Endocranial shape changes during growth in chimpanzees and humans: A morphometric analysis of unique and shared aspects

Compared to our closest living and extinct relatives, humans have a large, specialized, and complex brain embedded in a uniquely shaped braincase. Here, we quantitatively compare endocranial shape changes during ontogeny in humans and chimpanzees. Identifying shared and unique aspects in developmental patterns of these two species can help us to understand brain evolution in the hominin lineage.Using CT scans of 58 humans and 60 chimpanzees varying in age from birth to adulthood, we generated virtual endocasts to measure and analyze 29 three-dimensional endocranial landmarks and several hundred semilandmarks on curves and the endocranial surface; these data were then analyzed using geometric morphometric methods.The ontogenetic shape trajectories are nonlinear for both species, which indicates several developmental phases. Endocranial shape is already distinct at birth and there is no overlap between the two species throughout ontogeny. While some aspects of the pattern of endocranial shape change are shared between humans and chimpanzees, the shape trajectories differ substantially directly after birth until the eruption of the deciduous dentition: in humans but not in chimpanzees, the parietal and cerebellar regions expand relatively (contributing to neurocranial globularity) and the cranial base flexes within the first postnatal year when brain growth rates are high. We show that the shape changes associated with this early “globularization phase” are unique to humans and do not occur in chimpanzees before or after birth.     

Principles for the virtual reconstruction of hominin crania

Fossils are usually discovered broken or distorted, therefore reconstruction is inevitably the first step towards any comparative analysis. We outline a general methodological framework by which missing information about biological specimens can be estimated using geometric morphometric methods and discuss how this relates to effective paleoanthropological use of incomplete and distorted crania.Combining digital data resources with geometric morphometrics, we go beyond the assembly of fragments on the computer. As in a three-dimensional jigsaw puzzle, we first assemble the virtual pieces manually. Then we use landmarks, several hundred semilandmarks, and information from complete specimens to estimate missing coordinates and correct for distortion simultaneously. One can thus incorporate information from incomplete specimens in a comparative morphometric analysis while keeping track of the uncertainties that result from partial preservation or deformation. We exemplify our approach by reconstructing the fossil crania Arago XXI, Taung, and KNM-WT 15000. As different assumptions and algorithms lead to different estimations, there exists no “all-purpose” reconstruction. Instead one creates multiple reconstructions—a posterior distribution in a Bayesian sense. This distribution reflects uncertainty due to missing data values and sensitivity to prior assumptions. While there will typically be shape differences among equally plausible reconstructions, these different estimates might still support a single conclusion.     

Evidence for a dual pattern of cranial venous sinuses on the endocranial cast of Taung (Australopithecus africanus)

According to published accounts, an enlarged occipital-marginal sinus system is absent in Australopithecus africanus, although it occurs in high frequencies in A. robustus, A. Boisei, and Hadar hominids commonly designated A. afarensis. In this report, we describe, for the first time, an enlarged occipital-marginal sinus system on the endocranial cast of the Taung specimen, which is part of the holotype of A. africanus. In addition, well-developed right transverse and sigmoid sinuses are represented on the Taung endocast. The various components of the dual venous sinus system on the Taung endocast are measured, and the system is compared to those of other fossil hominids. The compresence of a lateral sinus system and enlarged occipital and marginal sinuses occurs in two Hadar specimens, 2 specimens of A. robustus crassidens, 1 A. boisei specimen, and several early H. sapiens crania. Hence, the presence of strong transverse sinus impressions in a fragmentary specimen may not be interpreted as an indication that an enlarged occipital-marginal sinus system was not present in the original specimen. Conversely, lack of transverse sinus grooves in a fragmentary specimen does provide indirect evidence than an enlarged occipital-marginal system would probably have been present in the whole specimen, as in 2 specimens of A. boisei. Including Taung, enlarged occipital and marginal sinuses occur in 1 out of 5, or 20%, of A. africanus specimens. This figure compares well with the range of mean frequencies in modern human cranial series (1.5 to 28%), but is much lower than are the frequencies for A. boisei, A. robustus, and the Hadar hominids.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evolutionary pattern of the regulatory network for flower development:Insights gained from a comparison of two Arabidopsis species

