Ontogenetic skull variation in a shovel-headed amphisbaenian species.

Leposternon microcephalum is a species belonging to the Amphisbaenia, a group of burrowing reptiles. Amphisbaenia present various morphological and physiological adaptations that allow them to penetrate the ground and live underground, through a system of galleries and permanent chambers that they build themselves. Among the morphological adaptations in this group, those of the skull stand out as it serves as the main excavation tool. Four basic skull shapes are recognized: rounded, keeled, shovel-shaped, and spade-shaped. The skull of L. microcephalum belongs to this last type, which is considered the most specialized. The species inhabits soils that are highly compacted and difficult to penetrate. Among the species of Leposternon present in South America, L. microcephalum has the widest distribution, being found in all Brazilian biomes and neighboring countries such as Bolivia, Argentina, Paraguay, and Uruguay. The analysis of the skull of this species was carried out using three-dimensional geometric morphometrics (3D-GMM), a technique that allows comparative analysis, through robust statistical methods, of shape and its variations, using Cartesian coordinate data from a configuration of homologous landmarks. The technique allows the size and shape components of a structure to be analyzed separately. From an ontogenetic point of view, this methodology had also been used to investigate variations in Cynisca leucura, a member of the Amphisbaenidae with a rounded head. Our hypothesis is that the patterns of morphological differentiation in the skull, mainly in the intermediate and occipital regions, are similar in different Amphisbaenia species. Therefore, the objective of this study was to analyze cranial morphological variations in an ontogenetic series of L. microcephalum using 3D-GMM. Computed Tomographic scans of 13 specimens were analyzed: juveniles (N = 8) and adults (N = 5), based on 20 landmarks that characterize the skull. Principal components and regression analyses between shape (dependent variable) and size (independent variable) showed a clear difference between the cranial morphological pattern of juvenile individuals and that of adults. For instance, young specimens tend to have a dorsoventrally tall neurocranium, with the tip of the snout more anteriorly oriented and its dorsal border subtly curved. Dorsally, the parietal region is thicker and smoothly dome-shaped in juveniles. As in C. leucura, the variation was strongly correlated with the size change from juvenile to adult, indicating a dominant role for ontogenetic allometry in determining skull shape.

Unveiling the role of bioturbation on bacterial activity in metal-contaminated sediments.

The processes permeating the relationships between bioturbation and microorganisms remain poorly understood due to the difficulty of traditional techniques in quantifying their two- and three-dimensional aspects. We used cutting-edge technologies to address the macro- and microorganisms' interactions under metal-contamination. Bioturbation (mucus-lined gallery perimeter, mucus-lined gallery surface area, and gallery water volume) positively influence the carbohydrate consumption rate by the bacterial consortium, elevating bacterial metabolic activity, despite metal-contamination. Synchrotron-based 2D-µXRF revealed that the mucous lining by marine worm during bioturbation as the primary carbon source enhances metal immobilization by bacterial biofilm, improving the bacterial metabolic activity. Bioturbation thus can positively affect bacterial consortium that can use the mucus as a carbon source, which enhances the resistance to metals through biofilm formation in metal-contaminated sediments.

Osteoderm microstructure of Riostegotherium yanei, the oldest Xenarthra.

Abstract: Riostegotherium yanei from the Itaboraí Basin, Brazil, is the oldest known Xenarthra. This paper aims to describe the internal morphology of the osteoderms of Riostegotherium yanei from the perspective of histology and micro-CT approaches, expanding the available data on cingulate osteoderm microstructure. Seven osteoderms of R. yanei were used for the internal microstructure description and eight of Dasypus novemcinctus for comparison. The osteoderms of Riostegotherium yanei lacks the diploë-like structure typical of glyptodonts but has a three-layered structure composed of two layers of non-Haversian compact bone enclosing a central layer of primary and secondary osteons. This internal organization is distinct from other Astegotheriini of comparable age, but similar to Dasypus. The 3D reconstruction of Riostegotherium yanei revealed two patterns of internal organization. Pattern 1 of movable osteoderm is composed of large remodeled areas at the base and a more compact bone at the tongue; in Pattern 2 (both movable and buckler), the internal cavities are much smaller, more numerous, and more interconnected to each other. In one buckler osteoderm, the cavities are organized somewhat radially with a compact central region (Pattern 1). Pattern 1 of both movable and buckler osteoderms resemble that of Dasypus.

