Tag: Late Paleozoic Ice Age

When Oxygen Soared and Rainforests Crashed: Extreme Climate, Giant Species, and the Dramatic Impacts of the Carboniferous Period (359–299 Million Years Ago)

Many species thrived in the Carboniferous Period (≈359- 299 million years ago) under elevated atmospheric oxygen levels, estimated at roughly 25- 35% (versus ~21% today).

The Carboniferous Period (≈359- 299 million years ago) featured one of Earth’s most extreme and dynamic climate regimes: a prolonged icehouse (the Late Paleozoic Ice Age, or LPIA) with repeated glacial- interglacial cycles, very low atmospheric CO₂, rising O₂, extensive tropical coal forests, and progressive aridification toward the Permian.

Illustration depicting the Carboniferous Period, showcasing a lush rainforest scene with tall trees, ferns, and a large prehistoric insect flying overhead. A large, segmented creature resembling an ancient arthropod is present on the forest floor, while a mountainous backdrop indicates a transition in climate and environment.
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A 2026 Nature study challenges the long- standing idea that high atmospheric oxygen alone enabled giant insects like Meganeura (and related griffinflies/Meganisoptera) to reach enormous sizes, showing that oxygen diffusion limits via tracheoles were likely not the main constraint.

About 300 million years ago, during the late Carboniferous (and into the early Permian), Earth hosted flying insects far larger than any alive today. Meganeura monyi and the even larger Meganeuropsis permiana had wingspans of roughly 65- 75 cm (about 70 cm is commonly cited), with body mass estimates for the biggest forms ranging from tens of grams up to 100- 150 g in some engineering analyses.

They resembled oversized dragonflies but belonged to an extinct order (Meganisoptera/griffinflies), acted as aerial predators, and lived in swampy, forested environments. Other arthropods of the era, such as the millipede- like Arthropleura (up to ~2.5 m), were also gigantic.

Insects breathe through a network of tubes (tracheae) that branch into tiny tracheoles delivering oxygen directly to tissues by diffusion, no lungs or blood- based oxygen transport like vertebrates.

For decades, scientists linked Palaeozoic insect gigantism to higher atmospheric oxygen (estimates often ~30- 35% versus ~21% today), which would have eased diffusion limits and allowed larger body sizes. The later drop in oxygen was thought to explain why such giants vanished. Supporting observations included some modern insects growing larger in oxygen-enriched air and allometric patterns in tracheal investment.

The fossil record itself is more complex than a simple oxygen- size correlation: maximum insect sizes tracked oxygen somewhat for long periods but decoupled later, and giant forms persisted into times of lower oxygen. The full picture remains incomplete; researchers emphasize multifactorial causes.

In short, Meganeura and its relatives show that the largest insects in Earth’s history were shaped by more than oxygen levels alone. The new work undermines a popular textbook explanation while leaving the precise drivers of their rise and fall as an open scientific question.

Graph showing the relationship between atmospheric oxygen content and the evolution of flight in insects, pterosaurs, avians, and chiropterans over geological time. Features illustrations of a large insect and a smaller insect for scale.
A graph showing changes in Earth’s atmospheric oxygen levels over the past 550 million years. The blue curve tracks oxygen concentration through different geological periods, from the Cambrian to the present day. Credit: Nature

Many species thrived in the Carboniferous Period (≈359- 299 million years ago) under elevated atmospheric oxygen levels, estimated at roughly 25- 35% (versus ~21% today).

This hyperoxic atmosphere is widely linked to the growth of unusually large arthropods (via their tracheal respiratory systems) and supported diverse terrestrial ecosystems in the vast coal forests and wetlands, though recent studies (including the 2026 Nature work on tracheoles) indicate oxygen was not the sole factor enabling gigantism.