Previous studies on Arabidopsis thaliana and other model plants have indicated that the development of a flower is controlled by a regulatory network composed of genes and the interactions among them.Studies on the evolution of this network will therefore help understand the genetic basis that underlies flower evolution.In this study,by reviewing the most recent published work,we added 31 genes into the previously proposed regulatory network for flower development.Thus,the number of genes reached 60.We then compared the composition,structure,and evolutionary rate of these genes between A.thaliana and one of its allies,A.lyrata.We found that two genes (FLC and MAF2) show 1∶ 2 and 2∶ 2 relationships between the two species,suggesting that they have experienced independent,post-speciation duplications.Of the remaining 58 genes,35 (60.3％) have diverged in exon-intron structure and,consequently,code for proteins with different sequence features and functions.Molecular evolutionary analyses further revealed that,although most floral genes have evolved under strong purifying selection,some have evolved under relaxed or changed constraints,as evidenced by the elevation of nonsynonymous substitution rates and/or the presence of positively selected sites.Taken together,these results suggest that the regulatory network for flower development has evolved rather rapidly,with changes in the composition,structure,and functional constraint of genes,as well as the interactions among them,being the most important contributors.     

A new Middle Miocene tarsier from Thailand and the reconstruction of its orbital morphology using a geometric-morphometric method

Tarsius is an extant genus of primates endemic to the islands of Southeast Asia that is characterized by enormously enlarged orbits reflecting its nocturnal activity pattern. Tarsiers play a pivotal role in reconstructing primate phylogeny, because they appear to comprise, along with Anthropoidea, one of only two extant haplorhine clades. Their fossils are extremely rare. Here, we describe a new species of Tarsius from the Middle Miocene of Thailand. We reconstructed aspects of its orbital morphology using a geometric-morphometric method. The result shows that the new species of Tarsius had a very large orbit (falling within the range of variation of modern Tarsius) with a high degree of frontation and a low degree of convergence. Its relatively divergent lower premolar roots suggest a longer mesial tooth row and therefore a longer muzzle than in extant species. The new species documents a previous unknown Miocene group of Tarsius, indicating greater taxonomic diversity and morphological complexity during tarsier evolution. The current restriction of tarsiers to offshore islands in Southeast Asia appears to be a relatively recent phenomenon.     

A comparison of the nariokotome Homo erectus with juveniles from a modern human population.

The Nariokotome Homo erectus has an apparent disjunction of inferred age as judged by dental maturity, by epiphyseal closure and by stature, when compared to modern human norms. On this basis, it has been suggested that this fossil hominin differed in its pattern of growth and development from modern humans. In particular, the characteristic human adolescent growth spurt may not yet have been present, and in this sense H. erectus growth would be more ape-like than human-like. This study tests this conclusion by examining the variation in age as inferred from the maturity indicators in a modern human skeletal population of known age. The results show that all of the maturity indicators used in this analysis underage the test skeletons. Furthermore, there is also no consistency between the indicators; they do not agree in their inferred chronological ages. The disjunction between the maturity indicators in the test skeletons is similar in pattern to the disjunction observed in the Nariokotome Homo erectus. This is particularly true of the relationship between dental age and the other two indicators. These results suggest that the pattern observed in Nariokotome is within the normal range of variation found in modern humans. It does not necessarily indicate a different pattern of growth and development.     

Sexual dimorphism in the human bony pelvis, with a consideration of the Neandertal pelvis from Kebara Cave, Israel.

