A Morrison stem gekkotan reveals gecko evolution and Jurassic biogeography.

Geckos are a speciose and globally distributed clade of Squamata (lizards, including snakes and amphisbaenians) that are characterized by a host of modifications for nocturnal, scansorial and insectivorous ecologies. They are among the oldest divergences in the lizard crown, so understanding the origin of geckoes (Gekkota) is essential to understanding the origin of Squamata, the most species-rich extant tetrapod clade. However, the poor fossil record of gekkotans has obscured the sequence and timing of the assembly of their distinctive morphology. Here, we describe the first North American stem gekkotan based on a three-dimensionally preserved skull from the Morrison Formation of western North America. Despite its Late Jurassic age, the new species already possesses several key characteristics of the gekkotan skull along with retained ancestral features. We show that this new stem gekkotan, and several previously named species of uncertain phylogenetic relationships, comprise a widespread clade of early crown lizards, substantiating faunal homogeneity in Laurasia during the Late Jurassic that extended across disparate ecological, body-size and physiological classes.

Income inequality in later years: occupational trajectories or initial social characteristics?

This study focuses on the constitution of financial reserves in Switzerland from a longitudinal perspective. Personal income after retirement derives from financial reserves whose constitution depends both on positional factors, such as sex and birth cohorts, and processual factors, such as occupational trajectories, in the institutional context of the Swiss pension system (structural factors). We hypothesise that some processual, positional and structural factors interact with each other to shape financial reserves available in old age. We assess this set of factors and their interactions using the occupational trajectory types stemming from optimal matching analysis (OMA) combined with the hierarchical clustering and regression tree methods. We used the retrospective biographic data SHARELIFE gathered during the third wave of the SHARE survey in 2009. The results show that occupational trajectories are influential factors accounting for much of the financial reserves available in later life. However, these processual factors interact with positional factors such as sex and birth cohort. The retirement schemes generalised in Switzerland during the period under consideration add up to the effect of positional factors on the constitution of financial reserves.

Evolutionary origins of the prolonged extant squamate radiation.

Squamata is the most diverse clade of terrestrial vertebrates. Although the origin of pan-squamates lies in the Triassic, the oldest undisputed members of extant clades known from nearly complete, uncrushed material come from the Cretaceous. Here, we describe three-dimensionally preserved partial skulls of two new crown lizards from the Late Jurassic of North America. Both species are placed at the base of the skink, girdled, and night lizard clade Pan-Scincoidea, which consistently occupies a position deep inside the squamate crown in both morphological and molecular phylogenies. The new lizards show that several features uniting pan-scincoids with another major lizard clade, the pan-lacertoids, in trees using morphology were convergently acquired as predicted by molecular analyses. Further, the palate of one new lizard bears a handful of ancestral saurian characteristics lost in nearly all extant squamates, revealing an underappreciated degree of complex morphological evolution in the early squamate crown. We find strong evidence for close relationships between the two new species and Cretaceous taxa from Eurasia. Together, these results suggest that early crown squamates had a wide geographic distribution and experienced complicated morphological evolution even while the Rhynchocephalia, now solely represented by the tuatara, was the dominant clade of lepidosaurs.

Fossil biomolecules reveal an avian metabolism in the ancestral dinosaur.

Birds and mammals independently evolved the highest metabolic rates among living animals1. Their metabolism generates heat that enables active thermoregulation1, shaping the ecological niches they can occupy and their adaptability to environmental change2. The metabolic performance of birds, which exceeds that of mammals, is thought to have evolved along their stem lineage3-10. However, there is no proxy that enables the direct reconstruction of metabolic rates from fossils. Here we use in situ Raman and Fourier-transform infrared spectroscopy to quantify the in vivo accumulation of metabolic lipoxidation signals in modern and fossil amniote bones. We observe no correlation between atmospheric oxygen concentrations11 and metabolic rates. Inferred ancestral states reveal that the metabolic rates consistent with endothermy evolved independently in mammals and plesiosaurs, and are ancestral to ornithodirans, with increasing rates along the avian lineage. High metabolic rates were acquired in pterosaurs, ornithischians, sauropods and theropods well before the advent of energetically costly adaptations, such as flight in birds. Although they had higher metabolic rates ancestrally, ornithischians reduced their metabolic abilities towards ectothermy. The physiological activities of such ectotherms were dependent on environmental and behavioural thermoregulation12, in contrast to the active lifestyles of endotherms1. Giant sauropods and theropods were not gigantothermic9,10, but true endotherms. Endothermy in many Late Cretaceous taxa, in addition to crown mammals and birds, suggests that attributes other than metabolism determined their fate during the terminal Cretaceous mass extinction.

