Comparative craniometric study of fat sand rat [Psammomys obesus] and four toed jerboa [Allactaga tetradactyla] live in the similar habitats

ABSTRACT

The present study deals with the skull structure in two species of rodents, namely Psammomys obesus, the common name is Fat Sand rat, and Allactaga tetradactyla, the common name is four toed jerboa that lives in the same habitat. The skulls of Psammomys obesus and Allactaga tetradactyla are studied. The skull of Psammomys obesus, is triangular, strongly ridged and the sutures between its components are fairly apparent. It has two large parietals which are quadrate in shape. The frontal bone have triangular shape. The squamosal bone is triangular in shape. The zygomatic arch is slender and weak. The tympanic bullae are greatly expanded and the external auditory meatus is swollen. It has irregular shaped sphenoid bone consists of two unfused parts, presphenoid and basisphenoid. The occipital bone encloses the foramen magnum which is guarded laterally by two smooth articular occipital condyles. Exoccipital is broad. The mandible of Psammomys obesus consists of right and left halves firmly united in life at the mandibular symphysis. The body of the mandible can be divided into two parts, one bears the incisor teeth and the other contains the molar teeth. However, the cranium in Allactaga tetradactyla is broadly flattened in shape and the sutures between its component bones are apparent. It has two large parietals and the interparietal is narrow and triangular in shape. The frontal bones are flattened. On each side of the cranium, the squamosal which lies between the tympanic bullae and orbit. Supraoccipital is large, the zygomatic arch is slender, weak and consists of two parts, the zygomatic process of maxilla and zygomatic process of temporal. The nasal bones are elongated. The maxillary bone is irregular in shape. The tympanic bulla, exoccipital and paraoccipital process are short