Growth, age and size of the Jurassic pachycormid Leedsichthys problematicus (Osteichthyes: Actinopterygii)

The Jurassic pachycormid osteichthyan Leedsichthys problematicus is renowned for having been able to achieve prodigious size for a bony fish. Building on work of MARTILL (1986a), a thorough examination of all known material was conducted in order to constrain estimates of the size of this animal and examine its rate of growth. Important specimens of Leedsichthys are described for the first time. The histology of Leedsichthys is reviewed, and the presence of growth annuli is used to establish ages for five specimens. Age and growth data were obtained from gill rakers (n = 4) and lepidotrichia (n = 2). Lepidotrichia show upward curvilinear growth profiles and ages ranging from 21 to 40 annuli, which are assumed to represent years. Both growth profiles start at a small size (0.26 and 0.33 mm radial distance), which is assumed to represent age 1. However, annuli can be lost near the margins of the elements. Gill rakers exhibit a sigmoidal growth profile. Age of gill rakers was estimated by adjusting the alignment of the inflection points of the growth profiles thereby giving adjusted ages. Gill rakers ranged in age from 19–38 annuli, but all show evidence of reabsorption of annuli near the focal points and at the margins of most elements. Sizes for the five individuals range from 8.0-16.5 m for ages of 19-40 years. Growth rate (0.01-0.05 K) was relatively slow as expected for a large, long-lived fish. At age 1, individuals were 1.6 m in length. Estimates for the length of L. problematicus compare well with published lengths of other large suspension feeders such as those for basking and whale sharks

IMPLEMENTING CONDITION-BASED MAINTENANCE PLUS AS A GROUND MAINTENANCE STRATEGY IN THE MARINE CORPS

In 2020, Marine Corps Order 4151.22 and Commandant White Letter 2–20 was published to implement Condition-Based Maintenance Plus (CBM+) as a ground maintenance strategy to improve operational availability and reduce life-cycle costs. The Fleet Marine Force is still operating under preventative and corrective maintenance strategies instead of CBM+ strategies. Organizational inertia, such as competing priorities, legacy processes, and inspections, has slowed the integration of CBM+ strategies. We reviewed key policy documents and interviewed fifteen subject-matter experts relevant to Marine Corps ground transport maintenance policies and practices. Based on this information, we conducted a thematic analysis using an organizational change approach to identify barriers and opportunities that impact CBM+ implementation. We found that immediate gains from CBM+ implementation in the Marine Corps can be achieved through a focus on people and process improvements while technology integration continues. The CBM+ strategy supports Force Design 2030 and Talent Management 2030 objectives and emphasizing this alignment can build momentum for CBM+. In this paper, we make six specific recommendations that apply organizational change concepts to enable effective CBM+ implementation as a ground maintenance strategy in the Marine Corps.NPS Naval Research ProgramThis project was funded in part by the NPS Naval Research Program.Major, United States Marine CorpsMajor, United States Marine CorpsApproved for public release. Distribution is unlimited

Sawflies (Hymenoptera: Symphyta) of the Parc Natural de s’Albufera de Mallorca

[eng]Eleven sawfly species are recorded from the largest wetland area in the Balearic Islands. Seven of these species are recorded for the first time in the archipelago, with one of them, Janus luteipes, being an addition to the recorded fauna of the Iberian Region.[cat]S’han registrat onze símfits a la zona humida més gran de les Illes Balears. Set d’aquestes espècies han estat primera cita per a l’arxipèlag, essent una d’elles, Janus luteipes, també una addició per a la fauna de la regió Ibèrica

Evolutionary pathways toward gigantism in sharks and rays

Through elasmobranch (sharks and rays) evolutionary history, gigantism evolved multiple times in phylogenetically distant species, some of which are now extinct. Interestingly, the world's largest elasmobranchs display two specializations found never to overlap: filter feeding and mesothermy. The contrasting lifestyles of elasmobranch giants provide an ideal case study to elucidate the evolutionary pathways leading to gigantism in the oceans. Here, we applied a phylogenetic approach to a global dataset of 459 taxa to study the evolution of elasmobranch gigantism. We found that filter feeders and mesotherms deviate from general relationships between trophic level and body size, and exhibit significantly larger sizes than ectothermic‐macropredators. We confirm that filter feeding arose multiple times during the Paleogene, and suggest the possibility of a single origin of mesothermy in the Cretaceous. Together, our results elucidate two main evolutionary pathways that enable gigantism: mesothermic and filter feeding. These pathways were followed by ancestrally large clades and facilitated extreme sizes through specializations for enhancing prey intake. Although a negligible percentage of ectothermic‐macropredators reach gigantic sizes, these species lack such specializations and are correspondingly constrained to the lower limits of gigantism. Importantly, the very adaptive strategies that enabled the evolution of the largest sharks can also confer high extinction susceptibility

Dinosaur egg structure investigated by MRI

<p>In July 1993, the Hunterian Museum of the University of Glasgow was offered a sandstone block with a clutch of intact dinosaur eggs, from Hunan Province, China. Later, a number of single eggs were also acquired.</p> <p>An inter-disciplinary project began to investigate the structure of these eggs. Investigations carried out included egg shell structure analysis, protein analysis, and a program of imaging including CT|, neutron radiography, and MRI.</p> In this poster, the results of imaging the eggs in two commercial high field MRI scanners based at Glasgow hospitals, are presented. The MR scanners are Seimens 1.0 T Impact and 1.5 T Magnetom

Distributed Modeling of Ablation (1996–2011) and Climate Sensitivity on the Glaciers of Taylor Valley, Antarctica

The McMurdo Dry Valleys of Antarctica host the coldest and driest ecosystem on Earth, which is acutely sensitive to the availability of water coming from glacial runoff. We modeled the spatial variability in ablation and assessed climate sensitivity of the glacier ablation zones using 16 years of meteorological and surface mass-balance observations collected in Taylor Valley. Sublimation was the primary form of mass loss over much of the ablation zones, except for near the termini where melt, primarily below the surface, dominated. Microclimates in ~10 m scale topographic basins generated melt rates up to ten times higher than over smooth glacier surfaces. In contrast, the vertical terminal cliffs on the glaciers can have higher or lower melt rates than the horizontal surfaces due to differences in incoming solar radiation. The model systematically underpredicted ablation for the final 5 years studied, possibly due to an increase of windblown sediment. Surface mass-balance sensitivity to temperature was ~−0.02 m w.e. K−1, which is among the smallest magnitudes observed globally. We also identified a high sensitivity to ice albedo, with a decrease of 0.02 having similar effects as a 1 K increase in temperature, and a complex sensitivity to wind speed