Sternal Rib Research Articles

Anatomical and morphometric studies on the axial skeleton of ostrich (Struthio camelus)

The present study showed a descriptive anatomical study of the parts of the axial skeleton in the ostrich (Struthio camelus) in addition to a morphometric study of each bone. We studied 7 male ostriches aged from 1 to 3 years with an average weight of 120.00 kg. The cranium exhibited two vast orbits supported by a sclerotic ring. Hyoid apparatus was fine delicate horseshoe-shaped and comprised Basihyale, Urohyale, and Cornu branchiale. Cornu branchiale were paired and long rod-shaped, consisting of a proximal bony part Ceratobranchiale and slightly curved distal cartilaginous process, the Epibranchiale located on either side of the hyoid apparatus. The whole vertebral column comprised 54 vertebrae, including 18 cervical vertebrae, 7 separated thoracic vertebrae, a synsacrum, and 9 separated caudal vertebrae. Atlas had a butterfly-shape with a narrow width and large vertebral foramen. Axis had a protruded dens with a rounded tip that arose from the cranial surface of the body for articulation with the Incisura fossae of atlas. Several Pneumatic foramina were found in the cervical vertebrae. The transverse foramen was found in all the cervical vertebrae except atlas. The ribs were nine pairs in number, the sternal ribs extended from the third to the seventh rib while the rest were asternal floating ribs. The sternum was a broad quadrilateral extensive bone, lacking the keel bone. It had dorsally several Pneumatic foramina.

Radiological Methods for the Imaging of Congenital Malformations of C6-T1, the First and Second Sternal Ribs and Development of a Classification System, Demonstrated in Warmblood Horses

There are conflicting data in studies on malformations of the cervicothoracic (C-T) junction (C6 to T2, including the first and second ribs), but evidence is mounting that they can be of clinical significance for horses. The objectives of this study were to establish a radiographic protocol for imaging the C-T junction in the field and to classify the radiographic variations found in 39 warmblood horses presented for clinical evaluation due to behavioral or performance issues. Malformations of the ventral lamina of C6 and transposition onto the ventral aspect of C7 were seen in 37/39 (94.9%) horses for both conditions. Rib anomalies were found among the horses with C6 and C7 malformations. A missing first rib, unilateral or bilateral, was found in 3/35 (11.4%) horses, a unilateral shortening of the rib in 17/35 (48.6%) horses, a bilateral shortening of the ribs in 12/35 (34.3%) horses, bifid ribs in 3/35 (8.6%) horses, and only 4/35 (11.4%) horses had a normal length of the first rib on both sides. There was a moderately to highly significant association between the grades of left and right malformations of C6 and C7 and first ribs as well as between C6 and C7. A large number of malformations were visualized radiographically at the C-T junction using the newly described methods of latero-lateral and oblique radiographic projections, which allows for these features to be identified in living horses.

Sternal Rib Ends as a Method of Age Estimation at the CIL: A Brief Note

This communication reports the relationship between skeletal age estimates based on the sternal rib ends (using the phase method of İşcan and colleagues, later revised by Hartnett) and the chronological age at the death of 221 U.S. military casualties processed by the Scientific Analysis section of the Defense POW/MIA Accounting Agency and its predecessor laboratories from 2000 to the present. Previously published age ranges for each phase do not provide accurate estimates for a sufficient proportion of the cases for forensic use; as an example, the age ranges that accompany reference cast sets proved accurate for 55% of CIL cases. Combining the published age ranges of İşcan and Hartnett, on the other hand, proved accurate in 99% of the cases.

Historic Horse Family Displaying Malformations of the Cervicothoracic Junction and Their Connection to Modern German Warmblood Horses.

Malformations of the equine cervicothoracic junction affect the C6 and C7 cervical vertebrae, the T1 thoracic vertebra and in variable extent the first and second sternal ribs. To date, the clinical impact of this malformation, its prevalence and mode of inheritance in equine populations are not yet determined. We examined five skeletons for signs of malformation of the cervicothoracic junction, including three skeletons from widely used Thoroughbred stallions affected with the malformation and two skeletons serving as a comparison. The three affected historical horses were the Thoroughbred stallions Der Loewe XX, Birkhahn XX and their common great grandsire Dark Ronald XX. Malformations of C6 and C7 showed a large variation between the three stallions, as Dark Ronald XX, Der Loewe XX and Birkhahn XX were affected uni-laterally at C6 and C7, uni-laterally at C6 and bi-laterally at C6 and C7, respectively, with varying grades. In order to evaluate whether or not these malformations are incidental, we took a random sample of 20 living German Warmblood horses, which are distant descendants of these stallions. This sample consisted of ten controls and ten horses with malformations of C6/C7. Blood proportions of the historical sires in the modern Warmblood horses ranged from 0.10 to 6.25%. The contribution to inbreeding in each individual horse of our selected horse group by those sires was expressed as a percentage of the total inbreeding coefficient and ranged from 0.01 to 17.96%, demonstrating their influence on the modern Warmblood. In the present study, we were able to describe the variability of the malformation of C6/C7 within a horse family including historic and modern horses. Additionally, we detected variations appearing in connection with malformations of the cervicothoracic junction that have not been described in the literature yet. This is the first time that the malformations of C6 and C7 have been described within a familial context, providing hints on inheritance in Thoroughbreds and Warmbloods. It is worthwhile to carry out further studies in a larger setting to gain more comprehensive insights into the inheritance of the malformation and the role of important ancestors.

Cross-sectional properties of rib geometry from an adult population.

Introduction: Human body models (HBMs) play a key role in improving modern vehicle safety systems to protect broad populations. However, their geometry is commonly derived from single individuals chosen to meet global anthropometric targets, thus their internal anatomy may not fully represent the HBM's target demographic. Past studies show sixth rib cross-sectional geometry differences between HBM ribs and population-derived ribs, and corrections to HBM ribs based on these data have improved HBM's abilities to predict rib fracture locations. Methods: We measure and report average and standard deviations (SDs) in rib cross-sectional geometric properties derived from live subject CT scans of 240 adults aged 18-90. Male and female results are given as functions of rib number and rib lengthwise position for ribs 2 through 11. Population means/SDs are reported for measures of rib total area, rib cortical bone area, and rib endosteal area, as well as inertial moment properties of these rib sections. These population corridors are compared between males and females, and against the baseline rib geometries defined in six current HBMs. Results: Total cross-sectional area results found average males ribs to be larger than those of females by between approximately 1-2 SDs depending on rib number and position, and larger in cortical bone cross-sectional area by between 0-1 SDs. Inertial moment ratios showed female ribs being between approximately 0-1 SDs more elongated than male ribs, dependent again on rib number and position. Rib cross-sectional areas from 5 of the 6 HBMs were found to be overly large along substantial portions of most ribs when compared to average population corridors. Similarly, rib aspect ratios in HBMs deviated from average population data by up to 3 SDs in regions towards sternal rib ends. Discussion: Overall, while most HBMs capture overall trends such as reductions in cross-section along shaft lengths, many also exhibit local variation that deviates from population trends. This study's results provide the first reference values for assessing the cross-sectional geometry of human ribs across a wide range of rib levels. Results also further provide clear guidelines to improve rib geometry definitions present in current HBMs in order to better represent their target demographic.

Ultrasound-guided percutaneous cryoneurolysis for management of acute sternal fracture pain

Establishing adequate analgesia for rib and sternal fractures remains a challenge due to the prolonged nature of the associated pain. Historically, cryoneurolysis has demonstrated beneficial in treating chronic pain, and the recent development of hand-held devices has allowed its functionality to expand into the management of acute pain. We present a polytrauma patient with sternal and multiple rib fractures that underwent ultrasound-guided intercostal cryoneurolysis at bedside, resulting in significant analgesia lasting several weeks and improving mobilization. This is the first report of the utilization of cryoneurolysis to treat acute sternal fracture pain. The most common sternal fracture pattern is transverse which only requires treatment of four intercostal nerves, making cryoneurolysis feasible in trauma centers. This portable, minimally invasive, and low risk technique has the added benefits of reducing opioid requirements, decreasing length of hospital stay, and improving mobility in polytrauma patients.

Estimation of Age @ Death by Counting Number of Osteons from the Sternal RIB

Background: Identification of an individual becomes essential in a dead body more than when he is alive. Identitybecomes a problem in a dead person when the body is decomposed, mutilated, in skeletal remains or in masscausality death. The foremost essential thing in medico legal cases, becomes identity of the dead , rather thanopinion about the cause of death, time since death or manner of death. The aim of this study was to arrive at theregression formula for assessing the age of the dead, based on the number of osteons in the sternal rib bone.Methods : The study involved 41 sternal ribs taken from 20 to 50 years old persons from the south Indianpopulation at Institute of Forensic Medicine Department Madras Medical College. After autopsy a portion of ribbone was removed from the shaft of the fourth sternal rib near their anterior ends. A slide from the bone sectionwas placed in the light microscope to study the number of osteons in full thickness of the compact bone of the rib.Result & Conclusion: In this study, age was plotted in the X– axis and the number of osteons were plotted in theY – axis. A correlation coefficient (r) is derived. It summarizes the significance in the relationship of two variables.This study illustrates the estimation of age at death by counting the number of osteons in the rib bone from the agegroup of 20 to 48 years. It was proved that the number of osteons increases with age.

Sexing the sternal rib end in modern Greeks: A virtual osteometric approach using high-resolution 3D surface models.

Sex determination is one of the first biological attribute to be assessed when unidentified remains surface. In material of forensic interest, being able to use every skeletal element available for identification purposes is of paramount importance. The osteometric method from the sternal rib end has been found to generate accurate sex estimates, but as various studies have proved, all osteometric methods should be population-specific, as one equation does not fit all. The aim of this study is to assess sexual dimorphism in a contemporary Greek population sample of 68 males and 43 females, with the use of discriminant function analysis. The superior-inferior height (SIH) and anterior-posterior breadth (APB) from the third to fifth sternal rib ends of both sides were taken from 3D models created with the use of a hand-held 3D scanner. The results demonstrated that SIH is more sexually dimorphic than APB (alpha value of .05) while the application of İşcan's (1985) formula on the contemporary Greek sample, provided results of low accuracy, ranging from 48.6-52.4%. The cross-validated discriminant functions equations for the current sample, produced results ranging between 74.0-82.9% indicating that population-specific formulas produce results of higher accuracy, that are vital in cases of forensic interest.

The evolution of a chest wall injury and reconstruction clinic during a pandemic.

In 2019, we sought to develop a chest wall injury and reconstruction clinic (CWIRC) to treat patients with chest wall pain and rib fractures. This initiative was fueled by the recognition of an unmet need and evolving research demonstrating improved patient care and experience. We will describe the evolution of this clinic program from an acute care surgery/general surgery (ACS/GS) clinic to a CWIRC. We identified outpatient encounters generated from a general surgery clinic staffed by a physician and nurse practitioner team. A retrospective cohort review was performed to identify all outpatient encounters and surgeries associated with these encounters from January 1, 2017, to November 30, 2021. Outpatient and operative work relative value unit (wRVU) production as well as payer mix was compared as the primary outcome. Over this time period, the number of clinic interactions decreased (2017-284 vs. 2021-229). Clinic productivity increased however from 181 wRVUs in 2017 to 295 wRVUs in 2021. The CWIRC patient visits increased from 4% to 70%. In addition, telehealth visits increased from 0% to 23% of encounters. The operative wRVU productivity attributable to outpatient clinic visits increased (2017-253 vs. 2021-591). Combined, the CWIRC resulted in an overall growth of 104% in total wRVUs. The payer mixes for patients with rib diagnosis have a higher number of Blue Cross Blue Shield, Medicare, and Managed Care compared with ACS/GS. The most common diagnosis was rib fracture initial evaluation (37%), rib fracture subsequent encounter (25%), rib pain (24%), and flail chest initial evaluation (4%). The initiation of a CWIRC increased wRVU production despite a decrease in clinical encounters. These clinics may produce more wRVUs per encounter than ACS/GS clinics. An underserved population has been identified of chest wall pathology patients presenting for initial evaluation as outpatients. Further investigation into this concept is warranted to serve this population. Therapeutic/Care Management; Level IV.

Anatomofunctional comparison between the ribs of man and domestic animals

The objective was to compare the ribs in men, canines, horses and cattle, highlighting structural similarities in terms of functions, types, quantities and formats, using parts from the Human and Veterinary Anatomy Laboratory of the University of Franca, articles and books in this area of ​​expertise. Among the similar functions of the ribs, the support of the skeleton by participating in the formation of the rib cage, aid in respiratory movements and protection of organs stood out. As for the types, all species presented sternal ribs (articulating directly with the sternum) and sternal ribs (indirect contact with the sternum) in different amounts; on the other hand, only the canine and human, the floating ones (without connection with adjacent cartilage). The number of ribs corresponded to that of thoracic vertebrae, varying between species (13 pairs in the canine, 18 in the equine, 13 in the bovine and 12 in the human). Regarding the shape, there was variation according to each species, being longer, wider and flatter in cattle compared to horses; in canines more narrow and curved and in humans in semi-arches. It is possible to infer that, regardless of the species, the ribs perform the same functions, however, there are alternations in terms of types, quantities and formats, which may be involved with evolutionary and postural characteristics.

Postcranial skeletal pneumaticity in non-aquatic neoavians: Insights from accipitrimorphae.

Postcranial skeletal pneumaticity, air-filled bones of the trunk and limbs, is exclusive to birds among extant tetrapods and exhibits significant variation in its expression among different species. Such variation is not random but exhibits relationships with both body mass and locomotor specializations. Most species-level comparative research to date has focused on aquatic-oriented taxa (e.g., Anseriformes). The lack of data from non-aquatic birds constrains our ability to characterize global (i.e., avian-wide) patterns of this trait complex. To address this gap, the study conducted herein quantified postcranial pneumaticity in Accipitrimorphae, a mostly terrestrial clade composed of species that span a range of body sizes and exhibit diverse flight/foraging behaviors. All examined species (n=88) invariably pneumatized the postaxial through pre-caudal vertebrae, sternum, coracoid, humerus, vertebral and sternal ribs, and pelvic girdle, a pattern herein referred to as the accipitrimorph baseline. Of the 88 sampled species, 41 expanded upon this pattern, whereas 10 species exhibited a reduction. No species deviated from the accipitrimorph baseline by more than two anatomical regions. A phylogenetically-informed regression analysis failed to identify a significant relationship between body mass and pneumaticity. However, specific pneumaticity phenotypes deviating from the baseline were correlated with aspects of wing morphology, tail length, and home range size. Results from this and previous studies provide clarity on two hypotheses: (1) aquatic taxa display distinct pneumaticity expression patterns relative to non-aquatic birds, notably with reductions in the proportion of the skeleton filled with air in diving specialists and (2) contemporary comparative studies, including the one herein, that explicitly account for phylogenetic relationships consistently fail to support the oft-cited positive relationship between pneumaticity and body mass. Instead, historical relationships and functional/ecological attributes (e.g., diving, specialized flight behaviors) appear to be the primary drivers underlying patterns of variation in this trait complex.

