now lets see the how the jurassic life worked in that very best Jurassic period with me irvin
On land gymnosperm plants were well represented. The superficially palm-like Cycadophyta (Cycads) were so abundant and diverse that the Jurassic period could well be called "the Age of Cycads" Some cycads were tall palm-like trees with rough branches marked by leaf scars, and pinnate (fern-like) leaf fronds. Other, unrelated forms, the equatorial flowering Bennettitales, were the most important group of shrubby trees, with short and stubby with squat bulbous trunks from the top of which the fronds grew.
Conifers continued to be the most diverse large trees, and included representatives of the extant (still living) families Araucariaceae, Cephalotaxaceae, Pinaceae, Podocarpaceae, Taxaceae, and Taxodiaceae, along with the extinct equatorial Cheirolepidiaceae. Ginkgos were important, particularly in mid to high northern latitudes. Dicksoniaceous tree ferns and Caytoniaceous seed ferns were relatively successful plants in the shrubby tree size range. The Cyatheaceae tree ferns may have (and still do) reach(ed) heights of 20 meters. Osmundaceous, matoniaceous, and dipteridaceous ferns were probably the dominant undergrowth and small plants. Lycopods remained relatively insignificant and sphenopsids were represented by the small (and still surviving "living fossil") Equisetum or "horsetail"
In the seas there was a great diversity of invertebrates. Sponges, corals, bryozoa, gastropods, bivalves, and ammonoid (left) and belemnite cephalopods all flourished, the latter two groups becoming the dominant nektonic invertebrates for the rest of the Mesozoic.
Brachiopods and Crinoids continued, but with nowhere like their Paleozoic glory.
Freshwater bivalves (clams), snails, and branchiopod Crustacea were common. On land, numerous groups of herbivorous insects were present, including the orders Orthoptera, Hemoptera (among which were the superfamilies Cicadelloidea and Fulgoroidea (leafhoppers), Psylloidea (plant hoppers), Pentatomoidea (shield bugs), and Cimicoidea (plant bugs)), Thysanoptera (thrips), Coleoptera (beetles, including most extant groups) and primitive Hymenoptera (sawflies). Pulmonate snails, millipedes, scorpions, spiders and mites were certainly present, but are not known from fossils.
As for the vertebrates, modern shark groups begin to appear. Bony fish are still mostly the intermediate heavy scaled holostean type, although the first teleosts appear early in the period. The gigantic Leedsichthys, a huge, scaleless filter feeder, reached 10 or even 30 meters in length, and filled the same ecological role as modern baleen whales.
On land, a few basal tetrapods struggled on, but most amphibians were of essential modern types (frogs and newts), although the most primitive representatives of those orders.
Sphenodont lepidosaurs took the same ecological role as lizards do today. Crocodiles were abundant and diverse, and included marine, semi-aquatic and even a few small lizard-like terrestrial forms.
In the oceans new types of ichthyosaurs replaced their Triassic predecessors. The cousins of the Triassic nothosaurs, the long-necked plesiosauroids and short-necked pliosauroids, were also common. All these marine reptiles, filled similar ecological roles to cetaceans of the Cenozoic. In the air were various types of pterosaur, these were mostly small to medium-sized forms, all were endothermic with a covering of fur.
Dinosaurs were diverse and abundant, and their was a rich megafauna of huge sauropods (including a number of families - Euhelopidae, Cetiosauridae, Brachiosaurus, Camarasaurs, Diplodocidae, etc), reaching many tons in weight, and the more modestly sized Scelidosauridae, Stegosauridae, and the camptosaurid iguanodonts. The browsing pressure these great beasts exerted on the vegetation must have been tremendous, although there is continuing argument whether the dinosaurs were ectotherms, endotherms, homeotherms, gigantotherms, or (as seems most likely) some combination of all of the preceding. Obviously, the higher their metabolism the greater the selection pressure they would have exerted on the contemporary vegetation. Along with the giant herbivores there were also the small fleet-footed "fabrosaurs", scutellosaurs, and hypsilophodontids, the "gazelles" of the dinosaurian world. These plant eaters were kept in check by a variety of carnivorous (theropod) dinosaurs, including small lightly built coelophysids, compsognathids, and ornitholestids, and larger (from several hundred kilos to several tons in weight) dilophosaurids, Ceratosauria, Torvosauroidea, and Allosauridae. Some of the smaller carnivores developed feathers and took to the air, these were the proto-bird Archaeornithes.A few tritylodontid therapsids straggled on, but it was a diverse assemblage of Mesozoic Mammals that played an important part of the microvertebrate fauna, filling the same ecological role as Insectivora and rodents do today.
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