Craniodental variation in Paranthropus boisei: a developmental and functional perspective

What levels and patterns of craniodental variation among a fossil hypodigm are necessary to reject the null hypothesis that only a single species is sampled? We suggest how developmental and functional criteria can be used to predict where in the skeleton of fossil hominins we should expect more, or less, within-species variation. We present and test three hypotheses about the factors contributing to craniodental variation in extant primate taxa, and then apply these results to the interpretation of the P. boisei hypodigm. Within the comparative samples of extant Homo, Pan, Gorilla, Pongo, and Colobus, variables from the cranial base, neurocranium, and face that are not subject to high magnitudes of strain have consistently lower levels of intraspecific variation than variables from regions of the face subject to high levels of strain. Dental size variables are intermediate in terms of their reliability. P. boisei is found to have a low degree of variability relative to extant primates for variables shown to be generally useful for testing taxonomic hypotheses. Contrary to the claims of Suwa et al. ([1997] Nature 389:489-492), the recently discovered material from Konso falls within the range of variation of the "pre-Konso" hypodigm of P. boisei for available conventional metrical variables. Those aspects of the Konso material that appear to extend the range of the P. boisei hypodigm involve regions of the skull predicted to be prone to high levels of within-species variation. The approach used in this study focuses on craniodental data, but it is applicable to other regions of the skeleton.     

Temporal changes to spatially stratified waterbird communities of the Coorong, South Australia: implications for the management of heterogenous wetlands

The Coorong, South Australia, is a globally significant wetland system, listed in the Ramsar Convention under a number of different criteria, including its importance to waterbird populations. Based on annual waterbird censuses conducted between 2000 and 2007, spatiotemporal analyses revealed that significant differences in waterbird community structure exist along the length of the Coorong. This spatial diversity in community structure was also found to be temporally consistent over this 8-year period. The abundance of the most numerically dominant bird species, such as red-necked stint Calidris ruficollis and grey teal Anas gracilis , explained much of this spatial variation. However, comparisons between data collected for the Coorong south lagoon in 1985 and 2000–2007 show that dramatic changes in these waterbird communities have occurred over longer periods of time, with 23 of the 27 most common species having declined in this period by at least 30%. The Coorong still regularly supports globally important populations (>1% of global population) of nine waterbird taxa, including three Palearctic shorebirds, confirming its Ramsar status. The functional links between the overutilized Murray-Darling basin river system and the Coorong are discussed.     

A new hominin from the Basal Member of the Hadar Formation, Dikika, Ethiopia, and its geological context

In this paper we report for the first time hominin remains from the Basal Member of the Hadar Formation at Dikika, in the Awash Valley of Ethiopia, dating to greater than 3.4 Ma. The new fossil, DIK-2-1, is a fragment of a left mandible and associated dentition. The mandible is attributed to Australopithecus afarensis. However, the new fossil exhibits some metric and morphological features that have not previously been seen in the A. afarensis hypodigm, increasing the already impressive degree of variation in the mandibular sample of the species.     

Assessing the use of the mitochondrial cox1 marker for use in DNA barcoding of red algae (Rhodophyta)

The red algae, a remarkably diverse group of organisms, are difficult to identify using morphology alone. Following the proposal to use the mitochondrial cytochrome c oxidase subunit I (cox1) for DNA barcoding animals, we assessed the use of this gene in the identification of red algae using 48 samples plus 31 sequences obtained from GenBank. The data set spanned six orders of red algae: the Bangiales, Ceramiales, Corallinales, Gigartinales, Gracilariales and Rhodymeniales. The results indicated that species could be discriminated. Intraspecific variation was between 0 and 4 bp over 539 bp analyzed except in Mastocarpus stellatus (0-14 bp) and Gracilaria gracilis (0-11 bp). Cryptic diversity was found in Bangia fuscopurpurea, Corallina officinalis, G. gracilis, M. stellatus, Porphyra leucosticta and P. umbilicalis. Interspecific variation across all taxa was between 28 and 148 bp, except for G. gracilis and M. stellatus. A comparison of cox1 with the plastid Rubisco spacer for Porphyra species revealed that it was a more sensitive marker in revealing incipient speciation and cryptic diversity. The cox1 gene has the potential to be used for DNA barcoding of red algae, although a good taxonomic foundation coupled with extensive sampling of taxa is essential for the development of an effective identification system.     

