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PubMed2004

Mantle segmentation along the Oman ophiolite fossil mid-ocean ridge.

It has been difficult to relate the segmentation of mid-ocean ridges to processes occurring in the Earth's underlying mantle, as the mantle is rarely sampled directly and chemical variations observed in lavas at the surface are heavily influenced by details of their production as melt extracted from the mantle. Our understanding of such mantle processes has therefore relied on the analysis of pieces of fossil oceanic lithosphere now exposed at the Earth's surface, known as ophiolites. Here we present the phase chemistry and whole-rock major- and trace-element contents of 174 samples of the mantle collected along over 400 km of the Oman Sultanate ophiolite. We show that, when analysed along the fossil ridge, variations of elemental ratios sensitive to the melting process define a three-dimensional geometry of mantle upwellings, which can be related to the segmentation observed in modern mid-ocean ridge environments.

Journal Article↗

PubMed2001

Genetic diversity and evolutionary relationships of the troglodytic "living fossil" Congeria kusceri (Bivalvia: Dreissenidae).

Population genetic theory predicts that long-term isolation of "living fossils" in relic habitats might reduce genetic variability due to small population sizes and inbreeding. The recent description of a troglodytic "living fossil" Congeria kusceri--the only known subterranean bivalve mollusc--from a genus thought to be extinct since the Miocene, offers a unique opportunity to examine this hypothesis. Here, we use DNA sequences from two mitochondrial genes to compare levels of genetic variability and to test phylogenetic relationships of C. kusceri with surface-dwelling dreissenid relatives. Phylogenetic analyses of sequences from the cytochrome oxidase 1 (COI) and 16S rDNA genes reveal that Mytilopsis is the sister genus to Congeria and this clade forms the sister taxon to Dreissena. Relatively high levels of DNA diversity characterized the population of C. kusceri (haplotypic diversity= 0.50 for 16S rDNA and 0.66 in the COI gene), in contrast to no intraspecific variability in populations of Dreissenapolymorpha, D. bugensis, Mytilopsisleucophaeta, and Corbiculafluminea. Maintenance of genetic variability in C. kusceri may result from long-term population size stability, which merits further investigation. This underground species apparently was buffered from the climatic changes and resultant population bottlenecks that affected its surface-dwelling relatives during the Pliocene and Pleistocene Ice Ages.

Animals↗

PubMed1988

The oldest fossil bee: Apoid history, evolutionary stasis, and antiquity of social behavior.

Trigona prisca, a stingless honey bee (Apidae; Meliponinae), is reported from Cretaceous New Jersey amber (96-74 million years before present). This is about twice the age of the oldest previously known fossil bee, although Trigona is one of the most derived bee genera. T. prisca is closely similar to modern neotropical species. Most of bee evolution probably occurred during the approximately 50 million years between the beginning of the Cretaceous when flowering plants (on which bees depend) appeared and the time of T. prisca. Since then, in this phyletic line of Meliponinae, there has been almost no morphological evolution. Since the fossil is a worker, social organization had arisen by its time.

Journal Article↗

PubMed1993

Structural biopolymer preservation in Miocene leaf fossils from the Clarkia site, northern Idaho.

The 17- to 20-million-year-old locality at Clarkia, northern Idaho, is renowned for yielding amplifiable DNA from a magnolia leaf fossil. In-source pyrolysis-mass spectrometry and pyrolysis-gas chromatography/mass spectrometry now reveal that molecular preservation of biomacromolecules is highly selective; structural polysaccharides, cutin polyesters, and proteins were not preserved in detectable quantity in the leaf tissues, whereas both lignin and an aliphatic biopolymer were detected. This study points up the need for improved understanding of the precise modes and extent of preservation of biomacromolecules in fossil materials and sediments.

Journal Article↗

PubMed1996

DNA, morphology and fossils: phylogeny and evolutionary rates of the gastropod genus Littorina.

