Growth Marks Research Articles

In Case You Haven't Heard…

Could kids' teeth help diagnose mental health issues? Dr. Erin Dunn, a social and psychiatric epidemiologist at Massachusetts General Hospital in Boston, and her team are exploring new ways to help diagnose and treat mental health issues by focusing on children's teeth, 2News Oklahoma reported March 25. Dr. Dunn's latest study is centered around the 2013 Boston Marathon bombing. Dr. Dunn and her team are trying to find women who lived in the New England area and were pregnant or had already given birth when those terrorist attacks happened. Their hope is to see if the trauma of the marathon bombing left behind any kind of clues. As baby teeth form, they develop microscopic growth marks, almost like the rings of a tree. Researchers are hoping to analyze those teeth from around the time of the bombing. They're looking for things like enamel thickness or abnormalities, which could be signs of trauma. “The idea is that teeth might have these imprints that tell us about our early life history,” Dunn said. Her ultimate hope is that teeth could better predict kids' mental health issues later in life.

Osteohistology of the hyperelongate hemispinous processes of Amargasaurus cazaui (Dinosauria: Sauropoda): Implications for soft tissue reconstruction and functional significance.

Dicraeosaurid sauropods are iconically characterized by the presence of elongate hemispinous processes in presacral vertebrae. These hemispinous processes can show an extreme degree of elongation, such as in the Argentinean forms Amargasaurus cazaui, Pilmatueia faundezi and Bajadasaurus pronuspinax. These hyperelongated hemispinous processes have been variably interpreted as a support structure for a padded crest/sail as a display, a bison-like hump or as the internal osseous cores of cervical horns. With the purpose to test these hypotheses, here we analyze, for the first time, the external morphology, internal microanatomy and bone microstructure of the hemispinous processes from the holotype of Amargasaurus, in addition to a second dicraeosaurid indet. (also from the La Amarga Formatin; Lower Cretaceous, Argentina). Transverse thin-sections sampled from the proximal, mid and distal portions of both cervical and dorsal hemispinous processes reveal that the cortical bone is formed by highly vascularized fibrolamellar bone interrupted with cyclical growth marks. Obliquely oriented Sharpey's fibres are mostly located in the medial and lateral portions of the cortex. Secondary remodelling is evidenced by the presence of abundant secondary osteons irregularly distributed within the cortex. Both anatomical and histological evidence does not support the presence of a keratinized sheath (i.e. horn) covering the hyperelongated hemispinous processes of Amargasaurus, and either, using a parsimonious criterium, in other dicraeosaurids with similar vertebral morphology. The spatial distribution and relative orientation of the Sharpey's fibres suggest the presence of an important system of interspinous ligaments that possibly connect successive hemispinous processes in Amargasaurus. These ligaments were distributed along the entirety of the hemispinous processes. The differential distribution of secondary osteons indicates that the cervical hemispinous processes of Amargasaurus were subjected to mechanical forces that generated higher compression strain on the anterior side of the elements. Current data support the hypothesis for the presence of a 'cervical sail' in Amargasaurus and other dicraeosaurids.

Deep learning and machine learning neural network approaches for multi class leather texture defect classification and segmentation

Modern leather industries are focused on producing high quality leather products for sustaining the market competitiveness. However, various leather defects are introduced during various stages of manufacturing process such as material handling, tanning and dyeing. Manual inspection of leather surfaces is subjective and inconsistent in nature; hence machine vision systems have been widely adopted for the automated inspection of leather defects. It is necessary develop suitable image processing algorithms for localize leather defects such as folding marks, growth marks, grain off, loose grain, and pinhole due to the ambiguous texture pattern and tiny nature in the localized regions of the leather. This paper presents deep learning neural network-based approach for automatic localization and classification of leather defects using a machine vision system. In this work, popular convolutional neural networks are trained using leather images of different leather defects and a class activation mapping technique is followed to locate the region of interest for the class of leather defect. Convolution neural networks such as Google net, Squeeze-net, RestNet are found to provide better accuracy of classification as compared with the state-of-the-art neural network architectures and the results are presented.Graphical

Accuracy and Precision of Otolith‐Derived Age Interpretations for Known‐Age Lake Trout