Cyclopygid Trilobites from the Ordovician Builth-Llandrindod Inlier, Central Wales

Cyclopygids are a minor element in the abundant trilobite fauna of the Ordovician Llanfawr Mudstones Formation ( teretiusculus – gracilis biozones) of the Builth-Llandrindod inlier. The rarity of these trilobites may be due to the accumulation of these sediments close to the shoreward limit of their depth range, and if this is the case, their presence, together with sedimentological evidence, can be used to infer the bathymetric limits within which the Llanfawr Mudstones Formation might have been deposited. Species of Degamella , Microparia ( Microparia ), Microparia ( Heterocyclopyge ), Sagavia and Emmrichops are described; some are common to the Dobrotivá Formation in Bohemia, whilst others have affinities with species from approximately coeval strata in Kazakhstan and north-west China.     

The Late Triassic Phytosaur Mystriosuchus Westphali, With A Revision of the Genus

Mystriosuchus westphali is based on a large, well-preserved cranium and a snout fragment from the Stubensandstein (Norian) of south-west Germany. The hypodigm is redescribed and new or poorly known cranial structures in phytosaurs are discussed. For the first time, the presence of a premaxillary crest is substantiated in a phytosaur. The type specimen shows a supernumerary occipital element (='tabular') that is probably fused to the parietal in other phytosaurs, and an orbitosphenoid. A computerised parsimony analysis confirms the hypothesis that Mystriosuchus is nested within Pseudopalatinae, the most derived clade of phytosaurs, and thus does not fall within basal phytosaurs. Mystriosuchus is characterised by five unique features (slit-like interpremaxillary fossa, triangular cross-section of the postorbito-squamosal bar, strongly reduced posttemporal fenestra, and two features of the cranial sculpture), plus eight synapomorphies that also occur in some more distantly related taxa. Mystriosuchus westphali is diagnosed by, among other apomorphies, a distinct premaxillary crest, a squamosal-proo¨tic contact, absence of a posterior process of the squamosal, and a slit-like posttemporal fenestra. The type species Mystriosuchus planirostris shows, most significantly, the naris facing forward anteriorly and upward posteriorly, and the longest rostrum and the highest degree of depression of the supratemporal opening in any phytosaur. Mystriosuchus exemplifies a common pattern in phytosaurids in being a genus that includes a gracile, elongated, slender-snouted and a more robust species with a broader, often crested snout. This study demonstrates that a detailed analysis of the cranial anatomy and the rigorous application of cladistic principles to identified character states help to clarify current inconsistencies in the taxonomy and nomenclature of phytosaurs.     

Evolutionary implications of the distribution and variation of the skeletal muscles of the anuran lymphatic system

Lymphatic return to the circulation in anurans is dependent upon the interaction of a number of skeletal muscles and lung deflation. We define character states and describe variation of these putative lymphatic skeletal muscles: the M. cutaneus pectoris (CP), M. cutaneus dorsi (CD), M. piriformis (P), M. sphincter ani cloacalis (SAC), and the complex of the M. gracilis minor/M. abdominal crenator (GM/AC). We include examination of over 400 specimens of 377 species belonging to 40 of the 42 currently recognized anuran families. Some muscles show limited variation (P) or are clearly linked to phylogeny (CP; CD) and thus have limited value in the determination of form and function. However, the GM/AC and SAC show a high degree of structural variation that appears in taxa across the phylogenetic spectrum. This allows us to make phylogenetically independent determinations of form and function. We define an ancestral state of the GM and conclude that evolution of the GM/AC and SAC has progressed in two directions from this ancestral state: toward either elaboration or reduction. Where present, the character states of both of these muscle groups were observed in all species examined and the number of states correlated within each family as well. The degree of development of the GM/AC and SAC compliance pump system is strongly correlated with previously determined lymph flux rates in a three species test. Our data suggest there may be a relationship between greater elaboration of the GM/AC and SAC system and terrestriality among the Anura.     

