The diagram you produced on Page 4 of Cladistics: OG E B A D C -- black eye -- long wing -- wide neck -- long leg -- dark body -- large eye -- thick leg -- wide body The differences in the in-group are explained in 10 steps! Comma separation at one step might be clearer! -- wide wing -- long stinger Your cladogram uses numbered traits… I am doing it this way for a reason…

This diagram is based on the same clade critter data… But is not the result of cladistic analysis: OG E B A D C 25 Steps!! <-- black eye <-- long leg <-- dark body <-- wide neck <-- thick leg <-- wide body <-- long wing <-- large eye <-- wide wing <-- long stinger What concept was used to make this diagram? Scientists reject this diagram because of parsimony…why?

This is likely your cladogram from Page 4 of Cladistics OG E B A D C -- black eye -- long wing -- wide neck -- long leg -- dark body -- large eye -- thick leg -- wide body -- wide wing -- long stinger

What do we do with the newly-discovered Clade Critter (page 5)? OG E B A D C -- black eye -- long wing -- wide neck -- long leg -- dark body -- large eye -- thick leg -- wide body F -- wide wing -- long stinger

Is it easier to evolve or to lose a characteristic? There are two possible explanations— which is most parsimonious? OG F B A D C -- dark bodyR -- black eye dark -- body -- long wing Two Forward Evolutions -- wide neck -- dark bodyR -- long leg -- dark body -- large eye A homoplasy of parallelism or… convergence -- thick leg -- wide body A single evolution But two reversals -- dark body F -- wide wing -- long stinger Is it easier to evolve or to lose a characteristic?

Reversal Homoplasy The Case of Tetrapods

Reptiles are a grade (are paraphyletic) Vertebrate Clade Homeothermy (a homoplasy) Homeotherms are polyphyletic Reptiles are a grade (are paraphyletic) http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/V/VertebrateClade.gif

Tetrapod limbs are complex Ball joint at girdle (pectoral or pelvic) Proximal segment has one heavy bone Hinge joint at elbow or knee Distal segment has two bones for rotation of hand/foot Small cuboidal bones at wrist and ankle for flexibility of hand/foot position Long metacarpal/metatarsals for palm/instep Phalanges for the digits (fingers/toes)

Tetrapod limbs are stereotypical The complex structures are shared among these tetrapods: Amphibians Reptiles Birds Mammals Conclusion: rather than evolving complex limb form and function separately and identically among all these groups of species (i.e., many homoplasies), the tetrapod leg design evolved just once in a common ancestor (i.e., more parsimonious)

Reversal of a complex trait is comparatively parsimonious Forward evolution of a leg requires modification of: Bones Muscles Connectives Vascular Paths Neural Paths Reversal of a complex trait is comparatively parsimonious Reversal could be just ONE point mutation in ONE gene that normally puts limb development into motion. Without the first step, the rest does not happen.

Tetrapod evolution has been reversed multiple times! Thus, it must be easily done… i.e. is parsimonious Legless amphibians: caecilians Legless lizards: glass lizards Ajolote: mole lizards Snakes So some gene functioning early in tetrapod development can mutate (become defective), rendering some ancestral species (and its descendants) legless. All the rest of the tetrapod genes that had evolved to make the limbs, are made useless by this one mutation.

terrestrial amphibians Caecilians: terrestrial amphibians http://www.wildherps.com/images/herps/standard/017614_caecilian.jpg http://www.wildherps.com/images/herps/standard/017612_caecilian.jpg http://scienceblogs.com/zooillogix/caecilian.bmp

A photo of parent Caecilian with offspring R635RmqosDI/AAAAAAAANYc/jwcNDv1suD4/flesh+eating+amphibian+caecilians%5B2%5D

http://www. unexplained-mysteries http://www.unexplained-mysteries.com/gallery/albums/userpics/22445/normal_ajolote.jpg This ajolote is a snake that reversed the reversal blocking only pectoral limbs (note: belly scale pattern and limb location) Or it is a lizard that has lost only its pelvic limbs (reversal homoplasy)

There are also partial losses: the Boa has vestigial pelvic limbs http://www.edwardtbabinski.us/images/spurs1.jpg Of course the alternative interpretation is a partial reversal of loss

There are several clear examples of reversals of reversals: http://dakotabirding.com/Snake_wlegs.jpg This snake has reversed the reversal blocking pectoral limbs

This is another verified reversal of a reversal: http://www.telegraph.co.uk/earth/wildlife/6187320/Snake-with-foot-found-in-China.html This snake has reversed the reversal blocking pelvic limbs

Of course humans will make false claims! This claim of pectoral limbs is clearly false: http://robandjan.files.wordpress.com/2008/08/snake1.jpg This snake is in the act of swallowing a frog, NOT sprouting legs!

Is dark body a complex characteristic? There are two possible explanations— which is most parsimonious? OG F B A D C -- dark bodyR -- black eye dark -- body -- long wing Two Forward Evolutions -- wide neck -- dark bodyR -- long leg -- dark body -- large eye A homoplasy of parallelism or… convergence -- heavy leg -- wide body A single evolution But two reversals F -- dark body -- wide wing -- long tail Is dark body a complex characteristic? Maybe one enzyme!