Trigonoolithusis anoogenusofdinosaur egg,representing a basalprismatoolithid.Its eggshell, like avian eggs, is composed of three structural layers, but cladistic analysis suggests that its parent was a non-aviantheropod.[1]
| Trigonoolithus Temporal range:
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|---|---|
Egg fossil classification
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| Basic shell type: | †Dinosauroid-prismatic |
| Oofamily: | †Prismatoolithidae |
| Oogenus: | †Trigonoolithus Moreno-Azanzaet al.,2014 |
| Oospecies | |
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History
editFossil eggshells now assigned toTrigonoolithuswere first discovered in2009by Miguel Moreno-Azanza, José Manuel Gasca, and José Ignacio Canudo, three paleontologists fromUniversidad de Zaragoza.[2]They recognized that the fossils represented a new oogenus of prismatoolithids, but the description would not be completed until2014,when they published a description of the new oogenus and oospeciesTrigonoolithus amoaein the paleontology journalActa Palaeontologica Polonica.[1]
Distribution
editFossils ofTrigonoolithusare found in abundance at the La Cantera site of theBlesa FormationinTeruel, Spain.This site is dated to the earlyBarremianage.[1]
Description
editTrigonoolithusis known from numerous eggshell fragments, but no complete or near-complete eggs. The whole egg ofT. amoaewas probably highly elongated, similar to other prismatoolithids. The shell fragments vary between 330 and 1040 μm in thickness, including the prominent triangular protuberances ornamenting their outer surface.[1]
Its eggshell is made up of three structural layers, with gradual boundaries between them. The middle layer, known as the prismatic layer, has a squamatic texture and the prismatic structure characteristic of Prismatoolithidae. It is three to four times thicker than the innermost layer (the mammillary layer), and two to three times thicker than the external layer.[1]
Circular pores 10 μm in diameter cut throughTrigonoolithus's shell to allow for gas exchange. They are angusticanaliculate (meaning the pores are long, straight, and narrow), similar to the pore systems ofPrismatoolithus,Sankofa,andProtoceratopsidovum.[1][3]
Parataxonomy
editTrigonoolithusis classified in the oofamily Prismatoolithidae, alongsidePreprismatoolithus,Prismatoolithus,Protoceratopsidovum,Sankofa,andSpheruprismatoolithus.[1]
Moreno-Azanzaet al.performed multiplecladistic analysesto determine the phylogenetic position ofTrigonoolithus.Because no completeTrigonoolithuseggs are known, its position was slightly unstable, butTrigonoolithuswas consistently placed as thebasalmostmember of Prismatoolithidae, or in apolytomywith other non-aviantheropodsandbirds.[1]
Paleobiology
editPrismatoolithids were previously hypothesized to be eggs ofhypsilophodontsorceratopsians,but later research found that they in fact are the eggs of theropods, based on analysis of preserved embryos ofPrismatoolithus leviswhich showed them to beTroodon formosus.Therefore,Trigonoolithuswas also probably laid by a theropod. Based on its phylogenetic position, Moreno-Azanzaet al.concluded it was most likely a non-dromaeosaurian, non-oviraptorid coelurosaur theropod dinosaur. Of the theropods found at La Cantalera (so far represented only by teeth), onlyaff.Paronychodonsp.and an indeterminatemaniraptoranare possible parents ofTrigonoolithus.[1]
References
edit- ^abcdefghiMoreno-Azanza, M.; Canudo, J.I.; Gasca, J.M. (2014)."Unusual theropod eggshells from the Early Cretaceous Blesa Formation of the Iberian Range, Spain"(PDF).Acta Palaeontologica Polonica.59(4): 843–854.
- ^Moreno-Azanza, M., Gasca, J.M., and Canudo, J.I. (2009).A high-diversity egg shell locality from the Hauterivian–Barremian transition of the Iberia Peninsula.Journal of Vertebrate Paleontology29 (Supplement to No. 3): 151A.
- ^Carpenter, K. (1999). Eggs, Nests, and Baby Dinosaurs: A Look at Dinosaur Reproduction (Life of the Past). Indiana University Press, Bloomington, Indiana.