Recognizing sexual dimorphism in the fossil record: lessons from nonavian dinosaurs

Paleobiology ◽  
2017 ◽  
Vol 43 (3) ◽  
pp. 495-507 ◽  
Author(s):  
Jordan C. Mallon
Keyword(s):  
Sexual Dimorphism ◽  
Fossil Record ◽  
Statistical Tests ◽  
A Priori ◽  
Mixture Modeling ◽  
Statistical Investigation ◽  
Morphological Data ◽  
Sexually Dimorphic ◽  
Quantitative Evidence ◽  
Evolution Of Life

AbstractThe demonstration of sexual dimorphism in the fossil record can provide vital information about the role that sexual selection has played in the evolution of life. However, statistically robust inferences of sexual dimorphism in fossil organisms are exceedingly difficult to establish, owing to issues of sample size, experimental control, and methodology. This is particularly so in the case of dinosaurs, for which sexual dimorphism has been posited in many species, yet quantifiable data are often lacking. This study presents the first statistical investigation of sexual dimorphism across Dinosauria. It revisits prior analyses that purport to find quantitative evidence for sexual dimorphism in nine dinosaur species. After the available morphological data were subjected to a suite of statistical tests (normality and unimodality tests and mixture modeling), no evidence for sexual dimorphism was found in any of the examined taxa, contrary to conventional wisdom. This is not to say that dinosaurs were not sexually dimorphic (phylogenetic inference suggests they may well have been), only that the available evidence precludes its detection. A priori knowledge of the sexes would greatly facilitate the assessment of sexual dimorphism in the fossil record, and it is suggested that unambiguous indicators of sex (e.g., presence of eggs, embryos, medullary bone) be used to this end.

scholarly journals Seasonal dynamics of dental sexual dimorphism in the Atlantic stingray Dasyatis sabina

1996 ◽  
Vol 199 (10) ◽  
pp. 2297-2306 ◽  
Author(s):  
S Kajiura ◽  
T Tricas
Keyword(s):  
Sexual Dimorphism ◽  
Fossil Record ◽  
Reproductive Season ◽  
Sexually Dimorphic ◽  
Mating Season ◽  
Selective Pressures ◽  
Dasyatis Sabina ◽  
Atlantic Stingray ◽  
Cartilaginous Fishes

Cartilaginous fishes continuously replace their teeth throughout their life (polyphyodonty) and often show a sexually dimorphic dentition that was previously thought to be an invariant sex character. Radial vector analysis of tooth shape in the polyphyodontic stingray Dasyatis sabina across a consecutive 24 month period shows a stable molariform morphology for females but a periodic shift in male dentition from a female-like molariform to a recurved cuspidate form during the reproductive season. The grip tenacity of the male dentition is greater for the cuspidate form that occurs during the mating season than for the molariform dentition that occurs during the non-mating season. Dental sexual dimorphism and its sex-dependent temporal plasticity probably evolved via polyphyodontic preadaptation under selective pressures on both sexes for increased feeding efficiency and sexual selection in males to maximize mating success. These phenomena are important considerations for the identification and classification of cartilaginous fishes and possibly other polyphyodontic vertebrates in the fossil record.

scholarly journals Ontogeny of a sexually selected structure in an extant archosaur Gavialis gangeticus (Pseudosuchia: Crocodylia) with implications for sexual dimorphism in dinosaurs

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9134 ◽  
Author(s):  
David Hone ◽  
Jordan C. Mallon ◽  
Patrick Hennessey ◽  
Lawrence M. Witmer
Keyword(s):  
Sexual Dimorphism ◽  
A Priori ◽  
Small Sample ◽  
Egg Laying ◽  
Sexually Dimorphic ◽  
Large Dataset ◽  
Unique Model ◽  
Small Sample Sizes ◽  
Gavialis Gangeticus ◽  
Slow Growing

