Open Access
How to translate text using browser tools
5 October 2020 New Species of Plotopteridae (Aves) from the Oligocene Ashiya Group of Northern Kyushu, Japan
Tomoyuki Ohashi, Yoshikazu Hasegawa
Author Affiliations +
Abstract

Four coracoids belonging to the family Plotopteridae have been found from the Oligocene Ashiya Group, northern Kyushu, Japan. One coracoid is assigned to Copepteryx hexeris, and the other coracoids are assigned to new genera and species: Stenornis kanmonensis gen. et sp. nov., and Empeirodytes okazakii gen. et sp. nov., of the Plotopteridae. Stenornis and Empeirodytes share a synapomorphy: an elongate sulcus on the ventral surface of the facies articularis humeralis portion of the shaft, which is not observed in coracoids of other plotopterids. These new plotopterids reveal that the diversity of this group in the Oligocene Ashiya Group is higher than previously realized.

Introduction

The Plotopteridae are an extinct seabird family found in Eocene to Miocene marine sediments of the North Pacific Rim. The family was established by Howard (1969) based on an incomplete left coracoid of Plotopterum joaquinensis from California, U.S.A. Most of the 12 species of Plotopteridae that have been described consist of partially articulated skeletons or partial bones: Copepteryx hexeris from northern Kyushu, Japan; Hokkaidornis abashiriensis from Hokkaido, Japan; and Klallamornis abyssa, ?K. clarki, Olympidytes thieli, Tonsala buchanani, and T. hildegardae from Washington, U.S.A. (Olson, 1980; Olson and Hasegawa, 1996; Sakurai et al., 2008; Dyke et al., 2011; Mayr and Goedert, 2016). The other species have been described based on fragmentary or isolated materials: C. titan from northern Kyushu, Japan; Phocavis maritimus from Oregon, U.S.A.; Stemec suntokum from British Columbia, Canada; and T. cf. hildegardae and ?Tonsala sp. from Washington, U.S.A. (Goedert, 1988; Olson and Hasegawa, 1996; Kaiser et al., 2015; Mayr and Goedert, 2016).

The Oligocene Ashiya Group, which is widely distributed in northern Kyushu, is known for yielding many marine vertebrate fossils: shark teeth (Yabumoto, 1987; Tomita and Oji, 2010); the mysticete whale, Yamatocetus canaliculatus (Okazaki, 2012); a bony-toothed bird (Okazaki, 1989); and three species of the Plotopteridae: Copepteryx hexeris, C. titan, and Tonsala? sp. (Olson and Hasegawa, 1996). The present study compared the coracoids of other recently studied plotopterid birds to identify the taxonomic position of the new materials.

Institutional abbreviation.—KMNH, Kitakyushu Museum of Natural History and Human History, Kitakyushu, Japan.

Geological setting

All specimens have been found in the Oligoene Ashiya Group in and around Kitakyushu City, Fukuoka, Japan. The Ashiya Group is composed mainly of marine sediments and divided into the Yamaga, Norimatsu, Jinnobaru, Honjyo, and Waita formations in ascending order (Nakae et al., 1998; Tomita and Oji, 2010). The Yamaga Formation is distributed in Ainoshima and Kaijima Islands and consists of the outer shelf to shore face sediments (Tomita and Oji, 2010). The age of the Yamaga Formation at Ainoshima Island is late Early Oligocene (Tsuchi et al., 1987; Okada, 1992; Tomita and Oji, 2010). The age of the Jinnobaru Formation distributed in Kaijima Island is also estimated late Early Oligocene (Fukata et al., 2014).

Figure 1.

Left coracoid of Copepteryx hexeris (KMNH VP 600009). Above; photos and below; drawings. A, dorsal view; B, medial view; C, lateral view; D, ventral view. Abbreviations: fac, facies articularis clavicularis; fah, facies articularis humeralis; fas, facies articularis scapularis.

img-z2-1_285.jpg

Systematic paleontology

Order Aves Linnaeus, 1758
Family Plotopteridae Howard, 1969
Genus Copepteryx Olson and Hasegawa, 1996

  • Type species.—Copepteryx hexeris Olson and Hasegawa, 1996.

