HE Qing, JIANG Qin, XING Li-da, AN Yan-fei, HOU Jie & HU Yi (2018)
Microstructure and Raman Spectra Characteristics of Dinosaur Eggs from Qiyunshan, Anhui Province.
Spectroscopy and Spectral Analysis 38(7): 2143â2148 (in Chinese)
The dinosaur eggs from Qiyunshan, Anhui Province, are the newly discovery which can provide new information for researching the formation mechanisms of dinosaur eggshell. Polarizing microscope and Laser Raman spectroscopy were used to analyze the inner mineral composition and structure characteristics of Qiyunshan dinosaur eggshell in this paper. The results showed that the main minerals of eggshells composed of calcite, organic matter and little quartz, opal, muscovite, dolomite, glauconite and goethitewere formed by permineralization and carbonization. Polarizing microscope results revealed that primary calcite and secondary calcite appeared graphic structure. The crystalline degree of primary calcite was poor, which was the product of eggshell petrification, while the crystallinity of secondary calcite was better and there were little quartz in secondary calcite. Raman spectra analysis indicated that the Raman peaks of primary calcite and secondary calcite both appeared near 1087, 282, 713 and 155 cm-1, but the Raman intensity and crystallinity of secondary calcite with coarser particles were higher than primary calcite, which was consistent with the microscopic observations. Raman peaks appearing near at 1 360 and 1 600 cm-1were related to the tiny crystal vibration and C--C stretching vibration of organic matter. All of Raman peaks near 466, 209, 130, 357 and 404 cm-1were the characteristic peaks of quartz. In addition, the Raman peaked near 898, 629, 1 458, 654 and 481 cm-1represent opal, muscovite, dolomite, glauconite and goethite respectively, which suggested that minerals in the surrounding rock hadentered the inside of the eggshell. The conclusion provided important data for studying the mineral formation of eggshell and sedimentary environment of the dinosaur-egg-bearing strata.
Claudia InÃs Serrano-BraÃasa, Belinda Espinosa-ChÃvez & S. Augusta Maccracken (2018)
Gastrochaenolites Leymerie in dinosaur bones from the Upper Cretaceous of Coahuila, north-central Mexico: Taphonomic implications for isolated bone fragments.
Cretaceous Research (advance online publication)
Gastrochaenolites borings are described for the first time on hadrosaur bones from Coahuila, Mexico.
Ethology of borers can help elucidate different biostratinomic stages in solitary bone fragments.
Relics of encrusting organisms provide evidence of subsequent reworking and reburial scenarios.
Isolated bone fragments are typically disregarded during the collection of vertebrate remains because of the apparent lack of useful taxonomic information, as compared to intact or articulated bones. The presence of isolated bone fragments is occasionally reported, but no particular taphonomic data are conveyed and valuable depositional information is overlooked. However, through the analysis of borings and other traces of encrusting organisms present on bone fragments, we may obtain valuable information about their post-mortem histories within a depositional environment. In this study, bivalve borings in isolated hadrosaur bone fragments are described from the Campanian Cerro del Pueblo Formation of Coahuila, north-central Mexico. Two ichnotraces indicate transport from terrestrial to shallow-marine environments: Gastrochaenolites turbinatus and Gastrochaenolites cluniformis. These borings represent the first description of Gastrochaenolites at ichnospecies level in dinosaur bones. Additional relics of encrusting organisms and the fill of sediment provide evidence for subsequent reworking and reburial of the bones. The taphonomic analysis results an important clue for understanding the preservation of the studied fragmented bones within brackish and marine sedimentary settings, and an aid for reconstructing the Late Cretaceous environmental evolution in north-central Mexico.
Gerald Mayr & Stig A. Walsh (2018)
Exceptionally well-preserved early Eocene fossil reveals cranial and vertebral features of a stem group roller (Aves: Coraciiformes).
Palaeobiodiversity and Palaeoenvironments (advance online publication)
Three-dimensionally preserved skulls of small Paleogene land birds are very rare. Here, we describe a cranium and associated partial postcranial remains of an early Eocene stem group roller (Aves: Coraciiformes) from the London Clay of the Isle of Sheppey (England). The fossil shows features of the skull and vertebral column in great detail. It is distinguished from extant Coraciidae and Brachypteraciidae in several presumably plesiomorphic characteristics, which are likely to reflect differences in diet and/or foraging strategy between Eocene and extant rollers. Preserved stomach contents in other early Eocene fossils indicate that fruits were a regular part of the diet of stem group rollers. The extant Coraciidae and Brachypteraciidae, by contrast, almost exclusively feed on larger-sized invertebrates and small vertebrates, which are usually dispatched by beating before being swallowed. Stronger biting forces as well as the characteristic prey manipulation behavior of extant rollers may account for some of the observed differences in the cranial and vertebral morphology of the fossil and extant taxa, but the exact functional correlations remain elusive. We furthermore identify a previously undescribed cranial feature of rollers: a very large foramen for the ramus occipitalis of the arteria ophthalmica externa, which is of unknown functional significance and constitutes a potentially promising research target for future studies.
