What a New Model of Skeletal Homologies Tells Us About Asteroid Evolution

The Extraxial-Axial Theory (EAT) is applied to the body wallhomologies of asteroids. Attempts to characterize major platesystems of asteroids as axial or extraxial, particularly thosethat are highly organized into series, can be problematic. However,the Optical Plate Rule (OPR) is instrumental in establishingthat ambulacrals and terminals are axial. It is equally clearthat the region aboral to the marginal frame is a part of theperforate extraxial body wall (with the possible exception ofthe centrodorsal, which is likely imperforate extraxial). Previouslyestablished EAT criteria, particularly those strongly rootedin the embryologically expressed boundary between axial andextraxial body wall in larvae, suggest that marginals, and perhapsadambulacrals, are extraxial in origin. We also explore theextraxial nature and phylogenetic significance of the odontophore.Our data from both juveniles and adults show that plate andtube foot addition sequences occur according to the OPR, andshed light on poorly known homologies of the asteroid mouthframe. These data indicate that the mouth angle ossicle mustat least contain the first ambulacral, although we cannot ruleout the possibility that the first adambulacral also contributesto the construction of this ossicle. The interpretations providedby the EAT for all ossicles suggest a synapomorphy scheme forsomasteroids, ophiuroids, and asteroids.     

Arrays in rays: terminal addition in echinoderms and its correlation with gene expression

The echinoderms are deuterostomes that superimpose radial symmetry upon bilateral larval morphology. Consequently, they are not the first animals that come to mind when the concepts of segmentation and terminal addition are being discussed. However, it has long been recognized that echinoderms have serial elements along their radii formed in accordance with the ocular plate rule (OPR). The OPR is a special case of terminal growth, forming elements of the ambulacra that define the rays in echinoderms. New elements are added at the terminus of the ray, which may or may not be marked by a calcified element called the terminal plate (the "ocular" of sea urchins). The OPR operates in every echinoderm, from the occasionally bizarre fossils of the Cambrian to the most familiar extant taxa. Using the OPR and other criteria of recognition, echinoderm body wall can be divided into two main regions: extraxial components are associated with the somatocoels, axial components (formed in accordance with the OPR) with the hydrocoel. We compare patterns of development in axial regions of echinoderms with those found in the anterior-posterior axes of the earliest echinoderms as well as other invertebrates. Although axial and extraxial skeletons appear to be composed of the same biomineral matrix, the genes involved in patterning these two skeletal components are likely distinct. During development of the axial skeleton, for instance, the genes engrailed and orthodenticle are expressed in spatial and temporal patterns consistent with the OPR. Other genes such as distal-less seem to demarcate early ontogenetic boundaries between the axial rudiment and the extraxial larval body. There is a complex and pervasive reorganization of gene expression domains to produce the highly divergent morphologies seen in the Echinodermata. We integrate morphological and genetic information, particularly with respect to the origins of radial symmetry in the rudiment, and the concomitant development of the rays.     

Oral Region Homologies in Paleozoic Crinoids and Other Plesiomorphic Pentaradial Echinoderms

The phylogenetic relationships between major groups of plesiomorphic pentaradial echinoderms, the Paleozoic crinoids, blastozoans, and edrioasteroids, are poorly understood because of a lack of widely recognized homologies. Here, we present newly recognized oral region homologies, based on the Universal Elemental Homology model for skeletal plates, in a wide range of fossil taxa. The oral region of echinoderms is mainly composed of the axial, or ambulacral, skeleton, which apparently evolved more slowly than the extraxial skeleton that forms the majority of the body. Recent phylogenetic hypotheses have focused on characters of the extraxial skeleton, which may have evolved too rapidly to preserve obvious homologies across all these groups. The axial skeleton conserved homologous suites of characters shared between various edrioasteroids and specific blastozoans, and between other blastozoans and crinoids. Although individual plates can be inferred as homologous, no directly overlapping suites of characters are shared between edrioasteroids and crinoids. Six different systems of mouth (peristome) plate organization (Peristomial Border Systems) are defined. These include four different systems based on the arrangement of the interradially-positioned oral plates and their peristomial cover plates, where PBS A1 occurs only in plesiomorphic edrioasteroids, PBS A2 occurs in plesiomorphic edrioasteroids and blastozoans, and PBS A3 and PBS A4 occur in blastozoans and crinoids. The other two systems have radially-positioned uniserial oral frame plates in construction of the mouth frame. PBS B1 has both orals and uniserial oral frame plates and occurs in edrioasterid and possibly edrioblastoid edrioasteroids, whereas PBS B2 has exclusively uniserial oral frame plates and is found in isorophid edrioasteroids and imbricate and gogiid blastozoans. These different types of mouth frame construction offer potential synapomorphies to aid in parsimony-based phylogenetics for exploring branching order among stem groups on the echinoderm tree of life.     

