GOING DEEPER INTO MODERN AND FOSSIL CROCODILIAN TOOTH MICROANATOMY: WHAT CAN BE INFERRED OF PALAEOENVIRONMENT AND TAPHONOMY FROM HISTOCHEMICAL ANALYSES?

Teeth provide information about the evolutionary pathway of an organism, its biology and habitat. This is the case even of fossilized teeth, since they have perdurable biomineralized structures, as biological apatite. The material that has been selected for this study comprises teeth from modern crocodilian individuals and extinct Cretaceous crocodylomorphs from Lo Hueco site. Microanatomy, histochemistry and crystallographic nature of enamel, dentine and cementum have been characterized by Polarized Light Microscopy, SEM-EDS, Confocal Raman Spectroscopy and SR-µXRD. A focus has been made on dentine lamination. In the fossil sample short-period incremental lines show alternate presence of dentinal tubules that has not been described previously either in living or fossil archosaur. This could be related to influence of environmental circadian rhythms in the abundance, size and/or activity of cells depositing dentine in the day-night cycle. Regarding histochemical and crystallographic compositions, the major and mostly unique phase is HA, but in the case of fossil teeth, a secondary phase identified as hematite appears locally between discontinuities of the material. Incremental lines would not be related to variation in chemical composition and furthermore do not present different HA crystallographic nature (different directions of HA or different crystallite sizes) either. Only small intensity oscillations are observed in the fossil sample by SR-µXRD which are compatible with the alternating abundance of dentinal tubules. Crystallinity differences between modern and fossil material, as crystallite size and presence of CO32- groups could be explained by postdepositional processes.

Synchrotron X-ray microdiffraction to study dental structures in Cretaceous crocodylomorphs

Synchrotron radiation X-ray microdiffraction (SR-μXRD) has been applied for the first time as a fundamental method of analysis to unveil crocodilian teeth growth and development. Teeth from a fossil crocodylomorph from the Upper Cretaceous site of Lo Hueco (Spain) and a modern crocodylian from the living species Crocodylus niloticus have been analysed. Both samples have been studied through Polarized Light Microscopy, Scanning Electron Microscopy coupled with Energy Dispersive X-Ray Spectroscopy, Confocal Raman Spectroscopy, and SR-μXRD. Significant differences have been found in hydroxyapatite (HA) crystallite sizes and texture, and the evolution of these two features along teeth depth. The main differences observed in crystallite size are related to postdepositional processes and/or the environmental and functional pressures of teeth during crocodylomorph life, very different from that of the modern specimen. Regarding the crystalline texture in the tooth enamel, it can be linked to teeth functionality during crocodilian life, causing the directed growth of HA crystallites due to the mechanical stress to which they are subjected

Mercury in archaeological human bone: biogenic or diagenetic?

We investigated mercury (Hg) in human bone from archaeological sites in the Iberian Peninsula where the cultural use of cinnabar (HgS) as a pigment, offering or preservative in burial practices has been documented from the 4th to 2nd millennia cal B.C. (Late Neolithic, Copper Age and Bronze Age). Previous analyses have shown high levels of total mercury (THg) in human bone at numerous Neolithic and Chalcolithic sites in this region, but the question remains if this mercury entered the bones via diagenetic processes in the soil, especially where cinnabar powder and paint was found associated with the burials, or if it entered the bone via biogenic pathways from exposure to mercury from using cinnabar in life. We analyzed the humerus, femur, and tibia from a total of 30 individual burials from four Neolithic to Bronze Age sites in Iberia and found low to high values of THg in these bones, with the humerus showing significantly more THg concentrations than other skeletal elements when the THg was greater than 1 ppm. This pattern of Hg deposition in skeletal material from different sites and ages strongly suggests a biogenic origin for the mercury. In addition, absence of detectable Hg in bones with high to low values of THg using SEM EDS analysis further discounts diagenetic intrusion of Hg or cinnabar particles into the bone from the soil. It is likely that greater stress and bone remodeling rates from use of heavy tools and other activities in life are responsible for higher THg in the humerus than other skeletal elements, but additional research is needed to verify this.National Science FoundationNational Science Foundation (NSF) [ECCS-1542174]Spanish GovernmentSpanish Government [HAR2016-78036-P, HAR2016-74846-P, HAR2017-82755-P, HAR2017-83004-P, I + D HAR2017-87324-P]CIAS [PEst-OE/SADG/UI0283/2019]FCTPortuguese Foundation for Science and Technology [PTDC/EPH-ARQ/0798/2014]info:eu-repo/semantics/publishedVersio

Covariation between the shape and mineralized tissues of the rib cross section in Homo sapiens, Pan troglodytes and Sts 14

DATA AVAILABILITY STATEMENT : The data that support the findings of this study are available upon reasonable request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.OBJECTIVES : Studying rib torsion is crucial for understanding the evolution of the hominid ribcage. Interestingly, there are variables of the rib cross section that could be associated with rib torsion and, consequently, with the morphology of the thorax. The aim of this research is to conduct a comparative study of the shape and mineralized tissues of the rib cross section in different hominids to test for significant differences and, if possible, associate them to different thoracic morphotypes. MATERIALS AND METHODS : The sample consists of the rib cross sections at the midshaft taken from 10 Homo sapiens and 10 Pan troglodytes adult individuals, as well as from A. africanus Sts 14. The shape of these rib cross sections was quantified using geometric morphometrics, while the mineralized tissues were evaluated using the compartmentalization index. Subsequently, covariation between both parameters was tested by a Spearman's ρ test, a permutation test and a linear regression. RESULTS : Generally, P. troglodytes individuals exhibit rib cross sections that are rounder and more mineralized compared to those of H. sapiens. However, the covariation between both parameters was only observed in typical ribs (levels 3–10). Although covariation was not found in the rib cross sections of Sts 14, their parameters are closer to P. troglodytes. DISCUSSION : On the one hand, the differences observed in the rib cross sections between H. sapiens and P. troglodytes might be related to different degrees of rib torsion and, consequently, to different thoracic 3D configurations. These findings can be functionally explained by considering their distinct modes of breathing and locomotion. On the other hand, although the rib cross sections belonging to Sts 14 are more similar to those of P. troglodytes, previous publications determined that their overall morphology is closer to modern humans. This discrepancy could reflect a diversity of post-cranial adaptations in Australopithecus.Consejo Superior de Investigaciones Científicas; DST-NRF; Leakey Foundation; Spanish Ministry of Economy, Industry and Competitivity; Spanish Ministry of Science and Innovation.http://wileyonlinelibrary.com/journal/ajpahj2024AnatomySDG-03:Good heatlh and well-bein

