The uniqueness of Daubentonia

The aberrant features of the genus Daubentonia, such as the superficially rodent-like dentition, the globose and foreshortened brain case, and the filiform third manual digit have long been known. But the current assessment of the genus as lemuriform, and within that group as closest to the indriids, depends upon greater weight being placed upon other characteristics such as the cranial arterial pattern, the molariform teeth, and the developmental characteristics of the dentition. Prior multivariate morphometric studies have shown that though the shoulder structure of Daubentonia is uniquely different from that of all other primates, the structure of its pelvis may not be especially different from that of many relatively non-specialized primates. A large series of studies have been summated here in which many different anatomical regions (shoulder, arm, forearm, forelimb as a whole, pelvis, femur, hindlimb as a whole, forelimb and hindlimb combined, and total bodily proportions including limbs, trunk, and head) have been characterized osteometrically in a wide range of primate genera. The resulting data sets have been studied by discriminant function analyses. The differences that have been found are large enough that it can be confidently asserted that in its postcranial skeleton, Daubentonia is more different from the primates as a whole than is any other primate genus. These differences are big enough that their statistical and biological significance is not at all in doubt, notwithstanding the very small numbers of available specimens of this rare genus. They are so great that functional implications exist though they cannot, in our present state of knowledge of the habits of the genus, be ascribed with any certainty. They are so great indeed, paralleling the enormous differences of Daubentonia from other primates in its dentition, skull and cheiridia, that we may prefer to keep open minds about its taxonomic placement.     

Aegyptopithecus endocasts: oldest record of a pongid brain

Incomplete endocasts of Aegyptopithecus, one of the oldest known pongids. indicate that by 26 to 28,000,000 years ago the pongid brain was advanced over that of most prosimians in having relatively more visual cortex, relatively smaller olfactory bulbs and a well developed central sulcus, and in being relatively larger. The brain of Aegyptopithecus was more primitive than that of modern anthropoids in having a relatively smaller frontal lobe. The brain of Aegyptopithecus was relatively long and low, like that of Alouatta, but unlike that of most other anthropoids; that difference in shape may be the result of allometric factors, or may reflect retention of primitive cranial features in Aegyptopithecus.     

Cranial anatomy of Shunosaurus, a basal sauropod dinosaur from the Middle Jurassic of China

Shunosaurus, from the Middle Jurassic of China, is probably the best‐known basal sauropod and is represented by several complete skeletons. It is unique among sauropods in having a small, bony club at the end of its tail. New skull material provides critical information about its anatomy, brain morphology, tooth replacement pattern, feeding habits and phylogenetic relationships. The skull is akinetic and monimostylic. The brain is relatively small, narrow and primitively designed. The tooth replacement pattern exhibits back to front replacement waves in alternating tooth position. The teeth are spatulate, stout and show well‐developed wear facets indicative of coarser plant food. Upper and lower tooth rows interdigitate and shear past each other. Tooth morphology, skull architecture, and neck posture indicate that Shunosaurus was adapted to ground feeding or low browsing. Shunosaurus exhibits the following cranial autapomorphies: emargination of the ventral margin of the jugal/quadratojugal bar behind the tooth row; postorbital contains a lateral pit; vomers do not participate in the formation of the choanae; pterygoid is extremely slender and small with a dorsal fossa; quadrate ramus of the pterygoid is forked; quadratojugal participates in the jaw articulation; tooth morphology is a combination of cylindrical and spatulate form; basipterygoid process is not wrapped by the caudal process of the pterygoid; trochlear nerve has two exits; occlusal level of the maxillary tooth row is convex downward, whereas that of the dentary is concave upward, acting like a pair of garden shears; dentary tooth count is 25 or more; and the replacing teeth invade the labial side of the functional teeth. Cranial characters among the basal sauropods are reviewed. As Shunosaurus is the earliest sauropod for which cranial remains are known, it occupies an important position phylogenetically, showing the modification of skull morphology from the prosauropod condition. Although the skull synapomorphies of Sauropoda are unknown at present, 27 cranial synapomorphies are known for the clade Eusauropoda. © 2002 The Linnean Society of London, Zoological Journal of the Linnean Society, 2002, 136 , 145?169.     

