Fine-fraction clays from the Chiang Muan mine in Phayao Province, northern Thailand, were studied... more Fine-fraction clays from the Chiang Muan mine in Phayao Province, northern Thailand, were studied using the x-ray diffraction method. The analysis determined the parent rocks and depositional environments of clays. Clay minerals in this area are subdivided into three zones of I to III. In zone I, montmorillonite is dominant, followed by kaolinite and illite. These clay minerals were derived
The palaeobiological record of 12 million to 7 million years ago (Ma) is crucial to the elucidati... more The palaeobiological record of 12 million to 7 million years ago (Ma) is crucial to the elucidation of African ape and human origins, but few fossil assemblages of this period have been reported from sub-Saharan Africa. Since the 1970s, the Chorora Formation, Ethiopia, has been widely considered to contain ~10.5 million year (Myr) old mammalian fossils. More recently, Chororapithecus abyssinicus, a probable primitive member of the gorilla clade, was discovered from the formation. Here we report new field observations and geochemical, magnetostratigraphic and radioisotopic results that securely place the Chorora Formation sediments to between ~9 and ~7 Ma. The C. abyssinicus fossils are ~8.0 Myr old, forming a revised age constraint of the human-gorilla split. Other Chorora fossils range in age from ~8.5 to 7 Ma and comprise the first sub-Saharan mammalian assemblage that spans this period. These fossils suggest indigenous African evolution of multiple mammalian lineages/groups betwe...
ABSTRACT ABSTRACT—A new fossil lizard of the genus Pachygenys is described on the basis of a sing... more ABSTRACT ABSTRACT—A new fossil lizard of the genus Pachygenys is described on the basis of a single, partially broken right mandible excavated from an unnamed formation of the Lower Cretaceous Sasayama Group in Hyogo Prefecture, western Honshu, Japan. The mandible exclusively shares a few apparently highly specialized morphological features, such as distinct foreshortening of the dentary tooth row and reduced dentary tooth number (nine), with Pachygenys thlastesa, the type species of the genus from the Lower Cretaceous of eastern China. However, the new species differs from the latter in having a shorter tooth row, anterior and middle teeth with unicuspid crowns (vs. bluntly truncated crowns in the latter), and posterior teeth with unicuspid and simple conical crowns (vs. bluntly truncated crowns in the latter). The specimen described here represents the first unequivocal fossil record of lizards in Japan, with its congeneric species occurring almost concurrently in eastern Eurasia.
A new genus and species of titanosauriform sauropod is erected based on a partial skeleton found ... more A new genus and species of titanosauriform sauropod is erected based on a partial skeleton found in the Lower Cretaceous Sasayama Group of Hyogo Prefecture, SW Japan. The new taxon is here named as Tambatitanis amicitiae gen. et sp. nov., which is diagnosed by the following features of the caudal vertebrae, chevrons and braincase: the postzygapophysis and the summit of the neural spine of the anterior caudal vertebrae are located beyond the posterior border of the centrum, the spine of the anterior caudal vertebrae is curved strongly anteriorly and bow-shaped in lateral view, the summit of the neural spine is expanded and hemispherical with its anterior face excavated by the posterodorsal extension of a deep and narrow SPRF, the transverse process of the anterior caudal vertebrae are short and L shaped, the anterior chevron is the longest among sauropods in proportion to body size, the distal ends of the anterior chevrons are rod-shaped, the distal ends of the mid chevrons are trans...