Prescription, Compliance, and Burden Associated with Salt-Restricted Diets in Heart Failure Patients: Results from the French National OFICSel Observatory.

(1) Background: There is much debate about the use of salt-restricted diet for managing heart failure (HF). Dietary guidelines are inconsistent and lack evidence. (2) Method: The OFICSel observatory collected data about adults hospitalised for HF. The data, collected using study-specific surveys, were used to describe HF management, including diets, from the cardiologists' and patients' perspectives. Cardiologists provided the patients' clinical, biological, echocardiography, and treatment data, while the patients provided dietary, medical history, sociodemographic, morphometric, quality of life, and burden data (burden scale in restricted diets (BIRD) questionnaire). The differences between the diet recommended by the cardiologist, understood by the patient, and the estimated salt intake (by the patient) and diet burden were assessed. (3) Results: Between March and June 2017, 300 cardiologists enrolled 2822 patients. Most patients (90%) were recommended diets with <6 g of salt/day. Mean daily salt consumption was 4.7 g (standard deviation (SD): 2.4). Only 33% of patients complied with their recommended diet, 34% over-complied, and 19% under-complied (14% unknown). Dietary restrictions in HF patients were associated with increased burden (mean BIRD score of 8.1/48 [SD: 8.8]). (4) Conclusion: Healthcare professionals do not always follow dietary recommendations, and their patients do not always understand and comply with diets recommended. Restrictive diets in HF patients are associated with increased burden. An evidence-based approach to developing and recommending HF-specific diets is required.

Determinants of Antithrombotic Treatment for Atrial Fibrillation in Octogenarians: Results of the OCTOFA Study.

BACKGROUND AND OBJECTIVE: Atrial fibrillation, the most frequent form of arrhythmia, affects 5-15% individuals aged > 80 years. Stroke is a major risk for atrial fibrillation patients. The benefits of anticoagulant therapy clearly outweigh the risk of hemorrhage, even in the elderly. Despite the efficacy of warfarin, many eligible patients receive no prophylactic antithrombotic therapy. New generation oral anticoagulants compare favorably with vitamin K antagonists in the prevention of thromboembolic events and hemorrhage. These new agents are likely to influence the prescribing habits of anticoagulants in atrial fibrillation. The aim of this study to investigate both the frequency and the determining factors of anticoagulant prescriptions in AF patients aged ≥ 80 years and followed up by private-practice cardiologists in France. METHODS: The OCTOFA (Atrial Fibrillation in Octogenarians) Study assessed the anticoagulant prescribing habits of cardiologists in France. The volunteer cardiologists recruited all consecutive patients fulilling the inclusion criteria. RESULTS: Between June 2013 and September 2016, 89 cardiologists recruited 738 eligible patients: age ≥ 80 years, non-valvular atrial fibrillation, no other compelling indication for anticoagulation therapy, no recent acute coronary syndrome or stroke. Most (90.7%) patients were on oral anticoagulant therapy: vitamin K antagonist or non-vitamin K antagonist oral anticoagulants, low molecular weight heparin (1.4%), aspirin (5.7%), and no antithrombotic treatment (2.2%). Patients on vitamin K antagonists were older (p < 0.001), had lower renal function (p = 0.033), and had a more frequent history of myocardial infarction (p < 0.001), heart failure (p = 0.001), peripheral artery disease (p = 0.033), major hemorrhage (p = 0.025), and falls (p = 0.045). Four determining factors of anticoagulant prescriptions were statistically significant: high CHA2DS2-VASc score (p < 0.001), high HAS-BLED score (p < 0.001), age > 90 years (p = 0.001), and moderate/severe cognitive impairment (p = 0.002). CONCLUSIONS: Most private-practice cardiologists prescribe anticoagulant treatment according to current guidelines in elderly atrial fibrillation patients. Non-vitamin K antagonist oral anticoagulants represent a significant proportion of prescriptions.

Noise and biases in genomic data may underlie radically different hypotheses for the position of Iguania within Squamata.

