An Ancient Pack Hunter or Evidence of Juvenile Gregarious Behavior

 

D. quartacolonia is a relatively cute little archosaur; but is that because it was still a baby?

 In the Middle Triassic, around 240 million years ago, a few lovely animals were in the same place at the wrong time. Swept up by a flood event or something similar, they were transported a short distance and rapidly buried before they could attempt to escape. Their remains were not scavenged and are wonderfully preserved, providing the basis for a series of studies on the frankly very underrated specimen! We hear often about the Fighting Dinosaurs and the Dueling Dinosaurs and the Babysitting Dinosaurs... a lot of dinosaurs. But there is surprisingly little attention, from the press or otherwise, on this bonebed, a single fossil unit that preserves ten Decuriasuchus quartacolonia in three dimensions, and in various degrees of articulation (articulated specimens are those where the bones are connected, rather than scattered randomly, like you would find in a flowing riverbed.) 

 Another interesting, but not so surprising, feature of the animals in the bonebed is their apparent age. The Decuriasuchus preserved here are all relatively young, and far from their maximum size. An unfortunate consequence of this is that there is a serious dearth of reconstructions of adult Decuriasuchus; and mine is no exception. I based it solely on the material present in the paper, so it represents a juvenile. This means the adult appearance of Decuriasuchus is a potential mystery. I say potential because of certain ideas I will discuss later. 

Anatomy and a Brief Rant about Osteoderms 

Regardless, the anatomy of the animal is interesting; like many archosaurs today, it's got a really long tail compared to its overall body length. In the extant croc-line archosaurs, the tail is a propulsor for aquatic movement, but that does not seem to be the case with Decuriasuchus given the construction of its skull: Eyes on the side and forward-oriented nostrils coupled with a tall cranium and recurved teeth do not a good aquatic hunter make. So it's bizarre to see an ancient, terrestrial archosaur that has such a long tail. It shares some other similarities with our modern crocs, too, despite its age. It's got dorsal osteoderms that form a nice plate of armor atop its body, but they are generally simple in structure and not as ornamented as the living crocs or some of their extinct relatives like the aetosaurs. They are simple plates and cover the back and stomach, probably offering protection from predators and rival Decuriasuchus. They are found in sets of four along the back, where they are well preserved. On the lower side of the tail the other set of osteoderms, which are comparatively less nicely fossilized. Frustratingly, the description paper glosses over the preserved osteoderms, which I do not appreciate.[1] There is plentiful information to be found in an osteoderm, even in a cursory description; are they smooth? Rough? Do they vary in size up or down the tail? They are abundant, why not cut one or two in half and do some histology. Some data suggests that the structure, internal and external, of osteoderms could be a proxy for lifestyle... with good analysis we could 'confirm' that Decuriasuchus was likely terrestrial.[2] While the paper that reports on the trend of osteoderm ornamentation loss in terrestrial pseudosuchians suggests that ornamented osteoderms help swimming pseudosuchians heat themselves up faster, I am somewhat skeptical of this idea. I do agree that the osteoderms play an important role in thermoregulation; they are demonstrated to do so. However, I think that this correlation may have less to do with lifestyle in relation to aquatic activity and more to do with endo/ectothermy. But that's a conversation for another day. 

 Juvenile Gregarious Behavior and the Identity of Decuriasuchus

 Many species of archosaurs group together when young but live more solitary lives as adults. Aetosaurus ferratus individuals are known to group together for a time after hatching,[3] and Diplodocus from the Mothers' Day site in the Morrison Formation represent a sauropod herd comprised exclusively of subadult individuals. This is not abnormal for reptiles, who grow slowly and consistently rather than rapidly like mammals. There would be little survival advantage to staying with your parents when you are large enough to sustain yourself by foraging but not large enough to eat the same material. This is called ontogenetic niche shift, a phenomenon often talked about in Tyrannosaurus rex but far from unique to it. In some species, this niche shift means that parents and offspring barely resemble each other morphologically...

 ...so how do we know we haven't already found an adult Decuriasuchus? We don't. It would be reckless to try matching it willy-nilly to any large predatory archosaur from the area, but there's a surprisingly compelling argument that it's a juvenile Prestosuchus. Firstly, a good amount of the percieved difference in skull shape is due to taphonomic deformation. This seems to be the case mainly because all of the preserved skulls are quite strikingly different in shape from one another, but only the best-preserved one is present in most skeletals. This one is quite compressed dorsoventrally and probably does not quite represent the animal's skull shape in vivo. The skull of Decuriasuchus is still markedly similar to that of the other prestosuchids, though. Perhaps the most compelling evidence for the idea that Decuriasuchus represents a juvenile Prestosuchus is the presence of adult Prestosuchus in the same outcrop and the similarity of their bone development. [4] This issue, however, is far from resolved. Prestosuchus chiniquensis is an animal with diagnostic traits associated mainly with the postcrania, while Decuriasuchus's diagnostic traits are only associated with the skull. This is another issue I have with the description paper. The best way to resolve this issue, in my opinion, is an updated description of D. quartacolonia that takes good care to comment on the abundance of postcranial material from this species.  

There are a lot of questions to be asked about this animal, and in a situation rare in paleontology, the specimens are available to answer a few of them! Decuriasuchus deserves a lot more attention than it's getting, especially compared to its dinosaur relatives. So my message is, as always, to give some more love to the Pseudosuchians. 

 

Who Am I?

 

 Hello!

 

 

 Majungasaurus and I at Dino Shindig 2025.

I'm an early-career researcher with experience in a few areas of archosaur paleontology. I like to talk about weird guys from the Triassic and birds occasionally.  

This is a place for me to publish my work, be it opinion, fun facts, or art. Nothing here is peer reviewed. Please do not cite it for research. This is a place for my opinions and ideas, as well as sharing facts about the natural world. I cite my sources to try keeping everything accurate, but there's nobody besides me checking for that and so of course, this work is subject to bias. Rather than a serious scientific repository, this is my little space to talk about things I find interesting. 

With that, I hope you enjoy. 

The Triassic Bigfoot

Ctenosauriscus koeneni

One of the most bizarre archosaurs of the Early Triassic is Ctenosauriscus. It's a strange looking predatory animal with few body fossils, a complicated taxonomic history, and a sail along its back (sound familiar, Spinosaurus..?) Ctenosauriscus is, despite all that, one of the most well known members of the group ctenosauriscidae. The others are extraordinarily fragmentary bar Arizonasaurus, and not a single complete specimen has ever been found. They are some of the oldest archosaurs out there, with Xilousuchus (pictured below) being potentially the oldest archosaur, full stop. It's from a fossil formation in China, dated to ~247 million years old.

