Current State, Needs, and Opportunities for Wearable Robots in Military Medical Rehabilitation and Force Protection.

Despite advances in wearable robots across various fields, there is no consensus definition or design framework for the application of this technology in rehabilitation or musculoskeletal (MSK) injury prevention. This paper aims to define wearable robots and explore their applications and challenges for military rehabilitation and force protection for MSK injury prevention. We conducted a modified Delphi method, including a steering group and 14 panelists with 10+ years of expertise in wearable robots. Panelists presented current wearable robots currently in use or in development for rehabilitation or assistance use in the military workforce and healthcare. The steering group and panelists met to obtain a consensus on the wearable robot definition applicable for rehabilitation or primary injury prevention. Panelists unanimously agreed that wearable robots can be grouped into three main applications, as follows: (1) primary and secondary MSK injury prevention, (2) enhancement of military activities and tasks, and (3) rehabilitation and reintegration. Each application was presented within the context of its target population and state-of-the-art technology currently in use or under development. Capturing expert opinions, this study defines wearable robots for military rehabilitation and MSK injury prevention, identifies health outcomes and assessment tools, and outlines design requirements for future advancements.

Perceptions and assessment of a novel robotic wheelchair transfer system.

OBJECTIVES: Wheelchair transfers risk injury to users and caregivers. Conventional transfer devices are injury-prone and time inefficient. The Powered Personal Transfer System (PPTS), utilizing a modified Electric Powered Wheelchair (EPW) and a hospital bed, provides a no-lift solution for bed-to-wheelchair transfers. Objective 1: Assess PPTS workload compared to existing methods. Objective 2: Evaluate PPTS EPW in daily mobility tasks. Objective 3: Perform Rehabilitation Engineering and Assistive Technology Society of North America (RESNA) wheelchair standards testing for PPTS EPW stability and performance. METHODS: Fifteen professional and family caregivers, experienced in assisting EPW users, performed transfers between the bed and EPW using the PPTS. Subsequently, participants drove the PPTS EPW providing ratings on the ease of performing mobility tasks. Wheelchair testing was conducted following RESNA standards. SETTING: : Simulated bedroom in a laboratory setting. RESULTS: Participants reported low workload demands for employing the PPTS and indicated a preference for the PPTS over existing transfer devices/methods. Ease of performing everyday mobility tasks was not significantly different between the modified PPTS and the commercially available original manufacturer equipment EPW (p > 0.05). RESNA wheelchair standards testing confirmed that the PPTS EPW preserves functionality, stability and performance when compared to similar commercially available EPWs. CONCLUSION: The PPTS demonstrated promise in offering a practical, low demanding, and safe solution for transfers. It has the potential to enhance user and caregiver safety by reducing the incidence of caregiver injuries associated with assisting in transfer tasks. In addition to its efficiency and ease of use, it is an advancement in assistive technology for wheelchair transfers.

Evolution, development, and regeneration of tooth-like epithelial appendages in sharks.

Sharks and their relatives are typically covered in highly specialized epithelial appendages embedded in the skin called dermal denticles; ancient tooth-like units (odontodes) composed of dentine and enamel-like tissues. These 'skin teeth' are remarkably similar to oral teeth of vertebrates and share comparable morphological and genetic signatures. Here we review the histological and morphological data from embryonic sharks to uncover characters that unite all tooth-like elements (odontodes), including teeth and skin denticles in sharks. In addition, we review the differences between the skin and oral odontodes that reflect their varied capacity for renewal. Our observations have begun to decipher the developmental and genetic shifts that separate these seemingly similar dental units, including elements of the regenerative nature in both oral teeth and the emerging skin denticles from the small-spotted catshark (Scyliorhinus canicula) and other chondrichthyan models. Ultimately, we ask what defines a tooth at both the molecular and morphological level. These insights aim to help us understand how nature makes, replaces and evolves a vast array of odontodes.

On the Move pad - a portable multipurpose pad: User feedback.

