Dietary hardness, loading behavior, and the evolution of skull form in bats

The morphology and biomechanics of the vertebrate skull reflect the physical properties of diet and behaviors used in food acquisition and processing. We use phyllostomid bats, the most diverse mammalian dietary radiation, to investigate if and how changes in dietary hardness and loading behaviors during feeding shaped the evolution of skull morphology and biomechanics. When selective regimes of food hardness are modeled, we found that species consuming harder foods have evolved skull shapes that allow for more efficient bite force production. These species have shorter skulls and a greater reliance on the temporalis muscle, both of which contribute to a higher mechanical advantage at an intermediate gape angle. The evolution of cranial morphology and biomechanics also appears to be related to loading behaviors. Evolutionary changes in skull shape and the relative role of the temporalis and masseter in generating bite force are correlated with changes in the use of torsional and bending loading behaviors. Functional equivalence appears to have evolved independently among three lineages of species that feed on liquids and are not obviously morphologically similar. These trends in cranial morphology and biomechanics provide insights into behavioral and ecological factors shaping the skull of a trophically diverse clade of mammals.     

The evolutionary and morphological history of the parasphenoid bone in vertebrates

The parasphenoid is located in the cranium of many vertebrates. When present, it is always an unpaired, dermal bone. While most basal vertebrates have a parasphenoid, most placental mammals lack this element and have an unpaired, dermal vomer in a similar position (i.e. associated with the same bones) and with a similar function. As such, the parasphenoid and the vomer were considered homologous by some early twentieth century researchers. However, others questioned this homology based on comparisons between mammals and reptiles. Here we investigate the parasphenoid bone across the major vertebrate lineages (amphibians, reptiles, mammals and teleosts) including both developmental and evolutionary aspects, which until now have not been considered together. We find that within all the major vertebrate lineages there are organisms that possess a parasphenoid and a vomer, while the parasphenoid is absent within caecilians and most placental mammals. Based on our assessment and Patterson's conjunction tests, we conclude that the non‐mammalian parasphenoid and the vomer in mammals cannot be considered homologous. Additionally, the parasphenoid is likely homologous between sarcopterygian and actinopterygian lineages. This research attempts to resolve the issue of the parasphenoid homology and highlights where gaps in our knowledge are still present.     

Testing hypotheses about tinkering in the fossil record: the case of the human skull

Efforts to test hypotheses about small-scale shifts in development (tinkering) that can only be observed in the fossil record pose many challenges. Here we use the origin of modern human craniofacial form to explore a series of analytical steps with which to propose and test evolutionary developmental hypotheses about the basic modules of evolutionary change. Using factor and geometric morphometric analyses of craniofacial variation in modern humans, fossil hominids, and chimpanzee crania, we identify several key shifts in integration (defined as patterns of covariation that result from interactions between components of a system) among units of the cranium that underlie the unique shape of the modern human cranium. The results indicate that facial retraction in modern humans is largely a product of three derived changes: a relatively longer anterior cranial base, a more flexed cranial base angle, and a relatively shorter upper face. By applying the Atchley-Hall model of morphogenesis, we show that these shifts are most likely the result of changes in epigenetic interactions between the cranial base and both the brain and the face. Changes in the size of the skeletal precursors to these regions may also have played some role. This kind of phenotype-to-genotype approach is a useful and important complement to more standard genotype-to-phenotype approaches, and may help to identify candidate genes involved in the origin of modern human craniofacial form.     

Morphogenesis of the cranium of Cavia porcellus L. II: Comparative part and literature

