Louis G. Zachos

Classification and description of dolomitic fabrics of rocks from the Floridan aquifer, U.S.A.

Abstract Biozones of the Lake City Formation, Avon Park Formation and Ocala Limestone are characterized by interbedded, massive, fossiliferous carbonate rocks (wackestones to grainstones) and thinly bedded, peloidal and carbonaceous rocks (mudstones and wackestones). Several horizons have been partly or completely dolomitized. A wide range of early to late stages of dolomitic fabrics are recognized. The fabrics are classified descriptively as equigranular (unimodal) or inequigranular (multimodal). Fabrics composed of crystals Two processes of dolomitization are suggested: (a) homogeneous dolomitization resulting in a single-stage development of microtextured (groundmass crystals

Significance of endangered and threatened plant natural products in the control of human disease

Significance In this report we describe a group of highly complex glycosides active against hepatitis C virus and a separate group of natural products active against established targets for the control of diabetes mellitus. These complex metabolites were found in the rare plant Diplostephium rhododendroides Hieron. from the mountains of Ecuador. This report illustrates the human health significance of protecting rare and endangered plants for the control of new and emerging diseases. The extinction of this particular plant would have taken with it promising opportunities to develop unique treatments for the control of two modern-day disease challenges. The genus Diplostephium is represented by several plant species with a history of use in traditional medicine in Central and South America. One in five of the world’s plant species is threatened with extinction according to the 2010 first global analysis of extinction risk. Tilman et al. predicted a massive ecological change to terrestrial plants within the next 50–100 y, accompanied by an increase in the number of global plant species facing extinction [Tilman D, et al. (2001) Proc Natl Acad Sci USA 98(10):5433–5440]. Most of the drug-producing plant families contain endangered species never previously studied for their utility to human health, which strongly validates the need to prioritize protection and assessment of these fragile and endangered groups [Zhu F, et al. (2011) Proc Natl Acad Sci USA 108(31):12943–12948]. With little prior attention given to endangered and rare plant species, this report provides strong justification for conservation of the rare plant Diplostephium rhododendroides Hieron., as well as other potential drug-producing endangered species in this and other groups.

A new computational growth model for sea urchin skeletons.

A new computational model has been developed to simulate growth of regular sea urchin skeletons. The model incorporates the processes of plate addition and individual plate growth into a composite model of whole-body (somatic) growth. A simple developmental model based on hypothetical morphogens underlies the assumptions used to define the simulated growth processes. The data model is based on a Delaunay triangulation of plate growth center points, using the dual Voronoi polygons to define plate topologies. A spherical frame of reference is used for growth calculations, with affine deformation of the sphere (based on a Young-Laplace membrane model) to result in an urchin-like three-dimensional form. The model verifies that the patterns of coronal plates in general meet the criteria of Voronoi polygonalization, that a morphogen/threshold inhibition model for plate addition results in the alternating plate addition pattern characteristic of sea urchins, and that application of the Bertalanffy growth model to individual plates results in simulated somatic growth that approximates that seen in living urchins. The model suggests avenues of research that could explain some of the distinctions between modern sea urchins and the much more disparate groups of forms that characterized the Paleozoic Era.

Heterochronic hierarchies: Application and theory in evolution

Heterochrony is an abundant mode of evolution that is not limited to minor allometric changes, contrary to common belief. This misconception, along with confusion over terminology, has resulted from historically restricting our view to timing and rate changes that occur late in ontogeny and affect only major organs. By focusing on finer scales of space and time, at cellular levels and changes early in ontogeny, much of the confusion over heterochrony is eliminated. Heterochrony is redefined: change in the timing and rate of dialogue during cellular self‐assembly. Therefore it naturally follows that temporally‐related spatial nesting of growth fields occurs during ontogeny. Local allometric changes, as well as major morphological “leaps”; may be explained by such alterations. Following a fossil example of hierarchical heterochronic change, a nomenclatural classification is presented along with branching tree models to illustrate the processes.

Echinoids in biostratigraphy and paleoenvironmental reconstruction; a cluster analysis from the Eocene Gulf Coast (Ocala Limestone)

Cluster analysis of 31 echinoid species from the Late Eocene of the Gulf Coast area delineates 5 major stratigraphicecologic associations: an early assemblage containing a clypeasteroidprominent fauna of shallow-water, near-shore species; two later offshore, spatangoid-prominent associations; a transitional assemblage between these early and later ones; and a general assemblage containing broad-ranging species. The utility of echinoids as biostratigraphic and paleoenvironmental indicators is illustrated and discussed.

EOCENE ECHINOIDS OF TEXAS

Abstract Fourteen species of echinoids ranging in age from early to late Eocene, including four new species, are described from Texas. New taxa include Schizaster (Schizaster) caddoensis from the Reklaw and Weches Formations (Claiborne Group, middle Eocene), Schizaster (Schizaster) stenzeli and Eupatagus texanus from the Weches Formation, and Schizaster (Paraster) susana from the Caddell Formation (Jackson Group, upper Eocene). Fibularia meyeri (Aldrich, 1921) and Fibularia alabamensis Cooke, 1959 are synonymized with Fibularia texana (Twitchell, 1915) from the Weches and Cook Mountain Formations (Claiborne Group, middle Eocene). Other reported species are Linthia hollandi Barry, 1942, from the Sabinetown Formation (Wilcox Group, lower Eocene); Gagaria sp., Protoscutella tuomeyi (Twitchell, 1915), Protoscutella mississippiensis mississippiensis (Twitchell, 1915), Maretia arguta (Clark, 1915), and Linthia? sp. from the Weches Formation; Spatangus? sp. and Eupatagus carolinensis? Clark, 1915 from the Cook Mountain Formation, and Periarchus lyelli (Conrad, 1834) from the Cook Mountain and Caddell Formations. These echinoids are sensitive indicators of depositional environment, in particular their distribution serves as a marker for stenohaline (open marine) environments and illustrates the biogeographic variability along the northeast Texas coast during the Eocene.

