Preliminary description of a late Middle Pleistocene mammalian fauna prior to the extinction of Gigantopithecus blacki from the Yixiantian Cave, Guangxi ZAR, South China.

In recent years, nearly 20 cave sites with rich assemblages of mammalian fossils have been found and excavated in the Chongzuo area, Guangxi Zhuang Autonomous Region, China. Their ages are distributed throughout the entire Pleistocene Epoch. These discoveries have greatly facilitated our understanding of the evolution of the Stegodon-Ailuropoda fauna and the environmental context of human evolution in southern China. Here, we present a preliminary report on a diverse late Middle Pleistocene mammalian fauna from the Yixiantian Cave in southern China, which is a typical representative of the Stegodon-Ailuropoda fauna (sensu lato). The fossil mammals are represented by isolated dental remains only. In 2010 and 2011, two seasons of systematic excavations at the Yixiantian Cave yielded a total of 4,958 identifiable mammalian teeth. They were identified as belonging to 37 species and 6 orders of mammals. In addition, the tooth type of all the teeth representing each species was also determined where possible. A single fragmentary molar was identified as belonging to Gigantopithecus blacki, indicating that its population had declined sharply at this time and was on the brink of extinction. Description of the Yixiantian fauna will not only help better characterize the composition of the Stegodon-Ailuropoda fauna during the late Middle Pleistocene, but also clarify our understanding of the paleoenvironmental context at a time just prior to the extinction of G. blacki.

Petrogenesis of isotopically enriched Quaternary magma with adakitic affinity associated with subduction of old lithosphere beneath central Myanmar.

We present a model for the petrogenesis of magma with adakitic affinity in an old subduction zone, which does not involve slab melting and is constrained by new geochronological and geochemical data for Mt. Popa, the largest of three Quaternary volcanoes in central Myanmar (Popa, Monywa and Singu). The edifice is composed of Popa Plateau (0.8-0.6 Ma) with high-K rocks and a stratovolcano (< 0.33 Ma) predominantly composed of medium-K rocks with adakitic affinity (Mg# 45-63, Sr/Y > 40). The distinct K contents indicate that the adakitic magmas cannot be derived from Popa high-K rocks, but they share trace-element signatures and Sr-Nd isotope ratios with medium-K basalts from Monywa volcano. Our estimation of water contents in Popa magma reveals that primary magma for medium-K basalts was generated by partial melting of wedge mantle with normal potential temperature (TP 1330-1340 °C) under wet conditions (H2O 0.25-0.54 wt%). Its melting was probably induced by asthenospheric upwelling that is recognized by tomographic images. Mafic adakitic magma (Mg# ~ 63, Sr/Y ~ 64) was derived from the medium-K basaltic magma in fractional crystallization of a garnet-bearing assemblage at high pressure, and felsic adakitic rocks (Mg# ~ 45, Sr/Y ~ 50) were produced by assimilation-fractional crystallization processes at mid-crustal depths.

Modern human teeth unearthed from below the ∼128,000-year-old level at Punung, Java: A case highlighting the problem of recent intrusion in cave sediments.

The emergence of modern humans in the eastern edge of the Eurasian Continent is debated between two major models: early (∼130-70 ka) and late (∼50 ka) dispersal models. The former view is grounded mainly on the claims that several cave sites in Southeast Asia and southern China yielded modern human fossils of those early ages, but such reports have been disputed for the lack of direct dating of the human remains and insufficient documentation of stratigraphy and taphonomy. By tracing possible burial process and conducting direct dating for an early Late Pleistocene paleontological site of Punung III, East Java, we here report a case that demonstrates how unexpected intrusion of recent human remains into older stratigraphic levels could occur in cave sediments. This further highlights the need of direct dating and taphonomic assessment before accepting either model. We also emphasize that the state of fossilization of bones and teeth is a useful guide for initial screening of recent intrusion and should be reported particularly when direct dating is unavailable. Additionally, we provide a revised stratigraphy and faunal list of Punung III, a key site that defines the tropical rainforest Punung Fauna during the early Late Pleistocene of the region.