AbstractCatch‐at‐age data are used to inform important management decisions for recovering populations of Lake Trout Salvelinus namaycush. Age data for Lake Trout are commonly derived from interpretation of annual growth marks (annuli) on the fish’s otoliths. Due to the tendency for annuli to vary in appearance and the subjectivity that is inherent to any age interpretation method, it is important that the common sources of interpretation error be well understood for any aging method used to inform management plans. In this study, coded wire tags were used to establish true ages for 153 Lake Trout to measure the precision and accuracy of age interpretations made from transverse‐sectioned otoliths and to identify sources of potential age interpretation error that researchers and managers may encounter when using this method. Precision of age interpretations, as measured by average coefficient of variation, ranged from 7.9% to 9.2%. Accuracy of age interpretations varied among readers, with exact matches ranging from 41.8% to 53.6% and accuracy within ±1 year ranging from 81.0% to 83.0%. Age interpretation errors were more likely to be overestimates of true age for Lake Trout under age 7 and underestimates for Lake Trout over age 13. However, only reader 1 exhibited significant systematic bias in their age interpretations. Poor clarity of the first annuli, growth checks resembling annuli, and faintness of narrow annuli near otolith margins in older fish were identified as likely sources of interpretation error in this study. A digital reference collection of known‐age Lake Trout otoliths is provided as supplemental material in the online version of this article. This collection can be used for training new readers, measuring the accuracy of age interpretations, and monitoring for aging bias by anyone using otoliths to obtain age data for Lake Trout.

AGE AND GROWTH OF Papyrocranus afer (GUNTHER 1868), AN EMERGING ORNAMENTAL FISH IN NIGERIA

Papyrocranus afer are threatened by increasing collection from the wild for aquaria, especially the juveniles. Age, growth and growth derived parameters of P. afer Lagoon based on analysis Length Frequency Distribution (LFD) and interpretation of annual growth marks hard structures (namely scales, otoliths, opercula and cleithra). In total, 1, 154 individuals of P. afer were sampled monthly during Jan. 2010 to Dec. 2011 from Lekki Lagoon. The mean lengths-at-ages from LFD were 13.45 cm (Age 0+) 34.45 cm (Age 1+), 49.50 cm (Age 2+) and 61cm (Age 3+). The von bertalanffy growth function was used to model the observed length-at-age data: Lt = 77.6 (1 – e-0.33(t +0.46)). Length at first maturity (Lm) was 41.1cm while length at optimum yield (Lopt) was 49.5cm. Preponderance of immature fishes (38 cm) in the catch suggests growth overfishing. Interpretable annual growth marks on hard parts showed ages 1, 2 and 3 years; the mean lengths at these ages were 33.1, 44.6 and 58.4cm (cleithra), 29.1, 40.0 and 60.4 (scale) and 29.1, 40.0 and 60.4 (operculum). No interpretable growth marks on otoliths. Growth overfishing underline vulnerability of Papyrocranus afer to over-exploitation, hence the need for its conservation in Lekki Lagoon.

Bone histology on Koreaceratops hwaseongensis (Dinosauria: Ceratopsia) from the Lower Cretaceous of South Korea

Koreaceratops hwaseongensis is a basal ceratopsian dinosaur found in the Lower Cretaceous Sihwa Formation (Albian), South Korea. It was found only with the lower part of the body. The right tibia and fibula exhibit poor histological preservation due to microbial degradation. They are characterized by signs of extensive tunneling by microorganisms, which rendered the bone cortex into an amalgam of microscopical globules and foci. Such signs of biodegradation may support the hypothesis that the Lower Cretaceous Korean peninsula had a semi-arid and seasonal wet-dry climate. However, a few remaining traces of histological features like the vasculature and absence/presence of growth marks indicate that the growth pattern of Koreaceratops is very similar to that of a subadult Protoceratops andrewsi. Both species exhibit zonation with some bone remodeling in their tibiae and lines of arrested growth with an extensive bone remodeling in their fibulae. The only histological similarity between Koreaceratops and the more basal ceratopsians Psittacosaurus is the longitudinal and reticular vasculature in their fibulae. These suggest that Koreaceratops is much closer to Protoceratops than Psittacosaurus in terms of phylogeny. The fibula of Koreaceratops shows a constant osseous drift that initially drifted toward the medial axis but abruptly changed to the anterior axis in the final growth interval. In addition, the right tibia's final growth exhibiting an anteromedial osseous drift suggests that Koreaceratops experienced a change in its right hindlimb's biomechanics before death. The number of growth zones in the tibia indicates that Koreaceratops was approximately eight years old when it died.

