Ramapithecus and Sivapithecus from China: Some implications for higher primate evolution

The pattern of overall dental dimensions in over 900 teeth of ramapithecines from Lufeng in China is examined using frequency distribution histograms and fitted normal curves, and compared with data for extant hominoids. A prior study has demonstrated unequivocally that at least two groups of animals must have existed at Lufeng [Wu and Oxnard, 1983; Oxnard, 1983a]. The present investigation confirms this finding in more detail. In addition it shows that one fossil group possesses smaller teeth with a lesser degree of sexual dimorphism and approximately equal numbers of adult males and females, and the other possesses larger teeth with a rather larger degree of sexual dimorphism and a female-male ratio that may have approximated from as low as 2:1 to as high as 4:1. Comparisons of patterns of difference along the tooth row demonstrate that both these forms differ from modern apes in their sexual dimorphism, the smaller form being more like humans than the larger, which is more like apes, especially orangutans. Comparisons of the areas of the canine teeth with each of the other functional segments of the tooth row again show that the smaller form is basically similar to modern humans and that the larger resembles extant great apes. Comparisons of other functional dental areas seem to relate to dietary and masticatory functions. Thus the cutting areas are large relative to the chewing areas in omnivorous humans, whereas in the essentially vegetarian great apes this ratio is smaller. The smaller fossil resembles the human condition and may have been somewhat omnivorous; the larger one more resembles the apes and may have been somewhat more vegetarian. However, these comparisons also show that the way in which the larger form resembles the apes is associated with special development of the canines, which is different from that in any modern ape. Comparisons show that the canines in the larger form project far beyond the normal line of tooth crowns. Finally, comparisons show that canine sexual dimorphism in height is marked in the larger form. Neither of these last two features is true of the smaller fossil. These findings have implications for our understanding of the evolution of early pongids and hominids, and for the evolution of primate sexual dimorphisms and dental mechanisms.     

Quantitative differences in dental microwear between primate species with different diets and a comment on the presumed diet of Sivapithecus

Studies of dental microwear have been used to relate tooth form to function in a variety of recent and extinct mammals. Probably the most important aspect of microwear analysis is the possibility of using it to deduce the diet of extinct animals. Such deductions must be based on comparative studies of modern species with known diets, but to date, only qualitative studies have been attempted and all have been based on small samples. Here we report quantitative differences in dental microwear between primate species that are known to have different diets. Occlusal facets with different functions have previously been shown to exhibit different microwear patterns. However, the differences between facets of one species are shown to be far less than those between homologous facets of different species. Study of seven species of extant primates shows that enamel microwear can be used to distinguish between those with a mainly frugivorous diet and those with a mainly folivorous one. Microwear can also distinguish hard-object feeders from soft-fruit eaters. The microwear of Miocene Sivapithecus indicus cannot be distinguished statistically from that of the chimpanzee, but it is different from that of the other species. On this evidence S. indicus was not a hard-object feeder and the adaptive significance of its thick molar enamel is at present unknown.     

Australopithecine taxonomy and phylogeny in light of facial morphology

The beginning of specialization characterizing the robust australopithecines is manifested in almost every aspect of the masticatory system of Australopithecus africanus. Of particular significance is the presence of two massive bony columns on both sides of the nasal aperture that support the anterior portion of the palate. These columns--the anterior pillars--are viewed as a structural response to the greater occlusal load stemming from the beginning stages of molarization of the premolars and exerted on the more anterior part of the dental arcade. In A. africanus the molarization process is, indeed, just in its initial phase, but the still considerable protrusion of the palate relative to the more peripheral facial frame increases the need for pillars. The anterior pillars and the advancement of the inferior part of the infraorbital plate (the origin of the masseter) play a major role in molding the facial topography of A. africanus. The absence of the pillars and the common position of the masseteric origin lead us to define the face of A. afarensis as the most primitive of the australopithecines and allow us to discriminate between its facial morphology and that of A. africanus. The presence of anterior pillars in the face of the latter places it clearly in the robust australopithecine clade.     