The development of the chondrocranium of Cavia porcellus is compared to those of other rodents. The tectum posterius of the investigated rodents is orientated vertically. This position is functionally caused by the attachment of the muscles of the neck and shoulder girdle. The paracondylar process is a typical feature of rodents although absent in Mesocricetus. Only in Cavia and Tatera, the connection between the lamina supraoccipitalis and the auditory capsule-the supraoccipitocapsular commissure-is missing. Youssef's (1966) generalization that the course of the notochord in rodents is of transbasal type cannot be confirmed. In Cavia, the auditory capsule is connected with the occipital region only by the exoccipitocapsular commissure. The connection between auditory capsule and basal plate is established by the alicochlear and the anterior basicapsular commissures. In comparison to other rodents, the number of commissures in Cavia is reduced. In rodents, there is always a subarcuate fossa which in later stages of development is filled out by the flocculus cerebelli. In contrary to Rajtova's (1972a) statement, Cavia shows a suprafacial commissure as all mammals do (Reinbach 1952). As the tegmen tympani is absent in Otomys and Erethizon, it is not a typical rodent feature. The carotid foramen is well developed in Cavia but the internal carotid artery obliterates until the 25 mm CRL-stage. In embryonic rodents, the ala temporalis may have a foramen ovale but not a foramen rotundum. During ontogeny rodents show the ala hypochiasmatica for the attachment of the straight muscles of the eyeball. In Cavia the ala hypochiasmatica develops independently and fuses with the postoptic root of the ala orbitalis in later stages. In myomorphs and sciumorphs, the orbitoparietal and orbitonasal commissures are present. Only in caviomorphs this part of the primary sidewall of the skull is uncomplete. Erethizon, however, shows an orbitonasal commissure whereas in Cavia both commissures are missing. In this respect the guinea-pig resembles the condition of primates. There is no interorbital septum in rodents. The nasal capsule of rodents contains 1 atrioturbinal, 1 maxilloturbinal, 1 nasoturbinal, and at least 3 ethmoturbinals. Due to the strong development of the alveoli of the incisors, the maxilloturbinale is flected in the caviomorphs. The epiphanial foramina are present. The lamina transversalis anterior is continuous with the nasal septum so that there is a complete zona anularis in rodents. The paraseptal cartilages are continuous with the lamina transversalis anterior but not with the lamina transversalis posterior.(ABSTRACT TRUNCATED AT 400 WORDS)     

大荔颅骨的测量研究

本文报道大荔颅骨的一系列测量数据, 并且将其与中国, 欧洲和非洲的中更新世人类的相应数据进行比较, 发现大荔颅骨的测量数据大多没有超出中国和欧洲/非洲中更新世人的变异范围, 有的与中国中更新世人接近, 有的与欧洲和/或非洲标本更加接近。本文将这些结果与大荔颅骨的与中国古人类共同具有的其他测量和观察特征进行综合考虑, 建议大荔人群属于中国古人类连续进化链中的一员, 并且表现出中国古人类与欧洲和非洲古人类之间基因交流的形态证据。     

Evolution and development of the vertebrate skull: The role of pattern formation

The vertebrate skull is anatomically complex and phylogenetically diverse; it presents unique opportunities to examine the role of developmental processes in evolutionary change. Previous studies have largely examined phylogenetic trends in tissue composition or change in the timing of developmental events (heterochrony). Additional important insights may be gained if skull evolution and development are viewed from the standpoint of pattern formation. Contemporary models of pattern formation offer the possibility of linking developmental mechanisms of cranial morphogenesis from the level of genes, through cell biology, to adult form.     

Morphology of the regiones ethmoidalis and orbitotemporalis in Galea musteloides Meyen 1832 and Kerodon rupestris (Wied-Neuwied 1820) (Rodentia: Caviidae) with comments on the phylogenetic systematics of the Caviidae

The present study describes the fetal regions ethmoidalis and orbitotemporalis of the cranium of Galea musteloides and Kerodon rupestris and compares them with Galea spixii and Cavia porcellus . The fetal crania of these representatives of the Caviinae were serially sectioned and 3D plate reconstructions were built. For a broader scope, serially sectioned heads of the caviomorph taxa Hydrochaeris hydrochaeris and Dasyprocta leporina were also examined. The ethmoidal and orbitotemporal regions of the cranium provides characters that are pertinent to the discussion of systematics of the Caviinae. Nine cranial characters were identified as being significant and discussed phylogenetically. Taking the monophyly of the Cavioidea as given, two characters are autapomorphic for the genus Galea: the reduction of the crista semicircularis and the lacrimale forming the 'arco antorbitario' (Kraglievich 1930). Cavia is the sister group of Galea; synapomorphic characters are the extent of the processus palatinus medialis of the praemaxillare and the presence lamina pterygoidea of the alisphenoid. There were no apomorphic characters of the structural complexes examined that could support the Caviinae. The reduced and nonperforated alisphenoid is an autapomorphic feature of the Caviidae. The division of the nasoturbinale is evidence for a sistergroup relationship of the Hydrochaeridae and the Caviidae. Autapomorphic characters for the Cavioidea include the ventrolateral opening of the organon vomeronasale and the lateral prolongation of the lacrimale.     