CONTEXT/OBJECTIVE: Hard-shell toilet seats may compromise safety and hinder the participation of individuals at risk for pressure injuries (PIs) when using these facilities away from home in public, hotel, or family/friend restrooms. Moreover, people often add "wash-cloths" for additional padding for comfort, and to reduce the risk of PIs due to pressure or shearing on their wheelchairs surfaces. This study investigated the utilization of portable pads, initially designed for toilet use but adaptable to various places and contexts, while examining pad usability. DESIGN: A cross-sectional descriptive survey design. SETTING: Inpatient care, outpatient care, and community setting. PARTICIPANTS: 45 individuals at risk of PIs. RESULTS: Participants extended the use of these pads beyond toilets, employing them as wheelchair armrest and leg rest pads in other settings. Feedback from a customized questionnaire indicated high levels of usefulness (8.5/10) and ease of use (9.1/10) attributed to the pads. Among the features, the top three favored were ease of use, comfort/cushioning, and function. Participants expressed a desire for a variety of sizes and colors to enable versatile usage and suggested incorporating a pocket for storing small items. CONCLUSIONS AND RELEVANCE: Individuals at risk of PIs require cushioning not only on hard-shell toilet seats, but also for additional padding, protection and enhancing the use of wheelchairs. Rehabilitation professionals can play a crucial role in educating and training both clients and caregivers to understand PI prevention, enabling them to effectively leverage the pads in appropriate situations, thereby enhancing their comfort in their wheelchairs during social engagement.

Accessible Autonomous Transportation and Services: Design Considerations From the Perspective of Consumers and Providers.

OBJECTIVE: To understand the priorities and preferences of people with disabilities (PwDs) and older adults regarding accessible autonomous vehicles (AVs) to address existing transportation barriers. DESIGN: Two national surveys, Voice of the Consumer and Voice of the Provider, were conducted to gather feedback from accessible AV consumers and providers, respectively, in the United States. SETTING: This U.S.-based study focused on PwDs and older adults who may face transportation challenges and those who provide or design AV solutions. PARTICIPANTS: The 922 consumers and 45 providers in the surveys encompassed a diverse range of disability types, caregiver roles, and age groups (N = 967). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: The main outcomes were consumer usage needs and provider preferences for features in accessible autonomous transportation. Patterns in usage needs and feature preferences through 2-step clustering algorithm were applied subsequent to the descriptive analysis of participant demographics and their responses. RESULTS: Participants strongly preferred AV features enhancing personal transportation, especially for rural medical appointments. Most sought comprehensive AV automated features. Wheelchair users emphasized accessible entrances, particularly for lower-income brackets ($25,000-$49,000). Provider priorities closely aligned with consumer preferences, reinforcing content validity. CONCLUSIONS: The study highlights the importance of prioritizing wheelchair accessibility in AVs and improving access to medical appointments, especially in rural and low-income communities. Implications include developing inclusive AV services for PwDs and underserved populations. The research establishes a foundation for a more equitable and accessible transportation landscape through AV technology integration.

The actin cytoskeleton plays multiple roles in structural colour formation in butterfly wing scales.

Vivid structural colours in butterflies are caused by photonic nanostructures scattering light. Structural colours evolved for numerous biological signalling functions and have important technological applications. Optically, such structures are well understood, however insight into their development in vivo remains scarce. We show that actin is intimately involved in structural colour formation in butterfly wing scales. Using comparisons between iridescent (structurally coloured) and non-iridescent scales in adult and developing H. sara, we show that iridescent scales have more densely packed actin bundles leading to an increased density of reflective ridges. Super-resolution microscopy across three distantly related butterfly species reveals that actin is repeatedly re-arranged during scale development and crucially when the optical nanostructures are forming. Furthermore, actin perturbation experiments at these later developmental stages resulted in near total loss of structural colour in H. sara. Overall, this shows that actin plays a vital and direct templating role during structural colour formation in butterfly scales, providing ridge patterning mechanisms that are likely universal across lepidoptera.

Discovering Provider Awareness of Mobility Assistive Technologies and Clinical Guidelines-A Comparative Analysis With Consumer Responses.

OBJECTIVE: This study aims to enhance the accessibility and quality of mobility-assistive technology by investigating and bridging knowledge gaps between mobility-assistive technology providers and consumers with ambulatory limitations. DESIGN: A survey was conducted among mobility-assistive technology providers in the United States, consisting of sections on awareness, knowledge importance and desire, and knowledge sources. The responses were compared to data collected from consumers in a previous study. RESULTS: A total of 144 mobility-assistive technology providers participated, with 60% having received academic or professional training in relevant fields. Analysis revealed significant knowledge gaps between providers and consumers, particularly in assistive technology assessment tools and knowledge sources. Moderate gaps were also observed in areas such as clinical practice guidelines, desired mobility-assistive technology information, and knowledge sources. However, the gaps in other areas were relatively small. CONCLUSIONS: This study highlights the knowledge gaps between mobility-assistive technology providers and consumers, hindering the optimal utilization and fulfillment of user needs. Providers possess valuable information that consumers may lack, positioning them as primary knowledge sources. Addressing these gaps through targeted interventions, improved communication channels, and enhanced education can enhance the utilization of mobility-assistive technology and improve outcomes for individuals with ambulatory limitations.

