In your attachments 'DenseCloud_Classes.JPG' and 'DenseCloud_RGB.JPG' the light colour points are on the top surface of the tail, and the dark points are on the underside, facing the opposite direction - away from you.
If you looked at it from below you would then see that the dark points become lighter, and the light points become dark as you view them from the other side. The dark colour indicates the orientation of the surface that the point corresponds to.
Your attachment illustrates that you do not have many points on the upper surface of the tail, and photoscan can not create a good watertight mesh of an object with only one side available in the dense cloud so it only meshes the parts with data from both sides, as shown in your attachment 'Mesh.JPG'.
So you need to check your images of the upper side of the tail to check overlap with each other and adjacent parts of the object to see why this part is not being reconstructed in the dense cloud. Likely causes are that it is out of focus in some/all images, insufficient images, or it moved during the scan.