Despite strong evidence for sexual selection in various display traits and other exaggerated structures in large extinct reptiles, such as dinosaurs, detecting sexual dimorphism in them remains difficult. Their relatively small sample sizes, long growth periods, and difficulties distinguishing the sexes of fossil specimens mean that there are little compelling data on dimorphism in these animals. The extant gharial (Gavialis gangeticus) is a large and endangered crocodylian that is sexually dimorphic in size, but males also possesses a sexually selected structure, the ghara, which has an osteological correlate in the presence of a fossa associated with the nares. This makes the species a unique model for potentially assessing dimorphism in fossil lineages, such as dinosaurs and pterosaurs, because it is a large, slow-growing, egg-laying archosaur. Here we assess the dimorphism of G. gangeticus across 106 specimens and show that the presence of a narial fossa diagnoses adult male gharials. Males are larger than females, but the level of size dimorphism, and that of other cranial features, is low and difficult to detect without a priori knowledge of the sexes, even with this large dataset. By extension, dimorphism in extinct reptiles is very difficult to detect in the absence of sex specific characters, such as the narial fossa.

Description of the female of Ceromya glaucescens Tachi & Shima (Diptera: Tachinidae) and discovery of unusual sexual dimorphism in this species

Zootaxa ◽  
2017 ◽  
Vol 4237 (3) ◽  
pp. 583
Author(s):  
TAKUJI TACHI
Keyword(s):  
Sexual Dimorphism ◽  
Sequence Data ◽  
Morphological Characters ◽  
Morphological Data ◽  
Compound Eyes ◽  
Sexually Dimorphic ◽  
Separate Species ◽  
Wing Patterns ◽  
Males And Females ◽  
Dimorphic Species

Sexual dimorphism is a phenomenon in which the male and female of a species differ in features of the external morphology such as size, shape, colour, or the development of appendages. In the Diptera, stalked compound eyes, leg modifications and wing patterns are well-known examples of sexual dimorphism (McAlpine 1979; Zeil 1983; Adler & Adler 1991; Meyerrochow & Reid 1994; Wilkinson & Dodson 1996; Sivinski 1997; Baker & Wilkinson 2001; Eberhard 2002; Puniamoorthy et al. 2008). Males and females of sexually dimorphic species are often described as separate species due to the dissimilarity in external characters, thus leading to problems in identification and proper association of the sexes. In contrast to characters that are usually involved in sexual dimorphism, leg chaetotaxy is considered one of the invariable character systems, irrespective of sex, in the tribe Siphonini of the Tachinidae, and is thus widely used in keys to genera and species (O’Hara 1989; Andersen 1996). Species’ identification by DNA barcoding has been used in various groups of organisms (Hebert et al. 2003; Ratnasingham & Hebert 2013). In insects, males, usually more easily identified by morphological characters (e.g., postabdominal features) than females, are often used for barcoding. The identification of females will improve as sequence data accumulate, such as data from pairs collected in copula. In this paper, I describe sexual dimorphism in the Japanese endemic species of tachinid fly Ceromya glaucescens Tachi & Shima, 2000 of the tribe Siphonini, and use molecular and morphological data for the identification of this species. Sequence data of C. silacea (Meigen, 1824) are also included for comparison. 

scholarly journals X chromosome escapee genes are involved in ischemic sexual dimorphism through epigenetic modification of inflammatory signals

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Shaohua Qi ◽  
Abdullah Al Mamun ◽  
Conelius Ngwa ◽  
Sharmeen Romana ◽  
Rodney Ritzel ◽  
...  
Keyword(s):  
Sexual Dimorphism ◽  
X Chromosome ◽  
Epigenetic Modification ◽  
Artery Occlusion ◽  
Sexually Dimorphic ◽  
Mrna Levels ◽  
Young Females ◽  
Human Stroke ◽  
Histone H3k4 ◽  
Cerebral Artery Occlusion

