Stages are based on the external and/or internal morphological development of the vertebrate embryo, and are not directly dependent on either age or size. The human embryonic period proper is divided into 23 Carnegie stages. Criteria beyond morphological features include age in days, number of somites present, and embryonic length.
As this staging can be applied to all vertebrates, and most vertebrate embryos develop during the embryonic period in much the same way, we can directly compare the timing of development for different species.
From the table you can see that to reach the end of embryonic development, Carnegie stage 23, can take from as little as 10 days in chickens to nearly 60 days in humans.
Carnegie is the name of a historical US Institute that historically categorised these developmental stages, and continues to study embryology today.
To see the various staging systems for each species look at the Embryo Staging Systems references.
The data in relation to days is only an approximation (an average of the range) due to the variability that occurs in normal developmental. The most common measurement is the crown to rump length (CRL) and the effects of fixation should always be considered when making these measurements.
Species |
Stage |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Days |
20 |
22 |
24 |
28 |
30 |
33 |
36 |
40 |
42 |
44 |
48 |
52 |
54 |
55 |
58 |
|
|
Baboon |
Days |
23 |
25 |
27 |
28 |
29 |
30 |
31 |
33 |
35 |
37 |
39 |
41 |
43 |
45 |
47 |
|
Rhesus Monkey |
Days |
21 |
22 |
25 |
28 |
29 |
30 |
32 |
34 |
36 |
37 |
38 |
40 |
42 |
44 |
46 |
|
Marmoset |
Days |
57 |
60 |
64 |
67 |
74 |
||||||||||
|
Days |
9 |
9.5 |
10 |
10.5 |
11 |
11.5 |
12 |
12.5 |
13 |
13.5 |
14 |
14.5 |
15 |
15.5 |
16 |
|
|
Rat |
Days |
10.5 |
11 |
11.5 |
12 |
12.5 |
13 |
13.5 |
14 |
14.5 |
15 |
15.5 |
16 |
16.5 |
17 |
17.5 |
|
Chinese Hamster |
Days |
10 |
10.5 |
11 |
11.5 |
12 |
12.5 |
13 |
13.5 |
14 |
14.5 |
15 |
15.5 |
16 |
16.5 |
17 |
|
Guinea Pig |
Days |
14.5 |
15 |
15.5 |
17 |
18 |
19 |
20 |
21 |
22 |
23 |
24 |
25 |
26 |
27 |
29 |
|
Rabbit |
Days |
8 |
8.5 |
9.5 |
10.5 |
11 |
12 |
12.5 |
13.5 |
14 |
14.5 |
15.5 |
16 |
16.5 |
17 |
18 |
|
Sheep |
Days |
15 |
16 |
17.5 |
18.5 |
19.5 |
20.5 |
22 |
23 |
24.5 |
25.5 |
27.5 |
29.5 |
30 |
33 |
|
|
Pig |
Days |
14 |
15 |
16 |
17 |
18 |
19 |
20.5 |
21.5 |
23 |
24 |
25.5 |
27.5 |
29 |
30.5 |
32.5 |
|
Days |
1 |
1.5 |
2 |
2.25 |
2.5 |
3 |
3.25 |
3.75 |
4.75 |
5.5 |
6.25 |
7.25 |
7.75 |
8.5 |
10 |
Source: Butler, H. and Juurlink, B.H.J. An atlas for staging mammalian and chick embryos. CRC Press Inc., Florida (1987) and specific references listed below.
O'Rahilly Early human development and the chief source of information on staged human embryos. Eur. J. Obstet. Gynec. Reprod. Biol. 9 p273 (1979)
Hendrickx Embryology of the baboon. University of Chicago Press.
Hendrickx and Sawey Embryology of the rhesus monkey. The Rhesus Monkey, Bourne (ed), Academic Press, NY (1975)
Phillips The embryology of the common marmoset. Adv.
Theiler The house mouse. Springer-Verlag, NY (1972)
Witschi Growth. Altman and Dittmer (ed), Fed. Soc. Exp. Biol., Washington (1962)
Donkelaar Stages in the prenatal development of the chinese hamster. Anat. Embryol. 156 p1 (1979)
Harman and Prickett The development of the external form of the guinea-pig between the ages of 11 and 20 days of gestation. Am. J. Anat. 49 p351 (1932)
Edwards The external development of the rabbit and rat embryo. Advances in teratology, Vol 3, Woollam (ed), Academic Press, NY (1968)
Bryden Embryology of the sheep. J. Morphology 138 p169 (1972)
Marrable The embryonic pig. A chronological account. Pitman Medical, London (1971)
Hamburger and Hamilton A series of normal stages in the development of the chick embryo. J. Morph. 88 p49 (1951)
Butler and Juurlink An atlas for staging mammalian and chick embryos. CRC Press Inc., Florida (1987)
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Our understanding of development relies a great deal on our ability to organise embryonic events into a timed sequence. This means that we can not only understand the order of events but also when they occur.
This is also experimentally useful as comparisons can be then made between embryos of the same species.
This page is a summary of a great deal of work by other embryologists over many years (see references) to stage embryos from different species, and having done so, we can also compare the timing of embryonic development between species.
Note that the day timing for each stage is the average of a range from many embryos, and I have also included a table of the data used to generate the comparison graph.
Please cite the original authors when using this data.
Please email Dr Mark Hill if you wish to make a comment about this current project.