The erectile cheek-spine apparatus in the bristlenose catfish Ancistrus (Loricariidae, Siluriformes), and its relation to the formation of a secondary skull roof

In the South American catfish family Loricariidae, the opercle has been decoupled from the lower jaw, and has also lost its function in expiration. While many loricariid species have a small and slightly mobile opercle with reduced opercular musculature, within the hypostomine subfamily a novel opercular mechanism has developed that erects a tuft of enlarged odontodes anterior to the opercle. This defensive mechanism is examined in Ancistrus cf. triradiatus. The opercle has a prominent anterior process and the orientation of the reinforced articulation hinge to the hyomandibular bone has shifted. The opercular musculature is well developed, with a hypertrophied dilatator operculi that extends deep inside the skull roof bones and toward the midline, over the brain, but below the superficial skull roof. Hence the frontal, sphenotic, parieto-supraoccipital and compound pterotic bones consist of a dorsal, superficial part and a deeper part separating the brain from the muscle: two functional skull roofs are thus formed. The impact on the path of the cranial sensory canals is substantial, moving canals away from the skull surface. Hypertrophy of cranial muscles is known from many teleosts, but the invasion of such large muscles into the skull, which is drastically modified and literally hollowed out, has never been described before. These cranial modifications are greater in males than in females, related to the territorial behavior of the former, in which the erectile spines are usually used.     

Multiple calvarial defects in lmx1b mutant mice

The vertebrate cranial vault, or calvaria, forms during embryonic development from cranial mesenchyme of multiple embryonic origins. Inductive interactions are thought to specify the number and location of the calvarial bones, including interactions between the neuroepithelium and cranial mesenchyme. An important feature of calvarial development is the local inhibition of osteogenic potential which occurs between specific bones and results in the formation of the cranial sutures. These sutures allow for postnatal growth of the skull to accommodate postnatal increase in brain size. The molecular genetic mechanisms responsible for the patterning of individual calvarial bones and for the specification of the number and location of sutures are poorly understood at the molecular genetic level. Here we report on the function and expression pattern of the LIM-homeodomain gene, lmx1b, during calvarial development. Lmx1b is expressed in the neuroepithelium underlying portions of the developing skull and in cranial mesenchym which contributes to portions of the cranial vault. Lmx1b is essential for proper patterning and morphogenesis of the calvaria since the supraoccipital and interparietal bones of lmx1b mutant mice are either missing or severely reduced. Moreover, lmx1b mutant mice have severely abnormal sutures between the frontal, parietal, and interparietal bones. Our results indicate that lmx1b is required for multiple events in calvarial development and suggest possible genetic interaction with other genes known to regulate skull development and suture formation. Dev. Genet. 22:314–320, 1998. © 1998 Wiley-Liss, Inc.     

Cranial morphology and adaptations in Eocene Adapidae. II. The Cambridge skull of Adapis parisiensis

One of the most complete skulls of the early primate Adapis parisiensis is in the collection of the Department of Zoology, Cambridge University. This exceptionally well-preserved male skull, from Quercy in southern France, is important in showing relatively small orbits that are highly convergent, a distinct ethmoid component in the medial orbital wall, very small infraorbital foramina, a well-preserved auditory region with the stapedial canal about twice the diameter of the canal for the promontory artery, and a well-preserved braincase 8.8 cm³ in endocranial volume. The frontal lobe of the brain in the Cambridge skull described here is less expanded than that reported previously in a British Museum skull. The average body weight of Adapis parisiensis is estimated to have been about 2.0 kg, and that of Adapis magnus is estimated to have been about 8.4 to 9.0 kg. The encephalization quotient (EQ) of Adapis parisiensis is estimated to have been 0.45, which is well below the range found in modern prosimians. There is some indication that the size of the foramen magnum has increased with increasing brain size during primate evolution. Adapis parisiensis appears to have been a medium-sized, visually oriented, diurnal, sexually dimorphic arboreal folivore.     

Stereotaxic: measurements of the skull cap and skull base in merino sheep (Ovis aries L.)]

On the 14 skulls of 6-month old merino labms, stereotaxical measurements were carried out. Not only individual variations were found, but they also dependent on sex. A small assymetry was found on the diagrams of frontal measurements of the skull cap and base. The point bregma is more variable than the lambda. The position of the cranial third of the skull base in 6 month old lambs is not yet constant and until adult age it will shift about 30 degrees to 35 degrees dorsalward and forward. Since the skull cap and base do not grow parallely, and their cranial part has not constant position, we do not recommended this age group for chronic experiments with implanted electrodes. Owing to smaller variations of the skull cap and base and nearer position of the sutura sagittalis toward the medial line, male lambs would be more suitable for short-term experiments and for the stereotactic atlas of deep brain structures.     

