Comparative osteology of the penguin‐like mid‐Cenozoic Plotopteridae and the earliest true fossil penguins, with comments on the origins of wing‐propelled diving

Mayr, Gérald; Goedert, James L.; Pietri, Vanesa L. De; Scofield, R. Paul

doi:10.1111/jzs.12400

Cited by 12 publications

(12 citation statements)

References 40 publications

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“…Plotopteridae is an extinct lineage of Suliformes (although there is some dispute about their exact phylogenetic position; Smith 2010 ; Mayr et al. 2015 , 2020a ). Eight genera have been described from the upper Eocene–middle Miocene of the Pacific coast of North America and Japan (approximately 35–17 Ma; e.g., Howard 1969 ; Olson and Hasegawa 1985 , 1996 ; Sakurai et al.…”

Section: Introductionmentioning

confidence: 99%

Wing Musculature Reconstruction in Extinct Flightless Auks (PinguinusandMancalla) Reveals Incomplete Convergence with Penguins (Spheniscidae) Due to Differing Ancestral States

Watanabe

Field

Matsuoka

2020

Integrative Organismal Biology

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Despite longstanding interest in convergent evolution, factors that result in deviations from fully convergent phenotypes remain poorly understood. In birds, the evolution of flightless wing-propelled diving has emerged as a classic example of convergence, having arisen in disparate lineages including penguins (Sphenisciformes) and auks (Pan-Alcidae, Charadriiformes). Nevertheless, little is known about the functional anatomy of the wings of flightless auks because all such taxa are extinct, and their morphology is almost exclusively represented by skeletal remains. Here, in order to re-evaluate the extent of evolutionary convergence among flightless wing-propelled divers, wing muscles and ligaments were reconstructed in two extinct flightless auks, representing independent transitions to flightlessness: Pinguinus impennis (a crown-group alcid), and Mancalla (a stem-group alcid). Extensive anatomical data were gathered from dissections of 12 species of extant charadriiforms and 4 aequornithine waterbirds including a penguin. The results suggest that the wings of both flightless auk taxa were characterized by an increased mechanical advantage of wing elevator/retractor muscles, and decreased mobility of distal wing joints, both of which are likely advantageous for wing-propelled diving and parallel similar functional specializations in penguins. However, the conformations of individual muscles and ligaments underlying these specializations differ markedly between penguins and flightless auks, instead resembling those in each respective group’s close relatives. Thus, the wings of these flightless wing-propelled divers can be described as convergent as overall functional units, but are incompletely convergent at lower levels of anatomical organization—a result of retaining differing conditions from each group’s respective volant ancestors. Detailed investigations such as this one may indicate that, even in the face of similar functional demands, courses of phenotypic evolution are dictated to an important degree by ancestral starting points.

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Section: Introductionmentioning

confidence: 99%

Wing Musculature Reconstruction in Extinct Flightless Auks (PinguinusandMancalla) Reveals Incomplete Convergence with Penguins (Spheniscidae) Due to Differing Ancestral States

Watanabe

Field

Matsuoka

2020

Integrative Organismal Biology

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“…Two genera are currently recognized: Miomancalla is known from the Miocene-Pliocene of California (~10-4.9 Ma), and Mancalla is known from the Pliocene (perhaps extending into the Miocene) -Pleistocene of the Pacific coasts of North America and Japan (~5.0-0.12 Ma; e.g., Lucas 1901;Miller and Howard 1949;Chandler 1990;Smith 2011; Smith and Clarke 2015;Watanabe et al 2020aWatanabe et al , 2020b. Plotopteridae is an extinct lineage of Suliformes (although there is some dispute about their exact phylogenetic position; Smith 2010;Mayr et al 2015Mayr et al , 2020a. Eight genera have been described from the upper Eocene -middle Miocene of the Pacific coast of North America and Japan (~35-17 Ma; e.g., Howard 1969;Olson andHasegawa 1985, 1996;Sakurai et al 2008;Goedart 2016, 2018).…”

Section: Introductionmentioning

confidence: 99%

Wing musculature reconstruction in extinct flightless auks (PinguinusandMancalla) reveals incomplete convergence with penguins (Spheniscidae) due to differing ancestral states

