The Horse – Head, Dentition and Limbs Anatomy and Evolution

About this book

Nikos Solounias ist deeply involved with horses and their ancient relatives of times long past. For several decades he ventured out into the world to learn everything he can about the history of the equids. His approach to in-depth examination of the modern horse and constant comparison with palaeontologic findings afford him rare insights into anatomy and function. This book focuses on three remarkable discoveries in the head, the dentition and the limbs of the modern horse.

In the equine head, the interaction of the nasal cavity, the nostrils but especially of the pre­orbital fossa and the nasal diverticulum are examined in detail. This not only allows new insights into the abilities and functions of the nose but also gives insights into the evolution of the anatomy of the equid face. Looking at horse dentition, the interaction between the teeth and the vegetation while chewing provides new insights that explain the structure of the teeth. Additionally, new theories about hypsodonty (high-crowned teeth) give further insight into the anatomy and evolution of the teeth. The author's research on the lower limbs of the horse provides the perhaps most striking results. Investigations of embryos and palaeontologic finds support the novel five-digit scenario of the meta­carpals and metatarsals. This reveals misunderstandings and new ideas about monodactyly.

Contents

Preface   6
Introduction   7

The nasal cavity and the anatomy of the preorbital area   9
The nasal cavity   13
The preorbital fossa of the horse   24
The air sacs of the horse   34
Paleontology   37
Merychippus insignis   38
Merchippus (Lakobatipus) sp.   42
Cremahipparion proboscideum   47
Embryology   56
Comparative species   64
The lowland tapir – Tapirus terrestris and Tapirus indicus Malayan tapir   64
The white-tailed deer – Odocoileus virginianus   67
Sound production in the Cetacea and similarities to the horse   69
The Indian elephant – Elephas maximus   70
The cotton tail rabbit – Sylvilagus sp.   72
Probable developmental functions for the preorbital fossae   74
Conclusion   79

The dentition – mastication and tooth wear   85
A short introduction to horse dentition   85
The anatomy of the Equus hypsodont teeth   89
Mastication and the anatomy of tooth wear   98
Motion of the jaw and some forces of mastication   100
The misunderstood lower dentition – a remarkable mutation   103
Cementum wear   106
Tooth mesowear in equids   109

The anatomy and embryology of the forelimb and feet   111
Brief osteological anatomy   114
The histology of the horse hoof   116
Evolution   121
The horse anatomy   126
Conclusion   128

References   129
Acknowledgments   132

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Biography

Nikos Solounias was born in Greece. He is a professor of anatomy and embryology at the New York Institute of Technology and a Research Associate in Palaeontology at the American Museum of Natural History. He has published 143 scientific peer-reviewed articles, and three books: Anatomy and Evolution of the Giraffe, Human Head and Neck Embryology and Placing Samotherium in Its Place.

His most important contributions are the study of the Miocene Samos fauna, the development of tooth micro wear, the dietary evolution of horses through the Cenozoic, the explanation as to why some herbi­vores have tall (hypsodont) teeth and the discovery that the ruminants also have five digits in their foot.