Phenotypic integration of neurocranium and brain

Evolutionary history of Mammalia provides strong evidence that the morphology of skull and brain change jointly in evolution. Formation and development of brain and skull co-occur and are dependent upon a series of morphogenetic and patterning processes driven by genes and their regulatory programs. Our current concept of skull and brain as separate tissues results in distinct analyses of these tissues by most researchers. In this study, we use 3D computed tomography and magnetic resonance images of pediatric individuals diagnosed with premature closure of cranial sutures (craniosynostosis) to investigate phenotypic relationships between the brain and skull. It has been demonstrated previously that the skull and brain acquire characteristic dysmorphologies in isolated craniosynostosis, but relatively little is known of the developmental interactions that produce these anomalies. Our comparative analysis of phenotypic integration of brain and skull in premature closure of the sagittal and the right coronal sutures demonstrates that brain and skull are strongly integrated and that the significant differences in patterns of association do not occur local to the prematurely closed suture. We posit that the current focus on the suture as the basis for this condition may identify a proximate, but not the ultimate cause for these conditions. Given that premature suture closure reduces the number of cranial bones, and that a persistent loss of skull bones is demonstrated over the approximately 150 million years of synapsid evolution, craniosynostosis may serve as an informative model for evolution of the mammalian skull.     

The endocast from Dana Aoule North (DAN5/P1): A 1.5 million year-old human braincase from Gona,Afar, Ethiopia

The nearly complete cranium DAN5/P1 was found at Gona (Afar, Ethiopia), dated to 1.5–1.6 Ma, and assigned to the species Homo erectus. Its size is, nonetheless, particularly small for the known range of variation of this taxon, and the cranial capacity has been estimated as 598 cc. In this study, we analyzed a reconstruction of its endocranial cast, to investigate its paleoneurological features. The main anatomical traits of the endocast were described, and its morphology was compared with other fossil and modern human samples. The endocast shows most of the traits associated with less encephalized human taxa, like narrow frontal lobes and a simple meningeal vascular network with posterior parietal branches. The parietal region is relatively tall and rounded, although not especially large. Based on our set of measures, the general endocranial proportions are within the range of fossils included in the species Homo habilis or in the genus Australopithecus. Similarities with the genus Homo include a more posterior position of the frontal lobe relative to the cranial bones, and the general endocranial length and width when size is taken into account. This new specimen extends the known brain size variability of Homo ergaster/erectus, while suggesting that differences in gross brain proportions among early human species, or even between early humans and australopiths, were absent or subtle.     

Miniaturization and its effects on cranial morphology in plethodontid salamanders, genus Thorius (Amphibia, Plethodontidae): II. The fate of the brain and sense organs and their role in skull morphogenesis and evolution

Relative size and arrangement of the brain and paired sense organs are examined in three species of Thorius, a genus of minute, terrestrial salamanders that are among the smallest extant tailed tetrapods. Analogous measurements of representative species of three related genera of larger tropical (Pseudoeurycea, Chiropterotriton) and temperate (Plethodon) salamanders are used to identify changes in gross morphology of the brain and sense organs that have accompanied the evolution of decreased head size in Thorius and their relation to associated changes in skull morphology. In adult Thorius, relative size (area measured in frontal plane, and length) of the eyes, otic capsules, and brain each is greater than in adults of all of the larger genera; relative size of the nasal capsules is unchanged or slightly smaller. Interspecific scaling phenomena--negative allometry of otic capsule, eye and brain size, isometry or slight positive allometry of nasal capsule size, all with respect to skull length--also are characteristic of intraspecific (ontogenetic) comparisons in both T. narisovalis and Pseudoeurycea goebeli. Predominance of the brain and eyes in Thorius results in greater contact and overlap among these structures and the nasal capsules in the anterior portion of the head. This is associated with anterior displacement of both the eyes and nasal capsules, which now protrude anterior to the skull proper; a change in eye shape; and medial deformation of anterior braincase walls. Posteriorly, predominance of the otic capsules has effected a reorientation of the jaw suspensorium to a fully vertical position that is correlated with the novel presence of a posteriorly directed squamosal process and shift in origin of the quadropectoralis muscle. Many of these changes in cranial morphology may be explained simply as results of mechanical (physical) interactions among the skeletal, nervous, and sensory components during head development at reduced size. This provides further evidence of the role of nervous, sensory, and other "soft" tissues in cranial skeletal morphogenesis, and reinforces the need to consider these tissues in analyses of skull evolution.     