Xilousuchus saipingensis

 Ctenosauriscus is the largest member of the group, with the only specimen known hitting about ten feet in length and the tip of the sail being around three and a half feet tall. Not exactly terrifying, Jurassic-Park-Monster sized, so our potential for a ctenosauriscid horror movie antagonist is unfortunately slim... That is, if you stick to body fossils. C. Deidrich described a series of footprints in Northern Germany that he suggested belonged to a relative of Ctenosauriscus, associated with the ichnospecies Isochirotherium herculis. (Ichnospecies are specific kinds of ichnofossils, like how a species is a kind of living thing. An ichnofossil is a 'trace fossil,' like a footprint, burrow, or poop left by an extinct organism.) In this case, the animal that left the trace fossils, called their Trackmaker, was gigantic, especially for the time. It moved in a big straight line across a dried up seabed, where there were several tracks left by meandering, smaller animals. Due to the clearly meat-focused dentition of the Ctenosauriscids, it's reasonable to suggest that the trackmaker might have preyed upon the small archosaurs in the area. Another fun detail (with little relevance, I'll admit) is that there are bits of a nothosaur, a marine reptile, stuck inside one of the footprints, which is just a fantastic mental image. Either the little guy was stepped on, or more likely, washed into the footprint by the tide when it returned. 

So how big really was our giant Triassic trackmaker? Using Arizonasaurus as a model, the author of the paper suggested a maximum size of 5-6 meters for the giant poposauroid. For my American Friends, that's about 17-20 feet long. It's no T. rex or Allosaurus, but it's certainly an animal large enough to be scary. The implied presence of a dorsal sail also makes it look a lot bigger in size estimation charts. Obviously we can't know if it was there, but since all members of the ctenosauriscidae have it, there's no reason I. herculis's trackmaker would lack the distinctive feature. Below are Ctenosauriscus and the giant mystery beast (in dark and light grey respectively) compared to an average-height human. The grid squares are 1 Meter each.

 Ctenosauriscus, the I. herculis trackmaker, and Homo.

 

Now that looks movie-monster sized, and it's plausible without having to drastically increase the size of a real animal like in Jurassic Park. Though I can't say it's particularly plausible for one of these guys to be running around eating people in a theme park. You'll need to come up with a scientific justification for that one yourself.  

 

 

 

Late Paleozoic and Mesozoic Interannual Weather Patterns are Consistent With but do not Confirm High-Amplitude ENSO Variation at the End Permian and Throughout the Mesozoic

 

Introduction

Modern extreme weather events on a local scale are capable of severely depopulating or causing local extinction and extirpation of a variety of species.[1] This is certainly true of warming events, both locally and on a global scale.[2] [3] Efforts to identify and connect the impacts of rapid warming with the decline of species have been made difficult in the past by a lack of apparent direct cause, but indirect causes like increased pathogen transmission and reduced host body size are correlated strongly with a warming climate and can be attributed to warming events.[4] Sporadic but repetitive warming events in recent history, such as the one leading to the extinction of fig-pollinating wasps in Borneo, have been linked to rapid and unusually hot El Niño events.[5]

El Niño events are a component of the El Niño Southern Oscillation (ENSO). ENSO is a broad term which describes the interannual variation of the pacific ocean’s (or its historical equivalent’s) surface temperature and the associated warming or cooling of land areas due to land-sea teleconnections.[6] Most of the earth’s surface is affected by some form of climate teleconnection that fosters interannual variation and leads to non-seasonal climate extremes.[7] The mechanisms by which ENSO operates are numerous but it is key to recognize temperature teleconnections enabled by the transference of hot air from warm, convective regions to subsident regions where air descends into low pressure zones.⁶ Additionally, these teleconnections are supported by poleward air movement from tropical to extratropical zones.[8] The most important effect of the various alterations in air and ocean pressure and/or temperature is the generation of a positive feedback loop which the atmospheric temperature and sea surface temperature exacerbate each other.[9] Feedback loops are key in generating extreme local and global ecological conditions which lead to mass extinctions.[10]

Extinctions are common throughout Earth’s history, but the Permo-Triassic mass extinction is one of, if not the most ecologically devastating.[11] Almost all species, both terrestrial and aquatic, were lost, and the ecology of the ensuing Triassic period was shaped by the survivors of what many refer to as ‘The Great Dying.’[12] The pre-extinction period is geographically characterized by the expansive and flat supercontinent Pangea and the single, worldwide ocean Panthalassa.[13] The ecology of the Permian was characterized by a variety of unique and largely extinct floral and faunal groups. The Nothosouthamerican biosphere of the Permian was characterized not by vast and empty deserts, as is frequently depicted in media and paleoart, but by a series of distinct, sometimes glacial environments with diverse plant life and various depositional environments. Afro-Indian deposits show sparse plant life associated with extreme conditions and potential glacial influence. Endemism is relatively low across the Afro-Indian Permian strata. Australian deposits lack diversity as well, and have no endemic taxa. At the end of the Permian, African deposits indicate an ecological gradient between the western and eastern sides of Pangea. Changes in plant diversity indicate a west to east migration of arid conditions across the supercontinent.[14] ENSO is strongly influenced by local and global geographical conditions and events such as ocean temperature changes, mountain uplift, and  radiative volcanic heat can amplify or modulate the manifestation of interannual temperature extremes.[15]

 

The faunal composition of the latest Permian was characterized by instability among the highest trophic levels, with predatory taxa rapidly emerging and becoming extinct. Movement of Inostrancevia sp. from Russian to African Pangea is regarded to be symptomatic of locale extinctions prior to the Permo-Triassic boundary and consistent with the early extirpation of large land predators in response to extinction-threatening events, a trend prominent in the fossil record.[16]

Rapid and relatively cosmopolitan changes in temperature and precipitation are not uncommon throughout geological time, and are often associated with mass extinctions.[17] [18] [19] However, these world warming events are not unique to large-scale extinction, and there is little understanding of the factors which predispose the earth to mass extinctions associated with rapid temperature change.  Flat areas, such as the widespread deserts of Permian Pangea, are subject to continental climate effects, but are also known to promote high degrees of sea surface temperature anomalies and amplify the effects of El Niño events.[20]  

Understanding the evolution of climate and how it relates to geology and other modulating conditions is highly important when trying to explain, explore, and predict modern climate phenomena. ENSO is not yet completely understood, and deep-time paleoclimatology gives us a unique opportunity to analyze a dataset many millions of years wider than what we can measure in the present day. With more research aimed at proxy-derived analysis of ENSO in geologic time and simulation-based analysis of its origins, we may be able to understand the extent and duration of ENSO’s effects on Earth’s weather systems over the last several hundred million years.

Objective

The objective of this review is to evaluate the hypothesis that ENSO anomalies were responsible, partially or wholly, for the conditions observed in the end Triassic and the Mesozoic anoxic events, to corroborate the predictions of past literature regarding Mesozoic ENSO anomalies with climate proxies for ENSO variation, and to identify necessary areas of further research.

