Characters shared by a group of taxa due to descent from a most recent common ancestor (i.e., synapomorphies) constitute the evidence to support the nested structure of a given cladogram.
These longer n-mers should only be shared between species due to descent from a common ancestor.
The posterior fossa deformity can also be seen: the cisterna magnum is absent and the foramen magnum is enlarged due to the descent of the structures of the posterior fossa toward the spinal canal (arrows in b).
Further, due to the descent of the brain there is distortion and stretching of the veins.
The bones within bat wings, for example, are very similar to those in mice feet and primate hands, due to the descent of all these structures from a common mammalian ancestor.
The epicardial and endocardial borders were outlined during the cardiac cycle in the short-axis slices; then the mitral, tricuspid, aortic, and pulmonary valves planes were tracked, to correct for alteration in volume due to the descent of the atrioventricular ring toward the apex during systole.
This method of unlinking topologies for a priori partitions has precedence in genetic studies that have investigated topological incongruence due to different descent histories of different genes [49], [50], [60] [63].
Due to common descent, the frequencies of SSR motifs in different species are expected to be correlated, and under the assumption of a constant rate of evolution (birth and death) of SSRs, the degree of correlation should decrease with the divergence time between species.
A distinction has to be made between resemblances due to propinquity of descent and those due only to similarity of function.
Their skeletal structure is homologous, due to common descent from the forelimb of a reptilian ancestor; but the modifications for flying are different and independently evolved, and in this respect they are analogous.