Phylogenetic diversity of cellular organization in the cardia of muscoid flies (Diptera: Schizophora)

In each of 30 dipteran species, representing 13 acalyptrate and 7 calyptrate families, the cardia is formed from specialized cells at the junction between foregut and midgut. Foregut epithelium forms the stomodeal valve; midgut epithelium envelops the valve to form the cardia's outer wall. Cytological characteristics within these epithelia differ from region to region and from species to species. Since the cardia secretes the peritrophic membrane, cardias with diverse patterns of cellular differentiation may be expected to produce peritrophic membranes with similarly diverse properties. Close relatives often share more details of cardia structure than do distantly related taxa. Within the monophyletic Calyptratae, a common pattern of cellular differentiation includes three distinct zones of columnar midgut cells enclosing a flanged stomodeal valve. Among species in the paraphyletic Acalyptratae, midgut typically includes a single zone of tall columnar cells, while the valve may be spheroidal, cylindrical, conical, or flanged. The correlation of phylogenetic distance with divergence in cardia organization implies a strong influence of ancestry upon current structure, regardless of current diet. However, at least some of the observed diversity in cardia structure is associated with dietary divergence. Calyptrate flies with derived blood-feeding behavior display cellular differentiation that is simplified from that seen in calyptrate relatives with less specialized feeding habits. This evolutionary modification suggests that cardia organization and hence peritrophic membrane structure can adapt to dietary changes, with possible significance for the spatial organization of digestive processes and interactions with ingested microorganisms.     

Turtle remains from the Middle Jurassic Xintiangou Formation of Yunyang,Sichuan Basin,China

Three turtle shells from the Middle Jurassic Xintiangou Formation of Yunyang (Chongqing, China) are described and assigned to Xinjiangchelyidae (Testudines: Eucryptodira). This is the first report of turtle remains from the Xintiangou Formation, Sichuan Basin and represents the oldest known Xinjiangchelyidae. The assemblage includes two taxa, Protoxinjiangchelys sp. and Xinjiangchelyidae indet. This discovery extends the stratigraphical distribution of Xinjiangchelyidae and improves our knowledge about the early evolution of that family. It demonstrates that by the Middle Jurassic, at the time of deposition of the Xintiangou Formation, the group was already diversified in the Sichuan Basin.     

高于庄古生物学(英)

距今 14～ 16亿年的华北地区高于庄组黑色层状、结核状和透镜状燧石与叠层石的黑色硅质部分中保存着极丰富的原核和真核生物微化石。宏观藻类在该组的页岩中亦已发现。本组为评估中元古代生命状况、古环境和前显生宙生物地层提供了重要的生物信息。迄今为止在高于庄组地层中已有百余个化石种被人们认识。根据古植物和古环境的特征这些生物种类可分为三个不同的组合 ,即 :1.颤藻和色球藻组合 ,出现在高于庄组一段 ,代表浅水藻席建造者和居住者与一些可能的外来浮游生物的种类 ;2 .念珠藻组合 ,仅发生在该组的二段 ,还含一些底栖藻席建造者或居住者的种类 ;3.第四段的色球藻组合 ,它代表了潮间带至亚潮带的藻席建造者和外来的种类。元古代燧石中的微化石 ,尤其是蓝藻化石 ,尽管在元古代它们就已不断趋向于多样化 ,但由于它们形态上的保守性 ,对环境的指示比对地质时代的指示更有价值。高于庄组微化石的特点和大多数链状念珠藻垂直层理保存的事实表明 :1.高于庄组微化石的个体大小随时间趋向于增大 ;2 .高于庄组的沉积可能是处于一个淡水环境 ,且沉积率可能等于或少于微生物的生长率 ;3.高于庄组织沉积模式可能是从潮间带至亚潮带或深海 ,然后再至潮间带或潮上带 ;4 .当高于庄组沉积时真核生物亦已出现。     

