Paper 60 Overview: Urantia During the Early Land-Life Era

This paper chronicles the transition from marine-dominated life to the establishment and development of land-based organisms on earth approximately 150 million years ago. It details the rise and dominance of reptiles, particularly dinosaurs, who ruled the planet for tens of millions of years until their eventual extinction. The narrative also covers the first appearances of mammals, the emergence of flowering plants, the development of birds, and the geological processes that shaped earth's mountains and continents during this period.

The paper divides this evolutionary epoch into distinct stages: the Early Reptilian Age (Triassic period), the Later Reptilian Age (Jurassic period), the Cretaceous Stage (marked by flowering plants and birds), and the conclusion of the Chalk Period. Throughout these stages, the planet underwent dramatic geographical transformations, including continental movements, mountain formations, sea level changes, and volcanic activity, all of which influenced the development and distribution of life forms that would eventually lead to the conditions necessary for human existence.

The exclusive era of marine life had come to an end on earth, giving way to the emergence of land-based organisms. This transition was facilitated by several crucial planetary changes: land elevations, cooling of both the earth's crust and oceans, restriction and consequent deepening of seas, and a significant increase in northern land masses. These factors collectively transformed the world's climate, particularly in regions far from the equatorial zone.

The closing epochs of the preceding era had been dominated by frogs, but these ancestors of land vertebrates were no longer prevalent, having dramatically declined during the previous period of biological challenges. Very few species survived the harsh trials of this transitional time, and even spore-bearing plants were nearly extinct, signaling a major shift in the planet's biological composition and preparing the stage for new dominant life forms.

The erosion deposits from this period consisted mostly of conglomerates, shale, and sandstone, with gypsum and red layers throughout these sedimentations across America and Europe indicating an arid climate. These dry regions experienced significant erosion from violent and periodic cloudbursts on the surrounding highlands, shaping the landscape. Few fossils can be found in these layers, though numerous sandstone footprints of land reptiles are preserved, while in many regions the thousand-foot red sandstone deposits contain no fossils whatsoever, as land animal life continued only in certain parts of Africa.

Around 150 million years ago, the early land-life periods began, with life generally faring better than during the challenging conclusion of the marine-life era. North America became geographically isolated for the first time, though this separation was brief as the Bering Strait land bridge soon reconnected it with Asia. Great troughs developed paralleling the Atlantic and Pacific coasts, and reptiles appeared suddenly about 140 million years ago, rapidly evolving into crocodiles, scaled reptiles, sea serpents, and flying reptiles. These reptilian dinosaurs quickly became the dominant species, distinguished by their small brains relative to their massive bodies, with some later weighing up to forty tons despite having brains weighing less than a pound.

About 120 million years ago, a new phase of the reptilian age began with the evolution and eventual decline of the dinosaurs. Land animal life reached its greatest development in terms of physical size during this period, but by its conclusion, dinosaurs had virtually disappeared from earth. These creatures ranged from smaller than two feet to the enormous plant-eating varieties measuring seventy-five feet in length, which have never since been equaled in size by any living creature. Their remains are found throughout the Rocky Mountains, along the Atlantic coast of North America, across western Europe, and in South Africa and India.

As these massive creatures grew larger, they became less active and strong, requiring enormous amounts of food. The land became so overrun with dinosaurs that they literally starved to death and became extinct, lacking the intelligence to address their own overconsumption. During this period, most of eastern North America was leveled by erosion and washed into the Atlantic Ocean, extending the coastline several hundred miles beyond its current position. It was predominantly a freshwater age with many inland lakes, as evidenced by abundant freshwater fossils in Colorado, Montana, and Wyoming. The climate remained mild, allowing corals to flourish in European waters, though they never reappeared in the gradually cooling polar seas.

The great Cretaceous period derives its name from the abundance of chalk-making foraminifers in the seas and represents the approach to the end of reptilian dominance. This era witnessed the appearance of flowering plants and bird life on land, while also marking the end of westward and southward continental drift. These changes were accompanied by tremendous crustal deformations, widespread lava flows, and significant volcanic activity across the planet. The contention between geologic forces gave rise to the formation of the vast north-south mountain range extending from Alaska through Mexico to Cape Horn, making this the modern mountain-building stage of geologic history.

Around 90 million years ago, angiosperms (flowering plants) emerged from the early Cretaceous seas and rapidly spread across the continents, soon joined by fig trees, magnolias, and tulip trees. The closing of the Bering Strait about 85 million years ago isolated the cooling waters of the northern seas, equalizing the previously different temperatures between Atlantic-Gulf waters and the Pacific Ocean. The period's sedimentations, consisting of chalk, shale, sandstone, and small amounts of limestone, vary in thickness from 200 feet to 10,000 feet in western North America and European locations. About 55 million years ago, the first true birds appeared – small, pigeon-like creatures that evolved directly from reptiles rather than from contemporary flying dinosaurs or earlier toothed land birds, marking this as both the age of birds and the declining age of reptiles.

The conclusion of the Cretaceous period marks the end of major sea invasions of the continents, particularly in North America, which had experienced twenty-four great inundations. While subsequent minor submergences occurred, none matched the extensive marine invasions of this and previous ages. These alternating periods of land and sea dominance followed million-year cycles, exhibiting a rhythmic pattern of rising and falling ocean floors and continental land levels, though with diminishing frequency and extent over time. This period also witnessed the end of continental drift and the formation of earth's modern mountains, with mountain building influenced not only by continental pressure but also by pre-existing lowlands filled with lighter deposits.

The oldest mountains on earth are located in Asia, Greenland, and northern Europe among the older east-west systems, while mid-age mountains belong to the circumpacific group and the second European east-west system. The youngest mountains are in the Rocky Mountain system, where land had repeatedly risen and been covered by the sea before the formation of the present range. Biologically, this period saw sea urchins increase while corals and crinoids decreased, and on land, fern forests were largely replaced by pine and other modern trees, including giant redwoods. By the period's end, though placental mammals had not yet evolved, the biological conditions were set for the appearance of the ancestors of future mammalian types, concluding the fifty-million-year Cretaceous age and the hundred-million-year premammalian era of land life known as the Mesozoic.