These are the classic examples of Carboniferous gigantism:

Griffinflies (order Meganisoptera/Protodonata): Meganeura monyi (wingspan ~65- 75 cm) and the related Meganeuropsis permiana (up to ~71 cm wingspan). These dragonfly- like aerial predators were among the largest flying insects ever. Other large Paleodictyoptera and mayfly- like insects also reached substantial sizes (wingspans up to ~45 cm in some cases).

Arthropleura (especially Arthropleura armata and related forms): The largest- known land arthropod, a millipede- like myriapod reaching 2- 2.7+ meters in length and weighing up to ~50 kg. It was a detritivore or herbivore that roamed forests and open woodlands.

Giant scorpions: Pulmonoscorpius kirktonensis (up to ~70 cm long), one of the largest terrestrial scorpions known, from early Carboniferous deposits in Scotland. It was likely an active predator.

Other large arthropods included various cockroaches (blattopterans), spiders, and additional myriapods and arachnids that reached sizes uncommon today.

Early tetrapods (amphibian-grade and the first amniotes) also lived under these conditions and sometimes attained large sizes:

  • Temnospondyl and other labyrinthodont amphibians (e.g., forms related to Eryops later, or various Carboniferous genera), some reached lengths of 1- 2 and more meters and were dominant predators in wetlands.
  • Early amniotes (stem reptiles and synapsids), such as Hylonomus (one of the earliest known reptiles) and other small- to- medium forms that began diversifying toward the end of the period. These were better adapted to drier conditions after events like the Carboniferous Rainforest Collapse.

Countless smaller insects, myriapods, arachnids, early tetrapods, fish (including sharks like Cladoselache), and of course the dominant plants (giant lycopsids such as Lepidodendron, sphenopsids, ferns, and seed ferns) also inhabited this high- O₂ world.

The combination of high oxygen, dense vegetation, humid wetlands, and the absence of large aerial vertebrate predators (birds and pterosaurs evolved much later) created ecological opportunities for arthropod gigantism.

Note that not all Carboniferous species were giants, most insects and other animals were of more ordinary sizes, and some large forms persisted into the Permian even as oxygen levels fluctuated.

The high- O₂ environment is one key part of the story of Carboniferous life, alongside climate, habitat structure, and evolutionary opportunity.

A prehistoric landscape featuring a river with various ancient aquatic creatures, including a shark and other fish. On the shore, a millipede and a turtle, along with ferns and tall trees in a misty environment.
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The Carboniferous Period (≈359- 299 million years ago) featured one of Earth’s most extreme and dynamic climate regimes: a prolonged icehouse (the Late Paleozoic Ice Age, or LPIA) with repeated glacial- interglacial cycles, very low atmospheric CO₂, rising O₂, extensive tropical coal forests, and progressive aridification toward the Permian.

This interval spans the Mississippian (Early Carboniferous) and Pennsylvanian (Late Carboniferous) and is critical for understanding icehouse dynamics, carbon- cycle feedback involving early forests, and the conditions that supported giant insects such as Meganeura.

Atmospheric Composition

CO₂: Dropped sharply from higher Devonian levels. During much of the LPIA, values were often in the range of ~200- 400 ppm (sometimes as low as ~150- 200 ppm or lower in models and proxies), among the lowest of the Phanerozoic. High- resolution records show orbital- scale (eccentricity) fluctuations of hundreds of ppm. A rapid ~4- fold rise around 294 Ma (Early Permian) helped end the main phase of the ice age.

O₂: Rose substantially due to massive organic- carbon burial in coal swamps (incomplete decomposition under waterlogged, anoxic conditions). Estimates commonly reach ~25- 35% by the late Carboniferous/early Permian (versus ~21% today). This high- O₂ atmosphere is linked to the earlier discussion of giant insects, though the 2026 study indicates it was not the sole size constraint.

Low CO₂ reduced the greenhouse effect, while high O₂ and widespread vegetation burial reinforced cooling. Modeling shows that CO₂ levels near the lower end approached thresholds that could have risked more extreme (near- Snowball) glaciation, though orbital variations and other factors prevented it.