Phylogenetic relationship of a fossil macaque (Macaca cf. robusta) from the Korean Peninsula to extant species of macaques based on zygomaxillary morphology.

Little is known about the biogeographical and evolutionary histories of macaques (Macaca spp.) in East Asia because the phylogenetic positions of fossil species remain unclear. Here we examined the zygomaxillary remains of a fossil macaque (M. cf. robusta) from the Durubong Cave Complex, South Korea, that dates back to the late Middle to Late Pleistocene, to infer its phylogenetic relationship to extant species. We took 195 fixed- and semi-landmarks from the zygomaxillary regions of the fossil specimen and from 147 specimens belonging to 14 extant species. We then conducted a generalized Procrustes analysis followed by a multivariate statistical analysis to evaluate the phenetic affinities of the fossil to the extant species and reconstructed the most parsimonious phylogenetic tree using a phylogenetic morphometric approach. We found that the fossil was most similar to Macaca fuscata (Japanese macaque) in the zygomaxillary morphospace although it was at the limit of the range of variation for this species. The second closest in the morphospace was the continental Macaca mulatta (rhesus macaque). Parsimonious reconstruction confirmed that the fossil was most closely related to M. fuscata, even after controlling for the effects of allometry. These findings suggest that in the late Middle to Late Pleistocene, close relatives of M. fuscata that looked like the extant species were distributed on the Korean Peninsula, where no species of macaques are found today. Thus, some morphological characteristics of M. fuscata may have developed before its ancestor dispersed into the Japanese archipelago.

The extinct river shark Glyphis pagoda from the Miocene of Myanmar and a review of the fossil record of the genus Glyphis (Carcharhiniformes: Carcharhinidae).

We redescribe an extinct river shark, Glyphis pagoda (Noetling), on the basis of 20 teeth newly collected from three different Miocene localities in Myanmar. One locality is a nearshore marine deposit (Obogon Formation) whereas the other two localities represent terrestrial freshwater deposits (Irrawaddy sediments), suggesting that G. pagoda from the Irrawaddy sediments was capable of tolerating low salinity like the extant Glyphis. Glyphis pagoda likely reached up to at least 185 cm in total body length and was probably piscivorous. The fossil species occurs in rocks of Myanmar and eastern and western India and stratigraphically ranges at least from the Lower Miocene (Aquitanian) to the lower Upper Miocene (mid-Tortonian). It has been classified under at least eight other genera to date, along with numerous taxonomic synonyms largely stemming from the lack of understanding of the heterodonty in extant Glyphis in the original description. Our literature review suggests that known Miocene shark faunas, particularly those in India, are manifested with unreliable taxonomic identifications and outdated classifications that warrant the need for a comprehensive taxonomic review in order to evaluate the evolutionary history and diversity pattern of Miocene shark faunas. The genus Glyphis has a roughly 23-million-year-long history, and its success may be related to the evolution of its low salinity tolerance. While extant Glyphis spp. are considered to be particularly vulnerable to habitat degradation and overfishing, the fossil record of G. pagoda provides renewed perspective on the natural history of the genus that can be taken into further consideration for conservation biology of the extant forms.

Protuberance or fossa on the lateral surface of the mandible in primates.

In order to clarify the morphological characteristics and function of the protuberance and/or fossa on the lateral surface of the mandible, we examined 778 mandibles of 9 genera, 19 species of non-human primates. Both protuberance and fossa were found in Macaca, Chlorocebus, and Cercocebus at frequencies ranging from 0% to 60%. The protuberance was composed of compact bone and was similar to the mandibular torus in humans. A well-developed protuberance extended from the fourth premolar to third molar region, and was situated at the central part of the mandibular body, or continued on the oblique line. Sometimes the protuberance localized on the mandibular base. A deep and large fossa was found in all individuals of Papio, Theropithecus, and Mandrillus, and the bone width was thin in the center of the fossa. The fossa extended from the third premolar to the second molar region, and the deepest area was the first molar region. In Macaca, Chlorocebus, and Cercocebus, the curvature of the external table of the mandible created a fossa. In Colobus, and Hylobates, the external surface of the mandible looked concave because of the thickened mandibular base. These concavo-convex structures have some biological functions and represent an adaptive change for mastication.