粤西云开地区中奥陶世翼形类(双壳类)一新超科——郁南蛤超科 Yunannioidea superfam.nov.

本研究记述粤西云开地区中奥陶统东冲组一种奇异的翼形类(双壳类)化石,建立了郁南蛤超科(新超科)Yunannioidea superfam.nov.,郁南蛤科(新科)Yunanniidae fam.nov.,郁南蛤属(新属)Yunannia gen.nov.及2新种:干坑郁南蛤(新属新种)Yunannia gankeng...     

Fossil vertebrate faunas of the British Rhaetian (latest Triassic)

Rhaetian fossil vertebrate faunas of Britain represent rich but biased samples of taxonomic diversity during uppermost Triassic time. Review of the Westbury Formation, Penarth Group, in particular, reveals a combination of marine, littoral, and terrestrial elements. Minimally, six species of shark are preserved along with a myriacanthid holocephalan, at least four actinopterygian taxa, a characteristic lungfish, ichthyosaurs, plesiosaurs, dinosaurs, and potentially the earliest representative of the Choristodera. Rare mammalian occurrences in the Westbury beds are also possible. Severnichthys gen. nov. is a large osteichthyan, probably a palaeonisciform chondrostean, which historically has been mistaken for a labyrinthodont amphibian. At least two additional actinopterygian species and a holocephalan are known from die Lilstock Formation, and a mammal or mammallike reptile is recorded from the uppermost Blue Anchor Formation. Analysis of element abundance in the disarticulated Westbury Formation assemblage indicates that many parts of some taxa are never preserved while other elements of the same form are common. Such preservational bias suggests that many species may be missing entirely from this long-studied but poorly understood taphocoenosis. Possibly contemporaneous cave faunas from nearby upland areas give a similarly biased picture of the terrestrial fauna during this time of widespread marine transgression.     

Length Variation in Mitochondrial DNA of the Minnow Cyprinella Spiloptera

Length differences in animal mitochondrial DNA (mtDNA) are common, frequently due to variation in copy number of direct tandem duplications. While such duplications appear to form without great difficulty in some taxonomic groups, they appear to be relatively short-lived, as typical duplication products are geographically restricted within species and infrequently shared among species. To better understand such length variation, we have studied a tandem and direct duplication of approximately 260 bp in the control region of the cyprinid fish, Cyprinella spiloptera. Restriction site analysis of 38 individuals was used to characterize population structure and the distribution of variation in repeat copy number. This revealed two length variants, including individuals with two or three copies of the repeat, and little geographic structure among populations. No standard length (single copy) genomes were found and heteroplasmy, a common feature of length variation in other taxa, was absent. Nucleotide sequence of tandem duplications and flanking regions localized duplication junctions in the phenylalanine tRNA and near the origin of replication. The locations of these junctions and the stability of folded repeat copies support the hypothesized importance of secondary structures in models of duplication formation.     

Phylogeography and host race differentiation in the European mistletoe (Viscum album L.)

Mistletoes are bird dispersed, hemi-parasitic shrubs infecting a large number of woody host plants. Chloroplast fragment length polymorphisms were used to study genetic differentiation among presumed host races, population genetic structure, and to elucidate the postglacial migration history of mistletoe ( Viscum album ) across the entire natural distribution range in Europe. The populations sampled belong to four closely related taxa, three of which are widely distributed and differ in their host trees, whereas a fourth taxon is rare and endemic to the Island of Crete. The molecular analysis of chloroplast DNA variation supported the distinction of these four taxa. We further found evidence for phylogeographical structure in each of the three widely distributed host races. Independent of host race, mistletoe haplotypes from Turkey were distinct and distant from those found elsewhere in Europe, suggesting that highly differentiated populations, and possibly new taxa, exist at the range limit of the species.     