Developmental stress and cranial hypostosis by epigenetic trait occurrence and distribution: an exploratory study on the Italian Neandertals

The occurrence and distribution of 35 cranial epigenetic traits in the Italian Neandertals (Saccopastore 1 and 2, Guattari 1) were examined according to morpho-functional cranial regions and with respect to a distinction between hypostosis (i.e., weak osseous development, arrested morphogenesis, retention of infantile features) and hyperostosis (i.e. excess of ossification, not reaching the pathological condition). The results, expressed ashypostotic scores, showed higher levels of hypostosis in these Neandertal specimens than in recent European samples. The highest expressions of hypostotis were observed in those regions of the Neandertal cranium where disequilibrium between skeletal and cerebral growth factors was expected. These results—interpreted as expression of developmental stress—are consistent with a heterochronic interpretation of the development of the Neandertal cranium; namely, a faster ossification of the cranial vault relative to brain growth rates.     

Construction and characterization of a high activity mutant of human keratinocyte growth factor-2

Keratinocyte growth factor-2 (KGF-2) plays an important role in vertebrate limb development, lung branching morphogenesis, regeneration and reconstruction of the epidermis. Previous studies have used the wild type factor. Here, we have constructed a double-site mutant of human KGF-2, named STEA. STEA possesses higher receptor binding affinity and promotes better proliferation activity on rat tracheal epithelium (RTE) cells than recombinant human KGF-2. These results suggest that the simultaneous mutation of Ser115 to Thr and Glu117 to Ala improves the biological activity of KGF-2.     

Studies on the skull of the Indian sisorid catfish, Erethistes pussilus

The skull of Erethistes pussilus is described in detail. The general disposition of the bones corresponds to the siluroid pattern. Among the siluroid fishes, E. pussilus approaches the advanced forms in certain features such as obliteration of myodomic space, edentulous palate, absence of entopterygoids and supratemporals, intimate sutural articulation of posttemporals and complex vertebra with the cranium, diminished cranial cavity and loss of sutural articulation among the palatopterygoquadrate elements. In certain characters like the hyomandibula exclusively supported from the sphenotic, solitary hypohyal on each hyoid cornu, absence of interhyals, reduced orbits, edentulous vomer, small gape of mouth, toothless ectopterygoid and in the small number of branchiostegals, E. pussilus stands specialized alone among the catfishes. A diagnosis of the salient cranial characters of the fish is given and its relationship discussed.     

Studies on the skull of the Indian sisorid catfish, Erethistes pussilus

The skull of Erethistes pussilus is described in detail. The general disposition of the bones corresponds to the siluroid pattern. Among the siluroid fishes, E. pussilus approaches the advanced forms in certain features such as obliteration of myodomic space, edentulous palate, absence of entopterygoids and supratemporals, intimate sutural articulation of posttemporals and complex vertebra with the cranium, diminished cranial cavity and loss of sutural articulation among the palatopterygoquadrate elements. In certain characters like the hyomandibula exclusively supported from the sphenotic, solitary hypohyal on each hyoid cornu, absence of interhyals, reduced orbits, edentulous vomer, small gape of mouth, toothless ectopterygoid and in the small number of branchiostegals, E. pussilus stands specialized alone among the catfishes. A diagnosis of the salient cranial characters of the fish is given and its relationship discussed.     

Jaw muscles and the skull in mammals: the biomechanics of mastication.