Arms versus brachioles: Morphogenetic basis of similarity and differences in food-gathering appendages of pelmatozoan echinoderms

The similarity in the skeleton model of the brachiolar food-gathering system of Blastozoa and the arm system of Crinozoa, including the apical growth with enantomorphous displacement of skeletal ele-ments, is explained by the primary organizing role of the radial ambulacral canals, which have the same branching model for ambulacral tentacles. The difference in the positions of brachioles and arms relative to the theca (exothecal and endothecal) is associated with the formation of the primary ambulacral tentacles directly on the body surface of the majority of Blastozoa, particularly, the closed vestibular cavity of crinoids. The supporting skeleton of brachioles arose as a branch of the plates covering the floor of the ambulacrum, if they were present, or formed similarly as a new formation outside the theca. The supporting skeleton of arms, brachials, developed as a result of the serial growth of plates positioned radially at the boundary of the aboral skeleton and tegmen formed due to the appearance of the vestibulum. The hypothesis of the inductive role of hydrocoel and its radial ambulacral appendages, which organize the arrangement of skeletal elements in the morphogenesis of echinoderms, enables the refinement of the principle of skeleton division into the axial and extraxial parts. The axial skeleton has a developmental model formed under the control of the radial ambu-lacral canals. Remaining skeleton is extraxial, subdivided into the symmetrized part arranged under direct or indirect organizing effect of the hydrocoel and unregulated, nonsymmetrized part, which is not connected initially with the influence of the hydrocoel.     

Evolution to the extreme: origins of the highly modified apical system in pourtalesiid echinoids

The apical system of the genus Pourtalesia displays a plate architecture that falls so far outside that typical of other echinoids that plate homologies remain problematic. A new approach using the Extraxial–Axial Theory (EAT) that develops homologies for the Echinodermata is proposed. The exploration of apical plate patterns throughout ontogenetic sequences shows that the typical holasteroid pattern found in the youngest specimens undergoes a series of disturbances that result in a multiple disjunction accompanied by isolation or disappearance of certain genital plates. We propose a new interpretation of the apical architecture of the genus that agrees with: (1) the plate addition processes as predicted by the EAT; (2) patterns observed in other genera of the Pourtalesiidae as well as in its sister‐group (plexechinids); and (3) the patterns known from Palaeocene holasteroids. In the context of the EAT, the genus Pourtalesia appears to represent the extreme in a reduction of the extraxial part of the body wall. © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society, 2004, 140 , 137–155.     

Modularity and heterochronies in the evolution of metazoa: Paleontological aspect

All organisms are formed of more or less independent elements, modules. Paleontology deals with morphological modules preserved in the fossil state and allows their evolution within taxa of different levels to be reconstructed. Modularity provides organisms with the ability to evolve, since changes in one module does not influence others, nor disturb the integrity of organism. Each organism may have unique modules represented by a single copy and serial modules developing according to a certain symmetry type. Serial terminal growth is characteristic of ambulacra of echinoderms, in which it is combined with alternating appearance of structures on the right and left of the symmetry plane. The morphology of the solute Maennilia estonica, which has been investigated in detail, shows that the growth model for the brachiola is similar to the model for ambulacra of sea urchins, but without an ocular plate. Probably, the hydrocoel initially induced the appearance of a skeleton necessary for its activity and organized its development according to its own model of terminal growth. Subsequently, the axial skeleton appearing following this pattern could have organized the growth of adjacent parts of the extraxial skeleton following the same model to form a united module. The fusion of modules could have resulted from heterochronies. Extant and extinct material connected with the change in the anteroposterior axis in evolutionary and ontogenetic development of echinoderms provides a prominent example of heterochronies. Heterochronies were the mechanism connecting characters into an integrated ensemble of the body plan. Archaic diversity reflects an attempt to create a new body plan. Various manifestations of archaic diversity show that the emergence of a new higher taxon is connected with the combination of a number of characters united in an integrated complex forming the body plan which is stable from the moment of appearance due to strict recursive relationships between its modules rather than with the acquisition of an individual character, even if it is very important.     

