Investigation of a bone lesion in a gorgonopsian (Synapsida) from the Permian of Zambia and periosteal reactions in fossil non-mammalian tetrapods.

While only distantly related to mammals, the anatomy of Permian gorgonopsians has shed light on the functional biology of non-mammalian synapsids and on the origins of iconic 'mammal-like' anatomical traits. However, little is known of gorgonopsian behaviour or physiology, which would aid in reconstructing the paleobiological context in which familiar mammalian features arose. Using multi-modal imaging, we report a discrete osseous lesion in the forelimb of a late Permian-aged gorgonopsian synapsid, recording reactive periosteal bone deposition and providing insights into the origins and diversity of skeletal healing responses in premammalian synapsids. We suggest that the localized lesion on the anterolateral (preaxial) shaft of the left radius represents acute periostitis and, conservatively, most likely developed as a subperiosteal haematoma with subsequent bone deposition and limited internal remodelling. The site records an inner zone of reactive cortical bone forming irregular to radial bony spicules and an outer, denser zone of slowed subperiosteal bone apposition, all of which likely occurred within a single growing season. In surveys of modern reptiles-crocodylians, varanids-such haematomas are rare compared to other documented osteopathologies. The extent and rapidity of the healing response is reminiscent of mammalian and dinosaurian bone pathologies, and may indicate differing behaviour or bone physiology compared to non-dinosaurian reptiles. This report adds to a growing list of putative disease entities recognized in early synapsids and broadens comparative baselines for pathologies and the evolution of bone response to disease in mammalian forebears. This article is part of the theme issue 'Vertebrate palaeophysiology'.

Visual Narrative and Jargon Minimization Underpin Anatomy Teaching to Animation/VFX Industry Professionals and Health Professions Students.

Whether diagrammatic or deeply detailed, most anatomical illustration adheres to established archetypes-identical views of similar dissections, exhibiting neither variability nor originality. These conventional views are replicated from one generation of anatomy textbooks, atlases, and now digital sources, with little modification or reference to original dissection. In this paper, I argue that more effective communication in the field of anatomy requires rethinking conventional anatomical images and avoiding over-reliance on anatomic terminology. The ubiquity and emphasis on the image in the emerging digital learning ecosystem challenges science educators to revisit their use of the conventional visuals. The tools of narrative creating engaging science communication can also be used in constructing better images. After brief review of the role of anatomical jargon and its discontents, I present several examples of "readable" images. These examples have been refined in the course of communicating detailed anatomy and movement for two decades to medical and other health professions students, as well as to character designers, modelers, riggers, and animators in the animation and gaming industries. That "reading an image" promotes understanding without jargon is both anecdotally self-evident and yet scientifically largely untested. Rather than subsisting on images of convenience, the intersection of narrative tools and anatomical imagery provides the opportunity to structure images with intentionality and ultimately evaluate their impact. Such key images and their stories will ultimately require testing to validate the extensive anecdotal evidence that visual stories promote learning.

Comparative anatomy and osteohistology of hyperelongate neural spines in the sphenacodontids Sphenacodon and Dimetrodon (Amniota: Synapsida).

Osteohistological investigations of hyperelongate vertebral spinous processes (neural spines) are presented to elucidate previously unknown aspects of dorsal sail form and function in two, closely related genera of "sail-backed" synapsids: Sphenacodon and Dimetrodon. Although recent and classic surveys of bone histology in extinct vertebrates have sampled the genus Dimetrodon, new sectioning of Sphenacodon material allows a comparative analysis of these structures among Sphenacodontidae for the first time. Variability within the histological organization of the neural spine is assessed by examining multiple regions along its length, and implications for soft tissue correlates, growth and mechanics are considered here. Both genera exhibit extensive parallel-fibered and fibrolamellar bone, in addition to lamellar bone. Several features vary along the length of the spine in each species. Muscle scars and extensive Sharpey's fibers are present at the base of the spine; no scars and fewer fibers are manifested ∼55-60 mm above the zygapophyses in mature individuals. The distal cortex of the spine does not exhibit greater vascularity than the proximal region in either genus. However, both genera manifest distinct vascular grooves of variable size along the distal periosteal surface, some of which become incorporated into the distal cortex. The observed histovariability appears to record the transition from the proximal (epaxial muscle embedded) to the distally protruding portion of the spine. These observations and independent pathological evidence support the existence of a short dorsal crest in Sphenacodon and possibly other basal sphenacodontids. Although the thermoregulatory capacity of such a crest remains uncertain, developmental and mechanical features are readily interpretable and are discussed with respect to the origins and early evolution of the dorsal sail in sphenacodontid synapsids.