Hypothetical way of pollen aperture patterning. 2. Formation of polycolpate patterns and pseudoaperture geometry

Deviant forms of polycolpate pollen, differing from the typical pattern in the number and arrangement of apertures, are found to be similar in distantly related dicotyledon taxa. The range of variation of common and deviant aperture patterns may be arranged as a continuous series, which may be described as a gradual and geometrically regular transformation of the deviant form with a meridional circular colpus to one of the common polycolpate conditions. Similar series have been observed in the taxa with colporate and pseudocolpate pollen. All possible spatial isomers and their mirror symmetrical variants of the deviant polycolpate and polypseudocolpate pollen have been predicted in terms of the suggested regularities of aperture multiplication. Some of them have been identified in the samples studied.     

高于庄古生物学

距今14～16亿年的华北地区高于庄组黑色层状、结核状和透镜状燧石与叠层石的黑色硅质部分中保存着极丰富的原核和真核生物微化石.宏观藻类在该组的页岩中亦已发现.本组为评估中元古代生命状况、古环境和前显生宙生物地层提供了重要的生物信息.迄今为止在高于庄组地层中已有百余个化石种被人们认识.根据古植物和古环境的特征这些生物种类可分为三个不同的组合,即:1.颤藻和色球藻组合,出现在高于庄组一段,代表浅水藻席建造者和居住者与一些可能的外来浮游生物的种类;2.念珠藻组合,仅发生在该组的二段,还含一些底栖藻席建造者或居住者的种类;3.第四段的色球藻组合,它代表了潮间带至亚潮带的藻席建造者和外来的种类.元古代燧石中的微化石,尤其是蓝藻化石,尽管在元古代它们就已不断趋向于多样化,但由于它们形态上的保守性,对环境的指示比对地质时代的指示更有价值.高于庄组微化石的特点和大多数链状念珠藻垂直层理保存的事实表明:1.高于庄组微化石的个体大小随时间趋向于增大;2.高于庄组的沉积可能是处于一个淡水环境,且沉积率可能等于或少于微生物的生长率;3. 高于庄组织沉积模式可能是从潮间带至亚潮带或深海,然后再至潮间带或潮上带;4.当高于庄组沉积时真核生物亦已出现.     

Testing the taxonomic integrity of Paranthropus boisei sensu stricto

The craniodental hypodigm of Paranthropus boisei sensu stricto is morphologically distinctive, but it has been suggested that the substantial variation in mandibular and dental size in that hypodigm may exceed that which is reasonable to subsume within a single hominin species. In this study, Fligner and Killeen, coefficient of variation (CV)-based and average taxonomic distance (ATD)-based bootstrap tests, were used to compare variation in size and shape of the mandibular corpus remains attributed to P. boisei s.s. with the variation observed in samples of great apes and modern humans. The degree of size variation in the P. boisei s.s. mandibular hypodigm is never observed in human and chimpanzee samples, is rare in gorillas, but is not uncommon in orangutans. However, the shape variation in the fossil group is comparable to the variation in the extant reference groups. Although the size variation in P. boisei s.s. is substantial, it is exaggerated by the effects of taphonomy. The small mandibles are more often abraded, whereas the large mandibles are more likely to have been infiltrated with matrix. On the basis of the results of this investigation of the mandibular corpus, there are no grounds for rejecting the "single-species" hypothesis for P. boisei s.s. When Sokal and Braumann's adjusted CV values were used to predict the index of sexual dimorphism (ISD) for the P. boisei s.s., despite the substantial geological time embraced by the mandibular corpus hypodigm, the predicted value of lnISD, when corrected for taphonomic factors, is comparable to the sexual dimorphism observed within Gorilla.     