The subdivisions and fusions of the exoskeletal skull bones ofDiscosauriscus austriacus (Makowsky 1876) and their possible homologues in rhipidistians

Two localities in the Boskovice Furrow region of Moravia (Czecho-Slovakia) have produced new, well preserved material of the Lower Permian tetrapodDiscosauriscus austriacus (Makowsky 1876). A relatively large number of specimens have been found with some dermal skull roof bones partly or fully subdivided, and/or fused. These are the first records of such subdivisions and fusions in this tetrapod and the following bones are discussed: frontal, postfrontal, parietal, intertemporal, supratemporal, tabular and postparietal. The subdivided bones within the skull roof ofDiscosauriscus (and some dissorophoids) are situated at the same places as those found in Devonian rhipidistians, and may relate to the homology of the bones of the cranial exoskeletal roof inDiscosauriscus and in osteolepiforms. It shows that the “orthodox” terminology of the skull roof bones used in osteolepiforms is correct.     

Craniometric allometry in the thicktailed bushbabyOtolemur Crassicaudatus

Static adult craniometric allometry was evaluated in a sample of 66Otolemur crassicaudatus skulls (34 males, 32 females). Although cranial measures were equally well correlated to skull length in males and females, there were noteworthy differences in the exponential values between the sexes. These results underlined the need for caution when allometric analyses are based on pooled data. From the cranial allometric analyses it is concluded that the longer the skull, the shorter and the narrower the maxilla, and the broader the bizygomatic distance. Although cranial length increased proportionately to the increase in skull length, the cranial width in females was positively allometric whilst in males it was negatively allometric. Allometric analyses of mandibular dimensions suggest that larger animals will have proportionately longer mandibulae, which will, in turn, be relatively wider across the gonia, yet shallower behind the first molars. It is postulated that the disproportionate widening of the zygomata might be related to the widening across the gonia.     

Pattern in craniofacial biology: Evidence from the old world monkeys (Cercopithecidae)

An understanding of craniofacial growth, both evolutionarily and clinically, requires an investigation of pattern —geometric relations that remain relatively constant among growing structures or components of the skull. Several craniofacial biologists have suggested that specific morphological relations remain invariant during growth and in interspecific comparisons of adults of varying size. We tested the hypothesized invariance of a series of craniofacial angles in a sample of adult Old World monkeys. Fifteen angles were determined from lateral cranial radiographs. Criteria for examining angular invariance included tests for significant correlations and regression slopes with palatal length (overall skull size), tests for significant mean differences (ANOVAs) in angular values between the two subfamilies of Cercopithecidae — Cercopithecinae and Colobinae — and the computation and ranking of standard deviations (SDs) and coefficients of variation (CVs). Results indicate that most of the cranial angles purported to be invariant do not in fact meet the criteria for acceptance. One of the few cranial angles that evinces a somewhat constant value is that between the posterior maxillary plane and the neutral axis of the orbits, providing very limited support for Enlow’s (1982) claim that this region represents a fundamental anatomical interface (at least within Old World monkeys). Our analysis suggests that while there may be several relatively invariant structural relations within the skull, most of those previously discussed as representing evidence of pattern in primate-wide or mammal-wide comparisons are incorrect.     

Brain size of the lion (Panthera leo) and the tiger (P. tigris): implications for intrageneric phylogeny, intraspecific differences and the effects of captivity

Intraspecific encephalization of the lion and the tiger is investigated for the first time using a very large sample. Using cranial volume as a measure of brain size, the tiger has a larger brain relative to greatest length of skull than the lion, the leopard and the jaguar. The Asian lion has a relatively much smaller brain compared with those of sub-Saharan lions, between which there are few differences. The Balinese and Javan tigers had relatively larger brains compared with those of Malayan and Sumatran tigers, even although these four putative subspecies occupy adjacent ranges in south-eastern Asia. Differences in brain size do not appear to correlate with any known differences in behaviour and ecology and, therefore, may reflect only chance differences in intrageneric and intraspecific phylogeny. However, captive-bred big cats generally have a reduced brain size compared with that of wild animals, so that an animal's life history and living conditions may affect brain size and, hence, functional or environmental explanations should be considered when linking brain size differences to intraspecific phylogenies.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 85–93.     

