Читать книгу Medicine and Surgery of Camelids - Группа авторов - Страница 18

Camelid evolution began in North America over 40 million years ago during the Eocene epoch [18]. Geologic and paleontologic time scales are estimates and subject to revision. Figure 1.13 provides a diagram of the relationships between the various artiodactylid families since the Eocene epoch. Webb published a definitive work on the evolution of Pleistocene camelids based on paleontologic evidence [20]. He suggested three major tribes, separated as early as the Eocene epoch. This family tree is questionable, with insufficient fossil records to trace lines accurately (postulates indicated by broken lines) (Figure 1.14) [20, 21]. Two tribes, Camelopini (Camelops) and Camelini (Camelus), evolved in North America only west of the Mississippi River. The tribe Lamini (Lama) was also found in Florida [21, 22].

Figure 1.12 Llama.

The Pleistocene epoch was characterized by a series of periods of extreme cold and glaciation in northern North America and Europe [23]. The last glacial retreat occurred about 10 000 years ago, marking the beginning of the recent epoch. It was during the Pleistocene epoch that the Camelidae flourished [24–26]. Many genera in the family Camelidae became extinct, for unknown reasons, before the recent epoch.