Insights into The Ecology, Genetics and Distribution of Lucanus Elaphus Fabricius (Coleoptera: Lucanidae), North America's Giant Stag Beetle

Little is known about the biology or conservation status of Lucanus elaphus Fabricius in North America despite well‐documented declines of a related species, Lucanus cervus (L.), in Europe. This study provides information critical to developing conservation plans for L. elaphus including the species’ larval substrate requirements, genetic data and range‐wide estimates of habitat suitability. In Mississippi floodplain forests, larval L. elaphus were recovered from a wide range of log sizes and rot types and were either found tunnelling within the wood or feeding beneath logs at the soil–wood interface. The species appears to require 1–2 years to complete development, exhibits a 1:1 sex ratio and is parasitised by Zelia vertebrata (Say) (Diptera: Tachinidae). Flight intercept traps placed at three heights at both the edge and interior of hardwood‐dominated forests in Georgia yielded six adult male L. elaphus, all of which were captured in traps placed at 15 m on the forest edge. Because L. elaphus larvae are morphologically indistinguishable from related species, DNA sequence data from the mitochondrial cytochrome oxidase I gene were generated to facilitate molecular identification. Genetic data revealed modest intra‐specific variation, with up to 1.3% sequence divergence among haplotypes sampled from the same forest. Based on assembled occurrence records, ecological niche models suggest that environmental conditions are suitable for L. elaphus across much of the southeastern United States, provided that adequate lowland forest cover and dead wood substrates are available.

Occurrence of the spatangid echinoid Maretia arguta (Clark) in the middle Eocene of Texas

Echinoid fragments were reported by Zachos (1990) from a Weches Formation (Clairborne) outcrop on Hooker Creek in Burleson County, Texas. Enough fragments have been found at the latter locality to piece together a composite identifiable as a species of the spatangid genus Maretia , most likely M. arguta. This species has not previously been reported outside of Clarke County, Mississippi. A search of the stratigraphic collections of the Texas Memorial Museum in Austin, Texas, has uncovered several previously unidentified specimens of M. arguta from two Weches localities, at Kickapoo Shoals on the Trinity River in Houston County and at Nacogdoches in Nacogdoches County. In addition, spatangoid fragments, some of which are attributable to M. arguta , are common in collections from the Weches and Cook Mountain Formations.

Comparative morphology and phylogenetic significance of Gregory’s diverticulum in sand dollars (Echinoidea: Clypeasteroida)

Several derived sand dollar (Echinoidea: Clypeasteroida) families are characterized by the presence of Gregory’s diverticulum, an accessory organ of the digestive tract. This soft tissue structure is composed of a central tubular cecum that gives off multiple lobes into the periphery of the test. Most notable are the organ’s capacity to selectively store sand grains that the animal has taken up from the surrounding sediment as well as the gradual reduction of Gregory’s diverticulum during ontogeny. Several aspects of the biology of this structure have remained unexplored, including the organ’s precise morphology and structural diversity. In order to provide a concise basis for future histological, physiological, and functional analyses, a comprehensive comparative morphological and phylogenetic study across numerous taxa was undertaken. Taxon sampling comprised over 100 clypeasteroid species, including various fossil taxa. This extensive dataset permits establishing a concise terminology that incorporates all of the organ’s substructures. In addition, three-dimensional models of Gregory’s diverticulum are presented that provide an improved spatial understanding of the organ’s morphology in situ. The combined data from dissection, X-ray imaging, microcomputed tomography, and magnetic resonance imaging reveal a previously unknown variability of the structure, which also yields several phylogenetically informative morphological characters. Among those sand dollar families that possess Gregory’s diverticulum, the organ is present in two distinct shapes, which can be distinguished by the number, shape, and location of substructures. In addition, the data provide unequivocal evidence that Gregory’s diverticulum is absent in the extant taxa Rotulidae and Astriclypeidae, but also in the enigmatic Marginoproctus.

Holistic morphometric analysis of growth of the sand dollar Echinarachnius parma (Echinodermata:Echinoidea:Clypeasteroida)

Holistic morphometrics is a term implying complete shape characterization of all of the structural parts of an organism. The skeleton of an echinoid is comprised of hundreds of individual plates arranged in a closed 3-dimensional mosaic forming the test. GIS software and techniques were used to generate topologically correct digital models of an ontogenetic series of specimens of the sand dollar echinoid Echinarachnius parma. Plate growth can be considered in proportion to overall skeleton growth, resulting in a linear model of relative growth. Alternatively, separate logistic equations can be fit to the ontogenetic series of homologous plate areas using nonlinear least squares regression to result in a model for instantaneous growth. The linear and logistic parameters of the models describe the allometric growth of plates from different viewpoints. Growth is shown to fall into characteristic patterns defining distinct plate growth domains associated with development of the imago (larval) skeleton just prior to metamorphosis, early growth associated with expansion of the corona and fold-over (forming the flattened body form), juvenile growth and formation of petals, and adult growth. Functions of growth, plate translocation, plate juxtaposition between aboral and oral surfaces, and relationships with internal buttressing are quantified. Results offer explanations for general skeletal symmetry, distinction between ambulacral and interambulacral growth, the relationship of growth to internal buttressing, existence of a distinct petalodium, and anterior-posterior asymmetry during development. The parametric values of growth functions derived from the results are a basis for computational modeling of growth and development in sand dollars.