Acquisition Of Characters Research Articles

Archaeopteryx feathers and bone chemistry fully revealed via synchrotron imaging

Evolution of flight in maniraptoran dinosaurs is marked by the acquisition of distinct avian characters, such as feathers, as seen in Archaeopteryx from the Solnhofen limestone. These rare fossils were pivotal in confirming the dinosauria-avian lineage. One of the key derived avian characters is the possession of feathers, details of which were remarkably preserved in the Lagerstätte environment. These structures were previously simply assumed to be impressions; however, a detailed chemical analysis has, until now, never been completed on any Archaeopteryx specimen. Here we present chemical imaging via synchrotron rapid scanning X-ray fluorescence (SRS-XRF) of the Thermopolis Archaeopteryx, which shows that portions of the feathers are not impressions but are in fact remnant body fossil structures, maintaining elemental compositions that are completely different from the embedding geological matrix. Our results indicate phosphorous and sulfur retention in soft tissue as well as trace metal (Zn and Cu) retention in bone. Other previously unknown chemical details of Archaeopteryx are also revealed in this study including: bone chemistry, taphonomy (fossilization process), and curation artifacts. SRS-XRF represents a major advancement in the study of the life chemistry and fossilization processes of Archaeopteryx and other extinct organisms because it is now practical to image the chemistry of large specimens rapidly at concentration levels of parts per million. This technique has wider application to the archaeological, forensic, and biological sciences, enabling the mapping of "unseen" compounds critical to understanding biological structures, modes of preservation, and environmental context.

EREM: Parameter Estimation and Ancestral Reconstruction by Expectation-Maximization Algorithm for a Probabilistic Model of Genomic Binary Characters Evolution

Evolutionary binary characters are features of species or genes, indicating the absence (value zero) or presence (value one) of some property. Examples include eukaryotic gene architecture (the presence or absence of an intron in a particular locus), gene content, and morphological characters. In many studies, the acquisition of such binary characters is assumed to represent a rare evolutionary event, and consequently, their evolution is analyzed using various flavors of parsimony. However, when gain and loss of the character are not rare enough, a probabilistic analysis becomes essential. Here, we present a comprehensive probabilistic model to describe the evolution of binary characters on a bifurcating phylogenetic tree. A fast software tool, EREM, is provided, using maximum likelihood to estimate the parameters of the model and to reconstruct ancestral states (presence and absence in internal nodes) and events (gain and loss events along branches).

The five AhMTP1 zinc transporters undergo different evolutionary fates towards adaptive evolution to zinc tolerance in Arabidopsis halleri.

Gene duplication is a major mechanism facilitating adaptation to changing environments. From recent genomic analyses, the acquisition of zinc hypertolerance and hyperaccumulation characters discriminating Arabidopsis halleri from its zinc sensitive/non-accumulator closest relatives Arabidopsis lyrata and Arabidopsis thaliana was proposed to rely on duplication of genes controlling zinc transport or zinc tolerance. Metal Tolerance Protein 1 (MTP1) is one of these genes. It encodes a Zn2+/H+ antiporter involved in cytoplasmic zinc detoxification and thus in zinc tolerance. MTP1 was proposed to be triplicated in A. halleri, while it is present in single copy in A. thaliana and A. lyrata. Two of the three AhMTP1 paralogues were shown to co-segregate with zinc tolerance in a BC1 progeny from a cross between A. halleri and A. lyrata. In this work, the MTP1 family was characterized at both the genomic and functional levels in A. halleri. Five MTP1 paralogues were found to be present in A. halleri, AhMTP1-A1, -A2, -B, -C, and -D. Interestingly, one of the two newly identified AhMTP1 paralogues was not fixed at least in one A. halleri population. All MTP1s were expressed, but transcript accumulation of the paralogues co-segregating with zinc tolerance in the A. halleri X A. lyrata BC1 progeny was markedly higher than that of the other paralogues. All MTP1s displayed the ability to functionally complement a Saccharomyces cerevisiæ zinc hypersensitive mutant. However, the paralogue showing the least complementation of the yeast mutant phenotype was one of the paralogues co-segregating with zinc tolerance. From our results, the hypothesis that pentaplication of MTP1 could be a major basis of the zinc tolerance character in A. halleri is strongly counter-balanced by the fact that members of the MTP1 family are likely to experience different evolutionary fates, some of which not concurring to increase zinc tolerance.

