Aung Naing Soe

The anthropoid status of a primate from the late middle Eocene Pondaung Formation (Central Myanmar): Tarsal evidence

Primate dental and postcranial remains from the Eocene Pondaung Formation (Myanmar) have been the subject of considerable confusion since their initial discoveries, and their anthropoid status has been widely debated. We report here a well preserved primate talus discovered in the Segyauk locality near Mogaung that displays derived anatomical features typical of haplorhines, notably anthropoids, and lacks strepsirhine synapomorphies. Linear discriminant and parsimony analyses indicate that the talus from Myanmar is more similar structurally to those of living and extinct anthropoids than to those of adapiforms, and its overall osteological characteristics further point to arboreal quadrupedalism. Regressions of talar dimensions versus body mass in living primates indicate that this foot bone might have belonged to Amphipithecus. This evidence supports hypotheses favoring anthropoid affinities for the large-bodied primates from Pondaung and runs contrary to the hypothesis that Pondaungia and Amphipithecus are strepsirhine adapiforms.

Late Middle Eocene primate from Myanmar and the initial anthropoid colonization of Africa

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.

A new primate from the Eocene Pondaung Formation of Myanmar and the monophyly of Burmese amphipithecids

The family Amphipithecidae is one of the two fossil primate taxa from Asia that appear to be early members of the anthropoid clade. Ganlea megacanina, gen. et sp. nov., is a new amphipithecid from the late middle Eocene Pondaung Formation of central Myanmar. The holotype of Ganlea is distinctive in having a relatively enormous lower canine showing heavy apical wear, indicating an important functional role of the lower canine in food preparation and ingestion. A phylogenetic analysis of amphipithecid relationships suggests that Ganlea is the sister taxon of Myanmarpithecus, a relatively small-bodied taxon that has often, but not always, been included in Amphipithecidae. Pondaungia is the sister taxon of the Ganlea + Myanmarpithecus clade. All three Pondaung amphipithecid genera are monophyletic with respect to Siamopithecus, which is the most basal amphipithecid currently known. The inclusion of Myanmarpithecus in Amphipithecidae diminishes the likelihood that amphipithecids are specially related to adapiform primates. Extremely heavy apical wear has been documented on the lower canines of all three genera of Burmese amphipithecids. This distinctive wear pattern suggests that Burmese amphipithecids were an endemic radiation of hard object feeders that may have been ecological analogues of living New World pitheciin monkeys.

New Sivaladapid primates from the Eocene Pondaung formation of Myanmar and the Anthropoid status of Amphipithecidae

Abstract Fossil primates from the late middle Eocene Pondaung Formation of Myanmar have figured prominently in recent efforts to reconstruct the early evolutionary history of anthropoids. The anthropoid affinities of Amphipithecidae, the most abundant fossil primates currently known from the Pondaung Formation, have proven to be particularly controversial. Here we describe two new genera and species, Paukkaungia parva and Kyitchaungia takaii, of sivaladapid primates from the Pondaung Formation. Tarsal elements that are appropriate in size and morphology to belong to Kyitchaungia takaii are also described. These are the first undoubted adapiforms—and the first fossil primates other than anthropoids—to be reported from the Eocene of Myanmar. The discovery of sivaladapids in the Pondaung Formation enhances the taxonomic and paleoecological diversity of the late middle Eocene primate fauna of Myanmar. In this respect, the fossil primate community from the Pondaung Formation appears to have resembled roughly contemporaneous assemblages from China, Thailand, and Pakistan. The newly discovered sivaladapid tarsal elements help to resolve conflicting interpretations regarding the taxonomic allocation of large-bodied primate postcranial elements from the Pondaung Formation. The NMMP 20 partial skeleton from the Pondaung Formation, which has often been regarded as that of an amphipithecid, is more plausibly interpreted as pertaining to a third Pondaung sivaladapid. Recognizing the sivaladapid affinities of the NMMP 20 partial skeleton solidifies the anthropoid status of amphipithecids, further constraining temporal, phylogenetic, and biogeographic hypotheses regarding anthropoid origins.

