Naoki Kohno - Academia.edu (original) (raw)
Papers by Naoki Kohno
Biosurface and Biotribology, 2017
Paleontological Research, 1997
A mammalian tooth from the lower Middle Miocene Korematsu Formation (ca. 16.3-15.6 Ma) within the... more A mammalian tooth from the lower Middle Miocene Korematsu Formation (ca. 16.3-15.6 Ma) within the Bihoku Group in Shobara City, Hiroshima Prefecture, southwestern Japan, is d~ribed and identified as a right upper first molar of the amphicyonid carnivore Ysengrinia sp. This is the first amphicyonid to be described from Far East Asia and it provides additional evidence for the carnivoran faunal connections between Europe-Asia-North America during the Early and early Middle Miocene.
Bulletin of the National Science Museum. Series C, Geology & paleontology, 1993
Royal Society Open Science, 2021
Little is known about how mammalian biogeography on islands was affected by sea-level fluctuation... more Little is known about how mammalian biogeography on islands was affected by sea-level fluctuations. In the Japanese Archipelago, brown bears ( Ursus arctos ) currently inhabit only Hokkaido, the northern island, but Pleistocene fossils indicate a past distribution throughout Honshu, Japan's largest island. However, the difficulty of recovering ancient DNA from fossils in temperate East Asia has limited our understanding of their evolutionary history. Here, we analysed mitochondrial DNA from a 32 500-year-old brown bear fossil from Honshu. Our results show that this individual belonged to a previously unknown lineage that split approximately 160 Ka from its sister lineage, the southern Hokkaido clade. This divergence time and fossil record suggest that brown bears migrated from the Eurasian continent to Honshu at least twice; the first population was an early-diverging lineage (greater than 340 Ka), and the second migrated via Hokkaido after approximately 160 Ka, during the ice a...
Biological Journal of the Linnean Society, 2021
Cetaceans (whales and dolphins) have some of the largest and most complex brains in the animal ki... more Cetaceans (whales and dolphins) have some of the largest and most complex brains in the animal kingdom. When and why this trait evolved remains controversial, with proposed drivers ranging from echolocation to foraging complexity and high-level sociality. This uncertainty partially reflects a lack of data on extinct baleen whales (mysticetes), which has obscured deep-time patterns of brain size evolution in non-echolocating cetaceans. Building on new measurements from mysticete fossils, we show that the evolution of large brains preceded that of echolocation, and subsequently followed a complex trajectory involving several independent increases (e.g. in rorquals and oceanic dolphins) and decreases (e.g. in right whales and ‘river dolphins’). Echolocating whales show a greater tendency towards large brain size, thus reaffirming cognitive demands associated with sound processing as a plausible driver of cetacean encephalization. Nevertheless, our results suggest that other factors suc...
A new species of an extinct dolphin belonging to the kentriodontids, i.e., Kentriodon sugawarai s... more A new species of an extinct dolphin belonging to the kentriodontids, i.e., Kentriodon sugawarai sp. nov., is described from the upper lower to lowest middle Miocene Kadonosawa Formation in Ninohe City, Iwate Prefecture, northern Japan. The holotype of Kentriodon sugawarai sp. nov., consists of a partial skull with ear bones, mandibular fragments, and some postcranial bones. This new species shares five unique characters with other species of Kentriodon. In addition, the new species differs from other species of the genus in displaying a narrow width of the squamosal lateral to the exoccipital in posterior view, the dorsolateral edge of the opening of the ventral infraorbital foramen that is formed by the maxilla and the lacrimal or the jugal, and at least three anterior dorsal infraorbital foramina. Our phylogenetic analysis based on 393 characters for 103 Odontoceti taxa yielded a consensus tree showing all previously identified kentriodontids as a monophyletic group that comprises...