Squamate reptiles are a major component of vertebrate biodiversity whose crown-clade traces its origin to a narrow window of time in the Mesozoic during which the main subclades diverged in rapid succession. Deciphering phylogenetic relationships among these lineages has proven challenging given the conflicting signals provided by genomic and phenomic data. Most notably, the placement of Iguania has routinely differed between data sources, with morphological evidence supporting a sister relationship to the remaining squamates (Scleroglossa hypothesis) and molecular data favoring a highly nested position alongside snakes and anguimorphs (Toxicofera hypothesis). We provide novel insights by generating an expanded morphological dataset and exploring the presence of phylogenetic signal, noise, and biases in molecular data. Our analyses confirm the presence of strong conflicting signals for the position of Iguania between morphological and molecular datasets. However, we also find that molecular data behave highly erratically when inferring the deepest branches of the squamate tree, a consequence of limited phylogenetic signal to resolve this ancient radiation with confidence. This, in turn, seems to result from a rate of evolution that is too high for historical signals to survive to the present. Finally, we detect significant systematic biases, with iguanians and snakes sharing faster rates of molecular evolution and a similarly biased nucleotide composition. A combination of scant phylogenetic signal, high levels of noise, and the presence of systematic biases could result in the misplacement of Iguania. We regard this explanation to be at least as plausible as the complex scenario of convergence and reversals required for morphological data to be misleading. We further evaluate and discuss the utility of morphological data to resolve ancient radiations, as well as its impact in combined-evidence phylogenomic analyses, with results relevant for the assessment of evidence and conflict across the Tree of Life.

Early Evolution of Modern Birds Structured by Global Forest Collapse at the End-Cretaceous Mass Extinction.

The fossil record and recent molecular phylogenies support an extraordinary early-Cenozoic radiation of crown birds (Neornithes) after the Cretaceous-Paleogene (K-Pg) mass extinction [1-3]. However, questions remain regarding the mechanisms underlying the survival of the deepest lineages within crown birds across the K-Pg boundary, particularly since this global catastrophe eliminated even the closest stem-group relatives of Neornithes [4]. Here, ancestral state reconstructions of neornithine ecology reveal a strong bias toward taxa exhibiting predominantly non-arboreal lifestyles across the K-Pg, with multiple convergent transitions toward predominantly arboreal ecologies later in the Paleocene and Eocene. By contrast, ecomorphological inferences indicate predominantly arboreal lifestyles among enantiornithines, the most diverse and widespread Mesozoic avialans [5-7]. Global paleobotanical and palynological data show that the K-Pg Chicxulub impact triggered widespread destruction of forests [8, 9]. We suggest that ecological filtering due to the temporary loss of significant plant cover across the K-Pg boundary selected against any flying dinosaurs (Avialae [10]) committed to arboreal ecologies, resulting in a predominantly non-arboreal post-extinction neornithine avifauna composed of total-clade Palaeognathae, Galloanserae, and terrestrial total-clade Neoaves that rapidly diversified into the broad range of avian ecologies familiar today. The explanation proposed here provides a unifying hypothesis for the K-Pg-associated mass extinction of arboreal stem birds, as well as for the post-K-Pg radiation of arboreal crown birds. It also provides a baseline hypothesis to be further refined pending the discovery of additional neornithine fossils from the Latest Cretaceous and earliest Paleogene.

Fingerprinting snakes: paleontological and paleoecological implications of zygantral growth rings in Serpentes.

We introduce a new non-destructive source of skeletochronological data with applications to species identification, associating disarticulated remains, assessing minimum number of individuals (MNI), and collection management of fossil snakes, but with potential implications for all bony vertebrates, extinct or extant. Study of a diverse sample of Recent henophidian snakes confirms that annual growth cycles (AGCs) visible on the surface of the vertebral zygantrum correspond to lines of arrested growth in osteohistological thin sections and accordingly reflect chronological age. None of the specimens considered here showed signs of remodelling of the zygantrum, suggesting that a complete, unaltered age record is preserved. We tested potential influences on AGCs with a single experimental organism, a male Bogertophis subocularis, that was raised at a controlled temperature and with constant access to mice and water. The conditions in which this individual was maintained, including that it had yet to live through a full reproductive cycle, enabled us to determine that its AGCs reflect only the annual solar cycle, and neither temperature, nor resource availability, nor energy diversion to gametogenesis could explain that it still exhibited lines of arrested growth. Moreover, growth lines in this specimen are deposited toward the end of the growth season in the fall, and not in the winter, during which this individual continued to feed and grow, even though this mid-latitude species would normally be hibernating and not growing. This suggests that growth lines are not caused by hibernation, but reflect the onset of a physiological cycle preparing Bogertophis subocularis for winter rest. That being said, hibernation and reproductive cycle could still influence the amount of time represented by an individual growth line. Growth-line number and AGC spacing-pattern, plus centrum length, are used to estimate MNI of the Early Eocene fossil snake Boavus occidentalis collected from the Willwood Formation over two field seasons during the late 19th century. We identified eight or nine individuals among specimens previously parcelled among two specimen lots collected during those expeditions.