The late Miocene marked a time of significant geographic dispersal and radiation for many mammali... more The late Miocene marked a time of significant geographic dispersal and radiation for many mammalian taxa within Africa, including the proboscidean lineages. The ,6.1 Ma site of Lemudong'o, Kenya, yielded two elephantoid specimens. The first is a mandibular fragment with the third molar. This specimen represents a primitive member of the Anancus kenyensis lineage, with similarities to a specimen from
Vertebrate Paleobiology and Paleoanthropology, 2010
ABSTRACT Paleontological fieldwork between 1998–2005 by the Eyasi Plateau Expedition at Laetoli a... more ABSTRACT Paleontological fieldwork between 1998–2005 by the Eyasi Plateau Expedition at Laetoli and nearby sites produced a large collection of proboscidean fossils from the early to mid Pliocene Lower and Upper Laetolil Beds and late Pliocene Upper Ndolanya Beds, and possibly older sediments at Endolele, that substantially enlarges the sample of proboscidean material recovered earlier by Louis Leakey in 1935, Kohl-Larsen in 1938–1939, and Mary Leakey in the 1970s and early 1980s. The present study of the combined proboscidean sample confirms the presence of deinotheres and loxodont elephants, and provides the first description of anancine gomphotheres from the area. In addition, the first stegodont from the Eyasi Plateau is identified. The study also suggests that gomphotheres and loxodont elephants evolved locally in the Eyasi Plateau during the early Pliocene. Inference from stratigraphic distribution of proboscidean taxa, isotopic analyses, and dental morphology corresponds with paleoecological reconstruction depicting the Eyasi Plateau during the early-mid Pliocene as covered with abundant shrub- and grassland, with more restricted gallery forest, and as drier during the late Pliocene. Age-grade mortality profiles of elephants and deinotheres from the Laetolil and Upper Ndolanya Beds indicate a chronic lack of standing water or cyclical incidences of drought in the region for a sustained interval of time. KeywordsLaetoli-Endolele-Pliocene-Tanzania-Deinotheres-Loxodont elephants-Anancine gomphotheres
... of the archaic elephants Primelephas korotorensis and Stegotetrabelodon orbus and the primiti... more ... of the archaic elephants Primelephas korotorensis and Stegotetrabelodon orbus and the primitive anancine gomphothere Anancus kenyensis (Sanders 1997) and Pleistocene horizons at Olduvai dominated by the more advanced elephant Elephas recki (Maglio 1973; Coppens ...
Fine-fraction clays from the Chiang Muan mine in Phayao Province, northern Thailand, were studied... more Fine-fraction clays from the Chiang Muan mine in Phayao Province, northern Thailand, were studied using the x-ray diffraction method. The analysis determined the parent rocks and depositional environments of clays. Clay minerals in this area are subdivided into three zones of I to III. In zone I, montmorillonite is dominant, followed by kaolinite and illite. These clay minerals were derived
The palaeobiological record of 12 million to 7 million years ago (Ma) is crucial to the elucidati... more The palaeobiological record of 12 million to 7 million years ago (Ma) is crucial to the elucidation of African ape and human origins, but few fossil assemblages of this period have been reported from sub-Saharan Africa. Since the 1970s, the Chorora Formation, Ethiopia, has been widely considered to contain ~10.5 million year (Myr) old mammalian fossils. More recently, Chororapithecus abyssinicus, a probable primitive member of the gorilla clade, was discovered from the formation. Here we report new field observations and geochemical, magnetostratigraphic and radioisotopic results that securely place the Chorora Formation sediments to between ~9 and ~7 Ma. The C. abyssinicus fossils are ~8.0 Myr old, forming a revised age constraint of the human-gorilla split. Other Chorora fossils range in age from ~8.5 to 7 Ma and comprise the first sub-Saharan mammalian assemblage that spans this period. These fossils suggest indigenous African evolution of multiple mammalian lineages/groups betwe...
ABSTRACT ABSTRACT—A new fossil lizard of the genus Pachygenys is described on the basis of a sing... more ABSTRACT ABSTRACT—A new fossil lizard of the genus Pachygenys is described on the basis of a single, partially broken right mandible excavated from an unnamed formation of the Lower Cretaceous Sasayama Group in Hyogo Prefecture, western Honshu, Japan. The mandible exclusively shares a few apparently highly specialized morphological features, such as distinct foreshortening of the dentary tooth row and reduced dentary tooth number (nine), with Pachygenys thlastesa, the type species of the genus from the Lower Cretaceous of eastern China. However, the new species differs from the latter in having a shorter tooth row, anterior and middle teeth with unicuspid crowns (vs. bluntly truncated crowns in the latter), and posterior teeth with unicuspid and simple conical crowns (vs. bluntly truncated crowns in the latter). The specimen described here represents the first unequivocal fossil record of lizards in Japan, with its congeneric species occurring almost concurrently in eastern Eurasia.