  • Figure 1

  • Material.—KMNH VP 600009, incomplete left coracoid, the extremitas omalis coracoidei portion is preserved.

  • Locality.—Kaijima Island, Kitakyushu, Fukuoka, Japan.

  • Horizon and age.—Yamaga Formation, Ashiya Group (late early Oligocene).

  • Emended diagnosis.—Olson and Hasegawa (1996) described the following characteristics as diagnostic features of Copepteryx hexeris: the scapular end of C. hexeris differs from that of Plotopterum and Tonsala in having an elongated glenoid facet with no distinct margin above the shaft, no sinuate sternal margin, ventral furcular facet, and relatively long and narrow coracohumeral surface (Olson, 1980).

  • In the present study, the following characters are added to the differential diagnosis (Table 1). A deeper longitudinal depression than most other protopterids is present on the dorsal surface at the facies articularis clavicularis. A well-developed ridge runs around the caudal side of the facies articularis clavicularis as a result of the deep depression of the recessus infra-acrocoracoideus. The position of the processsus lateralis is almost horizontal to the base (KMNH VP 200006 and fig. 1 in Olson and Hasegawa, 1996).

  • Description.—The extremitas omalis coracoidei portion of the left coracoid is preserved. The dorsoventral depth is approximately 9.0 mm and the mediolateral width is approximately 10.5 mm at the shaft at the caudal portion of the base of the procoracoid process. The cross-section of the shaft is ovate. The angle between the processus acrocoracoideus and the shaft is about 130°. The facies articularis clavicularis is almost flat although the ventral part of the acrocoracoid process is broken. A longitudinal depression is situated on the dorsal side of the facies articularis clavicularis. A deep depression of recessus infra-acrocoracoideus is hollowed along the caudal margin of the facies articularis clavicularis. The strong ridge-like margin is recognized between the facies articularis clavicularis and the shaft; therefore, the caudal end of the facies articularis clavicularis is everted. An acrocoracoid process curves slightly lateral or with a gradually ventromedial orientation and has no pneumaticity. The facies articularis humeralis is an almost smooth, flat, and craniocaudally elongated shape, but does not protrude to the lateral border of the processus acrocoracoideus. The spatulate-like procoracoid process is extended craniodorsally. An apical top of the procoracoid process extends medially. The facies articularis scapularis is well developed, concave, and has a distinctive margin around it. The caudal portion of the triosseal canal is convex. The ventral surface of the shaft at the region of the facies articularis humeralis is flat. A pit for biciptial attachment has not developed on the facies articularis clavicularis.

  • Remarks.—KMNH VP 600009 is identified as Copepteryx hexeris based on the following characteristics. The size and dorsoventral depth of the shaft are almost the same as that of the holotype of C. hexeris (KMNH VP 200006). A longitudinal depression on the dorsal side of the facies articularis clavicularis is also observed on the holotype. The spatulate-like procoracoid process is extended from the shaft craniodorsally as on the holotype. The coracoid of the holotype (KMNH VP 200006) shows two characteristics: the position of the processsus lateralis is almost horizontal to the base and the angulus medialis is rounded shape (fig. 1 in Olson and Hasegawa, 1996).

  • Table 1.

    List of the diagnostic features of the coracoid in the present specimens and other plotopterids.

    img-z3-2_285.gif

    Stenornis gen. nov.

  • Type species.—Stenornis kanmonensis sp. nov.

  • Diagnosis.—As for the type and only species; the size is almost the same as Copepteryx hexeris.

  • Etymology.—The genus name “steno (στενó)” means strait in Greek, “ornis” means bird in Greek. The plotopterid fossil localities; Ainoshima, Kaijima, and Hikoshima islands are located at the Kanmon Strait.

  • Stenornis kanmonensis sp. nov.
    Figures 2, 3

  • Holotype.—Almost complete left coracoid (KMNH VP 200003).

  • Synonymy.—Tonsala? sp., Olson and Hasegawa (1996).

  • Locality.—Hikoshima Island, Shimonoseki, Yamaguchi, Japan.

  • Horizon and age.—Jinnobaru Formation, Ashiya Group (late early Oligocene).