    

Mountain Uplift

Mountain uplift and subsequent erosion cause a variety of changes to the manifestation of ENSO when applied in models.^{20 [21]} A general circulation model-based analysis (AOGCM) performed at several different mountain heights yielded results pertinent to the geographic conditions of the late Permian.²¹ Similarly to the estimated extreme weather conditions of the end Permian, a tropical thermal maximum was centered around the pacific dateline, with the Eastern ocean being coolest when mountains were lowered. The emergence of a pacific hot tongue in association with mountain erosion is promising for an El Niño related Permo-Triassic, as is the Eastward movement of the ocean’s colest waters as mountains uplift and the simulation diverges from conditions similar to the Permian’s flatlands and deltaic plains.[22] [23] [24] [25]

 

Figure 1:  Isopach map showing preserved Pennsylvanian strata in the Western United States. Bold black lines represent faults. Figure Soreghan et. al. 2012.

Studies of Carboniferous-Permian deposits in Western North America provide a unique set of data regarding the orogeny and patterning of the Permian’s highlands. (Fig. 1) The mountainous environments that did exist in the Permian were unusual in their emergence and uplift patterns, with the Ancestral Rockies (ARM) subsiding abruptly in the early Permian due to changing mantle flow dynamics which relaxed the forces responsible for their orogeny.[26]

 

 

Ocean Anoxia and ENSO

Acceptable oxygen levels within oceanic ecosystems are highly important for maintaining life.[27] The same is true for life-sustaining nutrients like nitrogen, which are not evenly distributed throughout the ocean.[28] El Niño and La Niña strongly affect the geometry and depth of suboxic zones in the extant pacific ocean, with ENSO responsible for 70% shifts, both positive and negative, in water column denitrification rates.[29] Denitrification is correlated with anoxia, and models of the Permo-Triassic extinction account for both an extended, SST-reducing La Niña and a significant anoxia induced extinction in the Wuchiapingian‐Changhsingian (fig. 2, fig. 3).^{25 [30]}  [31] Alternating and prolonged terrestrial droughts due to El Niño and oceanic anoxia due to La Niña would be devastating for life on earth.[32] [33]

Figure 2: Stratigraphic and geochemical log of the Niushan section, displaying changes in δ13Corg, TOC, Mo, Mo/Al, U/Al, V/Al, FeT/Al, Spy, and δ34Spy. Note the rapid but temporary drop in oxygen content in the lowest blue section, associated with the extended early-Changhsingian La Niña.  (Liao et. al. 2020)

 

 

Figure 3: Simulation-Based sea surface temperature (SST) analysis of the Changhsingian with PCO₂ levels at 2468 ppm. SST anomaly increase with PCO₂ levels. Note the extended, severe La Niña at year 5960. Pre-Industrial La Niña periods were characterized by 0.5 degree SST anomalies, where the potential Changhsingian La Niña Event (CLNA) was characterized by a multi-year, sustained SST anomaly of approximately -2 degrees. (Sun et. al. 2024)

The historical coincidence of intense La Niña events and ocean suboxia/anoxia supports the hypothesis that an increased intensity of ENSO variation surrounding the Permo-Triassic was coincident with and potentially causal to the End Permian Mass Extinction.

 

 

 

Volcanism and ENSO

Volcanoes are well known for their effects on climate conditions, frequently being associated with short-term global cooling after large eruptions.[34] [35] While a dramatic, ENSO related response is by no means guaranteed to follow a volcanic eruption, there is significant evidence that in some cases the various stresses volcanism exerts on the atmosphere and hydrosphere are contributors to change in ENSO dynamics.[36] Volcanic eruptions in the recent past have had noticeable, lasting effects on SST anomalies (fig. 5.) and produced El Niño type events within two years, but the extent of their impact is related to oceanographic dynamics.[37]

Figure 5: Observed SST response to the five main volcanic eruptions during 1870–2010 (i.e., Krakatau (1883), Santa Maria (1902), Mt Agung (1962), El Chichon (1982), and Pinatubo (1991)). SST anomalies (SSTA, oC) are computed using the preceding 5-year climatology, and the resulting anomalies are plotted relative to the tropical average (20°N–20°S). (a) Evolution of the composited Niño-3.4 (5°S–5°N, 170°W–120°W) SSTA plotted over the 2-year period including the five largest volcanic eruptions during 1870–2010 in HadISST observations (black line). The red dots denote when the five events have anomalies of the same sign. An arrow indicates the dates and magnitude of the selected eruptions, based on AOD by Gao et al. (2008). (b) Same as (a) but shown as a longitude-time section. The black rectangle denotes the Niño-3.4 region during October-November-December. Stippling highlights times and locations where the five eruptions display anomalies of the same sign and the contour corresponds to the 90% significance level of this anomaly following a two-tailed Student’s t-test. (c) Time series of anomalous percentage of El Niño occurrence for CMIP5 historical simulation members over the entire historical period (136 years). Note that the composites maintained a common seasonality (i.e., the calendar months of each eruption were aligned despite the differing eruption months) due to the seasonally synchronized nature of ENSO events (Reproduced from Khodri et al. (2017) under a creative commons attribution 4.0 license https://creativecommons.org/licenses/by/4.0/) (Dogar et. al. 2023)

There is limited research on the systematic effects of volcanism on ENSO, and so the volcano-induced El Niño model is not airtight.[38] However, there is still a precedent of eruptions producing a notable increase in factors normally associated with El Niño conditions before a prolonged cooling (La Niña) period post-eruption, and the issue of establishing a connection with ENSO lies not in linking the immediate effects but the long term ones.[39] Some of the most compelling evidence of a volcanic influence on ENSO is the reaction of the position of the Intertropical Convergence Zone to non-tropical volcanism. The ITCZ’s position is known to affect the phase transition of ENSO, and the ITCZ is shifted north and south in response to non-tropical volcanic eruptions.[40] [41] [42] [43] Volcanogenic influences on the climate, such as post-eruption winter warming, and their potential explanations remain under-researched especially in how they relate to ENSO, so it is currently difficult to concretely model this realm of volcanic influence on paleoclimatology.

 

 

ENSO Through Geological Time

Current long-term research regarding the origins and persistence of ENSO over geological time are suggestive of a persistent ENSO throughout the past 250 million years.[44] However, a similar study has not yet been conducted which includes the Permian. Identifying the points within the Mesozoic where ENSO amplitude increased dramatically and the prominent Mesozoic anoxic events yields a notable pattern, however. During the Mesozoic, three prominent anoxic events are recorded in the geologic record: The Toarcian, Aptian and Cenomanian-Turonian.[45]

            The Cenomanian-Turonian anoxic event is characterized by high amounts of buried organic matter and is thought to be linked to an increase in planktonic productivity and subsequent decomposition.[46] A similar dynamic can be observed in modern times, as extant phytoplankton populations increase as water cools after El Niño conditions, and during times of high SST anomaly, phytoplankton populations grow and shrink intraanually, a dynamic which would leave behind large amounts of organic matter to be decomposed aerobically.[47] Conditions of Cenomanian-Turonian anoxia are mirrored in cause and geology by the Aptian anoxic event, which is consistent with increased plankton productivity as well.[48] In geological formations associated with the Toarcian anoxic event, evidence of mas algal and bacterial death are present, but the distribution of fossil organisms and geochemistry of the rock indicates a heavy degree of salinity stratification.[49] In modern ocean ecosystems, the buildup of salinity-segregated strata in the pacific ocean is not only associated with, but essential for the increased ocean temperature causal to an El Niño event.[50] Jenkyns 1999 proposed a volcanological cause for the Mesozoic anoxic events, and volcanism well be a factor or even a solitary cause. This is not to say that ENSO is not involved, however, as volcanism and the behavior of the cycles involved in ENSO variation are potentially linked.  

