Table 2 Sequence of chondrification in the chondrocranium of birds and non-avian sauropsids. Chondrocranial characters ordered by anatomical regions. For the sequential stages as originally reported see Table S4, Additional file 4 and Table S5, Additional file 5

acrochordal cartilage

1

1

?

1

1

1

2

1

1

1

2

1

1

1

3

parachordal cartilage

1

1

1

1

1

1

1

1

1

1

4

1

1

1

1

fenestra basicranialis posterior

?

4

?

?

3

–

1

3

–

2

?

3

3

2

3

trabeculae

1

1

2

2

2

2

3

2

2

2

1

1

1

2

1

trabecula communis

3

2

2

3

5

2

3

3

2

2

3

2

3

2

2

otic capsule

4

2

2

2

2

2

3

1

3

3

4

1

2

3

2

fenestra ovalis

6

3

?

6

7

6

4

3

6

4

?

?

4

7

6

metotic cartilage

6

4

?

3

6

2

3

3

4

3

?

–

–

–

–

nasal septum

3

3

3

3

5

3

4

2

2

2

3

3

4

4

3

fenestration of nasal septum

–

5

?

5

8

6

?

5

8

6

–

?

8

10

6

prenasal process

3

3

3

6

5

2

2

3

4

4

?

–

–

–

–

planum antorbitale

4

4

?

5

7

4

4

2

5

3

4

?

5

5

5

parietotectal cartilage

4

4

?

4

6

5

4

3

3

4

4

3

5

7

4

nasal capsule

7

7

?

7

9

6

6

6

7

6

4

?

6

9

5

cupola anterior

7

7

?

7

9

7

6

6

7

6

–

?

6

10

5

concha nasalis

4

4

?

5

7

5

?

?

–

–

4

?

7

?

5

maxilloturbinal

5

5

?

5

8

6

6

5

7

6

?

?

?

?

?

atrioturbinal

7

6

?

5

9

7

6

6

8

6

?

?

?

?

?

interorbital septum

4

2

3

4

6

2

3

2

5

3

4

2

4

2

3

fenestration of interorbital septum

–

7

3

7

8

6

6

4

–

7

?

?

–

8

6

planum supraseptale

5

7

?

?

7

5

5

6

7

?

4

3

4

2

3

pila antotica

2

2

?

1

4

2

2

?

2

2

4

4

4

2

5

tectum synoticum

7

5

4

7

7

7

4

5

7

4

5

5

7

6

5