  • Differential diagnosis.—The large-sized plotopterid differs from other plotopterids in the following characteristics (Table 1). The angle between the processus acrocoracoideus and the shaft is about 95 to 100°. A craniocaudally elongated sulcus is situated on the ventral surface of the shaft. The facies articularis humeralis has the following combination characters: situating closer to the dorsal side and a slight depression on the middle. The weakly convex processus lateralis is positioned more toward the cranial portion of the shaft (upward by about 50°). The tip of the processus lateralis is gently peaked and faces laterally. In addition, the facies articularis clavicularis broader and more bean-shaped than in other plotopterids.

  • Etymology.—The specific epithet is from the fossil locality located at the Kanmon Strait.

  • Paratype.—Right coracoid (KMNH VP 600010: Figure 3) lacking processus lateralis; Ainoshima Island, Kitakyushu, Fukuoka, Japan; Ashiya Group (Oligocene); collected by Masahiro Sato.

  • Description.—The holotype of Stenornis kanmonensis is almost completely preserved, lacking only the apical tip of the procoracoid process. The dorsoventral depth of the shaft on the caudal portion of the base of procoracoid process is approximately 8.3 mm, and the mediolateral width is 13.3 mm in KMNH VP 200003; these values are approximately 8.5 mm and 12.9 mm in KMNH VP 600010. The shaft is elongated and flattened toward the extremitas sternalis coracoidei. The angle between the proc. acrocoracoideus and the shaft is about 95 to 100°. The facies articularis clavicularis is flat, slightly elongated, and triangular. A depression is not developed on the acrocoracoid process. No pneumaticity is observed on the caudal portion of the acrocoracoid process. The facies articularis humeralis has a craniocaudally elongated shape and a smooth surface that is concave at the center. From the ventral edge of the facies articularis humeralis, the surface slopes gradually on the ventral side of the shaft. The concavity of the facies articularis scapularis has a cup-like shape that is slightly elongated craniocaudally and is vertical to the shaft. The caudal portion of the triosseal canal is convex. A craniocaudally elongated sulcus is observed on the ventral surface of the facies articularis humeralis portion of the shaft. A moderate depression is recognized on the dorsal surface of the extrermitas sternalis coracoidei. The tip of the angulus medialis is broken off. A weakly convex processus lateralis is located toward the cranial portion of the shaft, and the tip faces laterally. The wide and flat labrum externum is located laterally opposite to the labrum internum. The craniocaudal positions of the labrum internum and labrum externum are situated parallel to each other. No pneumaticity is observed on the labrum internum.

  • Remarks.—Olson and Hasegawa (1996) classified KMNH VP 200003 as Tonsala? sp. because few referable specimens were known at that time. However, recent studies have reported new details of coracoids of Tonsala based on well-preserved materials (Dyke et al., 2011; Mayr and Goedert, 2016). Based on comparisons with these studies, Stenornis kanmonensis (KMNH VP 200003) differs from Tonsala and other plotopterids; comparative details are described below. Olson and Hasegawa (1996) classified it as Tonsala? sp. based on its size (larger than Tonsala hildegardae and smaller than Copepteryx hexeris) and morphology (different from C. hexeris in terms of the broader and proximal lateral process at the narrower sternal end). The coracoids of Tonsala, T. hildegardae, T. buchanani, and ?Tonsala sp. were described in previous studies (Olson, 1980; Dyke et al., 2011; Mayr and Goedert, 2016). Compared with T. hildegardae (Olson, 1980), the facies articularis humeralis of S. kanmonensis is situated more dorsally, and the ridge between the acrocoracoid process and the facies articularis humeralis is rounded. In addition, the orientation of the facies articularis scapularis is vertical and is dorsally situated in S. kanmonensis. No elongated sulcus is observed on the ventral surface of the facies articularis humeralis portion of the shaft in T. hildegardae. Two significant differences are recognized between S. kanmonensis and T. buchanani. In medial aspect, the shape of the facies articularis clavicularis of S. kanmonensis is a slightly elongated triangle, whereas that of T. buchanani is oval (Dyke et al., 2011). The facies articularis humeralis faces laterally in S. kanmonensis, but it is oriented obliquely toward the dorsal face in T. buchanani (Dyke et al., 2011). ?Tonsala sp. is smaller than T. hildegardae, and the shaft of S. kanmonensis is almost straight, whereas the shaft of ?Tonsala sp. is slightly inclined laterally from the facies articularis humeralis portion (Mayr and Goedert, 2016). The facies articularis scapularis of S. kanmonensis is more craniocaudally elongated and has a more rounded edge than that of ?Tonsala sp. (Mayr and Goedert, 2016).