A re‐interpretation of the ambulacral system of Eumorphocystis (Blastozoa,Echinodermata) and its bearing on the evolution of early crinoids

Recent debates over the evolutionary relationships of early echinoderms have relied heavily on morphological evidence from the feeding ambulacral system. Eumorphocystis, a Late Ordovician diploporitan, has been a focus in these debates because it bears ambulacral features that show strong morphological similarity to early crinoid arms. Undescribed and well‐preserved specimens of Eumorphocystis from the Bromide Formation (Oklahoma, USA) provide new data illustrating that composite arms supported by a radial plate that bear a triserial arrangement of axial and extraxial components encasing a coelomic extension can also be found in blastozoans. Previous reports have considered these arm structures to be restricted to crinoids; these combined features have not been previously observed in blastozoan echinoderms. Phylogenetic analyses suggest that Eumorphocystis and crinoids are sister taxa and that shared derived features of these taxa are homologous. The evidence from the arms of Eumorphocystis suggests that crinoid arms were derived from a specialized blastozoan ambulacral system that lost feeding brachioles and strongly suggests that crinoids are nested within blastozoans.     

Diversity in skeletal architecture influences biological heterogeneity and Symbiodinium habitat in corals

Scleractinian corals vary in response to rapid shifts in the marine environment and changes in reef community structure post-disturbance reveal a clear relationship between coral performance and morphology. With exceptions, massive corals are thought to be more tolerant and branching corals more vulnerable to changing environmental conditions, notably thermal stress. The typical responses of massive and branching coral taxa, respectively, are well documented; however, the biological and functional characteristics that underpin this variation are not well understood. We address this gap by comparing multiple biological attributes that are correlated with skeletal architecture in two perforate (having porous skeletal matrices with intercalating tissues) and two imperforate coral species (Montipora aequituberculata, Porites lobata, Pocillopora damicornis, and Seriatopora hystrix) representing three morphotypes. Our results reveal inherent biological heterogeneity among corals and the potential for perforate skeletons to create complex, three-dimensional internal habitats that impact the dynamics of the symbiosis. Patterns of tissue thickness are correlated with the concentration of symbionts within narrow regions of tissue in imperforate corals versus broad distribution throughout the larger tissue area in perforate corals. Attributes of the perforate and environmentally tolerant P. lobata were notable, with tissues ～5 times thicker than in the sensitive, imperforate species P. damicornis and S. hystrix. Additionally, P. lobata had the lowest baseline levels of superoxide and Symbiodinium that provisioned high levels of energy. Given our observations, we hypothesize that the complexity of the visually obscured internal environment has an impact on host–symbiont dynamics and ultimately on survival, warranting further scientific investigation.     

Ultrastructure of Axial Vascular and Coelomic Organs in Comasterid Featherstars (Echinodermata: Crinoidea)

