Oldest known dinosaurian nesting site and reproductive biology of the Early Jurassic sauropodomorphMassospondylus

Abstract

The extensive Early Jurassic continental strata of southern Africa have yielded an exceptional record of dinosaurs that includes scores of partial to complete skeletons of the sauropodomorph Massospondylus , ranging from embryos to large adults. In 1976 an incomplete egg clutch including in ovo embryos of this dinosaur, the oldest known example in the fossil record, was collected from a road-cut talus, but its exact provenance was uncertain. An excavation program at the site started in 2006 has yielded multiple in situ egg clutches, documenting the oldest known dinosaurian nesting site, predating other similar sites by more than 100 million years. The presence of numerous clutches of eggs, some of which contain embryonic remains, in at least four distinct horizons within a small area, provides the earliest known evidence of complex reproductive behavior including site fidelity and colonial nesting in a terrestrial vertebrate. Thus, fossil and sedimentological evidence from this nesting site provides empirical data on reproductive strategies in early dinosaurs. A temporally calibrated optimization of dinosaurian reproductive biology not only demonstrates the primary significance of the Massospondylus nesting site, but also provides additional insights into the initial stages of the evolutionary history of dinosaurs, including evidence that deposition of eggs in a tightly organized single layer in a nest evolved independently from brooding.

Taphonomical and palaeoecological investigation of the Late Cretaceous (Maastrichtian) Tuştea vertebrate assemblage (Romania; Haţeg Basin) - insights into a unique dinosaur nesting locality

“…The fact that identical megaloolithid eggs and clutches occur associated with two different calcrete levels (thus represent distinct, successive time intervals) suggests that members of the same egg-laying taxon returned to the same nesting area on at least two occasions, a pattern of multi-year repeated usage of the same nesting area described previously as "nest site fidelity" (e.g., Horner, 1982Horner, , 2000Moratalla and Powell, 1994;Mohabey, 1996;Chiappe et al, 2003Chiappe et al, , 2005Garcia et al, 2003;Grellet-Tinner and Fiorelli, 2010;Reisz et al, 2012). Discovery of isolated eggshell fragments below the crevasse-splay sandstone in 1994 would represent another argument to support the scenario of multiple re-utilisation of the same nesting area, but further support in this respect, through discovery of eggs, nests and eventually hatchling remains in this lowermost egg-bearing level, is required.…”

South Africa's coalfields — A 2014 perspective

“…Palaeontologically the Elliot Formation is important for its Late Triassic to Early Jurassic dinosaur and associated fauna (Kitching and Raath, 1984;Olsen and Galton, 1984;Smith and Kitching, 1997;Warren and Damiani, 1999;Yates and Kitching, 2003;Yates et al, 2004;Sidor and Hancox, 2006;Reisz et al, 2013;McPhee et al, 2014). This list is by no means definitive but would give the interested reader a good overview and covers most of the main fauna known.…”

Evolution of parental incubation behaviour in dinosaurs cannot be inferred from clutch mass in birds

“…However, it is known that phylogeny does affect many allometric relationships in bird reproduction, including egg composition [3] and energetics [4]. Lack of consideration of possible confounding factors in Varricchio et al's study justifies a reanalysis, particularly because the application of their technique is apparently going to see wider use [2].…”

“…Their conclusion was based largely on an allometric analysis of avian clutch volume (CV) against female body mass (FBM) for each type of parental care behaviour. Varricchio et al's allometric analysis was recently used to infer the sex of the parent providing parental care in the sauropodomorph dinosaur Massospondylus [2]. However, Varricchio et al [1] did not consider numerous wellknown factors associated with variation in egg and clutch size in extant birds, which prompted us to re-evaluate their allometric model using our own data.…”