Arthropod phylogeny: An overview from the perspectives of morphology, molecular data and the fossil record

Monophyly of Arthropoda is emphatically supported from both morphological and molecular perspectives. Recent work finds Onychophora rather than Tardigrada to be the closest relatives of arthropods. The status of tardigrades as panarthropods (rather than cycloneuralians) is contentious from the perspective of phylogenomic data. A grade of Cambrian taxa in the arthropod stem group includes gilled lobopodians, dinocaridids (e.g., anomalocaridids), fuxianhuiids and canadaspidids that inform on character acquisition between Onychophora and the arthropod crown group. A sister group relationship between Crustacea (itself likely paraphyletic) and Hexapoda is retrieved by diverse kinds of molecular data and is well supported by neuroanatomy. This clade, Tetraconata, can be dated to the early Cambrian by crown group-type mandibles. The rival Atelocerata hypothesis (Myriapoda + Hexapoda) has no molecular support. The basal node in the arthropod crown group is embroiled in a controversy over whether myriapods unite with chelicerates (Paradoxopoda or Myriochelata) or with crustaceans and hexapods (Mandibulata). Both groups find some molecular and morphological support, though Mandibulata is presently the stronger morphological hypothesis. Either hypothesis forces an unsampled ghost lineage for Myriapoda from the Cambrian to the mid Silurian.

Positive and Negative Transfers of Korean Characters to Acquisition of Chinese Characters Writing

Positive and Negative Transfers of Korean Characters to Acquisition of Chinese Characters Writing

Listriodon guptai Pilgrim, 1926 (Mammalia, Suidae) from the early Miocene of the Bugti Hills, Balochistan, Pakistan: new insights into early Listriodontinae evolution and biogeography

New dental remains of listriodont suids are described from the lower member of the early to middle Miocene Vihowa Formation of the Bugti Hills, Pakistan. The material is homogeneous in terms of morphology and dimensions and referred as a whole to Listriodon guptai Pilgrim, 1926. This species is also mentioned in coeval deposits of the Zinda Pir Dome, Pakistan, dating back to ca. 19 Ma. The early occurrence of an advanced listriodont in Pakistan constrains the age of acquisition of several characters correlated to lophodonty within Listriodontini, and raises major questions about the early history of the Old World Listriodontinae. Strong morphological similarity between Listriodon guptai and the African species Listriodon akatikubas found in the late early Miocene of Maboko (Kenya, ca. 16.5 Ma) suggests that this latter is most probably a migrant originating from Asia.

Phylogenetic relationships among the lepidopteran and trichopteran suborders (Insecta) from the embryological standpoint1

Adopting the cladistic method in comparative embryology, 27 embryonic characters were analyzed to reconstruct the phylogenetic relationships among the lepidopteran and trichopteran suborders, viz., Annulipalpia, Integripalpia, Zeugloptera, Dacnonypha, Exoporia, Monotrysia, and Ditrysia. The resultant cladogram is basically coincident with that proposed by Kristensen. The order Trichoptera and Lepidoptera constitute a monophyletic group on the basis of one synapomorphy, the presence of well developed silk glands in embryos. The Trichoptera are separable from the Lepidoptera by the states of four characters. The Trichoptera, as a whole, are quite homogenous, and embryological data provide no rational ground for the separation of this order into the Annulipalpia and Integripalpia at a subordinal level. On the contrary, the embryonic development of the Lepidoptera becomes divergent from the most primitive condition to a specialized one according to suborders. The Zeugloptera are the sister group of all other Lepidoptera, because they share two apomorphies with the latter. The Dacnonypha are the most primitive next to the Zeugloptera, and have a sister-group relationship with the Exoporia + (Monotrysia + Ditrysia), being held together with the latter by five synapomorphies. Although the Exoporia retain almost as many plesiomorphic characters as the Dacnonypha, they have a sister-group relationship with the Monotrysia + Ditrysia, as inferred on the basis of two synapomorphies. The Monotrysia and Ditrysia have a sistergroup relationship, and are the most advanced groups in the Lepidoptera judging from their shared acquisition of many apomorphic characters.