Paleontological Research
Abstract. The late Palaeogene represents a crucial time in cetacean evolution that witnessed the ... more Abstract. The late Palaeogene represents a crucial time in cetacean evolution that witnessed the origin of modern baleen and toothed whales (Neoceti) from their “archaeocete” ancestors. So far, this fundamental transition has been discussed mainly in terms of cranial morphology, whereas descriptions of postcranial material remain rare. Here, we report a small cetacean humerus from the Nichinan Group (lower Oligocene to lower Miocene), Kushima City, Miyazaki Prefecture, southern Kyushu, Japan. Our specimen resembles archaeocete humeri in being proximodistally elongate and in retaining a distinct deltoid ridge, but shares with neocetes the defining feature of an immobilised elbow joint. It resembles most Oligocene odontocetes in its small size and in lacking a notch marking the position of the distal epiphysis, and is furthermore similar to the enigmatic Microzeuglodon in having a transversely compressed shaft. A morphometric analysis based on five linear measurements, however, fails to cluster our specimen with any other known group of cetaceans, indicating that it is not easily referable to either basal mysticetes or odontocetes. Therefore, we here classify it as Neoceti incertae sedis.
A new species of a beaked whale that belongs to the extant genus Berardius is described from the ... more A new species of a beaked whale that belongs to the extant genus Berardius is described from the Middle to Late Miocene boundary age Tsurushi Formation (ca 12.3–11.5 Ma) on the Sado Island, Niigata Prefecture, Japan. The new species, Berardius kobayashii sp. nov. represents the oldest record of this genus and provides a minimum age for the emergence of this extant genus. Berardius kobayashii sp. nov. has the following generic characters: the ratio between the width of the premaxillary crests and the width of the premaxillary sac fossae is 1.0–1.25, nodular frontals make isolated protuberance on the posterior part of the vertex. Among the species within the genus, B. kobayashii sp. nov. shares a unique character with B. minimus: the apices of the left and right hamular processes of the pterygoids contact medially, forming together a posteriorly directed medial point. In addition, B. kobayashii sp. nov. displays a unique combination of the following characters: it is extremely small i...
Biological Journal of the Linnean Society, 2021
Cetaceans (whales and dolphins) have some of the largest and most complex brains in the animal ki... more Cetaceans (whales and dolphins) have some of the largest and most complex brains in the animal kingdom. When and why this trait evolved remains controversial, with proposed drivers ranging from echolocation to foraging complexity and high-level sociality. This uncertainty partially reflects a lack of data on extinct baleen whales (mysticetes), which has
obscured deep-time patterns of brain size evolution in non-echolocating cetaceans. Building on new measurements from mysticete fossils, we show that the evolution of large brains preceded that of echolocation, and subsequently followed a complex trajectory involving several independent increases (e.g. in rorquals and oceanic dolphins) and decreases (e.g. in right whales and ‘river dolphins’). Echolocating whales show a greater tendency towards large brain size, thus reaffirming cognitive demands associated with sound processing as a plausible driver of cetacean encephalization. Nevertheless, our results suggest that other factors such as sociality were also important.
PeerJ
The extant genera of fur seals and sea lions of the family Otariidae (Carnivora: Pinnipedia) are ... more The extant genera of fur seals and sea lions of the family Otariidae (Carnivora: Pinnipedia) are thought to have emerged in the Pliocene or the early Pleistocene in the North Pacific. Among them, the Steller sea lion (Eumetopias jubatus) is the largest and distributed both in the western and eastern North Pacific. In contrast to the limited distribution of the current population around the Japanese Islands that is now only along the coast of Hokkaido, their fossil records have been known from the middle and late Pleistocene of Honshu Island. One such important fossil specimen has been recorded from the upper lower Pleistocene Omma Formation (ca. 1.36–0.83 Ma) in Kanazawa, Ishikawa Prefecture, Japan, which now bears the institutional number GKZ-N 00001. Because GKZ-N 00001 is the earliest fossil having been identified as a species of the sea lion genus Eumetopias, it is of importance to elucidate the evolutionary history of that genus. The morphometric comparisons were made among 51 ...
Frontiers in Ecology and Evolution
BULLETIN OF THE GEOLOGICAL SURVEY OF JAPAN
Current biology : CB, Jan 9, 2017
The pygmy right whale, Caperea marginata, is the most enigmatic living whale. Little is known abo... more The pygmy right whale, Caperea marginata, is the most enigmatic living whale. Little is known about its ecology and behaviour, but unusual specialisations of visual pigments [1], mitochondrial tRNAs [2], and postcranial anatomy [3] suggest a lifestyle different from that of other extant whales. Geographically, Caperea represents the only major baleen whale lineage entirely restricted to the Southern Ocean. Caperea-like fossils, the oldest of which date to the Late Miocene, are exceedingly rare and likewise limited to the Southern Hemisphere [4], despite a more substantial history of fossil sampling north of the equator. Two new Pleistocene fossils now provide unexpected evidence of a brief and relatively recent period in geological history when Caperea occurred in the Northern Hemisphere (Figure 1A,B).
