A histological survey of avian post-natal skeletal ontogeny

Bone histology of crown-group birds is a research topic of great interest, permitting insight into the evolution of remarkably high growth rates in this clade and variation across the altricial-precocial spectrum. In this study, we describe microanatomical characteristics of the humerus and femur in partial growth series from 14 crown group birds representing ten major clades (Struthioniformes, Galliformes, Apodiformes, Columbiformes, Charadriiformes, Accipitriformes, Strigiformes, Psittaciformes, Falconiformes, and Passeriformes). Our goals were to: (1) describe the microanatomy of each individual; (2) make inter-and intra-taxonomic comparisons; (3) assess patterns that correspond with developmental mode; and (4) to further parse out phylogenetic, developmental, and functional constraints on avian osteological development. Across taxa, the femoral and humeral tissue of neonates can be broadly characterized as highly-vascularized, disorganized woven bone with great variation in cortical thickness (inter-and intrataxonomically, within an individual specimen, and within a single section). The tissue of precocial chicks is relatively more mature at hatching than in altricial, but other categories along the developmental spectrum were less easy to distinguish, thus we were unable to identify a definitive histological proxy for developmental mode. We did not find evidence to support hypotheses that precocial chicks exclusively have thicker cortices and more mature bone in the femur than the humerus at time of hatching; instead, this is a characteristic of nearly all taxa (regardless of developmental mode), suggesting deep evolutionary origins and the effects of developmental channeling. Bone tissue in adults exhibited unexpected variation, corresponding to differences in body size. Large-bodied birds have cortices of fibrolamellar bone, but organization of tissue increases and vascularity decreases with diminishing body size. The outer circumferential layer (OCL) also appears at earlier growth stages in small-bodied taxa. Thus, while the OCL is indicative of a cessation of appositional growth it is not always indicative of cortical maturity (that is, maximum organization of bony tissue for a given taxon). Small size is achieved by truncating the period of fast growth; manipulation of the timing of offset of bone growth is therefore an important factor in changing growth trajectories to alter adult body size.

Defence Spending and Economic Growth in South Africa: Evidence from Cointegration and Co-Feature Analysis

The paper revisits the causality relationship between defence spending and economic growth for South Africa during the period 1960–2018. The results of our estimation show that defence spending and economic growth are cointegrated and that there is bidirectional Granger causality running between defence spending and economic growth in the long run. We then applied a Hodrick-Prescott filter to decompose the trend and the fluctuation components of the defence spending and economic growth series. The findings from the autoregressive distributed lag bounds test estimations show that in the long- and short-run, the trends and cyclicality of defence spending retard economic growth. The estimation results show that there is cointegration between the trends and the cyclical components of the two series, which suggests that the Granger causality possibly relates to the business cycle. This study suggests that investing more and reducing inefficiency spending in the defence sector during fluctuations can further stimulate economic growth in South Africa.

Computed Tomography elucidates ontogeny within the basal therapsid clade Biarmosuchia

Biarmosuchia is a clade of basal therapsids that includes forms possessing plesiomorphic ‘pelycosaurian’ cranial characters as well as the highly derived Burnetiamorpha which are characterised by cranial pachyostosis and a variety of cranial bosses. Potential ontogenetic variation in these structures has been suggested based on growth series of other therapsids with pachyostosed crania, which complicates burnetiamorph taxonomic distinction and thus it is essential to better understand cranial ontogeny of the Burnetiamorpha. Here, three new juvenile biarmosuchian skulls from the late Permian of South Africa are described using X-ray micro computed tomography (CT). We found that juvenile biarmosuchians are distinguished from adults by their relatively large orbits, open cranial sutures, and incomplete ossification of the braincase and bony labyrinth. Also, they manifest multiple centres of ossification within the parietal and preparietal bones. CT examination reveals that the holotype of Lemurosaurus pricei (BP/1/816), previously alleged to be a juvenile, shows no evidence of juvenility and is thus probably an adult. This suggests that the larger skull NMQR 1702, previously considered to be an adult L. pricei, may represent a new taxon. This study provides, for the first time, a list of characters by which to recognise juvenile biarmosuchians.