The Fish–Tetrapod Transition: New Fossils and Interpretations

Our information on the transition between fish with fins and tetrapods with limbs and digits has increased manyfold in the last 15–20 years and especially in the last 5 or 10 years, with some spectacular finds of new material. Some of these include new tetrapod-like fish and very primitive tetrapods that help to resolve questions of the sequence of acquisition of tetrapod characters, the approximate timing of the events, the likely geographic location, and the circumstances under which it happened. Forelimbs and skulls became modified in advance of hind limbs, adapted for supporting the head and front of the body out of the water, probably in connection with air breathing. The likely time of origin for limbed tetrapods is between 385 and 380 million years ago, probably in the northern continent of Laurussia. The origin of limbed tetrapods did not coincide with the acquisition of full terrestriality, an outcome that probably arose in the Early Carboniferous. This later part of the story is documented by few fossils, though two in particular give key information. Studies of modern vertebrates, especially the evolutionary developmental genetics of Hox genes, are beginning to provide clues to the origin of digits.

Palaeontological and Molecular Evidence Linking Arthropods, Onychophorans, and other Ecdysozoa

Membership of Arthropoda in a clade of molting animals, the Ecdysozoa, has received a growing body of support over the past 10 years from analyses of DNA sequences from many genes together with morphological characters involving the cuticle and its molting. Recent analyses based on broad phylogenomic sampling strengthen the grouping of cycloneuralian worms and arthropods as Ecdysozoa, identify the velvet worms (Phylum Onychophora) as the closest living relatives of arthropods, and interpret segmentation as having separate evolutionary origins in arthropods and annelid worms. Determining whether the water bears (Phylum Tardigrada) are more closely related to onychophorans and arthropods or to unsegmented cycloneuralians such as roundworms (Nematoda) is an open question. Fossil taxa such as the Cambrian anomalocaridids provide a combination of arthropod and cycloneuralian characters that is not observed in any living ecdysozoan. Fossils break up long branches and help to resolve the sequence of character acquisition at several critical nodes in the arthropod tree, notably in a suite of Cambrian lobopodians that may include the stem groups of each of the major panarthropod lineages.

A new oligocene astrapothere (mammalia, meridiungulata) from patagonia and a new appraisal of astrapothere there phylogeny

Synopsis The new genus and species Maddenia lapidaria from pre‐Deseadan (Oligocene) deposits at the southern cliff of Lake Colhue Huapí (Chubut Province, Argentina) is described. This small Oligocene astrapothere represents an adaptive type that is distinct from the usual one proposed for post‐Casamayoran (Eocene) forms. Because of its small body size and dental characters, preliminarily interpreted as primitive, this genus was originally considered to be a member of the Albertogaudryinae surviving into the Oligocene and coexisting with more derived species. However, a phylogenetic analysis based on dental and mandibular characters indicates that Maddenia lapidaria is, rather, the sister group of the giant Deseadan and later astrapotheriids by sharing with them a well developed upper molar crista and crochet, P4 lingual valley, p2 absent and superficial premolar and molar hypoflexid. Maddenia lapidaria has highly molarised upper premolars, representing the top‐most expression of the evolutionary trend of increasing premolar complexity in the Astrapotheria. Asubsequent evolutionary turnover resulted in a reduction of the size and number of premolars and secondary occlusal simplification, coinciding with an abrupt increase in hypsodonty and body size that characterise the more advanced astrapotheriids. This interpretation challenges the progressive acquisition of astrapotheriid characters traditionally accepted for the group. The moderately deep premolar and molar hypoflexid seen in Maddenia lapidaria is interpreted as the ancestral condition for the younger astrapotheres, which, on the one hand, would have evolved into the complete reduction of this structure in the Uruguaytheriinae and, on the other hand, the development of a deep labial vertical cleft in the Astrapotheriinae (Astrapotherium and Astrapothericulus).