  • Unlike the facies articularis clavicularis of Plotopterum joaquinensis, the facies articularis clavicularis of Stenornis kanmonensis has no sulcus. The craniocaudally elongated facies articularis humeralis differs from that of P. joaquinensis. The facies articularis scapularis of P. joaquinensis is slightly convex, but that of S. kanmonensis has a cup-like shape. In addition, there is a significant difference in the size of S. kanmonensis and P. joaquinensis. According to Kaiser et al. (2015), the facies articularis humeralis and facies articularis clavicularis of Stemec suntokum are almost circular facets, and most aspects of the facies articularis humeralis and facies articularis scapularis of Stemec suntokum are similar to Plotopterum, these features differ from those of S. kanmonensis. Sakurai et al. (2008) mentioned that Hokkaidornis abashiriensis differs from KMNH VP 200003 in terms of the shape of the angulus medialis and processus lateralis. The ventral side of the shaft of Klallamornis abyssa is essentially flat (Mayr and Goedert, 2016), but a slightly elongate sulcus is observed on the ventral surface of the facies articularis humeralis portion of the shaft of S. kanmonensis. There is no ridge-like linea intermuscularis, which has been observed in K. abyssa (Mayr and Goedert, 2016) on the ventral surface of the extremitas sternalis coracoidei portion of S. kanmonensis. The angulus medialis of K. abyssa is more rounded in shape (Mayr and Goedert, 2016, figs. 4C and 5A–D) than that of S. kanmonensis. All these comparisons indicate that S. kanmonensis differs from the known plotopterids.

  • Figure 2.

    Holotype of Stenornis kanmonensis gen. et sp. nov., left coracoid (KMNH VP 200003). Above; photos and below; drawings. A, dorsal view; B, medial view; C, lateral view; D, ventral view. Abbreviations: fac, facies articularis clavicularis; fah, facies articularis humeralis; fas, facies articularis scapularis; labr. ext. cor., labrum externum coracoidei; labr. int. cor., labrum internum coracoidei.

    img-z5-1_285.jpg

    Figure 3.

    Holotype and paratype of Stenornis kanmonensis gen. et sp. nov. Left; holotype (KMNH VP 200003) and right; paratype (KMNH VP 600010) in each photo. A, dorsal view; B, medial view; C, lateral view; D, ventral view; E, proximal view; F, distal view.

    img-z6-1_285.jpg

    Empeirodytes gen. nov.

  • Type species.—Empeirodytes okazakii sp. nov.

  • Diagnosis.—As for the type and only species.

  • Etymology.—The genus name “empeiros (Έµπειρoς)” means proficient in Greek, and “dytes (δύτης)” means diver in Greek.

  • Empeirodytes okazakii sp. nov.
    Figures 4, 5

  • Holotype.—Left coracoid lacking both sides of extremitas omalis coracoidei and extremitas sternalis coracoidei (KMNH VP 600011: Figure 4).

  • Locality.—Hiroiwa, Ainoshima Island, Kitakyushu, Fukuoka, Japan.

  • Horizon and age.—Ashiya Group (Oligocene).

  • Differential diagnosis.—Overall size is smaller than Copepteryx, Hokkaidornis, and Klallamornis and larger than Plotopterum and Stemec. The new species has the following two characteristics as the differential diagnosis (Table 1). A depression develops on the ventral surface of the facies articularis humeralis portion of the shaft. This depression is deeper and more prominent than in Stenornis. A sharply defined ridge runs along the caudal margin of the labrum internum. In addition, the base of the procoracoid process is thick and trapezoidal. The dorsoventral depth of the overall shaft is very thin.

