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A new member of the family Plotopteridae (Aves) from the late Oligocene of British Columbia, Canada

Gary Kaiser, Junya Watanabe, and Marji Johns

Plain Language Abstract

The Oligocene sandstones of the Sooke Formation, at the southern end of Vancouver Island, British Columbia, are rich in mammal fossils from 24 million years ago, but bird fossils are scarce. One was found in the 1890s but no more appeared until three bones were given to the Royal BC Museum at the end of 2013. Two were incomplete leg bones that were not very informative but the third was a complete and well-preserved coracoid. In birds, the coracoid lies in the shoulder at the focus of forces generated by forelimb-powered locomotion. The forces shape the articulating surfaces for the scapula, furcula, and humerus into distinctive features. In contrast, the shaft of the coracoid is usually simple, ending in a wide flange that distributes stress to the breastbone.

The head of the Sooke coracoid included a set of features that identified its owner as a small member of the Plotopteridae, an extinct family of wing-propelled diving birds that lived in the North Pacific Ocean between 16 and 35 million years ago. The shaft of the new fossil is exceptionally long and slender, as in other plotopterids. It does not end in a wide flange.

The biggest difference between this new fossil and other plotopterids is size. Most plotopterids were giants, reaching 2m in length. The new fossil suggests a bird about the size of a small cormorant. Plotopterum joaquinensis, the first species to be discovered, is the only one known to have a similar size.

The details of structures on the head of the Sooke fossil differ from Plotopterum joaquinensis and we named the new find Stemec suntokum. The genus name means long-necked duck in the language of the first nation's people from Sooke and the species name recognizes the work of Leah and Graham Suntok who found the fossil.

Resumen en Español

Un nuevo miembro de la familia Plotopteridae (Aves) del Oligoceno tardío de la Columbia Británica, Canadá

El descubrimiento de un fósil de ave, en rocas del Oligoceno superior de la Formación Sooke en el suroeste de la Isla de Vancouver, Columbia Británica, constituye el primer ejemplo para Canadá de Plotopteridae, una familia extinta que vivió en el Pacífico Norte desde finales del Eoceno al Mioceno temprano. El fósil es un coracoides bien conservado y prácticamente completo que exhibe las características diagnósticas de la familia. Se describe Stemec suntokum como un nuevo género y especie para esta extinta familia de aves con buceo propulsado por las alas. Los coracoides son huesos excepcionalmente informativos que se encuentran en el foco de las fuerzas que actúan sobre el hombro y donde juegan un papel importante en la biomecánica de la locomoción de las aves. El coracoides de Stemec tiene un eje inusualmente estrecho, cónico, que difiere fundamentalmente de los coracoides aplastados y anchos de otros grupos de aves.

Palabras clave: fósiles de aves; Columbia Británica; Nuevas especies; Pacífico Norte; Oligoceno; Plotopteridae

Traducción: Enrique Peñalver

Résumé en Français

Un nouveau représentant de la famille Plotopteridae (Aves) de l'Oligocène récent de Colombie-Britannique, Canada

Un fossile d'oiseau découvert dans l'Oligocène supérieur des roches de la formation de Sooke au sud-ouest de l'île de Vancouver, Colombie-Britannique, est le premier représentant canadien des Plotopteridae, une famille disparue qui vivait dans le Pacifique Nord de l'Éocène récent au Miocène ancien. Le fossile est un coracoïde quasi-complet et bien préservé, montrant les caractères diagnostiques de cette famille. Stemec suntokum est décrit comme un nouveau genre et une nouvelle espèce de cette famille disparue d'oiseaux plongeurs utilisant leurs ailes pour se propulser sous l'eau. Les coracoïdes sont des os exceptionnellement informatifs, situés au point de rencontre des forces agissant sur l'épaule où ils jouent un rôle majeur dans la biomécanique de la locomotion des oiseaux. Le coracoïde de Stemec présente une diaphyse inhabituellement étroite et conique, différant de manière fondamentale des coracoïdes larges et aplatis des autres groupes d'oiseaux.

