Description of the tympanic regions of Paraechinus and Podogymnura

58 p. : ill. ; 24 cm.Includes bibliographical references (p. 56-58)."Although living hedgehogs have long been regarded [as] the archetypes of the primitive placental mammal, they have nonetheless had a complex Cenozoic history that is reflected in the recognition of three extinct and two living erinaceid subfamilies. Members of one extinct subfamily, the Brachyericinae, underwent a remarkable shortening of the skull and a reduction in the number of teeth during the Oligocene, Miocene, and early Pliocene. This trend culminated in the two North American genera, Brachyerix and Metechinus, in which only three teeth were retained anterior to P[subscript]4. Dimylechinus, a European form from the early Miocene, and Exallerix from the medial Oligocene of Asia both retained at least four teeth anterior to P[subscript]4. None of the four genera had an M[subscript]3. Brachyerix and Metechinus occur from the Great Plains to the Pacific coast of North America. Brachyerix is temporally restricted to the Miocene; Metechinus occurs in late Miocene and early Pliocene sediments. Although both genera are known from several localities, they are never found together, which may reflect an ecological separation of these two forms during temporal overlap. Both are known only from cranial osteology. During the past 40 years, the differences between these two North American genera have not been well defined, and only now with the availability of several specimens of each can the generic boundaries be adequately reviewed. Two species of Brachyerix are recognized in the present paper. Brachyerix macrotis, restricted to the early and medial Miocene, is the larger of the two and differs from B. incertis, new combination (late Miocene), in having a stronger lingual cingulum on P[superscript]3 and in entirely lacking a P[superscript]3 protocone. Metechinus marslandensis can now be synonymized with B. macrotis, whereas Talpa incerta and Metechinus fergusoni are both junior synonyms of B. incertis. Only Metechinus nevadensis still requires generic separation owing to its unique basicranium, small auditory bullae, nature of the sagittal crest, and relatively anteroposteriorly compressed M[subscript]1 trigonid. Dimylechinus bernoullii is an adequate structural ancestor for Brachyerix macrotis and its descendents. However, as both Dimylechinus and Exallerix are known only from single specimens, their relationship to the North American brachyericines as well as to one another is not well understood and will not be until further specimens are found. An appendix describing the ear regions of two living hedgehog genera, Paraechinus and Podogymnura, is included to supplement Butler's (1948) paper on the erinaceid ear region. Paraechinus is the only living erinaceid that has bony tubes covering part of the blood vessels contained in the tympanic cavity, a condition developed to the extreme in the Miocene Brachyerix"--P. [1]-2

Erinaceinae and Brachyericinae

116 p. : ill., maps ; 26 cm.Thesis (Ph. D.)--Columbia University.Includes bibliographical references (p. [111]-116)."Modern Erinaceidae include the familiar hedgehog, Erinaceus europaeus, the archetypical primitive placental mammal in the minds of many biologists. Now restricted to the Old World, the family flourished in North America during the Miocene when three subfamilies were present there. Restricted to North America, the Brachyericinae seem to have originated on that continent. Both North American genera of Amphechinini (new tribe of the Erinaceinae) are well known in the Old World in earlier Oligocene deposits and hence appear to have immigrated into North America just before their first appearance there in the early Miocene. Area of origin of the Erinaceini may be interpreted as (1) unspecified within Holarctica plus the Ethiopian Region or (2) as external to Holarctica, depending on how the evidence is weighed. The sudden appearance of the tribe over the extent of Holarctica plus the Ethiopian Region at the beginning of the Miocene and the existence of an adequate structural ancestor in North America immediately prior to the time of initial appearance suggests the first interpretation. Counter to this, the presence in the Oligocene of a derived sister group of the Erinaceini (i.e., the Amphechinini) suggests that the tribe existed by that time, probably in an area where adequate collections from that epoch have not been made, e.g., Africa. Van Couvering (1972) has suggested that many forms which suddenly appear in the Miocene record of Europe without known precursors may have existed in Africa during the Oligocene and migrated only after the two continental blocks met in the mid-Cenozoic. Because the African Oligocene record of small mammals is so pitifully poor and a plausible reason exists for expecting that the Erinaceini existed there during that epoch, the second hypothesis appears more probable at this time. Once established in North America in the early Miocene, both the Erinaceinae and Brachyericinae had relatively uneventful histories. Least eventful was that of the Amphechinini, one species (Parvericius montanus) appearing to be conspecific with forms known in the Oligocene of Asia and the other species (Amphechinus horncloudi) differing only slightly from its Old World predecessors and contemporaries in that genus. Although A. horncloudi did not survive the Arikareean when it first appeared, P. montanus persisted with little noticeable change from that age through the Barstovian. Only one species of Erinaceini is recognized, Untermannerix copiosus (new), which appeared in the Barstovian and persisted until the Clarendonian with no noticeable change. More complex was the history of the Brachyericinae. Both genera have two species of markedly different size. In each, the smaller species appears to suddenly replace the larger. In the case of Metechinus, the evidence for this abruptness is equivocal but for Brachyerix it is highly compelling. Most useful in the analysis of the data has been the cladistic method as outlined by Hennig in his 1966 work. It was a fundamental tool in the development of the more plausible second hypothesis of the history of the Erinaceini outlined above. Determination of primitive and derived states or polarity of a given character, a fundamental problem of the cladistic method, was made by analyzing the distribution of the different states among the several groups recognized in an initial, credible higher phylogenetic hypothesis. Character states widely scattered in a haphazard pattern among the groups were regarded as primitive; ones found in only a few groups, particularly when thought to be closely related, were regarded as derived. In cases where the pattern was ambiguous, by restricting the sample examined to forms known prior to an arbitrary geologic epoch, it was often possible to determine polarity in this subset. Because in this procedure one is examining the forms that would have been available had one lived at that earlier, arbitrary date, the methodological pitfalls are no different from examining the total sample including modern forms"--P. 5

