Notice that the charts for basal Paraves and Rhamphorhynchus are very similar.
This is what you would expect if basal Paraves descended from Rhamphorhynchidae.
This is what you would expect if basal Paraves descended from Rhamphorhynchidae.
Figure 3. Representative aerodynamic measurements for pitching stability and control effectiveness. Long-tailed taxa (a) have a stable equilibrium point at 10-25 (yellow line) and the tail is effective in generating pitching moments at low angles of attack (pale yellow box indicates measurable moments for given tail deflections). In short-tailed taxa (b), including extant Larus, the equilibrium point at 0-5 is unstable (red line) and the tail control effectiveness is reduced (no measurable moments for the given tail deflections). One example (Rhamphorhynchus) drawn from pterosaurs illustrates similar possibilities in a phylogenetically distant [actually quite close] taxon.
NOT CONVERGENCE
This is not convergence because ground-based dinosaurs and pterosaurs did not live in similar ways and/or similar environment, and so did not face the same environmental factors.
http://en.wikipedia.org/wiki/Convergent_evolution
In morphology, analogous traits will often arise where different species live in similar ways and/or similar environment, and so face the same environmental factors. When occupying similar ecological niches (that is, a distinctive way of life) similar problems lead to similar solutions.[4]
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