Mots-clés : fossiles d'oiseaux ; Colombie-Britannique ; nouvelle espèce ; Pacifique Nord ; Oligocène ; Plotopteridae

Translator: Antoine Souron

Deutsche Zusammenfassung

Ein neues Mitglied der Familie Plotopteridae (Aves) aus dem späten Oligozän von British Columbia, Kanada

Der Fund eines Vogelfossils in der oberoligozänen Sooke Formation des südwestlichen Vancouver Island, British Columbia ist der erste Nachweis der Plotopteridae, einer ausgestorbenen Familie, die vom späten Eozän bis ins frühe Miozän im Nordpazifik lebte. Das Fossil ist ein nahezu komplettes, gut erhaltenes Coracoid, das die diagnostischen Merkmale der Familie aufweist. Stemec suntokum wird als neue Gattung und Art dieser Familie ausgestorbener Tauchvögel beschrieben, die mit ihren kurzen Flügeln Vortrieb generierten. Coracoide sind äußerst aussagekräftige Knochen die am Mittelpunkt der Kräfte liegen, die auf die Schulter wirken und die an dieser Stelle eine wichtige Rolle in der Biomechanik der Vogel-Lokomotion spielen. Das Coracoid von Stemec hat einen ungewöhnlich schmalen, konischen Schaft der sich grundlegend von den breiten, flachen Coracoiden anderer Vogelgruppen unterscheidet.

Schlüsselwörter: Vogelfossil; British Columbia; neue Art; Nordpazifik; Oligozän; Plotopteridae

Translator: Eva Gebauer


563 arab

Translator: Ashraf M.T. Elewa



author1Gary Kaiser. Royal BC Museum, 675 Belleville Street, Victoria British Columbia, Canada V8W 9W2. This email address is being protected from spambots. You need JavaScript enabled to view it.

Gary Kaiser received his M.Sc. from Carleton University and worked for 30 years as a conservation biologist in the Migratory Birds Program of the Canadian Wildlife Service. Although he was most deeply involved with colonial seabirds of the temperate zone, his position gave him the opportunity to participate in projects on sandpipers and forest birds in southern Asia and South America. After retirement he returned to a childhood interest in paleontology and published Inner Bird: evolution and anatomy in 2007. He has subsequently participated in various projects involving reproductive activity in Cretaceous birds, bring his broad knowledge of modern birds and the principles of behavioral ecology to bear on the interpretation of fossils. For the past 15 years, he has been a research associate at the Royal BC Museum.


author2Junya Watanabe. Department of Geology and Mineralogy, Kyoto University, Sakyoku Kitashirakawa Oiwakecho, Kyoto, 606-8502 Japan. This email address is being protected from spambots. You need JavaScript enabled to view it.

Junya Watanabe is a Ph.D. candidate in the Department of Geology and Mineralogy, Kyoto University. He works primarily on the skeletal ontogeny of birds and its implications for morphological evolution. He has worked on several remote islands in Japan to collect onogenetic series of birds. His research interests include avian anatomy, paleontology, systematics, and evolution.


author3Marji Johns. Royal BC Museum, 675 Belleville Street, Victoria British Columbia, Canada V8W 9W2. This email address is being protected from spambots. You need JavaScript enabled to view it.

Marji received her M.Sc. from the University of Victoria and has worked for over 36 years in palaeontology and geoscience. Her multidisciplinary Cenozoic and Mesozoic research has resulted in publications on the Tofino Basin and Queen Charlotte Basin and Triassic biostratigraphy and geoscience in northeastern British Columbia. She is currently Collections Manager, Palaeontology at the Royal BC Museum, Victoria.



FIGURE 1. Stemec suntokum gen. et sp. nov. holotype right coracoid (RBCM.EH2014.032.0001.001) from the Sooke Formation, at the southwestern end of Vancouver Island, British Columbia as re-assembled after preparation. 1-4, dorsal (1), medial (2), lateral (3), ventral (4) aspects. Abbreviations: FACL, facies articularis clavicularis; FAHU, facies articularis humeralis; PRO, procoracoid.


FIGURE 2. Components of Stemec coracoid (RBCM.EH2014.032.0001.001). 1, cross-section of the shaft immediately caudal of the cranial portion (a-a of Figure 1.1); 2, cross-section cranial to the sternal segment (b-b of Figure 1.1); and 3, structural features near the sternal articulation.


FIGURE 3. Comparison of the acrocoracoid of Plotopterum joaquinensis (LACM 8927) (1 and 3) to Stemec suntokum (RBCM.EH2014.032.0001.001) (2 and 4). 1 and 2, dorsal aspects, 3 and 4, cranial aspects. See Figure 1 for abbreviations.


FIGURE 4. Map of Carmanah Group surface exposures along western Vancouver Island, British Columbia. A, Brooks Peninsula; B, Nootka (Tatchu Point, Nootka Island, Hesquiat Peninsula, and Flores Island); C, Carmanah (Pachena Point south to Owen Point); and D, Sooke (Port Renfrew south to Sooke) (for additional information, see Johns et al., 2012, figure 1).