Die Naturwissenschaften, 2016
Living baleen whales (Mysticeti) include the world's largest animals to have ever lived-blue ... more Living baleen whales (Mysticeti) include the world's largest animals to have ever lived-blue whales (Balaenoptera musculus) can reach more than 30 m. However, the gigantism in baleen whales remains little explored. Here, we compiled all published stem mysticetes from the Eocene and Oligocene and then mapped the estimated body size onto different phylogenies that suggest distinct evolutionary histories of baleen whales. By assembling all known stem baleen whales, we present three novel findings in early mysticete evolution. Results show that, regardless of different phylogenetic scenarios, large body size (more than 5-m long) evolved multiple times independently in their early evolutionary history. For example, the earliest known aetiocetid (Fucaia buelli, 33-31 Ma) was small in size, about 2 m, and a later aetiocetid (Morawanocetus-like animal, 26-23 Ma) can reach 8-m long-almost four times the size of Fucaia buelli-suggesting an independent gigantism in the aetiocetid lineage. ...
Kimura et al (2015): Bulletin of the Gunma Museum of Natural History, (19):39-48. Abstract: We re... more Kimura et al (2015): Bulletin of the Gunma Museum of Natural History, (19):39-48. Abstract: We report a new fossil mysticete, previously referred to as the "Shimajiri whale" (e.g., Adaniya, 1977), from the Upper Miocene of Miyako Island, Okinawa, Japan. The new material was recovered from the Okamishima Formation (Shimajiri Group), which is correlative with foraminiferal Zone N17. Very little cetacean material has been described from the Ryukyu Islands and the wider area of Southeast Asia, making this an important find. The specimen consists of a fragmentary cranium including both periotics and the left tympanic bulla, but missing the rostrum and the left zygomatic and supraorbital processes. The surfaces of most of the bones are badly eroded and reveal little sutural detail. Nevertheless, the specimen can be confidently identified as a balaenopterid based on (1) its abruptly depressed supraorbital process, (2) cranially elongated pars cochlearis and (3) the overlap of the...
Biosurface and Biotribology, 2017
Paleontological Research, 1997
A mammalian tooth from the lower Middle Miocene Korematsu Formation (ca. 16.3-15.6 Ma) within the... more A mammalian tooth from the lower Middle Miocene Korematsu Formation (ca. 16.3-15.6 Ma) within the Bihoku Group in Shobara City, Hiroshima Prefecture, southwestern Japan, is d~ribed and identified as a right upper first molar of the amphicyonid carnivore Ysengrinia sp. This is the first amphicyonid to be described from Far East Asia and it provides additional evidence for the carnivoran faunal connections between Europe-Asia-North America during the Early and early Middle Miocene.
Bulletin of the National Science Museum. Series C, Geology & paleontology, 1993
Royal Society Open Science, 2021
Little is known about how mammalian biogeography on islands was affected by sea-level fluctuation... more Little is known about how mammalian biogeography on islands was affected by sea-level fluctuations. In the Japanese Archipelago, brown bears ( Ursus arctos ) currently inhabit only Hokkaido, the northern island, but Pleistocene fossils indicate a past distribution throughout Honshu, Japan's largest island. However, the difficulty of recovering ancient DNA from fossils in temperate East Asia has limited our understanding of their evolutionary history. Here, we analysed mitochondrial DNA from a 32 500-year-old brown bear fossil from Honshu. Our results show that this individual belonged to a previously unknown lineage that split approximately 160 Ka from its sister lineage, the southern Hokkaido clade. This divergence time and fossil record suggest that brown bears migrated from the Eurasian continent to Honshu at least twice; the first population was an early-diverging lineage (greater than 340 Ka), and the second migrated via Hokkaido after approximately 160 Ka, during the ice a...