Characterization of scale deposition in oil pipelines through X-Ray Microfluorescence and X-Ray microtomography.

The formation of scales consists in one of the most relevant problems in the oil prospecting field and occurs when incompatible types of water (injected sea water and formation water) are mixed in the reservoir, unavoidably undergoing chemical interaction followed by mineral precipitation. In this work, scale samples extracted from obstructed oil pipes were characterized through X-Ray Microfluorescence and X-Ray microtomography by analyzing their elemental and structural composition. Different types of scale were found according to their elemental distribution (mainly BaSO4 and CaCO3) and to the way that they were deposited inside the pipes. The results of both techniques provided data that can be used to optimize the prevention and removal methods of such materials from pipes and equipments used in oil facilities.

Monitoring bioturbation by a small marine polychaete using microcomputed tomography.

Bioturbation is one of the principle biological processes involved in transporting particles and solutes within sediments, which contributes to the maintenance of biodiversity. In muddy polluted environments, bioturbation may increase pollutant flux at the water-sediment interface, thereby enhancing contaminant bioavailability. The behavior of organisms dictates bioturbation, and gallery shape influences the magnitude of solute transport. Thus, quantitative investigations of gallery shape are fundamental to understanding how pollutant and solute transport is enhanced by bioturbators in muddy sediments. However, there is a lack of tools for quantitatively analyzing gallery geometry, especially for assessing bioturbation and gallery properties through time. Despite the potential of microcomputed tomography (µCT) for quantitative analyses of bioturbation, few such studies have been carried out. Here, we aimed to investigate the potential of µCT for quantitatively assessing the shape and geometric properties of galleries made by small marine polychaetes and their evolution through time in muddy sediments. We focused on Laeonereis acuta (Treadwell, 1923) (Nereididae, Polychaeta), which is a key bioturbator in marine coastal ecosystems. Using 2D and 3D images generated from µCT, we evaluated L. acuta galleries and propose several indexes to quantitatively assess gallery evolution and the role of gallery parameters in bioturbation. Quantitative investigations of polychaete galleries using µCT can assist in monitoring how bioturbation influences sedimentary systems.

Reassessment of the enigmatic crocodyliform "Goniopholis" paulistanus Roxo, 1936: Historical approach, systematic, and description by new materials.

The Crocodyliformes are the most represented vertebrate clade in the Upper Cretaceous sequences of the Bauru Group, Paraná Basin. However, some of the species described have an uncertain taxonomic status and phylogenetic position. For instance, "Goniopholis" paulistanus has been assigned as a nomem dubium, due to its description being based on scarce material. The "G". paulistanus specimens (i.e. teeth and a left tibia) were discovered in two different localities in São Paulo state: Mirandópolis and Valparaíso municipalities; where the upper interval of the Adamantina Formation (Early Maastrichtian of Bauru Group) crops out. Revisiting these specimens, we observed multicrenulated teeth in middle dentary toot- row, a remarkable feature only shared with teleosaurids Machimosaurus hugii (Upper Jurassic of Laurasia) and M. rex (Lower Cretaceous of Tunisia). This apomorphy was also recognized in new material from the Alfredo Marcondes municipality (Presidente Prudente Formation), which are here also referred to "G". paulistanus. We recognized the teeth of "G." paulistanus as the lectotype, however the tibia cannot be assigned to a species as it was not collected in association with the teeth. We performed a phylogenetic analysis with a data matrix composed of 388 characters and 86 taxa, analyzed in TNT. The strict consensus tree recovered Neosuchia and Ziphosuchia (Notosuchia + Sebecia) within Mesoeucrocodylia. The species "G" paulistanus is valid, as a distinct and new genus within Sebecia, in a polytomy with Barreirosuchus, Pepesuchus, Itasuchus and Peirosaurus, forming the clade Itasuchidae. Stolokrosuchus is the sister taxon to Itasuchidae, the sister group of all other Sebecia (Peirosauridae (Mahajangasuchidae + Sebecidae and taxa affinis)). The clades Ziphosuchia, Sebecia and Itasuchidae are here redefined, and we find the last two clades to be more closely related to terrestrial notosuchids than to semiaquatic neosuchians.