Stockard, C.R., 1907. Observations on the natural history of Polyodon spathula. The American Naturalist, 41(492), pp.753-766.
| Species | Development state | Trait | Primary Data | Secondary Data |
| Polyodon spathula | Egg | Egg size after water-hardening | ~2.70 | 2.7 mm |
| Polyodon spathula | Egg | Egg size after water-hardening | ~2.20 | 2.2 mm |