Cross-sectional morphology of the SK 82 and 97 proximal femora

Computed tomography scans of the proximal femoral shaft of the South African “robust” australopithecine, A. robustus, reveal a total morphological pattern that is similar to the specimen attributed to A. boisei in East Africa but unlike that of Homo erectus or modern human femora. Like femora attributed to H. erectus, SK 82 and 97 have very thick cortices, although they do not have the extreme increase in mediolateral buttressing that is so characteristic of H. erectus. And unlike H. erectus or modern humans, their femoral heads are very small relative to shaft strength. These features are consistent with both increased overall mechanical loading of the postcranial skeleton and a possibly slightly altered pattern of bipedal gait relative to that of H. erectus and modern humans. Am J Phys Anthropol 109:509–521, 1999. © 1999 Wiley-Liss, Inc.     

Dental metric assessment of the omo fossils: implications for the phylogenetic position of Australopithecus africanus

The discovery of Australopithecus afarensis has led to new interpretations of hominid phylogeny, some of which reject A. africanus as an ancestor of Homo. Analysis of buccolingual tooth crown dimensions in australopithecines and Homo species by Johanson and White (Science 202:321-330, 1979) revealed that the South African gracile australopithecines are intermediate in size between Laetoli/hadar hominids and South African robust hominids. Homo, on the other hand, displays dimensions similar to those of A. afarensis and smaller than those of other australopithecines. These authors conclude, therefore, that A. africanus is derived in the direction of A. robustus and is not an ancestor of the Homo clade. However, there is a considerable time gap (ca. 800,000 years) between the Laetoli/Hadar specimens and the earliest Homo specimens; "gracile" hominids from Omo fit into this chronological gap and are from the same geographic area. Because the early specimens at Omo have been designated A. afarensis and the later specimens classified as Homo habilis, Omo offers a unique opportunity to test hypotheses concerning hominid evolution, especially regarding the phylogenetic status of A. africanus. Comparisons of mean cheek teeth breadths disclosed the significant (P less than or equal to 0.05) differences between the Omo sample and the Laetoli/Hadar fossils (P4, M2, and M3), the Homo fossils (P3, P4, M1, M2, and M1), and A. africanus (M3). Of the several possible interpretations of these data, it appears that the high degree of similarity between the Omo sample and the South African gracile australopithecine material warrants considering the two as geographical variants of A. africanus. The geographic, chronologic, and metric attributes of the Omo sample argue for its lineal affinity with A. afarensis and Homo. In conclusion, a consideration of hominid postcanine dental metrics provides no basis for removing A. africanus from the ancestry of the Homo lineage.     

Functional morphology of the asterionic region in extant hominoids and fossil hominids

Asterionic sutural patterns in Plio-Pleistocene hominid crania have never been examined in detail. We present an analysis of this anatomical region in Australopithecus and Homo and relate different sutural patterns to functional changes in the masticatory apparatus. The great apes and A. afarensis share the common adult higher primate sutural pattern referred to as the "asterionic notch," which develops in response to the hypertrophy of posterior temporalis muscle fibers and the consequent formation of compound temporal/nuchal crests. This sutural configuration also appears to be present on the early Homo cranium KNM-ER 1805. In contrast, adult male A. boisei crania exhibit a unique pattern where the temporal squama overlaps the parietal which, in turn, overlaps the par mastoidea and the upper scale of the occipital bone. We relate this arrangement to the need to reinforce the rear of a thin-walled braincase against the net tensile forces exerted by the temporalis and nuchal muscles. The common juvenile hominoid edge-to-edge asterionic articulation is maintained in adult A. africanus, A. robustus, female A. boisei, and most Homo crania. We discuss the latter pattern in regard to anterior temporalis hypertrophy in A. africanus, A. robustus, and A. boisei and to craniofacial paedomorphosis in Homo.     