Using data from the direct sequencing of fragments of three mitochondrial genes (12S and 16S ribosomal RNA, and cytochrome-b; total length 1469 b.p.) we have reconstructed a gene phylogeny for all 19 living species of the gastropod genus Littorina. Members of the closely related genera Nodilittorina, Littoraria and Mainwaringia have been used as outgroups, and it appears that Littorina is monophyletic. An earlier morphological phylogeny has been revised, and its topology found to be almost entirely consistent with that from the molecular data. The fossil record is sparse, but likewise consistent. A consensus tree is presented, showing clear resolution of basal and terminal branches, and a central unresolved polychotomy. We have used fossil evidence and geological events to estimate the ages of some clades, and thus to calculate average rates of molecular evolution, which in turn provide approximate dates for all branches of the molecular phylogeny. The central polychotomy may be explained by a burst of rapid speciation in the northwestern Pacific during the Middle Miocene, perhaps driven by climatic fluctuation. Our results support the hypothesis that the two clades of Littorina in the northern Atlantic originated from Pacific ancestors which took part in the Pliocene trans-Arctic migration of marine organisms.

Animals↗

PubMed2006

Inconsistency of the maxilla and mandible in the Minatogawa Man No. 1 hominid fossil evaluated from dental occlusion.

The Minatogawa man hominid fossils are human fossils from Japan and the oldest from the Late Pleistocene period. Of the Minatogawa skeletal remains, Minatogawa Man No. 1 is best preserved and is accompanied by the mandible. When the maxillary and mandibular dentitions of Minatogawa Man No. 1 were occluded, the dentitions did not align with one another. The attrition pattern of the maxillary teeth was of an inclined type, which tilted from the buccal to lingual side, whereas that of the mandibular dentition was of a horizontal type. Moreover, both left maxillary and mandibular third molars exhibited attrition on the distal portion of the occlusal surface. The occlusal surfaces did not complement each other in the range of mandibular movement without temporomandibular joint dislocation and the curve of Spee produced by the left maxillary and mandibular occlusal planes did not match. These findings suggest that the maxilla and mandible of Minatogawa Man No. 1 are, in fact, from different individuals.

Dental Occlusion↗

PubMed1976

Morphological cerebral asymmetries of modern man, fossil man, and nonhuman primate.

Cerebral asymmetries are common in modern and fossil man and the great apes. Those occurring most often are listed here: 1. The left sylvian fissure in man is longer than the right and in both fetal and adult brains the posterior end of the right sylvian fissure is commonly higher than the left. Associated with these findings, the left planum temporale is usually longer than the right. 2. The left occipital pole is often wider and usually protrudes more posteriorly than the right. 3. The left lateral ventricle, and especially the occipital horn, is usually larger than the right. 4. If one frontal pole extends beyond the other it is usually the right. 5. On X-ray computerized axial tomograms (CT) of the brain the right frontal lobe and the central portion of the right hemisphere more often measure wider than the left. 6. The CT studies commonly show a Yakovlevian anticlockwise torque (taking the nose as 12 o'clock), with the left occipital pole longer and often extending across the midline toward the right and a wider right hemisphere in its central and frontal portions and frequent forward protrusion of the right frontal pole. This is found also in newborns. 7. The posterior end of the sagittal sinus usually lies to the right of the midline and the sinus flows more directly into the right transverse sinus than into the left. 8. The right transverse sinus is usually higher than the left. 9. In left-handed and ambidextrous individuals the posterior ends of the sylvian fissures are more often nearly equal in height and the occipital regions are more often equal in width or the right may be wider. 10. The torque of the pyramidal tract and the hemispheral torque cannot at present be related to right- or left-handedness. Statistics concerning left-handedness are somewhat confounded, because it is likely that not a few individuals are left-handed because of an early injury of the left hemisphere in a normally right-handed individual. 11. Cerebral asymmetries are found in fossil man similar to those in modern man. 12. Asymmetries of the sylvian fissures similar to those of modern man have been found in the great apes and are particularly common in the orangutan. 13. The most striking and consistently present cerebral asymmetries found in adult and fetal brains are in the region of the posterior end of the sylvian fissures-- the areas generally regarded as a major importance in language function.

Adolescent↗

PubMed1968

Radiocarbon: analysis of inorganic carbon of fossil bone and enamel.

Carbon dioxide from calcium carbonate in fossil bone can be selectively separated from carbon dioxide in bone apatite by hydrolyzing the sample first in acetic acid and then in hydrochloric acid. Radiocarbon analyses of the inorganic carbon dioxide in three samples of known age clearly show calcium carbonate in fossil bone to be secondary and the carbonate of bone apatite to be indigenous and suitable for dating in some cases. Agreement between dates on collagen-bone apatite pairs increases the level of confidence.

Acetates↗

PubMed2000

Fossil legumes from the Middle Eocene (46.0 Ma) Mahenge Flora of Singida, Tanzania.