Abstract Background Stroke is a sexually dimorphic disease. Previous studies have found that young females are protected against ischemia compared to males, partially due to the protective effect of ovarian hormones, particularly estrogen (E2). However, there are also genetic and epigenetic effects of X chromosome dosage that contribute to stroke sensitivity and neuroinflammation after injury, especially in the aged. Genes that escape from X chromosome inactivation (XCI) contribute to sex-specific phenotypes in many disorders. Kdm5c and kdm6a are X escapee genes that demethylate H3K4me3 and H3K27me3, respectively. We hypothesized that the two demethylases play critical roles in mediating the stroke sensitivity. Methods To identify the X escapee genes involved in stroke, we performed RNA-seq in flow-sorted microglia from aged male and female wild type (WT) mice subjected to middle cerebral artery occlusion (MCAO). The expression of these genes (kdm5c/kdm6a) were confirmed in four core genotypes (FCG) mice and in post-mortem human stroke brains by immunohistochemistry (IHC), Western blot, and RT-PCR. Chromatin immunoprecipitation (ChIP) assays were conducted to detect DNA levels of inflammatory interferon regulatory factor (IRF) 4/5 precipitated by histone H3K4 and H3K27 antibodies. Manipulation of kdm5c/kdm6a expression with siRNA or lentivirus was performed in microglial culture, to determine downstream pathways and examine the regulatory roles in inflammatory cytokine production. Results Kdm5c and kdm6a mRNA levels were significantly higher in aged WT female vs. male microglia, and the sex difference also existed in ischemic brains from FCG mice and human stroke patients. The ChIP assay showed the IRF 4/5 had higher binding levels to demethylated H3K4 or H3K27, respectively, in female vs. male ischemic microglia. Knockdown or over expression of kdm5c/kdm6a with siRNA or lentivirus altered the methylation of H3K4 or H3K27 at the IRF4/5 genes, which in turn, impacted the production of inflammatory cytokines. Conclusions The KDM-Histone-IRF pathways are suggested to mediate sex differences in cerebral ischemia. Epigenetic modification of stroke-related genes constitutes an important mechanism underlying the ischemic sexual dimorphism.

The melanocortin-3 receptor is a pharmacological target for the regulation of anorexia

2021 ◽  
Vol 13 (590) ◽  
pp. eabd6434
Author(s):  
Patrick Sweeney ◽  
Michelle N. Bedenbaugh ◽  
Jose Maldonado ◽  
Pauline Pan ◽  
Katelyn Fowler ◽  
...  
Keyword(s):  
Sexual Dimorphism ◽  
Feeding Behavior ◽  
Critical Role ◽  
Brain Regions ◽  
Sexually Dimorphic ◽  
Male And Female ◽  
Female Mice ◽  
Bidirectional Regulation ◽  
Fear And Anxiety ◽  
Agouti Related Protein

Ablation of hypothalamic AgRP (Agouti-related protein) neurons is known to lead to fatal anorexia, whereas their activation stimulates voracious feeding and suppresses other motivational states including fear and anxiety. Despite the critical role of AgRP neurons in bidirectionally controlling feeding, there are currently no therapeutics available specifically targeting this circuitry. The melanocortin-3 receptor (MC3R) is expressed in multiple brain regions and exhibits sexual dimorphism of expression in some of those regions in both mice and humans. MC3R deletion produced multiple forms of sexually dimorphic anorexia that resembled aspects of human anorexia nervosa. However, there was no sexual dimorphism in the expression of MC3R in AgRP neurons, 97% of which expressed MC3R. Chemogenetic manipulation of arcuate MC3R neurons and pharmacologic manipulation of MC3R each exerted potent bidirectional regulation over feeding behavior in male and female mice, whereas global ablation of MC3R-expressing cells produced fatal anorexia. Pharmacological effects of MC3R compounds on feeding were dependent on intact AgRP circuitry in the mice. Thus, the dominant effect of MC3R appears to be the regulation of the AgRP circuitry in both male and female mice, with sexually dimorphic sites playing specialized and subordinate roles in feeding behavior. Therefore, MC3R is a potential therapeutic target for disorders characterized by anorexia, as well as a potential target for weight loss therapeutics.