Development and content validity of the caregiver assisted transfer technique instrument.

Informal caregivers often provide transfer assistance to individuals with disabilities; however, repeated transfers are associated with a high risk of musculoskeletal pain and injury, and training and education around transfers is minimal. The purpose of this study was to develop and assess the content validity of a new tool, the Caregiver Assisted Transfer Technique Instrument (CATT), which could be used to provide an objective indicator of transfer performance. Item importance, clarity, and appropriateness of responses were rated on a five-point Likert scale by clinicians (n = 15), informal caregivers (n = 10), and individuals with spinal cord injury (n = 5). The content validity index and modified Kappa of each item was calculated. Participants also provided qualitative feedback on item content. In general, items were rated favorably for their importance (4.47 to 5.00), clarity (4.33 to 4.90), and appropriateness of responses (4.38 to 4.90), and most items had excellent content validity (k* ≥ 0.75). Feedback from participants led to the creation of two versions of the CATT: one for manual lifting techniques (CATT-M) and one for transfers performed via lift-based technologies (CATT-L). Future work will focus on establishing the reliability and validity of the CATT as well as developing training and education interventions surrounding assisted transfers.

Exploring Control Authority Preferences in Robotic Arm Assistance for Power Wheelchair Users.

This paper uses mixed methods to explore the preliminary design of control authority preferences for an Assistive Robotic Manipulator (ARM). To familiarize users with an intelligent robotic arm, we perform two kitchen task iterations: one with user-initiated software autonomy (predefined autonomous actions) and one with manual control. Then, we introduce a third scenario, enabling users to choose between manual control and system delegation throughout the task. Results showed that, while manually switching modes and controlling the arm via joystick had a higher mental workload, participants still preferred full joystick control. Thematic analysis indicates manual control offered greater freedom and sense of accomplishment. Participants reacted positively to the idea of an interactive assistive system. Users did not want to ask the system to only assist, by taking over for certain actions, but also asked for situational feedback (e.g., 'How close am I (the gripper)?', 'Is the lid centered over the jug?'). This speaks to a future assistive system that ensures the user feels like they drive the system for the entirety of the task and provides action collaboration in addition to more granular situational awareness feedback.

Evaluation of Electric and Air-Powered Shopping Scooters in Grocery Stores.

OBJECTIVE: The purpose of this study was to further previous research and gather additional information regarding the usage of motorized shopping scooters as well as feedback for improvements to an air-powered scooter. METHODS: Online surveys were used to assess individuals' shopping characteristics and experience using the motorized scooters and to gather feedback from store employees regarding their experience. K-Means clustering analysis was used to determine user demographics who chose to use the air-powered scooter versus the electric-powered scooter while shopping. RESULTS: A total of 127 individuals provided informed consent, 65 individuals from site 1 and 62 individuals from site 2. One hundred twenty participants met the inclusion criteria and completed the survey. K-Means clustering found that age, type of personal mobility device, shopping bill total, and frequency using a motorized shopping scooter to be significant factors in whether individuals chose to use an air-powered scooter or electric-powered scooter. CONCLUSIONS: Motorized shopping scooters are in high demand and used by a wide variety of individuals, yet electric-powered scooters are commonly unavailable because of having dead batteries or all the devices being in use. Air-powered scooters may serve as a practical replacement for the current electric-powered scooters found in grocery and retail stores.

Test-Retest Reliability of the Electronic Instrumental activities of daily living Satisfaction Assessment (EISA): A Cohort Study.

