Geoscience Reference
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such as an extendable tube that projected from the cloaca and thus brought the eggs
closer to the ground without the sauropod mother having to squat. Another method
would have been to use mucus, which would have acted like a slimy envelope to
keep each egg from going into freefall, instead gently lowering it to the nest. Sadly,
sauropod soft tissues or mucus produced by these animals are extremely unlikely to
have been preserved in the fossil record, so these are very difficult hypotheses to
test properly.
In any case, an idealized suite of trace fossils documenting sauropod egg-lay-
ingwouldshowherhind-footimpressionsoneithersideoftheneststructure,point-
ing forward and perhaps overlapping as she laid eggs from the rear of the nest to
the front. If all things were equal in the mud or sand preserving the tracks, though,
evidence of sauropod squatting should have generated more depth or deformational
structures in and around her tracks, which would also help to explain whether they
got close to the ground or stood up high. Also, however thrilling it would be to find
a trace fossil of an egg impact, complete with splatter pattern caused by the explo-
sion of yolk and eggshell, this is rather doubtful when one considers how quickly
such an inept reproductive strategy would be lost from a sauropod lineage.
Based on what we now know from a blend of body fossils and trace fossils,
nesting titanosaurs should have had the following sequence take place, from doing
the deed to making the nursery, so to speak:
• Successful mating which resulted in fertilization (let's not forget that im-
portant step);
• A female and/or male sauropod, but probably the female, found a suitable
spot for digging;
• The sauropod used one or both of its rear legs to scratch down and behind
her, but added an outward twist to remove the loosened sediment;
• The mother stood over the elongated and slightly asymmetrical trough to
deposit the eggs, probably starting at the rear and moving forward;
• The sauropod(s) may or may not have buried the eggs.