Biological Journal of the Linnean Society, 2021
Cetaceans (whales and dolphins) have some of the largest and most complex brains in the animal ki... more Cetaceans (whales and dolphins) have some of the largest and most complex brains in the animal kingdom. When and why this trait evolved remains controversial, with proposed drivers ranging from echolocation to foraging complexity and high-level sociality. This uncertainty partially reflects a lack of data on extinct baleen whales (mysticetes), which has obscured deep-time patterns of brain size evolution in non-echolocating cetaceans. Building on new measurements from mysticete fossils, we show that the evolution of large brains preceded that of echolocation, and subsequently followed a complex trajectory involving several independent increases (e.g. in rorquals and oceanic dolphins) and decreases (e.g. in right whales and ‘river dolphins’). Echolocating whales show a greater tendency towards large brain size, thus reaffirming cognitive demands associated with sound processing as a plausible driver of cetacean encephalization. Nevertheless, our results suggest that other factors suc...
A new species of an extinct dolphin belonging to the kentriodontids, i.e., Kentriodon sugawarai s... more A new species of an extinct dolphin belonging to the kentriodontids, i.e., Kentriodon sugawarai sp. nov., is described from the upper lower to lowest middle Miocene Kadonosawa Formation in Ninohe City, Iwate Prefecture, northern Japan. The holotype of Kentriodon sugawarai sp. nov., consists of a partial skull with ear bones, mandibular fragments, and some postcranial bones. This new species shares five unique characters with other species of Kentriodon. In addition, the new species differs from other species of the genus in displaying a narrow width of the squamosal lateral to the exoccipital in posterior view, the dorsolateral edge of the opening of the ventral infraorbital foramen that is formed by the maxilla and the lacrimal or the jugal, and at least three anterior dorsal infraorbital foramina. Our phylogenetic analysis based on 393 characters for 103 Odontoceti taxa yielded a consensus tree showing all previously identified kentriodontids as a monophyletic group that comprises...
Paleontological Research
Abstract. The late Palaeogene represents a crucial time in cetacean evolution that witnessed the ... more Abstract. The late Palaeogene represents a crucial time in cetacean evolution that witnessed the origin of modern baleen and toothed whales (Neoceti) from their “archaeocete” ancestors. So far, this fundamental transition has been discussed mainly in terms of cranial morphology, whereas descriptions of postcranial material remain rare. Here, we report a small cetacean humerus from the Nichinan Group (lower Oligocene to lower Miocene), Kushima City, Miyazaki Prefecture, southern Kyushu, Japan. Our specimen resembles archaeocete humeri in being proximodistally elongate and in retaining a distinct deltoid ridge, but shares with neocetes the defining feature of an immobilised elbow joint. It resembles most Oligocene odontocetes in its small size and in lacking a notch marking the position of the distal epiphysis, and is furthermore similar to the enigmatic Microzeuglodon in having a transversely compressed shaft. A morphometric analysis based on five linear measurements, however, fails to cluster our specimen with any other known group of cetaceans, indicating that it is not easily referable to either basal mysticetes or odontocetes. Therefore, we here classify it as Neoceti incertae sedis.
A new species of a beaked whale that belongs to the extant genus Berardius is described from the ... more A new species of a beaked whale that belongs to the extant genus Berardius is described from the Middle to Late Miocene boundary age Tsurushi Formation (ca 12.3–11.5 Ma) on the Sado Island, Niigata Prefecture, Japan. The new species, Berardius kobayashii sp. nov. represents the oldest record of this genus and provides a minimum age for the emergence of this extant genus. Berardius kobayashii sp. nov. has the following generic characters: the ratio between the width of the premaxillary crests and the width of the premaxillary sac fossae is 1.0–1.25, nodular frontals make isolated protuberance on the posterior part of the vertex. Among the species within the genus, B. kobayashii sp. nov. shares a unique character with B. minimus: the apices of the left and right hamular processes of the pterygoids contact medially, forming together a posteriorly directed medial point. In addition, B. kobayashii sp. nov. displays a unique combination of the following characters: it is extremely small i...
Biological Journal of the Linnean Society, 2021
Cetaceans (whales and dolphins) have some of the largest and most complex brains in the animal ki... more Cetaceans (whales and dolphins) have some of the largest and most complex brains in the animal kingdom. When and why this trait evolved remains controversial, with proposed drivers ranging from echolocation to foraging complexity and high-level sociality. This uncertainty partially reflects a lack of data on extinct baleen whales (mysticetes), which has
obscured deep-time patterns of brain size evolution in non-echolocating cetaceans. Building on new measurements from mysticete fossils, we show that the evolution of large brains preceded that of echolocation, and subsequently followed a complex trajectory involving several independent increases (e.g. in rorquals and oceanic dolphins) and decreases (e.g. in right whales and ‘river dolphins’). Echolocating whales show a greater tendency towards large brain size, thus reaffirming cognitive demands associated with sound processing as a plausible driver of cetacean encephalization. Nevertheless, our results suggest that other factors such as sociality were also important.
