We report here new craniodental remains from the late Eocene Krabi coal mine in Thailand that can be attributed to the suoid Siamochoerus banmarkensis Ducrocq, Chaimanee, Suteethorn & Jaeger, 1998. ...This material that includes the complete lower dentition and isolated upper molars provides new information on the dental morphology of this species and makes S. banmarkensis, together with Egatochoerus jaegeri Ducrocq, 1994 from Krabi, the second best documented early suoid in the Eocene of Asia. A few dental features that can be observed on these new remains suggest that S. banmarkensis might be more closely related to Suidae Gray, 1821, but it also illustrates the difficulty to attribute a precise taxonomic position to Eocene taxa.
Nous décrivons dans ce travail de nouveaux restes crânio-dentaires provenant de la mine de lignite de Krabi d’âge Eocène supérieur en Thaïlande et pouvant être attribués au suoïde Siamochoerus banmarkensis Ducrocq, Chaimanee, Suteethorn & Jaeger, 1998. Ce matériel, qui inclue la dentition inférieure complète et des molaires supérieures isolées, permet de préciser la morphologie dentaire pour cette espèce et fait de S. banmarkensis, tout comme Egatochoerus jaegeri Ducrocq, 1994 de Krabi, le second suoïde primitif le mieux documenté dans l’Eocène d’Asie. Quelques caractères dentaires, pouvant être observés sur ces nouveaux restes, suggèrent que S. banmarkensis pourrait être plus étroitement apparenté aux Suidae Gray, 1821, mais cela illustre également la difficulté d’attribuer une position taxonomique précise aux formes éocènes
Fossil Alligator remains from Asia are critical for tracing the enigmatic evolutionary origin of the Chinese alligator, Alligator sinensis, the only living representative of Alligatoridae outside the ...New World. The Asian fossil record is extremely scarce and it remains unknown whether A. sinensis is an anagenetic lineage or alternatively, extinct divergent species were once present. We provide a detailed comparative description of a morphologically highly distinct Alligator skull from the Quaternary of Thailand. Several autapomorphic characters warrant the designation of a new species. Alligator munensis sp. nov. shares obvious derived features with A. sinensis but autapomorphies imply a cladogenetic split, possibly driven by the uplift of the southeastern Tibetan plateau. The presence of enlarged posterior alveoli in Alligator munensis is most consistent with a reversal to the alligatorine ancestral condition of having crushing dentition, a morphology strikingly absent among living alligatorids. Crushing dentition has been previously considered to indicate an ecological specialisation in early alligatorines that was subsequently lost in Alligator spp. However, we argue that there is yet no evidence for crushing dentition reflecting an adaptation for a narrower niche, while opportunistic feeding, including seasonal utilisation of hard-shelled preys, is a reasonable alternative interpretation of its function.
Determining the diet of fossil apes is essential to understand primate evolution. The giant form from Southeast Asia, Gigantopithecus blacki, may have been up to 270 kg and survived until about ...100,000 years ago. It is known only from isolated teeth and a few lower jaws with reduced front teeth and enlarged molars and premolars. A large spectrum of diets has been suggested for Gigantopithecus, ranging from carnivorous or grass-feeding in open savannah to a vegetarian diet dominated by fruits or bamboo. To determine its habitat and to understand why it became extinct, we tried to evaluate its dietary niche. The carbon stable isotopic composition of tooth enamel of this taxon compared to coeval and extant mammals from Southeastern Asia show that Gigantopithecus was a forest-dweller with a generalist vegetarian diet and was not specialized on bamboos. In southern China, Gigantopithecus lived in a forested environment, as did the coeval fauna, while in Thailand, it occupied only the forested part of a mosaic landscape including significant parts of open savannah. The carbon isotopic compositions of Gigantopithecus were different from those of omnivorous and carnivorous taxa, but very similar to those of orang-utans and unlike those of the bamboo-specialist giant panda. Therefore, even when open savannah environments were present in the landscape, Gigantopithecus foraging was limited to forested habitats. The very large size of Gigantopithecus, combined with a relatively restricted dietary niche, may explain its demise during the drastic forest reduction that characterized the glacial periods in South East Asia.
