The 3-dimensional anatomy of the North-Western Marsupial Mole (Notoryctes caurinus Thomas 1920) using computed tomography, X-ray and magnetic resonance imaging

Abstract

The 3-D skeletal images obtained from reconstruction of CT scans and X-rays, and soft-tissue images produced by MRI, provide invaluable information of the internal and gross anatomy of the north-western marsupial mole (Notoryetes caurinus). The conical skull, which is quite thin-walled dorsally and anteriorly but strong in the basicranial region, has little evidence of the orbit or zygomatic arch, and the smoothly-curved posterior region has no sagittal or occipital crests. The vertebral column is remarkably strengthened, and in lateral view has an unusual flat-shape. The cervical vertebrae appear to be greatly compressed; 4 or 5 are completely fused (which is unique among marsupials). The thoracic vertebrae are fairly robust with large neural spines. The lumbar vertebrae are distinct, becoming large posteriorly towards the pelvis. The sacral vertebrae are greatly expanded in size and are fused with the pelvis. Particularly in the middle of the tail, the caudal vertebrae are greatly developed, with large transverse processes and chevron bones. The pectoral girdle is very anterior, with the shoulder articulation level with the anterior cervical vertebrae just behind the skull, and low on the side of the body. The humerus is robust, and the radius and ulna are very short. The bones of the pelvis are highly derived, and fused to sacral vertebrae. The epipubic bones are small and not ossified. An ossified patella is present and it has an unusual large triangular keel. The most apparent soft-tissue structure by MRI is a large amount of subcutaneous fat, particularly around the ventral surface of the pelvis but also dorsal to the pelvis and anteriorly around the shoulders. The major muscle groups are visible, but distinction between individual muscles is not possible except for the very large muscles of the thigh, upper arm and base of the tail. The muscles of the tail are strongly developed, more so ventrally than dorsally.