Trigonoolithus

Trigonoolithus; Temporal range: Lower Cretaceous PreꞒ Ꞓ O S D C P T J K Pg N
Egg fossil classification
Basic shell type:	†Dinosauroid-prismatic
Oofamily:	†Prismatoolithidae
Oogenus:	†Trigonoolithus; Moreno-Azanza et al., 2014
Oospecies
	Trigonoolithus amoae Moreno-Azanza et al. 2014;

Trigonoolithus is an

theropod.^[1]

History

Fossil eggshells now assigned to Trigonoolithus were first discovered in

Universidad de Zaragoza.^[2] They recognized that the fossils represented a new oogenus of prismatoolithids, but the description would not be completed until 2014, when they published a description of the new oogenus and oospecies Trigonoolithus amoae in the paleontology journal Acta Palaeontologica Polonica.^[1]

Distribution

Fossils of Trigonoolithus are found in abundance at the La Cantera site of the

Teruel, Spain. This site is dated to the early Barremian age.^[1]

Description

Trigonoolithus is known from numerous eggshell fragments, but no complete or near-complete eggs. The whole egg of T. amoae was 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 through Trigonoolithus's shell to allow for gas exchange. They are angusticanaliculate (meaning the pores are long, straight, and narrow), similar to the pore systems of Prismatoolithus, Sankofa, and Protoceratopsidovum.^[1]^[3]

Parataxonomy

Trigonoolithus is classified in the oofamily Prismatoolithidae, alongside Preprismatoolithus, Prismatoolithus, Protoceratopsidovum, Sankofa, and Spheruprismatoolithus.^[1]

Moreno-Azanza et al. performed multiple

birds.^[1]

Paleobiology

Prismatoolithids were previously hypothesized to be eggs of

maniraptoran are possible parents of Trigonoolithus.^[1]

References

^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ Moreno-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 Paleontology 29 (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.

[MACG-1] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ Moreno-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.

[JVP-2] 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 Paleontology 29 (Supplement to No. 3): 151A.

[Carpenter-3] Carpenter, K. (1999). Eggs, Nests, and Baby Dinosaurs: A Look at Dinosaur Reproduction (Life of the Past). Indiana University Press, Bloomington, Indiana.

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