Age validation and contrasted growth performances of Pseudoplatystoma punctifer (Siluriformes: Pimelodidae) in two river systems of the Western Amazon

Abstract The doncella Pseudoplatystoma punctifer is an economically and ecologically important catfish in the Amazon basin. However, little is known about its age, growth and population dynamics parameters. This study aims to validate the formation of growth marks in vertebrae of individuals collected from two rivers systems of the Peruvian Amazon (Amazon-Marañón-Ucayali and Putumayo) and compare growth parameters using the von Bertalanffy growth function between sexes and systems. A total of 372 individuals from the Amazon-Marañón-Ucayali (AMU) system and 93 from the Putumayo River were analyzed. The formation of one growth ring per year was validated and the individual ages ranged from zero to nine years old. Females grew significantly larger than males in both systems. Both females and males grew significantly better in the AMU system than in the Putumayo River. Maximum observed length and size at maturity in the AMU system were lower than those reported in previous studies in the area, and together with an important proportion of juveniles in the catches, suggest that the species is heavily exploited. Further studies on the reproductive biology and population dynamics of the doncella are needed in order to implement management measures more in line with the current situation.

First osteohistological and histotaphonomic approach of Equus occidentalis Leidy, 1865 (Mammalia, Equidae) from the late Pleistocene of Rancho La Brea (California, USA).

Rancho La Brea (California, USA) is the most emblematic Quaternary fossiliferous locality in the world, since both the high number and diversity of the specimens recovered and their excellent preservational quality. In the last decades, paleobiological and paleoecological knowledge of the different groups of mammals from this site has increased notably; however, some aspects have not yet been inquired or there is little information. In this work we provide information on one of the most abundant mammals of this site, the equid Equus occidentalis, based on the study, from osteohistological and histotaphonomic perspectives, of thin sections of different limb bones. On the one hand, from an osteohistological viewpoint, we observe that the distribution and characterization of bone tissues in the different skeletal elements are, in general lines, similar to that mentioned for other extant and extinct equids. Cyclical growth marks allowed us to propose preliminary skeletochronological interpretations. On the other hand, from a taphonomic viewpoint, we note that all the samples reflect an excellent preservation of the bone microstructure, slightly altered by different pre- and post-burial processes. The variations recorded evidence different taphonomic history and preservation conditions among pits. This is the first study including fossil material from Rancho La Brea exclusively based on the analysis of the bone microstructure features.

Osteohistology of non-mammalian therapsids from Puesto Viejo Group, Argentina

ABSTRACT The Puesto Viejo Group is an important unit for the knowledge Triassic faunas especially non-mammalian therapsids. This group crops out in the San Rafael Block, southwest Mendoza, Argentina. It is composed of the basal Quebrada de los Fósiles Formation (QF) which is overlaid by the Río Seco de la Quebrada Formation (RSQ). This report comprises tetrapod remains from the RSQ Formation at the Quebrada del Durazno area that includes, until now, exclusively therapsids. The aim of this study is to analyse the bone microstructure of cynodonts and dicynodonts to elucidate the histological features and growth patterns. Histological thin sections made in ribs and appendicular bones reveal a predominance of fibrolamellar bone tissue suggesting an overall fast bone growth, however, the presence of parallel-fibred bone suggest periods of slowing down of the growth. The existence of growth marks indicates periodic interruptions of growth, which is likely the expression of their ability to rapid respond to environmental changes. This contribution offers new insights into the bone microstructure of tetrapod assemblages from RSQ Formation during the Upper Triassic span.