Cranial biomechanics, bite force and function of the endocranial sinuses in Diprotodon optatum, the largest known marsupial

The giant extinct marsupial Diprotodon optatum has unusual skull morphology for an animal of its size, consisting of very thin bone and large cranial sinuses that occupy most of the internal cranial space. The function of these sinuses is unknown as there are no living marsupial analogues. The finite element method was applied to identify areas of high and low stress, and estimate the bite force of Diprotodon to test hypotheses on the function of the extensive cranial sinuses. Detailed three‐dimensional models of the cranium, mandible and jaw adductor muscles were produced. In addition, manipulations to the Diprotodon cranial model were performed to investigate changes in skull and sinus structure, including a model with no sinuses (sinuses ‘filled’ with bone) and a model with a midsagittal crest. Results indicate that the cranial sinuses in Diprotodon significantly lighten the skull while still providing structural support, a high bite force and low stress, indicating the cranium may have been able to withstand higher loads than those generated during feeding. Data from this study support the hypothesis that pneumatisation is driven by biomechanical loads and occurs in areas of low stress. The presence of sinuses is likely to be a byproduct of the separation of the outer surface of the skull from the braincase due to the demands of soft tissue including the brain and the large jaw adductor musculature, especially the temporalis. In very large species, such as Diprotodon, this separation is more pronounced, resulting in extensive cranial sinuses due to a relatively small brain compared with the size of the skull

Observations of Lick Standard Stars Using the SCORPIO Multi-Slit Unit at the SAO 6-m Telescope

We present Lick line-index measurements of standard stars from the list of Worthey. The spectra were taken with the multi-slit unit of the SCORPIO spectrograph at the 6-m Special Astrophysical observatory telescope. We describe in detail our method of analysis and explain the importance of using the Lick index system for studying extragalactic globular clusters. Our results show that the calibration of our instrumental system to the standard Lick system can be performed with high confidence.Comment: 12 pages, 3 figure

New eucryptodiran turtle

35 p. : ill., maps ; 26 cm.Includes bibliographical references (p. 28-30).Chubutemys copelloi is the oldest nonmarine cryptodire from South America represented by a skull. The skull and associated postcranial fragments are from the Aptian Cerro CostaŠno Member of the Cerro Barcino Formation of Chubut, Argentina. Chubutemys has a processus trochlearis oticum, showing that it is a cryptodire, and an enclosed canalis caroticus internus extending to the posterior margin of the pterygoid, showing that it is a eucryptodire. The skull of Chubutemys is similar to that of other primitive eucryptodires, particularly Dracochelys, but also to Hangaiemys, Judithemys, Sinemys, and Ordosemys. Chubutemys differs from all these, however, in possessing a solidly roofed skull, formed by long, wide parietals, rather than a posterior emargination. Chubutemys also differs from these taxa in having no cheek emargination. A phylogenetic analysis using PAUP* analyzed 104 parsimony-informative characters resolving into one most parsimonious cladogram of 224 steps, a consistency index of 0.55, and a retention index of 0.74. The phylogenetic analysis weakly joins Chubutemys and meiolaniids on the basis of the prefrontal-postorbital contact. Chubutemys also has a fully roofed skull and slitlike posterior opening of the foramen caroticum laterale (foramen posterius canalis caroticus laterale), features to be expected in a meiolaniid sister taxon. Chubutemys provides further evidence that meiolaniids are related to 'basal' eucryptodires ('sinemydids/macrobaenids'), that is, eucryptodires outside the living Cryptodira, the Polycryptodira. The basicranial morphology of meiolaniids, with an intrapterygoid slit, rather than being a unique feature of the group is instead a modified state of the primitive eucryptodire condition, as seen in such forms as Chubutemys, Dracochelys, Ordosemys, and Sinemys. The intrapterygoid slit of meiolaniids is homologous with the pterygoid flange associated with the foramen caroticum laterale (foramen posterius canalis caroticus laterale of Sukhanov) in non-Polycryptodiran eucryptodires like Ordosemys. Chubutemys shows that nonmarine eucryptodires were present in South America in the Cretaceous, as they were in North America, central Asia, and Australia