First discovery of colobine fossils from the Late Miocene/Early Pliocene in central Myanmar.

Here we report two kinds of colobine fossils discovered from the latest Miocene/Early Pliocene Irrawaddy sediments of the Chaingzauk area, central Myanmar. A left mandibular corpus fragment preserving M1-3 is named as a new genus and species, Myanmarcolobus yawensis. Isolated upper (M(1)?) and lower (M2) molars are tentatively identified as Colobinae gen. et sp. indet. Although both forms are medium-sized colobines, they are quite different from each other in M2 morphology. The isolated teeth of the latter show typical colobine-type features, so it is difficult to identify their taxonomic position, whereas lower molars of Myanmarcolobus have unique features, such as a trapezoid-shaped long median lingual notch, a deeply concave median buccal cleft, a strongly developed mesiobuccal notch, and rather obliquely running transverse lophids. Compared with fossil and living Eurasian colobine genera, Myanmarcolobus is most similar in lower molar morphology to the Pliocene Dolichopithecus of Europe rather than to any Asian forms. In Dolichopithecus, however, the tooth size is much larger and the median lingual notch is mesiodistally much shorter than that of Myanmarcolobus. The discovery of Myanmarcolobus in central Myanmar is the oldest fossil record in Southeast Asia not only of colobine but also of cercopithecid monkeys and raises many questions regarding the evolutionary history of Asian colobine monkeys.

Evolutionary trend in dental size in Gigantopithecus blacki revisited.

Previous analyses of dental size in Gigantopithecus blacki indicated marked sexual dimorphism and a trend towards increasing size through time. These studies were based on a sample of over 700 teeth from five localities excavated prior to 1990. Since then, 12 additional cave sites have been discovered in southern China, yielding hundreds of isolated teeth of G. blacki. Most of these sites are well dated by a combination of biochronology and absolute dating methods, so we now have a much better understanding of the chronology of G. blacki. Here, we reexamine the degree of sexual dimorphism and the question of dental size increase through time in G. blacki based on the expanded collections now available. Our results show that sexual dimorphism is not as marked as indicated in previous studies and confirm earlier analyses suggesting that the postcanine teeth of G. blacki tend to become larger through time from the beginning of the Early Pleistocene to the Middle Pleistocene.

A new late Eocene Bicornucythere species (Ostracoda, Crustacea) from Myanmar, and its significance for the evolutionary history of the genus.

The ostracode genus Bicornucythere (Ostracoda, Crustacea) is abundant in modern-day eutrophic marine bays, and is widely distributed in estuaries and inner bays throughout East Asia, including in China, Korea, Japan, and the Russian Far East. The evolutionary history of Bicornucythere is poorly understood. Here, we report on a new species of Bicornucythere (Bicornucythere concentrica sp. nov.) from the upper Eocene Yaw Formation in the Central Myanmar Basin. The oldest previously known Bicornucythere taxon, Bicornucythere secedens, was reported from lower Miocene strata in India, although a molecular phylogeny suggests that the genus first appeared in the Late Cretaceous. Bicornucythere concentrica sp. nov. is at least 10.9 million years older than the earliest known B. secedens. The new species occurs with Ammonia subgranulosa, a benthic foraminifer, an association that is representative of brackish water conditions in modern Asian bays. Our findings indicate that extant genera have inhabited Asian bays since the late Eocene. The paleobiogeography of Bicornucythere indicates that the taxon was dispersed onto Indian coasts during the collision between the Indian and Eurasian plates.

The first archaic Homo from Taiwan.