Association of Maternal Stress and Social Support During Pregnancy With Growth Marks in Children’s Primary Tooth Enamel

Exposure to maternal psychosocial stressors during the prenatal and perinatal periods can have major long-term mental health consequences for children. However, valid and inexpensive biomarkers are currently unavailable to identify children who have been exposed to psychosocial stress and the buffers of stress exposure. To assess whether a growth mark in tooth enamel, the neonatal line, is associated with exposure to prenatal and perinatal maternal psychosocial factors. This prospective cohort study used exfoliated primary canine teeth and epidemiological survey data from 70 children enrolled in the Avon Longitudinal Study of Parents and Children, a birth cohort based in Bristol, England. Exfoliated teeth were collected from children at 5 to 7 years of age. Data were collected from January 1, 1991, to December 31, 1998, and were analyzed from January 1, 2019, to August 10, 2021. Four types of prenatal and perinatal maternal psychosocial factors were studied: stressful life events, psychopathological history, neighborhood disadvantage, and social support. Data were collected from mailed-in questionnaires completed during and shortly after pregnancy. Neonatal line width measured within 3 portions of the tooth crown (the cuspal, middle, and innermost third) in exfoliated primary canines. A total of 70 children (34 of 70 [48.7%] male; 63 of 67 [94.0%] White) were studied. Most children were born full term (57 [83.8%]) and to mothers of typical child-bearing age (60 [88.2%]). Neonatal lines were wider in the canines of children born to mothers who self-reported severe lifetime depression (β = 3.35; 95% CI, 1.48-5.23; P = .001), any lifetime psychiatric problems (β = 2.66; 95% CI, 0.92-4.41; P = .003), or elevated anxiety or depressive symptoms at 32 weeks' gestation (β = 2.29; 95% CI, 0.38-4.20; P = .02). By contrast, neonatal lines were narrower in children born to mothers who self-reported high social support shortly after birth (β = -2.04; 95% CI, -3.70 to -0.38; P = .02). The magnitude of these associations was large, up to 1.2 SD unit differences, and persisted after adjusting for other risk factors. In this cohort study, neonatal line width was associated with exposure to maternal perinatal psychosocial factors. Replication and validation of these findings can further evaluate teeth as possible new biomarkers.

Living fast in the Triassic: New data on life history in Lystrosaurus (Therapsida: Dicynodontia) from northeastern Pangea.

Lystrosaurus was one of the few tetrapods to survive the Permo-Triassic mass extinction, the most profound biotic crisis in Earth's history. The wide paleolatitudinal range and high abundance of Lystrosaurus during the Early Triassic provide a unique opportunity to investigate changes in growth dynamics and longevity following the mass extinction, yet most studies have focused only on species that lived in the southern hemisphere. Here, we present the long bone histology from twenty Lystrosaurus skeletal elements spanning a range of sizes that were collected in the Jiucaiyuan Formation of northwestern China. In addition, we compare the average body size of northern and southern Pangean Triassic-aged species and conduct cranial geometric morphometric analyses of southern and northern taxa to begin investigating whether specimens from China are likely to be taxonomically distinct from South African specimens. We demonstrate that Lystrosaurus from China have larger average body sizes than their southern Pangean relatives and that their cranial morphologies are distinctive. The osteohistological examination revealed sustained, rapid osteogenesis punctuated by growth marks in some, but not all, immature individuals from China. We find that the osteohistology of Chinese Lystrosaurus shares a similar growth pattern with South African species that show sustained growth until death. However, bone growth arrests more frequently in the Chinese sample. Nevertheless, none of the long bones sampled here indicate that maximum or asymptotic size was reached, suggesting that the maximum size of Lystrosaurus from the Jiucaiyuan Formation remains unknown.