The Late Paleozoic Ice Age (LPIA)

The LPIA is the longest- lived and one of the most intense icehouses of the Phanerozoic (roughly Late Devonian to mid/late Permian, with its Carboniferous peak).

  • Glaciation intensified from the late Visean/Serpukhovian onward, with multiple discrete glacial episodes separated by interglacials.
  • Ice centers were concentrated on southern Gondwana (South America, Africa, Antarctica, Australia, India), expanding and contracting; maximum extent occurred near the Carboniferous- Permian boundary.
  • Sea- level fluctuations of tens to ~100 m produced widespread cyclothems (repeating sequences of marine, terrestrial, and coal deposits) driven by glacioeustasy, paced by orbital cycles (especially 405- kyr eccentricity and longer obliquity modulations).
  • Global average temperatures during glacial maxima were cooler than today in many reconstructions (tropics still relatively warm but with strong gradients; polar regions very cold).

The main icehouse phase was maintained by sustained low CO₂. Deglaciation accelerated in the Early Permian with the CO₂ rise, leading to warmer, drier conditions overall.

Tropical Forests, Coal, and Climate Feedback

Equatorial regions (Laurussia/Euramerica) hosted vast wetland “coal forests” dominated by lycopsids (giant clubmosses such as Lepidodendron), sphenopsids (horsetails), ferns, and early seed plants. These created the bulk of the world’s coal deposits through rapid peat accumulation.

Vegetation was highly dynamic:

  • Repeated turnovers between wetland (humid, glacial-linked) and dryland (more seasonal or arid) biomes on glacial- interglacial timescales.
  • The Carboniferous Rainforest Collapse (around the late Moscovian/Kasimovian, ~305- 307 Ma) involved contraction of the lycopsid- dominated wetlands, linked to cooling, drying, sea- level fall, and habitat fragmentation. This reduced a major carbon sink and contributed to later CO₂ changes.

Plant physiology (stomatal conductance, water use) and ecosystem shifts influenced local hydrology, runoff, and the broader carbon cycle, creating feedbacks with climate.

Broader Dynamics and Drivers

Paleogeography: Assembly of Pangaea increased continentality, altered ocean circulation, and contributed to progressive tropical aridification (especially across the Carboniferous- Permian transition). Mountain building (e.g., Central Pangaean Mountains) affected regional rainfall and weathering.

Orbital forcing: Strong eccentricity and obliquity signals drove the high- frequency glacial- interglacial cycles and associated sea- level, vegetation, and CO₂ variations.

Long- term trend: Overall cooling into the LPIA apex, followed by aridification and warming into the Permian. Equatorial Pangaea shifted from persistently humid wetlands toward more seasonal and eventually semi- arid/arid conditions.

These dynamics created a world of high oxygen, expansive wetlands (favoring large arthropods), fluctuating sea levels, and strong latitudinal climate gradients, very different from both the preceding Devonian greenhouse and the subsequent Permian. The Carboniferous remains a key analog for understanding icehouse carbon- cycle– climate interactions on a vegetated Earth.

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Carboniferous climate (≈359- 299 Ma) was defined by the Late Paleozoic Ice Age (LPIA), a prolonged icehouse with repeated glacial- interglacial cycles, low atmospheric CO₂ (often 200- 400 ppm or lower), rising O₂ (peaking ~25–35%), humid equatorial wetlands, and progressive tropical aridification.

These conditions produced cascading impacts across the atmosphere, biosphere, geology, and long- term Earth systems.

Widespread tropical forests (especially lycopsid-dominated coal swamps) drove massive organic- carbon burial.

This drew down CO₂, reinforcing global cooling and sustaining the LPIA, while elevating O₂ through photosynthesis and incomplete decay under waterlogged conditions. High burial rates brought CO₂ close to thresholds that risked more extreme (near- Snowball Earth) glaciation, though orbital variations and other factors prevented total freeze- over.

