Trilobites showed strong resilience capacity through the Late Devonian events despite an inexorable decline

Bault, Valentin

doi:10.1016/j.palaeo.2023.111807

Cited by 1 publication

(2 citation statements)

References 109 publications

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“…3). This may reflect the differences in the orders’ broad-scale evolutionary trajectories, with phacopids being more diverse earlier in the Palaeozoic and proetids later, resulting from apparent turnover events (e.g., Bault, 2023). Proetida is notably constrained at the centre of the morphospace (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…10). This presumably reflects external selection pressures on proetids during the Carboniferous and Permian as the only trilobite order surviving into the Permian, over their decline to eventual extinction (e.g., Adrain, 2013; Bault, 2023; Bault et al, 2022; Fortey, 2001). Lerosey-Aubril and Feist (2012) found that proetids in the late Palaeozoic experienced many separate extinction and radiation events, though our dataset suggests this is not reflected in their cephalic shape disparity averaged across this time, and our time bins are too coarse to provide the required resolution to detect both extinctions and radiations within geological Periods.…”

Section: Discussionmentioning

confidence: 99%

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Distinct causes underlie double-peaked trilobite morphological disparity

Drage,

Pates

2024

Preprint

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Trilobite cephalic morphology impacted the autecology of individuals, and is critical for high- and low-level taxonomic assignments. Disparity in trilobite cephalon shape varied through time and was integral to the occupation of a diversity of ecological niches. To fully appreciate trilobite cephalic evolution, we must understand how this disparity varies, and what factors control cephalon morphometry. We explore the disparity of trilobite cephala through the Palaeozoic, and analyse the associations between cephalic morphometry and taxonomic assignment and geological Period, using a dataset of 983 2D trilobite cephalon outlines. Elliptical Fourier transformation visualised as a Principal Components Analysis suggests significant differences in morphospace occupation for order and Period groups, and comparisons of disparity measures also suggest significantly different disparities between the groups. Trilobite cephalic disparity peaks in the Ordovician and Devonian. The Cambrian–Ordovician expansion of morphospace occupation appears a result of radiation to new niches, and thus all trilobite orders were established by the late Ordovician. In comparison, the morphospace expansion from the Silurian to Devonian seems solely a result of within-niche diversification rather than novel niche occupation. However, analyses interrogating the regions of morphospace occupied, including centroid distances, average pairwise shape comparisons and Linear Discriminant Analysis demonstrate that, except for the order Harpida and the Cambrian and Ordovician Periods, order and geological Period could not be robustly predicted for an unknown trilobite. Further, Kmeans clustering analyses suggest the total dataset naturally subdivides into only seven groups that do not correspond with taxonomic orders, though Kmeans clusters do decrease in number through the Palaeozoic, aligning with findings of decreasing disparity.

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Section: Discussionmentioning

confidence: 99%