Abstract The spongy body of Davidaster rubiginosa, D. discoidea, and Comactinia meridionalis, is an axial haemal plexus consisting of two structurally similar, but positionally distinct, regions: an oral circumesophageal part and an aboral part which lies lateral to the axial organ. The axial organ is a large axial blood vessel which is infiltrated by hollow cellular tubes lined with monociliated epithelial cells. The spongy body plexus is a tangle of small blood vessels overlain by podocytes and myocytes. The spongy body and the axial organ are situated in the axial coelom, which is confluent with the perivisceral coelom, the water vascular system, and the parietal canals. The parietal canals open to the exterior via ciliated tegmenal ducts and surface pores. The crinoid spongy body is morphologically similar to the axial gland of asteroids, ophiuroids, and echinoids (AOE). Although the axial glands of these three classes of echinoderms are mutually homologous structures, the homology of the crinoid spongy body and the AOE axial gland is questionable because of differences in organization and developmental origin. Alternatively, the crinoid spongy body may be homologous to asteroid gastric haemal tufts, which are podocyte-covered blood vessels suspended in the perivisceral coelom. The functional organization of the spongy body suggests a filtration nephridium and predicts an excretory function. An alternative hypothesis is that the spongy body is a site of nutrient transfer from the blood vascular system to the perivisceral coelom.     

Relationships between foraminiferal assemblages and depositional sequences in Jahrum Formation,Ardal area (Zagros Basin,SW Iran)

The Jahrum Formation was deposited in the foreland basin in southwest Iran (Zagros Basin). The Zagros mountain belt of Iran, a part of the Alpine–Himalayan system, extends from the NW Iranian border through to SW Iran, up to the strait of Hormuz. The various facies of the Jahrum Formation were deposited in four main genetically related depositional environments, including: tidal flat, lagoon, shoal and open marine. These are represented by 14 microfacies. The Jahrum Formation represents sedimentation on a carbonate ramp. Tidal flat facies are represented by fenestral fabric, stromatolitic boundstone and thin-bedded planes. Carbonate deposition in a shallow marine lagoon was characterised by wacke–packstone, dominated by various taxa of imperforate foraminifer. The shoals are made up of medium- to coarse-grained skeletal and peloidal grainstone. This facies was deposited predominantly in an active high energy wave and current regime, and grades basinward into middle ramps facies are represented by wackestones–packstones with a diverse assemblage of echinoderm and large benthic foraminifers with perforate wall. Outer ramp facies consist of alternating marl and limestones rich in pelagic foraminifera. There is no evidence for resedimentation processes in this facies belt. The sequence stratigraphy study has led to recognition of three third-order depositional sequences.     

Facies,paleoenvironment, carbonate platform and facies changes across Paleocene Eocene of the Taleh Zang Formation in the Zagros Basin,SW-Iran

The Paleocene–Eocene Taleh Zang Formation of the Zagros Basin is a sequence of shallow-water carbonates. We have studied carbonate platform, sedimentary environments and its changes based on the facies analysis with particular emphasis on the biogenic assemblages of the Late Paleocene Sarkan and Early Eocene Maleh kuh sections. In the Late Paleocene, nine microfacies types were distinguished, dominated by algal taxa and corals at the lower part and larger foraminifera at the upper part. The Lower Eocene section is characterised by 10 microfacies types, which are dominated by diverse larger foraminifera such as alveolinids, orbitolitids and nummulitids. The Taleh Zang Formation at the Sarkan and Maleh kuh sections represents sedimentation on a carbonate ramp.

The deepening trends show a gradual increase in perforate foraminifera, the deepest environment is marked by the maximum occurrence of perforate foraminifers (Nummulites), while the shallowing trends are composed mainly of imperforate foraminifera and also characterised by lack of fossils in tidal flat facies.

Based on the facies changes and platform evolution, three stages are assumed in platform development: I; algal and coralgal colonies (coralgal platform), II; coralgal reefs giving way to larger foraminifera, III; dominance of diverse and newly developing larger foraminifera lineages in oligotrophic conditions.     

Sedimentary facies and paleoenvironmental interpretation of the Oligocene larger-benthic-foraminifera-dominated Qom Formation in the northeastern margin of the Tethyan Seaway

