Discovery of Propotamochoerus (Artiodactyla, Suidae) from the Neogene of Myanmar

Dento-gnathic specimens of Propotamochoerus (Mammalia, Artiodactyla, Suidae) were discovered from the upper Miocene and lower Pliocene of the Irrawaddy Group, central Myanmar. These specimens were identified as Propotamochoerus hysudricus and Propotamochoerus sp. cf. P. hysudricus. The discovery of P. cf. hysudricus from the lower Pliocene indicates a younger stratigraphic position of this genus. Small size of the premolars in the lower Pliocene specimens possibly suggests an intermediate stage of dental evolution for this form

Correlation between musculoskeletal structure of the hand and primate locomotion: Morphometric and mechanical analysis in prehension using the cross- and triple-ratios

Biometric ratios of the relative length of the rays in the hand have been analyzed between primate species in the light of their hand function or phylogeny. However, how relative lengths among phalanges are mechanically linked to the grasping function of primates with different locomotor behaviors remains unclear. To clarify this, we calculated cross and triple-ratios, which are related to the torque distribution, and the torque generation mode at different joint angles using the lengths of the phalanges and metacarpal bones in 52 primates belonging to 25 species. The torque exerted on the finger joint and traction force of the flexor tendons necessary for a cylindrical grip and a suspensory hand posture were calculated using the moment arm of flexor tendons measured on magnetic resonance images, and were compared among\ua0Hylobates\ua0spp.,\ua0Ateles\ua0sp., and\ua0Papio hamadryas. Finally, the torques calculated from the model were validated by a mechanical study detecting the force exerted on the phalanx by pulling the digital flexor muscles during suspension in these three species. Canonical discriminant analysis of cross and triple-ratios classified primates almost in accordance with their current classification based on locomotor behavior. The traction force was markedly reduced with flexion of the MCP joint parallel to the torque in brachiating primates; this was notably lower in the terrestrial quadrupedal primates than in the arboreal primates at mild flexion. Our mechanical study supported these features in the torque and traction force generation efficiencies. Our results suggest that suspensory or terrestrial quadrupedal primates have hand structures that can exert more torque at a suspensory posture, or palmigrade and digitigrade locomotion, respectively. Furthermore, our study suggests availability of the cross and triple-ratios as one of the indicators to estimate the hand function from the skeletal structure

アメリカグマ（Ursus americanus），マレーグマ（Helarctos malayanus），ホッキョクグマ（Ursus maritimus）における手内筋の筋重量について

The hands of the American black bear (Ursus americanus), the sun bear (Helarctos malayanus), the polar bear (Ursus maritimus), and the lion (Panthera leo) were dissected and the mass of the intrinsic hand muscles were systematically recorded to explore possible interspecies variation. Muscle mass was divided by the third metacarpal bone size for normalization. The results indicated that the normalized muscle masses of the thenar muscles were larger in the three bears than the lion, and the abductor pollicis muscle was larger in the sun bear than other bears. For the abductor digiti minimi muscle, the normalized muscle mass was larger in the three bears than the lion, but smaller in the polar bear among three bears. One limitation of this study is that here we provided only one specimen for each species, and thus the present results need to be confirmed by examining a larger number of cases in future studies. However, these differences in the intrinsic hand muscles of the four species may reflect adaptation for their different habits

Correlation between musculoskeletal structure of the hand and primate locomotion: Morphometric and mechanical analysis in prehension using the cross- and triple-ratios.

Biometric ratios of the relative length of the rays in the hand have been analyzed between primate species in the light of their hand function or phylogeny. However, how relative lengths among phalanges are mechanically linked to the grasping function of primates with different locomotor behaviors remains unclear. To clarify this, we calculated cross and triple-ratios, which are related to the torque distribution, and the torque generation mode at different joint angles using the lengths of the phalanges and metacarpal bones in 52 primates belonging to 25 species. The torque exerted on the finger joint and traction force of the flexor tendons necessary for a cylindrical grip and a suspensory hand posture were calculated using the moment arm of flexor tendons measured on magnetic resonance images, and were compared among Hylobates spp., Ateles sp., and Papio hamadryas. Finally, the torques calculated from the model were validated by a mechanical study detecting the force exerted on the phalanx by pulling the digital flexor muscles during suspension in these three species. Canonical discriminant analysis of cross and triple-ratios classified primates almost in accordance with their current classification based on locomotor behavior. The traction force was markedly reduced with flexion of the MCP joint parallel to the torque in brachiating primates; this was notably lower in the terrestrial quadrupedal primates than in the arboreal primates at mild flexion. Our mechanical study supported these features in the torque and traction force generation efficiencies. Our results suggest that suspensory or terrestrial quadrupedal primates have hand structures that can exert more torque at a suspensory posture, or palmigrade and digitigrade locomotion, respectively. Furthermore, our study suggests availability of the cross and triple-ratios as one of the indicators to estimate the hand function from the skeletal structure