IMPORTANCE: Currently, no self-report instruments exist for assessing satisfaction with performing instrumental activities of daily living and occupations for people with disabilities using internet-connected assistive devices like accessible smartphones, tablets, laptops, and apps. OBJECTIVE: To assess the test-retest reliability and internal consistency of the Electronic Instrumental activities of daily living Satisfaction Assessment (EISA) self-report outcome tool. DESIGN: Repeated-measures cohort study with a time frame of 7 to 21 days. SETTING: Multicity online recruitment at assistive technology clinics, nongovernmental organizations, advocacy and peer support groups for people with disabilities, and higher education institutions. PARTICIPANTS: Eighty-four participants with disabilities, age 18 yr or older, with a mean age of 43.3 yr (range = 19-75 yr), and 57% female. INTERVENTION: Not applicable. OUTCOMES AND MEASURES: The a priori study hypotheses were that the EISA test-retest reliability scores would be above the minimum acceptable level (Rs > .80) and that internal consistency would be good (Cronbach's α = .70-.90). RESULTS: On the basis of the study data, the EISA, Version 1.0, demonstrated good test-retest reliability (Rs = .81) and excellent internal consistency (Cronbach's α = .88). CONCLUSIONS AND RELEVANCE: The results of the test-retest reliability and internal consistency analyses provide good support for the EISA to be used in clinical settings. What This Article Adds: This article documents the reliability and internal consistency of, to our knowledge, the first-ever self-report instrument for assessing satisfaction with performance of everyday occupations for people with disabilities using internet-connected assistive devices such as smartphones, tablets, laptops, and apps.

Accessible autonomous transportation and services: voice of the consumer - understanding end-user priorities.

PURPOSE: This study aimed to explore the requirements for accessible Autonomous Vehicles (AVs) and AV services from a consumer perspective, focusing on people with disabilities (PwDs) and older adults. METHODS: Two national surveys were conducted, capturing current transportation trends and AV priorities. Participants (n = 922) with disabilities and older adults were included in the analysis. RESULTS: Transportation choices exhibited significant divergence based on the underlying causes of disabilities, showcasing distinct inclinations and impediments within each category. AV services, encompassing family conveyance and package delivery, proved integral, but their specific desirability fluctuated in accordance with the nature of disabilities. Notably, medical appointments emerged as the foremost AV utilisation requirement, particularly pronounced among individuals with hearing impairments. Preferences for orchestrating AV rides and the preferred vehicle types displayed disparities linked to the various disability classifications. The employment of mobile applications, websites, and text messages were preferred mediums for arranging rides. Features such as automated route guidance and collision prevention garnered unanimous precedence among AV attributes. Key priorities, spanning wheelchair accessibility, user profiles, and seamless communication with AVs, were universally emphasised across all participant clusters. The study indicated a moderate comfort level with AV deployment, implying the potential for favourable reception within the population of PwDs and older adults. CONCLUSION: The study highlights the significance of considering diverse needs in accessible AV development of vehicle and infrastructure and policies.

The findings inform evidence-based interventions and programmes that prioritise accessibility needs, promoting social inclusion and equitable transportation solutions.Continued research and advocacy are essential for successful autonomous vehicle integration, catering to the needs of all individuals.

Usability and Vibration Analysis of a Low-Profile Automatic Powered Wheelchair to Motor Vehicle Docking System.

The QLX is a low-profile automatic powered wheelchair docking system (WDS) prototype developed to improve the securement and discomfort of wheelchair users when riding in vehicles. The study evaluates the whole-body vibration effects between the proposed QLX and another WDS (4-point tiedown system) following ISO 2631-1 standards and a systematic usability evaluation. Whole-body vibration analysis was evaluated in wheelchairs using both WDS to dock in a vehicle while riding on real-world surfaces. Also, participants rated the usability of each WDS while driving a wheelchair and while riding in a vehicle in driving tasks. Both WDSs showed similar vibration results within the vibration health-risk margins; but shock values below health-risk margins. Fifteen powered wheelchair users reported low task load demand to operate both WDS; but better performance to dock in vehicles with the QLX (p = 0.03). Also, the QLX showed better usability (p < 0.01), less discomfort (p's < 0.05), and greater security compared to the 4-point tiedown while riding in a vehicle (p's < 0.05). Study findings indicate that both WDS maintain low shock exposure for wheelchair users while riding vehicles, but a better performance overall to operate the QLX compared to the 4-point tiedown system; hence enhancing user's autonomy to dock in vehicles independently.

Accessible autonomous transportation and services: a focus group study.

