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Five well-supported fossil calibrations within the "Waterbird" assemblage (Tetrapoda, Aves)

Nathan D. Smith and Daniel T. Ksepka

Plain Language Abstract

Fossil calibrations in concert with DNA sequence data allow scientists to reconstruct the timing of evolutionary events. This paper presents a set of fossil calibrations for the "waterbird" assemblage, a group uniting most aquatic and semi-aquatic birds such as storks, herons, frigatebirds, pelicans, ibises, penguins, cormorants, and tropicbirds. For each fossil we review the evidence in the geological record for its age, the features of the skeleton that tell us what group of birds it belongs to and the implications it has for understanding the temporal diversification of the group.

Resumen en Español

Cinco calibraciones fósiles bien respaldadas dentro de la Asociación "Waterbird" (Tetrapoda, Aves)

La asociación "waterbird" es un grupo de aves acuáticas y semiacuáticas que se caracterizan por presentar morfologías, ecologías e historias extremadamente diversas. Este grupo también incluye representantes fósiles que constituyen algunos de los registros más antiguos de Neoaves y son críticos al momento de calibrar la diversificación temporal de las aves modernas. En este trabajo brindamos cinco calibraciones fósiles bien respaldadas dentro del clado "waterbird" que servirán para sustentar calibraciones temporales robustas para los orígenes de los linajes basales de: Phaethontes (rabijuncos o aves del trópico); Threskiornithidae (ibis y espátulas); Pelecanidae (pelícanos); Fregatidae (fragatas); y Phalacrocoracidae (cormoranes). Aplicamos criterios rigurosos para justificar el emplazamiento filogenético y el contexto geocronológico de estos especímenes, y discutir registros potencialmente más antiguos con el objetivo de facilitar el enfoque de futuras investigaciones y recopilaciones. Los fósiles aquí descriptos confirman estudios previos al reconocer que la mayoría de las grandes divisiones cladogenéticas dentro de la asociación "waterbird" tuvieron lugar en el Eoceno, lo cual apoya las interpretaciones tanto de la rápida diversificación de linajes de estas aves acuáticas en el Paleógeno temprano, como del rápido establecimiento de planes corporales y posiblemente morfologías ecológicamente relevantes durante este periodo temporal.

Palabras clave: Aves; Pelecaniformes; calibraciones fósiles; filogenia; reloj molecular

Traducción: Diana Elizabeth Fernández

Résumé en Français

Cinq calibrations fossiles avec bon support au sein de l'assemblage d'"oiseaux aquatiques" (Tetrapoda, Aves)

L'assemblage d'"oiseaux aquatiques" est un groupe d'oiseaux aquatiques et semi-aquatiques qui sont caractérisés par de très diverses morphologies, écologies, et histoires de vie. Le groupe comprend également des représentants fossiles qui constituent certains des registres les plus anciens pour Néoaves et sont essentiels pour l'étalonnage de la diversification temporelle des oiseaux modernes. Ici, nous fournissons un ensemble de cinq calibrations fossiles bien supportées du clade d'oiseaux aquatiques qui serviront à fournir des étalonnages temporelles robustes pour les origines de: la souche de Phaethontes (pailles); la souche de Thréskiornithidé (ibis et spatules) la souche Pélécanidé (pélicans); la souche Frégatidé (frégates); et la souche Phalacrocoracidé (cormorans). Nous appliquons des critères rigoureux pour justifier à la fois la position phylogénétique et le contexte géochronologique de ces spécimens, et de discuter des registres potentiellement plus anciens pour aider à cibler la recherche et la collecte avenir. Les fossiles décrits ici affirment les études précédentes à reconnaître que la plupart des grandes scissions cladogénétiques au sein de l'assemblage des oiseaux aquatiques se produite par l'Eocène, soutenant les interprétations à la fois de diversification rapide de la lignée des oiseaux aquatiques au début du Paléogène, et aussi la mise en place rapide de plans de corps et de morphologies éventuellement écologiquement pertinentes au cours de cette période.

Mots-clés: Aves; Pelecaniformes; calibrations fossiles; phylogénie; horloge moléculaire

Translator: Kenny J. Travouillon

Deutsche Zusammenfassung

In progress

Translator: Eva Gebauer

Arabic

Translator: Ashraf M.T. Elewa

 

 

smithNathan D. Smith
Department of Biology
Howard University
415 College Street NW
Washington, DC 20059
USA
and Department of Paleobiology
National Museum of Natural History
Smithsonian Institution
Washington, DC 20013
USA
This email address is being protected from spambots. You need JavaScript enabled to view it.