Changes of base-year and Indian GDP growth: an agnostic look

Purpose World over, change of base year in the gross domestic product (GDP) is a standard practice of GDP estimation. However, unless a consistent series of GDP is released with respect to the new base for the earlier period, the existence of multiple growth rates creates problems for applied researchers, policymakers and the general public alike. Faced with such a menu of GDP series researchers often try to interpolate a consistent series of GDP. The main purpose of this paper is to analyses the nature of the data generating process of such multiple interpolated series of quarterly growth rates and tries to discern the consistency of such processes. Design/methodology/approach The present paper tries to look into the statistical implications and complications of such interpolated quarterly GDP/growth series in India in terms of three series of GDP, namely, with 1999–2000, 2004–2005 and 2011–2012 as its bases. Findings The analysis reveals that as a result of a change of base year, the nature of the data generating process of the old and new GDP series could undergo changes and experience different breakpoints. While all these conclusions seem to be valid for GDP growth at quarterly intervals, taking the data at annual frequency is less problematic. Practical implications The observation suggests that in most applied work, researchers may not have the luxury of only working with annual data and certain consistency checks will be necessary to check the veracity of the results based on quarterly data with those based on annual data. Second, moving forward it may be useful for the Authorities to make a transition to a chain-based linking method rather than fixed time-period-based bases as is currently done. Originality/value The analysis of Indian GDP in this paper is, perhaps, indicative of the fact that usage of quarterly GDP data is to be handled with caution and it is preferable that any serious empirical analysis uses annual GDP data whenever it is available/feasible. The comparison of GDP growth rates at different frequencies and examining the true nature of the process are quite unique in their contribution towards empirical macroeconomic research.

Anatomy and systematics of the diplodocoid Amphicoelias altus supports high sauropod dinosaur diversity in the Upper Jurassic Morrison Formation of the USA

Sauropod dinosaurs were an abundant and diverse component of the Upper Jurassic Morrison Formation of the USA, with 24 currently recognized species. However, some authors consider this high diversity to have been ecologically unviable and the validity of some species has been questioned, with suggestions that they represent growth series (ontogimorphs) of other species. Under this scenario, high sauropod diversity in the Late Jurassic of North America is greatly overestimated. One putative ontogimorph is the enigmatic diplodocoid Amphicoelias altus , which has been suggested to be synonymous with Diplodocus . Given that Amphicoelias was named first, it has priority and thus Diplodocus would become its junior synonym. Here, we provide a detailed re-description of A. altus in which we restrict it to the holotype individual and support its validity, based on three autapomorphies. Constraint analyses demonstrate that its phylogenetic position within Diplodocoidea is labile, but it seems unlikely that Amphicoelias is synonymous with Diplodocus . As such, our re-evaluation also leads us to retain Diplodocus as a distinct genus. There is no evidence to support the view that any of the currently recognized Morrison sauropod species are ontogimorphs. Available data indicate that sauropod anatomy did not dramatically alter once individuals approached maturity. Furthermore, subadult sauropod individuals are not prone to stemward slippage in phylogenetic analyses, casting doubt on the possibility that their taxonomic affinities are substantially misinterpreted. An anatomical feature can have both an ontogenetic and phylogenetic signature, but the former does not outweigh the latter when other characters overwhelmingly support the affinities of a taxon. Many Morrison Formation sauropods were spatio-temporally and/or ecologically separated from one another. Combined with the biases that cloud our reading of the fossil record, we contend that the number of sauropod dinosaur species in the Morrison Formation is currently likely to be underestimated, not overestimated.

Relative Growth in Hyperbolic Groups

In this note we obtain estimates on the relative growth of normal subgroups of non-elementary hyperbolic groups, particularly those with free abelian quotient. As a corollary, we deduce that the associated relative growth series fail to be rational.