  • Etymology.—The specific epithet is in honor of Yoshihiko Okazaki who has studied vertebrate fossils, including plotopterid birds from the Ashiya Group, Kitakyushu, Japan.

  • Paratype.—Right coracoid (KMNH VP 600012: Figure 5) lacking both sides of extremitas omalis coracoidei and extremitas sternalis coracoidei; Kaijima Island, Kitakyushu, Fukuoka, Japan; Ashiya Group (Oligocene).

  • Description.—KMNH VP 600011 and 600012 are preserved without the extremitas omalis coracoidei and the lateral side of the extremitas sternalis coracoidei. The dorsoventral depth is approximately 5.3 mm and the mediolateral width is approximately 9.0 mm in KMNH VP 600011, and these values are approximately 4.5 mm and 7.2 mm in KMNH VP 600012 for each shaft on the caudal portion of the base of the procoracoid process. The shaft is a very flattened oval shape in cross-section and craniocaudally elongated. The caudal portion of the triosseal canal is convex and swollen in KMNH VP 600012. The procoracoid process is strongly rolled back medially and in the direction of extremitas omalis coracoidei, and its base is thicker and trapezoidal. An apical tip of the procoracoid process extends medially. The surface of the facies articularis scapularis is smooth and gently concave. A clear depression is present on the ventral surface of the facies articularis humeralis portion of the shaft. The surface of the facies articularis humeralis is an almost smooth, flat, and craniocaudally elongated oval shape, and a sharp gap runs along the ventral side of the facies articularis humeralis in KMNH VP 600012. The dorsoventral depth of the overall shaft is very thin. A slight depression is recognized on the dorsal surface of the extremitas sternalis coracoidei. The angulus medialis is preserved, but the processus lateralis is not preserved. The tip of the angulus medialis is sharp. The labrum externum coracoidei is turned outward distinctly. The labrum internum coracoidei has a distinct ridge on the caudal edge elongated from the angulus medialis. The sharply defined ridge runs along the caudal margin of the labrum internum. The wide and narrow labrum externum is located laterally to the labrum internum. The craniocaudal position of the labrum internum and labrum externum is relatively equal.

  • Remarks.—Empeirodytes okazakii significantly differs from the coracoids of other plotopterids in the following features: sulcus on the ventral side of the facies articularis humeralis portion of the shaft and sharply ridge on the caudal margin of the labrum internum. A spur-like sharp angulus medialis differs from the rounded edge of that of Copepteryx hexeris and the gradually sloped edge of Stenornis kanmonensis (KMNH VP 200003). This spur-like sharp angulus medialis also differs from Klallamornis abyssa, which has a rounded margin of the angulus medialis (fig. 4C and fig. 5 in Mayr and Goedert, 2016). In addition, there is a clear difference in the shape of the labrum internum between E. okazakii and Stenornis kanmonensis. For the caudal margin of the labrum internum, E. okazakii has a high and sharp ridge, but Stenornis kanmonensis has a low and rounded ridge. The smooth and gently concave facies articularis scapularis of E. okazakii differs from the cup-like facies articularis scapularis of Tonsala. As compared to the caudal view of Stemec suntokum in fig. 2.3 of Kaiser et al. (2015), the labrum internum and the labrum externum of E. okazakii are more developed than those of Stemec suntokum. The angulus medialis of Hokkaidornis abashiriensis is situated at the margin of the sternal end from the caudal view (fig. 2 in Sakurai et al., 2008), but that of E. okazakii is located along the middle line of the sternal end from the caudal view.

  • Figure 4.

    Holotype of Empeirodytes okazakii gen. et sp. nov., left coracoid (KMNH VP 600011). Above; photos and below; drawings. A, dorsal view; B, medial view; C, lateral view; D, ventral view; E, distal view. Abbreviations: fas, facies articularis scapularis; labr. ext. cor., labrum externum coracoidei; labr. int. cor., labrum internum coracoidei.

    img-z8-1_285.jpg

    Figure 5.