Figure 4: Mesozoic modeling of ENSO based on Bjerkens index and atmospheric noise. Note the Increase in ENSO amplitude in the Toarcian (180 MYA), Aptian (120 MYA) and Cenomanian-Turonian (90 MYA) which correlate with major Mesozoic anoxia events. (Li 2024)

 

Was The End Permian Predisposed to El Niño/La Niña Induced Extinction?

The End Permian Mass Extinction almost certainly had a volcanic component, but the leading cause of the mass death brought about by the extinction event has been attributed to a subsequent series of environmental changes amplified by ocean acidification and a warming feedback loop.[51] El Niño and La Niña events are tightly regulated by their own impacts, as the warming of certain areas, like the Indian Ocean, during an El Niño event can initiate a cooling and transition to the subsequent La Niña event.[52] The weakening and potential reversal of these feedback loops combined with the unique geography of the Permian may have produced persistent El Niño conditions as a result of volcanic activity.²⁵ Intense volcanism is not unique across geological time, but volcanism-induced extinctions are- the end Permian is unique in the level of biodiversity loss attributed to volcanic activity, and so an additional component to the extinction event ought to be considered. ²⁵ [53] The Siberian Traps, the volcano system coincident with the Permo-Triassic Boundary, is far to the North, and would have shifted the position of the Intertropical Convergence Zone significantly upon eruption.^{47 48 49 50 [54]} The presence of intense, non-tropical volcanism in End Permian Pangea and its influence on the ITCZ, a component of ENSO, could be correlated with the intensified hydrological cycle observed in the End Permian.[55]

Bjerknes feedback may also be a component of the continuous warming loop observed at the end of the Permian. The continuous warming of sea surface waters by an El Niño event of high amplitude, potentially volcanogenic, would warm sea surface waters which then evaporate and darken clouds, reducing albedo and promoting additional warming. The redistribution of reflective clouds away from the equator would reduce overall albedo and promote continuous global warming, as is observed in End Permian Strata.^{25 [56]}

 

 

 

 

Biology of the End Permian and Subsequent Triassic Ecosystems

The persistent droughts of the End Permian promoted a shift from gymnosperm-laden forests and wetlands to lighter, transient shrubs.[57] Insect groups relying on consistent wet ecosystems rather than seasonal or interannual precipitation changes also went extinct.[58] Insects that bore aquatic larvae with terrestrial adults were relatively successful in the End Permian, indicating that there was not a permanent absence of rain, but rather an inconsistency in its behavior.⁵⁸ Both fossil record analysis and simulations indicate heavy deforestation through the End Permian, with Gondwanan forests moving to the poles and subsequent deforestation of the tropics and other areas.[59]

Faunal environments at the End Permian were under high levels of ecological stress, indicated by a drop in ichnofossil density (ichnofabric index), which is a proxy for burrowing activity.[60] Additionally, the shift from a eukaryote-dominated to prokaryote dominated plankton ecosystem is observed in the end Permian and consistent with ENSO-related climate shifts such as pacific gyre position change.[61] [62] Additional evidence for climatic ecological stress, particularly among marine communities, is the widespread delay in recovery to pre-extinction diversity. The rapid positive changes in temperature and acidity and inconsistent oxygen levels are known to have impeded the recovery of life in early Triassic biota.[63] Additionally, there is evidence of an oscillation of oxygen levels in the early Triassic as the Tethys moved from anoxic to euxinic to life-sustaining conditions before reverting back to anoxia.[64] As previously mentioned, ENSO is tied to oxygen content in aquatic biota and a high-amplitude period of ENSO in the late Permian and early Triassic would cause oscillations in ocean oxidation.[65] This is consistent with the end Permian’s inconsistent ecosystem, one which is marked by a variety of rapid changes in climate within relatively short periods of time.[66]

Discussion

The Paleozoic-Mesozoic boundary represents the greatest known loss of biodiversity in the history of the planet.[67] While hypothesized to be the result of a variety of causes, the body of knowledge available suggests that anomalies in the El Niño-Southern Oscillation (ENSO) were present and contributed to the rapid shifts in climate seen at the end of the Permian. The largely flat ecosystem of the end Permian, which saw the subsidence of the Ancestral Rockies, would have amplified the impacts of ENSO variation present at the time. ^{21 22 23 24 25 26} High levels of SST anomaly are also consistent with the end Permian’s geography as simulations of non-mountainous conditions and their impacts on ENSO produce similar oceanic hot tongues to those reconstructed for the Permian. ^{21 22 23 24 25 26}

Additional overlaps between modeled Permian ecosystems, isotope-reconstructed Permian ecosystems, and modern analyses of ENSO-affected ocean systems can be found in their changing anoxic zones. Increased SST anomaly, which is tied to ENSO, is observed to cause 70% swings in water column denitrification rates.^{27 28 29} Denitrification rates are highly correlated with anoxia, and models of Permian anoxia and SST anomaly amplitude yield low ocean oxygen and an extended La Niña during the Wuchiapingian‐Changhsingian transition, creating conditions that would be devastating to Permian ocean life, which suffered immense diversity losses at this time.^{25 30 31 32 33}

Using the data available regarding Mesozoic climate models and anoxic events, which is limited, similarities between the end Permian and mid-Mesozoic anoxic events arise. ENSO cycles have been hypothesized to exist since the early Triassic, but long-term climate simulations have not yet been performed for the Paleozoic, so a conclusive date of origin for ENSO is not known.³⁴ It is therefore not currently possible to tie pre-Mesozoic anoxic events to broad trends in ENSO amplitude. Observation of the three major Mesozoic ocean anoxic events (Toarcian, Aptian and Cenomanian-Turonian anoxic events) reveals a tentative correlation between major volcanism, ENSO amplitude, and ocean anoxia in the Mesozoic, connections which are moderately well-established in the modern day.^{44 45 46 47 48 49 50}

Volcanism has historically been proposed and somewhat widely accepted to be the cause of the End Permian Mass Extinction as well as the Mesozoic’s major anoxic events.^{45 46 47 48 49 50 [68]} Volcanism and ENSO-induced extreme climate conditions are not mutually exclusive explanations for the diversity loss seen in the Permian, particularly because in certain conditions volcanic activity is known to influence or generate El Niño and La Niña conditions.^{34 35 36 37}  There is limited analysis on long-term climate in response to extreme volcanism, but the literature which does exist demonstrates the influence of non-tropical volcanism on the position of the Intertropical Convergence Zone (ITCZ), which has a significant bearing on the nature of ENSO as well as other weather cycles.^{39 40 41 42 43 44} This is by no means definitive evidence that volcanogenic weather anomalies caused abnormal ENSO cycles that ended the Permian, but it is a compelling area for further research, as the long-term climatic effects of volcanoes are under-researched as previously mentioned.