Mandibular force profiles and tooth morphology in growth series of Albertosaurus sarcophagus and Gorgosaurus libratus (Tyrannosauridae: Albertosaurinae) provide evidence for an ontogenetic dietary shift in tyrannosaurids

The albertosaurines Albertosaurus sarcophagus and Gorgosaurus libratus are among the best represented tyrannosaurids, known from nearly complete growth series. These specimens provide an opportunity to study mandibular biomechanical properties and tooth morphology in order to infer changes in feeding behavior and bite force through ontogeny in tyrannosaurids. Mandibular force profiles reveal that the symphyseal region of albertosaurines is consistently stronger in bending than the middentary region, indicating that the anterior extremity of the jaws played an important role in prey capture and handling through ontogeny. The symphyseal region was better adapted to withstand torsional stresses than in most non-avian theropods, but not to the extent seen in Tyrannosaurus rex, suggesting that albertosaurine feeding behavior may have involved less bone crushing or perhaps relatively smaller prey than in T. rex. The constancy of these biomechanical properties at all known growth stages indicates that although albertosaurines maintained a similar feeding strategy through ontogeny, prey size/type had to change between juvenile and mature individuals. This ontogenetic dietary shift likely happened when individuals reached a mandibular length of ~58 cm, a size at which teeth shift from ziphodont to incrassate in shape and bite force begins to increase exponentially. The fact that large albertosaurines were capable of generating bite forces equivalent to similar-sized tyrannosaurines suggests that no significant differences in jaw closing musculature existed between the two clades and that the powerful bite of T. rex is the result of its large body size rather than of unique adaptations related to a specialized ecology.

Description and rediagnosis of the crested hadrosaurid (Ornithopoda) dinosaur Parasaurolophus cyrtocristatus on the basis of new cranial remains

For nearly 60 years, skulls of Parasaurolophus species have been differentiated primarily on the basis of crest shape rather than on unique morphologic characters of other cranial elements. Complicating matters is the fact that crests dramatically change shape throughout ontogeny. Without a complete growth series, it has become difficult to assess the taxonomic distinctness of each species through the lens of allometric growth. Parasaurolophus cyrtocristatus has proven to be especially troublesome to assess because of the poorly preserved nature of the type and only skull. A new, partial skull from the Fossil Forest Member of the Fruitland Formation—the same geologic unit as the type specimen—is the first opportunity to re-diagnose this species as well as redefine the genus with many new traits. An undescribed, short-crested subadult skull from the Kaiparowits Formation of Utah previously assigned to cf. P. cyrtocristatus allows detailed comparisons to be made between the unnamed Utah taxon and the material of this species from the type locality. We find that several characteristics of the squamosal, supraoccipital, and premaxilla shared between the referred skull and the type skull are unique to P. cyrtocristatus (senso stricto) within the genus, irrespective of the overall crest shape. A phylogenetic analysis that includes six new characters posits that P. cyrtocristatus and P. tubicen are sister taxa, and that the latter does not share a closest common ancestor with the long-crested P. walkeri as previously hypothesized. This result helps to explain why both taxa are found in northeastern New Mexico, USA and in sequential geologic units (Fruitland Formation and Kirtland Formation, respectively). Additionally, the exquisitely preserved new skull provides the first opportunity to unequivocally identify the osteological make-up of the Parasaurolophus cranial crest. Unlike in previous reconstructions, the crest composition in Parasaurolophus follows what is seen in other lambeosaurines such as Corythosaurus, where the dorsal process of the premaxilla dominates the crest, with the nasal forming 80% of the ventral paired tubes, and the lateral premaxillary process acting a lateral cover between the dorsal and ventral tubes. The skull of P. cyrtocristatus is still incompletely known, so more complete material will likely reveal new features that further differentiate this species and aid in determining the pace of ornamental crest evolution.