In vitro digestibility of fern and gymnosperm foliage: implications for sauropod feeding ecology and diet selection

Abstract

Sauropod dinosaurs, the dominant herbivores throughout the Jurassic, challenge general rules of large vertebrate herbivory. With body weights surpassing those of any other megaherbivore, they relied almost exclusively on pre-angiosperm plants such as gymnosperms, ferns and fern allies as food sources, plant groups that are generally believed to be of very low nutritional quality. However, the nutritive value of these taxa is virtually unknown, despite their importance in the reconstruction of the ecology of Mesozoic herbivores. Using a feed evaluation test for extant herbivores, we show that the energy content of horsetails and of certain conifers and ferns is at a level comparable to extant browse. Based on our experimental results, plants such as Equisetum, Araucaria, Ginkgo and Angiopteris would have formed a major part of sauropod diets, while cycads, tree ferns and podocarp conifers would have been poor sources of energy. Energy-rich but slow-fermenting Araucaria, which was globally distributed in the Jurassic, was probably targeted by giant, high-browsing sauropods with their presumably very long ingesta retention times. Our data make possible a more realistic calculation of the daily food intake of an individual sauropod and improve our understanding of how large herbivorous dinosaurs could have flourished in preangiosperm ecosystems.

A simulated bird gastric mill and its implications for fossil gastrolith authenticity

“…They may give more resistance to gastroliths and diminish impacts between stones. If conifer (i.e., auracarian) needles contributed a major part to the diet of sauropodomorph dinosaurs as suggested by their high levels of energy available after prolonged fermentation (Hummel et al 2008); and if the stones were subject to very limited abrasion for a long period, gastrolith polish may have formed in the digestive tract of sauropodomorphs. However, more research is needed to test this hypothesis.…”

The evolution of ornithischian quadrupedality

“…A shift to obligate high-fibre herbivory has also been linked to the development of sauropod quadrupedality for similar reasons, with the need to turn the body into an efficient fermentation chamber (e.g. Hummel et al 2008;Wilkinson and Ruxton 2013). All known herbivorous non-avian theropods retain bipedality but, as with bipedal ornithischians, many of these taxa are narrow-snouted and might have been selective or specialist feeders, although it should be noted that therizinosaurs do possess deep thoraxes and laterally flared ilia suggestive of elongate guts (Paul 1984;Barrett 2005;Zanno and Makovicky 2011;Lautenschlager et al 2016).…”

Predation and protection in the macroevolutionary history of conifer cones

“…The initial shift in tissue investment in the Jurassic is roughly concurrent with the diversification of large sauropod dinosaurs in the Early to Middle Jurassic [30,31] and a consequent increase in vertebrate browsing height [13], although the exact height is debated [32,33]. Intriguingly, the first conifer group to develop truly large cones (Araucariaceae, with Jurassic cones up to 15 cm in diameter) has also been suggested as a primary sauropod food source based on their ubiquity and the relatively high energy content of their foliage [34]. The appearance of early birds and potentially arboreal mammals by the Late Jurassic [26,27], and the subsequent radiation of modern bird groups and small placental mammals in the Early Cenozoic, almost certainly resulted in a further increase in vertebrate seed predation pressures in the canopy, since these groups are effective seed predators in modern ecosystems and are known to cause morphological changes within extant species (such as larger, more robust scales or proportionally more cone tissue relative to seed tissue [22,35 -38]) that mirror changes seen in the fossil record on a much broader taxonomic scale.…”