The biology of late Permian ecosystems as well as the recovery dynamics of the early Triassic are consistent with a loss of year-round wetness in Pangea and a transition to more inconsistent weather.^{57 58 59} This, along with a sharp decrease in the ichnofabric index in Permo-Triassic strata is indicative of an ecosystem under extreme stress.⁶⁰ The same signs of extreme conditions can be seen in the oceanic ecosystems, where a pronounced shift from eukaryote-dominated plankton communities to prokaryote-dominated ones is observed. The same trend is present in modern ENSO-induced climate shifts.^{61 62} In addition to the conditions of the end Permian suggesting climate oscillation, the early Triassic’s rapid shifts in ocean oxygen content may also be representative of inconsistent year-to-year temperatures and precipitation rates.^{63 64 65 66} As are many areas of paleoclimatology, however, interannual climate variability in the early Mesozoic is poorly understood as studies mainly focus on either seasonal dynamics or longer-term climate variability.

 

Conclusion and Summary

El Niño-Southern Oscillation is a weather phenomenon which has existed for at least 252 million years. Recent literature has proposed, however, that ENSO is at least as old as the end Permian, and was a cause of the Permo-Triassic Mass Extinction, the most severe loss of biodiversity in geological history. This review was created with the aim of evaluating this claim, corroborating the predictions of past literature regarding Mesozoic ENSO anomalies with climate proxies for ENSO variation, and identifying necessary areas of further research. The main points of evidence for an ENSO-caused Permo-Triassic extinction are simulation-based, and not currently corroborated with tangible climate proxies. However, the anoxic event at the beginning of the Changhsingian is derived from the use of climate proxies and correlates with the model-derived La Niña period proposed. The same is true for simulation-derived Mesozoic SST anomaly increases and proxy-derived Mesozoic anoxic events. Volcanism has been previously attributed to these events as an explanation, but this does not necessarily contradict the hypothesis that ENSO is responsible for the changes seen. It is known that volcanic eruption impacts the behavior of interannual climate variation, but long-term volcanic effects on ENSO are under-researched. Broadly, further research ought to be done in regards to long-term Paleozoic climate variation, early Mesozoic climate variation, the effects of mountain geography on ENSO dynamics, and the impact of volcanic activity on global climate systems over the long term. Understanding these areas would allow for a much stronger comprehension of the causality of the End-Permian Mass Extinction and the three major Mesozoic anoxic events.

 

 

 

 

 

 

Works Cited

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Johansson, V., Kindvall, O., Askling, J., & Franzén, M. (2020). Extreme weather affects colonization–extinction dynamics and the persistence of a threatened butterfly. Journal of Applied Ecology, 57(6), 1068-1077.

Thomas, C. D., Franco, A. M., & Hill, J. K. (2006). Range retractions and extinction in the face of climate warming. Trends in Ecology & Evolution, 21(8), 415-416.

Alan Pounds, J., Bustamante, M., Coloma, L. et al. Widespread amphibian extinctions from epidemic disease driven by global warming. Nature 439, 161–167 (2006). https://doi.org/10.1038/nature04246

Harrison, R. D. (2000). Repercussions of El Nino: drought causes extinction and the breakdown of mutualism in Borneo. Proceedings of the Royal Society of London. Series B: Biological Sciences, 267(1446), 911-915.

Enfield, D. B. (1989). El Niño, past and present. Reviews of geophysics, 27(1), 159-187.

Dahlin, K. M., & Ault, T. R. (2018). Global linkages between teleconnection patterns and the terrestrial biosphere. International journal of applied earth observation and geoinformation, 69, 56-63.

Hoskins, B. J., & Karoly, D. J. (1981). The steady linear response of a spherical atmosphere to thermal and orographic forcing. Journal of Atmospheric Sciences, 38(6), 1179-1196.

Bjerknes, J. (1969). Atmospheric teleconnections from the equatorial Pacific. Monthly weather review, 97(3), 163-172.

Rial, J. A., Pielke, R. A., Beniston, M., Claussen, M., Canadell, J., Cox, P., ... & Salas, J. D. (2004). Nonlinearities, feedbacks and critical thresholds within the Earth's climate system. Climatic change, 65, 11-38

Kidder, D. L., & Worsley, T. R. (2004). Causes and consequences of extreme Permo-Triassic warming to globally equable climate and relation to the Permo-Triassic extinction and recovery. Palaeogeography, Palaeoclimatology, Palaeoecology, 203(3-4), 207-237.

Dorado, G., Rey, I., Rosales, T. E., Sánchez-Cañete, F. J. S., Luque, F., Jiménez, I., ... & Vásquez, V. F. (2010). Biological mass extinctions on planet Earth. Archaeobios, 4, 53-64.

Schove, D. J., Nairn, A. E. M., & Opdyke, N. D. (1958). The climatic geography of the Permian. Geografiska Annaler, 40(3-4), 216-231.

Cúneo, N. R. (1996). Permian phytogeography in Gondwana. Palaeogeography, Palaeoclimatology, Palaeoecology, 125(1–4), 75–104. https://doi.org/10.1016/S0031-0182(96)00025-9

Robock, A. (2000). Volcanic eruptions and climate. Reviews of geophysics, 38(2), 191-219.

Kammerer, C. F., Viglietti, P. A., Butler, E., & Botha, J. (2023). Rapid turnover of top predators in African terrestrial faunas around the Permian-Triassic mass extinction. Current Biology, 33(11), 2283-2290.

Poulsen, C. J., Gendaszek, A. S., & Jacob, R. L. (2003). Did the rifting of the Atlantic Ocean cause the Cretaceous thermal maximum?. Geology, 31(2), 115-118.

Pol, D., Ramezani, J., Gomez, K., Carballido, J. L., Carabajal, A. P., Rauhut, O. W. M., ... & Cúneo, N. R. (2020). Extinction of herbivorous dinosaurs linked to Early Jurassic global warming event. Proceedings of the Royal Society B, 287(1939), 20202310.

Twitchett, R. J. (2006). The palaeoclimatology, palaeoecology and palaeoenvironmental analysis of mass extinction events. Palaeogeography, Palaeoclimatology, Palaeoecology, 232(2-4), 190-213.

