Tambussi et al. 2005
- Family Spheniscidae
C. unienwillia was the first of the genus to be described, whose remains were recovered from and named after the Late Paleocene Cross Valley Formation on Seymour Island, Antarctica. It measured about 140 cm (4.6 ft).
In August 2019, a new species of Crossvallia, C. waiparensis, was described based off leg bone fossils from Waipara, New Zealand. It measured about 160 cm (5.2 ft) and weighed around 70–80 kg. It is thought to have lived in the Paleocene 66–56 million years ago, and close relatives of C. waiparensis may have lived in the Antarctic. The fossils were discovered in 2019 by amateur palaeontologist Leigh Love. 
- Tambussi, Claudia P.; Reguero, Marcelo A.; Marenssi, Sergio A.; Santillana, Sergio N. (2005). "Crossvallia unienwillia, a new Spheniscidae (Sphenisciformes, Aves) from the Late Paleocene of Antarctica". Geobios. 38 (5): 667–675. doi:10.1016/j.geobios.2004.02.003.
- Cross Valley at Fossilworks.org
- Mayr, Gerald; De Pietri, Vanesa L.; Love, Leigh; Mannering, Al; Scofield, R. Paul (2019). "Leg bones of a new penguin species from the Waipara Greensand add to the diversity of very large-sized Sphenisciformes in the Paleocene of New Zealand". Alcheringa. doi:10.1080/03115518.2019.1641619.
- "Pingvin". Magyar Narancs (in Hungarian). XXXI (34): 7. 2019-08-22. ISSN 1586-0647.
- "Human-sized penguin discovered in Waipara". RNZ. 2019-08-14. Retrieved 2019-08-14.