Jurassic Park Period Part 3

Flora

And now, let's move on to living things, such as plants. There's a lot of ground to cover, so to speak, so let's get to it. There is no evidence of a mass extinction of plants at the Triassic/Jurassic boundary, although some species did decline or even die out in some areas.

Conifers form a dominant component of Jurassic floras, when they underwent a major time of diversification. Most modern conifer groups appeared by the end of the Jurassic.

The oldest definitive record of the cypress family is from the Early Jurassic and were found in Patagonia (the southern area of South America). By the middle of the Jurassic, the cypress were abundant in warm temperate-tropical regions of the Northern Hemisphere.

Ancestors of the current pine family were widely distributed across Eurasia during the Jurassic.

The flora of the mid-latitudes of Eastern Asia were dominated during the Early Jurassic by a broad leafed conifer which shed its leaves seasonally, and which is not closely related to any living family of conifer. It extended northwards into polar latitudes of Siberia, and then contracted northward because of increasing aridity of the region.

Evidence of the yew family have been found in Sweden, England and China dating from the Middle Jurassic. They appear to be closely related to modern yew specimens.

Ginkgoales—which today has only one living specie, the Ginkgo biloba—were more diverse during the Jurassic, and were among the most important components of Eurasian Jurassic flora, adapted to a wide variety of climatic conditions.

Bennettitales are a group of seed plants that reached a peak diversity during the Triassic and Jurassic periods. Although they bear some resemblance to cycads, they are not believed to be closely related to them. All Jurassic Bennettitales grew as shrubs and small trees, and were adapted to grow in open habitat with poor soil. They also had flower-like reproductive structures that are thought to have been pollinated by insects.

Cycads reached their apex of diversity during the Jurassic and Cretaceous (which comes next) periods. Although this era is sometimes called the 'Age of Cycads', cycads are thought to have been a relatively minor component of Jurassic flora. Their foliage is often confused with that of Bennettitales and other plants. Cycads are thought to have been mostly confined to tropical and subtropical latitudes.

There are no widely accepted Jurassic records of true flowering plants, and fossil evidence suggests that the group diversified during the period following the Jurassic.

'Seed ferns' is a collective term to refer to fern-like plants that produce seeds but have uncertain affinities to living seed plant groups. One prominent group of seed ferns reached their zenith during the Jurassic and was widespread in the Northern Hemisphere, although records in the Southern Hemisphere are rare.

Another group of seed plants are known from the Late Triassic through the Jurassic to the Cretaceous. They are thought to have been tree- or shrub-like, and formed a conspicuous component of Northern Hemisphere Mesozoic temperate and warm-temperate floras. Another group of seed plants called the Pentoxylales, first appeared during the Jurassic, but appear to have been confined to Gondwana.

Many living families of fern were widespread during the Jurassic period. The Polypodiales ferns, which make up 80% of living fern diversity, have no record from the Jurassic and are thought to have diversified later, during the Cretaceous.

The oldest remains of modern horsetails first appear in the Early Jurassic. I could have sworn I heard mention of horsetails in earlier periods, but those must not have made it to modern times.

The Cyatheales, the group containing most modern tree ferns, appeared during the late Jurassic.

Quillworts that are virtually identical to modern species are known from the Jurassic onwards.

Various mosses have left fossil records from the Jurassic and are believed to be related to modern mosses. Several records of liverwort have also been found from the Middle Jurassic.

https://en.wikipedia.org/wiki/Jurassic

Jurassic Park Period Part 2

Paleoclimate

Climate during the Jurassic was approximately 5-10 degrees C (41-50 degrees F) hotter than present time, with atmospheric carbon dioxide likely 4 times higher. It's likely that forests grew near the poles, where they experienced warm summers and cold, sometimes snowy winters. It is unlikely there were any ice sheets, as the high summer temperatures would have prevented the accumulation of snow, although there may have been mountain glaciers. The ocean depths were likely 8 degrees C (about 46 degrees F) warmer than present, and coral reefs grew further north and south by 10 degrees of latitude There were probably large areas of desert in the lower latitudes.

The beginning of the Jurassic was probably marked by a thermal spike corresponding to the eruption of the Central Atlantic magmatic province. This was followed by the Early Jurassic cool interval between 199 and 183 million years ago. ('Cool', of course, is a relative term.) Then came a spike in global temperatures of around 4-8 degrees C (39-46 degrees F) during the eruption of the Karoo-Ferrar large igneous provinces in southern Gondwana, which lasted from 183 million years ago until 174 million years ago.

During this long temperature spike, the ocean surface temperatures likely exceeded 30°C (86°F) and all the land mass between 30°N to 30°C were likely extremely arid, with temperatures in the interior in excess of 40°C (104°F).

There was an episode of widespread oceanic anoxia that is often attributed to the eruption of the Karoo-Ferrar large igneous provinces and the associated increase of carbon dioxide concentration in the atmosphere. This event had significant impact on marine invertebrates, but little effect on marine reptiles. During this time, the Sichuan Basin (of southwestern China) was transformed into a giant lake, 3 times the size of Lake Superior. Seawater pH dropped to its lowest point around the middle of this event.

This was followed by a (relatively) cool period between 174 and 164 million years ago, which was followed by a warm interval between 164 and 150 million years ago. During this warm interval, the land mass interior had less severe seasonal swings than before because the expansion of the Central Atlantic and the western Indian Oceans provided new sources of moisture to moderate the temperature. The end of the Jurassic was marked by another cool interval, which began 150 million years ago and continued beyond the end of the Jurassic.

I recently saw someone on social media poo-pooing concern over the climate changing. As they put it, the climate has been changing for millions of years. And they are right, it has been. What they fail to take into consideration is that mass extinction events have been happening for millions of years, AND the climate changes of the past have not occurred as rapidly as this one. If we want to survive this climate change, we need to use the brains we have.

https://en.wikipedia.org/wiki/Jurassic