Gilmoremys gettyspherensis n. sp.Â
Walter G. Joyce, Tyler R. Lyson & Joseph J.W. Sertich (2018)
A new species of trionychid turtle from the Upper Cretaceous (Campanian) Fruitland Formation of New Mexico, USA.
Journal of Paleontology (advance online publication)
New shell material of a trionychid turtle from the Upper Cretaceous (upper Campanian) Fossil Forest Member of the Fruitland Formation of northwestern New Mexico represents a new species, Gilmoremys gettyspherensis. The material consists of right costals IâIII, V, VI, and VIII, left costals V, VII, and VIII, the left half of the entoplastron, the right hypo- and xiphiplastron, and the left hyo-, hypo-, and xiphiplastron. The specimen shows great similarities to the Late Cretaceous (Maastrichtian) trionychid Gilmoremys lancensis (Gilmore, 1916) by having a relatively thin shell, carapacial sculpturing consisting of fine pits combined with extended sinusoidal ridges or grooves, free costal rib ends, presence of a preneural, a distally constricted costal I and distally expanded costal II, two lateral hyoplastral processes, low hyoplastral shoulders, and full midline contact of the elongate xiphiplastra, but differs by being smaller, having raised sinusoidal ridges on the carapace instead of grooves, less distally expanded costals II, and less elongate xiphiplastra. Phylogenetic analysis places Gilmoremys gettyspherensis n. sp. as sister to Gilmoremys lancensis near the base of the clade Plastomenidae. Like the majority of previously described plastomenid materials, the type specimen of Gilmoremys gettyspherensis n. sp. was collected from a mudstone horizon, suggesting a preference for ponded environments.
Reposting this in a formal way:
Mark J. MacDougall, Sean P. Modesto, Neil Brocklehurst, Antoine VerriÃre, Robert R. Reisz & JÃrg FrÃbisch (2018)
Response: A Reassessment of the Taxonomic Position of Mesosaurs, and a Surprising Phylogeny of Early Amniotes
Frontiers in Earth Sciences 6: Article 99
The early amniote clade Mesosauridae has long been of interest to scientists, primarily due to the members of the clade being the oldest secondarily aquatic tetrapods and their role as a line of evidence for continental drift. In the landmark phylogenetic analysis of Parareptilia by Gauthier and colleagues in 1988, Mesosauridae was found to be the sister taxon of all included parareptiles. Over the last three decades several studies regarding the phylogenetic placement of mesosaurs have helped to reinforce their position as the most basal parareptile clade. The most recent study of Mesosauridae is by Laurin and PiÃeiro, who reassess the phylogenetic position of the clade within early amniotes. This new analysis recovered mesosaurs as being the sister clade to all other sauropsids, supporting the results of an earlier study by Laurin and Reisz in 1995. However, we feel that there are two main issues with this new study that need to be addressed. The first is the use of an outdated phylogenetic matrix and the fact that the authors patently ignore over two decades of parareptilian research when conducting their phylogenetic analysis, whereas the second involves the problems associated with lateral temporal fenestration and its extreme variability in reptiles. We discuss how these two issues could have influenced the results that were obtained from this study, and how, when they are taken into account, a different picture regarding the phylogenetic position of Mesosauridae is reconstructed to that of Laurin and PiÃeiro.
Borja Esteve-Altava, Stephanie E Pierce, Julia L Molnar, Peter Johnston, Rui Diogo & John R Hutchinson (2018)
Evolutionary parallelisms of pectoral and pelvic network-anatomy from fins to limbs.
Pectoral and pelvic lobe-fins transformed into fore- and hindlimbs during the Devonian period, enabling the water-to-land transition in tetrapods. In the timespan of ~60 million years, transitional forms evolved, spanning a wide range of morphologies. Here we traced the evolution of well-articulated appendicular skeletons across the fins-to-limbs transition, using a network-based approach and phylogenetic tools to quantify and compare topological features of skeletal anatomy of fins and limbs. We show that the topological arrangement of bones in the pectoral and pelvic appendages evolved in parallel during the fins-to-limbs transition, occupying overlapping regions of the morphospace, following a directional mode of evolution, and decreasing their disparity over time. We identify the presence of digits as the morphological novelty triggering significant topological changes that clearly discriminated limbs from fins. The origin of digits caused an evolutionary shift towards appendages that were less densely and heterogeneously connected, but more assortative and modular. Topological disparity likewise decreased for both appendages: for the pectoral appendage, until the origin of amniotes; for the pelvic appendage, until a time concomitant with the earliest-known tetrapod tracks. Finally, we tested and rejected the presence of a pectoral-pelvic similarity bottleneck for the network-anatomy of appendages at the origin of tetrapods. We interpret our findings in the context of a dynamic compromise between possibly different functional demands in pectoral and pelvic appendages during the water-to-land transition and a shared developmental program constraining the evolvability of limbs.