Daisuke Kubo

The Ardipithecus Ramidus Skull and Its Implications for Hominid Origins

The highly fragmented and distorted skull of the adult skeleton ARA-VP-6/500 includes most of the dentition and preserves substantial parts of the face, vault, and base. Anatomical comparisons and micro–computed tomography–based analysis of this and other remains reveal pre-Australopithecus hominid craniofacial morphology and structure. The Ardipithecus ramidus skull exhibits a small endocranial capacity (300 to 350 cubic centimeters), small cranial size relative to body size, considerable midfacial projection, and a lack of modern African ape–like extreme lower facial prognathism. Its short posterior cranial base differs from that of both Pan troglodytes and P. paniscus. Ar. ramidus lacks the broad, anteriorly situated zygomaxillary facial skeleton developed in later Australopithecus. This combination of features is apparently shared by Sahelanthropus, showing that the Mio-Pliocene hominid cranium differed substantially from those of both extant apes and Australopithecus.

Brain size of Homo floresiensis and its evolutionary implications

The extremely small endocranial volume (ECV) of LB1, the type specimen of Homo floresiensis, poses a challenge in our understanding of human brain evolution. Some researchers hypothesize dramatic dwarfing of relative brain size from Homo erectus presumably without significant decrease in intellectual function, whereas others expect a lesser degree of brain diminution from a more primitive, small-brained form of hominin currently undocumented in eastern Asia. However, inconsistency in the published ECVs for LB1 (380–430 cc), unclear human intraspecific brain–body size scaling and other uncertainties have hampered elaborative modelling of its brain size reduction. In this study, we accurately determine the ECV of LB1 using high-resolution micro-CT scan. The ECV of LB1 thus measured, 426 cc, is larger than the commonly cited figure in previous studies (400 cc). Coupled with brain–body size correlation in Homo sapiens calculated based on a sample from 20 worldwide modern human populations, we construct new models of the brain size reduction in the evolution of H. floresiensis. The results show a more significant contribution of scaling effect than previously claimed.

Tail-Sitter Vertical Takeoff and Landing Unmanned Aerial Vehicle: Transitional Flight Analysis

A new design for a tail-sitter vertical takeoff and landing unmanned aerial vehicle was proposed. A nonlinear mathematical model of the vehicle dynamics was constructed by combining simple estimation methods. The flight characteristics were revealed through a trim analysis and an optimized transitional flight path analysis by using the mathematical model. The trim analysis revealed the existence of a flight path constraint to avoid stall; the vehicle could not descend in low-speed flight without high-lift devices such as flaps and slats. These devices improved the descentperformance. Inparticular, slatsprovidedasubstantialimprovement; theyenabled adescent rateof2 m=s. In the optimized transitional flight path analysis, a level outbound transition without high-lift devices was achieved althoughatrimmedlevel flightatlowspeed,aswasshowninthetrimanalysis,wasnotpossible;thiswasbecausethe outboundtransition wasanaccelerative flight.Onthe contrary,without high-lift devices, the vehicle could notavoid climbing to avoid stall during inbound transitions. The slats provided a satisfactory improvement during the transition and enabled a level inbound transition. These results showed the necessity of leading-edge slats for the proposed tail-sitter vertical takeoff and landing unmanned aerial vehicle.

Craniofacial morphology of Homo floresiensis: description, taxonomic affinities, and evolutionary implication.

This paper describes in detail the external morphology of LB1/1, the nearly complete and only known cranium of Homo floresiensis. Comparisons were made with a large sample of early groups of the genus Homo to assess primitive, derived, and unique craniofacial traits of LB1 and discuss its evolution. Principal cranial shape differences between H. floresiensis and Homo sapiens are also explored metrically. The LB1 specimen exhibits a marked reductive trend in its facial skeleton, which is comparable to the H. sapiens condition and is probably associated with reduced masticatory stresses. However, LB1 is craniometrically different from H. sapiens showing an extremely small overall cranial size, and the combination of a primitive low and anteriorly narrow vault shape, a relatively prognathic face, a rounded oval foramen that is greatly separated anteriorly from the carotid canal/jugular foramen, and a unique, tall orbital shape. Whereas the neurocranium of LB1 is as small as that of some Homo habilis specimens, it exhibits laterally expanded parietals, a weak suprameatal crest, a moderately flexed occipital, a marked facial reduction, and many other derived features that characterize post-habilis Homo. Other craniofacial characteristics of LB1 include, for example, a relatively narrow frontal squama with flattened right and left sides, a marked frontal keel, posteriorly divergent temporal lines, a posteriorly flexed anteromedial corner of the mandibular fossa, a bulbous lateral end of the supraorbital torus, and a forward protruding maxillary body with a distinct infraorbital sulcus. LB1 is most similar to early Javanese Homo erectus from Sangiran and Trinil in these and other aspects. We conclude that the craniofacial morphology of LB1 is consistent with the hypothesis that H. floresiensis evolved from early Javanese H. erectus with dramatic island dwarfism. However, further field discoveries of early hominin skeletal remains from Flores and detailed analyses of the finds are needed to understand the evolutionary history of this endemic hominin species.

A Small UAV for Immediate Hazard Map Generation

An unmanned aerial vehicle (UAV) system providing quick response imagery for natural disaster assessment was developed. A prototype UAV and on-board software using a GPS navigation system were developed for this purpose. The flight performance was evaluated by 6DOF simulations and rigorous flight tests. In the proposed system, collected images by an on-board digital camera is transmitted in real-time to a spatial temporal GIS to share the information. The usability of the small UAV system was qualified by a flight experiment in a city-wide emergency evacuation drill.

New reconstruction and morphological description of a Homo erectus cranium: skull IX (Tjg-1993.05) from Sangiran, Central Java.

