Biogeographical Migration Patterns

INTRODUCTION

The order Lagomorpha consists of two extant families: Leporidae (hares and rabbits) and Ochotonidae (pikas) and several extinct families. The purpose of this paper is to identify the characterize biogeographical migration patterns of Lagomorphs and why. The natural geographical distribution today of the lagomorphs is found throughout Europe, Asia and North America. Figure 1 is an illustration depicting the various time periods as well as the number of million years ago (Mckenna 1997). The sources identified address the distribution throughout the Eocene to the Pliocene (35-5 Ma) (Figure 11). The aims of this paper are to identify the biogeographical distribution of the various families and how that compares to the modern day distribution.

Some characteristics belonging to the include a fenestrated lacework of bone on the lateral surface of the maxilla, a snout tapering in width anteriorly, a tendency toward reduction of the palatine component of the palate, a present supraorbital process of the frontal bone and the tendency toward the loss of the posterior mental foramen with the cranial characteristics (Dawson 2008). Some postcranial characteristics that differ between the Leporidae and the Ochotonidae include the location of the vertebrarterial canal, the number of thoracolumbar vertebrae, the number of fused sacral vertebrae, the fusion of the pelvis at the pubic symphysis and fusion of the cuneiform to the metatarsal in the Leporidae. The postcranial characteristics between the two of them include evolutionary changes in the skeleton associated with either short bursts of locomotion or rapid, sustained bounding locomotion. When comparing living ochotonoids and leporids, the living ochotonoids are much more homogenous in size and tarsal morphology. Along with the dental identification, these skeletal characteristics aid in the identification of families, genera and species. One of the main defining features of lagomorphs is the calcaneal canal passing diagonally through the talus (if talus is present) (Rose et al. 2008). While it is typically present in both the Ochotonidae and Leporidae, it is

2013).The major changes in the natural environment include the drift and reconnection of continents, the drastic decline of CARBON DIOXIDE (in the late Miocene) and the formation of ice-age climate cycles. The origination of leporids in the Eocene occurred within a warmer and wetter climate. During the transition of Eocene to Oligocene global cooling started to take place while the number of fossil occurrences increased (Ge et al. 2013). Plant fossils from the early to middle Miocene indicate that forests and swamps dominate the vegetation in the northern hemisphere while the low diversity of leporids during this time period may indicate that the vegetation of the time did not promote diversification and dispersal of the Lagomorpha (Ge et al. 2013). However the uplift of the Qinghai Tibet Plateau and the formation of Asian monsoon accelerated the aridity in North America and the CARBON DIOXIDE in the atmosphere. Lagomorphs are likely to be affected by environmental change due to changes in the climate, land use and human disturbance (Leach et al. 2015). They occupy a wide range of environmental conditions in all continents except Antarctica, and are found at extreme elevations (sea level to >5000m) and latitudes (Equator to Arctic) (Leach et al. 2015). Closely related, large-bodied, similarly sized