Watanabe

Field

Matsuoka

2020

Preprint

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Despite longstanding interest in convergent evolution, factors that result in deviations from fully convergent phenotypes remain poorly understood. In birds, the evolution of flightless wing-propelled diving has emerged as a classic example of convergence, having arisen in disparate lineages including penguins (Sphenisciformes) and auks (Pan-Alcidae, Charadriiformes). Nevertheless, little is known about the functional anatomy of the wings of flightless auks because all such taxa are extinct, and their morphology is almost exclusively represented by skeletal remains. Here, in order to re-evaluate the extent of evolutionary convergence among flightless wing-propelled divers, wing muscles and ligaments were reconstructed in two extinct flightless auks, representing independent transitions to flightlessness: Pinguinus impennis (a crown-group alcid), and Mancalla (a stem-group alcid). Extensive anatomical data were gathered from dissections of 12 species of extant charadriiforms and 4 aequornithine waterbirds including a penguin. It was found that the wings of both flightless auk taxa were characterized by an increased mechanical advantage of wing elevator/retractor muscles, and decreased mobility of distal wing joints, both of which are likely advantageous for wing-propelled diving and parallel similar functional specializations in penguins. However, the conformations of individual muscles and ligaments underlying these specializations differ markedly between penguins and flightless auks, instead resembling those in each respective group’s close relatives. Thus, the wings of these flightless wing-propelled divers can be described as convergent as overall functional units, but are incompletely convergent at lower levels of anatomical organization—a result of retaining differing conditions from each group’s respective volant ancestors. Detailed investigations such as this one may indicate that, even in the face of similar functional demands, courses of phenotypic evolution are dictated to an important degree by ancestral starting points.

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“…A deeply concave cotyla scapularis characterizes the coracoid of many Plotopteridae, which are extinct wing-propelled diving seabirds from the North Pacific and are hypothesized to be part of the Suliformes (Fig. 2j, k; Mayr 2017a; Mayr et al 2021a).…”

Section: Resultsmentioning

confidence: 99%

The coracoscapular joint of neornithine birds—extensive homoplasy in a widely neglected articular surface of the avian pectoral girdle and its possible functional correlates

Mayr

2021

Zoomorphology

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A survey is given of the morphological variation of the coracoscapular joint of neornithine birds. In Mesozoic stem group representatives, the coracoid exhibits a deeply concave cotyla scapularis, which articulates with a globose tuberculum coracoideum of the scapula. This morphology is likely to be functionally related to the development of a powerful supracoracoideus muscle and the formation of a triosseal canal as a pulley for the tendon of this muscle. In neornithine birds, the coracoid articulates with the scapula either via a concave cotyla or a flat facies articularis, with the latter largely restricting movements of the coracoid to the paramedian plane. Ancestral state reconstruction suggests that a cotyla scapularis is plesiomorphic for Neornithes and that a flat facies articularis scapularis evolved at least 13 times independently within the clade. For several lineages, the transition to a flat facies articularis scapularis can be traced in the fossil record, and the replacement of a cup-shaped cotyla by a flat articular facet seems to have been due to various functional demands. Often, a flat facies articularis scapularis is associated with reduced shafts of the furcula. A weakly developed furcula enables transverse movements of the coracoid and therefore enables a restriction of the mobility of the coracoscapular joint to the paramedian plane. In taxa with a large crop, a flat facies articularis scapularis is likely to be associated with a reorganization of the pectoral musculature, whereas in procellariiform birds, the transition from a cotyla to a facies articularis appears to have been correlated with the capacity for sustained soaring without wing flapping.

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Comparative osteology of the penguin‐like mid‐Cenozoic Plotopteridae and the earliest true fossil penguins, with comments on the origins of wing‐propelled diving

Cited by 12 publications

References 40 publications

Wing Musculature Reconstruction in Extinct Flightless Auks (PinguinusandMancalla) Reveals Incomplete Convergence with Penguins (Spheniscidae) Due to Differing Ancestral States

Wing Musculature Reconstruction in Extinct Flightless Auks (PinguinusandMancalla) Reveals Incomplete Convergence with Penguins (Spheniscidae) Due to Differing Ancestral States

Wing musculature reconstruction in extinct flightless auks (PinguinusandMancalla) reveals incomplete convergence with penguins (Spheniscidae) due to differing ancestral states

The coracoscapular joint of neornithine birds—extensive homoplasy in a widely neglected articular surface of the avian pectoral girdle and its possible functional correlates

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