A tiny Triassic saurian from Connecticut and the early evolution of the diapsid feeding apparatus.

Following the Permo-Triassic Extinction, large-bodied diapsid reptiles-with a body length >1 m-rapidly expanded their ecological roles. This diversification is reflected in enormous disparity in the development of the rostrum and adductor chamber. However, it is unclear how marked the diversity of the feeding apparatus was in contemporary small-bodied diapsids. Here we describe the remarkably small skull (2.5 cm long) of a saurian reptile, Colobops noviportensis, gen. et sp. nov., from the Triassic New Haven Arkose of Connecticut, USA. The taxon possesses an exceptionally reinforced snout and strikingly expanded supratemporal fossae for adductor musculature relative to any known Mesozoic or Recent diapsid of similar size. Our phylogenetic analyses support C. noviportensis as an early diverging pan-archosaur. Colobops noviportensis reveals extraordinary disparity of the feeding apparatus in small-bodied early Mesozoic diapsids, and a suite of morphologies, functionally related to a powerful bite, unknown in any small-bodied diapsid.

French Registry on Acute ST-elevation and non-ST-elevation Myocardial Infarction 2015 (FAST-MI 2015). Design and baseline data.

BACKGROUND: The FAST-MI programme, consisting of 1-month surveys of patients admitted to hospital for acute myocardial infarction (AMI) in France, has run since 2005. AIM: To gather data on the characteristics, management and outcomes of patients hospitalized for AMI at the end of 2015 in France and to provide comparisons with the previous surveys. METHODS: Consecutive adults with ST-segment elevation myocardial infarction (STEMI) or non-ST-segment-elevation myocardial infarction (NSTEMI) with symptom onset≤48hours were included over a 1-month period, with a possible extension of recruitment for 1 additional month. Patients with AMI following cardiovascular procedures were excluded. In all, 204 centres participated in the survey (114 community hospitals, 40 academic, 48 private clinics, 2 army hospitals), representing 78% of French centres managing AMI patients. Inclusion started from 5 October 2015. Data were collected on-site from source files by external research technicians, using an electronic case record form with automatic quality checks. Centralized biology was organized in voluntary centres to collect RNA and DNA samples, serum and stools. Long-term follow-up was organized centrally with interrogation of municipal registry offices, physicians and by direct contact with the patients or their families. RESULTS: A total of 5291 patients were included over the entire recruitment period, with 3813 included during the first month (STEMI: 49%, NSTEMI: 51%). Mean age was 66±14 years, 29% were≥75 years of age, 28% were women; 80% presented with typical chest pain. In STEMI patients, 6% received intravenous fibrinolysis and 71% underwent primary PCI. The hospital death rate was 2.7% (STEMI: 2.8%, NSTEMI: 2.5%). CONCLUSIONS: Recruitment was in line with expectations and the first data show that management has continued to evolve since the 2010 survey, with continued improvement in hospital outcomes.

The origin of snakes: revealing the ecology, behavior, and evolutionary history of early snakes using genomics, phenomics, and the fossil record.