Molar crown formation in the Late Miocene Asian hominoids, Sivapithecus parvada and Sivapithecus indicus

During the past decade, studies of enamel development have provided a broad temporal and geographic perspective on evolutionary developmental biology in Miocene hominoids. Here we report some of the first data for molar crown development in one hominoid genus, Sivapithecus. The data are compared to a range of extant and extinct hominoids. Crown formation times (CFTs), daily rates of enamel secretion (DSR), Retzius line number and periodicity, and relative enamel thickness (RET) were calculated in a mandibular first molar of Sivapithecus parvada and a maxillary first molar of Sivapithecus indicus from the Siwalik sequence of Pakistan. A CFT of 2.40 years for the protoconid of S. parvada and 2.25 years for the protocone of S. indicus lie within the range of first molar (M1) formation times for the majority of Miocene hominoids (1.96-2.40 years, excluding Proconsul heseloni), and are similar to an M(1) from Gorilla (2.31 years) and M(1)s from Pan (2.22-2.39 years). This is unlike the longer CFTs in modern humans, which appear to be linked with their extended growth period. In contrast to extant great apes and humans, daily rates of enamel secretion are rapid in the Sivapithecus M1s during the early stages of growth, which seems to be a common pattern for most Miocene apes. The rapid accumulation of cuspal enamel in the Sivapithecus molars produced thicker enamel than either Pan or Gorilla in a comparable period of time. Future studies on larger samples of living and fossil hominoids are needed to clarify trends in crown development, which may be better understood in the context of life history strategies coupled with good data on body mass and brain size.     

Seed morphology and anatomy of Austrotaxus spicata (Taxaceae) and its systematic position

The anatomy and ultrastructure of seed envelopes of a New Caledonian endemic Austrotaxus spicata were examined for the first time. The systematic position and phylogenetic relations of Austrotaxus were analysed in light of these data. The structure of aril and spermoderm were investigated to demonstrate the similarities with Phyllocladus as well as with Taxus and Pseudotaxus . On the basis of all female reproductive organ characters, Austrotaxus appeared to be fairly isolated and its placing in the independent family Austrotaxaceae was confirmed from the standpoint of comparative anatomy of the seed coat. Taking into consideration that the heterobathmy of features can be the most distinctively traced in the structure of reproductive organs, evaluating the extent of evolutionary advancement of Austrotaxus seems to be rather difficult. However, it is evident that the relationship of Austrotaxus either with Taxaceae or with Podocarpaceae s.l . is considerably remote.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 145 , 437–443.     

Mandibular postcanine dentition from the Shungura Formation,Ethiopia: Crown morphology,taxonomic allocations,and Plio-Pleistocene hominid evolution

Over 200 hominid specimens were recovered by the International Omo Expedition of 1967–1976. Despite the fragmentary nature of this primarily dental collection, these hominid remains represent a major body of evidence about hominid evolution in eastern Africa during the 2–3 myr time period. Our analysis of the Omo dental collection is based on a large comparative sample of 375 quantifiable mandibular postcanine teeth of A. afarensis, A. africanus, A. aethiopicus, A. boisei, A. robustus, and early Homo. A total of 48 isolated mandibular premolars and molars of the Omo collection spanning the 2–3 myr time period is sufficiently preserved to allow reliable serial allocations and intertaxon comparisons and is the object of study in this paper. We present taxonomic identifications of these teeth and seven other mandibular specimens preserving tooth crowns. Metric analyses of this study include cusp area and crown shape variables taken on occlusal view diagrams. Nonmetric analyses were based on simultaneous observations of all relevant material to ensure accuracy of categorical evaluations. First, a combined metric and morphological evaluation was conducted to allocate each Omo tooth to either robust or nonrobust categories. Further taxonomic affinities were then examined. Our results indicate that nonrobust and robust lineages cooccur by circa 2.7 myr. We consider the Shungura robust specimens from Members C through F to represent A. aethiopicus. A significant phenetic transformation occurs at circa 2.3 myr, with the mosaic emergence of the derived A. boisei morphology across Member G times. Characterization of the East African nonrobust lineage is more difficult because of the comparatively subtle morphological differences seen among the dentitions of A. afarensis, A. africanus, and early Homo. The earlier Members B and C nonrobust specimens are difficult to evaluate and are considered indeterminate to genus or species. Both molars and premolars from Members E through G exhibit phenetic similarities to the early Homo condition and are considered as aff. Homo sp. indet. At present, there is no indication of multiple species in the Omo nonrobust sample at any time horizon. The 2–2.4 myr Omo nonrobust specimens exhibit some similarities to the stated Homo “rudolfensis” condition in size and morphology and are likely to represent the ancestral condition of the genus Homo. The bearing of these results on interpretations of early hominid evolution and diversification is considered. © 1996 Wiley-Liss, Inc.     