Sexual dimorphism of the human pelvis is inferentially related to obstetrics. However, researchers disagree in the identification and obstetric significance of pelvic dimorphisms. This study addresses three issues. First, common patterns in dimorphism are identified by analysis of pelvimetrics from six independent samples (Whites and Blacks of known sex and four Amerindian samples of unknown sex). Second, an hypothesis is tested that the index of pelvic dimorphism (female mean x 100/male mean) is inversely related to pelvic variability. Third, the pelvic dimensions of the Neandertal male from Kebara cave, Israel are compared with those of the males in this study. The results show that the pelvic inlet is the plane of least dimorphism in humans. The reason that reports often differ in the identification of dimorphisms for this pelvic plane is that both the length of the pubis and the shape of the inlet are related to nutrition. The dimensions of the pelvis that are most dimorphic (that is, female larger than male) are the measures of posterior space, angulation of sacrum, biischial breadth, and subpubic angle. Interestingly, these dimensions are also the most variable. The hypothesis that variability and dimorphism are inversely related fails to be supported. The factors that influence pelvic variability are discussed. The Kebara 2 pelvis has a spacious inlet and a confined outlet relative to modern males, though the circumferences of both planes in the Neandertal are within the range of variation of modern males. The inference is that outlet circumference in Neandertal females is also small in size, but within the range of variation of modern females. Arguments that Neandertal newborns were larger in size than those of modern humans necessarily imply that birth was more difficult in Neandertals.     

A new species of Carpolestes (Mammalia,Plesiadapoidea) from the late Paleocene of southern Wyoming: assessing changes in size and shape during the evolution of a key anatomical feature

A new and phylogenetically basal species of Carpolestes, the youngest and most derived genus of the plesiadapoid family Carpolestidae in North America, is described from a late Tiffanian (Ti-5) site in Sweetwater County, Wyoming, USA. Carpolestids differ from closely related plesiadapoid clades in having an enlarged, multicuspidate, blade-like P₄ that is partly convergent on that of multituberculates and other mammals showing plagiaulacoid dental adaptations. With some notable exceptions, the evolutionary history of North American carpolestids is characterized by the progressive development of larger and more elaborate P₄ blades through time. In particular, species of the monophyletic genus Carpolestes differ from species assigned to the earlier and apparently paraphyletic genus Carpodaptes in terms of both the size and shape of their P₄. A geometric morphometric analysis reveals that, with respect to P₄ shape, the closest approximation to the highly derived morphology of Carpolestes is made by Carpodaptes hobackensis, which is one of the smallest known species of Carpodaptes. In contrast, the largest known species of Carpodaptes, Carpodaptes jepseni, has a P₄ that falls within the metric range of variation for species of Carpolestes, yet Carpodaptes jepseni shows a uniquely derived P₄ shape that seems to exclude it from any special phylogenetic relationship with Carpolestes. A phylogenetic analysis based on dental characters reconstructs Carpodaptes hobackensis as the sister group of the Carpolestes clade. Shape seems to have been a more important factor than size during the final transformation of the blade-like P₄ of North American carpolestids.

http://zoobank.org/urn:lsid:zoobank.org:pub:212F9ECC-DA9A-44F8-BE7E-43F3EBAD636A     

Insights into the evolution of heliozoa (Protozoa, Sarcodina) as provided by ultrastructural studies on a new species of flagellate from the genus Pteridomonas

The fine structure of Pteridomonas danica , a new species of helioflagellate (protozoa), is described. The organism has a single apical flagellum which bears two rows of tripartite tubular hairs. There are two kinetosomes which are bound to each other and to the surface of the single nucleus by amorphous electron-dense material. The flagellum is surrounded by a wreath of fine arms, which are supported internally by triads of microtubules. The triads terminate on the nucleus. The mitochondria have tubular cristae which contain wisps of intracristal material. The dictyosomes are located in the posterior part of the cell, being clustered around the internal element of the contractile stalk. Extrusomes are present. Pteridomonas has substantial similarities with the colourless flagellate Ciliophrys and with the pedinellid algal flagellates. As Ciliophrys resembles the actinophryid heliozoa in several important respects, the evidence supports the contention that these heliozoa have a common ancestry with the heterokont algae and have evolved along a line involving the pedinellids and some colourless helioflagellates. If the perceived relationships are to be reflected in their taxonomy, then a substantial reclassification of these organisms is required.     

