Cairanoolithusis anoogenusofdinosaur eggwhich is found in Southwestern Europe. The eggs are large (15–19 centimetres or 6–7+1⁄2inches in diameter) and spherical. Their outer surface is either smooth, or covered with a subdued pattern of ridges interspersed with pits and grooves. Multiple fossilegg clutchesare known but the nest structure is unclear.
| Cairanoolithus Temporal range:
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| Cairanoolithus dughii | |
Egg fossil classification
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| Basic shell type: | †Dinosauroid-spherulitic |
| Oofamily: | †Cairanoolithidae Sellés and Galobart,2015 |
| Oogenus: | †Cairanoolithus Vianey-Liaud et al.,1994 |
| Oospecies | |
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| Synonyms | |
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The parent ofCairanoolithusis probably some kind of non-ornithopodornithischian,possibly thenodosauridStruthiosaurus.
The eggs were first named in 1994, when the two oospecies were classified in distinct oogenera asCairanoolithus dughiiandDughioolithus roussetensis.They are now considered to belong in a single oogenus, possibly even a single oospecies. Though it has been classified as amegaloolithid,Cairanoolithusis now placed in its own oofamily, Cairanoolithidae.[1][2]
Description
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Cairanoolithuseggs are spherical and fairly large, measuring15–19 cm (6–7+1⁄2in) in diameter.[2][3]The outer surface is smooth or covered with a subdued netlike pattern of ridges, interspersed with pits and grooves (sagenotuberculate ornamentation).[1][2]The eggshells are made up of partially interlocking column-shaped shell units and range from1.10 to 2.65 mm (3⁄64to13⁄128in) thick.[2]
Several egg clutches ofC. dughiiare known, containing as many as 25 fossilized eggs.[2]Unfortunately,taphonomicalalterations (changes during the fossilization process) make it difficult to determine the original structure of the nest. Cousin (2002) hypothesized thatCairanoolithuseggs were laid on the surface of the ground, possibly buried beneath a mound of plant matter.[4]Tanakaet al.(2015) noted that the shell had a high rate of water vapor conductance. Therefore, they concluded thatCairanoolithusnests were covered by organic or inorganic material, similar to modern eggs with high vapor conductance.[5]
Oospecies
editTwo oospecies ofCairanoolithushave been described:
- Cairanoolithus dughiiis thetypeoospecies. At1.57–2.41 mm (1⁄16–3⁄32in), its eggshell is slightly thicker than that ofC. 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,can be distinguished fromC. dughiiby its thinner eggshell (measuring1.11–1.77 mm or3⁄64–9⁄128in thick), its broader eggshell units, and the relative prominence of its ornamentation.[2]LikeC. dughii,C. roussetensistypically has an angusticanaliculate pore system, though some specimens have prolatocanaliculate pores, meaning they have 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 tointraspecificvariation or due to taphonomy. He also described several eggshell fragments that possibly belong to an additional distinct oospecies ofCairanoolithus;[4]however these specimens were referred toC. roussetensisby Selles and Galobart (2015).[2]
Classification
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| Simplified version of Selles and Galobart's cladogram, showing the position ofCairanoolithusrelative to other non-theropod dinosaur eggs. |
While it was formerly considered amegaloolithid,Cairanoolithusis now considered to belong its ownmonotypicoofamily, Cairanoolithidae. It belongs to the dinosauroid-spherulitic basic type, a group includingsauropodeggs andornithischianeggs, butparaphyleticallyexcludingtheropodeggs.[2]
Thecladistic analysisdone by Selles and Galobart in 2015 recoveredCairanoolithusas a sister taxon to the clade ofornithopodeggsGuegoolithus,Spheroolithus,andOvaloolithus.Therefore, they considered it likely thatCairanoolithusbelongs to a non-ornithopod ornithischian dinosaur.[2]
Parentage