The cranial endoskeleton of Tiktaalik roseae

Among the morphological changes that occurred during the 'fish-to-tetrapod' transition was a marked reorganization of the cranial endoskeleton. Details of this transition, including the sequence of character acquisition, have not been evident from the fossil record. Here we describe the braincase, palatoquadrate and branchial skeleton of Tiktaalik roseae, the Late Devonian sarcopterygian fish most closely related to tetrapods. Although retaining a primitive configuration in many respects, the cranial endoskeleton of T. roseae shares derived features with tetrapods such as a large basal articulation and a flat, horizontally oriented entopterygoid. Other features in T. roseae, like the short, straight hyomandibula, show morphology intermediate between the condition observed in more primitive fish and that observed in tetrapods. The combination of characters in T. roseae helps to resolve the relative timing of modifications in the cranial endoskeleton. The sequence of modifications suggests changes in head mobility and intracranial kinesis that have ramifications for the origin of vertebrate terrestriality.

The braincase and jaws of a Devonian ‘acanthodian’ and modern gnathostome origins

Modern gnathostomes (jawed vertebrates) emerged in the early Palaeozoic era, but this event remains unclear owing to a scant early fossil record. The exclusively Palaeozoic 'acanthodians' are possibly the earliest gnathostome group and exhibit a mosaic of shark- and bony fish-like characters that has long given them prominence in discussions of early gnathostome evolution. Their relationships with modern gnathostomes have remained mysterious, partly because their un-mineralized endoskeletons rarely fossilized. Here I present the first-known braincase of an Early Devonian (approximately 418-412 Myr bp) acanthodian, Ptomacanthus anglicus, and re-evaluate the interrelationships of basal gnathostomes. Acanthodian braincases have previously been represented by a single genus, Acanthodes, which occurs more than 100 million years later in the fossil record. The braincase of Ptomacanthus differs radically from the osteichthyan-like braincase of Acanthodes in exhibiting several plesiomorphic features shared with placoderms and some early chondrichthyans. Most striking is its extremely short sphenoid region and its jaw suspension, which displays features intermediate between some Palaeozoic chondrichthyans and osteichthyans. Phylogenetic analysis resolves Ptomacanthus as either the most basal chondrichthyan or as the sister group of all living gnathostomes. These new data alter earlier conceptions of basal gnathostome phylogeny and thus help to provide a more detailed picture of the acquisition of early gnathostome characters.

The Phylogeny of Ceratosauria (Dinosauria: Theropoda)

Synopsis Recent discoveries and analyses have drawn increased attention to Ceratosauria, a taxonomically and morphologically diverse group of basal theropods. By the time of its first appearance in the Late Jurassic, the group was probably globally distributed. This pattern eventually gave way to a primarily Gondwanan distribution by the Late Cretaceous. Ceratosaurs are one of several focal groups for studies of Cretaceous palaeobiogeography and their often bizarre morphological developments highlight their distinctiveness. Unfortunately, lack of phylogenetic resolution, shifting views of which taxa fall within Ceratosauria and minimal overlap in coverage between systematic studies, have made it difficult to explicate any of these important evolutionary patterns. Although many taxa are fragmentary, an increase in new, more complete forms has clarified much of ceratosaur anatomy, allowed the identification of additional materials and increased our ability to compare specimens and taxa. We studied nearly 40 ceratosaurs from the Late Jurassic‐Late Cretaceous of North and South America, Europe, Africa, India and Madagascar, ultimately selecting 18 for a new cladistic analysis. The results suggest that Elaphrosaurus and its relatives are the most basal ceratosaurs, followed by Ceratosaurus and Noasauridae + Abelisauridae (= Abelisauroidea). Several additional forms were identified as noasaurids, including Genusaurus. Within Abelisauridae, our analysis reveals a clade including Majungasaurus and the Indian forms, as well as a more weakly supported clade comprising Carnotaurus and Ilokelesia. These results greatly clarify the sequence of character acquisition leading to, and within, Abelisauroidea. Thanks to new noasaurid materials (particularly Masiakasaurus), numerous formerly ambiguous characters can now be resolved as either abelisaurid, noasaurid or abelisauroid synapomorphies. Skull and forelimb shortening, for example, now appear to be features confined to Abelisauridae. Nevertheless, a great deal of phylogenetic resolution is lacking, particularly among noasaurids, which hampers attempts to glean meaningful biogeographical information from the phylogeny. As a result, tem poral and geographical sampling biases are probably contributing to the apparent patterns in the data and we suggest that definitive answers must await new discoveries. None of the recent ceratosaurian discoveries bear directly on the controversy surrounding latest Cretaceous ceratosaur biogeography.