PURPOSE: Existing automated vehicle transportation guidelines and regulations have minimal guidance to address the specific needs of people with disabilities. Accessibility should be at the forefront to increase autonomy and independence for people with disabilities. The purpose of this research is to better understand potential facilitators and barriers to using accessible autonomous transportation. METHODS: Focus groups were conducted with key stakeholders derived from people with disabilities (n = 5), travel companions/caregivers (n = 5), and transportation experts or designers (n = 11). RESULTS: The themes include describing stakeholder perceptions across all three groups by identified themes: autonomous vehicle assistive technology, autonomy vs automation, cost, infrastructure, safety & liability, design challenges, and potential impact. CONCLUSION: Specific gaps and needs were identified regarding barriers and facilitators for transportation accessibility and evidence-based guidance. These specific gaps can help to formulate design criteria for the communication between, the interior and exterior of accessible autonomous vehicles.

Accessible and affordable autonomous transportation may increase mobility and the autonomy of people with disabilities to travel spontaneously.Autonomous vehicles and services should be designed to accommodate various types of disabilities such as multimodal and multilingual device communication.Safety and liability regulatory protocols need to be developed for incidents and emergencies.Wheelchair user, especially people who use powered devices, would need systems for ingress/egress, docking, and occupant restraints.

Participatory Action Design and Engineering of Powered Personal Transfer System for Wheelchair Users: Initial Design and Assessment.

Caregivers that assist with wheelchair transfers are susceptible to back pain and occupational injuries. The study describes a prototype of the powered personal transfer system (PPTS) consisting of a novel powered hospital bed and a customized Medicare Group 2 electric powered wheelchair (EPW) working together to provide a no-lift solution for transfers. The study follows a participatory action design and engineering (PADE) process and describes the design, kinematics, and control system of the PPTS and end-users' perception to provide qualitative guidance and feedback about the PPTS. Thirty-six participants (wheelchair users (n = 18) and caregivers (n = 18)) included in the focus groups reported an overall positive impression of the system. Caregivers reported that the PPTS would reduce the risk of injuries and make transfers easier. Feedback revealed limitations and unmet needs of mobility device users, including a lack of power seat functions in the Group-2 wheelchair, a need for no-caregiver assistance/capability for independent transfers, and a need for a more ergonomic touchscreen. These limitations may be mitigated with design modifications in future prototypes. The PPTS is a promising robotic transfer system that may aid in the higher independence of powered wheelchair users and provide a safer solution for transfers.

Evaluation of Power Wheelchair Dynamic Suspensions for Tip Prevention in Non-ADA Compliant Surfaces.

OBJECTIVE: To evaluate the driving performance and usability of a mobility enhancement robot (MEBot) wheelchair with 2 innovative dynamic suspensions compared with commercial electric powered wheelchair (EPW) suspensions on non-American with Disabilities Act (ADA) compliant surfaces. The 2 dynamic suspensions used pneumatic actuators (PA) and electro-hydraulic with springs in series electrohydraulic and spring in series (EHAS). DESIGN: Within-subjects cross-sectional study. Driving performance and usability were evaluated using quantitative measures and standardized tools, respectively. SETTING: Laboratory settings that simulated common EPW outdoor driving tasks. PARTICIPANTS: 10 EPW users (5 women, 5 men) with an average age of 53.9±11.5 years and 21.2±16.3 years of EPW driving experience (N=10). INTERVENTION: Not applicable. MAIN OUTCOME MEASURE(S): Seat angle peaks (stability), number of completed trials (effectiveness), Quebec User Evaluation of Satisfaction with Assistive Technology (QUEST), and systemic usability scale (SUS). RESULTS: MEBot with dynamic suspensions demonstrated significantly better stability (all P<.001) than EPW passive suspensions on non-ADA-compliant surfaces by reducing seat angle changes (safety). Also, MEBot with EHAS suspension significantly completed more trials over potholes compared with MEBot with PA suspension (P<.001) and EPW suspensions (P<.001). MEBot with EHAS had significantly better scores in terms of ease of adjustment (P=.016), durability (P=.031), and usability (P=.032) compared with MEBot with PA suspension on all surfaces. Physical assistance was required to navigate over potholes using MEBot with PA suspension and EPW suspensions. Also, participants reported similar responses regarding ease of use and satisfaction toward MEBot with EHAS suspension and EPW suspensions. CONCLUSIONS: MEBot with dynamic suspensions improve safety and stability when navigating non-ADA-compliant surfaces compared with commercial EPW passive suspensions. Findings indicate MEBot readiness for further evaluation in real-world environments.

Changes to physical activity behavior during the COVID-19 pandemic and their associated factors: a cross sectional survey of Mexican women.