Recent studies of an increasing number of hominin fossils highlight regional and chronological diversities of archaic Homo in the Pleistocene of eastern Asia. However, such a realization is still based on limited geographical occurrences mainly from Indonesia, China and Russian Altai. Here we describe a newly discovered archaic Homo mandible from Taiwan (Penghu 1), which further increases the diversity of Pleistocene Asian hominins. Penghu 1 revealed an unexpectedly late survival (younger than 450 but most likely 190-10 thousand years ago) of robust, apparently primitive dentognathic morphology in the periphery of the continent, which is unknown among the penecontemporaneous fossil records from other regions of Asia except for the mid-Middle Pleistocene Homo from Hexian, Eastern China. Such patterns of geographic trait distribution cannot be simply explained by clinal geographic variation of Homo erectus between northern China and Java, and suggests survival of multiple evolutionary lineages among archaic hominins before the arrival of modern humans in the region.

Contribution of the maxillary sinus to the modularity and variability of nasal cavity shape in Japanese macaques.

The nasal cavity is essential for conditioning of inspired air, and its form likely impacts its function. Since humans and other anthropoids have reduced nasal turbinates when compared to other mammals, variation in relative surface area is mainly brought about by changes to overall nasal architecture. Previous studies of modern humans suggest that variation in the transverse dimensions of the nasal cavity is likely possible because of the presence of the maxillary sinuses. To understand the evolutionary origin of this adaptation, we investigated the nasofacial skeleton of Japanese macaques (Macaca fuscata). We applied computed tomography and geometric morphometrics to test how the nasal cavity shape is correlated with relative maxillary sinus volume and to evaluate how the nasal cavity shape is integrated with the external craniofacial shape. Our results show that the decreasing sinus volume is well associated with the relative expansion of nasal cavity at the middle region compared to the anterior and posterior openings. The nasal cavity shape is not integrated with the external craniofacial shape especially at the middle region as well as the posterior opening. Thus, the maxillary sinus in macaques may contribute to the modularity and variability of the nasal cavity shape, possibly facilitating the adaptive changes in the nasal airways of this species.

Computed tomography examination of the face of Macaca anderssoni (Early Pleistocene, Henan, northern China): Implications for the biogeographic history of Asian macaques.

Macaca anderssoni, a fossil macaque from the Early Pleistocene of northern China, has attracted much attention from researchers in terms of reconstructing the biogeographic history of Asian macaques, while its phylogenetic position remains debatable. In the present study, we evaluated patterns of variation in external and internal craniofacial morphologies among four phylogenetic groups of extant macaques (the fascicularis, sinica, silenus, and sylvanus groups), using computed tomography and multivariate analyses. We also reassessed the holotype of M. anderssoni, a partial cranium preserving the face and palate, to evaluate the phylogenetic group to which M. anderssoni is most closely related. Facial elongation was found to be significantly influenced by size. The particular combination of some allometric and non-allometric shape components was found to reflect phylogenetic relationships; however, these features of M. anderssoni fall intermediate among the four phylogenetic groups, with no typical similarities to any one group. The variations in nasal cavity shape were found to reflect phylogenetic relationships but those of the maxillary sinus did not. Macaca anderssoni has a nasal cavity that is laterally expanded anteriorly and constricted posteriorly, a unique morphology among macaques and shared only with larger members of the sinica group. This unique feature is considered to be a derived condition among macaques, suggesting that M. anderssoni is phylogenetically related to the sinica group (especially M. assamensis, M. thibetana, and M. arctoides) and that the populations of the sinica group were distributed in northern China during the Early Pleistocene. Currently, the populations of the sinica group are not distributed in northern East Asia, while those of the fascicularis group are. Thus, probably due to climatic deterioration in the Late Pleistocene, the former lineage has retreated southward or has become extinct in this region, being replaced by the latter lineage.

Ecogeographical and phylogenetic effects on craniofacial variation in macaques.