The well-exposed outcrops of the Bujan, northern Abadeh, and Varkan stratigraphic sections of the Qom Formation in the Iranian part of the “northeastern margin” of the Tethyan Seaway were characterized by abundant biogenic components dominated by foraminifers, coralline red algae, and corals. The Qom Formation is Rupelian–Chattian in age in the study areas. Based on the field investigations, depositional textures, and dominant biogenic components, fifteen (carbonate and terrigenous) facies were identified. These facies can be grouped into four depositional environments: open marine, open lagoon, restricted lagoon, and continental braided streams. The marine facies were deposited on a ramp-type platform. The euphotic inner ramp was characterized mainly by imperforate foraminifera, with co-occurrence of some perforate taxa. These facies passed basinward into a mesophotic (middle) ramp with Neorotalia packstone (F5), coral, coralline algae, perforate foraminiferal packstone (F4), and coral patch reefs (F7). The deeper, oligophotic ramp facies were marly packstones with planktonic and hyaline benthic foraminifera, including large lepidocyclinids and nummulitids. The abundance of perforate foraminifera and the absence of facies indicating restricted lagoonal or intertidal settings suggest that the Varkan section was deposited mainly in open marine settings with normal salinity. The prevalence of larger benthic foraminiferal and red algal assemblages, together with the coral facies, indicates that carbonate production took place in tropical–subtropical waters.     

The Animal Axis

Soft-bodied animals are an answer to the problem, solved foreach species over evolutionary time, to design a cylindrical,motile machine composed of pliant polymeric materials (collagenand glycoproteins) and actuated by a contractile polymer (actomyosin). The vertebrate body is a cylindrical set of pliant collagenousmembranes. Axial notochords and backbones occur where membranesintersect. The basis for all vertebrate architecture is thecollagen fiber that best functions to resist tension. Axialcompressive forces in notochords and backbones occur as tensilestresses in collagen fibers in intervertebral discs and zygapohysealligaments. Bone provides local stiffening where muscles pull.Large muscle masses apply large forces via tendons thus allowingfor leverage in the function of axes of bodies and appendages.Although isolated species in invertebrate phyla have notochord-or backbone-like structures, only echinoderms and vertebrateshave a central axis to resist axial compression. Design is auseful tool in forming scientific hypotheses.     

Biostratigraphy and paleoecology of the Oligo-Miocene succession in Fars and Khuzestan areas (Zagros Basin,SW Iran)

Paleontological and biostratigraphical studies on carbonate platform succession from southwest Iran documented a great diversity of shallow-water benthic foraminifera during the Oligocene–Miocene. Larger foraminifera are the main means for the stratigraphic zonation of carbonate sediments. The distributions of larger benthic foraminifera in two outcrop sections (Abolhayat and Lali) in the Zagros Basin, Iran, are used to determine the age of the Asmari Formation. Four assemblage zones have been recognized by distribution of the larger benthic foraminifera in the study areas. Assemblage 3 (Aquitanian age) and 4 (Burdigalian age) have not been recognized in the Abolhayat section (Fars area), due to sea-level fall. The end Chattian sea-level fall restricted marine deposition in the Abolhayat section and Asmari Formation replaced laterally by the Gachsaran Formation. This suggests that the Miocene part of the formation as recognized in the Lali section (Khuzestan area) of the Zagros foreland basin is not present in the Abolhayat outcrop. The distribution of the Oligocene larger benthic foraminifera indicates that shallow marine carbonate sediments of the Asmari Formation at the study areas have been deposited in the photic zone of tropical to subtropical oceans. Based on analysis of larger benthic foraminiferal assemblages and microfacies features, three major depositional environments are identified. These include inner shelf, middle shelf and outer shelf. The inner shelf facies is characterized by wackestone–packstone, dominated by various taxa of imperforate foraminifera. The middle shelf is represented by packstone–grainstone to floatstone with a diverse assemblage of larger foraminifera with perforate wall. Basinwards is dominated by argillaceous wackestone characterized by planktonic foraminifera and large and flat nummulitidae and lepidocyclinidae. Planktonic foraminifera wackestone is the dominant facies in the outer shelf.     