The land fauna of Ascension Island: new data from caves and lava flows,and a reconstruction of the prehistoric ecosystem

Abstract. Terrestrial arthropods were investigated in 1990 and 1995 on Ascension, a young and extremely isolated volcanic island in the equatorial Atlantic. Three new genera (of Araneae, Oribatida and Psocoptera) were discovered and the number of apparently endemic species was increased from fourteen to about twenty-nine. Some 311 species of land animals (a few now extinct) are known to have established themselves on the island; in a few groups there may be significant numbers of unrecorded species. About ninety-five endemic and non-endemic species are considered to be native (including two marine turtles, twelve seabirds and two extinct landbirds); seventy-eight are of doubtful status; and at least 138 were probably introduced by humans. Natural colonists arrived mainly by air (drifting with the wind during migratory movements) but some evidently travelled on floating objects or attached to birds or other animals. Natural colonization was almost entirely from Africa. Before the arrival of humans, Ascension had an early successional ecosystem. The fauna in the lava and cinder deserts of the lowlands—both on the surface and in subterranean cracks and caves—was dominated by taxonomically varied scavengers and mainly arachnid predators. The scattered angiosperms here and in the foothills supported some host-specific herbivores with associated predators; they were also exploited (especially after exceptional rains) by a number of Orthoptera, Hemiptera and Lepidoptera derived from migratory African populations and perhaps reinforced at intervals by additional groups of colonists. The more extensive and largely cryptogamic vegetation on the central peak had a poor fauna probably composed mainly of micro-arthropods. Along coasts, on islets and in the extensive seabird colonies there were additional arthropod species and also a flightless rail and a night heron (both now extinct). Invertebrate stocks that colonized Ascension underwent a variety of evolutionary changes including phyletic evolution leading to endemic status, adaptation to subterranean life (Araneae, Pseudoscorpiones, Collembola and Psocoptera), character release (phorid Diptera), and probably splitting of lineages (speciation) within the island (Isopoda, Collembola and gryllid Orthoptera). The relatively high diversity of Pseudoscorpiones (five species in five genera) and their 100% apparent endemicity is notable. The indigenous fauna of Ascension provides a view of an early stage in the processes of colonization, adaptive evolution and radiation which—over much longer periods—give rise to the richer and more distinctive faunas of older oceanic islands such as Ascension's nearest neighbour, St Helena, where a few invertebrate clades have undergone repetitive speciation and some adaptive radiation.     

Cardamine apennina: a new endemic diploid species of the C. pratensis group (Brassicaceae) from Italy

Italian representatives of the Cardamine pratensis group were investigated using morphometric, karyological, and molecular (AFLP-fingerprinting) analyses. Focus was on resolving the taxonomic and evolutionary position of C. granulosa from Piemonte (NW Italy) and of populations from central Italy, previously included in C. granulosa or C. pratensis s. str. Results show that C. granulosa is a morphologically and genetically well defined diploid species, but is extremely rare and restricted to a small area in Piemonte. Central Italian populations differ from both C. granulosa and C. pratensis s. str., and, although the morphological differentiation is not strongly pronounced, they show marked molecular divergence, suggesting recognition as a new species, Cardamine apennina. Because of their restricted distribution and diploid chromosomal level, C. apennina and C. granulosa may represent basal and quite isolated lineages, whereas reticulation on diploid and polyploid level has affected remaining lineages of the C. pratensis group. Both Italian endemics are endangered due to rarity and habitat loss. A key for identification of the Italian taxa of the C. pratensis group is also provided.     

Ostreol A: A new cytotoxic compound isolated from the epiphytic dinoflagellate Ostreopsis cf. ovata from the coastal waters of Jeju Island,Korea

Ostreol A was isolated from cultures of the epiphytic dinoflagellate Ostreopsis cf. ovata from the coastal waters of Jeju Island, Korea. The compound, a non-palytoxin derivative, has a polyhydroxy chain ending with the primary amino group and contains an amide bond, along with two tetrahydropyran rings in the chain. Its chemical structure was elucidated by nuclear magnetic resonance (NMR) spectroscopy methods and confirmed by mass analysis. The compound exhibited significant cytotoxicity in the brine shrimp lethality test at a concentration of 0.9 μg/mL.     

Toward a modern synthesis of immunity: Charles A. Janeway Jr. and the immunologist's dirty little secret

This essay chronicles the major theoretical and experimental contributions made by Charles A. Janeway, Jr. (1943-2003), Howard Hughes Medical Institute investigator and Yale Professor of Immunobiology, who established the fundamental role of the innate immune system in the induction of the adaptive arm.     