The high- O₂ atmosphere promoted more frequent and intense wildfires (evident in abundant charcoal), altering vegetation structure and nutrient cycling. Plant physiology was also affected: elevated O₂ relative to CO₂ increased photorespiration in C3 plants, potentially reducing net primary productivity in some models, while still supporting vast biomass overall.

Vegetation and forests: Oscillating glacial- interglacial climates repeatedly restructured tropical forests between everwet swamp biomes (glacial phases) and more seasonal/dryland communities (interglacials). This culminated in the Carboniferous Rainforest Collapse (~305 Ma), which fragmented and largely eliminated the classic lycopsid coal forests in Euramerica, shifting dominance to tree ferns and more drought-tolerant groups. Habitat loss reduced a major carbon sink and contributed to later aridification.

Arthropods: High oxygen relaxed respiratory constraints for tracheal breathers, facilitating gigantism in forms such as the griffinfly Meganeura (wingspans ~70 cm), the millipede- like Arthropleura (up to 2.5 and more meters), and large scorpions like Pulmonoscorpius. Dense vegetation and limited large vertebrate competitors further supported this. Flight evolved and diversified rapidly among insects.

Tetrapods: Wetland habitats favored amphibian- grade forms, but climate shifts (especially aridification and the rainforest collapse) drove extinctions among moisture- dependent amphibians while favoring the radiation of amniotes (early reptiles and synapsids) with adaptations for drier conditions (e.g., amniotic eggs). Habitat fragmentation promoted endemism, new ecological strategies (herbivory, predation), and broader terrestrial expansion.

Marine life experienced sea- level fluctuations (cyclothems from glacioeustasy of tens to ~100 m), anoxia in some intervals, and biodiversity responses tied to cooling versus warming pulses.

Glacial cycles produced widespread cyclothems, repeating sedimentary sequences of marine limestones, shales, sandstones, and coals, that dominate Carboniferous strata in many regions.

Sea- level falls exposed vast lowlands for peat accumulation, later becoming the bulk of the world’s economic coal deposits (the source of much of the fossil carbon driving modern industrial CO₂ emissions).

Mountain building associated with Pangaea assembly created rain shadows and altered drainage, contributing to regional drying. Polar ice sheets on Gondwana left glacial deposits (tillites, striations) across southern continents.

The Carboniferous set the stage for the early Permian transition to warmer, drier conditions as CO₂ eventually rose and ice sheets waned.

The period’s icehouse dynamics, vegetation-climate feedback, and atmospheric extremes provide key analogs for understanding modern icehouse- greenhouse transitions, the role of forests as carbon sinks, and how climate stress drives evolutionary and ecosystem restructuring.

In short, Carboniferous climate not only shaped a unique world of giant arthropods and coal forests but left a lasting imprint on Earth’s carbon cycle and biological trajectory.

210- Million- Year- Old Dinosaur Unearthed from a Houseboat Expedition Is Zimbabwe’s Fifth Named Species

Phylogenetic analyses place it in the clade Unaysauridae, a group of early sauropodomorph dinosaurs restricted (so far) to the Late Triassic of Gondwana.

The Late Paleozoic Ice Age (LPIA), also called the Late Paleozoic Icehouse or (formerly) the Karoo Ice Age, was the longest and most extensive icehouse interval of the Phanerozoic Eon. It lasted roughly 100- 110 million years, from the Late Devonian (~360 Ma) to the Late Permian (~255 Ma), with peak glaciation in the Carboniferous and Early Permian

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Musango matusadonaensis (or simply Musango), a new species of early sauropodomorph dinosaur from Zimbabwe’s Lake Kariba area.

It lived about 210 million years ago in the Late Triassic (Norian stage), when dinosaurs were spreading but had not yet become dominant land animals.