A new genus and species of titanosauriform sauropod is erected based on a partial skeleton found ... more A new genus and species of titanosauriform sauropod is erected based on a partial skeleton found in the Lower Cretaceous Sasayama Group of Hyogo Prefecture, SW Japan. The new taxon is here named as Tambatitanis amicitiae gen. et sp. nov., which is diagnosed by the following features of the caudal vertebrae, chevrons and braincase: the postzygapophysis and the summit of the neural spine of the anterior caudal vertebrae are located beyond the posterior border of the centrum, the spine of the anterior caudal vertebrae is curved strongly anteriorly and bow-shaped in lateral view, the summit of the neural spine is expanded and hemispherical with its anterior face excavated by the posterodorsal extension of a deep and narrow SPRF, the transverse process of the anterior caudal vertebrae are short and L shaped, the anterior chevron is the longest among sauropods in proportion to body size, the distal ends of the anterior chevrons are rod-shaped, the distal ends of the mid chevrons are trans...
The late Miocene marked a time of significant geographic dispersal and radiation for many mammali... more The late Miocene marked a time of significant geographic dispersal and radiation for many mammalian taxa within Africa, including the proboscidean lineages. The ,6.1 Ma site of Lemudong'o, Kenya, yielded two elephantoid specimens. The first is a mandibular fragment with the third molar. This specimen represents a primitive member of the Anancus kenyensis lineage, with similarities to a specimen from
Vertebrate Paleobiology and Paleoanthropology, 2010
ABSTRACT Paleontological fieldwork between 1998–2005 by the Eyasi Plateau Expedition at Laetoli a... more ABSTRACT Paleontological fieldwork between 1998–2005 by the Eyasi Plateau Expedition at Laetoli and nearby sites produced a large collection of proboscidean fossils from the early to mid Pliocene Lower and Upper Laetolil Beds and late Pliocene Upper Ndolanya Beds, and possibly older sediments at Endolele, that substantially enlarges the sample of proboscidean material recovered earlier by Louis Leakey in 1935, Kohl-Larsen in 1938–1939, and Mary Leakey in the 1970s and early 1980s. The present study of the combined proboscidean sample confirms the presence of deinotheres and loxodont elephants, and provides the first description of anancine gomphotheres from the area. In addition, the first stegodont from the Eyasi Plateau is identified. The study also suggests that gomphotheres and loxodont elephants evolved locally in the Eyasi Plateau during the early Pliocene. Inference from stratigraphic distribution of proboscidean taxa, isotopic analyses, and dental morphology corresponds with paleoecological reconstruction depicting the Eyasi Plateau during the early-mid Pliocene as covered with abundant shrub- and grassland, with more restricted gallery forest, and as drier during the late Pliocene. Age-grade mortality profiles of elephants and deinotheres from the Laetolil and Upper Ndolanya Beds indicate a chronic lack of standing water or cyclical incidences of drought in the region for a sustained interval of time. KeywordsLaetoli-Endolele-Pliocene-Tanzania-Deinotheres-Loxodont elephants-Anancine gomphotheres
... of the archaic elephants Primelephas korotorensis and Stegotetrabelodon orbus and the primiti... more ... of the archaic elephants Primelephas korotorensis and Stegotetrabelodon orbus and the primitive anancine gomphothere Anancus kenyensis (Sanders 1997) and Pleistocene horizons at Olduvai dominated by the more advanced elephant Elephas recki (Maglio 1973; Coppens ...
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