Dataset Information

Patterns of mammalian jaw ecomorphological disparity during the Mesozoic/Cenozoic transition.

ABSTRACT: The radiation of mammals after the Cretaceous/Palaeogene (K/Pg) boundary was a major event in the evolution of terrestrial ecosystems. Multiple studies point to increases in maximum body size and body size disparity, but patterns of disparity for other traits are less clear owing to a focus on different indices and subclades. We conducted an inclusive comparison of jaw functional disparity from the Early Jurassic-latest Eocene, using six mechanically relevant mandibular ratios for 256 species representing all major groups. Jaw functional disparity across all mammals was low throughout much of the Mesozoic and remained low across the K/Pg boundary. Nevertheless, the K/Pg boundary was characterized by a pronounced pattern of turnover and replacement, entailing a substantial reduction of non-therian and stem-therian disparity, alongside a marked increase in that of therians. Total mammal disparity exceeded its Mesozoic maximum for the first time during the Eocene, when therian mammals began exploring previously unoccupied regions of function space. This delay in the rise of jaw functional disparity until the Eocene probably reflects the duration of evolutionary recovery after the K/Pg mass extinction event. This contrasts with the more rapid expansion of maximum body size, which occurred in the Palaeocene.

SUBMITTER: Benevento GL

PROVIDER: S-EPMC6532522 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Patterns of mammalian jaw ecomorphological disparity during the Mesozoic/Cenozoic transition.

Benevento Gemma Louise GL Benson Roger B J RBJ Friedman Matt M

Proceedings. Biological sciences 20190501 1902

The radiation of mammals after the Cretaceous/Palaeogene (K/Pg) boundary was a major event in the evolution of terrestrial ecosystems. Multiple studies point to increases in maximum body size and body size disparity, but patterns of disparity for other traits are less clear owing to a focus on different indices and subclades. We conducted an inclusive comparison of jaw functional disparity from the Early Jurassic-latest Eocene, using six mechanically relevant mandibular ratios for 256 species re ...[more]

PMID: 31039714

Similar Datasets

Project description:BackgroundMuch of the current research in the growing field of evolutionary development concerns relating developmental pathways to large-scale patterns of morphological evolution, with developmental constraints on variation, and hence diversity, a field of particular interest. Tooth morphology offers an excellent model system for such 'evo-devo' studies, because teeth are well preserved in the fossil record, and are commonly used in phylogenetic analyses and as ecological proxies. Moreover, tooth development is relatively well studied, and has provided several testable hypotheses of developmental influences on macroevolutionary patterns. The recently-described Inhibitory Cascade (IC) Model provides just such a hypothesis for mammalian lower molar evolution. Derived from experimental data, the IC Model suggests that a balance between mesenchymal activators and molar-derived inhibitors determines the size of the immediately posterior molar, predicting firstly that molars either decrease in size along the tooth row, or increase in size, or are all of equal size, and secondly that the second lower molar should occupy one third of lower molar area. Here, we tested the IC Model in a large selection of taxa from diverse extant and fossil mammalian groups, ranging from the Middle Jurassic (~176 to 161 Ma) to the Recent.ResultsResults show that most taxa (~65%) fell within the predicted areas of the Inhibitory Cascade Model. However, members of several extinct groups fell into the regions where m2 was largest, or rarely, smallest, including the majority of the polyphyletic "condylarths". Most Mesozoic mammals fell near the centre of the space with equality of size in all three molars. The distribution of taxa was significantly clustered by diet and by phylogenetic group.ConclusionsOverall, the IC Model was supported as a plesiomorphic developmental system for Mammalia, suggesting that mammal tooth size has been subjected to this developmental constraint at least since the divergence of australosphenidans and boreosphenidans approximately 180 Ma. Although exceptions exist, including many 'condylarths', these are most likely to be secondarily derived states, rather than alternative ancestral developmental models for Mammalia.

Project description:This study examined the dynamic coordination between disconjugate, vergence eye movements, and pupil size in 52 normal subjects during binocular disparity stimulation in a virtual reality display. Eye movements and pupil area were sampled with a video-oculographic system at 100 Hz during performance of two tasks, (1) fusion of a binocular disparity step (±1.5° of visual angle in the horizontal plane) and (2) pursuit of a sinusoidally varying binocular disparity stimulus (0.1 Hz, ±2.6° of visual angle in the horizontal plane). Pupil size data were normalized on the basis of responses to homogeneous illumination increments ranging from 0.42 to 65.4 cd/m2. The subjects produced robust vergence eye movements in response to disparity step shifts and high fidelity sinusoidal vergence responses (R 2 relative to stimulus profile: 0.933 ± 0.088), accompanied by changes in pupil area. Trajectory plots of pupil area as a function of vergence angle showed that the pupil area at zero vergence is altered between epochs of linear vergence angle-pupil area relations. Analysis with a modified Gath-Geva clustering algorithm revealed that the dynamic relationship between the ocular vergence angle and pupil size includes two different transient, synkinetic response patterns. The near response pattern, pupil constriction during convergence and pupil dilation during divergence, occurred ~80% of the time across subjects. An opposite, previously undescribed synkinetic pattern was pupil constriction during divergence and pupil dilatation during convergence; it occurred ~15% of the time across subjects. The remainder of the data were epochs of uncorrelated activity. The pupil size intercepts of the synkinetic segments, representing pupil size at initial tropia, had different relationships to vergence angle for the two main coordinated movement types. Hippus-like movements of the pupil could also be accompanied by vergence movements. No pupil coordination was observed during a conjugate pursuit task. In terms of the current dual interaction control model (1), findings suggest that the synkinetic eye and pupillary movements are produced by a dynamic switch of the influence of vergence related information to pupil control, accompanied by a resetting of the pupil aperture size at zero-vergence.

Dataset Information

Patterns of mammalian jaw ecomorphological disparity during the Mesozoic/Cenozoic transition.

Publications

Patterns of mammalian jaw ecomorphological disparity during the Mesozoic/Cenozoic transition.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets