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Two new families and three new genera and species of Crinoidea from the Icla and Belén formations, Bolivian Devonian, are described. The material is identified as Meperocrinus angelina n. gen. n. sp., from the Icla Formation of the Sub-Andina region, Tuberocrinus lapazensis n. gen. n. sp. and Aenigmaticumcrinus rochacamposi n. gen. n. sp., both from the Belén Formation of the Bolivian Altiplano. Meperocrinus angelina n. gen. n. sp. is an Emperocrinidae, a family described from the Silurian of the United States of America. Tuberocrinus lapazensis n. gen. n. sp. is assigned to a new family of Dimerocrinitacea, the Tuberocrinidae n. fam., which is closely related to Pterinocrinidae that already has representatives in Bolivia (Apurocrinus sucrei McIntosh), Argentina (Pterinocrinus? australis Haude), and Colombia (Bogotacrinus scheibei McIntosh). Aenigmaticumcrinus rochacamposi n. gen. n. sp. is also as assigned to a new family of Dimerocrinitacea, the Aenigmaticumcrinidae n. fam.; a family with very distinctive features. These data demonstrate that the Malvinokaffric crinoid fauna in Bolivia has a mixed origin, with forms that arrived in South America from Europe (Old World Realm) and United States of America (Eastern America Realm) during the late Silurian or earliest Devonian, as well as a local stock, which evolved to highly endemic lineages.
Embolic ischemic strokes cause significant mortality and morbidity worldwide. It has been proposed that some of these strokes are due to unstable carotid plaques with intraplaque hemorrhage (IPH) but a low overall degree of stenosis. Our aim was to test a fat-saturated T1-weighted (T1WI) black-blood sequence on MRI for the detection of IPH in symptomatic individuals and to quantify the relation between IPH, severity of stenoses, and ischemic brain lesions.
Materials and Methods:
Sixty-two patients were examined by 3T MRI. Sequences included brain diffusion-weighted imaging (DWI) as well as 3D turbo spin echo (TSE) fat-saturated black-blood T1 of the carotid bifurcations, to detect IPH as a focal intraplaque hyperintensity. Both carotid arteries were analyzed in each patient. The North American Symptomatic Carotid Endarterectomy Trial scale was used for quantification of stenosis degree.
Thirty-six out of 62 patients (mean age, 74) showed brain ischemia on DWI. Fifteen of these 36 patients (42%) had associated ipsilateral IPH at the carotid bifurcation or the proximal internal carotid artery. Mean degree of stenosis in this group was 50%. In 21 patients with ischemia without IPH, the mean degree of stenosis was 44%.
MRI with 3D TSE fat-saturated black-blood T1 technique is a safe, reliable, and noninvasive tool for the detection of IPH. A high percentage (42%) of ischemic events in patients with low- to moderate-degree stenosis were associated with IPH, an easily detectable imaging biomarker of plaque vulnerability. The ability to confirm IPH by MRI may help stratify patients into different risk and treatment groups in the future.
A new Saldidae (MCT 6959-I) from the Crato Formation (Lower Cretaceous, late Aptian), Santana Group, Araripe Basin (northeastern Brazil) is described and illustrated. Olindasalda gondwanica n. gen. n. sp. is the first fossil Saldidae recorded from the Gondwanan supercontinent. The new genus can be distinguished from other members of the subfamily Chiloxanthinae by its small (4.49 mm) and oval-elongated body, absence of spots on the corium of the hemelytron, long R vein, and much-reduced first cell of the membrane. Remarks on the geology of the type locality and a comparison of the new genus with other saldids are provided.
This chapter examines the role of selection in driving certain aspects of pelvic morphology, particularly the differences between mediolateral breadths and anteroposterior breadths. The chapter is divided into three sections, representing the three key selection pressures researchers have spent the most time on – namely, obstetrics, locomotion and thermoregulation. Data for the role of each of these on pelvic morphology are considered, as is discussion of the myriad ways human populations have mixed and matched morphological traits to manage these selection pressures. Clearly, there is not a single strategy for handling the interactive nature of these pressures.
In this chapter, we discuss evidence about the evolutionary forces that have shaped the evolution of the human pelvis, both in its entirety as well as portions of the pelvis, focusing on studies that have investigated pelvic evolution using experimental and quantitative genetic methods. These methods are tied to information from Chapter 4 about pelvis development, with emphasis placed on the importance of understanding the difficulty of tying development and growth with evolutionary processes. Special attention is placed on the concept of the palimpsest. Further, we review these findings in light of three principal hypotheses broadly offered about the processes that selected for pelvic shape (as reviewed in Chapters 2 and 3): locomotion, obstetric sufficiency and thermoregulation. We show from multiple studies that the human pelvis evolved in response to natural selection as well as through neutral evolutionary processes (e.g. genetic drift). A key conclusion from these studies is that parts of the pelvis evolved in different manners in response to these (and other) selection factors; thus, the shape of the human pelvis reflects a modular response to various sources of selection.
This chapter provides an overview of the anatomy of the primate pelvis, with a particular focus on the features of the hominoid (ape) and human pelvic morphologies. Underlying sources of morphological variation such as phylogenetic signals, sexual dimorphism and obstetric function are examined, as well as general patterns of pelvic anatomical variation within Homo sapiens.
In light of the various sources of evidence presented in the preceding chapters, we are left to conclude that the human (in the broadest sense of recent humans and their ancestors) pelvis represents various experiments in evolution. A diversity in pelvic sizes and shapes has marked hominin history, as each population and each species responded to selection pressures in sometimes unique and sometimes convergent ways. These were situated in the distinctive population histories of each of these groups, creating a mosaic of patterns underlain both by responses to evolution and changing patterns of covariance within development. To understand the diversity we observe among fossils, as well as variation within recent humans, we must therefore cultivate a multidisciplinary expertise in biomechanics, kinematics, fossil evidence, developmental biology and evolutionary theory. This book represents an attempt at bringing together these various sources of evidence to better understand the factors, patterns and potential processes that shaped the evolution of the pelvis.
Even before the focus on bipedalism as the ‘hallmark’ of the human lineage (Robinson, 1972), interest in the pelvis was stimulated by discussions across different disciplines, including the growing field of obstetrics (see review in Walrath, 2003), as well as by multiple fossil discoveries (Pycraft, 1930; Dart, 1949). It was also clear at the outset that the pelvis was going to serve as a crucial part of the evolutionary history of humans, given that it had obvious functional implications in its role in locomotion, which included dramatic differences between other species grouped with humans taxonomically and then phylogenetically, including the African and Asian apes.
To investigate pelvis evolution and to understand the sources of its variation, we must comprehend its development. We review developmental processes that form the pelvis from three perspectives: cell layers and tissues, genomic information and overall growth. At tissue level, the pelvis forms largely from lateral plate mesoderm as well as from somites. The os coxa forms from cartilaginous precursor tissues that grow and ossify, especially in two major regions that become the ischiopubis and the ilium. The sacrum and coccyx form from multiple ossification centres. Numerous secondary ossification centres form, with the last fusing by the mid-twenties. The importance of multiple genes and molecular factors are discussed, including interactions among and differences in timing and locations of expression, emphasising Islet1, Emx2, Pbx and Hox. We review the importance of differences in timing of ossification among skeletal elements, their interactions with mechanical loading and sex hormones, and environmental factors affecting individual growth. These processes are linked to morphological integration and are the origins of the morphological variation on which evolutionary forces act.
This chapter examines the fossil record of hominoid and hominin pelvic remains from the Miocene through to the Late Pleistocene. The interpretation of functional demands shaping hominin pelvic morphology including locomotion, obstetrics and thermoregulation are discussed, as well as evidence for pelvic sexual dimorphism in hominin species. The long-standing view of a relatively linear pattern of hominin pelvic evolution from Australopiths, through early Homo, to Neanderthals, broken only by the appearance of the somewhat divergent morphology of Homo sapiens is examined in light of recent fossil pelvis discoveries that point to greater diversity in the hominin pelvic morphology. These fossils add to evidence from elsewhere in the postcranium that indicate there were multiple ways to be a bipedal hominin.
This book provides a synthetic overview of all evidence concerning the evolution of the morphology of the human pelvis, including comparative anatomy, clinical and experimental studies, and quantitative evolutionary models. By integrating these lines of research, this is the first book to bring all sources of evidence together to develop a coherent statement about the current state of the art in understanding pelvic evolution. Second, and related to this, the volume is the first detailed assessment of existing paradigms about the evolution of the pelvis, especially the obstetric dilemma. The authors argue that there are many 'dilemmas', but these must be approached using a testable methodology, rather than on the proviso of a single paradigm. The volume clearly contributes to greater scientific knowledge about human variation and evolution, and has implications for clinicians working within reproductive health. A thought-provoking read for students, researchers and professionals in the fields of biological anthropology, human evolutionary anthropology, paleoanthropology, bioarchaeology, biology, developmental biology and obstetrics.
Experimental evidence for the formation of hydrogenated fullerene molecules is presented. Films of C60 were grown on a highly oriented pyrolytic graphite (substrate) and exposed to a beam of deuterium atoms. Thermal desorption combined with mass spectrometry was used to determine the deuterated fullerene products formed, revealing a maximum degree of deuteration corresponding to C60D36. Release of D2 from the deuterated C60 film occurs at a much higher temperature than for D-saturated graphite.
Reactions on carbonaceous surfaces play an important role in processes such as H2 formation in the interstellar medium. We have investigated the adsorption of C2 molecules on a highly oriented pyrolytic graphite (HOPG) surface and then exposed them to a beam of deuterium atoms in order to investigate the formation of deuterated fullerenes. Scanning tunneling microscopy (STM) was used to probe the adsorbed molecules and their deuteration. Deuteration of C2 films results in increased thermal stability of the film, relative to films of pristine C2, along with an evolution towards higher deuterated species. The STM data provide confirmatory evidence for the formation of deuterated fullerene species.