Rhinos In Nebraska by Alison Pearce Stevens

Twelve million years ago, in ancient Nebraska, short, round hippos, elephants, three-toed horses, many types of camels and oreodonts roamed the grasslands. But a thousand miles away, unknown to these animals, a supervolcano erupted, spewing rock and ash into the sky. Over the next days and weeks, the ash carried downwind of the eruption continued to fall steadily.

The animals on the ancient Nebraska savanna soon found themselves breathing in the ash as they grazed and walked. Smaller animals such as turtles and birds quickly succumbed as the ash suffocated them. Larger animals like the horses, camels and hippos took much longer to die. We know all this because of the most extraordinary record contained in the Ashfall Fossil Beds.

The Ashfall Fossil Beds were first discovered in 1953, although the area was known for the bones found in a specific spot by farmers for years. That spot was called Bone Hill and it was believed that this was where cattle went to die. That's because any bones found, unlike most fossil bones were not mineralized. Farmers thought that meant they were recent.

Donald Peterson and his father James were hired by a farmer to plant rye in fields near Bone Hill. At the base of Bone Hill, Donald and James discovered the skull of an animal eroding out of the cliff face. They decided to contact University of Nebraska State Museum about their discovery and this led paleontologists Lloyd Tanner and Henry Reider to visit the site. They were able to identify the skull as that of a rhinoceros, which once roamed the Great Plains of North America! Although Tanner and Reider made field notes and noted the location of the skull, which they took back to the museum, their notes were eventually lost.

It wasn't until 1971 that geologists Mike and Jane Voorhies, who were mapping the area, discovered the jawbone of a baby rhinoceros within the ten foot thick layer of volcanic ash. It was known that rhinoceros roamed what is now Nebraska over thirty million years ago. However, fossils were a rare find. When Mike returned the next day to remove the fossil, he discovered the entire skull and saw a vertebrae as well.  Jane did not return to the area because it was covered in poison ivy. (They eventually named it Poison Ivy Quarry.) It would be another six years before Mike returned to Poison Ivy Quarry, this time with a small team of paleontologists to help him. They uncovered the complete skeleton of the baby rhinoceros and more skeletons. Over the next few weeks they removed the skeletons of a dozen rhinos and three horses, taking them to the museum. With the help of John Boellstorff, who worked for the Nebraska Geological Survey, the ash was dated at approximately 10.5 million years, plus or minus 1.5 million years. At this time they did not know the source of the volcanic ash.

The following year, Mike Voorhies again returned with a bulldozer to remove the rock and soil topping the ash layer. Over the next four months, they uncovered fifty-eight rhinos. So began the remarkable discoveries that led Voorhies and other scientists to piece together the catastrophic events that led to what became known as the Ashfall Fossil Beds.

Discussion

Scientist, Alison Pearce Stevens weaves together the fascinating events that paleontologists believe occurred at a watering hole almost 10 million years ago, after the eruption of a supervolcano. Stevens, who has a Ph.D in ecology, evolution and animal behaviour, begins the story with the discovery of rhinoceros bones and then goes on to describe the work of Mike Voorhies as he and other paleontologists, students and interns worked to excavate the Ashfall Fossil Beds.

Along the way, Stevens provides her young readers with information about many different aspects of the research. For example she explains how scientists dated the volcanic ash, how evidence from the skeletal remains of the animals indicated they suffered from Marie's disease and what that suggested about how they may have died.

Paleobotanists were able to use seeds in the ash to determine what the environment was like at the time of the eruption. Evidence from diatoms, tiny plant-like algae that form glass shells, helped paleobiologists determine that the water hole filled during the rainy season and dried up when the rains stopped. The distribution of types of animals who died at the water hole helped scientists determine that grazers like rhinos were more affected by the ash than browsers like deer. Michael Perkins, a geologist at the University of Utah had studied ash beds from Utah and many surrounding states. Mike Voorhies asked Perkins to try to determine where the volcano that produced the ash beds in Nebraska was located. 

Stevens shows her readers the many facets of paleontological and geological research and how geologists can piece together an event based on the information fossils, rocks and other features provide. The explanations are simple and easy to understand. There are the black and white illustrations by Matt Huynh as well as some black and white photographs of the Ashfall beds excavated over the years and housed in a special building constructed to protect them.

Budding geologists and those interested in earth history will enjoy this well written, engaging and informative book about a unique event in North American geologic and natural history. Stevens has included a Glossary, Author's Note and an Index at the back of the book.

Further information may be found at:

Rhino Resource Center's copy of Mike Voorhies 1978 paper, A Miocene Rhinoceros Herd Buried in Volcanic Ash which can be found at: https://www.rhinoresourcecenter.com/pdf_files/137/1378684580.pdf

Alison Pearce Stevens article from Science New for Students, Rhinos, Camels and Bone-Crushing Dogs Once Roamed Nebraska: https://www.snexplores.org/article/rhinos-camels-and-bone-crushing-dogs-once-roamed-nebraska

Book Details:

Rhinos In Nebraska by Alison Pearce Stevens
New York: Henry Holt and Company        2021
135 pp.

