Table 2. The similarity and difference of skin appendages among reptile, bird, mammals and fossils.
| Reptile | Bird | Mammal | Reptile with branching skin appendage and feathered dinosaur |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Tuberculate scale |
Overlapping scale |
Scutate scale |
Reticulate scale |
Feather | Bristle in Turkey beard |
Hair |
Longi- squama |
Psittaco -saurus |
Sinosauro- pteryx |
Sinornitho -saurus |
Micro- Raptor gui |
|
| Placode | ? | ? | + | ? | + | ? | + | ? | ? | ? | ? | ? |
| A-P axis | - | + | + | - | + | ? | + | + | ? | ? | ? | ? |
| P-D axis | - | - | - | - | + | + | + | + | + | + | + | + |
| Follicle | - | - | - | - | + | - | + | - | + | ? | ? | + |
| Mesenchym al core | + | + | + | + | + | + | - | - | ? | ? | ? | ? |
| Cylinder | - | - | - | - | + | + | - | - | +? | +? | +? | ? |
| Simple branching | - | - | - | - | + | + | - | + | - | + | + | + |
| Hierarchical branching | - | - | - | - | + | - | - | - | - | - | + | + |
| L-R asymmetry | - | - | - | - | + | - | - | - | - | - | - | + |
| Regeneration | ? | ? | - | - | + | ? | + | ? | ? | ? | ? | ? |
| α-Keratin | ? | + | + | + | + | ? | + | ? | ? | ? | ? | ? |
| β-Keratin | ? | + | + | - | + | + | - | ? | ? | ? | ? | ? |
-, no; + yes; ? not sure