Bone histology of dinocephalians (Therapsida, Dinocephalia): palaeobiological and palaeoecological inferences

AbstractWe investigate the bone histology of multiple skeletal elements of dinocephalian taxa from the middle PermianTapinocephalusAssemblage Zone of the Karoo Basin of South Africa. The results show that the cortex is predominantly composed of fibrolamellar bone, suggesting rapid osteogenesis for these basal non‐mammalian therapsids. However, in a few skeletal elements, growth marks interrupt the deposition of the fibrolamellar bone tissue, indicating periodic arrests in growth. Ontogenetic differences are observed among the specimens studied: the majority have fibrolamellar bone deposited up to the peripheral margin of the bone wall, indicating continuous fast growth right up to the time of death, while a few specimens have avascular lamellar bone tissue with multiple, closely spaced rest lines, indicating maturity and a slowing down of growth prior to death. Several taxon‐specific histological variations in terms of orientation of vascular canals and primary osteons, incidence of growth marks, and extent of secondary medullary reconstruction suggest slight differences in growth trajectories between the different taxa. The skeletal elements of the herbivorous taxa (Keratocephalus,MoschopsandStruthiocephalus) and the omnivorousJonkeria, previously studied, are characterized by a thick cortex, and extensively developed medullary spongiosa, suggestive of semi‐aquatic habits. In contrast, the femoral histology of the carnivorousAnteosaurussuggests that it was more terrestrial.

Growth variability, dimensional scaling, and the interpretation of osteohistological growth data.

Osteohistological data are commonly used to study the life history of extant and extinct tetrapods. While recent advances have permitted detailed reconstructions of growth patterns, physiology and other features using these data, they are most commonly used in assessments of ontogenetic stage and relative growth in extinct animals. These methods have seen widespread adoption in recent years, rapidly becoming a common component of the taxonomic description of new fossil taxa, but are often applied without close consideration of the sources of variation present or the dimensional scaling relationships that exist among different osteohistological measurements. Here, we use a combination of theoretical models and empirical data from a range of extant and extinct tetrapods to review sources of variability in common osteohistological measurements, their dimensional scaling relationships and the resulting interpretations that can be made from those data. In particular, we provide recommendations on the usage and interpretation of growth mark spacing/zonal thickness data, when these are likely to be unreliable, and under what conditions they can provide useful inferences for studies of growth and life history.

Skeletochronology and Paleohistology of Hyposaurus rogersii (Crocodyliformes, Dyrosauridae) from the Early Paleogene of New Jersey, USA.

Simple SummaryThe way of life and biology of extinct animals can be inferred from growth marks and microstructures in their fossil bones. Hyposaurus is a genus representative of dyrosaurids, a group of crocodile-like animals that survived the extinction event that killed the dinosaurs but nonetheless has long become extinct. The current study focuses on bone sections from a single individual, extracted from the optimal location in the best bones for such studies. It complements and corrects previous works based on less optimal material, and concludes that the genus was a marine ambush predator rather than a fast-swimming pursuit predator, that the males of the genus grew larger than the females, and that the individual studied was a fully mature 17–18-year-old female.The paleohistology of dyrosaurids is known from a small sample, despite being common fossils and representing a rare lineage of crocodylomorphs that survived the Cretaceous–Paleogene extinction. Their lifestyle has been inferred only from sections of the snout, vertebrae, partial femur, and tibia. To improve this, we conducted a skeletochronological and paleohistological study of midshaft cross-sections of both femora and humeri of a nearly complete Hyposaurus rogersii skeleton. We found lamellar-zonal bone that underwent remodeling, evidenced by resorption cavities and abundant secondary osteons within the primary periosteal cortex. The osteons, mostly longitudinally oriented and arranged in circular rows, often anastomose radially along a linear path, resembling radial rows. The medullary cavity is completely open, lacking trabeculae: endosteal deposition is limited to thin lamellae surrounding the cavity. Analysis of cyclical growth marks and the presence of an external fundamental system indicate the specimen was a fully mature adult 17–18 years of age. Comparison of the skeleton to others suggests sexual dimorphism and that it was female. The open medullary cavity, and no evidence for pachyosteosclerosis, osteosclerosis, osteoporosis, or pachyostosis indicate H. rogersii was not a deep diver or a fast swimmer in the open ocean but a near-shore marine ambush predator.