Kitoh, A. (2007). ENSO modulation by mountain uplift. Climate dynamics, 28, 781-796.

Lee, J. Y., Wang, B., Seo, K. H., Ha, K. J., Kitoh, A., & Liu, J. (2015). Effects of mountain uplift on global monsoon precipitation. Asia-Pacific Journal of Atmospheric Sciences, 51, 275-290.

Ward, R. F., Kendall, C. G. S. C., & Harris, P. M. (1986). Upper Permian (Guadalupian) facies and their association with hydrocarbons—Permian basin, west Texas and New Mexico. AAPG bulletin, 70(3), 239-262.

Minter, N. J., Buatois, L. A., Lucas, S. G., Braddy, S. J., & Smith, J. A. (2006). Spiral-shaped graphoglyptids from an Early Permian intertidal flat. Geology, 34(12), 1057-1060.

Faure, M., Lardeaux, J. M., & Ledru, P. (2009). A review of the pre-Permian geology of the Variscan French Massif Central. Comptes rendus géoscience, 341(2-3), 202-213.

Sun, Y., Farnsworth, A., Joachimski, M. M., Wignall, P. B., Krystyn, L., Bond, D. P., ... & Valdes, P. J. (2024). Mega El Niño instigated the end-Permian mass extinction. Science, 385(6714), 1189-1195.

Soreghan, G. S., Keller, G. R., Gilbert, M. C., Chase, C. G., & Sweet, D. E. (2012). Load-induced subsidence of the Ancestral Rocky Mountains recorded by preservation of Permian landscapes. Geosphere, 8(3), 654-668.

Davis, J. C. (1975). Minimal dissolved oxygen requirements of aquatic life with emphasis on Canadian species: a review. Journal of the Fisheries Board of Canada, 32(12), 2295-2332.

Letscher, R. T., Hansell, D. A., Carlson, C. A., Lumpkin, R., & Knapp, A. N. (2013). Dissolved organic nitrogen in the global surface ocean: Distribution and fate. Global Biogeochemical Cycles, 27(1), 141-153.

Yang, S., Gruber, N., Long, M. C., & Vogt, M. (2017). ENSO‐driven variability of denitrification and suboxia in the Eastern Tropical Pacific Ocean. Global Biogeochemical Cycles, 31(10), 1470-1487.

Wei, H., Tang, W., Gu, H., Fu, X., & Zhang, X. (2021). Chemostratigraphy and pyrite morphology across the Wuchiapingian‐Changhsingian boundary in the Middle Yangtze Platform, South China. Geological Journal, 56(12), 6102-6116.

Wei, H., Tang, W., Gu, H., Fu, X., & Zhang, X. (2021). Chemostratigraphy and pyrite morphology across the Wuchiapingian‐Changhsingian boundary in the Middle Yangtze Platform, South China. Geological Journal, 56(12), 6102-6116.

Schimel, J. P. (2018). Life in dry soils: effects of drought on soil microbial communities and processes. Annual review of ecology, evolution, and systematics, 49(1), 409-432.

May, D. R. (1972). The effects of oxygen concentration and anoxia on respiration of Abarenicola pacifica and Lumbrineris zonata (Polychaeta). The Biological Bulletin, 142(1), 71-83.

Chylek, P., Folland, C., Klett, J. D., & Dubey, M. K. (2020). CMIP5 climate models overestimate cooling by volcanic aerosols. Geophysical Research Letters, 47(3), e2020GL087047.

Kravitz, B., & Robock, A. (2011). Climate effects of high‐latitude volcanic eruptions: Role of the time of year. Journal of Geophysical Research: Atmospheres, 116(D1).

Clement, A. C., Seager, R., Cane, M. A., & Zebiak, S. E. (1996). An ocean dynamical thermostat. Journal of Climate, 9(9), 2190-2196.

Predybaylo, E., Stenchikov, G., Wittenberg, A. T., & Osipov, S. (2020). El Niño/Southern Oscillation response to low-latitude volcanic eruptions depends on ocean pre-conditions and eruption timing. Communications Earth & Environment, 1(1), 12.

Dogar, M. M., Hermanson, L., Scaife, A. A., Visioni, D., Zhao, M., Hoteit, I., ... & Fujiwara, M. (2023). A review of El Niño Southern Oscillation linkage to strong volcanic eruptions and post-volcanic winter warming. Earth Systems and Environment, 7(1), 15-42.

McGregor, S., Khodri, M., Maher, N., Ohba, M., Pausata, F. S., & Stevenson, S. (2020). The effect of strong volcanic eruptions on ENSO. El Niño Southern Oscillation in a changing climate, 267-287.

Ham, Y. G., & Kug, J. S. (2014). Effects of Pacific Intertropical Convergence Zone precipitation bias on ENSO phase transition. Environmental Research Letters, 9(6), 064008.

Liao, H., Cai, Z., Guo, J., & Song, Z. (2023). Effects of ITCZ Poleward Location Bias on ENSO Seasonal Phase-Locking Simulation in Climate Models. Journal of Climate, 36(15), 5233-5249.

Dogar, M. M., Stenchikov, G., Osipov, S., Wyman, B., & Zhao, M. (2017). Sensitivity of the regional climate in the Middle East and North Africa to volcanic perturbations. Journal of Geophysical Research: Atmospheres, 122(15), 7922-7948.

Dogar, M. M., Kucharski, F., & Azharuddin, S. (2017). Study of the global and regional climatic impacts of ENSO magnitude using SPEEDY AGCM. Journal of Earth System Science, 126(2), 30.

Li, X., Hu, S., Hu, Y., Cai, W., Jin, Y., Lu, Z., ... & Nie, J. (2024). Persistently active El Niño–Southern Oscillation since the Mesozoic. Proceedings of the National Academy of Sciences, 121(45), e2404758121.

Jenkyns, H. C. (1999). Mesozoic anoxic events and palaeoclimate. Zentralblatt für Geologie und Paläontologie, 1997(7-9), 943-949.

Lavaniegos, B. E., Jiménez-Pérez, L. C., & Gaxiola-Castro, G. (2002). Plankton response to El Niño 1997–1998 and La Niña 1999 in the southern region of the California Current. Progress in Oceanography, 54(1-4), 33-58.

Sliter, W. V. (1989). Aptian anoxia in the Pacific Basin. Geology, 17(10), 909-912.

Farrimond, P., Eglinton, G., Brassell, S. C., & Jenkyns, H. C. (1989). Toarcian anoxic event in Europe: an organic geochemical study. Marine and Petroleum Geology, 6(2), 136-147.

Maes, C., Picaut, J., & Belamari, S. (2005). Importance of the salinity barrier layer for the buildup of El Niño. Journal of Climate, 18(1), 104-118.

Benton, M. J., & Twitchett, R. J. (2003). How to kill (almost) all life: the end-Permian extinction event. Trends in Ecology & Evolution, 18(7), 358-365.