Among non-mammalian vertebrates, rigid skulls with tight sutural junctions are associated with high levels of cranial loading. The rigid skulls of mammals presumably act to resist the stresses of mastication. The pig, Sus scrofa, is a generalized ungulate with a diet rich in resistant foods. This report synthesizes previous work using strain gages bonded to the bones and sutures of the braincase, zygomatic arch, jaw joint, and mandible with new studies on the maxilla. Strains were recorded during unrestrained mastication and/or in anesthetized pigs during muscle stimulation. Bone strains were 100-1000 micro epsilon, except in the braincase, but sutural strains were higher, regardless of region. Strain regimes were specific to different regions, indicating that theoretical treatment of the skull as a unitary structure is probably incorrect. Muscle contraction, especially the masseter, caused strain patterns by four mechanisms: (1) direct loading of muscle attachment areas; (2) a compressive reaction force at the jaw joint; (3) bite force loading on the snout and mandible; and (4) movement causing new points of contact between mandible and cranium. Some expected patterns of loading were not seen. Most notably, strains did not differ for right and left chewing, perhaps because pigs have bilateral occlusion and masseter activity.     

3D虚拟复原精度的差异对头骨测量数值的影响——以Mimics软牛为例

近年来,根据三维软件虚拟复原的头骨来获取测量数据的方法被越来越多地应用在古生物,特别是古人类学的研究中,然而对于三维软件不同精度虚拟复原的头骨,其测量数值是否有差异,研究者并不是很清楚。本文以Mimics软件为例,根据其复原模型简化规则,选择未精简的最佳精度模型作为标准进行配对t检验或非参数检验,通过对43例云南人头骨的顶骨矢状弦长、颅周长、头盖部面积、乳突小房表面积、颅容量、乳突小房体积等六个测量项目的对比和分析,对Mimics软件低、中、高、最佳四种精度3D虚拟复原头骨间的测量差异进行了研究。结果显示：颅周长、头盖部面积、颅容量、乳突小房体积四项的所有简化精度模型的测量数据均与最佳精度模型测量数据的差异具有显著性;而除高精度组外,顶骨矢状弦长及乳突小房表面积的其余精度组测量数据均与最佳精度组差异具有显著性;此外,顶骨矢状弦长、颅周长、头盖部面积、颅容量的简化精度与最佳精度的测量差异占比均小于3%.而乳突小房表面积的低精度与最佳精度测量差异占比可超过50%,乳突小房体积的低精度与最佳精度测量差异占比可超过120%。这一结果提示我们,在测量Mimics复原的三维模型时,体量大差异小的测量项可以在较低精度的复原模型上进行测量;而对头骨内部腔窦这样体量小表面粗糙的结构,复原模型的精度选择及测量数据比较需要格外谨慎。     

Evidence for the neural crest origin of turtle plastron bones

Summary: The migrating cranial neural crest cells of birds, fish, and mammals have been shown to form the membranous bones of the cranium and face. These findings have been extrapolated to suggest that all the dermal bones of the vertebrate exoskeleton are derived from the neural crest ectomesenchyme. However, only one group of extant animals, the Chelonians, has an extensive bony exoskeleton in the trunk. We have previously shown that the autapomorphic carapacial and plastron bones of the turtle shell arise from dermal intramembranous ossification. Here, we show that the bones of the plastron stain positively for HNK‐1 and PDGFRα and are therefore most likely of neural crest origin. This extends the hypothesis of the neural crest origin of the exoskeleton to include the turtle plastron. genesis 31:111–117, 2001. © 2001 Wiley‐Liss, Inc.     

A small skull from Flores dated to the 20th century

A human skull with mandible from the Ngada District on the island of Flores, Indonesia, is described in order to contribute to the knowledge of variation in cranial architecture, which is important in interpretations of evolutionary cerebralisation. The skull was excavated in 1924 and sent to the National Museum in Copenhagen. The “Copenhagen Flores” (CF) male skull is radiocarbon-dated and of modern age. The cranium is small, but larger than e.g. Liang Bua skull (LB1) in every measurement. The (CT-scan based) cranial capacity of 1258 ml is normal for modern humans, but somewhat lower than values from the middle or upper Palaeolithics. The metric cranial data analysed in FORDISC, characterize the skull as a male Vietnamese rather than a Chinese or White individual. Tooth morphology shows the sundadont pattern and tooth size corresponds to that of teeth from Bali, Java and Malayan Orang Asli. Remarkable are the marked asymmetries in the dentition with rotation of an upper premolar and congenital absence of a third molar. In these respects the CF skull is similar to dentitions belonging to the pygmoid villagers of Rampasasa, a village not far from the Liang Bua cave, and to LB1.