This bipedal early relative of later giant long- necked forms like Diplodocus was relatively lightly built, roughly 4.5 meters (15 feet) long and about 222 kg (around 490 pounds, comparable to a large pig). It was nearly fully grown (estimated age ~8 years) when it died and shows evidence of having recovered from a serious injury or infection. Its skull is missing, but it was likely a herbivore or omnivore that fed on plants along rivers and streams.

The partial skeleton (vertebrae, ribs, limb bones, and parts of the hip and shoulder) was excavated in 2018 from the Pebbly Arkose Formation near the shore of Lake Kariba (near Matusadona National Park/Musango Island) in northern Zimbabwe.

It comes from the same rock unit as the previously named Musankwa sanyatiensis (announced earlier from the same expeditions), indicating diverse dinosaur ecosystems in the region rather than a uniform fauna across southern Africa.

The discovery method was unusual: a joint team of Zimbabwean, South African, and British paleontologists conducted expeditions in 2017 and 2018 from a houseboat/riverboat (a floating base/lab) on the lake.

This was necessary because the site is in a remote national park with dangerous wildlife (elephants, hippos, etc.), where camping is restricted and road access is limited. They used smaller boats to reach the shoreline exposures.

The species name references the local Shona word “musango” (roughly “living in the bush”) and the Matusadona area; the earlier Musankwa was named after the houseboat itself and a nearby river.

It is only the fifth dinosaur species formally named from Zimbabwe. The formal description appeared in the Journal of Systematic Palaeontology (around late July 2026), with coverage continuing into September 2026. Researchers view finds like this as the “tip of the iceberg” for Africa’s understudied fossil record and plan further work in the area.

In short, the headline matches a real recent paleontological announcement highlighting both a scientifically interesting early sauropodomorph and the practical challenges (and creative solutions) of fieldwork in a remote African lake setting.

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Phylogenetic analyses place it in the clade Unaysauridae, a group of early sauropodomorph dinosaurs restricted (so far) to the Late Triassic of Gondwana.

Musango is recovered as the sister taxon to the sympatric Zimbabwean form Musankwa sanyatiensis (from the same Pebbly Arkose Formation).

The broader Unaysauridae also includes Unaysaurus and Macrocollum (from Brazil, South America), plus Pradhania (from India). Some analyses show variable internal relationships among these taxa, but the overall grouping is consistently Gondwanan and Late Triassic (Norian) in age.

This supports the idea of a short- lived but geographically widespread Southern Hemisphere clade. Close morphological similarities (and shared derived features) with these relatives indicate that early sauropodomorphs could disperse across large distances while Africa, South America, India, and other landmasses remained connected within the southern portion of Pangaea (Gondwana).

During the Late Triassic (~210 million years ago), continuous land connections across Gondwana allowed faunal interchange. The presence of closely related unaysaurids in what Zimbabwe, Brazil, and India are now consistent with this.

Some popular or secondary accounts also note affinities or comparisons involving South African material, though the formal description emphasizes that no dinosaur taxa are currently shared between the Triassic deposits of Zimbabwe (Mid-Zambezi Basin) and the classic main Karoo Basin of South Africa. This actually strengthens the emerging picture of regional provincialism (distinct local ecosystems) within a still-connected supercontinent, rather than a completely uniform southern African fauna.

In short, Musango adds evidence that early dinosaurs (and specifically this lineage of bipedal sauropodomorphs) were capable of wide geographic ranges across joined continents, while also highlighting that local environmental differences produced more diverse, regionally distinct communities than previously assumed.

This fits the larger pattern of Gondwanan dinosaur biogeography during the rise of the group in the Late Triassic.

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The Late Paleozoic Ice Age (LPIA), also called the Late Paleozoic Icehouse or (formerly) the Karoo Ice Age, was the longest and most extensive icehouse interval of the Phanerozoic Eon. It lasted roughly 100- 110 million years, from the Late Devonian (~360 Ma) to the Late Permian (~255 Ma), with peak glaciation in the Carboniferous and Early Permian.