Skull IX (Tjg-1993.05) was unearthed from the upper stratigraphic zone (Bapang-AG levels) of the hominin-bearing sequence in Sangiran. This remarkably complete cranial specimen of Homo erectus from the early Pleistocene of Java preserves substantial portions of the vault and face. However, the distortion present in the original reconstruction has hampered detailed documentation of its morphological characteristics. We here report a new reconstruction of Skull IX that successfully recovers the original morphology and significantly differs from previous reconstructions. Detailed morphological description and the results of initial comparative analyses based on this new reconstruction are provided. The endocranial volume of Skull IX was measured as 870 cc using micro-CT data. The neurocranium of Skull IX is slightly smaller than the so far recorded smallest cranium from this zone, suggesting this individual was female. In most, but not all, aspects of the cranial vault form, details of the external surface structures, and facial morphology, Skull IX exhibits numerous similarities to the other Bapang-AG H. erectus specimens, indicating that it belonged to the Bapang-AG H. erectus population. Drawing on the expanded fossil sample of this chronoregional H. erectus group, we discuss their evolutionary status, degree of sexual dimorphism, and facial morphological variation in Afro-Asian earlier Homo specimens.

A Diploblastic Radiate Animal at the Dawn of Cambrian Diversification with a Simple Body Plan: Distinct from Cnidaria?

Background Microfossils of the genus Punctatus include developmental stages such as blastula, gastrula, and hatchlings, and represent the most complete developmental sequence of animals available from the earliest Cambrian. Despite the extremely well-preserved specimens, the evolutionary position of Punctatus has relied only on their conical remains and they have been tentatively assigned to cnidarians. We present a new interpretation of the Punctatus body plan based on the developmental reconstruction aided by recent advances in developmental biology. Results Punctatus developed from a rather large egg, gastrulated in a mode of invagination from a coeloblastura, and then formed a mouth directly from the blastopore. Spiny benthic hatchlings were distinguishable from swimming or crawling ciliate larvae found in cnidarians and sponges. A mouth appeared at the perihatching embryonic stage and was renewed periodically during growth, and old mouths transformed into the body wall, thus elongating the body. Growing animals retained a small blind gut in a large body cavity without partitioning by septa and did not form tentacles, pedal discs or holdfasts externally. A growth center at the oral pole was sufficient for body patterning throughout life, and the body patterning did not show any bias from radial symmetry. Conclusions Contrary to proposed cnidarian affinity, the Punctatus body plan has basic differences from that of cnidarians, especially concerning a spacious body cavity separating ectoderm from endoderm. The lack of many basic cnidarian characters in the body patterning of Punctatus leads us to consider its own taxonomic group, potentially outside of Cnidaria.

Virtual Endocast of Qafzeh 9: A Preliminary Assessment of Right-Left Asymmetry

We performed a semi-virtual reconstruction of the endocast for Qafzeh 9, a representative of early anatomically modern humans in the Near East, by using sequential CT images of the present cranial reconstruction with manual clay infilling of the gap and missing portions in the inner cranial surface. After assessing the reconstructed virtual endocast in terms of right-left (R-L) asymmetry, we morphed it in such a manner that the observed asymmetry reduced and fit into the range of variation observed in recent humans. The assessment suggests that the present reconstruction of the Qafzeh 9 cranium, possessing a significant degree of R-L asymmetry, suffers from distortion. Directly measured endocranial volumes (1411 cc for the original reconstruction and 1477 cc for the morphed version) were smaller than previously published data (1531 cc) using least-square regression equations. After morphing, the endocast was higher at the middle cranial fossa and narrower at the frontal lobe, both characteristics falling within the range of recent human variation. Although the reconstructed Qafzeh 9 endocasts of both the original and morphed versions fit into the endocranial evolution among lineages of the genus Homo, many fossil crania may have undergone a substantial degree of taphonomic deformation. Therefore, application of possible corrections or hypothesis of plausible taphonomic scenarios should be part of a reasonable assessment of a single precious fossil specimen.

Cerebellar Size Estimation from Endocranial Measurements: An Evaluation Based on MRI Data

Cerebellar volume (CBV) estimation of fossil hominins can help in understanding the evolution of modern behavior, considering that recent neurological studies suggest significant contribution of the cerebellum to high cognitive abilities of modern humans. However, there has been no reliable methods to estimate the CBV from the endocranial cavity. In order to develop the method, the correlation between CBV and the volume and linear measurements of the posterior cranial fossa (PCF), which were taken from MRI data of thirty-two Japanese subjects, was examined. Estimation equations were then obtained from the bivariate relationships and the validity were evaluated based on prediction intervals. We found that, among the PCF metrics we examined, PCF volume was most highly correlated with CBV (r = 0.88), and the estimation equation provides CBV estimates with the error of about ±12 cc for specimens from the reference population sample. This result could offer a promising prospect for CBV estimation of fossil hominins including Neanderthal examples.

High Angle of Attack Flight of a Wing-in-Propeller- Slipstream Mini Unmanned Aircraft

A prototype tail-sitter mini unmanned aircraft (SkyEyeV) was developed and tested in a wind tunnel and semi-automatic flights. A tail-sitter is an aircraft that takes off and lands on its tail section with the fuselage pointing upwards. A key feature of the prototype is the leading edge slats, which are incorporated in its design to avoid stall during flight at high angles of attack. Through wind tunnel testing—aerodynamic force measurements and airflow visualization via tuft method—it was confirmed that the slats increase the stall angle of attack not only in the non-powered condition (without propeller) but also in the powered condition (wing in propeller slipstream). On conducting semi-automatic flight testing, the vehicles flight characteristics were verified, and several useful insights were obtained requiring further investigation.