Paper 59 Overview: The Marine-Life Era on Urantia

The history of Urantia is divided into five major eras spanning one billion years, with the marine-life era covering approximately 250 million years during what scientists call the Paleozoic period. This significant era can be subdivided into six long periods, each characterized by specific developments in both geological formations and biological evolution. The marine-life era represents about one quarter of the planet's history and established the foundation for all subsequent life development.

During this era, sea bottoms, continental shelves, and near-shore basins became covered with prolific vegetation, while primitive animal organisms evolved from preceding plant life forms. These early animals gradually populated the extensive coastlines, eventually filling the inland seas with diverse marine life. Though few early organisms had shells that could be preserved as fossils, this era began recording the chapters of earth's "stone book" of life records that would be methodically developed during subsequent ages, with North America containing particularly rich fossil deposits that clearly show the separation between this and earlier periods.

We divide Urantia's history into five major eras spanning one billion years: the prelife era (450 million years), the life-dawn era (150 million years), the marine-life era (250 million years), the early land-life era (100 million years), and the mammalian era (50 million years). The marine-life era represents approximately one quarter of planetary history and can be subdivided into six distinct periods, each characterized by specific developments in both the geological realms and biological domains. This classification system provides a framework for understanding earth's developmental history.

As this era begins, sea bottoms, continental shelves, and numerous shallow near-shore basins become covered with prolific vegetation, while simple animal organisms evolve from preceding plant forms. These early animal organisms gradually spread along extensive coastlines, eventually filling the many inland seas with primitive marine life. Since few of these early organisms possessed shells, not many have been preserved as fossils, yet the stage was set for the opening chapters of the "stone book" of life records that would be methodically developed during subsequent ages. North America contains particularly rich fossil-bearing deposits from the entire marine-life era, with the oldest layers clearly separated from earlier periods by extensive erosion deposits.

By the dawn of this period, life was confined to various inland seas and oceanic shorelines, with no land organisms yet evolving. Primitive marine animals were well established and prepared for the next evolutionary development, with amebas being typical survivors from the preceding transition period. Around 400 million years ago, marine life—both plant and animal—became fairly well distributed worldwide as the climate grew warmer and more equable, leading to a general flooding of continental seashores, particularly in North and South America. New oceans formed while existing bodies of water greatly expanded in size.

Vegetation began crawling onto land for the first time and made considerable progress adapting to a non-marine habitat. Suddenly and without gradual ancestry, the first multicellular animals appeared, with trilobites evolving to dominate the seas for ages. From the standpoint of marine life, this truly was the trilobite age. During this period, much of North America and Europe emerged from the sea as earth's crust temporarily stabilized, with mountains rising along the Atlantic and Pacific coasts. The trilobite fossils found in rock strata from this time present certain basic uniformities coupled with well-marked variations, reflecting their development from the three original life implantations that produced slightly different organisms in the Western Hemisphere compared to the Eurasian group and the Australian-Antarctic type.

The periodic phenomena of land elevation and sinking characteristic of these times occurred gradually without spectacular events, being accompanied by little volcanic activity. Throughout these successive land fluctuations, the Asiatic mother continent did not fully share the history of other land bodies, experiencing many inundations in different directions but not developing the uniform rock deposits found on other continents. Around 350 million years ago, a great flood period began across all continents except central Asia, with land masses repeatedly covered by water while only coastal highlands remained above these shallow, widespread inland seas.

This period witnessed the development of lime-secreting algae, thousands of species of early coral ancestors, abundant sea worms, and various jellyfish that have since become extinct. Corals and later types of sponges evolved, while cephalopods became well developed and survived as modern pearly nautilus, octopus, cuttlefish, and squid. Shell animals flourished in ancient seas, including single-shelled gastropods like drills, periwinkles, and snails, along with bivalve species such as mussels, clams, oysters, and scallops. The world grew quiet and relatively peaceful by the end of this period, with a mild and equable climate that allowed land plants to migrate farther from shorelines, though all animals remained marine organisms since the atmosphere still contained too much carbon dioxide to support air-breathing creatures.

Around 300 million years ago, another major period of land submergence began as the ancient Silurian seas encroached southward and northward, engulfing most of Europe and North America. The land wasn't elevated far above sea level, resulting in minimal shoreline deposition. These seas teemed with lime-shelled life, and as these shells fell to the sea bottom, they gradually built up remarkably thick limestone layers averaging about 1,000 feet in thickness, which now cover practically all of Europe and North America, though they appear at the earth's surface in only a few places. This period marked the height of great water deposition with little mountain building activity.