The Age of Dinosaurs by Steve Brusatte

The Age of Dinosaurs tells the fascinating story of how scientists believe dinosaurs came to be the dominant species on Earth for over 150 million years. Their story covers the Mesozoic Era which includes the Triassic, Jurassic and Cretaceous Periods from 250 million to 66 million years ago.

The story begins in the early Triassic when there was one land mass, a supercontinent called Pangea. To understand this story this first chapter gives a short explanation of fossils and the importance of the rocks they are found in and how they can tell scientists about life long ago. A brief overview of the Earth's history is given up to the end of the Permian when great changes led to a mass extinction. Brusatte's visit to Poland to investigate the tracks of an animal called Prorotodactylus and his research there set the stage for the opening chapter title The Ancestors of Dinosaurs. Based on the tracks, paleontologists believe that this animal was an archosaur, a type of reptile that survived the Permian extinction and was a forerunner of the dinosaurs. The archosaurs were divided into two branches: one group which includes crocodiles and their extinct cousins and a second group which includes the dinosaurs.

In the early Triassic dinosaurs were not yet dominant but we know they existed from fossil evidence from the area of Pangea that is now Argentina.  They were rare throughout the rest of Pangea, likely restricted to the Argentina area of Pangea which was located south of the equator, an area cooler, wetter and more humid. Dinosaurs at this time included both meat-eaters and plant-eaters.  Instead, huge amphibians, called super salamanders dominated the waters, while thousands of species of crocodiles ruled the land.

Dinosaurs began to dominate in the Jurassic. At the end of the Triassic, the supercontinent of Pangea began to break apart. Increased volcanic activity resulted in climate change and another extinction however it was not a large as the previous Permian extinction but it was significant enough. "Many of the animals that ruled the Triassic world went extinct." This included most of the crocodile species and super salamanders. The dinosaurs survived, something that is not fully understood.

The first 30 millions years of the Jurassic Period saw dinosaurs evolve into many new species. This diversification continued throughout the Jurassic with different species inhabiting a wide range of ecosystems from the poles to the equator. Some examples of this diversity could be seen in the ornithischian dinosaurs which are plant eating dinosaurs. These dinosaurs had beaks and included stegosaurs with back plates and ankylosaurs with spiked armour. By mid-Jurassic (170 million years ago) dinosaurs were dominant, "...the most important animals in ecosystems all over the planet." 

Another group of dinosaurs, the Sauropods, were the largest animals to live on land. Sauropods, which were plant eaters, were found all over the world. The dominant predator was Allosaurus which lived in North America, Europe and possibly Africa.

The transition to the Cretaceous was much calmer with the continents continuing to move further apart, continuing climate changes, changes to sea level and the formation of islands and land bridges that allowed dinosaurs to migrate. These factors all influenced the evolution of dinosaurs. The sauropods declined but those that remained became enormous. They were the titanosaurs and were truly colossal, at more than one hundred feet long and weighing over seventy tons. Velociraptors were a new type of predator in the Cretaceous as were the carcharodontosaurs, a huge carnivore. But these were soon to be replaced by the tyranosaurs and the most famous of them all was Tyrannosaurus Rex.

From this point on, Brusatte goes on to detail the evolution of the tyrannosaurs, as well as the types of dinosaurs that dominated the various regions of the Earth (North America, Asia, the South and Europe) during the peak of their reign in the Cretaceous. There are also chapters which explain how paleontologists believe dinosaurs evolved into birds, as well as what scientists believe ended the reign of the dinosaurs.

Discussion

The Age of Dinosaurs is a book for the young dinosaur enthusiast. Brusatte, a paleontologist at the University of Edinburgh takes his readers through time beginning with the ancestors of the dinosaurs, to their rise as the dominant life form on our planet and to their sudden demise. The Age of Dinosaurs was inspired by Brusatte's book, The Rise and Fall of the Dinosaurs which was published in 2018 for adult readers. As Brusatte notes in this current edition for younger readers, "It is the story of dinosaur evolution: how dinosaurs changed over time as their world changed around them." Brusatte pieces together the story as we currently understand it, in an exciting, engaging way for young readers.

There is plenty of information about many geologic concepts in The Age of Dinosaurs including explanations about fossils, how dinosaur species are identified, the use radioisotope dating, and plate tectonics. Brusatte spends some time explaining where specific types of dinosaurs were found, for example tyrannosaurs were located mainly in the western United States and Canada and explains how the Earth's changing landmass over millions of years, influenced where certain species of dinosaurs lived. However, one drawback to this book is the lack of maps to help young readers visualize the changing Earth through the Jurassic and Cretaceous. For example maps showing Pangea separating into Gondwana, its gradual break up into the continents we see today would have been helpful. 

There are "boxes" that highlight information about the research paleontologists are undertaking to learn more about dinosaurs. The book opens with a lovely pencil illustration on the title page of a dinosaur scene. Brusatte includes a detailed timeline and a dinosaur lineage chart that readers can refer to as they read the book. In the back, there is a Further Reading section, a Glossary and an Index.  Overall, this is a fantastic book, very informative, easy to read and chock full of interesting facts about dinosaurs that is sure to please older readers who might be interested in learning more about the subject. It may even inspire a future paleontologist or two!

Book Details:

The Age of Dinosaurs: The Rise and Fall of the World's Most Remarkable Animals by Steve Brusatte
New York: Quill Tree Books       2021
249 pp.