The widespread and complex ecogeographical diversity of macaques may have caused adaptive morphological convergence among four phylogenetic subgroups, making their phylogenetic relationships unclear. We used geometric morphometrics and multivariate analyses to test the null hypothesis that craniofacial morphology does not vary with ecogeographical and phylogenetic factors. As predicted by Bergmann's rule, size was larger for the fascicularis and sinica groups in colder environments. No clear size cline was observed in the silenus and sylvanus groups. An allometric pattern was observed across macaques, indicating that as size increases, rounded faces become more elongated. However, the elevation was differentiated within each of the former two groups and between the silenus and sylvanus groups, and the slope decreased in each of the two northern species of the fascicularis group. All allometric changes resulted in the similar situation of the face being more rounded in animals inhabiting colder zones and/or in animals having a larger body size than that predicted from the overarching allometric pattern. For non-allometric components, variations in prognathism were significantly correlated with dietary differences; variations in localized shape components in zygomatics and muzzles were significantly correlated with phylogenetic differences among the subgroups. The common allometric pattern was probably influenced directly or indirectly by climate-related factors, which are pressures favoring a more rounded face in colder environments and/or a more elongated face in warmer environments. Allometric dissociation could have occurred several times in Macaca even within a subgroup because of their wide latitudinal distributions, critically impairing the taxonomic utility of craniofacial elongation.

First discovery of colobine fossils from the early to middle Pleistocene of southern Taiwan.

Here we report on two kinds of cercopithecid fossil monkeys (Cercopithecinae and Colobinae) from the early to middle Pleistocene sediments of the Chochen (=Tsochen) area (Tsailiao-chi or Shinhua Hill), southern Taiwan. The fossil specimens include the first fossil record of colobine monkeys from Taiwan, where only macaque monkeys now occur. All cercopithecine fossils were identified as Macaca cf. Macaca cyclopis, the extant Taiwan macaque, except for one extremely large isolated upper molar, which may belong to another macaque species. On the other hand, all colobine specimens fall within the size variation of extant and extinct Rhinopithecus, but its specific status cannot be determined because of the scantiness of the fossil material. In Taiwan, Rhinopithecus presumably became extinct in the late Pleistocene, probably owing to global cooling and vegetation change, whereas macaques, which are of almost the same body size as Rhinopithecus, survived as M. cyclopis to the present. The contrasting history of survival between the two kinds of monkeys may be due to ecological/behavioral differences between them or as a result of accidental events that occurred in the Pleistocene of Taiwan.

Reassessment of Dolichopithecus (Kanagawapithecus) leptopostorbitalis, a colobine monkey from the Late Pliocene of Japan.

In the original description of Dolichopithecus (Kanagawapithecus) leptopostorbitalis, Iwamoto, Hasegawa and Koizumi, 2005, a moderately large-sized colobine monkey from the Late Pliocene of central Japan, affinities to the European Dolichopithecus rather than to the Transbaikalian Parapresbytis were noted based on the similarities in cranial morphology. Computed tomography scans confirm the presence of the maxillary sinus in the holotype, whereas it is probably absent in specimens of the European Dolichopithecus ruscinensis, the type species of this genus. This feature is either present or absent homogeneously in any given genus of living anthropoids. Its presence or absence is unknown in Parapresbytis, but the distinct morphology of the maxillary incisors in this taxon suggests that this form had different feeding habits from the Japanese colobines. These findings suggest that the Japanese colobine should be referred to henceforth as Kanagawapithecus leptopostorbitalis. Kanagawapithecus shares many important facial and dental features with Dolichopithecus rather than with Parapresbytis, but this association depends largely on the limited availability of comparable materials for the latter. Among colobines, the presence of the maxillary sinus is recorded only in Libypithecus and Cercopithecoides. The maxillary sinus is absent in all modern Asian colobines, implying that Kanagawapithecus is an isolated form without any relationship to living forms. Nevertheless, such phylogenetic interpretations are largely dependent on the restricted fossil evidence from the Pliocene and Pleistocene of eastern Eurasia and will be reexamined when new findings are made.

Allometry and interspecific differences in the facial cranium of two closely related macaque species.

Interpreting evolutionary history of macaque monkeys from fossil evidence is difficult, because their evolutionary fluctuations in body size might have removed or formed important morphological features differently in each lineage. We employed geometric morphometrics to explore allometric trajectories of craniofacial shape in two closely related species, Macaca fascicularis and M. fuscata. These two species exhibit a single shared allometric trajectory in superoinferior deflection of the anterior face, indicating that the differences in this feature can be explained by size variation. In contrast, two parallel trajectories are demonstrated in craniofacial protrusion, indicating that even if they are comparable in size, M. fuscata has a higher and shorter face than M. fascicularis. The degree of facial protrusion is most likely a critical feature for phyletic evaluation in the fascicularis group. Such analyses in various macaques would help to resolve controversies regarding phyletic interpretations of fossil macaques.

