Photo by Jenna Richardson

Thomas Mcloughlin’s A Guide to Pennsylvanian (Carboniferous) Age Plant Fossils of Southwest Virginia is full of information about paleobotany and plant fossils.

As a veteran geologist who has been on the field for almost three decades, Thomas Mcloughlin has been collecting and investigating fossils in the Appalachian regions. The fruit of this committed exploration is A Guide to Pennsylvanian (Carboniferous) Age Plant Fossils of Southwest Virginia.

This book is a meticulous and comprehensive visual compilation of Pennsylvanian-age fossils found in the coal layers in the Appalachian Mountains. These fossils are divided accordingly, and readers can know where to find similar specimens. Accompanying the fossil images are brief descriptions and expositions presented in a clear and concise manner for easy comprehension by the general public.

With more than 71 plates and over 300 illustrations (the majority being full-color), the book is a marvelous piece of art and science. If you are interested in paleobotany and plant fossils, this book is a wonderful addition to your bookshelf.

But What Is the Pennsylvanian Age?

The Pennsylvanian, sometimes known as the Upper Carboniferous or the Late Carboniferous, is a fascinating part of the Earth’s history. It is named after the US state of Pennsylvania, where evidence of the period, in the form of expansive coal beds, can be found. The subperiod lasted from 323.2 to 298.9 million years ago.

Like with most other geochronological periods, the Pennsylvanian is quite defined by the geological layer, although the exact date of its beginning and end is within the difference of a few hundred thousand years.

Although a lot of artistic renderings of the Pennsylvanian depict its swampland, they were only abundant in the regions around the equator.

The Gondwana supercontinent took up most of the southern hemisphere, which experienced a series of ice ages during that time. These successive periods of growing and melting ice created repeating layers of sedimentary rock through cyclical covering and uncovering of coastal areas. The evidence of their existence can be found at sea level.

During the Pennsylvanian Age, the warmer and shallower seas of the previous period vanished and made way for cooler and more turbid waters, which saw massive changes in marine life. Over the land, forested wetlands dominated—the detritus buildup of these ecosystems gradually created much of the modern period’s coal beds.

The Pennsylvanian’s tropical forests also left their mark in the form of massive coal deposits, which can be found in much of North America and Europe. The dominant floral species of the period were giant club mosses, horsetails, ferns, and conifer-like trees called cordaites.

Animal Life During the Period

Because of the ecological supremacy of massive trees and vegetation, more than a fourth of the atmosphere was made up of oxygen. This saturation of oxygen led to the evolution of massive invertebrates that became the paramount class of animals. In particular, there was a flourishing of cockroaches leading to some referring to the Pennsylvanian as “The Age of Cockroaches.”

A dense diversity of animal species could be found in the woodlands and wetlands of this period.

Since vertebrate animals had not evolved the capacity to consume plants, insects and other invertebrates made up much of the population of plant-feeders. Amphibian populations saw an explosion of increased speciation, which is why the Pennsylvanian is also known as the Age of Amphibians.

The evolution of membranous and land-adapted eggs happened during this period, which would foreshadow the future dominance of land by vertebrate animals. Another development in this period was the evolution of the first reptiles, whose adaptations allowed them to quickly outnumber the amphibians, whose species were restricted to specific locales.

Prominent traces of glaciation (and more evidence of dropping sea levels) indicate when the Pennsylvanian began. The general climate of the Earth was more or less similar to today, with both poles frozen and wet tropical weather along the equator, which were bounded by temperate regions.

The supercontinent of Gondwana existed during this period, although it was more of an interconnected mass of continents rather than a single landmass. In the later stages of the Pennsylvanian, the heavy movement between the tectonic plates and the resulting collisions would force the disparate parts of Gondwana to merge and become the true supercontinent of Pangea. These massive geological upheavals brought about catastrophic climate changes, and at the end of the period, much of the dominant wetlands had dried up, and the giant plants characteristic of this period died out.

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