Paleoenvironmental reconstruction of the “Lo Hueco” Fossil Site (Upper Cretaceous, Cuenca, Spain): Preliminary stable isotope analyses on crocodilians and dinosaurs

Stable isotope analyses (δ18OPO4, δ18OCO3, and δ13C) are reported for the first time on crocodilian, theropod, and sauropod teeth from two stratigraphic levels (G1 and G2) from the late Campanian–early Maastrichtian “Lo Hueco” fossil site (Cuenca, Spain) in order to better understand paleoclimatic and paleoenvironmental conditions existing in the Iberian Peninsula during the Late Cretaceous. Diagenetic alteration was evaluated using three tests: (1) consistent differences in enamel and dentine δ18OPO4 values, (2) crocodilian δ18OPO4 values consistently lower than dinosaur δ18OPO4 values in agreement with the proposed latitudinal distribution between ectotherms and endotherms, and (3) a Δδ18OCO3-PO4 value of 9.1 ± 1.7‰ for dinosaurs in accordance with the expected equilibrium fractionation between carbonate and phosphate in unaltered modern mammalian bioapatite. Calculated δ18OH2O values are slightly higher in crocodilians compared to dinosaurs since semiaquatic ectothermic taxa δ18OH2O represents local meteoric waters in a brief window of time when the conditions are favorable for apatite synthesis, whereas terrestrial endothermic taxa δ18OH2O records ingested water year-round. Mean air temperature calculated using crocodilian and dinosaur δ18OH2O values shows an increase between G1 and G2, which may be related to differences in the sedimentological setting and/or to a shift toward warmer conditions over time. Finally, the sauropod mean δ13C value (−11.1 ± 0.2‰, VPDB) is in the predicted range for C3 vegetation

Vegetal preservation in the “Lo Hueco” fossil site (Cuenca, Spain)

Preservación Vegetal en el yacimiento Lo Hueco (Cuenca, España

ΔTWMs-MAT (°C) <i>vs</i> latitude (°) for “Lo Hueco” (black dotted arrow), Late Cretaceous eastern Tethyan rudists from Steuber [36] and Steuber <i>et al</i>. [38] (black square), and modern meteorological stations located at latitudes 25° to 35° in both hemispheres from Africa (grey square), Asia (crossed square), North America (grey triangle), South America (grey circle), and Southwest Pacific (grey diamond).

<p>Absolute latitude is shown including North and South hemispheres.</p

Comparison between isotopic values of “Lo Hueco” crocodyliforms and modern crocodilians.

<p>A) δ¹⁸O_CO3 (‰ VSMOW) <i>vs</i> δ¹³C (‰ VPDB) mean ± 1 standard deviation (SD) values of the “Lo Hueco” crocodyliforms (black circle), and modern inland <i>Alligator mississippiensis</i> (grey triangle), coastal <i>Alligator mississippiensis</i> (grey square) and <i>Crocodylus acutus</i> (grey diamond) [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0119968#pone.0119968.ref107" target="_blank">107</a>]. B) SD δ¹⁸O_CO3 (‰ VSMOW) <i>vs</i> δ¹³C (‰ VPDB) values of the “Lo Hueco” crocodyliforms and modern crocodilians (symbols as in A).</p

δ¹⁸O_PO4 (‰ VSMOW) values of “Lo Hueco” vertebrates.

<p>Theropods (triangles), sauropods (squares), crocodyliforms (circles), turtles (diamonds), and gars (crosses). Large black symbols represent mean δ¹⁸O_PO4 values.</p

Fractionation between herbivore enamel and herbivore diet (Δ¹³C_enamel-diet).

<p>“Lo Hueco” bulk organic matter and sauropod mean ± 1 SD δ¹³C (‰ VPDB) (black). Two Medicine (TM), Judith River (JR), Dinosaur Park (DP), and Hell Creek (HC) Formations bulk organic matter and ceratopsian and hadrosaur mean ± 1 SD δ¹³C (‰ VPDB) (grey) [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0119968#pone.0119968.ref025" target="_blank">25</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0119968#pone.0119968.ref026" target="_blank">26</a>]. “Lo Hueco” Δ¹³C_enamel-diet is 15‰, when analysing sauropods, whereas Fricke and Pearson [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0119968#pone.0119968.ref025" target="_blank">25</a>] and Fricke <i>et al</i>. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0119968#pone.0119968.ref026" target="_blank">26</a>] obtained a value of 18‰ when analysing ceratopsians and hadrosaurs. Note different frequency scale for “Lo Hueco” (black) and Fricke and Pearson [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0119968#pone.0119968.ref025" target="_blank">25</a>] and Fricke <i>et al</i>. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0119968#pone.0119968.ref026" target="_blank">26</a>]´s data (grey).</p