Nasal anatomy of Paradolichopithecus gansuensis (early Pleistocene, Longdan, China) with comments on phyletic relationships among the species of this genus.

Paradolichopithecus was a large cercopithecine primate that existed in Eurasia from the middle Pliocene to the early Pleistocene. Para. arvernensis from the late Pliocene of Senèze, France, shows no maxillary sinus, whereas Para.sushkini from the late Pliocene of Kuruksay, Tajikistan, has this feature. In this study, we examined a new maxillary specimen of Para. gansuensis from the early Pleistocene of Longdan, China. The Longdan maxilla had lost its facial part, which exposed the internal floor of the nasal region. The nasal floor expands laterally, making the maxillary body thin at the P3-M2 level and thick at the M3 level and extending to the maxillary tubercle. Such a topography is seen in the Senèze and Kuruksay crania. The Longdan maxilla shows no evidence of the formation of a maxillary sinus within the inferior portion of the thick maxillary body, as is seen in the Senèze cranium. Such a configuration could reflect the absence of a maxillary sinus in the Longdan specimen. Eastern Para. gansuensis might have dispersed eastward retaining a primitive condition, while central Para. sushkini would have acquired this feature independently in central Eurasia.

Meaning of the canine sexual dimorphism in fossil owl monkey, Aotus dindensis from the middle Miocene of La Venta, Colombia.

The owl monkey, Aotus, is the only modern nocturnal anthropoid with monogamous social structure. It has been demonstrated by the fossil species, Aotus dindensis, discovered from La Venta, Colombia, that the Aotus lineage had emerged as early as the middle Miocene (12-15 Ma). The type specimen of A. dindensis, which was discovered in 1986, preserves extremely large orbits, indicating a nocturnal habit. However, a few anatomical traits in living Aotus, such as the lack of a tapetum lucidum, indicates that nocturnality is a secondary adaptation from diurnal ancestry in this genus. Here we report new fossil specimens of A. dindensis from La Venta. The specimens include maxillary teeth and a mandibular fragment preserving lower molars. The detailed analysis of the specimen suggests that A. dindensis exhibits strong sexual dimorphism in the maxillary canine and premolars, which is traditionally associated with intense intermale competition for mates and/or food resources in non-monogamous, diurnal societies. As a result, the new fossil materials of A. dindensis demonstrate the first osteological evidence for the diurnal ancestry of the night monkey, Aotus. Moreover, the coexistence of large orbits and canine dimorphism suggests the presence of mosaic evolution in the craniodental characters of the Aotus lineage.

Observation of lateral mandibular protuberance in Taiwan macaque (Macaca cyclopis) using computed tomography imaging.

Morphological characteristics of the protuberance on the external surface of the mandible in Taiwan macaque (Macaca cyclopis) was investigated using cone-beam computed tomography. We observed 49 skulls of M. cyclopis. Of 7 skulls with deciduous and mixed dentitions in which M2s did not erupt, the protuberance was not found. Of the 13 skulls with mixed and permanent dentitions in which M2s had erupted, a palpable protuberance was found in one specimen. Of the 29 samples in which M3s had erupted completely, a perceptible protuberance was found in 2 samples, and palpable protuberance was found in 8 samples. Thus, the protuberance was found in 10 samples of the 29 samples with complete dentitions (34.5%), and the emergence of the protuberance may have been related to mandibular growth. In the case of the well-developed protuberance, it extended from the P4 to M3 region but did not extend to the mental foramina. By using cone-beam computed tomography, it was determined that the protuberance was composed of cortical bone and was the thickest in M2 region. Since the protuberance consisted of homogeneous cortical bone, it was considered to be the result of normal bone growth similar to the mandibular torus in humans.