BACKGROUND: On March 24, 2020, the Mexican Government established social distancing measures to address the outbreak of the COVID-19 pandemic. The resulting home confinement affected daily lifestyle habits such as eating, sleeping, and physical activity (PA). The objectives of this study were to determine changes in PA behaviors among Mexican women due to the COVID-19 pandemic and to assess potential factors associated with these changes. METHODS: This was a cross-sectional study based on an anonymous online questionnaire developed by the Task Force on Physical Activity for Persons with Disabilities (PAPD) within the International Society of Physical and Rehabilitation Medicine (ISPRM). Descriptive, quantitative statistics were used for data analysis. A Chi-squared (χ²) test was used to explore associations between dependent and independent variables. RESULTS: A total of 1882 surveys were completed. Among the respondents, 53.3% declared that their PA was reduced during the pandemic, 26.6% reported similar PA behavior, and 20.1% declared that their PA had increased during the pandemic. Lower PA behavior during the pandemic was associated with lower education levels, stricter pandemic constraints, obesity, and lower self-perceived functioning levels. A statistically significant association between poorer self-perceived mental health and decreased PA behaviors was also found. Respondents who were younger, self-perceived as unimpaired, not overweight, and whose income was not impacted by COVID-19 were associated with higher levels of reported physical and mental health. CONCLUSIONS: The study results identify disparities experienced in PA behavior during the COVID-19 pandemic among Mexican women and highlights the need for social support for PA participation.

Transient agonism of the sonic hedgehog pathway triggers a permanent transition of skin appendage fate in the chicken embryo.

Vertebrate skin appendage early development is mediated by conserved molecular signaling composing a dynamical reaction-diffusion-like system. Variations to such systems contribute to the remarkable diversity of skin appendage forms within and among species. Here, we demonstrate that stage-specific transient agonism of sonic hedgehog (Shh) pathway signaling in chicken triggers a complete and permanent transition from reticulate scales to feathers on the ventral surfaces of the foot and digits. Resulting ectopic feathers are developmentally comparable to feathers adorning the body, with down-type feathers transitioning into regenerative, bilaterally symmetric contour feathers in adult chickens. Crucially, this spectacular transition of skin appendage fate (from nodular reticulate scales to bona fide adult feathers) does not require sustained treatment. Our RNA sequencing analyses confirm that smoothened agonist treatment specifically promotes the expression of key Shh pathway-associated genes. These results indicate that variations in Shh pathway signaling likely contribute to the natural diversity and regionalization of avian integumentary appendages.

Protocol for the rapid intravenous in ovo injection of developing amniote embryos.

We present a technique for precise drug delivery into the vascular system of developing amniote embryos via injection into chorioallantoic veins underlying the eggshell membrane. We describe steps for incubating and candling eggs, removing the shell to expose underlying veins, and precise intravenous injection. In addition to chicken embryos, this protocol is applicable to other amniote species that lay hard-shell eggs, including crocodiles and tortoises. This technique is rapid, is reproducible, is of low cost, and will provide an important resource for developmental biologists. For complete details on the use and execution of this protocol, please refer to Cooper & Milinkovitch.1.

Teeth outside the mouth: The evolution and development of shark denticles.

Vertebrate skin appendages are incredibly diverse. This diversity, which includes structures such as scales, feathers, and hair, likely evolved from a shared anatomical placode, suggesting broad conservation of the early development of these organs. Some of the earliest known skin appendages are dentine and enamel-rich tooth-like structures, collectively known as odontodes. These appendages evolved over 450 million years ago. Elasmobranchs (sharks, skates, and rays) have retained these ancient skin appendages in the form of both dermal denticles (scales) and oral teeth. Despite our knowledge of denticle function in adult sharks, our understanding of their development and morphogenesis is less advanced. Even though denticles in sharks appear structurally similar to oral teeth, there has been limited data directly comparing the molecular development of these distinct elements. Here, we chart the development of denticles in the embryonic small-spotted catshark (Scyliorhinus canicula) and characterize the expression of conserved genes known to mediate dental development. We find that shark denticle development shares a vast gene expression signature with developing teeth. However, denticles have restricted regenerative potential, as they lack a sox2+ stem cell niche associated with the maintenance of a dental lamina, an essential requirement for continuous tooth replacement. We compare developing denticles to other skin appendages, including both sensory skin appendages and avian feathers. This reveals that denticles are not only tooth-like in structure, but that they also share an ancient developmental gene set that is likely common to all epidermal appendages.