Recent discoveries of older and phylogenetically more primitive basal anthropoids in China and Myanmar, the eosimiiforms, support the hypothesis that Asia was the place of origins of anthropoids, ...rather than Africa. Similar taxa of eosimiiforms have been discovered in the late middle Eocene of Myanmar and North Africa, reflecting a colonization event that occurred during the middle Eocene. However, these eosimiiforms were probably not the closest ancestors of the African crown anthropoids. Here we describe a new primate from the middle Eocene of Myanmar that documents a new clade of Asian anthropoids. It possesses several dental characters found only among the African crown anthropoids and their nearest relatives, indicating that several of these characters have appeared within Asian clades before being recorded in Africa. This reinforces the hypothesis that the African colonization of anthropoids was the result of several dispersal events, and that it involved more derived taxa than eosimiiforms.
We describe several mammal taxa from the poorly known late Eocene locality of Bang Mark, Krabi Basin in southern Thailand. Most of them were unknown in that locality that now includes 19 distinct ...taxa. The new material corresponds to dental remains that can be attributed to a carnivoran, a dichobunid, ruminants, anthracotheres and perissodactyls. These remains provide information on the affinities of several genera that were uncertain so far. Archaeotragulus might be more closely related to Siamotragulus from the Miocene of Southeast Asia, Pakistan and East Africa, and the tragulid status of Krabitherium is supported by the morphology of its p4. We also describe the smallest known anthracothere, Geniokeryx nanus, sp. nov., and a new species of eomoropid chalicothere, Eomoropus meridiorientalis, sp. nov., that represents the first record of that family in the Krabi fauna. This work also supports the contemporaneity of Bang Mark with Wai Lek and Bang Pu Dam.
Sivaladapidae is a poorly known Asian strepsirrhine family originally discovered in Miocene sediments of the Indian subcontinent. Subsequent research has considerably increased the diversity, ...temporal range, and geographical distribution of this group, now documented from China, Thailand, Myanmar, Pakistan, and India and whose earliest representatives date back to the Middle Eocene. We present here a new taxon of sivaladapid from the Na Duong coal mine in the Latest Middle Eocene-Late Eocene of Vietnam. It represents the first Eocene primate from Vietnam and the first medium-sized mammal recovered from this locality, thus documenting a completely new part of the Na Duong paleobiodiversity. This taxon is the largest sivaladapid ever found with an estimated body weight of 5.3 kg and it represents a new subfamily of sivaladapids in exhibiting a very peculiar combination of dental features yet unknown in the fossil record of the family (e.g., retention of four premolars, high-crowned molars with accentuated bunodonty and extreme crest reduction). Besides documenting a complete new part of sivaladapid evolution, its primitive dental formula and derived features shared with the Early Eocene Asiadapidae reinforce the hypothesis of a basal branching of sivaladapids among strepsirrhines.
The fluviatile terrace deposits of Khok Sung, Nakhon Ratchasima province, have yielded more than one thousand fossils, making this the richest Pleistocene vertebrate fauna of Thailand. The excellent ...preservation of the specimens allows precise characterization of the faunal composition. The mammalian fauna consists of fifteen species in thirteen genera, including a primate, a canid, a hyaenid, proboscideans, rhinoceroses, a suid, cervids, and bovids. Most species correspond to living taxa but globally (Stegodon cf. orientalis) and locally (Crocuta crocuta ultima, Rhinoceros unicornis, Sus barbatus, and Axis axis) extinct taxa were also present. The identification of Axis axis in Khok Sung, a chital currently restricted to the Indian Subcontinent, represents the first record of the species in Southeast Asia. Three reptilian taxa: Crocodylus cf. siamensis, Python sp., and Varanus sp., are also identified. Faunal correlations with other Southeast Asian sites suggest a late Middle to early Late Pleistocene age for the Khok Sung assemblage. However, the Khok Sung mammalian fauna is most similar to that of Thum Wiman Nakin, dated to older than 169 ka. The Khok Sung large mammal assemblage mostly comprises mainland Southeast Asian taxa that migrated to Java during the latest Middle Pleistocene, supporting the hypothesis that Thailand was a biogeographic pathway for the Sino-Malayan migration event from South China to Java.