FIGURE 5. Geological context of the Sooke Formation and Carmanah Group rocks, Vancouver Island based on data from Clark and Arnold (1923), Cameron (1980), Muller et al. (1981), Johns et al. (2012).


FIGURE 6. Cliff-beach exposure of the Sooke Formation. Letters indicate A, sandstone and shell-rich beds with burrows near the base; B, ripples; C, pebble conglomerate and shells; D, shell-rich coquinas and concretions; and E, Mytilus sp. and other shelly materials in cross-laminated and bedded sandstones. Rock hammer 26 cm, walking stick 115 cm.


FIGURE 7. Casts of coracoids in the Smithsonian Institution, Washington DC, referable to Copepteryx, one of the very large plotopterids from the Oligocene Ashiya Group of Kitakyushu, Japan. 1, Dorsal aspect of shaft lacking the omal portion and 2, Isolated omal portion, ventral aspect. Abbreviations: FASC, facies articularis scapularis; see Figure 1 for others.


FIGURE 8. Dimensional proportions of the Stemec coracoid (RBCM.EH2014.032.0001.001) and to two much larger plotopterids compared to cormorants, darters, and penguins. All other families of wing-propelled birds have larger values on both axes. Extinct examples are marked by a ‘+’ symbol.




TABLE 1. Temporal and geographic record of the Family Plotopteridae.

Genus and species Formation and location Age Source
Plotopterum joaquinensis

Pyramid Hill Sand M., Jewett Sand F., California

Late Oligocene
(24-25 Ma)

Howard (1969), Scheirer and Magoon (2007)

Plotopterum sp.

Yamanouchi M., Akeyo F., Japan

Early Miocene
(16-17 Ma)

Olson and Hasegawa (1985), Sasao et al. (2011)

Tonsala hildegardae

Pysht F., Washington

Early Oligocene

Olson (1980), Goedert and Cornish (2002)

T. buchanani

Pysht F., Washington

Makah F., Washington

Early Oligocene


Late Eocene
(ca. 34-35.3 Ma)
to early Oligocene

Goedert and Cornish (2002), Dyke et al. (2011)

Tonsala? sp.

Yamaga F., Japan

Early Oligocene
(ca. 30-32 Ma)

Ozaki and Hamasaki (1991), Olson and Hasegawa (1996)

Stemec suntokum

Sooke F., British Columbia

Late Oligocene


(24.1-24.8 Ma)

Prothero et al. (2008), this study

Copepteryx hexeris

Ainoshima F. (~Yamaga F.), Japan

Yamaga F., Japan

Asagai F., Japan

Early Oligocene


Early Oligocene
(ca. 30-32 Ma)


Early Oligocene

Ozaki and Hamasaki (1991), Okada (1992), Olson and Hasegawa (1996), Kurita (2004)

C. titan

Ainoshima F. (~Yamaga F.), Japan

Early Oligocene

Olson and Hasegawa (1996)

Hokkaidornis abashiriensis

Tokoro F., Japan

Late Oligocene


(24-29 Ma)

Sakurai et al. (2008)

Phocavis maritimus

Keasey F., Oregon

Late Eocene


(ca. 33.8 Ma)

Goedert (1988), Goedert and Cornish (2002)




TABLE 2. Proportional dimensions of coracoids among the Plotopteridae and modern waterbirds.

Taxa Source Length of head1 to total length (%) Width of sternal articulation to total length (%)
Stemec suntokum RBCM.EH
23.3 18.0
Copepteryx hexeris Hasegawa et al. (1979) 23.5 23.0
Tonsala(?) sp. Hasegawa et al. (1979) 21.5 21.0
Sula sula RBCM 23425 29.3 46.0
Anhinga anhinga UWBM 40957 23.6 26.0
A. melanogaster UWBM 62930 24.7 24.0
Stem cormorants
Oligocorax sp. Mayr (2015) 25.3 27.0
Nambashag billerooensis Worthy (2011) 25.6 23.9
Phalacrocorax harrisi Shufeldt (1915) 16.4 31.0
NHMUK 1973.1.13 13.45 30.0
NHMUK 1902.1.9.12 15.35 32.0
Phalacrocorax penicillatus RBCM 15002 25.7 24.0
RBCM 12071 25.6 25.0
P. pelagicus RBCM 23169 25.5 30.0
P. auritus RBCM 11279 24.3 28.0
Eudyptula minor UWBM 57505 30.0 29.0
Spheniscus magellanicus Livezey and Zusi (2006) 22.9 29.0
Spheniscus humboldti UWBM 57504 28.7 32.0
Pygoscelis antarctica UWBM 38043 34.9 34.0