Sexual dimorphism in the antennae of terrestrial isopods: a result of male contests or scramble competition?

2000 ◽  
Vol 78 (11) ◽  
pp. 1987-1993 ◽  
Author(s):  
F Lefebvre ◽  
M Limousin ◽  
Y Caubet
Keyword(s):  
Sexual Dimorphism ◽  
Negative Correlation ◽  
Morphological Analysis ◽  
Scramble Competition ◽  
Behavioral Analysis ◽  
Sexually Dimorphic ◽  
Selection Pressures ◽  
Terrestrial Isopods ◽  
Male Contests

In Oniscidea (terrestrial crustaceans), males are known to have longer antennae than females. This sexual dimorphism may result from a variety of selection pressures. However, some species are well known for their highly aggressive males, which use their antennae as weapons. We tested the hypothesis that longer antennae in males have been selected for by means of antennal contests. Morphological analysis of the antennae and behavioral analysis of male dyads were performed in parallel on 7 species. We demonstrate significant sexual dimorphism of the antennae in 6 of the 7 species, and various forms of male aggressiveness depending on the species. Our hypothesis was rejected because we found a negative correlation between the use of the antennae in contests and the magnitude of sexual dimorphism. Furthermore, some species are sexually dimorphic but the males never compete using their antennae. We propose and argue that scramble competition to be the first to find receptive females could explain why males have longer chemoreceptive antennae.

scholarly journals Sexual dimorphism in a top predator ( Notophthalmus viridescens ) drives aquatic prey community assembly

2018 ◽  
Vol 285 (1890) ◽  
pp. 20181717 ◽  
Author(s):  
Denon Start ◽  
Stephen De Lisle
Keyword(s):  
Sexual Dimorphism ◽  
Sex Ratio ◽  
Intraspecific Variation ◽  
Structure And Function ◽  
Sexually Dimorphic ◽  
Ecological Communities ◽  
Top Predator ◽  
Aquatic Mesocosms ◽  
And Function ◽  
The Impact

Intraspecific variation can have important consequences for the structure and function of ecological communities, and serves to link community ecology to evolutionary processes. Differences between the sexes are an overwhelmingly common form of intraspecific variation, but its community-level consequences have never been experimentally investigated. Here, we manipulate the sex ratio of a sexually dimorphic predacious newt in aquatic mesocosms, then track their impact on prey communities. Female and male newts preferentially forage in the benthic and pelagic zones, respectively, causing corresponding reductions in prey abundances in those habitats. Sex ratio differences also explained a large proportion (33%) of differences in the composition of entire pond communities. Ultimately, we demonstrate the impact of known patterns of sexual dimorphism in a predator on its prey, uncovering overlooked links between evolutionary adaptation and the structure of contemporary communities. Given the extreme prevalence of sexual dimorphism, we argue that the independent evolution of the sexes will often have important consequences for ecological communities.

scholarly journals The added value of a visible channel to a geostationary thermal infrared instrument to monitor ozone for air quality

2014 ◽  
Vol 7 (2) ◽  
pp. 1645-1689
Author(s):  
E. Hache ◽  
J.-L. Attié ◽  
C. Tourneur ◽  
P. Ricaud ◽  
L. Coret ◽  
...  
Keyword(s):  
Air Quality ◽  
Transport Model ◽  
Statistical Tests ◽  
Surface Ozone ◽  
A Priori ◽  
Thermal Infrared ◽  
Added Value ◽  
Chemical Transport Model ◽  
Geo Satellite ◽  
Sky Conditions