North American black-fruited hawthorns. II. Floral development of 10- and 20-stamen morphotypes in Crataegus section Douglasii (Rosaceae: Maloideae)

Crataegus section Douglasii exhibits variation in stamen number per flower typical for the genus throughout North America. To understand the developmental basis for this variation we studied the early floral ontogeny of the three taxa in section Douglasii: C. douglasii (both Pacific northwest and the upper Great Lakes basin), C. rivularis, and C. suksdorfii. Crataegus suksdorfii, like all known diploid Crataegus, has ≈20 stamens; the two other taxa have ≈10 stamens, a condition associated only with polyploidy. In all taxa petal primordia and a whorl of five pairs of stamen primordia develop from five common primordia. The 10-stamen∗∗∗ condition results from loss of two whorls of five stamens that are subsequently formed in C. suksdorfii. Loss of these two whorls in the 10-stamen taxa is the result of neither a smaller floral apex at initiation, nor a smaller flower at anthesis. Stamen number variability, particularly in C. douglasii and C. rivularis, is the result predominantly of fewer than two stamen primordia developing between adjacent petal primordia. Pollen production in C. douglasii is half that in C. suksdorfii because of the reduction in stamen number. The results are presented and discussed in terms of morphogenetic explanations of meristic variation.     

Genetic structure of three orchid species with contrasting breeding systems using RAPD and allozyme markers

Zeuxine gracilis, Zeuxine strateumatica, and Eulophia sinensis are wild orchids with different breeding systems and colonizing abilities. Zeuxine gracilis is an outcrosser with restricted distribution, whereas S. strateumatica is an apomictic colonizer found only in newly available open habitats. Eulophia sinensis is an outcrossing colonizer. This study investigates the levels of genetic variation and patterns of population structure in these wild orchids to provide genetic information for the development of suitable conservation strategies. Lack of allozyme variation was characteristic of all three species, especially in populations of the two colonizing orchids, Z. strateumatica and E. sinensis. More variable markers, randomly amplified polymorphic DNAs (RAPDs), were further employed to characterize population structure of these species. Substantial genetic variation was found at the RAPD loci within populations of Z. gracilis (p = 21.65 ± 15.88%, A = 1.217 ± 0.159, and H = 0.076 ± 0.054) and E. sinensis (p = 17.82 ± 20.97%, A = 1.179 ± 0.209, and H = 0.070 ± 0.084), but little variation existed within populations of Z. strateumatica (p = 2.84 ± 2.58%, A = 1.029 ± 0.026, and H = 0.011 ± 0.011). Regardless of the breeding system, the total gene diversity at the species level was partitioned primarily between populations, as shown by high G(ST) values, in all three species. An extremely high level of population differentiation (G(ST) = 0.924) was found in the apomictic colonizer Z. strateumatica. The patterns of genetic variation in these wild orchids are apparently related to their differences in breeding system and colonizing ability. Different conservation strategies are needed for the long-term survival of these species.     

Polymorphic aspects of male anthropoid canines

Interspecific variation in the architecture of male anthropoid maxillary canines is documented. Extant taxa are polymorphic, and most can be sorted into two major groupings based on quantitative measures of shape, distal edge sharpness, and interspecific changes in their linear dimensions (projection, mesiodistal length, and buccolingual breadth) relative to each other and to body mass (scaling). One group includes the great apes and ceboids; the other includes cercopithecoids and hylobatids. Statistically significant differences between these groups were found for canine shape, for trajectories of regressions for canine projection on canine length and canine breadth, and for canine projection and canine breadth relative to body mass. The data indicate that explantations of canine variation in male anthropoids must include a mechanical interpretation of form in addition to assessments of habitus, heritage, and body mass.