Tetrapods evolved from sarcopterygian fishes in the Devonian and were the first vertebrates to colonize land. The locomotor component of this transition can be divided into four major events: terrestriality, the origins of digited limbs, solid substrate-based locomotion, and alternating gaits that use pelvic appendages as major propulsors. As the sister group to tetrapods, lungfish are a morphologically and phylogenetically relevant sarcopterygian taxon for understanding the order in which these events occurred. We found that a species of African lungfish (Protopterus annectens) uses a range of pelvic fin-driven, tetrapod-like gaits, including walking and bounding, in an aquatic environment, despite having a derived limb endoskeleton and primitively small, muscularly supported pelvis. Surprisingly, given these morphological traits, P. annectens also lifts its body clear of the substrate using its pelvic fins, an ability thought to be a tetrapod innovation. Our findings suggest that some fundamental features of tetrapod locomotion, including pelvic limb gait patterns and substrate association, probably arose in sarcopterygians before the origin of digited limbs or terrestriality. It follows that the attribution of some of the nondigited Devonian fossil trackways to limbed tetrapods may need to be revisited.T he vertebrate water-to-land transition initiated in the Devonian was a key event in the history of life. The ability to move in a variety of terrestrial and semiterrestrial environments opened up a range of new ecosystems for colonization and led to the diversity of tetrapod clades we see today. One essential adaptation in the evolution of tetrapods was the ability to locomote on land, a trait that required significant morphological and functional changes in the appendicular system. Many of these morphological changes can be observed in the fossil record (1-14). Work on basal tetrapod fossils has revealed that even those with digited limbs can be aquatic (5, 7). Some major questions these findings raised were how tetrapod-like limbs functioned in aquatic habitats, and in what sequence the characteristics of terrestrial tetrapod locomotion were acquired. These characteristics include the broad use of alternating limb movements, as in walking, the use of pelvic appendages as major propulsors, and the use of a bottom substrate (i.e., the solid surface underlying the fluid environment) to generate propulsive force.Whereas body fossils cannot directly inform the order in which these functional traits were acquired, fossil trackways can give us valuable information on how animals moved. Many fossil trackways from the Devonian are indicative of quadrupedal and bipedal gaits very similar to those used by modern terrestrial tetrapods (1,3,9,13,14). That tracks were preserved demonstrates that these animals were walking on a substrate. That these trackways have a cosmopolitan distribution implies that the animals responsible for generating them were themselves widespread, and likely abundant and diverse. Because we can...

Background: Inclusive STEM (traditionally known to stand for "Science, Technology, Engineering, and Math") high schools are emerging across the country as a mechanism for improving STEM education and getting more and diverse students into STEM majors and careers. However, there is no consensus on what these schools are or should be, making it difficult to both evaluate their effectiveness and scale successful models. We addressed this problem by working with inclusive STEM high school leaders and stakeholders to articulate and understand their intended school models. This "bottom-up" approach is in contrast with other studies that have taken a "top-down," literature-based approach to defining STEM schools. Results: Through this process, we identified 76 critical components of STEM schools and derived a theoretical framework of eight elements that represent the common goals and strategies employed by inclusive STEM high schools across the country: Personalization of Learning; Problem-Based Learning; Rigorous Learning; Career, Technology, and Life Skills; School Community and Belonging; External Community; Staff Foundations; and External Factors. This framework offers a clear picture of what exactly inclusive STEM schools are and common language for both researchers and practitioners. Interestingly, STEM disciplinary content did not emerge as a defining component across school models.

Objective: To evaluate the efficacy of childhood obesity interventions and conduct a taxonomy of intervention components that are most effective in changing obesity-related health outcomes in children 2-5 years of age. Methods: Comprehensive searches located 51 studies from 18,335 unique records. Eligible studies: (1) assessed children aged 2-5, living in the United States; (2) evaluated an intervention to improve weight status; (3) identified a same-aged comparison group; (4) measured BMI; and (5) were available between January 2005 and August 2019. Coders extracted study, sample, and intervention characteristics. Effect sizes [ESs; and 95% confidence intervals (CIs)] were calculated by using random-effects models. Metaregression was used to determine which intervention components explain variability in ESs. Results: Included were 51 studies evaluating 58 interventions (N = 29,085; mean age = 4 years; 50% girls). Relative to controls, children receiving an intervention had a lower BMI at the end of the intervention (g = 0.10, 95% CI = 0.02-0.18; k = 55) and at the last follow-up (g = 0.17, 95% CI = 0.04-0.30; k = 14; range = 18-143 weeks). Three intervention components moderated efficacy: engage caregivers in praise/encouragement for positive health-related behavior; provide education about the importance of screen time reduction to caregivers; and engage pediatricians/health care providers.

The West African lungfish (Protopterus annectens) performs benthic, pelvic fin-driven locomotion with gaits common to tetrapods, the sister group of the lungfishes. Features of P. annectens movement are similar to those of modern tetrapods and include use of the distal region of the pelvic fin as a “foot,” use of the fin to lift the body above the substrate and rotation of the fin around the joint with the pelvis. In contrast to these similarities in movement, the pelvic fins of P. annectens are long, slender structures that are superficially very different from tetrapod limbs. Here, we describe the musculoskeletal anatomy of the pelvis and pelvic fins of P. annectens with dissection, magnetic resonance imaging, histology and 3D-reconstruction methods. We found that the pelvis is embedded in the hypaxial muscle by a median rostral and two dorsolateral skeletal projections. The protractor and retractor muscles at the base of the pelvic fin are fan-shaped muscles that cup the femur. The skeletal elements of the fin are serially repeating cartilage cylinders. Along the length of the fin, repeating truncated cones of muscles, the musculus circumradialis pelvici, are separated by connective tissue sheets that connect the skeletal elements to the skin. The simplicity of the protractor and retractor muscles at the base of the fin is surprising, given the complex rotational movement those muscles generate. In contrast, the series of many repeating segmental muscles along the length of the fin is consistent with the dexterity of bending of the distal limb. P. annectens can provide a window into softtissue anatomy and sarcopterygian fish fin function that complements the fossil data from related taxa. This work, combined with previous behavioral examination of P. annectens, illustrates that fin morphologies that do not appear to be capable of walking can accomplish that function, and may inform the interpretation of fossil anatomical evidence.

African lungfish Protopterus annectens can produce rotational movements around the joint between the pelvis and the pelvic fin, allowing these animals to walk across benthic substrates. In tetrapods, limb rotation at the hip joint is a common feature of substrate-based locomotion. For sprawling tetrapods, rotation can involve nine or more muscles, which are often robust and span multiple joints. In contrast, P. annectens uses a modest morphology of two fan-shaped muscles, the pelvic fin protractor and retractor, to accomplish this movement. We hypothesized that functional subdivision, coupled with their broad insertions on the femur, allows each of these muscles to pull on the limb from multiple directions and provides a mechanism for fin rotation. To test this hypothesis, we examined the muscle activity at three locations in both the protractor and the retractor muscles during walking. Electromyograms show differences in the timing of muscle activation between dorsal and ventral regions of each muscle, suggesting that each muscle is functionally subdivided once. The subdivisions demonstrate sequential onsets of muscle activity and overlap of activity between regions, which are also features of limb control in tetrapods. These data indicate that subdivisions of protractor and retractor muscles impart functional complexity to a morphologically simple system, and suggest a mechanism that allows lungfish to produce a tetrapod-like walking gait with only two muscles. As one of few extant sarcopterygian fishes, P. annectens may provide important functional data to inform interpretation of limb movement of fossil relatives.