Old World Ruminant Morphophysiology, Life History, and Fossil Record: Exploring Key Innovations of a Diversification Sequence

Abstract

The omasum of pecoran ruminants (which is absent in tragulids) and shorter gestation periods in non-giraffid crown pecorans (as opposed to giraffids) could represent cases of key innovations that caused disparity in species diversity in extant ruminants. Literature suggests that the different ruminant groups inhabited similar niche spectra at different times, supporting the 'increased fitness' interpretation where a key innovation does not mainly open new niches, but allows more efficient use of existing ones. In this respect, we explored data on fossil species diversity of Afro-Eurasian ruminants from the Neogene and Quaternary. Tragulid and giraffid diversity first increased during the Early/Middle Miocene with subsequent declines, whereas bovid and cervid diversity increased distinctively. Our resulting narrative, combining digestive physiology, life history and the fossil record, thus provides an explanation for the sequence of diversity patterns in Old-World ruminants.

Physiological adaptations of ruminants and their potential relevance for production systems

“…This fluid could represent a burden on the enzyme-secreting function of the abomasum and small intestine (that would have to compensate for the dilution effect with increased secretion rates). The omasum has been interpreted as the organ that reabsorbs this fluid and hence facilitates an efficient sorting mechanism and a great fluid throughput linked to high feed intake (Clauss and Rössner, 2014).…”

Digesta retention patterns of solute and different-sized particles in camelids compared with ruminants and other foregut fermenters

“…Interpreting the effects of morphophysiological characteristics of the GIT as constraint for other physiological functions, and ultimately for the competitiveness and diversity of taxonomic groups, could lead to instructive narratives (e.g. Janis et al 1994;Clauss and Rössner 2014). In the case of camelids, both more functional measurements, such as particle size distributions in the different FS compartments, and a systematic evaluation of the fossil record in comparison to ruminants, are necessary to support such a narrative.…”

Augmenting Trait-Dependent Diversification Estimations with Fossil Evidence: A Case Study Using Osmoregulatory Neurovasculature

“…3). FF has been inferred for 27 families and can be represented by a gradient from no fermentation to full fermentation, depending on morphology, inferred diet (e.g., omnivory, graze, and browse), and taxonomic affinities [Janis, 1976;Bodmer, 1989;Hofmann, 1989;Janis et al, 1998;Clauss and Rössner, 2014]. Most extinct families are inferred to have an intermediate degree, 8 are thought to have little or no capacity for FF, and 3 are thought to have full FF capacity (Fig.…”

“…rumination, FF; Fig. 2) [Janis, 1976[Janis, , 2007Gentry, 2000;Vrba and Schaller, 2000;Hassanin and Douzery, 2003;Clauss and Rössner, 2014;DeMiguel et al, 2014]. Nearly perfect character overlap may suggest functional integration, but it can also be typified as Maddison and FitzJohn's [2015] "Darwin scenario," wherein the trait correlation may arise through common ancestry rather than a functional or adaptive scenario [Darwin, 1872].…”