Variabilité architecturale du test chez le genre Collyrites (Echinoidea, Disasteroidea) au Jurassique moyen

The aim of this paper is to study the evolution of the architecture of the « apical system–periproct complex » of the genus Collyrites (Echinoidea, Disasteroidea) for species from the Bathonian and Callovian stages (Middle Jurassic). The studied material comes from several localities of the Paris basin. The apical system of the genus Collyrites is subdivided in two parts: (i) an anterior part composed by four genital (1, 2, 3, 4) and three ocular (II, III, IV) plates, called trivium; (ii) a posterior part composed by two ocular plates (I, V) and one genital plate (5), without gonopor, which circle the periproct, called bivium. The genital plate 5, which may collapse in the periproct, is not always visible. The Bathonian–Callovian transition is marked by a subdivision of the bivium in two parts: the periproct breaks up from the posterior ocular plates (I, V). These morphological changes are associated with architectural modifications. The trivium stays relatively stable during the Bathonian and the Callovian, but a supplementary plate may be inserted into the trivium. The bivium shows important modifications linked to the separation of the periproct and the ocular plates (I and V). Such a separation is marked by a strong development of supplementary plates, these ones keeping in connection with the periproct and the ocular plates I and V. The supplementary plates are more and more developed whereas the distance between the periproct and ocular plates increases. The connection between the trivium and the bivium is similarly provided by supplementary plates. The size of these plates seems to significantly increase between the Bathonian and the Callovian. Moreover, some specimens from the Bathonian and the Callovian may have an atypical architecture with a supplementary genital plate or a genital plate with two pores. The “extraxial axial theory” allows to recognize two types of skeleton: (i) an “axial skeleton” corresponding to ocular plates and plates of the ambulacra and interambulacra; (ii) an “extraxial skeleton” corresponding to the genital and supplementary plates, and the periproct. Architectural modifications between the Bathonian and the Callovian is a result of a more important development of the “extraxial skeleton” while the “axial skeleton” shows few modifications during this time interval.     

Evolution of the axial system in craniates: morphology and function of the perivertebral musculature

The axial musculoskeletal system represents the plesiomorphic locomotor engine of the vertebrate body, playing a central role in locomotion. In craniates, the evolution of the postcranial skeleton is characterized by two major transformations. First, the axial skeleton became increasingly functionally and morphologically regionalized. Second, the axial-based locomotion plesiomorphic for craniates became progressively appendage-based with the evolution of extremities in tetrapods. These changes, together with the transition to land, caused increased complexity in the planes in which axial movements occur and moments act on the body and were accompanied by profound changes in axial muscle function. To increase our understanding of the evolutionary transformations of the structure and function of the perivertebral musculature, this review integrates recent anatomical and physiological data (e.g., muscle fiber types, activation patterns) with gross-anatomical and kinematic findings for pivotal craniate taxa. This information is mapped onto a phylogenetic hypothesis to infer the putative character set of the last common ancestor of the respective taxa and to conjecture patterns of locomotor and muscular evolution. The increasing anatomical and functional complexity in the muscular arrangement during craniate evolution is associated with changes in fiber angulation and fiber-type distribution, i.e., increasing obliqueness in fiber orientation and segregation of fatigue-resistant fibers in deeper muscle regions. The loss of superficial fatigue-resistant fibers may be related to the profound gross anatomical reorganization of the axial musculature during the tetrapod evolution. The plesiomorphic function of the axial musculature -mobilization- is retained in all craniates. Along with the evolution of limbs and the subsequent transition to land, axial muscles additionally function to globally stabilize the trunk against inertial and extrinsic limb muscle forces as well as gravitational forces. Associated with the evolution of sagittal mobility and a parasagittal limb posture, axial muscles in mammals also stabilize the trunk against sagittal components of extrinsic limb muscle action as well as the inertia of the body's center of mass. Thus, the axial system is central to the static and dynamic control of the body posture in all craniates and, in gnathostomes, additionally provides the foundation for the mechanical work of the appendicular system.     