Middle Eocene age caesalpinioid and mimosoid legume leaves are reported from the Mahenge site in north-central Tanzania. The Mahenge flora complements a sparse Paleogene tropical African fossil plant record, which until now consisted of a single macrobotanical assemblage, limited palynological studies in West Africa and Egypt, and fossil wood studies primarily from poorly dated deposits. Mahenge leaf macrofossils have the potential to add significantly to what is known of the evolutionary history of extant African plant groups and to expand our currently limited knowledge of African Paleogene environments. The site is associated with a kimberlite eruption and demonstrates the potential value of kimberlite-associated lake deposits as much-needed resources for African Paleogene floras. In this report we document a relatively diverse component of the flora consisting of the leaves of at least five species of Leguminosae. A new species of the extant genus Acacia (Mimosoideae), described herein, is represented by a bipinnate leaf. Another taxon is described as a new species of the extant genus Aphanocalyx (Caesalpinioideae), and a third leaf type may be related to the extant genus Cynometra (Caesalpinioideae). Two additional leaf types are less well understood: one appears to be referable to the Caesalpinioideae and subfamily affinities of the other taxon are unknown.

Journal Article↗

PubMed2001

Fossil flowers of ericalean affinity from the Late Cretaceous of Southern Sweden.

Charcoalified fossil flowers of a new genus and species (Paradinandra suecica) with affinities to Ericales s.l. (sensu lato) are described from the Late Cretaceous (Santonian-Campanian) from Southern Sweden. The flowers are pentamerous, hypogynous, and actinomorphic. Aestivation of sepals and petals is imbricate-quincuncial. The androecium consists of an outer whorl with single episepalous stamens and an inner whorl with paired epipetalous stamens. Pollen is small and probably tricolpate. Three carpels form a syncarpous ovary with numerous campylotropous ovules on parietal placentae. The styles are free for most of their length. The structure of mature fruits and seeds is unknown. Clear distinction of sepals and petals, possible dehiscence of anthers by restricted slits, presence of a nectary, and the general floral construction (salverform corolla) with a canalized access to the floral center clearly indicate insect pollination of the fossil flowers. Comparisons with extant taxa demonstrate that Paradinandra suecica shares many similarities with Ericales s.l. and in particular with members of Ternstroemiaceae, Theaceae, and Actinidiaceae. However, it is neither identical to any one genus of these families nor to any of the previously described ericalean taxa from the Cretaceous and thus provides further evidence of the diversity of Cretaceous ericalean plants.

Journal Article↗

PubMed2002

Effect of diatomaceous earths Fossil Shield and Silico-Sec on the egg laying behaviour of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae).

The pulse beetle, Callosobruchus maculatus (F.) is a destructive pest of pulses in both storage and field. It is well known that diatomaceous earth (DE) kill the insects by locally absorbing the epicuticular lipid layers leading to high rate of water loss through the cuticle. However, the effectiveness of DE depends on its ability to kill the adults before copulation and egg-laying. Newly emerged virgin males and females of Callosobruchus maculatus (F.) were exposed to the DEs, Fossil-Shield and Silico-Sec on 30 treated mungbeans (Vigna radita (L)). Fecundity, number of beans used for egg-laying and beans without eggs were evaluated after four days; the number of unhatched eggs was evaluated after ten days. It was determined, that the fecundity of female insects decreased sigmoidely with increasing rate of DE content. Percentages of unhatched eggs and seeds without eggs increased with increasing DE dosages. However, the maximum egg densities (eggs per used secd) occurred at 1200 mg DE/kg for Fossil-Shield and Silico-Sec. The reason for such DE-stimulated behaviour of egg laying expressed as a number of seeds with eggs of C. maculatus is not known, but it may be related to the stress caused by the inert dusts or to the reduction of both chemical and physical (tactile) stimuli. Treatment with DEs altered the surface texture of the beans and caused less cohesion between eggs and the seed surface. Only few larvae managed to penetrate into the grains, possibly due to increased grain roughness and repellent effect of DE. A relatively high number of eggs were laid on the surface of those beans where the amount of dust had been locally reduced by adults' movement and their pick up of DE. Therefore, several larvae tried to penetrate into these treated beans, causing a high larval density per partially cleaned bean. All these reasons lead to a progeny decline.

Animals↗

PubMed2004

[Recent rhinos do not lack character(s): neither do fossil rhinos!].