    Paratype of Empeirodytes okazakii gen. et sp. nov., right coracoid (KMNH VP 600012). Above; photos and below; drawings. A, dorsal view; B, medial view; C, lateral view; D, ventral view. Abbreviations: fah, facies articularis humeralis; fas, facies articularis scapularis.

    img-z9-1_285.jpg

    Discussion

    The ratio of dorsoventral depth to mediolateral width on the caudal to procoracoid process of the shaft is less than 1.0 in the Plotopteridae (Kaiser et al., 2015). By this criterion, the present coracoid specimens belong to that family. As in previous taxonomic studies of plotopterid birds, the coracoid can be a useful and diagnostic element for defining plotopterid birds at the species level. The holotypes of Plotopterum joaquinensis and Stemec suntokum are coracoids (Howard, 1969; Kaiser et al., 2015). Diagnoses of other plotopterids also have included coracoid characteristics: the coracoid of Tonsala hildegardae is compared with that of P. joaquinensis (Olson, 1980); one of the diagnostic features of Copepteryx hexeris is the scapular end of the coracoid as compared with P. joaquinensis and T. hildegardae (Olson and Hasegawa, 1996); the sternal end of the coracoid of Hokkaidornis abashiriensis is compared with those of C. hexeris and Tonsala? sp. (Sakurai et al., 2008); and some morphological features of the coracoid of Klallamornis abyssa are included in the diagnosis (Mayr and Goedert, 2016). In addition, Sakurai et al. (2008) mentioned that a straight and elongate coracoid shaft is one of the characteristics of the Plotopteridae. A recent phylogenetic analysis of Pelecaniformes including the Plotopteridae indicates that two characteristics of the coracoid are synapomorphies of the Plotopteridae (Char. no. 176: relative convexity of caudal portion of the triosseal canal; distinctly convex and swollen and char. no. 178: relative orientation of facies articularis clavicularis; caudal (sternal) end of facet is strongly everted, enhancing the cranial and medial components to its orientation; Smith, 2010). These previous studies show that coracoid characteristics are among those that define the family Plotopteridae and aid in differentiation at the species level.

    The present study classifies five coracoids from the Ashiya Group into three genera and species including two new genera and species. Other than the morphological differences, some studies of plotopterids refer to overall size as one of the diagnoses (Dyke et al., 2011; Mayr and Goedert, 2016). Matsuoka et al. (2009) also mentioned that at least four size-groups are recognized in plotopterid fossils from northern Kyushu, and each size group is divided into more than two morphological types. As compared to the size of the present specimens, roughly two different sizes are recognized; the larger type includes Copepteryx hexeris and Stenornis kanmonensis, and the smaller type includes Empeirodytes okazakii (Figure 6). These different sized groups in the present study are consistent with the previous study and confirm the establishment of a new genus and species with the morphological differences in the present study.

    Stenornis and Empeirodytes have a distinctive feature that is an elongate sulcus on the ventral surface of the facies articularis humeralis portion of the shaft. That of Stenornis is a slight depression, but that of Empeirodytes is a deep depression. It is unknown whether the depression is a muscle attachment, but a part of m. supracoracoideus might be related to, or attached on the depression. Usually, the origin of m. supracoracoideus is on the sternum and ventral surface of the coracoid, and m. supracoracoideus runs through the triosseal canal to the humerus. According to Ando and Fukata (2018), the m. supracoracoideus of plotopterid birds was large and functioned in their powerful upstroke during diving. It is suggested that Stenornis and Empeirodytes have more robust m. supracoracoideus than that of the other plotopterids, or the m. supracoracoideus of Stenornis and Empeirodytes is attached more strongly than that of the other plotopterids. Because m. supracoracoideus abducts the humerus, Stenornis and Empeirodytes might have had different or better swimming abilities than the other plotopterids.

    Figure 6.