NEW REMAINS OF PONDAUNGIMYS ANOMALUROPSIS (RODENTIA, ANOMALUROIDEA) FROM THE LATEST MIDDLE EOCENE PONDAUNG FORMATION OF CENTRAL MYANMAR

Abstract Except for the few specimens previously reported from the late middle Eocene of North Africa (Algeria) and more recently from South Asia (Myanmar), the fossil record of anomaluroid rodents is relatively scarce for the Paleogene Period. In this paper, we describe new material, notably a skull, of the anomaluroid taxon Pondaungimys anomaluropsis Dawson et al., 2003, recently described from the latest middle Eocene Pondaung Formation in Central Myanmar (South Asia). Pondaungimys shows a dental pattern very similar to that of Nementchamys, an anomaluroid rodent previously reported from roughly coeval deposits in Algeria. Although Nementchamys and Pondaungimys have a dental pattern relatively more primitive in some respects than that of Miocene and modern anomalurids, in other respects they show a derived dental complexity that leads us to consider both taxa as the closest outgroups of the Anomaluridae sensu stricto (the true scaly-tailed flying squirrels) within the Anomaluroidea. Pondaungimys clearly demonstrates that the evolutionary history of the anomaluroid rodents is not limited to Africa. The widespread South Asian-North African distribution of the late middle Eocene forms strongly suggests that faunal exchanges between Africa and Asia took place during the Paleogene, a statement supported by other mammalian groups.

A palaeo Tibet–Myanmar connection? Reconstructing the Late Eocene drainage system of central Myanmar using a multi-proxy approach

Strain resulting from the collision of India with Asia has caused fundamental changes to Asian drainage patterns, but the timing and nature of these changes are poorly understood. One frequently proposed hypothesis involves the connection of the palaeo Tsangpo drainage to a precursor to the Irrawaddy River of central Myanmar in the Palaeogene. To test this hypothesis, we studied the provenance of Palaeogene fluvio-clastic sedimentary rocks that crop out in central Myanmar, namely the Late Middle Eocene–Early Oligocene Pondaung and Yaw Formations. Isotopic analysis on bulk-rock and petrographic data indicate a primary magmatic arc source, and a secondary source composed of recycled, metamorphosed basement material. Although the exact location of both sources is hardly distinguishable because Burmese and Tibetan provinces share common lithological features, the presence of low-grade metamorphic fragments, the heterogeneity in Sr–Nd isotopic values of bulk sediments and westward-directed palaeoflow orientations indicate a proximal source area located on the eastern Asian margin. Central Myanmar was the locus of westward-prograding deltas opening into the Indian Ocean, supplied by the unroofing of an Andean-type cordillera that extended along the Burmese margin. We found no evidence to support a palaeo Tsangpo–Irrawaddy River, at least during the Late Eocene. Supplementary material: Data locations, and isotopic and petrographic results are available at www.geolsoc.org.uk/SUP18655.

First Magnetostratigraphic Study of the Pondaung Formation: Implications for the Age of the Middle Eocene Anthropoids of Myanmar

We report the results of a magnetostratigraphic investigation to improve the stratigraphical and chronological resolution of the Pondaung Formation of central Myanmar. A total of 98 samples were collected from 45 sites through a 319‐m‐thick section at the fossiliferous locality of Yashe Kyitchaung or the Primate Resort (yielding primate species Bahinia pondaungensis, Amphipithecus mogaungensis, and Myanmarpithecus yarshensis) near the Bahin village. Thermal and alternating field demagnetization allowed separation of two remanence components. The high‐temperature component is interpreted as the characteristic magnetization. Rock magnetic experiments show that the remanence magnetization is mainly carried by magnetite. This investigation documents normal polarity remanent magnetization, with a mean direction \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

A new anthracotheriid artiodactyl from Myanmar, and the relative ages of the Eocene anthropoid primate-bearing localities of Thailand (Krabi) and Myanmar (Pondaung)

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