Growth Dynamics of Australia's Polar Dinosaurs

Analysis of bone microstructure in ornithopod and theropod dinosaurs from Victoria, Australia, documents ontogenetic changes, providing insight into the dinosaurs' successful habitation of Cretaceous Antarctic environments. Woven-fibered bone tissue in the smallest specimens indicates rapid growth rates during early ontogeny. Later ontogeny is marked by parallel-fibered tissue, suggesting reduced growth rates approaching skeletal maturity. Bone microstructure similarities between the ornithopods and theropods, including the presence of LAGs in each group, suggest there is no osteohistologic evidence supporting the hypothesis that polar theropods hibernated seasonally. Results instead suggest high-latitude dinosaurs had growth trajectories similar to their lower-latitude relatives and thus, rapid early ontogenetic growth and the cyclical suspensions of growth inherent in the theropod and ornithopod lineages enabled them to successfully exploit polar regions

Stellar Proper Motions in the Galactic Bulge from deep HST ACS/WFC Photometry

We present stellar proper motions in the Galactic bulge from the Sagittarius Window Eclipsing Extrasolar Search (SWEEPS) project using ACS/WFC on HST. Proper motions are extracted for more than 180,000 objects, with >81,000 measured to accuracy better than 0.3 mas/yr in both coordinates. We report several results based on these measurements: 1. Kinematic separation of bulge from disk allows a sample of >15,000 bulge objects to be extracted based on >6-sigma detections of proper motion, with <0.2% contamination from the disk. This includes the first detection of a candidate bulge Blue Straggler population. 2. Armed with a photometric distance modulus on a star by star basis, and using the large number of stars with high-quality proper motion measurements to overcome intrinsic scatter, we dissect the kinematic properties of the bulge as a function of distance along the line of sight. This allows us to extract the stellar circular speed curve from proper motions alone, which we compare with the circular speed curve obtained from radial velocities. 3. We trace the variation of the {l,b} velocity ellipse as a function of depth. 4. Finally, we use the density-weighted {l,b} proper motion ellipse produced from the tracer stars to assess the kinematic membership of the sixteen transiting planet candidates discovered in the Sagittarius Window; the kinematic distribution of the planet candidates is consistent with that of the disk and bulge stellar populations.Comment: 71 pages, 30 figures, ApJ Accepte

Development of complex executive function over childhood : Longitudinal growth curve modeling of performance on the Groton Maze Learning Task

Abstract This longitudinal study modeled children's complex executive function (EF) development using the Groton Maze Learning Task (GMLT). Using a cohort-sequential design, 147 children (61 males, 5.5–11 years) were recruited from six multicultural primary schools in Melbourne and Perth, Australia. Race/ethnicity data were not available. Children were assessed on the GMLT at 6-month intervals over 2-years between 2010 and 2012. Growth curve models describe age-related change from 5.5 to 12.5 years old. Results showed a quadratic growth trajectory on each measure of error—that is, those that reflect visuospatial memory, executive control (or the ability to apply rules for action), and complex EF. The ability to apply rules for action, while a rate-limiting factor in complex EF, develops rapidly over early-to-mid childhood

Near-Infrared Properties of Metal-poor Globular Clusters in the Galactic Bulge Direction

Aims. J, H, and K' images obtained from the near-infrared imager CFHTIR on the Canada-France-Hawaii Telescope are used to derive the morphological parameters of the red giant branch (RGB) in the near-infrared color-magnitude diagrams for 12 metal-poor globular clusters in the Galactic bulge direction. Using the compiled data set of the RGB parameters for the observed 12 clusters, in addition to the previously studied 5 clusters, we discuss the properties of the RGB morphology for the clusters and compare them with the calibration relations for the metal-rich bulge clusters and the metal-poor halo clusters. Methods. The photometric RGB shape indices such as colors at fixed magnitudes of MK = MH = (-5.5, -5, -4, and -3), magnitudes at fixed colors of (J - K)o = (J - H)o = 0.7, and the RGB slope are measured from the fiducial normal points defined in the near- infrared color-magnitude diagrams for each cluster. The magnitudes of RGB bump and tip are also estimated from the differential and cumulative luminosity functions of the selected RGB stars. The derived RGB parameters have been used to examine the overall behaviors of the RGB morphology as a function of cluster metallicity. Results. The correlations between the near-infrared photometric RGB shape indices and the cluster metallicity for the programme clusters compare favorably with the previous observational calibration relations for metal-rich clusters in the Galactic bulge and the metal-poor halo clusters. The observed near-infrared magnitudes of the RGB bump and tip for the investigated clusters are also in accordance with the previous calibration relations for the Galactic bulge clusters.Comment: 12 pages, 9 figures, accepted for publication in Astronomy & Astrophysic