Pollen morphology of endemic species of the Horton Plains National Park,Sri Lanka

The pollen morphology of 27 endemic and palaeoecologically-important species belonging to 16 families and 20 genera from the mountain rain forests of Sri Lanka was studied using both light (LM) and scanning electron microscopy (SEM). The pollen grains exhibit a wide range of morphological characters. Their sizes (P and E) are in the range 10-53 2 9-60 mum, and they are distributed among seven shape classes. All the taxa have radially-symmetrical pollen grains except for Impatiens (bilateral). The amb varies from rounded to triangular, with intermediate shapes possible. The pollen grains of all the Lauraceae species studied are inaperturate and microspinose, with a thin, fragile, perforated exine. Sarcococca zeylanica (Buxaceae) has pantoporate pollen grains and a Croton -pattern consisting of faintly striate pegs of various shapes attached or enveloping the smooth rings. Colp(or)ate, syncolpate to parasyncolp(or)ate pollen grains with rugulate to perforate exine patterns occur in Eugenia mabaeoides ssp. mabaeoides and Syzygium ssp. (Myrtaceae). Osbeckia walkeri (Melastomataceae) has heterocolpate pollen with fossulate, foveolate to perforate exine pattern. 3-colporate, microreticulate pollen grains are met with in Euonymus revolutus (Celastraceae), and scabrate-microreticulate ones in Calophyllum walkeri (Clusiaceae). Hedyotis lawsoniae (Rubiaceae) pollen is microreticulate to perforate, while pollen of the Elaeocarpus (Elaeocarpaceae) species is 3-colporate, smooth to scabrate-perforate. Casearia thwaitesii (Flacourtiaceae) has 3-colporoidate pollen grains with a smooth, imperforate to occasionally sparsely perforate exine. Mastixia spp (Cornaceae) have a granular-perforate exine pattern, while Adinandra lasiopetala (Theaceae) has a smooth-perforate exine pattern. Triangular 3 (4)-colporate, and indistinctly faintly microreticulate-perforate pollen was found in Rhamnus arnottianus (Rhamnaceae), rugulate-perforate in Isonandra montana (Sapotaceae) and verrucate-perforate in Symplocos elegans (Symplocaceae). Glochidion coriaceum (Euphorbiaceae) has a 5-colporate grain with a coarsely reticulate exine pattern. Pollen grains of Impatiens walkeri and I. thwaitesii (Balsaminaceae) are bilateral, 4-colpate, reticulate and granular. A pollen key based on light microscope is constructed for all the taxa studied.     

Septal pore complex morphology in the Agaricomycotina (Basidiomycota) with emphasis on the Cantharellales and Hymenochaetales

The ultrastructure of septa and septum-associated septal pore caps are important taxonomic markers in the Agaricomycotina (Basidiomycota, Fungi). The septal pore caps covering the typical basidiomycetous dolipore septum are divided into three main phenotypically recognized morphotypes: vesicular-tubular (including the vesicular, sacculate, tubular, ampulliform, and globular morphotypes), imperforate, and perforate. Until recently, the septal pore cap-type reflected the higher-order relationships within the Agaricomycotina. However, the new classification of Fungi resulted in many changes including revision of existing and addition of new orders. Therefore, the septal pore cap ultrastructure of more than 325 species as reported in literature was related to this new classification. In addition, the septal pore cap ultrastructures of Rickenella fibula and Cantharellus formosus were examined by transmission electron microscopy. Both fungi have dolipore septa associated with perforate septal pore caps. These results combined with data from the literature show that the septal pore cap-type within orders of the Agaricomycotina is generally monomorphic, except for the Cantharellales and Hymenochaetales.It appears from the fungal phylogeny combined with the septal pore cap ultrastructure that the vesicular-tubular and the imperforate type both may have arisen from endoplasmic reticulum. Thereafter, the imperforate type eventually gave rise to the perforate septal pore cap-type.     

Novel conducting tissues in Lower Devonian plants

Elongate cells presumed to comprise water-conducting tissues are described from the central regions of short lengths of two naked, stomatiferous, coalified, axial fossils from Lochkovian (Lower Devonian) fluvial rocks in the Welsh Borderland. In one, a discrete central strand is predominantly composed of uniformly thickened cells that are compared with central tissues in coeval plants, e.g. Aglaophyton , and the hydroids of extant mosses. The other has at least two types of cells with pits of plasmodesmata dimensions that perforate only the inner layer of a bilayered wall. These are compared with liverwort and Takakia hydroids and the coeval S-type tracheids that characterize the Rhyniopsida. The affinities of the two axes remain equivocal. The relevance of plasmodesmata-derived pits to the evolution of diversity in water-conducting elements in early cmbryophytes is discussed.