Kug, J. S., & Kang, I. S. (2006). Interactive feedback between ENSO and the Indian Ocean. Journal of climate, 19(9), 1784-1801.

Fan, J. X., Shen, S. Z., Erwin, D. H., Sadler, P. M., MacLeod, N., Cheng, Q. M., ... & Zhao, Y. Y. (2020). A high-resolution summary of Cambrian to Early Triassic marine invertebrate biodiversity. Science, 367(6475), 272-277.

Saunders, A., & Reichow, M. (2009). The Siberian Traps and the End-Permian mass extinction: a critical review. Chinese Science Bulletin, 54(1), 20-37.

Schobben, M., Joachimski, M. M., Korn, D., Leda, L., & Korte, C. (2014). Palaeotethys seawater temperature rise and an intensified hydrological cycle following the end-Permian mass extinction. Gondwana Research, 26(2), 675-683.

Vecchi, G. A., & Wittenberg, A. T. (2010). El Niño and our future climate: where do we stand?. Wiley Interdisciplinary Reviews: Climate Change, 1(2), 260-270.

Greb, S. F., DiMichele, W. A., & Gastaldo, R. A. (2006). Evolution and importance of wetlands in earth history.

Jouault, C., Nel, A., Perrichot, V., Legendre, F., & Condamine, F. L. (2022). Multiple drivers and lineage-specific insect extinctions during the Permo–Triassic. Nature Communications, 13(1), 7512.

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[1] Maxwell, S. L., Butt, N., Maron, M., McAlpine, C. A., Chapman, S., Ullmann, A., ... & Watson, J. E. (2019). Conservation implications of ecological responses to extreme weather and climate events. Diversity and Distributions, 25(4), 613-625.

[2] Johansson, V., Kindvall, O., Askling, J., & Franzén, M. (2020). Extreme weather affects colonization–extinction dynamics and the persistence of a threatened butterfly. Journal of Applied Ecology, 57(6), 1068-1077.

[3] Thomas, C. D., Franco, A. M., & Hill, J. K. (2006). Range retractions and extinction in the face of climate warming. Trends in Ecology & Evolution, 21(8), 415-416.

[4] Alan Pounds, J., Bustamante, M., Coloma, L. et al. Widespread amphibian extinctions from epidemic disease driven by global warming. Nature 439, 161–167 (2006). https://doi.org/10.1038/nature04246

[5] Harrison, R. D. (2000). Repercussions of El Nino: drought causes extinction and the breakdown of mutualism in Borneo. Proceedings of the Royal Society of London. Series B: Biological Sciences, 267(1446), 911-915.

[6] Enfield, D. B. (1989). El Niño, past and present. Reviews of geophysics, 27(1), 159-187.

[7] Dahlin, K. M., & Ault, T. R. (2018). Global linkages between teleconnection patterns and the terrestrial biosphere. International journal of applied earth observation and geoinformation, 69, 56-63.

[8] Hoskins and Karoly, 1981

[9] Bjerknes 1969

[10] Rial, J. A., Pielke, R. A., Beniston, M., Claussen, M., Canadell, J., Cox, P., ... & Salas, J. D. (2004). Nonlinearities, feedbacks and critical thresholds within the Earth's climate system. Climatic change, 65, 11-38

[11] Kidder, D. L., & Worsley, T. R. (2004). Causes and consequences of extreme Permo-Triassic warming to globally equable climate and relation to the Permo-Triassic extinction and recovery. Palaeogeography, Palaeoclimatology, Palaeoecology, 203(3-4), 207-237.

[12] Dorado, G., Rey, I., Rosales, T. E., Sánchez-Cañete, F. J. S., Luque, F., Jiménez, I., ... & Vásquez, V. F. (2010). Biological mass extinctions on planet Earth. Archaeobios, 4, 53-64.

[13] Schove, D. J., Nairn, A. E. M., & Opdyke, N. D. (1958). The climatic geography of the Permian. Geografiska Annaler, 40(3-4), 216-231.

[14] Cúneo, N. R. (1996). Permian phytogeography in Gondwana. Palaeogeography, Palaeoclimatology, Palaeoecology, 125(1–4), 75–104. https://doi.org/10.1016/S0031-0182(96)00025-9

[15] Robock, A. (2000). Volcanic eruptions and climate. Reviews of geophysics, 38(2), 191-219.

[16] Kammerer, C. F., Viglietti, P. A., Butler, E., & Botha, J. (2023). Rapid turnover of top predators in African terrestrial faunas around the Permian-Triassic mass extinction. Current Biology, 33(11), 2283-2290.

[17] Poulsen, C. J., Gendaszek, A. S., & Jacob, R. L. (2003). Did the rifting of the Atlantic Ocean cause the Cretaceous thermal maximum?. Geology, 31(2), 115-118.

[18] Pol, D., Ramezani, J., Gomez, K., Carballido, J. L., Carabajal, A. P., Rauhut, O. W. M., ... & Cúneo, N. R. (2020). Extinction of herbivorous dinosaurs linked to Early Jurassic global warming event. Proceedings of the Royal Society B, 287(1939), 20202310.

[19] Twitchett, R. J. (2006). The palaeoclimatology, palaeoecology and palaeoenvironmental analysis of mass extinction events. Palaeogeography, Palaeoclimatology, Palaeoecology, 232(2-4), 190-213.

[20] Kitoh, A. (2007). ENSO modulation by mountain uplift. Climate dynamics, 28, 781-796.

[21] Lee, J. Y., Wang, B., Seo, K. H., Ha, K. J., Kitoh, A., & Liu, J. (2015). Effects of mountain uplift on global monsoon precipitation. Asia-Pacific Journal of Atmospheric Sciences, 51, 275-290.

[22] Ward, R. F., Kendall, C. G. S. C., & Harris, P. M. (1986). Upper Permian (Guadalupian) facies and their association with hydrocarbons—Permian basin, west Texas and New Mexico. AAPG bulletin, 70(3), 239-262.

[23] Minter, N. J., Buatois, L. A., Lucas, S. G., Braddy, S. J., & Smith, J. A. (2006). Spiral-shaped graphoglyptids from an Early Permian intertidal flat. Geology, 34(12), 1057-1060.

[24] Faure, M., Lardeaux, J. M., & Ledru, P. (2009). A review of the pre-Permian geology of the Variscan French Massif Central. Comptes rendus géoscience, 341(2-3), 202-213.

[25] Sun, Y., Farnsworth, A., Joachimski, M. M., Wignall, P. B., Krystyn, L., Bond, D. P., ... & Valdes, P. J. (2024). Mega El Niño instigated the end-Permian mass extinction. Science, 385(6714), 1189-1195.

[26] Soreghan, G. S., Keller, G. R., Gilbert, M. C., Chase, C. G., & Sweet, D. E. (2012). Load-induced subsidence of the Ancestral Rocky Mountains recorded by preservation of Permian landscapes. Geosphere, 8(3), 654-668.