Combined cardiac surgery in a Marfan syndrome patient with severe scoliosis via lower hemisternotomy: a case report

BackgroundScoliosis is one of the symptoms manifested by patients with Marfan syndrome (MFS). Deformity of the thoracic cavity due to severe scoliosis may cause difficulty during cardiac surgery in terms of the surgical approach and instrument manipulation; however, only a few reports have been available regarding the surgical case of MFS with severe scoliosis. Here, we report a case of combined aortic valve replacement and left atrial appendage closure in a patient with MFS who had severe scoliosis using lower hemisternotomy.Case presentationA 62-year-old female with MFS was referred to our hospital after being diagnosed with severe aortic regurgitation and paroxysmal atrial fibrillation with a history of cerebral thromboembolism. The aortic valve showed severe insufficiency due to cusp prolapse, whereas the aortic root was moderately dilated (42 mm). Echocardiography revealed severe regurgitation with reduced left ventricular ejection function (32%) and massive left ventricular diastolic dimension (88 mm). Moreover, combined aortic valve replacement and left atrial appendage closure was indicated. However, the patient had chest deformity due to severe scoliosis. Thus, conventional full sternotomy or thoracotomy was considered an inappropriate surgical approach. Lower hemisternotomy was selected on the basis of three-dimensional reconstruction imaging of the aorta, left atrial appendage, sternum, and rib. Sternal elevation and rib retraction with the costal arch folded back provided enough surgical field for the combined procedures to be safely conducted. The postoperative course was uneventful, except for predicted prolonged mechanical ventilation with the assistance of intraaortic balloon pumping. Thereafter, the patient has been free from any cardiac and cerebrovascular event.ConclusionsLower hemisternotomy can be useful for combined cardiac surgery in MFS with severe scoliosis.

805 Case Report: Atrial Perforation in the Setting of Electrical Injury and Subsequent Cardiopulmonary Resuscitation

IntroductionElectrical injuries cause 500 to 1000 deaths per year in the United States and are the fourth leading cause of death in the workplace. Rates and types of cardiac complication secondary to electrical injuries vary widely throughout the literature. Case reports describing cardiac perforation in the setting of electrical injury are exceedingly sparse. To our knowledge, there are no documented cases of cardiac perforation as a direct result of electrical injury.MethodsThis is a case report and review of relevant literature.ResultsCase Description:We present a case of myocardial perforation in the setting of high voltage electrical injury. An otherwise healthy 46-year old male sustained a 13.8 kV electrical. Resuscitation included bystander cardiopulmonary resuscitation (CPR), defibrillation by emergency medical responders, finger thoracostomies and massive transfusion protocol in the trauma bay, and finally emergent sternotomy and repair of two injuries to the right atrial appendage. Given this patient’s pattern of injury, including a sternal fracture and bilateral upper anterior rib fractures, the etiology of his right atrial perforation is more likely due to mechanical injury from CPR instead of thermal or electrical injury to the myocardium. However, intraoperative findings confound this theory as no defects were identified in the pericardium of the mediastinal pleura during the operation. This would argue against mechanical injury during CPR. However, the presence of a left hemothorax may could indicate that a pericardial injury was missed in the operation. We argue that the most likely cause of injury is mechanical perforation of the pericardium and myocardium during CPR with a possible missed pericardiotomy during surgical exploration. An alternative hypothesis is an isolated electrical injury to the myocardium and left hemothorax from rib fractures without communication between the two cavities. This patient expired on postoperative day two due to anoxic brain injury.ConclusionsThis case highlights myocardial injury as a rare but lethal complication of high voltage electrical injury and serves as a reminder that cardiac perforation and hemodynamic collapse due to hypovolemic shock can compound and complicate the resuscitation and management of a patient with electrical injury. Further, the widely varying data regarding cardiac complications secondary to electrical injury warrants further investigation and large-scale prospective data.

Double-layered two-directional somatopleural cell migration during chicken body wall development revealed with local fluorescent tissue labeling.