Abstract. Ozone is a tropospheric pollutant and plays a key role in determining the air quality that affects human wellbeing. In this study, we compare the capability of two hypothetical grating spectrometers onboard a geostationary (GEO) satellite to sense ozone in the lowermost troposphere (surface and the 0–1 km column). We consider one week during the Northern Hemisphere summer simulated by a chemical transport model, and use the two GEO instrument configurations to measure ozone concentration (1) in the thermal infrared (GEO TIR) and (2) in the thermal infrared and the visible (GEO TIR+VIS). These configurations are compared against each other, and also against an ozone reference state and a priori ozone information. In a first approximation, we assume clear sky conditions neglecting the influence of aerosols and clouds. A number of statistical tests are used to assess the performance of the two GEO configurations. We consider land and sea pixels and whether differences between the two in the performance are significant. Results show that the GEO TIR+VIS configuration provides a better representation of the ozone field both for surface ozone and the 0–1 km ozone column during the daytime especially over land.

scholarly journals Performance, but not size, of hindleg weaponry is sexually dimorphic in the giant mesquite bug (Thasus neocalifornicus)

2020 ◽  
Author(s):  
Zackary A. Graham ◽  
Nicole Kaiser ◽  
Alexandre V. Palaoro
Keyword(s):  
Sexual Dimorphism ◽  
Muscle Mass ◽  
Sexually Dimorphic ◽  
Aggressive Interaction ◽  
Body Parts ◽  
Single Measure ◽  
Male And Female ◽  
Aggressive Interactions ◽  
Sexual Dimorphisms

ABSTRACTIn many species, males possess specialized weaponry that have evolved to confer a benefit during aggressive interactions. Because male weaponry is typically an exaggerated or extreme version of pre-existing body parts, females often possess reduced or weaponry. Although much research has investigated sexual dimorphism in the sizes of such weapons, other weapon components, such as weapon performance or alternative weapon forms can also explain the evolution of weapon sexual dimorphisms. Here, we investigated the allometry and variation of multiple weapon components of hindleg weaponry in the male and female giant mesquite bugs, Thasus necalifornicus. Despite theory predicating greater allocation in male weaponry, we found that females allocated more into the lengths of their hindlegs compared to males. Despite this allocation, males possess relatively wider hindlegs, which likely increase area of muscle mass. Indeed, the squeezing performance of male hindlegs was much greater than that of female hindlegs. Lastly, we also described the allometry and variation in a male weapon component, prominent tibial spines, which likely are used to damage competitors during aggressive interaction. Overall, our findings highlight the intricacies of weapon sexual dimorphism and demonstrate the importance of measuring multiple weapon components and not a single measure.

scholarly journals Ecology and morphology of the dwarf bromeliad boa Ungaliophis panamensis (Squamata, Boidae, Ungaliophiinae) in Costa Rica and Panama

2021 ◽  
Vol 16 (2) ◽  
pp. 317-331
Author(s):  
Todd R. Lewis ◽  
Rowland K. Griffin ◽  
Irune Maguregui Martin ◽  
Alex Figueroa ◽  
Julie M. Ray ◽  
...  
Keyword(s):  
Costa Rica ◽  
Natural History ◽  
Latent Variable ◽  
Major Axis ◽  
Small Sample ◽  
Morphological Data ◽  
Sexually Dimorphic ◽  
Ecological Information ◽  
Rural Buildings ◽  
Forested Areas

Ecological and morphological data on Ungaliophis panamensis is extremely limited as this species is rarely encountered. These knowledge gaps have been advanced in this study where data was analysed from a small sample of snakes collected in two tropical forested environments in Costa Rica and Panama. Standardised major axis testing and a Bayesian latent variable ordination revealed that the species is sexually dimorphic, closely associated with tree trunks in natural forested areas, and occasionally discovered in rural buildings. Although further investigation into its natural history is warranted, this study shows that even with just a few individuals it is possible to elucidate ecological information that is relevant to the conservation of snake species.

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