction event. Mammals are cynodonts, as are their extinct ances ...
); the cynodonts were direct ancestors of mammals. In 2008 Sahney and Benton confirmed that this was not just a turnover (gradual replacement of one faunal complex by another) but a real extinction event in which a significant drop in the biodiversity of tetrapods on a global scale and community level occurred. The extinction may have taken place in two phases:
Edaphosauridae Edaphosauridae is a family of mostly large (up to or more) Late Carboniferous to Early Permian synapsids. Edaphosaur fossils are so far known only from North America and Europe. Characteristics They were the earliest known herbivorous amniotes ...
and
Ophiacodontidae Ophiacodontidae is an extinct family of early synapsids from the Carboniferous and Permian. '' Archaeothyris'', and '' Clepsydrops'' were among the earliest ophiacodontids, appearing in the Late Carboniferous. Ophiacodontids are among the most b ...
died out around the Kungurian–Roadian boundary, while Caseidae and Therapsida diversified; later in the Roadian or slightly later
Sphenacodontidae Sphenacodontidae (Greek: "wedge point tooth family") is an extinct family (biology), family of sphenacodontoidea, sphenacodontoid synapsids. Small to large, advanced, carnivore, carnivorous, Late Pennsylvanian to Guadalupian, middle Permian "pelyc ...
died out, although this was apparently the result of a slow decline over 20 Ma, which spanned from the Sakmarian through the
Kungurian In the geologic timescale, the Kungurian is an age or stage of the Permian. It is the latest or upper of four subdivisions of the Cisuralian Epoch or Series. The Kungurian lasted between and million years ago (Ma). It was preceded by the Arti ...
, and Caseidae also went into decline, over an even longer period. Olson's extinction appears to have been the highest Paleozoic peak in extinction rate observed in
Eureptilia Sauropsida (Greek for "lizard faces") is a clade of amniotes, broadly equivalent to the class Reptilia, though typically used in a broader sense to also include extinct stem-group relatives of modern reptiles and birds (which, as theropod dinos ...
, exceeding even the Permian–Triassic mass extinction.
Temnospondyls Temnospondyli (from Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') or temnospondyls is a diverse ancient order of small to giant tetrapods—often considered primitive amphibians—that flourished wo ...
were also particularly hard-hit. In December 2011, the fossilized remains of the 'youngest' pelycosaur was described by Modesto ''et al.'' as from 260 million years ago in South Africa. This, and slightly older remains of varanopids, documents the fact that this clade, like some caseids, survived Olson's Extinction. This type of animal is called a disaster taxon, an organism that survives a major environmental disruption, perhaps forming the basis for a new adaptive radiation.


In the water


Fish

Extinction rates in fish increased noticeably between the
Cisuralian The Cisuralian, also known as the Early Permian, is the first series/epoch of the Permian. The Cisuralian was preceded by the Pennsylvanian and followed by the Guadalupian. The Cisuralian Epoch is named after the western slopes of the Ural Mou ...
and the Guadalupian, the time of Olson's extinction. However, origination rates also rose, and so there does not appear to have been any substantial decrease in
species richness Species richness is the number of different species represented in an community (ecology), ecological community, landscape or region. Species richness is simply a count of species, and it does not take into account the Abundance (ecology), abunda ...
. Using data on chondrichthyan diversity, Koot showed that there was little substantial decline in diversity until the middle of the Guadalupian.Koot, M.B. 2013. Effects of the late Permian mass extinction on chondrichthyan palaeobiodiversity and distribution patterns


Recovery

Fauna did not recover fully from Olson's Extinction before the impact of the Permian-Triassic extinction event. Estimates of recovery time vary, where some authors indicated recovery was prolonged, lasting 30 million years into the Triassic. Several important events took place during Olson's Extinction, most notably the rise of therapsids, a group of sphenacodontoid
synapsid Synapsida is a diverse group of tetrapod vertebrates that includes all mammals and their extinct relatives. It is one of the two major clades of the group Amniota, the other being the more diverse group Sauropsida (which includes all extant rept ...
s that includes the evolutionary ancestors of mammals. Further research on the recently identified primitive therapsid of the Xidagou Formation (Dashankou locality) in China of Roadian age may provide more information on this topic.


References


Further reading


io9.com: "Why did nearly all life on Earth die 250 million years ago ?"


{{ExtEvent nav Extinction events Guadalupian life Permian North America