What was the environment like 66 million years ago?

Question: What was the environment like 66 million years ago?

Answer: 

66 million years ago marked the end of the Cretaceous Period, occurring between the Jurassic and Paleogene Periods.

What was the environment like 66 million years ago?

Geography

The Earth’s landmasses changed greatly in position during this period. The two established supercontinents were Laurasia and Gondwana. Africa, South America, Australia, India, Madagascar, and Antarctica formed the continent of Gondwana in the south. The continent of Laurasia consisted of North America, Eurasia, and Greenland in the north. By the end of the Cretaceous Period, North America and Eurasia had separated. Gondwana had also split into Africa, Antarctica, Madagascar, India, and South America.

The sea level was 660 to 820 feet higher than the present day during the late Cretaceous period. Scientists believe the enlargement of midoceanic ridges caused water displacement in the ocean basins. This resulted in high sea levels. Oceans then formed shallow epicontinental seas in North and South America, Europe, Africa, Australia, and Russia. Continents then began to shrink slightly in size. The land covered about 18% of the Earth’s surface. Today, 28% of the Earth is covered by land.

Geoidal eustacy is thought to be the reason for continental transgression. The oceans tend to expand as the continents shift. Sea levels then vary in the different ocean basins.

Climate

Although the Late Cretaceous Period was cooler in temperature than earlier in the period, the temperatures were still much higher than in the present day. Tropical and subtropical regions occurred as far north as 45 degrees. Temperate climates existed up to the polar regions. Glaciers were only present in high mountainous regions. 

Flora and Fauna

Angiosperms (flowering plants) occurred during the Cretaceous period, e.g., magnolias, poplars, figs, sycamores, herbaceous plants, and willows. New plant species resulted in the diversification of insects.

Dinosaurs had already established themselves as the dominant species, and placental mammals first appeared. Snakes, lizards, clams, and most fishes formed their modern features. Marine reptiles included mosasaurs, plesiosaurs, ichthyosaurs, teleost fish, sharks, and rays. Rudist bivalves dominated the coral reefs in the Tethyan region. Actaeonellid, nerineid snails, calcareous algae, benthic foraminiferans, colonial corals, echinoids, and ammonites also existed in these areas. 

The colder boreal regions included belemnites, reclining bivalves, and inoceramids. Plankton acquired modern characteristics during the Cretaceous Period. Coccolithophores, coiled and straight ammonites, diatoms, dinoflagellates, radiolarians, calpionellids, and ostracods were all present during this time.