editSince embryos are unknown in cairanoolithid eggs, the identity of their parent is uncertain. They have long been considered to be eggs oftitanosaursor ornithopods (likeRhabdodon).[6][7]However, numerous characteristics distinguishCairanoolithusfrom sauropod eggs (oofamilies Megaloolithidae andFaveoloolithidae), even though they bear superficial similarities in size and shape.Cairanoolithus's columnar eggshell units are quite unlike the fan-shaped ones seen inMegaloolithus,Faveoloolithus,orFusioolithus.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 (SpheroolithidaeandOvaloolithidae), 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. LateCampanianto earlyMaastrichtianornithischians from Southwestern Europe are restricted torhabdodontidsand thenodosauridStruthiosaurus.When Sellés and Galobart analyzed the pelvises ofRhabdodon(the largest known rhabdodontid) andStruthiosaurus,they found thatRhabdodoncould not have laid eggs as big asCairanoolithus.[2]On the other hand, even thoughStruthiosauruswas relatively small, the unique orientation of its ischia would have easily allowed it to lay eggs as large as a19 cm (7+1⁄2in) cairanoolithid egg.[2]However, interpretingCairanoolithusas the eggs of a nodosaur does raise the question of whyCairanoolithusor similar eggs have not been found in areas with a greater nodosaur abundance.[2]
Distribution
editCairanoolithusis native to Southwestern Europe, including southernFranceand northernIberia.Its fossils date to the lateCampanianto earlyMaastrichtian.[2]They are usually found in theAix-en-ProvenceBasin below theRognac Limestone.[2][3]C. dughiiis from the La Cairanne site inBouches du Rhône,France, fromRoquehautes-Grand Creuxand from theVilleveyrac Basin.[3]C. roussetensisis found in the northern part of Iberia (Tremp Groupof Spain),[8]and from southern France (inRousset Village,Roquehautes-Crete du Marbre,the Villeveyrac Basin, andArgelliers-Montamaud).[3][9]
Paleoecology
editThe Late Cretaceous ecosystems of Europe (which was then an island archipelago) show complex mixing of taxa originating from Africa, Asia, and North America.[10]In Southwestern Europe,Cairanoolithusco-occurs with numerous other types of fossil eggs;Megaloolithusis particularly common,[2][3]but theropod eggs such asPrismatoolithus[10]and the ornithopod eggGuegoolithus[11]are also present. Dinosaur body fossils are also common, including nodosaurids, rhabdodontids, titanosaurs,dromaeosaurids,basaliguanodontians,hadrosaurids,neoceratosaurians,andcoelurosaurs.Other vertebrates includebony fish,squamates,cryptodiranturtles,alligatorids,andmammals.[10]
History
editThe Aix Basin was first excavated for fossils in 1869 by French paleontologistPhilippe Matheron.[12]In the 1950s, Raymond Dughi and Francois Sirugue, a pair of French paleontologists working for theMuseum d'Histoire Naturelle Aix-en-Provence,extensively studied the basin's fossil eggshells.[13]They divided the eggs they had found into ten different types, but they did not describe them in detail. In the 1970s and 1980s, further work was done by the French paleontologist[14]P. Kerourio and the German paleontologist[15]H. K. Erben.[3]
In his 1983 doctoral thesis, M. M. Penner devised one of the early classification schemes for egg fossils.[2][16]He was the first to recognize the eggs now namedCairanoolithusas a distinct type; under his classification scheme, they were called "Group 2".[2]In 1994, French paleontologists M. Vianey-Liaud, P. Mallan, O. Buscail and C. Montgelard described them under the modern parataxonomic system asCairanoolithus dughiiand"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-Liaudsynomizedthe two oogenera.[17]In 2002, French paleontologist R. Cousin took a step further and synonymized the two oospecies.[4]
In 2012, the firstCairanoolithusfossils discovered outside of France were first reported byAlbert G. Sellesin hisPhD thesisatUniversitat de Barcelona,in which he also proposed thatCairanoolithusbe moved into its own oofamily.[18]Three years later, Selles andAngel Galobartpublished a comprehensive reanalysis ofCairanoolithus,in which they formally named the new oofamily, Cairanoolithidae, to containCairanaoolithus.Contrary to Cousin's conclusions, Selles and Galobart separated the oospeciesC. dughiiandC. roussetensis.Also, they demonstrated thatCairanoolithuswas not the eggs of an ornithopod or sauropod and conjectured that it could be the eggs of a nodosaur.[2]
References
edit- ^abcdCarpenter, Kenneth (1999).Eggs, Nests, and Baby Dinosaurs: A Look at Dinosaur Reproduction (Life of the Past).Bloomington, Indiana: Indiana University.ISBN978-0253334978.