It was not a single continuous glaciation but a dynamic series of discrete glacial episodes (lasting ~1- 8 million years or longer) separated by warmer interglacial or ice-minimum intervals of similar duration. Ice centers shifted diachronously as the southern supercontinent Gondwana drifted across the South Pole:

  • Early phases began in western South America (Andean basins) in the Late Devonian- Early Carboniferous.
  • Ice expanded eastward across Africa, Antarctica, India, and into Australia.
  • Major peaks occurred in the Late Carboniferous (Pennsylvanian, ~315 Ma) and Early Permian (Cisuralian/Sakmarian, ~295 Ma).
  • Final alpine- style glaciers persisted longest in eastern Australia, disappearing by the late Wuchiapingian (~255 Ma).

Evidence includes widespread glacial deposits (tillites, diamictites, dropstones, striated pavements, and glacial landforms) across Gondwana, notably the thick Dwyka Group in the Karoo Basin of southern Africa and the Itararé Group in Brazil’s Paraná Basin.

Primary drivers included:

  • Low atmospheric CO₂ — Levels dropped to some of the lowest of the Phanerozoic (possibly near or below modern values at times), largely due to the expansion of land plants (which buried organic carbon in vast coal swamps) and enhanced silicate weathering from mountain building (e.g., the Variscan/Hercynian orogeny during Pangaea assembly).
  • Paleogeography — Gondwana’s position over the South Pole provided high- latitude land for ice nucleation; the assembly of Pangaea altered ocean circulation, continental weathering, and climate belts.
  • Secondary factors: Orbital (Milankovitch) cycles influenced shorter- term ice- volume fluctuations; tectonic uplift created highlands favorable for glaciers.

Oxygen levels were correspondingly high, supporting large arthropods and other fauna in the Carboniferous.

Effects and Impacts:

  • Sea level — Large glacioeustatic fluctuations (tens of meters or more) produced cyclic sedimentary sequences (cyclothems) in low- latitude basins, alternating marine and non- marine deposits.
  • Climate — Strong equator- to- pole temperature gradients; low- latitude regions experienced monsoonal or seasonal climates linked to high- latitude ice volume. Equatorial areas saw “everwet” conditions during some glacial phases, shifting toward more arid or seasonal patterns as ice waned.
  • Biosphere — Influenced the distribution of coal- forming forests, marine biotas, and terrestrial ecosystems. The icehouse– greenhouse transition at the end of the LPIA set the stage for the warmer, more arid climates of the Late Permian and Triassic.
  • Landscape — Glacial erosion shaped significant topography (e.g., in East Antarctica and southern Africa), some of which is still preserved today after burial and later exhumation.

The LPIA ended gradually through the Middle- Late Permian as Gondwana drifted away from the pole, CO₂ levels rose (partly due to reduced weathering and changes in plant carbon sequestration), and ice sheets contracted. By the Late Permian, Earth had shifted into a greenhouse state that persisted into the Triassic, the climate backdrop for the early dinosaurs and the ecosystems discussed in prior context (including those of southern Gondwana where Musango later lived).

The LPIA is particularly significant as the only major icehouse- to- greenhouse transition recorded while complex terrestrial ecosystems (including forests and tetrapods) were already established, offering a deep- time analog for understanding long- term climate dynamics and feedback.

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Pangaean climate shifts refer to the major changes in global and regional climate that occurred while Earth’s continents were assembled into the supercontinent Pangaea (roughly late Carboniferous to mid- Jurassic, ~335- 170 million years ago). These shifts were driven by the unique geography of a vast landmass, fluctuating greenhouse-gas levels, volcanism, orbital cycles, and the eventual breakup of the supercontinent.

