Cairanoolithus
| Cairanoolithus Temporal range: Late Cretaceous | |
|---|---|
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| Cairanoolithus dughii | |
Eggshell classification  | |
| Basic shell type: | †Dinosauroid-spherulitic |
| Oofamily: | †Cairanoolithidae |
| Oogenus: | †Cairanoolithus |
| Oospecies | |
| Synonyms | |
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Cairanoolithus is an oogenus of dinosaur egg which is found in Southwestern Europe. They are large, spherical eggs that most likely were laid by some kind of non-ornithopod ornithischian, possibly Struthiosaurus. Cairanoolithus is the only member of the oofamily Cairanoolithidae.[1][2]
Distribution
Cairanoolithus is native to the late Campanian to early Maastrichtian of Southwestern Europe, including southern France and northern Iberia.[2] They are found in the Aix-en-Provence Basin below the Rognac Limestone.[2][3] C. dughii is from the La Caraine site in Bouches du Rhône, France, from Roquehautes-Grand Creux and from the Villeveyrac Basin.[3] C. roussetensis is native to Rousset Village, Roquehautes-Crete du Marbre, Villeveyrac Basin, and Argelliers-Montamaud.[3]
History
The Aix Basin was first excavated for fossils in 1869 by French paleontologist Philippe Matheron.[4] In the 1950s, Dughi and Sirugue worked on the basin studying fossil eggshells. They divided the eggs they had found into ten different types, but they did not describe them in detail. In the 70s and 80s, further work was done by Kerourio and Erben.[3]
Cairanoolithus eggs were described as a distinct type by M. M. Penner in his 1983 doctoral thesis.[2] Penner was working prior to the advent of the modern classification scheme for fossil eggs,[5] and called Cairanoolithus eggs "Group 2".[2] In 1994, French paleontologists M. Vianey-Liaud, P. Mallan., O. Buscail and C. Montgelard described them under the modern parataxonomic system as Cairanoolithus dughii and "Dughioolithus" roussetensis.[3] They did not assign either of them to any oofamily, but both oogenera were classified in the oofamily Megaloolithidae by the Russian paleontologist Konstantin Mikhailov in 1996.[6] Following further discoveries in 2001, Géraldine Garcia and Monique Vianey-Liaud synomized the two oogenera.[7] In 2002, French paleontologist R. Cousin took a step further and synonymized the two oospecies.[8]
In 2012, the first Cairanoolithus fossils discovered outside of France were first reported by Albert G. Selles in his PhD thesis at Universitat de Barcelona, in which he also proposed that Cairanoolithus be moved into its own oofamily.[9] Three years later, Selles and Angel Galobert published a comprehensive reanalysis of Cairanoolithus, in which they formally named the new oofamily, Cairanoolithidae, to contain Cairanaoolithus. Unlike previous authors, they hypothesized that Cairanoolithus was laid by a nodosaur. Contrary to Cousin's conclusions, Selles and Galobert separated the oospecies C. dughii and C. roussetensis.[2]
Description
Cairanoolithus eggs are spherical and fairly large, measuring 15–19 cm (5.9–7.5 in) in diameter.[2][3] The outer surface is smooth or bearing a slight sagenotuberculate ornamentation,[2] i.e. the eggshell is covered with a netlike pattern of ridges, interspersed with pits and grooves.[1] Their eggshells range from 1.10 mm to 2.65 mm thick, and is made up of partially interlocking column-shaped shell units.[2]
Oospecies
Two oospecies of Cairanoolithus have been described:
- Cairanoolithus dughii, the type oospecies, is known from the Late Campanian of Southern France. At 1.57-2.41 mm, its eggshell is slightly thicker than that of C. roussetensis. It has slender, partially fused columnar eggshell units. Their outer surface is almost without ornamentation, and the inner surface is covered with hollows once filled by organic cores. C. dughii's eggshell exhibits an angusticanaliculate pore system, i.e. its pores are long, narrow, and straight.[1][2]
- Cairanoolithus roussetensis, which was formerly classified in its own oogenus, Dughioolithus, is found in the Late Campanian of Southern France and in Iberia.[10] It can be distinguished from C. dughii by its thinner eggshell (measuring 1.11 to 1.77 mm thick), its broader eggshell units, and the relative prominence of its ornamentation.[2] Like C. dughii, C. roussetensis typically has an angusticanaliculate pore system, though some specimens have prolatocanaliculate pores (meaning they variable diameter across their length).[1][2]
Some authors consider the two oospecies to be synonymous. Cousin (2002) argued that the differences between them were due to intraspecific variation or due to taphonomy. He also described several eggshell fragments that possibly belong to an additional distinct oospecies of Cairanoolithus.[8]
Classification
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| Simplified version of Selles and Galobert's cladogram, showing the position of Cairanoolithus relative to other non-theropod dinosaur eggs. |