PeerJ
The extant genera of fur seals and sea lions of the family Otariidae (Carnivora: Pinnipedia) are ... more The extant genera of fur seals and sea lions of the family Otariidae (Carnivora: Pinnipedia) are thought to have emerged in the Pliocene or the early Pleistocene in the North Pacific. Among them, the Steller sea lion (Eumetopias jubatus) is the largest and distributed both in the western and eastern North Pacific. In contrast to the limited distribution of the current population around the Japanese Islands that is now only along the coast of Hokkaido, their fossil records have been known from the middle and late Pleistocene of Honshu Island. One such important fossil specimen has been recorded from the upper lower Pleistocene Omma Formation (ca. 1.36–0.83 Ma) in Kanazawa, Ishikawa Prefecture, Japan, which now bears the institutional number GKZ-N 00001. Because GKZ-N 00001 is the earliest fossil having been identified as a species of the sea lion genus Eumetopias, it is of importance to elucidate the evolutionary history of that genus. The morphometric comparisons were made among 51 ...
Frontiers in Ecology and Evolution
BULLETIN OF THE GEOLOGICAL SURVEY OF JAPAN
Current biology : CB, Jan 9, 2017
The pygmy right whale, Caperea marginata, is the most enigmatic living whale. Little is known abo... more The pygmy right whale, Caperea marginata, is the most enigmatic living whale. Little is known about its ecology and behaviour, but unusual specialisations of visual pigments [1], mitochondrial tRNAs [2], and postcranial anatomy [3] suggest a lifestyle different from that of other extant whales. Geographically, Caperea represents the only major baleen whale lineage entirely restricted to the Southern Ocean. Caperea-like fossils, the oldest of which date to the Late Miocene, are exceedingly rare and likewise limited to the Southern Hemisphere [4], despite a more substantial history of fossil sampling north of the equator. Two new Pleistocene fossils now provide unexpected evidence of a brief and relatively recent period in geological history when Caperea occurred in the Northern Hemisphere (Figure 1A,B).
Die Naturwissenschaften, 2016
Living baleen whales (Mysticeti) include the world's largest animals to have ever lived-blue ... more Living baleen whales (Mysticeti) include the world's largest animals to have ever lived-blue whales (Balaenoptera musculus) can reach more than 30 m. However, the gigantism in baleen whales remains little explored. Here, we compiled all published stem mysticetes from the Eocene and Oligocene and then mapped the estimated body size onto different phylogenies that suggest distinct evolutionary histories of baleen whales. By assembling all known stem baleen whales, we present three novel findings in early mysticete evolution. Results show that, regardless of different phylogenetic scenarios, large body size (more than 5-m long) evolved multiple times independently in their early evolutionary history. For example, the earliest known aetiocetid (Fucaia buelli, 33-31 Ma) was small in size, about 2 m, and a later aetiocetid (Morawanocetus-like animal, 26-23 Ma) can reach 8-m long-almost four times the size of Fucaia buelli-suggesting an independent gigantism in the aetiocetid lineage. ...
Kimura et al (2015): Bulletin of the Gunma Museum of Natural History, (19):39-48. Abstract: We re... more Kimura et al (2015): Bulletin of the Gunma Museum of Natural History, (19):39-48. Abstract: We report a new fossil mysticete, previously referred to as the "Shimajiri whale" (e.g., Adaniya, 1977), from the Upper Miocene of Miyako Island, Okinawa, Japan. The new material was recovered from the Okamishima Formation (Shimajiri Group), which is correlative with foraminiferal Zone N17. Very little cetacean material has been described from the Ryukyu Islands and the wider area of Southeast Asia, making this an important find. The specimen consists of a fragmentary cranium including both periotics and the left tympanic bulla, but missing the rostrum and the left zygomatic and supraorbital processes. The surfaces of most of the bones are badly eroded and reveal little sutural detail. Nevertheless, the specimen can be confidently identified as a balaenopterid based on (1) its abruptly depressed supraorbital process, (2) cranially elongated pars cochlearis and (3) the overlap of the...