A reappraisal of the origin and basal radiation of the Osteichthyes

ABSTRACT The earliest Actinoptergyii (ray-finned fishes) and Sarcopterygii (lobe-finned fishes) have been studied intensely, and a consistent picture of interrelationships has begun to emerge for the latter. In contrast, there has been minimal documentation of the pattern of character acquisition leading to the osteichthyan crown. We review the synapomorphies proposed for various levels within osteichthyan phylogeny (total group; Acanthodes + crown group; crown group; Sarcoptergyii; Actinopterygii), confirming some, rejecting others, and making new additions. This distribution of characters is used to interpret the placement of problematic Siluro-Devonian genera traditionally assigned to Actinopterygii, and suggests these taxa are stem osteichthyans. Earlier placements of these forms within the crown are symptomatic of taxonomies based on unpolarized similarities rather than synapomorphies.

Phonological awareness in young Chinese children

Two studies explored the nature of phonological awareness (PA) in Chinese. In Study 1, involving 146 children, awareness of phoneme onset did not differ from chance levels at ages 3-5 years in preschool but increased to 70% correct in first grade, when children first received phonological coding (Pinyin) instruction. Similarly, tone awareness was at better than chance levels from second year kindergarten (age 4), but increased strongly and significantly in first grade to 74% accuracy. In contrast, syllable and rime awareness increased gradually and steadily across ages 3-6 years. Patterns suggest different influences of age and literacy instruction for different PA levels. In Study 2, involving 202 preschoolers, variance in Chinese character recognition was best explained by tasks of syllable awareness, tone awareness, and speeded naming. Findings underscore the unique importance of both tone and syllable for early character acquisition in Chinese children.

Computer‐based teaching of word construction and reading in two students with developmental disabilities

AbstractStudents with developmental disabilities often have difficulty in learning the systematic relations between syllables (auditory stimuli) and characters (visual stimuli) required for reading. Two students with developmental disabilities participated in the present study which used computer‐based teaching applied in the home. We examined whether the students could read individual Japanese Hiragana characters after training with a constructional MTS procedure with differential outcome (DO) that was designed to teach word‐construction for pictured sample stimuli. The DO procedure provided the differential stimulus (in this case spoken syllables) after response selection. The results showed that the students not only acquired appropriate word‐construction responses through this task, they also learned to read Hiragana characters without direct training of this skill. The results are discussed in terms of the effect of the constructional MTS procedure with DO on the acquisition and transfer of reading characters and the applicability of computer‐based home teaching. Copyright © 2007 John Wiley & Sons, Ltd.

A primitive ornithischian dinosaur from the Late Triassic of South Africa, and the early evolution and diversification of Ornithischia

Although the group played an important role in the evolution of Late Mesozoic terrestrial ecosystems, the early evolutionary history of the ornithischian dinosaurs remains poorly understood. Here, we report on a new primitive ornithischian, Eocursor parvus gen. et sp. nov. from the Late Triassic (?Norian) Lower Elliot Formation of South Africa. Eocursor is known from a single specimen comprising substantial cranial and postcranial material and represents the most complete Triassic member of Ornithischia, providing the earliest evidence for the acquisition of many key ornithischian postcranial characters, including an opisthopubic pelvis. A new phylogenetic analysis positions this taxon near the base of Ornithischia, as the sister taxon to the important and diverse clade Genasauria. The problematic clade Heterodontosauridae is also positioned basal to Genasauria, suggesting that an enlarged grasping manus may represent a plesiomorphic ornithischian condition. This analysis provides additional phylogenetic support for limited ornithischian diversity during the Late Triassic, and suggests that several major ornithischian clades may have originated later than generally believed. There are few morphological differences between Late Triassic and Early Jurassic ornithischians, supporting previous suggestions that the Early Jurassic ornithischian radiation may simply represent the filling of vacant ecological space following Late Triassic terrestrial extinctions.

