Jurassic Park Period Part 4

Fauna - Reptiles

During the Jurassic, dinosaurs came to dominate the animal world, but they were not the only type of animals. The first birds appeared, evolving from a branch of theropod (hollow-boned) dinosaurs, to share the skies with pterosaurs, the dominant flying vertebrates. Lizards made an appearance and have been with us ever since. Therian mammals evolved, meaning creatures that gave birth to live young, and that includes marsupials. Crocodylomorphs (which eventually gave rise to modern crocodylia, but not during the Jurassic) transitioned from a terrestrial to an aquatic life. The oceans were inhabited by marine reptiles such as ichthyosaurs and plesiosaurs.

This is a lot of ground to cover (so to speak), so I'm going to start in the oceans and work my way to land and sky.

The Triassic/Jurassic extinction event decimated crocodile-like reptilian diversity, with crocodylomorphs (which originated during the last half of the Triassic) being the only group to survive. Even the herbivorous aetosaurs died out. [Can you imagine if they had survived, and we had vegetarian crocodiles raiding our gardens?] The diversity of crocodylomorphs during the Early Jurassic was about the same as those of the Late Triassic, but they occupied different ecological niches.

A group of predominantly marine crocodylomorphs became a prominent part of marine ecosystems. Within that group, some became highly adapted for life in the open ocean, including the transformation of limbs into flippers, the development of a tail fluke, and smooth, scaleless skin.

Turtles - Turtles (Testudinata) diversified during the Jurassic. The Jurassic turtles are believed to have formed 2 more advanced groups, the Mesochelydia (which were aquatic), and the Perichelydia. There are 2 modern groups turtles (the Testudines), which are terrestrial and had diverged by the Middle Jurassic. The Thalassochelydia is a diverse lineage of sea turtles, and is known from the Late Jurassic of Europe and South America.

Lepidosaurs - The tuatara is a reptile native only to New Zealand, and is the sole living representative of the Rhynchocephalians, which had achieved a global distribution by the beginning of the Jurassic. The Rhynchocephalians occupied a wide range of lifestyles, including the aquatic pleurosaurs with long snake-like bodies and reduced limbs, the herbivorous eilenodontines, and the Oenosaurus, which had broad tooth plates indicative that they ate creatures that were hard-shelled or had an exo-skeleton, such as corals, shelled mollusks and crabs. Rhynochocephalians disappeared from Asia after the Early Jurassic. The last common ancestor of living squamates (which includes lizards and snakes) is estimated to have lived around 190 million years ago during the Early Jurassic. Squamates first appear in the fossil record during the Middle Jurassic and included early members of a snake lineage. However, many Jurassic squamates have unclear relationships to living groups. Eichstaettisaurus from the Late Jurassic of Germany has been suggested to be an early relative of geckos and displays adaptations for climbing.

Ichthyosaurs - The Ichthyosaurs suffered an evolutionary bottleneck during the Triassic/Jurassic extinction event, with all but one group of them becoming extinct. Ichthyosaurs reached its apex of species diversity during the Early Jurassic, including the huge apex predator Temnodontosaurus and the swordfish-like Eurhinosaurus. However, Early Jurassic ichthyosaurs were significantly less morphologically diverse than their Triassic counterparts

Plesiosaurs - The Plesiosaurs originated at the end of the Triassic Period. At least 6 lineages of plesiosaur crossed the Triassic-Jurassic boundary, so they were already diverse in the Earliest Jurassic. Early plesiosaurs were generally small-bodied, with body size increasing later. There appears to have been a strong turnover as the middle of the Jurassic Period began, with the extinction of 2 groups that had been widespread, and the first appearance of the Cryptoclididae group, which became the dominant group of the latter half of the Jurassic. During this time, the thalassophonean pliosaurs, which had ancestrally been small-headed and long-necked, evolved short necks and large heads. Some species, such as the Pliosaurus, had skulls up to 2 metres (6 ft) in length, with body lengths estimated around 10-12 meters (30-36 feet), making them the apex predators of Late Jurassic oceans. Small-bodied plesiosaurs also invaded freshwater environments during the Jurassic, as shown by remains found in freshwater sediments from China and Australia.

Pterosaurs - Pterosaurs first appeared in the Late Triassic, but a major group of Jurassic pterosaurs is the Rhamphorhynchidae, which first appeared in the Early Jurassic. They ate fish. Another group, the Anurognathids, first appeared in the Middle Jurassic. They had short heads and densely furred bodies, and were probably insectivores. Short-tailed pterodactyloids first appeared in the at the beginning of the Late Jurassic. These include the ctenochasmatids, which have closely spaced needle-like teeth that were presumably used for filter feeding. The Late Jurassic Cycnorhamphus had a jaw with teeth only at the tips, with bent jaws like those of living openbill storks, that may have been used to hold and crush hard invertebrates.

Some of these animals could be found on land, as indicated in the above paragraphs by what they ate. But I'm fairly confident that they had branches of relatives living in the oceans. I am sorry for the use of huge tongue-twisting names, but there were so many names, I would have gotten completely bogged down trying to describe the various species.

There you have some of the reptiles that lived in the oceans and other waterways. This has been a long post, so I am going to end it here and take up fish next time. Yes, there were fish in the waters, too.

There will not be a quiz on the names used in this blog. Class dismissed.

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

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

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