A preliminary report on carnivorous mammals from Pondaung fauna

Some carnivore materials have been discovered from the Pondaung Formatioin in central Myanmar recently. The materials are separable into at least two genera, both of which are hyaenodontid creodonts. One of them is a medium-sized proviverrine. Collected parts include a maxilla, lower molar fragments, and some postcranial fragments. It shows some distinctive dental characters such as small protocone lobe on P_4, anterolingually-placed protocone and posterolingually-placed metacone relative to paracone on M_1 and M_2, and relatively large M_3 with a very reduced metaconid. The other is a much larger form. A maxillary fragment with a M_1 and a mandibular a fragment with P_2 to M_2 have been found for this form. possesses some similarities to Pterodon, but observations on more complete specimens and comparisons with other Pterodon-like hyaenodontids from Asia are necessary to settle a systematic assignment of this form. The two hyaenodontids are the only known mammalian predators from Pondaung fauna (latest Middle Eocene) based on the current knowledge

Notes on fish, reptilian, and several fragmentary mammalian dental fossils from the Pondaung Formation

We provide photos of fish and reptile fossils and several fragmentary mammalian dento-gnathic fossils from the Eocene Pondaung Formation of Myanmar with description of primate-like dento-gnathic fossils. The figured fossils consist of four specimens of fishes, 11 specimens of reptiles (two vertebral specimens of snake-like reptile, six lower jaws of agamid lizard, three jaws of indeterminate lizard, and two teeth of crocodile), and 42 specimens of mammals (24 fragmentary fossils, 12 fossils of the MGW specimens, three unreported primate-like fossils, and three previously reported primate fossils). Although these figured specimens are fragmentary, they add new evidence on the Pondaung vertebrate fauna, contributing to the understanding of the fauna

Postcranial materials of Pondaung mammals (middle Eocene, Myanmar)

Diversity of the Pondaung mammalian fauna (middle Eocene Myanmar) has been explored based on the dental materials. In this paper, we provided photos of skeletal materials of a rodent, carnivores, artiodactyls, and perissodactyls. Postcranial morphology of the endemic Pondaung mammals are compared with those of related fossil species from North America and Europe, revealing additional postcranial diversity in Eocene carnivorans, dichobunid artiodactyls, ruminants, and chalicotherioid perissodactyls. The postcranial materials indicated a presence of an additional taxon, a very small artiodactyl, that has not been known from the dental materials of the Pondaung mammals. The differences in postcranial morphologies suggested a divers locomotory behavior among the mammals of the Pondaung fauna, such that scansors, generalized terrestrialists with cursorial tendency, and generalized terrestrialists with digging adaptations were present among the carnivorous mammals, and that small-sized and medium-sized ungulates distributed on various stages of cursorial adaptations

Nonsurgical abilities predict laparoscopic surgical skills after training

It has been suggested that certain nonsurgical abilities can be used to predict laparoscopic surgical skills. This study aimed to conclusively determine whether these nonsurgical proficiencies are associated with laparoscopic surgical skills both before and after surgical training. We recruited 58 medical students for this study and assessed their laparoscopic surgical skills using the Surgical Assessment Device (HUESAD). The participants performed ten runs of HUESAD tasks before training. After they underwent box training and VR simulator training once a week for two weeks, they performed ten additional runs of the tasks. Finally, the participants responded to a questionnaire about their involvement in nonsurgical skills, including playing computer games, typing, sewing, playing musical instruments, and using chopsticks. Pearson’s correlation coefficients were calculated. No significant correlation was found between any of the nonsurgical skills and initial laparoscopic surgical skills. However, a significant correlation was observed between the participants’ ability to use chopsticks and scissors, ride a bicycle, and post-training laparoscopic surgical skills (p < 0.05). Several nonsurgical abilities investigated in this study did not correlate with pre- and post-training laparoscopic surgical skills, demonstrating that certain nonsurgical skills predict laparoscopic surgical skills not before but after training. This approach can be useful in predicting improvement in laparoscopic surgical skills. The ability to predict laparoscopic surgical skills is important for designing custom training programs to ensure safety and high-quality operations in laparoscopic surgery

Early Pleistocene Javan rhinoceros from the Irrawaddy Formation, Myanmar

We report dental fossils of Javan rhinoceros, Rhinoceros sondaicus (Mammalia, Perissodactyla, Rhinocerotidae), discovered from the upper part of the Irrawaddy Formation, the lower Pleistocene of central Myanmar. This is the first discovery of R. sondaicus from the Irrawaddy Formation, and these materials are possibly to be the oldest fossil record of this species in the world. The present materials consist of two fragmentary maxillae with M_1-3. They are referable to those of Rhinoceros sondaicus in having the following characteristics on the upper molars: moderately developed molar crochet, subhypsodonty, absence of the molar crista and antecrochet, absence of the protocone fold, absence of the metacone bulge on M_3, sinuosity of the ectoloph, strong molar parastyle fold, and deeper median valley than the posterior valley. The discovery of early Pleistocene Rhinoceros sondaicus in Myanmar fills geographical and chronological gaps between the late Miocene Gaindartherium (a probable ancestor of the genus Rhinoceros) from Indo-Pakistan and middle Pleistocene R. sondaicus from Java and Sumatra. It suggests that this species originated as early as early Pleistocene in continental Asia