Reconstructing the origin and early evolutionary history of anthropoid primates (monkeys, apes, and humans) is a current focus of paleoprimatology. Although earlier hypotheses frequently supported an ...African origin for anthropoids, recent discoveries of older and phylogenetically more basal fossils in China and Myanmar indicate that the group originated in Asia. Given the Oligocene-Recent history of African anthropoids, the colonization of Africa by early anthropoids hailing from Asia was a decisive event in primate evolution. However, the fossil record has so far failed to constrain the nature and timing of this pivotal event. Here we describe a fossil primate from the late middle Eocene Pondaung Formation of Myanmar, Afrasia djijidae gen. et sp. nov., that is remarkably similar to, yet dentally more primitive than, the roughly contemporaneous North African anthropoid Afrotarsius. Phylogenetic analysis suggests that Afrasia and Afrotarsius are sister taxa within a basal anthropoid clade designated as the infraorder Eosimiiformes. Current knowledge of eosimiiform relationships and their distribution through space and time suggests that members of this clade dispersed from Asia to Africa sometime during the middle Eocene, shortly before their first appearance in the African fossil record. Crown anthropoids and their nearest fossil relatives do not appear to be specially related to Afrotarsius, suggesting one or more additional episodes of dispersal from Asia to Africa. Hystricognathous rodents, anthracotheres, and possibly other Asian mammal groups seem to have colonized Africa at roughly the same time or shortly after anthropoids gained their first toehold there.
Serows and gorals (Bovidae, Caprinae) are emblematic antelopes distributed in Southeast Asia. They all are nearly threaten or vulnerable species nowadays despite having a more widespread distribution ...during the Pleistocene. Fossils of three native caprine species, i.e., a Sumatran serow
Capricornis sumatraensis
, Chinese goral
Naemorhedus griseus
, and Himalayan goral
Naemorhedus goral
, were recovered from four Pleistocene paleontological and archeological sites in Thailand, namely Pha Bong, Khok Sung, Tham Wiman Nakin, and Tham Lod Rockshelter. To investigate dietary changes of these Southeast Asian serows and gorals through the Quaternary, differences in feeding habits and habitat preferences between the Pleistocene and extant populations were examined using the hypsodonty index (HI) together with the mesowear II method and the dental microwear texture analysis (DMTA). The HI and mesowear-II results showed that Pleistocene and extant caprines were mixed feeders. For the Pleistocene caprine populations, the DMTA results suggested more browsing signals for
C. sumatraensis
than both
Naemorhedus
species that were mixed feeders similar to their extant populations. The DMTA demonstrated a considerable dietary overlap among the Pleistocene sympatric caprine populations. The dental microwear results also revealed that the extant
C. sumatraensis
is a leaf-dominant browser, while the extant
N. griseus
possibly feeds on seeds or tough food items. These data combined with previous stable carbon isotope analyses reinforce the idea that the restricted ranges of habitats for these extant serow and goral populations have possibly been driven by the Holocene climatic and environmental changes as well as the negative effects of human activities.
Three taxa within the subfamily Caprinae (Himalayan goral Naemorhedus goral, Chinese goral Naemorhedus griseus, and Sumatran serow Capricornis sumatraensis) live in the mountainous upland forests of ...Southeast Asia, where they are considered as vulnerable or near threatened species. Co-occurrences between these two recognized genera have been documented from some Pleistocene fossil sites in Thailand, suggesting more widely overlapping distribution in the past than today. However, diet and habitat preferences of these Pleistocene and present-day coexisting species have rarely been investigated so far. For the past three decades, stable carbon and oxygen isotope analyses become more commonplace in ecological investigations, allowing us to explore the diets and habitats of ancient and extant animals as well as to reconstruct environmental conditions in the past. We reconstructed diets and habitats of these taxa from five fossil sites in Thailand during the past 400,000 years (from the Middle Pleistocene to the Early Holocene) and from some modern wildlife using the isotopic analysis of carbonate in tooth enamel, in order to test species co-occurrence patterns during the Pleistocene and to examine possible changes of their niche breadths over evolutionary time. Our carbon isotope analysis revealed remarkably different ecological patterns between Naemorhedus and Capricornis. The Pleistocene Sumatran serow has been a greater generalist than both the Himalayan and Chinese gorals that fed on pure C4 or mixed C3 and C4 plants restricted to an open landscape habitat and than its extant population that occupies a closed-canopy forest. This suggests that the habitat contraction of the modern wildlife is likely due to the Holocene climate change and the human impacts on Thai ecosystems. In addition to the loss or reduction of grasslands after the latest Pleistocene when rainforests became dominant and besides the human hunting and predation pressure, the high interspecific competition likely contributed to the extirpation of Himalayan gorals in Thailand. Developing a strategic plan for the future biodiversity conservation, a long-term historical isotope approach allowed us to predict the contrasting habitat suitability, a lowland grassland, for these two threatened goral species as testified by their ecological persistence during the Pleistocene.
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