    The size comparison of the specimens (A to G) from dorsal views and set in line (dash line) at the base of the procoracoid process. A, Copepteryx hexeris (KMNH VP 600009); B, Stenornis kanmonensis (KMNH VP 200003); C, S. kanmonensis (KMNH VP 600010); D, Empeirodytes okazakii (KMNH VP 600011); E, E. okazakii (KMNH VP 600012); F, Left coracoid of Sula leucogaster (KMNH VR 700002). G, Left coracoid of Phalacrocorax capillatus (KMNH VR 700009). The morphological comparison of the specimens (H) by fitting the size for the same width at the base of the procoracoid process (gray line); left to right; C. hexeris (KMNH VP 600009), S. kanmonensis (KMNH VP 200003 and KMNH VP 600010), E. okazakii (KMNH VP 600011 and KMNH VP 600012), Sula leucogaster (KMNH VR 700002), P. capillatus (KMNH VR 700009).

    img-z11-1_285.jpg

    Eight species of plotopterid birds have been found from the Eocene-Miocene sediments of the northeastern Pacific Rim in previous studies. In the northwestern Pacific Rim, Copepteryx hexeris, C. titan, H. abashiriensis, and Tonsala? sp. were the only known Plotopteridae so far. However, it is revealed that two new species, including Tonsala? sp. as a new species of the Plotopteridae, occurred in the Oligocene Ashiya Group in the present study. This new information indicates that plotopterid birds prospered in the northwestern Pacific Rim as well as the northeastern Pacific Rim.

    Acknowledgements

    We are grateful to Yoshihiko Okazaki (Kitakyushu Museum of Natural History and Human History, KMNH), Takayoshi Harada (Kitakyushu Natural History Society of KMNH, KNHS), Tsutomu Ikeda (KNHS), Masahiro Sato (KNHS), the late Takashi Sotsuka (KNHS) and the late Masamichi Ota (KMNH) for their collection and preparation of the specimens over the years. We sincerely thank Yoshitaka Yabumoto (KMNH) for constant encouragement, review of an early draft of this manuscript, and valuable comments. We also thank Mark S. Florence (Smithsonian National Museum of Natural History) for permitting the observation of plotopterid materials in the collections at NMNH. We would like to thank Nathan Smith (Natural History Museum of Los Angeles County) and Gareth Dyke (University of Debrecen) for their helpful reviews, and also thank associate editor, Makoto Manabe (National Museum of Nature and Science) for his helpful suggestions that greatly helped to improve the manuscript. This work was supported by JSPS KAKENHI Grant Number 17H02028.

    References

    1.

    Ando, T. and Fukata, K., 2018: A well-preserved partial scapula from Japan and the reconstruction of the triosseal canal of plotopterids. PeerJ , 6: e5391. https://doi.org/10.7717/peerj.5391Google Scholar

    2.

    Dyke, G. J., Wang, X. and Habib, M. B., 2011: Fossil plotopterid seabirds from the Eo-Oligocene of the Olympic Peninsula (Washington State, USA): Descriptions and functional morphology. PLos ONE , 6(10): e25672, https://doi.org/10.1371/journal.pone.0025672Google Scholar

    3.

    Fukata, K., Kameya, A., Takakuwa, Y. and Fujii, K., 2014: Discovery of the teeth remains Parotodus benedeni from the Oligocene Ashiya Group in the Hikoshima Nishiyama Area, Shimonoseki City, Yamaguchi Prefecture, southwest Japan. Bulletin of the Yamaguchi Museum , vol. 40, p. 9–20. ( in Japanese with English abstract ) Google Scholar

    4.

    Goedert, J. L., 1988: A new Late Eocene species of Plotopteridae (Aves: Pelecaniformes) from northwestern Oregon. Proceedings of the California Academy of Sciences , vol. 45, p. 97–102. Google Scholar

    5.

    Howard, H., 1969: A new avian fossil from Kern County, California. Condor , vol. 71, p. 68–69. Google Scholar

    6.

    Kaiser, G., Watanabe, J. and Johns, M., 2015: A new member of the family Plotopteridae (Aves) from the late Oligocene of British Columbia, Canada. Palaeontologia Electronica , 18.3.52A, p. 1–18. Google Scholar

    7.

    Linnaeus, C., 1758: Systema naturae per regna tria naturae. Secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis . Editio decima 1, 824 p. Laurentii Salvii, Stockholm. Google Scholar

    8.

    Matsuoka, H., Hasegawa, Y. and Okazaki, Y., 2009: The diversity of the Paleogene diving birds (Plotopteridae, Pelecaniformes) from northern Kyushu area, western Japan. International symposium on terrestrial Paleogene biota and stratigraphy of eastern Asia, Abstracts and guidebook , p. 29–30. Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing. Google Scholar

    9.