The morphology and systematic position of Prionotylus Fieber and Centroplax Horvath (Heteroptera: Coreidae)

An account is given of several aspects of the morphology of the genera Prionotylus Fieber and Centroplax Horváth. The systematic position of these genera within the family Coreidae and the generic assignment of Prionotylus meridianus Villiers are considered.     

鼻腔结构影响人体嗅觉反应的数值模拟

采用一个符合实际解剖学的鼻腔结构,建立了鼻腔仿生模型和气味分子传输过程的控制方程,应用ANSYS软件,对鼻腔流场进行了数值模拟。结果显示吸气速度越大,流过嗅觉区的气味分子越多,越容易产生嗅觉;鼻腔入口处到嗅觉区的距离越短,流过嗅觉区的气味流量越大,越容易产生嗅觉。从而,丰富了嗅觉理论,使人们进一步认识嗅觉,为人工嗅觉提供了仿生理论依据。     

Contributions to the morphology,anatomy, and karyology ofRhabdodendron,and a reconsideration of the systematic position of theRhabdodendronaceae

Rhabdodendron macrophyllum (Spruce ex Benth.)Huber andR. amazonicum (Spruce exBenth.)Huber differ in several anatomical and morphological characters (secretory cavities, hypoderm, peltate hairs, internodal region and petiole). A position of the monotypicRhabdodendronaceae in theCentrospermae as recently suggested is hardly supported: Peltate hairs, lysigenous secretory cavities and spicular cells in the leaves, multilacunar nodes, chromosome number (R. macrophyllum: n = 10; first count for the genus resp. family), ± simultaneous (or slightly centripetal) development of the androeceum, anacrostyly and two ovules in the unicarpellate gynoeceum, apparent disc, monotelic racemes, and data available from literature (pollen, sieve tube plastids) clearly indicate a close affinity toRutaceae, and even make the family rank ofRhabdodendron questionable.     

Development of a computational fluid dynamics model for mucociliary clearance in the nasal cavity

Intranasal drug delivery has attracted significant attention because of the opportunity to deliver systemic drugs directly to the blood stream. However, the mucociliary clearance poses a challenge in gaining high efficacy of intranasal drug delivery because cilia continuously carry the mucus blanket towards the laryngeal region. To better understand mucus flow behaviour on the human nasal cavity wall, we present computational model development, and evaluation of mucus motion on a realistic nasal cavity model reconstructed from CT-scans. The model development involved two approaches based on the actual nasal cavity geometry namely: (i) unwrapped-surface model in 2D domain and (ii) 3D-shell model. Conservation equations of fluid motion were applied to the domains, where a mucus production source term was used to initiate the mucus motion. The analysis included mucus flow patterns, virtual saccharin tests and quantitative velocity magnitude analysis, which demonstrated that the 3D-shell model results provided better agreement with experimental data. The unwrapped-surface model also suffered from mesh-deformations during the unwrapping stage and this led to higher mucus velocity compared to experimental data. Therefore, the 3D-shell model was recommended for future mucus flow simulations. As a first step towards mucus motion modelling this study provides important information that accurately simulates a mucus velocity field on a human nasal cavity wall, for assessment of toxicology and efficacy of intranasal drug delivery.     

Floral ontogeny and systematic position of the Didiereaceae

Floral ontogenetical data from all four genera of the Didiereaceae (s.str.) are presented for the first time. All Didiereaceae s.str. are dioecious, having unisexual flowers with organ rudiments of the opposite sex. Two median bracts followed by a tetramerous perianth (two alternating dimerous ``whorls'), a slightly complex androecium with 6–12 stamens in a single row (on a common ring primordium), four of which mostly alternating with the perianth members, and one basal ovule connecting three free septa at their very base are flower characters in Didiereaceae, supporting phylogenetic analyses based on nucleotide sequence data. Closest relatives are the (formerly) portulacaceous genera Portulacaria (5 stamens alternating with the perianth), Ceraria (5 stamens alternating with the perianth), and Calyptrotheca (many stamens), all with pentamerous perianths, from which the tetramerous perianth in Didiereaceae can be derived. Applequist and Wallace (2003) included these three genera in an expanded family Didiereaceae (with three subfamilies).     