The thoracic ventral body wall consists of the rib, the sternum, the intercostal muscles, and the connective tissues surrounding them. The ribs and the intercostal muscles are derived from the somite. The connective tissues are derived from the somatic layer of the lateral plate mesoderm, somatopleure. The lateral growth of the somatopleure forms the primary ventral body wall. The migration of somitic cells into the somatopleure generates the secondary body wall. As the migrating behavior of the somatopleural cells during secondary body wall formation is still unclear, we investigate here the migratory behavior of the somatopleural cells in the thorax during chicken ventral body wall development by labeling the thoracic somatopleural cells one-somite-wide by DiI labeling or gene transfection of the enhanced green fluorescent protein and observe their distribution assisted by the tissue-clearing technique FRUIT. Our labeling experiments revealed the rostral migration of the somatopleural cells into a deep part of the thoracic body wall in embryonic day 6.5 chickens. For embryonic day 8.5 chickens, these deep-migrating somatopleural cells were found around the sternal ribs. Thus, we identified the double-layered two-directional migrating pathways of the somatopleural cells: the rostral migration of the deep somatopleural cells and the lateral migration of the superficial somatopleural cells. Our findings imply that the rostral migration of deep somatopleural cells and the lateral migration of superficial ones might be associated with the developing sternal ribs and the innervation of the thoracic cutaneous nerves, respectively.

PCR based method for sex estimation from bone samples of unidentified South African fetal remains

Fragmentary bone in disaster victim identification is reliant on a robust and objective method. Current methods employing traditional phenotypic analysis for sex estimation of forensic fetal remains are limited and often not possible due to the lack of distinctive cranial and pelvic traits. Thus, a molecular sex estimation method optimized for bone samples would enhance current techniques. Sternal rib samples were dissected from unclaimed perinatal decedents, presenting at varied stages of decomposition and unconfirmed circumstances of death, who were admitted to the Johannesburg Forensic Pathology Service (JFPS) and included in the Johannesburg Forensic Paediatric Collection (JFPC). A molecular protocol was designed and optimized using genomic DNA from SW480 cells and five individuals of unknown provenance and known sex (estimated during medicolegal autopsy) by targeting the X-linked G6PD and Y-linked SRY genes. The sex estimated at autopsy was confirmed using the optimized protocol. Nine (9) unidentified individuals were included and assigned sex based on the method described. The development of a sex typing protocol targeting the G6PD and SRY loci provides a new PCR method for sex estimation of human remains from 25 mg of bone fragment.

A new Heterodontosaurus specimen elucidates the unique ventilatory macroevolution of ornithischian dinosaurs.

Ornithischian dinosaurs were ecologically prominent herbivores of the Mesozoic Era that achieved a global distribution by the onset of the Cretaceous. The ornithischian body plan is aberrant relative to other ornithodiran clades, and crucial details of their early evolution remain obscure. We present a new, fully articulated skeleton of the early branching ornithischian Heterodontosaurus tucki. Phase-contrast enhanced synchrotron data of this new specimen reveal a suite of novel postcranial features unknown in any other ornithischian, with implications for the early evolution of the group. These features include a large, anteriorly projecting sternum; bizarre, paddle-shaped sternal ribs; and a full gastral basket - the first recovered in Ornithischia. These unusual anatomical traits provide key information on the evolution of the ornithischian body plan and suggest functional shifts in the ventilatory apparatus occurred close to the base of the clade. We complement these anatomical data with a quantitative analysis of ornithischian pelvic architecture, which allows us to make a specific, stepwise hypothesis for their ventilatory evolution.

Minimally invasive surgery for sternal and bilateral rib fractures

Sternal bone fractures with bilateral multiple rib fractures cause serious instability of the anterior chest wall, and prolonged mechanical ventilation may be required. A 45-year-old man was injured in a motor vehicle collision. He suffered from a bilateral flail chest injury accompanied by a transverse sternal fracture. Minimally invasive surgical stabilisation of the anterior chest wall was performed using two bars as per the Nuss procedure. Two days after surgery, he was extubated from artificial respiration and was ultimately discharged without any complications.