Concepts, methods, and interest of phylogenetic reconstruction are briefly examined. As large data sets are considered and refutable results are proposed, there is no need to use the argument of authority concerning relationships between taxons. Cladistic analysis in vertebrate palaeontology has gained considerable strength in the last decade, based on sets of hundreds of anatomical characters. One example is selected, which concerns the rhino family, i.e. rhinocerotids. Although underrepresented in recent times, these perissodactyl mammals flourished throughout the Cenozoicera (4 recent genera vs. 50 fossil genera). The main results of a recent cladistic analysis of elasmotheriine rhinocerotids, based on 282 anatomical characters, are listed. Such results concern phylogenetics (monophyly of both elasmotheriines and recent rhinos; branching of elasmotheriines among rhinocerotids) and methodology (definition of a "branching group"; location and processing of homoplasy; influence of taxonomic sampling). The implications are both biostratigraphical and palaeobiogeographical (evolution of the diet and spatial distribution; intercontinental dispersals; ghost lineages and heuristic use of the phylogenetic tree). Finally, forthcoming developments of the available data set for rhinocerotids are examined: controversial phylogenetic relationships among recent rhinos will be refined (thanks to close extinct taxa) and an exhaustive phylogeny of fossil and recent rhinocerotids will be reconstructed (54 genera).

Animals↗

PubMed1996

New specimens of the oldest fossil platyrrhine, Branisella boliviana, from Salla, Bolivia.

During the 1992 and 1993 field seasons, several new specimens of Branisella boliviana, the oldest fossil platyrrhine, were discovered in the late Oligocene deposits at Salla, northwestern Bolivia. The new materials are two maxillary fragments and seven mandibular fragments, including P3 and P2, neither of which have previously been recovered. All new and previously reported materials, including the holotype and referred specimens, were apparently recovered from the same horizon, called the Branisella zone (MacFadden et al. [1985] J. Geol. 93:223-250; MacFadden [1990] J. Hum. Evol. 19:7-21. The crown morphology of the newly discovered upper and lower premolars suggests that Branisella has a close affinity with callitrichines. A detailed examination of all molar specimens suggests that "Szalatavus attricuspis," which was recovered at Salla in 1981 and described as a new genus by Rosenberger et al. (1991), is a junior synonym of Branisella. The Branisella-like upper molar, in which a small hypocone is preserved on the poorly developed distolingual cingulum, is a shared-derived character with callitrichines and does not correspond to the primitive state for platyrrhine phylogeny. The ancestral upper molar morphotype for platyrrhines should have a moderate to large hypocone and a well developed talon area.

Animals↗

PubMed1996

Dietary inferences through buccal microwear analysis of middle and upper Pleistocene human fossils.

Buccal microwear has been studied in a sample of 153 molar teeth from different modern hunter-gatherer, pastoralist, and agriculturalist groups, with different diets (Inuit, Fueguians, Bushmen, Australian aborigines, Andamanese, Indians from Vancouver, Veddahs, Tasmanians, Lapps, and Hindus), preserved at museum collections. Molds of an area of the buccal surface have been obtained and observed at 100x magnification in a scanning electron microscope (SEM). The length and orientation of each striation have been determined with a semiautomatic program of an image analyzer system (IBAS). Results show that intergroup variability is significantly higher than the intragroup variability. There exists a tendency toward fewer striations and a higher proportion of vertical striations in the carnivorous groups than in the vegetarian ones. This microwear pattern is concordant with biomechanics (predominantly vertical mandible movements in meat eaters) and phytolith content in plants (more abrasive particles in vegetarian diets). The variability found has been used in a multivariate analysis as a base to compare the microwear pattern of a sample of 20 Middle and Upper Pleistocene fossils, mainly from Europe, analyzed with the same methodology. The sample includes specimens usually classified as archaic H. sapiens (Broken Hill, Banyoles, Montmaurin, La Chaise-Suard, La Chaise-Bourgeios et Delaunay), Neanderthal (La Quina V, Gibraltar 2, Tabun 1 and 2, Amud 1, Malarnaud, St. Cesaire, Marillac), and anatomically modern H. sapiens (Skhül 4, Qafzeh 9, Cro-Magnon 4, Abri-Pataud, Veyrier, La Madelaine, Rond-du-Barry). Results indicate that some of the Neanderthal specimens have a microwear pattern close to that of the carnivorous groups (such as Inuit and Fueguians), suggesting that these individuals follow a hunter strategy. In contrast, archaic H. sapiens and H. sapiens sapiens seem to have a more abrasive diet, probably more depending on vegetable materials, than the Neanderthals.

