Phylogenetic relationships of the ‘higher heterostracans’ (Heterostraci: Pteraspidiformes and Cyathaspididae), extinct jawless vertebrates

Randle, Emma; Sansom, Robert S.

doi:10.1093/zoolinnean/zlx025

Cited by 12 publications

(101 citation statements)

References 41 publications

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“…One segment of heterostracan diversity, the paraphyletic Cyathaspidiformes (41), first appear on the backreef and are preferentially found in reefal and deep lagoonal environments early, while the widespread, relatively robust and flattened genera Poraspis and Vernonaspis and some other late occurring forms shifted back to shore and freshwaters. In contrast, the other monophyletic division, the Pteraspidiformes (41), stay in the shallows and move into freshwater early, while a few later, streamlined lineages (including the Rhinopteraspis) make it to the shelf and open ocean ( Figs. 2A, S6; Additional Data File S1).…”

Section: Supplementary Text Fossil Record Summaries For Mid-paleozoicmentioning

confidence: 99%

The Nearshore Cradle of Early Vertebrate Diversification

Sallan¹,

Friedman²,

Sansom³

et al. 2018

Geological Society of America Abstracts With Programs

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Ancestral vertebrate habitats are subject to controversy, and obscured by limited, often contradictory, paleontological data. We assembled fossil vertebrate occurrence and habitat datasets spanning the mid-Paleozoic (480-360 Mya) and found that early vertebrate clades, both jawed and jawless, originated in restricted, shallow intertidal-subtidal environments. Nearshore divergences gave rise to body plans with different dispersal abilities: robust fishes shifted more shoreward while gracile groups moved seaward. Freshwaters were invaded repeatedly, but movement to deeper waters was contingent upon form, and short-lived until the later Devonian. Our results contrast with the onshore-offshore trends, reef-centered diversification, and mid-shelf clustering observed in benthic invertebrates. Nearshore origins for vertebrates may be linked to the demands of their mobility, and influenced the structure of their early fossil record and diversification. One sentence summary: Early vertebrates diversified in restricted, shallow marine waters, with nearshore divergence in body form shaping their dispersal and fossil record.

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Section: Supplementary Text Fossil Record Summaries For Mid-paleozoicmentioning

confidence: 99%

The Nearshore Cradle of Early Vertebrate Diversification

Sallan¹,

Friedman²,

Sansom³

et al. 2018

Geological Society of America Abstracts With Programs

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“…Given different topologies for the same set of fossil taxa, stratigraphic congruence metrics can be used to support one solution or technique over another (e.g. [ 19 ]), but broader conclusions will be hard to draw from any one dataset. Here, we take a meta-analysis approach; we use a wide range of published morphological data matrices of crown-group tetrapods to compare maximum parsimony (equal and implied weights) and Bayesian (Mk) trees in terms of stratigraphic congruence.…”

Section: Introductionmentioning

confidence: 99%

Parsimony, not Bayesian analysis, recovers more stratigraphically congruent phylogenetic trees

et al. 2018

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Reconstructing evolutionary histories requires accurate phylogenetic trees. Recent simulation studies suggest that probabilistic phylogenetic analyses of morphological data are more accurate than traditional parsimony techniques. Here, we use empirical data to compare Bayesian and parsimony phylogenies in terms of their congruence with the distribution of age ranges of the component taxa. Analysis of 167 independent morphological data matrices of fossil tetrapods finds that Bayesian trees exhibit significantly lower stratigraphic congruence than the equivalent parsimony trees. As such, taking stratigraphic data as an independent benchmark indicates that parsimony analyses are more accurate for phylogenetic reconstruction of morphological data. The discrepancy between simulated and empirical studies may result from historic data peaking practices or some complexities of empirical data as yet unaccounted for.

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“…The timing and nature of these morphological diversifications is unclear, as is the best way to quantify the morphological variation. For example, the difficulty in taxonomic assignment and phylogenetic reconstruction of the Pteraspidiformes (the largest clade of heterostracan ostracoderms) can be attributed to the continuous variation in their dermal plates which is often used to discriminate between taxonomic grades ( Ilyes & Elliott, 1994 ; Pernègre, 2002 ; Pernègre & Goujet, 2007 ; Pernègre & Elliott, 2008 ; Randle & Sansom, 2017a ; Randle & Sansom, 2017b ). The Pteraspidiformes are characterised by possessing separate dorsal, ventral, rostral and pineal plates along with paired branchial, orbital and in some instances cornual plates ( Fig.…”

Section: Introductionmentioning

confidence: 99%

“…The Pteraspidiformes are characterised by possessing separate dorsal, ventral, rostral and pineal plates along with paired branchial, orbital and in some instances cornual plates ( Fig. 1D ) ( Blieck, 1984 ; Blieck, Elliott & Gagnier, 1991 ; Janvier, 1996 ; Pernègre & Elliott, 2008 ; Randle & Sansom, 2017a ; Randle & Sansom, 2017b ). The Pteraspidiformes include many families and taxa of uncertain affinities.…”

Section: Introductionmentioning

confidence: 99%

Morphospace saturation in the stem-gnathostomes pteraspidiformes heterostracans: an early radiation of a ‘bottom’ heavy clade

Romano

Sansom

Randle

2018

PeerJ

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Ostracoderms (fossil armoured jawless fishes) shed light on early vertebrate evolution by revealing the step-wise acquisition of jawed vertebrate characters, and were important constituents of Middle Palaeozoic vertebrate faunas. A wide variety of head shield shapes are observed within and between the ostracoderm groups, but the timing of these diversifications and the consistency between different measures of their morphospace are unclear. Here, we present the first disparity (explored morphospace) versus diversity (number of taxa) analysis of Pteraspidiformes heterostracans using continuous and discrete characters. Patterns of taxic diversity and morphological disparity are in accordance: they both show a rise to a peak in the Lochkovian followed by a gradual decline in the Middle-Late Devonian. Patterns are largely consistent for disparity measures using sum of ranges or total variance, and when using continuous or discrete characters. Pteraspidiformes heterostracans can be classified as a “bottom-heavy clade”, i.e., a group where a high initial disparity decreasing over time is detected. In fact, the group explored morphospace early in its evolutionary history, with much of the subsequent variation in dermal armour occurring as variation in the proportions of already evolved anatomical features. This Early Devonian radiation is also in agreement with the paleobiogeographic distribution of the group, with a maximum of dispersal and explored morphospace during the Lochkovian and Pragian time bins.

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Phylogenetic relationships of the ‘higher heterostracans’ (Heterostraci: Pteraspidiformes and Cyathaspididae), extinct jawless vertebrates

Cited by 12 publications

References 41 publications

The Nearshore Cradle of Early Vertebrate Diversification

The Nearshore Cradle of Early Vertebrate Diversification

Parsimony, not Bayesian analysis, recovers more stratigraphically congruent phylogenetic trees

Morphospace saturation in the stem-gnathostomes pteraspidiformes heterostracans: an early radiation of a ‘bottom’ heavy clade

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