BACKGROUND: The highly derived morphology and astounding diversity of snakes has long inspired debate regarding the ecological and evolutionary origin of both the snake total-group (Pan-Serpentes) and crown snakes (Serpentes). Although speculation abounds on the ecology, behavior, and provenance of the earliest snakes, a rigorous, clade-wide analysis of snake origins has yet to be attempted, in part due to a dearth of adequate paleontological data on early stem snakes. Here, we present the first comprehensive analytical reconstruction of the ancestor of crown snakes and the ancestor of the snake total-group, as inferred using multiple methods of ancestral state reconstruction. We use a combined-data approach that includes new information from the fossil record on extinct crown snakes, new data on the anatomy of the stem snakes Najash rionegrina, Dinilysia patagonica, and Coniophis precedens, and a deeper understanding of the distribution of phenotypic apomorphies among the major clades of fossil and Recent snakes. Additionally, we infer time-calibrated phylogenies using both new 'tip-dating' and traditional node-based approaches, providing new insights on temporal patterns in the early evolutionary history of snakes. RESULTS: Comprehensive ancestral state reconstructions reveal that both the ancestor of crown snakes and the ancestor of total-group snakes were nocturnal, widely foraging, non-constricting stealth hunters. They likely consumed soft-bodied vertebrate and invertebrate prey that was subequal to head size, and occupied terrestrial settings in warm, well-watered, and well-vegetated environments. The snake total-group - approximated by the Coniophis node - is inferred to have originated on land during the middle Early Cretaceous (~128.5 Ma), with the crown-group following about 20 million years later, during the Albian stage. Our inferred divergence dates provide strong evidence for a major radiation of henophidian snake diversity in the wake of the Cretaceous-Paleogene (K-Pg) mass extinction, clarifying the pattern and timing of the extant snake radiation. Although the snake crown-group most likely arose on the supercontinent of Gondwana, our results suggest the possibility that the snake total-group originated on Laurasia. CONCLUSIONS: Our study provides new insights into when, where, and how snakes originated, and presents the most complete picture of the early evolution of snakes to date. More broadly, we demonstrate the striking influence of including fossils and phenotypic data in combined analyses aimed at both phylogenetic topology inference and ancestral state reconstruction.

Biogeography of worm lizards (Amphisbaenia) driven by end-Cretaceous mass extinction.

Worm lizards (Amphisbaenia) are burrowing squamates that live as subterranean predators. Their underground existence should limit dispersal, yet they are widespread throughout the Americas, Europe and Africa. This pattern was traditionally explained by continental drift, but molecular clocks suggest a Cenozoic diversification, long after the break-up of Pangaea, implying dispersal. Here, we describe primitive amphisbaenians from the North American Palaeocene, including the oldest known amphisbaenian, and provide new and older molecular divergence estimates for the clade, showing that worm lizards originated in North America, then radiated and dispersed in the Palaeogene following the Cretaceous-Palaeogene (K-Pg) extinction. This scenario implies at least three trans-oceanic dispersals: from North America to Europe, from North America to Africa and from Africa to South America. Amphisbaenians provide a striking case study in biogeography, suggesting that the role of continental drift in biogeography may be overstated. Instead, these patterns support Darwin and Wallace's hypothesis that the geographical ranges of modern clades result from dispersal, including oceanic rafting. Mass extinctions may facilitate dispersal events by eliminating competitors and predators that would otherwise hinder establishment of dispersing populations, removing biotic barriers to dispersal.

A Sociopoética como prática de pesquisa integral / Sociopoetics as practice of integral research / La Sociopoética como práctica de investigación integral

A partir das noções de vigilância e de vacuidade amorosas, este trabalho estuda as condições da instituição de uma ciência integrada que acolhe tanto a intuição característica do modo de fazer ciência das comunidades indígenas, afrodescendentes e populares, como o racionalismo crítico da academia. Sendo a Sociopoética uma abordagem privilegiada na configuração da identidade do pesquisador integral, o autor propõe técnicas de pesquisa intuitivas inspiradas na dança, nas sensações e no perspectivismo indígena, a fim de superar três obstáculos ao conhecimento integrado: a culpa, o medo e a falta de fé em si mesmo e no universo. Com referências em Deleuze, Guattari e Bergson, até o transe pode ganhar a dignidade de um método, na pesquisa considerada como uma conspiração do brincar.

Building on the notions of loving surveillance and loving emptiness, this paper studies the conditions for instituting an integrated science that welcomes both the intuition characteristic of how science is done in indigenous, Afro-Americanand grassroots communities, and critical academic rationalism. As Sociopoetics is particularly appropriate as an approach to shaping the identity of a comprehensive researcher, the author proposes intuitive research techniques inspired in dance, feelings and indigenous perspectivism, with a view to surmounting three obstacles to integrated knowledge: guilt, fear, and lack of faith in oneself and the universe. With references in Deleuze, Guattari and Bergson, even trance can gain the status of method in research considered a conspiracy of play.