Analysis of Variance↗

PubMed1996

Allometric patterns of cranial bone thickness in fossil hominids.

The interspecific allometry of five measures of total cranial bone thickness is examined in 10 extant catarrhine genera and two fossil hominid samples representing A. africanus and Asian H. erectus. Analysis of the modern sample shows that most interspecific variation in vault thickness can be accounted for by variation in body size. Correlation values are moderate to high (r = 0.75-0.98), and all variables exhibit positive allometry. The bone thickness: body mass relationship of modern humans broadly conforms with that of other primates. However, in the distribution of relative thickness throughout the skull, H. sapiens is distinguished by relative thickening of the parietal and extreme relative thinning of the temporal squama. The bone thickness: body mass relationship in the two early hominid species is examined using published mean body weight estimates generated from post-cranial predictor variables. A. africanus exhibits great similarity to modern humans in its relation to the catarrhine regression data and in the distribution of relative thickness throughout the skull. H. erectus also shows a modern human-like pattern in the distribution of its relative thickness; however, its bone thickness: body mass relationship is dissimilar to that displayed by all other taxa, including the other hominid species. On the basis of these results, it is suggested that the published body weight estimate assigned to H. erectus greatly underestimates actual mean body size for Asian members of this species.

Africa↗

PubMed1998

The mixed dentition and associated skull fragments of a juvenile fossil hominid from Sterkfontein, South Africa.

In April-May 1983, the late A.R. Hughes and his field team recovered more than 40 bone fragments and teeth from a single solution pocket of the Sterkfontein Formation. After preparation and reconstruction by JMC, it was recognised that these fragments represent a single juvenile individual (Stw 151), consisting of more than 40 cranial and dental parts, with mixed dentition. It constitutes the most complete set of jaws and teeth of an early hominid child since the Taung child was recovered in 1924. In this paper, the morphological and metrical features of the individual teeth are described. The other associated skull fragments (right ramus of the mandible, left petrous bone, right glenoid region) are also described. Comparisons are made with other South (and East) African fossil hominids. The beautiful preservation simultaneously of most of the deciduous teeth and of the permanent teeth exposed in their crypts allows an accurate analysis of the developmental sequence. A report on the dental developmental status of this juvenile is presented. On the basis of the microanatomical study of the developing permanent teeth, the estimated age at death is 5.2-5.3 years. Reconstructions of the maxillary and mandibular arcades are also offered. The morphological and metrical features of Stw 151 raise the possibility that it may represent a hominid more derived towards an early Homo condition than the rest of the A. africanus sample from Member 4.

Animals↗

PubMed1999

Testing for multiple species in fossil samples: an evaluation and comparison of tests for equal relative variation.

Tests for equal relative variation are valuable and frequently used tools for evaluating hypotheses about taxonomic heterogeneity in fossil hominids. In this study, Monte Carlo methods and simulated data are used to evaluate and compare 11 tests for equal relative variation. The tests evaluated include CV-based parametric bootstrap tests, modifications of Levene's test, and modified weighted scores tests. The results of these simulations show that a modified version of the weighted scores test developed by Fligner and Killeen ([1976] J. Am. Stat. Assoc. 71:210-213) is the only test that maintains an acceptable balance of type I and type II errors, even under conditions where all other tests have extraordinarily high type I error rates or little power.

Animals↗

PubMed1999

Estimating sexual dimorphism and size differences in the fossil record: a test of methods.

Investigations of size variation in fossil and archaeological skeletal assemblages may be complicated by incomplete skeletons, biased representation of sexes, and the lack of morphological features that identify sex. In order to refine our ability to evaluate size variation, we test the accuracy of three methods that are currently used to estimate size differences in unsexed (pooled) samples: the means method, the median method, and a newly applied technique, the method of moments. Using body mass data from 42 primate species, we calculated actual levels of sexual dimorphism for each species and compared these values to estimates produced by each method. Multivariate regression was used to examine the effects of sample distribution characteristics, including sample size, kurtosis, skewness, sample variance, sex ratio, and intrasexual variance on the performance of the methods. None of the methods appears to be especially accurate. However, one of the simplest methods, the means method, performs relatively well. Factors that lead to inaccuracies in estimation are not readily evident based on multiple regression analysis. We urge caution in the utilization of these techniques, and advocate further analysis of simulated data. Am J Phys Anthropol 110: 95-104, 1999.

Animals↗