    Mayr, G. and Goedert, J. L., 2016: New late Eocene to Oligocene remains of the flightless, penguin-like plotopterids (Aves, Plotopteridae) from western Washington State, U.S.A.. Journal of Vertebrate Paleontology , vol. 36, https://doi.org/10.1080/02724634.2016.1163573Google Scholar

    10.

    Nakae, S., Ozaki, M., Ota, M., Yabumoto, Y., Matsuura, H. and Tomita, S., 1998: Geology of the Kokura District with Geological Sheet Map at 1:50,000 , 126 p. Geological Survey of Japan, Tsukuba. ( in Japanese with English abstractGoogle Scholar

    11.

    Okada, H., 1992: Calcareous nannofossils and biostratigraphy of the Paleogene sequences of the northern Kyushu, Japan. Journal of the Geological Society of Japan , vol. 98, p. 509–528. Google Scholar

    12.

    Okazaki, Y., 1989: An occurrence of fossil bony-toothed bird (Odontopterygiformes) from the Ashiya Group (Oligocene), Japan. Bulletin of the Kitakyushu Museum of Natural History , no. 9, p. 123–126. Google Scholar

    13.

    Okazaki, Y., 2012: A new mysticete from the upper Oligocene Ashiya Group, Kyushu, Japan and its significance to mysticete evolution. Bulletin of the Kitakyushu Museum of Natural History and Human History, Series A (Natural History) , no. 10, p. 129–152. Google Scholar

    14.

    Olson, S. L., 1980: A new genus of penguin-like pelecaniform bird from the Oligocene of Washington (Pelecaniformes: Plotopteridae). Natural History Museum of Los Angeles County Contributions in Science , vol. 330, p. 51–57. Google Scholar

    15.

    Olson, S. L. and Hasegawa, Y., 1996: A new genus and two species of gigantic Plotopteridae from Japan (Aves: Pelecaniformes). Journal of Vertebrate Paleontology , vol. 16, p. 742–751. Google Scholar

    16.

    Sakurai, K., Kimura, M. and Katoh, T., 2008: A new penguin-like bird (Pelecaniformes: Plotopteridae) from the Late Oligocene Tokoro Formation, northeastern Hokkaido, Japan. Oryctos , vol. 7, p. 83–94. Google Scholar

    17.

    Smith, N. D., 2010: Phylogenetic analysis of Pelecaniformes (Aves) based on osteological data: Implications for waterbird phylogeny and fossil calibration studies. PLoS ONE , 5(10): e13354, https://doi.org/10.1371/journal.pone.0013354Google Scholar

    18.

    Tomita, T. and Oji, T., 2010: Habitat reconstruction of Oligocene elasmobranchs from Yamaga Formation, Ashiya Group, western Japan. Paleontological Research , vol. 14, p. 69–80. Google Scholar

    19.

    Tsuchi, R., Shuto, T. and Ibaraki, M., 1987: Geologic ages of the Ashiya Group, North Kyushu from a viewpoint of planktonic foraminifera. Reports of Faculty of Science, Shizuoka University , vol. 21, p. 109–119. Google Scholar

    20.

    Yabumoto, Y., 1987: Oligocene lamnid shark of the genus Carcharodon from Kitakyushu, Japan. Bulletin of the Kitakyushu Museum of Natural History , no. 6, p. 239–264. Google Scholar

    Author contributions

    T. O. made the main contributions on this study. All authors compared the specimens and discussed the specimen affinities in this study. T. O. mainly wrote the manuscript and Y.H. edited the manuscript.

    © by the Palaeontological Society of Japan
    Tomoyuki Ohashi and Yoshikazu Hasegawa "New Species of Plotopteridae (Aves) from the Oligocene Ashiya Group of Northern Kyushu, Japan," Paleontological Research 24(4), 285-297, (5 October 2020). https://doi.org/10.2517/2020PR005
    Received: 24 March 2019; Accepted: 31 October 2019; Published: 5 October 2020
    KEYWORDS
    Ashiya Group
    Aves
    coracoid
    Oligocene
    Plotopteridae
    Back to Top