A partir de los conceptos de vigilancia y vacuidad amorosas, este trabajo estudia las condiciones de la institución de una ciencia integrada que da la bienvenida tanto a la intuición, característica de como se cream las ciencias indígena, afroamericana y popular, como el racionalismo crítico de la academia. Siendo la Sociopoética un enfoque primordial en la formación de la identidade del investigador integral, el autor propone técnicas intuitivas de investigación inspiradas en la danza en, las sensaciones y em el perspectivismo indígena, con el fin de superar tres obstáculos para el conocimiento integrado: la culpa, el miedo y la falta de fe en si mismo y em el universo. Con referencias en Deleuze, Guattari y Bergson, el trance puede ganar la dignidad de un método, en la investigación considerada una conspiración del jugar.

Toward consilience in reptile phylogeny: miRNAs support an archosaur, not lepidosaur, affinity for turtles.

Understanding the phylogenetic position of crown turtles (Testudines) among amniotes has been a source of particular contention. Recent morphological analyses suggest that turtles are sister to all other reptiles, whereas the vast majority of gene sequence analyses support turtles as being inside Diapsida, and usually as sister to crown Archosauria (birds and crocodilians). Previously, a study using microRNAs (miRNAs) placed turtles inside diapsids, but as sister to lepidosaurs (lizards and Sphenodon) rather than archosaurs. Here, we test this hypothesis with an expanded miRNA presence/absence dataset, and employ more rigorous criteria for miRNA annotation. Significantly, we find no support for a turtle + lepidosaur sister-relationship; instead, we recover strong support for turtles sharing a more recent common ancestor with archosaurs. We further test this result by analyzing a super-alignment of precursor miRNA sequences for every miRNA inferred to have been present in the most recent common ancestor of tetrapods. This analysis yields a topology that is fully congruent with our presence/absence analysis; our results are therefore in accordance with most gene sequence studies, providing strong, consilient molecular evidence from diverse independent datasets regarding the phylogenetic position of turtles.

Homology of the enigmatic nuchal bone reveals novel reorganization of the shoulder girdle in the evolution of the turtle shell.

The turtle shell represents a unique modification of the ancestral tetrapod body plan. The homologies of its approximately 50 bones have been the subject of debate for more than 200 years. Although most of those homologies are now firmly established, the evolutionary origin of the dorsal median nuchal bone of the carapace remains unresolved. We propose a novel hypothesis in which the nuchal is derived from the paired, laterally positioned cleithra-dorsal elements of the ancestral tetrapod pectoral girdle that are otherwise retained among extant tetrapods only in frogs. This hypothesis is supported by origin of the nuchal as paired, mesenchymal condensations likely derived from the neural crest followed by a unique two-stage pattern of ossification. Further support is drawn from the establishment of the nuchal as part of a highly conserved "muscle scaffold" wherein the cleithrum (and its evolutionary derivatives) serves as the origin of the Musculus trapezius. Identification of the nuchal as fused cleithra is congruent with its general spatial relationships to other elements of the shoulder girdle in the adult morphology of extant turtles, and it is further supported by patterns of connectivity and transformations documented by critical fossils from the turtle stem group. The cleithral derivation of the nuchal implies an anatomical reorganization of the pectoral girdle in which the dermal portion of the girdle was transformed from a continuous lateral-ventral arc into separate dorsal and ventral components. This transformation involved the reduction and eventual loss of the scapular rami of the clavicles along with the dorsal and superficial migration of the cleithra, which then fused with one another and became incorporated into the carapace.

Evolutionary origin of the turtle shell.

The origin of the turtle shell has perplexed biologists for more than two centuries. It was not until Odontochelys semitestacea was discovered, however, that the fossil and developmental data could be synthesized into a model of shell assembly that makes predictions for the as-yet unestablished history of the turtle stem group. We build on this model by integrating novel data for Eunotosaurus africanus-a Late Guadalupian (∼260 mya) Permian reptile inferred to be an early stem turtle. Eunotosaurus expresses a number of relevant characters, including a reduced number of elongate trunk vertebrae (nine), nine pairs of T-shaped ribs, inferred loss of intercostal muscles, reorganization of respiratory muscles to the ventral side of the ribs, (sub)dermal outgrowth of bone from the developing perichondral collar of the ribs, and paired gastralia that lack both lateral and median elements. These features conform to the predicted sequence of character acquisition and provide further support that E. africanus, O. semitestacea, and Proganochelys quenstedti represent successive divergences from the turtle stem lineage. The initial transformations of the model thus occurred by the Middle Permian, which is congruent with molecular-based divergence estimates for the lineage, and remain viable whether turtles originated inside or outside crown Diapsida.