The oceanic climate remained mild and uniform during this time, with warm seas bathing even polar shorelines. Gastropods, brachiopods, sponges, and reef-making corals continued to thrive and increase in numbers. Around 280 million years ago, the continents had largely emerged from the second Silurian inundation, with rock deposits from this submergence known in North America as Niagara limestone—the layer over which Niagara Falls now flows. This stratum extends from the eastern mountains to the Mississippi valley region but not farther west except to the south. By the end of this final Silurian submergence, the trilobites had nearly disappeared while mollusks continued as monarchs of the seas, and primitive water scorpions evolved, soon followed by the appearance of true scorpions—the first air-breathing land animals.

In the ongoing struggle between land and water, there were long periods when the sea was relatively victorious, but times of land victory were approaching. As land emerged from the last Silurian inundation, an important period in world development and life evolution began—the dawn of a new age when the once naked and unattractive landscape became clothed with luxuriant verdure as the first magnificent forests prepared to appear. Marine life during this time was highly diverse due to early species segregation, though later there was free commingling and association of these different types. Brachiopods reached their evolutionary peak, being succeeded by arthropods, while barnacles made their first appearance in the fossil record.

The most significant event of this period was the sudden appearance of the fish family, making this truly the age of fishes—a time characterized by vertebrate animal types. Around 270 million years ago, all continents stood above water, representing one of the greatest land-emergence epochs in world history. Many of the largest true fish belong to this age, with some tooth-bearing varieties measuring 25 to 30 feet long, while today's sharks are descendants of these ancient fish species. The earth was rapidly being overrun by new types of land vegetation, particularly the prolific fern family that quickly spread across rising land areas worldwide. Tree types two feet thick and forty feet high soon developed, though their leaves were only rudimentary compared to modern foliage. As the land continued rising, portions of both Europe and North America began to sink again, marking the beginning of the last and least extensive Devonian floods.

The appearance of fish during the preceding period marked the apex of marine-life evolution, after which the evolution of land life became increasingly important. Around 220 million years ago, most continental land areas, including North America, rose above the water and became covered with luxurious vegetation, particularly ferns. Carbon dioxide was still present in the atmosphere but in decreasing amounts, creating ideal conditions for the expanding plant life. Shortly afterward, the central portion of North America was inundated, creating two great inland seas that eventually united, commingling their different forms of marine life and marking the beginning of the rapid worldwide decline in marine life and the opening of the subsequent land-life period.

In this environment, the first land animals suddenly appeared—numerous species of air-breathing amphibians that developed from arthropods whose swim bladders had evolved into lungs. From the briny waters of the seas, snails, scorpions, and frogs crawled out onto land, with frogs still laying their eggs in water today so that their young first exist as little fish or tadpoles. Insects also appeared for the first time and quickly spread across the continents along with spiders, scorpions, cockroaches, crickets, and locusts. Some dragonflies measured thirty inches across, and certain cockroaches grew to four inches long. The land was periodically rising and falling due to shifting sea levels, and this crustal movement—combined with the prolific vegetation of coastal swamps—contributed to extensive coal deposits that have caused this period to be known as the Carboniferous.

This period marks the end of pivotal evolutionary development in marine life and the beginning of the transition leading to subsequent ages of land animals. It was a time of great life impoverishment when thousands of marine species perished and land-based life was hardly established. This truly represents an age of biologic tribulation, when life nearly vanished from both the earth's surface and ocean depths. At the beginning of the long marine-life era, over 100,000 species of living things existed on earth, but by the close of this transition period, fewer than 500 had survived these challenging conditions.

The unusual characteristics of this new period resulted not so much from cooling of the earth's crust or the long absence of volcanic activity, but rather from an uncommon combination of ordinary pre-existing influences—primarily the restriction of seas and increasing elevation of enormous land masses. The mild marine climate of former times was disappearing as harsher continental weather patterns developed. Around 170 million years ago, significant evolutionary changes and adjustments occurred across the entire planet as land rose while ocean beds sank. Earth's crust folded extensively during these elevations, marking a time of continental emergence except for the disappearance of certain land bridges that had long connected South America with Africa and North America with Europe.

By 160 million years ago, the land was largely covered with vegetation adapted to support land-animal life, and the atmosphere had become ideal for animal respiration. This marks the end of the period of marine-life curtailment and those testing times of biologic adversity that eliminated all life forms except those with sufficient survival value to serve as ancestors for the more rapidly developing and differentiating life of ensuing ages. The vast oceanic nursery of life on Urantia had served its purpose, and as the biologic importance of the sea diminished, the second stage of evolution began to unfold on land.