[27] Davis, J. C. (1975). Minimal dissolved oxygen requirements of aquatic life with emphasis on Canadian species: a review. Journal of the Fisheries Board of Canada, 32(12), 2295-2332.

[28] Letscher, R. T., Hansell, D. A., Carlson, C. A., Lumpkin, R., & Knapp, A. N. (2013). Dissolved organic nitrogen in the global surface ocean: Distribution and fate. Global Biogeochemical Cycles, 27(1), 141-153.

[29] Yang, S., Gruber, N., Long, M. C., & Vogt, M. (2017). ENSO‐driven variability of denitrification and suboxia in the Eastern Tropical Pacific Ocean. Global Biogeochemical Cycles, 31(10), 1470-1487.

[30] Wei, H., Tang, W., Gu, H., Fu, X., & Zhang, X. (2021). Chemostratigraphy and pyrite morphology across the Wuchiapingian‐Changhsingian boundary in the Middle Yangtze Platform, South China. Geological Journal, 56(12), 6102-6116.

[31] Liao, Z., Hu, W., Cao, J., Wang, X., & Fu, X. (2020). Oceanic anoxia through the late Permian Changhsingian Stage in the Lower Yangtze region, South China: Evidence from sulfur isotopes and trace elements. Chemical Geology, 532, 119371.

[32] Schimel, J. P. (2018). Life in dry soils: effects of drought on soil microbial communities and processes. Annual review of ecology, evolution, and systematics, 49(1), 409-432.

[33] May, D. R. (1972). The effects of oxygen concentration and anoxia on respiration of Abarenicola pacifica and Lumbrineris zonata (Polychaeta). The Biological Bulletin, 142(1), 71-83.

[34] Chylek, P., Folland, C., Klett, J. D., & Dubey, M. K. (2020). CMIP5 climate models overestimate cooling by volcanic aerosols. Geophysical Research Letters, 47(3), e2020GL087047.

[35] Kravitz, B., & Robock, A. (2011). Climate effects of high‐latitude volcanic eruptions: Role of the time of year. Journal of Geophysical Research: Atmospheres, 116(D1).

[36] Clement, A. C., Seager, R., Cane, M. A., & Zebiak, S. E. (1996). An ocean dynamical thermostat. Journal of Climate, 9(9), 2190-2196.

[37] Predybaylo, E., Stenchikov, G., Wittenberg, A. T., & Osipov, S. (2020). El Niño/Southern Oscillation response to low-latitude volcanic eruptions depends on ocean pre-conditions and eruption timing. Communications Earth & Environment, 1(1), 12.

[38] Dogar, M. M., Hermanson, L., Scaife, A. A., Visioni, D., Zhao, M., Hoteit, I., ... & Fujiwara, M. (2023). A review of El Niño Southern Oscillation linkage to strong volcanic eruptions and post-volcanic winter warming. Earth Systems and Environment, 7(1), 15-42.

[39] McGregor, S., Khodri, M., Maher, N., Ohba, M., Pausata, F. S., & Stevenson, S. (2020). The effect of strong volcanic eruptions on ENSO. El Niño Southern Oscillation in a changing climate, 267-287.

[40] Ham, Y. G., & Kug, J. S. (2014). Effects of Pacific Intertropical Convergence Zone precipitation bias on ENSO phase transition. Environmental Research Letters, 9(6), 064008.

[41] Liao, H., Cai, Z., Guo, J., & Song, Z. (2023). Effects of ITCZ Poleward Location Bias on ENSO Seasonal Phase-Locking Simulation in Climate Models. Journal of Climate, 36(15), 5233-5249.

[42] Dogar, M. M., Stenchikov, G., Osipov, S., Wyman, B., & Zhao, M. (2017). Sensitivity of the regional climate in the Middle East and North Africa to volcanic perturbations. Journal of Geophysical Research: Atmospheres, 122(15), 7922-7948.

[43] Dogar, M. M., Kucharski, F., & Azharuddin, S. (2017). Study of the global and regional climatic impacts of ENSO magnitude using SPEEDY AGCM. Journal of Earth System Science, 126(2), 30.

[44] Li, X., Hu, S., Hu, Y., Cai, W., Jin, Y., Lu, Z., ... & Nie, J. (2024). Persistently active El Niño–Southern Oscillation since the Mesozoic. Proceedings of the National Academy of Sciences, 121(45), e2404758121.

[45] Jenkyns, H. C. (1999). Mesozoic anoxic events and palaeoclimate. Zentralblatt für Geologie und Paläontologie, 1997(7-9), 943-949.

[46] Jenkyns, H. C. (1980). Cretaceous anoxic events: from continents to oceans. Journal of the Geological Society, 137(2), 171-188.

[47] Lavaniegos, B. E., Jiménez-Pérez, L. C., & Gaxiola-Castro, G. (2002). Plankton response to El Niño 1997–1998 and La Niña 1999 in the southern region of the California Current. Progress in Oceanography, 54(1-4), 33-58.

[48] Sliter, W. V. (1989). Aptian anoxia in the Pacific Basin. Geology, 17(10), 909-912.

[49] Farrimond, P., Eglinton, G., Brassell, S. C., & Jenkyns, H. C. (1989). Toarcian anoxic event in Europe: an organic geochemical study. Marine and Petroleum Geology, 6(2), 136-147.

[50] Maes, C., Picaut, J., & Belamari, S. (2005). Importance of the salinity barrier layer for the buildup of El Niño. Journal of Climate, 18(1), 104-118.

[51] Benton, M. J., & Twitchett, R. J. (2003). How to kill (almost) all life: the end-Permian extinction event. Trends in Ecology & Evolution, 18(7), 358-365.

[52] Kug, J. S., & Kang, I. S. (2006). Interactive feedback between ENSO and the Indian Ocean. Journal of climate, 19(9), 1784-1801.

[53] Fan, J. X., Shen, S. Z., Erwin, D. H., Sadler, P. M., MacLeod, N., Cheng, Q. M., ... & Zhao, Y. Y. (2020). A high-resolution summary of Cambrian to Early Triassic marine invertebrate biodiversity. Science, 367(6475), 272-277.

[54] Saunders, A., & Reichow, M. (2009). The Siberian Traps and the End-Permian mass extinction: a critical review. Chinese Science Bulletin, 54(1), 20-37.

[55] Schobben, M., Joachimski, M. M., Korn, D., Leda, L., & Korte, C. (2014). Palaeotethys seawater temperature rise and an intensified hydrological cycle following the end-Permian mass extinction. Gondwana Research, 26(2), 675-683.

[56] Vecchi, G. A., & Wittenberg, A. T. (2010). El Niño and our future climate: where do we stand?. Wiley Interdisciplinary Reviews: Climate Change, 1(2), 260-270.

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