While it was formerly considered a megaloolithid, Cairanoolithus is now considered to belong its own oofamily, Cairanoolithidae. It belongs to the dinosauroid spherulitic basic type, a paraphyletic grouping including sauropod eggs and ornithischian eggs.[2]
The cladistic analysis done by Selles and Galobert in 2015 recovered Cairanoolithus as a sister taxon to the clade of ornithopod eggs Guegoolithus, Spheroolithus, and Ovaloolithus. Therefore, they considered it likely that Cairanoolithus is a non-ornithopod ornithischian.[2]
Parentage
Since embryos are unknown in cairanoolithid eggs, the identity of their parent is uncertain. They have long been considered to be eggs of titanosaurs or ornithopods (like Rhabdodon).[6][11] However, numerous characteristics separate Cairanoolithus from sauropod eggs (oofamilies Megaloolithidae and Faveoloolithidae), even though they bear superficial similarities in size and shape. Cairanoolithus's columnar eggshell units are quite unlike the fan-shaped ones seen in Megaloolithus, Faveoloolithus, or Fusioolithus. Also, its subdued ornamentation contrasts strongly with the heavily sculpted eggshells of sauropod eggs, and it has a different pore system.[2] Eggs of ornithopods (Spheroolithidae and Ovaloolithidae), on the other hand, show much closer similarity to cairanoolithids in ornamentation and pore system. However, ornithopod eggs are typically much smaller, and the crystal structure of their eggshell units is distinct.[2]
The cladistic analysis by Sellés and Galobart in 2015 supported an ornithischian parentage. Late Cretaceous ornithischians from Southwestern Europe are restricted to rhabdodontids and the nodosaurid Struthiosaurus.When Sellés and Galobart analyzed the pelvises of Rhabdodon (the largest known rhabdodontid) and Struthiosaurus, they found that Rhabdodon could not have laid eggs as big as Cairanoolithus. On the other hand, even though Struthiosaurus was relatively small, the unique orientation of its ischia would have easily allowed it to lay eggs as large as a 19 cm (7.5 in) cairanoolithid egg.[2] Interpreting Cairanoolithus as nodosauruid eggs, however, does raise the question of why Cairanoolithus is not found in regions with a greater nodosaurid abundance.[2]
References
- 1 2 3 4 Carpenter, K. 1999. Eggs, Nests, and Baby Dinosaurs: A Look at Dinosaur Reproduction (Life of the Past). Indiana University Press, Bloomington, Indiana.
- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Sellés, A. G., & Galobart, À. (2015). Reassessing the endemic European Upper Cretaceous dinosaur egg Cairanoolithus. Historical Biology, (ahead-of-print), 1-14.
- 1 2 3 4 5 6 M. Vianey-Liaud, P. Mallan, O. Buscail and C. Montgelard. (1994) "Review of French dinosaur eggshells: morphology, structure, mineral, and organic composition." Dinosaur Eggs and Babies, Cambridge University Press, Cambridge. pp 151-183
- ↑ Matheron. P. 1869. Notice sur les reptiles fossiles des depots Huvio-lacustres cretaces du bassin rt lignite de Fuveau. Memoires de I'Academie Imperiale des Sctences. Belles-uttres et Arts de Marseille 1869: 345-19.
- ↑ Carpenter, K., K.F. Hirsch, and J.R. Horner. "Introduction" Dinosaur Eggs and Babies, Cambridge University Press, Cambridge. pp 1-11
- 1 2 Konstantin E. Mikhailov, Emily S. Bray & Karl E. Hirsch (1996). "Parataxonomy of fossil egg remains (Veterovata): basic principles and applications". Journal of Vertebrate Paleontology 16 (4): 763–769. doi:10.1080/02724634.1996.10011364. JSTOR 4523773.
- ↑ Garcia, Géraldine; Vianey-Liaud, Monique (2001). "Nouvelles données sur les coquilles d'œufs de dinosaures Megaloolithidae du Sud de la France : systématique et variabilité intraspécifique [New data on the dinosaur eggshell Megaloolithidae from southern France: systematic and intraspecific variability]". Comptes Rendus de l'Académie des Sciences - Series IIA - Earth and Planetary Science 332 (3): 185–191. doi:10.1016/S1251-8050(00)91401-0.
- 1 2 Cousin R. (2002) Organisation des postes de dinosauriens de la paralamille des Megaloolithidae Zhao, 1979 [Organization of the dinosaur nest of the parafamily Megaloolithidae Zhao 1979]. Bulletin trimestriel de la Socie´te´ ge´ologique de Normandie et des Amis du Muse´us du Havre. 89:177.
- ↑ Selles, Albert G. (2012). Oological Record of Dinosaurs in South-Central Pyrenees (SW Europe): Parataxonomy, diversity and biostratigraphical implications (Ph.D.). Universitat de Barcelona.
- ↑ Sellés, A. G., Bravo, A. M., Delclòs, X., Colombo, F., Martí, X., Ortega-Blanco, J., Parellada, C., and Galobart, À. (2013). "Dinosaur eggs in the Upper Cretaceous of the Coll de Nargó area, Lleida Province, south-central Pyrenees, Spain: Oodiversity, biostratigraphy and their implications." Cretaceous Research, 40, 10-20.
- ↑ Vianey-Liaud, Monique; Khosla, Ashu; Garcia, Geraldine (2003). "Relationships between European and Indian dinosaur eggs and eggshells of the oofamily Megaloolithidae". Journal of Vertebrate Paleontology 23 (3): 575–585. doi:10.1671/0272-4634(2003)023[0575:RBEAID]2.0.CO;2.