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Dinosaur Eggs

University of Bristol
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Types of dinosaur eggs

Two major types of dinosaur eggs are recognised: spheroidal and elongated. These types can be further sub-divided based on length/diameter ratios, the thickness of the shell, the type of pores and the surface of the egg (may be ornamented).

The egg structure consists of a series of basic vertical units that grow from particular sites on the surface of the shell. The organisation of these units determines the classification scheme, being either spherulitic or prismatic:

  1. Spherulitic egg shells show spherical patterns in the crystalline structure, and they are seen in sauropods and hadrosaurs.
  2. Prismatic egg shells grow into spherical crystals only in the lower portion of the shell, while crystals in the upper portion are prisms.
  3. Ornithoid eggs (also seen in birds) are generally laid by theropods. In this type only the very bottom part of the shell exists as separate or discrete units (mammilae). The upper and mid-portions of the shell consist of a mass of biocrystalline material with a spongy (squamatic) ultrastructure, that comprises a homogeneous layer.

Egg types seen in dinosaurs

(modified from Moratalla 1994).