- ^abcdefghijklmnopqrstuvSellés, A.G.; Galobart, À (2016). "Reassessing the endemic European Upper Cretaceous dinosaur egg Cairanoolithus".Historical Biology.28(5): 583–596.doi:10.1080/08912963.2014.998666.S2CID85205835.
- ^abcdefgM. 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
- ^abcCousin, 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 Société Géologique de Normadie et des Amis du Muséus du Havre(in French).89:1–177.
- ^Tanaka; Zelenitsky, Darla; Therrien, François (2015)."Eggshell Porosity Provides Insight on Evolution of Nesting in Dinosaurs".PLOS ONE.10(11): e0142829.Bibcode:2015PLoSO..1042829T.doi:10.1371/journal.pone.0142829.PMC4659668.PMID26605799.
- ^abKonstantin 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.JSTOR4523773.
- ^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.S2CID86208659.
- ^Sellés, A. G.; Vila, B. (2015). "Re-evaluation of the age of some dinosaur localities from the southern Pyrenees by means of megaloolithid oospecies".Journal of Iberian Geology.41:125–139.
- ^Sellés, A. G.; Bravo, A. M.; Delclòs, X.; Colombo, F.; Martí, X.; Ortega-Blanco, J.; Parellada, C.; 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.doi:10.1016/j.cretres.2012.05.004.
- ^abcTabuce, Rodolphe; Tortosa, Thierry; Vianey-Liaud, Monique; Garcia, Geraldine; Lebrun, Renaud; Godefroit, Pascal; Dutour, Yves; Berton, Severine; Valentin, Xavier; Cheylan, Gilles (2013)."New eutherian mammals from the Late Cretaceous of Aix-en-Provence Basin, south-eastern France".Zoological Journal of the Linnean Society.169(3): 653–672.doi:10.1111/zoj.12074.S2CID82961064.
- ^Moreno-Azanza, M.; Canudo, J.I.; Gasca, J.M. (2014)."Spheroolithid eggshells in the Lower Cretaceous of Europe. Implications for eggshell evolution in ornithischian dinosaurs"(PDF).Cretaceous Research.51:75–87.doi:10.1016/j.cretres.2014.05.017.
- ^Matheron, P. (1869). "Notice sur les reptiles fossiles des dépôts fluvio-lacustres crétacés du bassin à lignite de Fuveau".Mémoires de l'Académie Impériale des Sciences. Belles-Lettres et Arts de Marseille(in French): 345–379.
- ^Taquet, Phillippe (1999).Dinosaur Impressions: Postcards from a Paleontologist [translated from French by Kevin Padian].Cambridge, UK: Cambridge University Press. p. 199.ISBN9780521779302.
- ^Kerourio, Phillippe (1981). "La distribution des" coquilles d'oeufs de dinosauriens multistratifiées "dans le Maestrichtien continental du sud de la France".Geobios(in French).14(4): 533–536.doi:10.1016/s0016-6995(81)80126-x.
- ^Wilford, John Noble (November 9, 1986)."New data extend era of dinosaurs".New York Times.Retrieved22 May2016.
- ^Carpenter, K.; Hirsch, K.F.; Horner, J.R. (1994). "Introduction".Dinosaur Eggs and Babies.Cambridge: Cambridge University Press. pp. 1–11.
- ^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, Série IIA(in French).332(3): 185–191.Bibcode:2001CRASE.332..185G.doi:10.1016/S1251-8050(00)91401-0.
- ^Garcia Sellés, Albert (22 June 2012).Oological record of dinosaurs in South-Central Pyrenees (SW Europe): Parataxonomy, diversity and biostratigraphical implications(Ph.D.).hdl:2445/35482.