Nathan Smith is an Assistant Professor of Biology at Howard University in Washington, DC, and a Research Associate at the Field Museum of Natural History and the Smithsonian National Museum of Natural History. He also currently serves on the USAP Steering Committee for Deep Field Camps in the Transantarctic Mountains. Nate received his B.A. from Augustana College, a M.S. from the University of Iowa, and a Ph.D. from the University of Chicago. Nate’s research is funded by the National Science Foundation and National Geographic, and focuses on the evolution and biogeography of Triassic–Jurassic dinosaurs, Cenozoic waterbirds (e.g., penguins, pelicans, and allies), scleractinian corals, and the application of phylogenetic comparative methods to broad questions in systematic biology and paleontology. Nate has conducted fieldwork in Antarctica, Argentina, China, and the southwestern and western United States.

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kpsekaDaniel T. Ksepka
Bruce Museum
1 Museum Drive
Greenwich, Connecticut 06830
USA
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Dan Ksepka is a vertebrate paleontologist and evolutionary biologist at the National Evolutionary Synthesis Center. He received a BS in Geological Sciences from Rutgers University and a PhD in Earth and Environmental Sciences from Columbia University through the American Museum of Natural History joint fellowship program. His current research focuses on exploring patterns of congruence and disparity between fossil ages and molecular divergence dates. Dan is also interested in major evolutionary transitions in birds, especially the evolution of wing-propelled diving in penguins. He enjoys sharing science with all types of audiences and blogs at March of the Fossil Penguins (fossilpenguins.wordpress.com).

 

TABLE 1. Fossil calibrations within the waterbird assemblage.

Calibration

Node

Taxon

Specimen

Geological Context

Minimum Age

1 Phaethontidae + extant sister taxon Lithoptila abdounensis OCP.DEK/GE 1087 Bed IIa, Ouled Abdoun Basin, Morocco 56.0 Ma
2 Threskiornithidae + extant sister taxon Rhynchaeites sp. MGUH 20288 Fur Formation, NE Denmark 53.9 Ma
3 Pelecanidae + extant sister taxon Pelecanus sp. NT-LBR-039 Pichovet limestone deposits, SE France 28.1 Ma
4 Fregatidae + Suloidea Limnofregata azygosternon USNM 22753 Green River Formation, Wyoming, USA 51.81 Ma
5 Phalacrocoracidae + Anhingidae ?Borvocarbo stoeffelensis PW 2005/5022-LS Enspel Lagerstätte, W Germany 24.52 Ma
 

FIGURE 1. Specimens representative of two taxa that provide fossil calibrations within the waterbird assemblage. 1, Limnofregata azygosternon (USNM 22753) from the early Eocene Green River Formation represents the sister taxon (with its congener Limnofregata hasegawai ) to Fregata, and calibrates the node Fregatidae + Suloidea. 2, Rhynchaeites messelensis (SMF 218) from the middle Eocene of Messel. Together with other Messel Rhynchaeites messelensis specimens and Rhynchaeites sp. (MGUH 20288) from the early Eocene Fur Formation, these represent the sister taxon to Threskiornithidae, and MGUH 20288 calibrates the node uniting Threskiornithidae and its extant sister taxon. Scale bars equal 50 mm.

figure1

FIGURE 2. Preferred phylogenetic tree based on the phylogenomic analysis of Hackett et al. (2008) showing the family-level relationships (with silhouettes of representatives within each family) within the waterbird assemblage, with five fossil calibrations (Table 1) included. Groups color-coded by membership in traditional avian orders: Pelecaniformes (green), Ciconiiformes (orange), Procellariiformes (blue), Sphenisciformes (brown), Podicipediformes (gold), Gaviiformes (purple). Stratigraphy and associated ages from Cohen et al. (2013; see also Walker et al., 2013). Branches (internodes) outside of fossil calibrations are set to a unit length to make topological relationships clear, and are not intended to represent actual divergence times. Double hash marks indicate that the clade containing Phaethon, Podiceps, and Phoenicopterus is actually recovered as distantly related to the waterbird clade (i.e., it is not its sister-taxon). Nodes that are numbered correspond to fossil calibrations described in the text. Asterisk next to Waimanu manneringi references a vetted calibration from Ksepka and Clarke (2015). Abbreviations: E, Early. M, Middle. L, Late.

figure2

FIGURE 3. Alternative phylogenetic tree based on the osteological analysis of Smith (2010) showing the family-level relationships (with silhouettes of representatives within each family) within the waterbird assemblage, with five fossil calibrations (Table 1) included. Groups color-coded by membership in traditional avian orders: Pelecaniformes (green), Ciconiiformes (orange), Procellariiformes (blue), Sphenisciformes (brown), Podicipediformes (gold), Gaviiformes (purple). Stratigraphy and associated ages from Cohen et al. (2013; see also Walker et al., 2013). Branches (internodes) outside of fossil calibrations are set to a unit length to make topological relationships clear, and are not intended to represent actual divergence times. Nodes that are numbered correspond to fossil calibrations described in the text. Asterisk next to Waimanu manneringi references a vetted calibration from Ksepka and Clarke (2015). Abbreviations: E, Early. M, Middle. L, Late.

figure3