Abstract Foraging strategy frequently drives morphological diversification in birds. The plunge‐diving behavior of certain species makes the functional and ecological trade‐offs of variation in cervical vertebrae an especially intriguing question. This study compares cervical vertebrae across five plunge‐diving species and two non‐plunge‐diving species, using morphometric analysis of micro‐CT scans to test whether diving birds share specialized cervical vertebrae morphologies distinct from non‐divers. Plunge‐divers repeatedly experience extreme impact forces during headfirst water entry, requiring the neck to function as a shock‐absorbing spring rather than a flexible manipulative system. To withstand these forces, plunge‐divers exhibit reinforced cervical vertebrae—short, wide vertebrae with expanded joints and thickened arches. These features help distribute compressive and bending loads and reduce stress on the spinal column during impact. Gannets and boobies, the most extreme plunge divers, have an additional articulating surface on the dorsal arch of their anterior cervical vertebrae which limits flexion in the beginning of the neck further reinforcing against high loads. Additionally, we see that all plunge‐diving sulids experience similar water impact durations and that the ratio between the radius of the head and the neck scales with impact velocity.
Abstract The intestinal epithelial barrier is anatomically and functionally distinct and specifically refers to the barrier formed by epithelial cells (enterocytes) and associated junctional complexes (tight junctions, adherens junctions, and desmosomes). The junctional complex is composed of specialized junctional proteins that regulate nutrient permeability across the gut epithelium while preventing passage of antigens, bacteria, and toxins. Modifying the junctional protein expression and disrupting the junctional complex structure result in intestinal hyperpermeability, referred to as “leaky gut.” The leakiness promotes endotoxemia and systemic inflammation, which orchestrate metabolic diseases of multiple organs, notably the liver. Ethanol and its metabolite acetaldehyde, bacterial lipopolysaccharide (LPS), and neutrophil extracellular traps (NETs) deliver a four‐pronged attack disrupting the gut epithelial barrier in alcohol use disorder (AUD). This article reviews the benefits of protecting the gut epithelial barrier structure and function in AUD. Adequate nutritional support is essential for maintaining the barrier integrity and sustaining gut health. Dietary nutrients and biotics supplements are effective in reinforcing the gut epithelial barrier integrity. Accordingly, this article elaborates on the prominent roles of dietary zinc, glutamine, and vitamin D supplementation in modulating the gut barrier junctional protein expression while mitigating the epithelial barrier breakdown induced by ethanol, acetaldehyde, LPS, and NETs. The efficacy of prebiotics, probiotics, and postbiotics in preventing disruption of the gut epithelial barrier in AUD is also reviewed. In summary, dietary nutrients and biotics supplements are beneficial in preserving the gut epithelial barrier integrity in AUD, thereby offering a supportive treatment option for alcohol‐related diseases.
Abstract The ‘Palaeogene strata’ of the Itaboraí Basin (upper Paleocene‐lower Eocene), Southeastern Brazil, has preserved 29 genera and almost 50 species of metatherians (about 65% of its mammalian diversity). Among them, Eobrasilia coutoi Simpson, 1947 is the most enigmatic due to its quite fragmentary nature. We redescribe this species by assigning new molars, first micro‐CT and microwear data, and reinterpreting its systematic affinities. Eobrasilia coutoi weighed about 5.92 kg, thus representing the largest Palaeogene non‐sparassodont metatherian from South America and Antarctica. A phylogenetic analysis recovered Eobrasilia and Periprotodidelphis as sister taxa (Eobrasiliidae rank nov.) within Polydolopimorphia. Lower molars morphofunctional variables (talonid relative area and height, and width by the length of the lower molar) suggest that E. coutoi has a pattern more similar to that of extant New World Primates (Cebidae, Pitheciidae) than extant didelphids. Buccolingually oriented wear facets on the parastyle and postmetacrista suggest a developed ectental masticatory component. Its microwear pattern is characterized by a predominance of fine scratches and small pits, resembling the pattern of callitrichids and cebids but differing from these in having longer scratches. Eobrasilia coutoi was likely a sclerocarpophagous metatherian, being able to exploit unripe fruits and seeds as food; however, it cannot be considered a specialized durophagous/hard‐object feeder like extant pitheciines. The results suggest a Tropical humid ‘mammalian trophic biome’ for the localities in the Itaboraí Basin with Eobrasilia coutoi . This is consistent with an early Eocene age (likely contemporaneous to the Early Eocene Climatic Optimum) inferred for Itaboraí youngest faunal assemblage.
Abstract Cranial bones of squamate reptiles diverge in shape and structure across lineages, while preserving the basic skull plan. Therefore, variation in cranial morphology of squamates is key to understanding phylogenetic relationships, species delimitation, and lifestyles, which ultimately contribute to insights into their evolution and ecology. Nevertheless, although Gymnophthalmidae is the most diverse endemic non‐ophidian squamate family in the Neotropics, studies on comparative cranial osteology within this lineage remain scarce. Herein, we thoroughly describe and compare the external skull anatomy of six species of the Andean genus Riama from Colombia and Ecuador ( R. columbiana , R. simotera , R. striata , and three undescribed taxa), aiming to provide phenotypic evidence for phylogenetic, taxonomic, and functional analyses. We examined 12 cleared‐and‐stained skulls of adult specimens (one male and one female per species) to preliminarily assess inter‐ and intraspecific variation within Riama . Interspecific variation occurs in the degree of contact between nasals (and consequently in the articulation of the nasal process of the premaxilla), and in the absence/presence of the posterior process of the jugal, among others. An anterior process of the ventral crest of the vomer in female R. columbiana is seemingly unique among gymnophthalmids. The number of tooth positions and teeth morphology vary both among sexes and species. Preliminary evidence implies sexual dimorphism and bilateral variation in some characters. Our findings suggest that variation in skull anatomy within Riama can inform species delimitation, and phylogenetic and functional analyses. Finally, we discuss variation in cranial morphology among species of Riama within a phylogenetic context.
Abstract The diversity of the tragulids from the Siwalik Group of the Indian subcontinent is enormous; however, their taxonomy remains unresolved and has been the subject of ongoing debate in recent years. This study aims to resolve some issues by describing the lower deciduous fourth premolars (dp4s) of the genus Afrotragulus , which are described and figured for the first time in the history of paleontology, and the dp4 of the genus Siamotragulus , which is described for the first time from the Siwaliks by ascribing it to this genus. The dp4s of both these genera differ at least in morphological characters such as presence or absence of an interlobular bridge, complete or incomplete M/Σ structure, morphology of first lobe, fossettes, lingual cusps, cristids, ectostylid, cingulids, valleys, and enamel, as well as in crown height, and confirm the presence of the genus Afrotragulus in the Siwaliks. We have also provided a brief overview of the structural aspects of ruminant dp4s and p4s.