Inter-element variation in the bone histology ofAnteosaurus(Dinocephalia, Anteosauridae) from theTapinocephalusAssemblage Zone of the Karoo Basin of South Africa

Despite its abundance in the Permian fossil record of South Africa, little is known about the life history of Anteosaurus. Here we examine the bone microstructure of multiple skeletal elements of Anteosaurus from the Tapinocephalus Assemblage Zone of the Karoo Basin. The bone histology of Anteosaurus magnificus reveals that the cortex is composed of highly vascularized, uninterrupted fibrolamellar bone tissue surrounding the inner spongy medullary region. However, the histology of two ribs and a previously described femur of another Anteosaurus taxon revealed an interrupted growth pattern with lines of arrested growth and peripheral rest lines occurring in the compacta, indicating periodic pauses in growth possibly linked to the slowing down of growth during maturity. Given that the fibula of the same individual has well-vascularised fibrolamellar bone tissue without any growth marks in the cortex; this suggests variation in skeletal growth. Based on our histological results, three growth dynamic stages are deduced for the genus Anteosaurus: (i) the earliest growth stage is represented by the predominance of highly vascularized, uninterrupted fibrolamellar bone tissue in the inner cortex, which suggests rapid periosteal bone deposition during early ontogeny; (ii) the next stage of growth shows periodic interruptions in the bone deposition as indicated by the deposition of lines of arrested growth; (iii) the third stage shows the development of lamellar bone tissue with rest lines in the peripheral part of the cortex suggesting a slowing down of growth prior to death. Most of the skeletal elements are characterized by thick bone walls, extensive secondary reconstruction and the complete infilling of the medullary cavity. However, the radius and a previously studied femur have open medullary cavities with struts of bony trabeculae. Based on histologic structures and comparisons with extant taxa, it is likely that Anteosaurus may have been more terrestrial as its osteology point towards terrestriality, but it may have occasionally inhabited ephemeral pools like modern semi-aquatic Hippopotamus.

Osteohistology of Greererpeton provides insight into the life history of an early Carboniferous tetrapod.

The vertebrate transition to land is one of the most consequential, yet poorly understood periods in tetrapod evolution. Despite the importance of the water-land transition in establishing modern ecosystems, we still know very little about the life histories of the earliest tetrapods. Bone histology provides an exceptional opportunity to study the biology of early tetrapods and has the potential to reveal new insights into their life histories. Here, we examine the femoral bone histology from an ontogenetic series of Greererpeton, an early tetrapod from the Middle-Late Mississippian (early Carboniferous) of North America. Thin-sections and micro-CT data show a moderately paced rate of bone deposition with significant cortical thickening through development. An interruption to regular bone deposition, as indicated by a zone of avascular tissue and growth marks, is notable at the same late juvenile stage of development throughout our sample. This suggests that an inherent aspect to the life history of juvenile Greererpeton resulted in a temporary reduction in bone deposition. We review several possible life history correlates for this bony signature including metamorphosis, an extended juvenile phase, environmental stress, and movement (migration/dispersal) between habitats. We argue that given the anatomy of Greererpeton, it is unlikely that events related to polymorphism (metamorphosis, extended juvenile phase) can explain the bony signature observed in our sample. Furthermore, the ubiquity of this signal in our sample indicates a taxon-level rather than a population-level trait, which is expected for an environmental stress. We conclude that movement via dispersal represents a likely correlate, as such events are a common life history strategy of aquatically bound vertebrates.

What's my age again? On the ambiguity of histology-based skeletochronology.

Histology-based skeletochronology is a widely used approach to determine the age of an individual, and is based on the assumption that temporal cessations or decelerations of bone growth lead to incremental growth marks (GM), reflecting annual cycles. We studied the reliability of histology-based skeletochronology in a variety of extant tetrapods by comparing two different approaches: petrographic ground sections versus stained microtomized sections. Each bone was cut into two corresponding halves at its growth centre in order to apply both approaches to one and the same sample. None of the samples unequivocally revealed the actual age of the specimens, but truly concerning is the fact that the majority of samples even led to conflicting age estimates between the two approaches. Although the microtomized sections tended to yield more GM and thus indicated an older age than the ground sections, the contrary also occurred. Such a pronounced ambiguity in skeletochronological data strongly challenges the value of the respective age determinations for both extant and extinct animals. We conclude that much more research on the fundamental methodological side of skeletochronology-especially regarding the general nature and microscopic recognition of GM-is required.

