In This Issue

doi:10.1073/iti3919116

New Research In

Cranial kinesis and avian palate evolution

S. chaoyangensis specimen IVPP V19058.

Cranial kinesis—relative movement between the braincase and the upper jaw—occurs in most living birds. The origin of this ability is poorly understood due to a lack of palatal elements preserved in the fossil record. Han Hu et al. (pp. 19571–19578) describe a fossil specimen of Sapeornis chaoyangensis, an Early Cretaceous stem group bird, which includes an intact vomer—the bone that divides the left and right airways in the inner part of the nose. The authors used high-resolution CT scans to reconstruct a 3D model of the vomer for Sapeornis and for the bird-like dinosaur Sinovenator changii, and reconstructed the palate of Sapeornis. Analysis of the palates of extant birds revealed that the 2 major divisions, Palaeognathae and Neognathae, exhibit distinct vomer morphologies, with cranial kinesis being more developed in the latter. Sinovenator and Sapeornis vomer morphology resembled that of Palaeognathae, suggesting that these 2 extinct species exhibited limited, if any, cranial kinesis. Sapeornis also featured an ectopterygoid bone, which is present in nonavian dinosaurs but not in extant birds, further supporting the existence of limited cranial kinesis in Sapeornis. The results suggest that the cranial kinesis observed in modern birds originated within the Neognathae and may have facilitated the diversification and evolutionary success of this lineage, according to the authors. — B.D.

Using spatial information in DNA for microscopy

Image of the Mona Lisa reconstructed using polonies. Adapted from Da Vinci, Leonardo. 1503–1506. Mona Lisa. Oil on wood. Paris: Musée du Louvre.

Spatial information at microscopic scales, such as the relative positions of biomolecules, can be encoded in DNA sequences, transmitted using next-generation sequencing, and reconstructed computationally into images. Ian Hoffecker et al. (pp. 19282–19287) describe a mathematical framework for generating images without conventional optics by using DNA sequencing and graph theory to encode spatial information. The method relies on unique seed DNA that is locally amplified, generating numerous polymerase colonies or “polonies.” Each polony has a distinct DNA barcode sequence associated with a specific spatial location, and the authors cross-linked strands from adjacent colonies so that they were marked by unique barcode pairs. By recovering DNA strands from a surface and subjecting them to next-generation sequencing, the authors reconstructed information about the topological network of adjacent polonies and their spatial distribution on a surface. The authors demonstrated an in silico proof of concept by simulating polony distributions, assembling them into a topological network, and reconstructing the spatial characteristics of the original seed distribution, which could then be used to generate images. DNA-sequencing–based microscopy can help reconstruct whole images without using optics, and the technique can achieve greater levels of automation and multiplexing than current microscopy techniques, according to the authors. — S.R.

Melt-rich rock from Chicxulub impact crater

Liftboat Myrtle, site of the expedition to drill into Chicxulub impact crater.

The Chicxulub asteroid impact approximately 66 million years ago marked the boundary between the Mesozoic and Cenozoic Eras and likely caused the associated mass extinction event. To better understand the immediate aftermath of the impact, Sean Gulick et al. (pp. 19342–19351) analyzed a core from the peak ring of the Chicxulub impact crater, a circle of elevated topography surrounding the center of the crater, containing approximately 130 m of impact melt rock and melt-bearing breccia deposited on the first day following the impact. Based on the analysis, the authors inferred that the bottom 40- to 50-m impact melt and breccia were rapidly deposited within minutes of the impact. Another 90 m of material was deposited by ocean water flowing back into the crater and the subsequent settling of debris over a period of hours. The top layer of the deposit contained soil biomarkers, suggesting that the tsunami caused by the impact was reflected back to the impact site during the first day, bringing terrestrial material with it. The presence of charcoal in the uppermost layers suggests the existence of impact-induced wildfires, whereas the absence of sulfur-rich evaporites from the deposit suggest that the impact released a large amount of sulfate aerosols that could have caused global cooling and darkening, according to the authors. — B.D.

Neandertal footprints and social structure

Neandertal footprint discovered at Le Rozel.

Fossil footprints represent a snapshot in time because they are preserved only when rapidly buried. Jérémy Duveau et al. (pp. 19409–19414) analyzed hundreds of 80,000-year-old fossilized hominin footprints in Normandy, France, to provide a glimpse into the social structure of Neandertals. The 257 footprints analyzed at the Le Rozel site lie in a coastal creek bed and were likely preserved by wind-driven sand when the area was part of a dune system. Though the authors did not find hominin bones at the site, they uncovered stone tools of similar age and characteristics to those found at other European Neandertal sites. The authors note that the prints are consistent with known Neandertal foot morphology and underscore that Neandertals would have been the only hominin in Western Europe at the time. Morphometric analysis of the 104 best-preserved footprints revealed that the prints were likely made by 10–14 individuals. Analysis of the length and width of the prints suggested that most of the prints belonged to adolescents and children, with the youngest estimated to be 2 years of age. According to the authors, the footprints provide an unusual window into Neandertal group size and composition. — T.H.D.

Uncovering factors underlying female infertility

One major contributor to female infertility is embryo implantation failure due to defects in decidualization, the process by which endometrial stromal cells transform into decidual cells. Genetic factors affecting decidualization have not been systematically investigated due to the lack of a suitable high-throughput screening tool. Meade Haller, Yan Yin, et al. (pp. 19541–19551) developed a high-throughput reporter cell line to identify genetic and chemical modulators of human decidualization. The authors constructed a reporter transgene consisting of the coding sequence for yellow fluorescent protein and the human prolactin promoter and introduced the construct into immortalized human endometrial stromal cells. Exposure to a hormone cocktail increased the expression of prolactin, a decidualization marker, as visualized by fluorescence microscopy. The authors used genome-wide small interfering RNA libraries to systematically interfere with the expression of 32,000 genes and exposed the cells to 910 small molecules and monitored the molecules’ effects on decidualization. The experiments revealed more than 4,200 decidualization modulators, including olfactory receptors, growth factors, kinases, and transcription factors, with a heavy representation of signaling molecules and receptors. According to the authors, the reporter cell line could be used to identify novel treatment strategies for impaired female fertility. — J.W.

Food consumption during Great Irish Famine

Destitution in Ireland. Failure of the potato crop. Illustration published in Pictorial Times, August 22, 1846. Image courtesy of the National Library of Ireland.

Nearly 1 million people in Ireland died as a consequence of the Great Famine of 1845–1852, when a fungal blight destroyed the potato crop on which nearly half the population depended for subsistence. Jonny Geber, Monica Tromp, Ashley Scott, et al. (pp. 19380–19385) explored food availability and consumption patterns among the victims. The authors analyzed dental calculus from 42 skeletons of people aged approximately 13 years and older and who died in the Kilkenny Union Workhouse during the famine. Microparticle analysis identified corn as the predominant source of starch granules in the calculus. Analysis of the protein content of calculus from a subset of individuals identified the frequent presence of the milk protein beta-lactoglobulin, as well as the occasional presence of the egg protein ovalbumin. The predominance of corn and milk is consistent with historical accounts of the Irish laborer’s diet during the famine, when potatoes were typically replaced with imported corn. The presence of eggs—typically consumed only by relatively affluent social classes—suggests that the victims had varying prefamine experiences. According to the authors, the results suggest how dental calculus can provide information about diet in historical populations. — B.D.

View Abstract