Table 1. Comparison of 7 developmental stages inside the egg case from S. stellaris and S. canicula.

7 developmental stages	34 stages of S. canicula, Ballard et al. 1993	Key features of each stage	Age S. stellaris (week)	Age S. canicula (week)	Body length S. stellaris (cm)	Body length S. canicula (cm)	Length range S. stellaris (cm)	Length range S. canicula (cm)	Yolk consumption S. stellaris (%)	Yolk consumption S. canicula (%)
1	4–16	No visible embryo	0	0	-	-	-	-	0%	0%
2	17–18	Embryo early formed	3	3	0.62 ± 0.2	0.47 ± 0.11	0.31–0.98	0.29–0.82	0%	0%
3	19–27	Long tail developed	4	4.25 ± 0.46	1.17 ± 0.16	1.1 ± 0.09	0.97–3.39	0.96–2.09	0%	0%
4	28–32	External gill filaments developed	8.13 ± 0.99	7 ± 0.53	3.64 ± 0.28	2.47 ± 0.21	3.24–8.32	2.18–5.75	< 28.05 ± 9.03%	< 22.21 ± 5.42%
5	33	External gill filaments shrunk	15.63 ± 1.19	14.13 ± 0.64	7.57 ± 0.77	6 ± 0.67	6.37–10.26	5.23–8.78	< 38.79 ± 9.37%	< 34.22 ± 7.23%
6	33	Fin-folds absent	19.25 ± 0.71	16.25 ± 0.46	10.84 ± 1.22	7.85 ± 0.91	8.84–17.02	6.44–10.63	< 98.79 ± 1.05%	< 98.35 ± 0.89%
7	34	Fully consumed external yolk	27 ± 0.93	21.38 ± 0.74	16.39 ± 0.93	10.3 ± 0.42	14.48–17.72	9.78–12.31	≈ 100%	100%

Key features are shown for each species developing inside the egg case. Data for both species (S. stellaris and S. canicula) are from this study (n = 8 for each species). The 34 stages of Scyliorhinus canicula (Ballard et al. 1993) was used to compare the detailed embryological staging to our non-invasive 7 developmental stages.