The osteohistological variability in the evolution of basal avialans

AbstractBasal avialans have been the focus of numerous histological studies in the past decade, from which different osteohistological patterns have been described. In this review, we look at the osteohistology in selected specimens from the four major avian groups: the long‐tailed Avialae (Archaeopteryxand Jeholornithiformes), basal Pygostylia, Enantiornithes and Euornithes. Developmental and evolutionary changes in the three major bone layers are observed throughout the bone cortex of the limbs, may it be interspecific or intraspecific. Most noteworthy is the adaptive change from the overall lamellar/parallel‐fibered bone tissue to a fibrolamellar complex in the mid‐cortex as of the basal Pygostylia, potentially even as of the Jeholornithiformes. This change is generally associated with an increase in the density and complexity of the neurovascular network. Another evolutionary‐developmental feature is the progressive loss of post‐natal growth marks as of the non‐ornithurine Euornithes, indicative of uninterrupted bone growth as observed in extant Neornithes. Our comparisons of the osteohistological patterns allow us to better determine how and when specific features typical observed in the avian crown group developed, associated with external and internal factors, and how they lead to what is commonly observed in extant Neornithes.

Histological investigation of burnt bones: A case study of angulate tortoises from the archaeological site, Diepkloof Rock Shelter, Western Cape, South Africa

AbstractThe current study examined burnt and unburnt tibiae of angulate tortoises from the intermediate and late Howiesons Poort levels at Diepkloof Rock Shelter (DRS) of Western Cape, South Africa, to ascertain heat‐induced osteohistological changes. Three types of bone damage caused by fire were recognized: (a) external color change in the bones but otherwise consistent osteological and histological features to unburnt bones; (b) partially burned bones with osteological features obliterated, but histological details still preserved, and carbon inclusions visible along the bone margins and within pore spaces; and (c) completely burned bones with obliterated osteological features, but overall shape is maintained, and except for the presence of cracks and carbon accumulations within pore spaces and around the periosteal margin, histological features are evident. Comparisons with other studies of burnt bone suggest that the bones at DRS were subjected to high temperatures of about 600°C to 900°C. Despite exposure to fire, histological features were intact in all the bones, permitting life history deductions for these angulate tortoises. During early ontogeny, uninterrupted fibrolamellar bone tissue (indicative of rapid growth rates) was deposited, whereas later in ontogeny, slowly formed parallel‐fibered bone tissue formed and growth ceased periodically. A minimum age of 10 years was deduced for two individuals, and closely spaced growth marks suggest that the sexual maturity was attained at 7–8 years. Based on the comparisons with modern angulate tortoises, it appears that DRS tortoises had slower growth rates, suggesting less optimal environmental conditions for growth prevailed at the time.

Histology and Geochemistry of Allosaurus (Dinosauria: Theropoda) From the Cleveland-Lloyd Dinosaur Quarry (Late Jurassic, Utah): Paleobiological Implications

The Late JurassicAllosaurusis one of the better-studied dinosaurs. A histological and geochemical study of a tibia and a femur ofA. fragilisrecovered in the Upper Jurassic Cleveland-Lloyd Dinosaur Quarry, Utah, United States has been done in order to address growth characteristics of this species. The two bones, probably belonging to separate individuals, are among the largest known for this species, which make them suitable to address such issues. The inclusion of our data on femur growth markings in the previously published data reflects a range of growth variability rather than two distinct growth strategies. The tibia has a well-developed external fundamental system indicating somatic maturity achievement. Using a quantitative method of superimposition to retrocalculate missing lines of arrested growth, the tibia appears to correspond to an individual that reached its skeletal maturity at 22 years and died at approximately 26 years. In the tibia, the concentration of zinc, a potential biomarker associated with bone formation, displays a higher concentration in zones of rapid growth compared to annuli. There is no direct relationship between the values of δ18Opand the lines of arrested growth distribution. The absence of relations between the histological organization and an enrichment in REE of the bone, indicates that the variations of δ18Oplikely represent a diagenetic process rather than a primordial, biologic composition. However, the geochemical composition of the bones is not homogeneous along the sections, indicating that the signal variations have not been completely erased by diagenesis.