A new gymnosperm <Emphasis Type="Italic">Sylvocarpus armatus</Emphasis> gen. et sp. nov. from the Lower Permian of the Ural Mountains

A Permian gymnosperm is described as a new genus and new species, Sylvocarpus armatus gen. et sp. nov., on the basis of half-closed seed-bearing capsules. The new plant is assigned to the Angaropeltidaceae, a family related to the Peltaspermales and Caytoniales.     

A new Papulaspora species from the infected eye of a horse: Papulaspora equi sp. nov.

An unusual fungus, probably traumatically introduced into the eye of a horse while grazing, was studied on various mycological media. Upon examination of colonies the organism produced bulbils and clearly exhibited the characteristics of a new species of Papulaspora, P. equi Shadomy & Dixon.     

Leaf evolution in early-diverging ferns: insights from a new fern-like plant from the Late Devonian of China

Background and Aims With the exception of angiosperms, the main euphyllophyte lineages (i.e. ferns sensu lato, progymnosperms and gymnosperms) had evolved laminate leaves by the Late Devonian. The evolution of laminate leaves, however, remains unclear for early-diverging ferns, largely represented by fern-like plants. This study presents a novel fern-like taxon with pinnules, which provides new insights into the early evolution of laminate leaves in early-diverging ferns.Methods Macrofossil specimens were collected from the Upper Devonian (Famennian) Wutong Formation of Anhui and Jiangsu Provinces, South China. A standard degagement technique was employed to uncover compressed plant portions within the rock matrix.Key Results A new fern-like taxon, Shougangia bella gen. et sp. nov., is described and represents an early-diverging fern with highly derived features. It has a partially creeping stem with adventitious roots only on one side, upright primary and secondary branches arranged in helices, tertiary branches borne alternately or (sub)oppositely, laminate and usually lobed leaves with divergent veins, and complex fertile organs terminating tertiary branches and possessing multiple divisions and numerous terminal sporangia.Conclusions Shougangia bella provides unequivocal fossil evidence for laminate leaves in early-diverging ferns. It suggests that fern-like plants, along with other euphyllophyte lineages, had independently evolved megaphylls by the Late Devonian, possibly in response to a significant decline in atmospheric CO₂ concentration. Among fern-like plants, planate ultimate appendages are homologous with laminate pinnules, and in the evolution of megaphylls, fertile organs tend to become complex.     

A novel toxin from the venom of the scorpion Tityus trivittatus, is the first member of a new alpha-KTX subfamily

The first example of a new sub-family of toxins (alpha-KTx20.1) from the scorpion Tityus trivittatus was purified, sequenced and characterized physiologically. It has 29 amino acid residues, three disulfide bridges assumed to adopt the cysteine-stabilized alpha/beta scaffold with a pI value of 8.98. The sequence identities with all the other known alpha-KTx are less than 40%. Its effects were verified using seven different cloned K(+) channels (vertebrate Kv1.1-1.5, Shaker IR and hERG) expressed in Xenopus leavis oocytes. The toxin-induced effects show large differences among the different K(+) channels and a preference towards Kv1.3 (EC50=7.9+/-1.4 nM).     

A new species of Paramunida Baba, 1988 from the Central Pacific Ocean and a new genus to accommodate P. granulata (Henderson, 1885)

The genus Paramunida belongs to the most diverse family of galatheoids and it is commonly reported from the continental slope across the Indian and Pacific Oceans. Examination of material collected by the NOAA RV Townsend Cromwell Cruise near Christmas (Kiritimati) Island, Kiribati, revealed the existence of a new species of Paramunida (P. haigae), which represents the fourth record of the genus for the Central Pacific. Furthermore, recent efforts to unravel phylogenetic relationships and diversification patterns in Paramunida revealed P. granulata (Henderson, 1885) to be the most basally diverging taxon within the genus. This species is clearly distinguished from other species of Paramunida by the spinulation of the carapace and the length of the distomesial spine of the second antennal peduncle article, which in combination with a high level of genetic divergence suggest that this species represents a separate monotypic lineage. A new genus, Hendersonida gen. n., is proposed to accommodate this species based on morphological and molecular evidence. An updated dichotomous identification key for all species of Paramunida is presented.