Guidelines for removal, preservation, and CT imaging of the syrinx, the avian vocal organ

While the state of the art has been described for recording bird songs and calls, there are no described best practices for collecting and preserving the avian vocal organ, the syrinx. In addition to skins and skeletal preparations, field collection of tissues for DNA sequencing has become a common practice. Protocols for such tissue collection often involve accessing internal organs. Here we argue that collecting syringes, which also involves accessing the chest cavity, adds only minimal time to field or skeletal preparation and can be done without damage to the skeleton. Collecting syringes will enable studies of structure–function relationships in the production of calls and song that have not been previously possible. Three-dimensional X-ray computed tomography (CT) imaging techniques allow new insight into these relationships, but material of both male and female birds as well as juveniles is lacking for most avian taxa. Here, we present a guide to the removal and preservation of the avian syrinx and associated vocal anatomy in hopes of increasing their representation in biological collections. In this guide, we suggest that taking in situ measurements is ideal since dissection, fixation, and tissue staining can affect measurements of certain airway features such as tracheal diameter and bronchial length. Our guidelines demonstrate that removing a single wing, shoulder, and half of the pectoral girdle from the dorsal side of the thorax along with disarticulating the sternal and vertebral rib segments on one side of the body allows exposure of the complete airway without damaging the skeleton. We also provide recommendations for fixation, storage, and staining of specimens in preparation for diffusible iodine-based contrast-enhanced computed tomography (diceCT) scans that allow imaging of both soft tissue structures such as vocal folds and muscles as well as the cartilaginous rings that support these structures.

Structure and possible ventilatory function of unusual, expanded sternal ribs in the Early Cretaceous bird Jeholornis

Many specimens of the basal bird Jeholornis from the Early Cretaceous Jehol Biota of northeast China include one or two distinctive paddle-shaped skeletal elements preserved in the thoracic region. These ossifications have generally been identified as lateral trabeculae, paired processes of the sternum that are common within the derived avian clade Ornithothoraces. In extant birds, lateral trabeculae define membrane-filled embayments or fenestrae in the caudal portion of the sternum that contribute to the area available for attachment of the pectoralis musculature, which drives the downstroke in flight. The presence of lateral trabeculae in Jeholornis would thus suggest a proportionally larger M. pectoralis, and a more powerful downstroke, than in other non-ornithothoracine avians. However, previously undescribed specimens of Jeholornis reveal that the paddle-shaped elements are actually anomalously expanded sternal ribs, the caudalmost of four pairs in the ribcage. Accordingly, lateral trabeculae are absent in Jeholornis, dovetailing with other evidence that basal birds lack many components of the sophisticated flight apparatus typical of ornithothoracines. The expanded sternal ribs represent a striking, and somewhat functionally enigmatic, autapomorphy of Jeholornis. In many pterosaurs the sternal ribs bear multiple small prominences, the sternocostapophyses, that probably improved the mechanical advantage of ribcage musculature involved in ventilation and increased the area for muscle attachment. The sternal rib expansions seen in Jeholornis presumably served a similar purpose, and are among a suite of derived features of this taxon that appear to represent adaptations for the demands of powered flight but only partially parallel those independently acquired by ornithothoracines.

A new enantiornithine (Aves: Ornithothoraces) with completely fused premaxillae from the Early Cretaceous of China

We report a new small enantiornithine, Shangyang graciles gen. et sp. nov., based on a nearly complete and articulated skeleton from the Lower Cretaceous Jiufotang Formation of Liaoning Province, north-eastern China. Shangyang has premaxillae that are completely fused rostrally as well as along the frontal processes, a previously unrecognized condition in Early Cretaceous birds. As in three other enantiornithine taxa, Shangyang preserves a pair of craniolateral processes in the sternum. Phylogenetic analysis places Shangyang in a relatively derived position within Enantiornithes, suggesting that the craniolateral processes of the sternum evolved independently among some enantiornithine lineages from the condition seen in some basal ornithuromorphs. The craniolateral processes in modern birds provide the insertions of the M. sternocoracoideus that functions in the downstroke, which can also originate from the two cranialmost sternal ribs instead when these processes are absent. The altered origin of this muscle shows that diverse pectoral musculoskeletal modifications took place early in avian history.http://zoobank.org/urn:lsid:zoobank.org:pub:20C69B6A-473B-4C6D-9672-F5B2CC2D8FE1