Pangaea stretched nearly from pole to pole and was surrounded by the enormous Panthalassa ocean, with the Tethys Sea as a large eastern embayment. This configuration produced:

  • Extreme continentality: Hot summers and cold winters in the vast interior, with limited ocean moderation.
  • A broad arid belt across low- to- mid latitudes (especially the continental interior), one of the most extensive desert systems in Earth history.
  • The Pangaean megamonsoon: Intense seasonal wind reversals driven by strong land- sea temperature contrasts. Summer monsoons brought heavy rains to coastal and equatorial regions facing Tethys, while winters were dry. The megamonsoon intensified as Pangaea reached its maximum size in the Triassic.

Overall, the climate was a greenhouse (“hothouse”) world with no permanent polar ice caps for most of the time, though high latitudes experienced cooler, more temperate conditions suitable for forests.

Key Climate Shifts Through Time

Late Carboniferous–Early Permian (~320–280 Ma)
Assembly of Pangaea was underway. Equatorial regions were initially wetter (supporting extensive coal forests), but progressive aridification occurred as mountain ranges (Central Pangaean Mountains) created rain shadows and low-latitude seaways closed. The Late Paleozoic Ice Age still influenced southern Gondwana.

Middle–Late Permian
Climates warmed and dried further. Deserts expanded in tropical/subtropical areas. Seasonal rainfall increased in some regions, but overall aridity grew.

Permian–Triassic transition (~252 Ma)
A dramatic shift into extreme hothouse conditions, triggered primarily by massive Siberian Traps volcanism. Huge releases of CO₂ (and possibly methane) caused rapid global warming, ocean anoxia, acidification, and intensified aridity in many mid-latitude areas. Tropical sea- surface temperatures may have reached lethal levels (~40 °C) in the Early Triassic. Vegetation collapse reduced carbon sequestration, helping sustain high CO₂ and super- greenhouse conditions for several million years. This interval coincides with the end-Permian mass extinction.

Early–Middle Triassic
Continued hot, dry conditions with a prolonged “coal gap” (limited forests). Recovery was stepwise. Climatic oscillations occurred, with intermittent rainfall possibly linked to a strengthening megamonsoon. Polar regions remained relatively mild.

Late Triassic
The megamonsoon reached peak intensity. Three broad climatic regions developed: arid interiors, more humid coastal/monsoonal zones, and higher- latitude temperate belts. Climate was strongly seasonal and non-zonal (not strictly latitude-controlled in the usual way).
Notable events include:

  • The Carnian Pluvial Episode (~234–232 Ma): A multi-pulse interval of increased global humidity and rainfall linked to Wrangellia large igneous province volcanism and carbon- cycle perturbations. This temporarily expanded lakes, wetlands, and hygrophytic (moisture-loving) plants, with biotic turnovers.
  • Later cooling and aridification episodes, including the Rhaetian Cool Interval.
  • Orbital (Milankovitch) forcing produced ~10,000- and ~20,000-year cycles that influenced lake levels and precipitation, creating latitudinal climate zones that sorted faunas (e.g., different tetrapod assemblages in humid vs. arid belts).

Jurassic onward (breakup phase)
Fragmentation increased continental runoff and silicate weathering, drawing down atmospheric CO₂. Climates became wetter overall, seasonal contrasts decreased in many regions, and the extreme interior aridity diminished. Dryland coverage, which had been high (~50- 60% of land during peak Pangaea), declined significantly by the Cretaceous.

Drivers of the Shifts:

  • Paleogeography: Supercontinent size and configuration controlled moisture transport, monsoons, and the extent of arid interiors. Breakup reversed many of these effects.
  • Greenhouse gases: Volcanism (Siberian Traps, Wrangellia, CAMP) and reduced plant- driven carbon sequestration raised CO₂; weathering and organic burial lowered it.
  • Orbital cycles: Modulated precipitation and seasonality on shorter timescales.
  • Feedback: Vegetation loss amplified warming; ice- albedo and ocean circulation effects played secondary roles.

These climate shifts strongly influenced ecosystems, favoring drought- adapted plants and animals in arid interiors, enabling provincial (regionally distinct) faunas despite the continuous landmass, and creating the environmental backdrop for the rise of dinosaurs in the Late Triassic.