The sixth skull cap of Pithecanthropus erectus

The sixth skull cap of Pithecanthropus erectus (or skull V, since the Modjokerto skull has not been given a number) was found in the upper layers of the Trinil beds of Sangiran (Central Java) in 1963, associated with fossils of the Sino-Malayan fauna. No stone tools were discovered in direct association with the find. The specimen consists of the occipital, both parietals, both temporals, sphenoid fragments, the frontal and the left zygomatic bone. We consider the skull to be a male in his early twenties. The occipital, parietal, frontal and temporal bones demonstrate definite pithecanthropine characteristics, and the cranial capacity is estimated to be 975 cm³. Of the superstructures, the supraorbital torus is extraodinarily thick, approaching the condition in Australopithecus boisei and Rhodesian man. And the sagittal torus is certainly higher than in skulls I and II, but lower than in skull IV. In addition, the angle between the occipital and nuchal planes is larger than in the previous finds. As revealed by various features, the gap between the robustness of skull IV on one hand, and skulls I, II and III on the other, is bridged by the present find. There is no reasonable taxonomic need to ascribe this specimen to a new species, because it seems to be merely an intrapopulational variant of the same species. Other skulls of P. erectus suggest that the bregmatic eminence, and hence the vertex, is invariably situated at bregma, but this new skull cap deviates from the pattern. Its pteric regions disclose the anthropoid X and I types. The middle meningeal groove pattern is similar to other Pithecanthropus skulls; however, it betrays a known anomaly in that the main stem is covered for a short distance by a bony plate. The mastoid process is fairly well developed, and is also well pneumatized as in P. pekinensis, with its air cells invading the pronounced supramastoid crest. The zygomatic bone, the first one recovered of P. erectus, does not show characters of particular importance. In fact, its thickness is in the range of modern man. We would like to stress that the absence of the cranial base does not necessarily indicate that the specimen must be a poor victim of cannibalism, since the morphology of the base renders it more susceptible to post-mortem natural traumata.     

The Skull of Stephanomys and a Review of Malpaisomys Relationships (Rodentia: Muridae): Taxonomic Incongruence in Murids

The cranial morphology of the extinct murid genus Stephanomys, previously known only by dental remains, is described here on the basis of partial skulls of three species of Pliocene age. Important cranial characters of the genus are a robust rostrum, a high zygoma, a wide zygomatic arch, a narrow interorbit, a large orbit, and an optic foramen in the backward position. In addition to some dental characters, Stephanomys shares most of these cranial traits with the extinct Malpaisomys from the Canary Islands. Some of these traits may be linked to the development of large eyes and life in a rocky environment. The peculiar dental pattern of Stephanomys (stephanodonty) is also present in some recent murids (Oenomys and Thamnomys) having a different skull morphology. A comparison with nine other extant genera of murids verified the relationship among Malpaisomys, Stephanomys, and Acomys, supporting our previous conclusion. Phenetic and cladistic analyses of 17 cranial and 23 dental characters show that skull morphology is phylogenetically informative but highly convergent and incongruent with other partial evidence based on dental and biochemical characters. The combined analyses of skull and teeth illustrate a case of mosaic evolution in murids.     

A novel transgenic mouse model of fetal encephalization and craniofacial development

There are surprisingly few experimental models of neural growthand cranial integration. This, and the dearth of informationregarding fetal brain development, detracts from a mechanisticunderstanding of cranial integration and its relevance to theontogenetic and interspecific patterning of the form of theskull. To address this shortcoming, our research uses transgenicmice expressing a stabilized form of β-catenin to isolatethe effects of encephalization on the development of the basi-and neuro-cranium. These mice develop highly enlarged brainsdue to an increase in neural precursor cells, and differencesbetween transgenic and wild-type mice are predicted to resultsolely from variation in relative brain size. By focusing onprenatal growth, this project adds to our understanding of acritically important period when major structural and functionalinterrelationships are established in the skull. Comparisonsof wild-type and transgenic mice were performed using microcomputedtomography (microCT) and magnetic resonance imaging (MRI). Theseanalyses show that the larger brains of the transgenic miceare associated with a larger neurocranium and an altered basicranialmorphology. However, body size and postcranial ossificationdo not seem to be affected by the transgene. Comparisons ofthe rate of postcranial and cranial ossification also pointto an unexpected effect of neural growth on skull development:increased fetal encephalization may result in a compensatorydecrease in the level of cranial ossification. Therefore, ifother life-history factors are held constant, the ontogeny ofa metabolically costly structure, such as a brain, may occurat the expense of other cranial structures. These analyses indicatethe benefits of a multifactorial approach to cranial integrationusing a mouse model.     

男性特小颅一例报告

本例特小颅T1的死者为男性,年龄约40岁,身高168cm,中国人。经颅骨各项指标测量和观察,该颅骨的脑颅特小,尤其是额部特别窄小;而面颅则相对较大,上、下颌骨向前突出。颅骨主要的长、宽、高各径和弧、弦、周长等的测量值均比其他报道中的最小值要小;颅容量为602ml,比已报道的最小颅容量1340ml还要小一倍多,故将其称为特小颅。