The distribution and systematic position of the Thermosbaenacea

Summary The oasis of El Hamma, southern Tunisia, was visited in September 1950 and 714 specimens of Thermosbaena mirabilis Monod were collected from two baths fed by hot-springs, Ain el Bordj, the type-source, and Ain Sidi Abd el Kadar where the animal had not previously been recorded. The specimens consisted of 164 males, 123 females (73 non-breeding; 50 with brood-pouches), and 94 juveniles; 333 specimens were unfortunately lost on the return journey. Thermosbaena lives in warm brackish water and can survive temperatures fluctuating between 37° and 47° C. but becomes moribund around 35° and dies around 30° C.Apart from examining the springs and baths at El Hamma, a search was made for Thermosbaena in 14 wells and 11 springs scattered over a wide area around El Hamma and Gabès; the River El Hamma was also sampled. The search proved negative in all but the two El Hamma baths already specified. It is suggested that the animal occupies an interstitial habitat in the thermal ground-water at El Hamma, and that it has been collected in the baths not because it has been brought there by the springs flowing into them (as previously believed), but because in the baths the collector has by chance had access to the interstitial habitat. There are grounds for believing that the three species of Monodella discovered on the Italian and Yugoslavian coasts (M. stygicola, M. argentarii, and M. halophila) are also interstitial forms, and that an ancestral habitat in the sea-bed of that part of the Mesogean (Tethys) Sea now represented by the Mediterranean was common to all members of the Thermosbaenacea. The palaeogeographic history of the Mesogean in the North African, Italian, and Yugoslavian areas is discussed and two hypotheses are formulated to account for the present-day habitat of Thermosbaena. The first would regard the organism as a legacy from the final retreat of the Mesogean from southern Tunisia in the lower Eocene. The second envisages the establishment of ancestral stock in a lake lying nearby El Hamma at a time during the Quaternary when a rise in the level of the Mediterranean had converted the lake into a brackish lagoon. This lake subsequently dried out to form the present-day Chott Djerid and it is suggested that Thermosbaena colonized the thermal brackish ground-water at El Hamma as a measure of survival in face of the increasingly saline ground-water of the developing chott. The second hypothesis is regarded as the most plausible. It is considered that the coastal locations of the Monodella species so far discovered indicate a comparatively recent colonization from the sea-bed of the Mediterranean via littoral ground-water. It is pointed out, however, that the palaeogeographic history of Italy and Yugoslavia renders the occurrence of as yet undiscovered species in the Italian and Balkan interior a distinct possibility, the organisms persisting as freshwater or brackish survivors of the Mesogean regression which followed the Pliocene.The systematic position of the Thermosbaenacea is reviewed in the light of recent work and it is concluded that little significance should be attached to the intermediate position of the order between the Peracarida and Syncarida suggested by Taramelli (1954), or to the stomatopodan affinities of the group suggested by Glaessner (1957). It would appear that these relict malacostracans should either be included in the Peracarida, or placed in a pre-peracaridan position as advocated by Siewing (1956, 1958), but the inclusion of the Thermosbaenacea in a new division Pancarida (Siewing, 1958), equivalent in rank to the Peracarida, is clearly premature.