A Study on the Effects of Acquisition of Chinese Characters on Declaration of Korean and Chinese Characters Used in Combination

A Study on the Effects of Acquisition of Chinese Characters on Declaration of Korean and Chinese Characters Used in Combination

Poriferan paraphyly and its implications for Precambrian palaeobiology

Abstract Well-supported molecular phylogenies, combined with knowledge of modern biology, can lead to new inferences about the sequence of character acquisition in early animal evolution, the taxonomic affinity of enigmatic Precambrian and Cambrian fossils, and the Proterozoic Earth system in general. In this paper we demonstrate, in accordance with previous molecular studies, that sponges are paraphyletic, and that calcisponges are more closely related to eumetazoans than they are to demosponges. In addition, our Bayesian analysis finds the Homoscleromorpha, previously grouped with the demosponges, to be even more closely related to eumetazoans than are the calcisponges. Hence there may be at least three separate extant ‘poriferan’ lineages, each with their own unique skeleton. Because spiculation is convergent within ‘Porifera’, differences between skeletonization processes in enigmatic Cambrian taxa such as Chancelloria and modern sponges does not mean that these Problematica are not organized around a poriferan body plan, namely a benthic, sessile microsuspension feeding organism. The shift from the anoxic and sulphidic deep ocean that characterized the mid-Proterozoic to the well-ventilated Phanerozoic ocean occurs before the evolution of macrozooplanton and nekton, and thus cannot have been caused by the advent of faecal pellets. However, the evolution and ecological dominance of sponges during this time interval provides both a mechanism for the long-term generation of isotopically-light CO 2 that would be recorded in carbon isotopic excusions such as the ‘Shuram’ event, and an alternative mechanism for the drawdown and sequestration of dissolved organic carbon within the sediment.

Morphological and molecular phylogenetic context of the angiosperms: contrasting the 'top-down' and 'bottom-up' approaches used to infer the likely characteristics of the first flowers

Recent attempts to address the long-debated 'origin' of the angiosperms depend on a phylogenetic framework derived from a matrix of taxa versus characters; most assume that empirical rigour is proportional to the size of the matrix. Sequence-based genotypic approaches increase the number of characters (nucleotides and indels) in the matrix but are confined to the highly restricted spectrum of extant species, whereas morphology-based approaches increase the number of phylogenetically informative taxa (including fossils) at the expense of accessing only a restricted spectrum of phenotypic characters. The two approaches are currently delivering strongly contrasting hypotheses of relationship. Most molecular studies indicate that all extant gymnosperms form a natural group, suggesting surprisingly early divergence of the lineage that led to angiosperms, whereas morphology-only phylogenies indicate that a succession of (mostly extinct) gymnosperms preceded a later angiosperm origin. Causes of this conflict include: (i) the vast phenotypic and genotypic lacuna, largely reflecting pre-Cenozoic extinctions, that separates early-divergent living angiosperms from their closest relatives among the living gymnosperms; (ii) profound uncertainty regarding which (a) extant and (b) extinct angiosperms are most closely related to gymnosperms; and (iii) profound uncertainty regarding which (a) extant and (b) extinct gymnosperms are most closely related to angiosperms, and thus best serve as 'outgroups' dictating the perceived evolutionary polarity of character transitions among the early-divergent angiosperms. These factors still permit a remarkable range of contrasting, yet credible, hypotheses regarding the order of acquisition of the many phenotypic characters, reproductive and vegetative, that distinguish 'classic' angiospermy from 'classic' gymnospermy. The flower remains ill-defined and its mode (or modes) of origin remains hotly disputed; some definitions and hypotheses of evolutionary relationships preclude a role for the flower in delimiting the angiosperms. We advocate maintenance of parallel, reciprocally illuminating programmes of morphological and molecular phylogeny reconstruction, respectively supported by homology testing through additional taxa (especially fossils) and evolutionary-developmental genetic studies that explore genes potentially responsible for major phenotypic transitions.