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Sommaire En septembre 1950, au cours d'une visite à El Hamma, oasis au sud de la Tunisie, 714 spécimens appartenant au genre Thermosbaena mirabilis Monod furent récoltés dans deux bassins alimentés par des sources thermales, Ain el Bordj, source typique, et Ain Sidi Abd el Kadar, où jamais encore de tels échantillons n'avaient été trouvés. Cette collection comprenait: 164 mâles, 123 femelles (73 stériles et 50 avec poches reproductrices) et 94 non-adultes. Malheureusement 333 de ces animaux furent perdus durant le voyage de retour. Thermosbaena vit dans une eau chaude et saumâtre, elle peut survivre à des temperatures variant de 37° à 47° C., mais elle commence à s'éteindre aux environs de 35° et meurt aux approches de 30° C.Une recherche pour trouver Thermosbaena fut entreprise, non seulement dans les deux bassins à El Hamma, mais aussi dans 14 puits et sources disséminés sur une large étendue autour d'El Hamma et de Gabès, ainsi que dans la rivière El Hamma dont des échantillons furent analysés. Rien ne fut trouvé en dehors des deux sources mentionnées en premier lieu. On suppose que ces animaux habitent certains interstices dans les fonds des sources thermales d'El Hamma, et qu'ils y ont été trouvés, non pas parce que amenés la par l'écoulement des eaux, mais parce que le collectionneur eut la chance d'acceder à leur terrain d'habitat. Il est raisonnable de croire que les 3 espèces de Monodella trouvées sur les côtes d'Italie et de Yougoslavie (M. stygicola, M. argentarii, et M. halophila) sont aussi du genre habitant des interstices et qu' un ancien habitat, dans les fonds de cette partie de la Mer mésogéenne (Tethys) maintenant réprénté par la Méditerranée était commun à tous les membres des thermosbenacés. L'histoire paléogéographique du Mésogée dans les régions nord-africaines, italiennes, et yougoslaves est en discussion et on formule deux hypothèses pour expliquer le présent habitat de Thermosbaena. La première considérait l'organisme comme un legs de la retraite finale du Mésogée depuis la Tunisie méridionale dans l'Eocène inférieure. La seconde envisage l'établissement d'une réserve ancestrale dans un lac se trouvant près d'El Hamma à une époque où un relèvement du niveau de la Méditerranée avait converti le lac en un lagon saumâtre. Ensuite ce lac s'est asséché pour former l'actuel Chott Djerid et on formule la suggestion que les Thermosbaena ont colonisé l'eau thermale saumâtre à El Hamma comme mesure de survie devant l'eau de plus en plus salée du chott en voie de dévéloppement. La deuxième hypothèse est estimée comme la plus plausible. On considère que la position sur la côte de l'espèce Monodella, dans la mesure où elle a été découverte, indique une colonisation comparativement récente partant du lit de la Méditerranée par l'intermédiaire des eaux littoraux. On souligne, cependant, que l'histoire paléogéographique de l'Italie et de la Yougoslave fait de la trouvaille d'espèces non encore découvertes dans l'Italie et l'intérieur des Balkans une possibilité distincte, les organismes persistant comme survivants d'eau douce ou saumâtre de la regression mésogéene qui suivit le Pliocène.La position systématique des thermosbenacés a été mise au point au cours de trauvaux récents, et l'on arrive à conclure que la position intermédiaire de l'ordre entre la Peracarida et la Syncarida, comme suggeré par Taramelli (1954), ou les affinités stomatopodéennes au groupe suggeré par Glaessner (1957) signifient peu de choses. Il semblerait que ces résidus malacostracéens devraient être inclus à la Peracarida ou placés dans une position pré-peracaridéenne, comme le recommande Siewing (1956, 1958), mais établir que les thermosbenacés sont une branche nouvelle Pancarida (Siewing, 1958) à un rang semblable à la Peracarida, serait certainement une conclusion prematurée.

     

Reevaluation of the systematic position of Scenella

Specimens originally illustrated from Lower Cambrian rocks of the Sierra Morena in Badajoz and Sevilla Provinces, southwestern Spain are supplemented by new material from another locality and are described as Scenella morenensis n. sp. Although Scenella was originally considered to be a patelliform gastropod, for three decades now the genus has been classified as a monoplacophoran. The type species of Scenella, S. reticulata Billings, does not show any paired muscles scars, nor does this new species; such scars are indicative of the Monoplacophora. This new species of Scenella does exhibit features which suggest assignment to the chondrophorine coelenterates. If so, Scenella cannot represent the ancestral form of mollusk.