scholarly journals Effects of taphonomic deformation on geometric morphometric analysis of fossils: a study using the dicynodont Diictodon feliceps (Therapsida, Anomodontia)

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9925
Author(s):  
Christian F. Kammerer ◽  
Michol Deutsch ◽  
Jacqueline K. Lungmus ◽  
Kenneth D. Angielczyk
Keyword(s):  
Sexual Dimorphism ◽  
Phylogenetic Signal ◽  
Principal Component ◽  
Biological Variation ◽  
Biological Information ◽  
Geometric Morphometric ◽  
Uniform Shear ◽  
Geological Processes ◽  
Morphometric Analyses ◽  
True Position

Taphonomic deformation, the distortion of fossils as a result of geological processes, poses problems for the use of geometric morphometrics in addressing paleobiological questions. Signal from biological variation, such as ontogenetic trends and sexual dimorphism, may be lost if variation from deformation is too high. Here, we investigate the effects of taphonomic deformation on geometric morphometric analyses of the abundant, well known Permian therapsid Diictodon feliceps. Distorted Diictodon crania can be categorized into seven typical styles of deformation: lateral compression, dorsoventral compression, anteroposterior compression, “saddle-shape” deformation (localized collapse at cranial mid-length), anterodorsal shear, anteroventral shear, and right/left shear. In simulated morphometric datasets incorporating known “biological” signals and subjected to uniform shear, deformation was typically the main source of variance but accurate “biological” information could be recovered in most cases. However, in empirical datasets, not only was deformation the dominant source of variance, but little structure associated with allometry and sexual dimorphism was apparent, suggesting that the more varied deformation styles suffered by actual fossils overprint biological variation. In a principal component analysis of all anomodont therapsids, deformed Diictodon specimens exhibit significant dispersion around the “true” position of this taxon in morphospace based on undistorted specimens. The overall variance associated with deformation for Anomodontia as a whole is minor, and the major axes of variation in the study sample show a strong phylogenetic signal instead. Although extremely problematic for studying variation in fossil taxa at lower taxonomic levels, the cumulative effects of deformation in this study are shown to be random, and inclusion of deformed specimens in higher-level analyses of morphological disparity are warranted. Mean morphologies of distorted specimens are found to approximate the morphology of undistorted specimens, so we recommend use of species-level means in higher-level analyses when possible.

Phylogeny explains better than ecology or body size the variation of the first lower molar in didelphid marsupials

Mammalia ◽  
2017 ◽  
Vol 81 (2) ◽  
Author(s):  
Luíza Z. Magnus ◽  
Nilton Cáceres
Keyword(s):  
Body Size ◽  
Phylogenetic Relationship ◽  
Phylogenetic Signal ◽  
The Body ◽  
Male Body ◽  
Environmental Pressures ◽  
Geometric Morphometric ◽  
Morphometric Analyses ◽  
Lower Molar ◽  
Better Than

AbstractTribosphenic molars are considered great innovations in mammals and are related to several structures and variables that can explain adaptation. The aim of this study was to investigate the importance of body size and habitat relation, using a phylogenetic approach, in the first lower molar shape in didelphid marsupials. Geometric morphometric analyses of the lower molar’s shape were performed on 261 specimens, 130 females and 131 males, covering 14 genera and 37 species of the Didelphidae family. The molar conformation showed a larger talonid in relation to the trigonid in more arboreal genera, and narrower and longer molars in genera with a larger body size. Phylogeny was the variable with the highest explanation for both females and males (16.17% and 9.02%, respectively). The body size was significant in males, presenting an important influence on molar shape, while the body size in females was not significant when phylogenetic relationship was controlled for. In both sexes, habitat presents a strong effect of phylogeny, with no direct effect on molar shape. Didelphid molar shape is another result of its phylogenetic history and does not respond very much to environmental pressures. Male body size influences molar shape in didelphids, even in the presence of a strong phylogenetic signal.

Sexual dimorphism in the carapace shape and length of the freshwater palaemonid shrimp Macrobrachium potiuna (Müller, 1880) (Decapoda: Caridea: Palaemonidae): geometric and traditional morphometric approaches

2017 ◽  
Vol 67 (2) ◽  
pp. 93-103 ◽  
Author(s):  
Madson Silveira de Melo ◽  
Setuko Masunari
Keyword(s):  
Body Weight ◽  
Sexual Dimorphism ◽  
Behavioral Differences ◽  
Geometric Morphometric ◽  
Freshwater Shrimps ◽  
Morphometric Analyses ◽  
Males And Females ◽  
Morphological Differences ◽  
Three Rivers ◽  
Coastal Basin

Sexual dimorphism is characterized by morphological, physiological, or behavioral differences between males and females. The genus Macrobrachium is a diverse group of freshwater shrimps distributed throughout tropical and subtropical regions. They have a great intra- and interspecific morphological variation, with some species showing sexual dimorphism. We investigated the sexual dimorphism of the size and shape of the carapace and body weight of Macrobrachium potiuna (Müller, 1880) in three populations of the State of Paraná through traditional and geometric morphometric techniques. The populations were sampled from three rivers: the Pombas River, Coastal Basin, the Piraquara River, First Plateau, and the Guabiroba River, Second Plateau. Morphometric analyses indicated that male shrimps showed differences in carapace length and body weight: the higher the distance from the sea, the smaller and lighter the shrimps. Carapace shape also differed significantly between the sexes in all three populations, with males having a less robust carapace, but a more elongated rostrum than females. The morphological differences between the genders seem to reflect the reproductive roles of males and females in this environment.

scholarly journals Jurassic scorpionflies (Mecoptera) with swollen first metatarsal segments suggesting sexual dimorphism

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Yan-jie Zhang ◽  
Peter J. M. Shih ◽  
Jun-you Wang ◽  
Maria E. McNamara ◽  
Chungkun Shih ◽  
...  
Keyword(s):  
Sexual Dimorphism ◽  
Middle Jurassic ◽  
Sexually Dimorphic ◽  
Geometric Morphometric ◽  
First Metatarsal ◽  
Phylogenetic Studies ◽  
Morphometric Analyses ◽  
New Findings ◽  
Mating Opportunities ◽  
Species Specific

Abstract Background Sexual dimorphism is widespread in insects. The certain specialized structures may be used as weapons in male–male combats or as ornaments to enhance mating opportunities. Results We report striking swollen first tarsal segments in two families, four genera and six species of scorpionflies from the Middle Jurassic Yanliao Biota of Northeastern China. Swollen tarsal segments are restricted to male specimens and to hind leg tarsi. The geometric morphometric analyses reveal that the degree of swelling within the orthophlebiid species possessing swollen first metatarsal segments is species-specific, which can be used as a diagnostic character for taxonomic and phylogenetic studies. Conclusions The new findings indicate that swollen first metatarsal segments are relatively common in the family Orthophlebiidae during the Middle Jurassic. The tarsal swellings are considered to be sexually dimorphic, potentially associated with sexually display by males and/or camouflage of a “nuptial gift” in the mating process.

Body shape evolution of Chromis and Azurina species (Percifomes, Pomacentridae) of the eastern Pacific

2013 ◽  
Vol 63 (2) ◽  
pp. 217-232 ◽  
Author(s):  
Rosalía Aguilar-Medrano
Keyword(s):  
Body Shape ◽  
Phylogenetic Signal ◽  
Molecular Data ◽  
The Body ◽  
Eastern Pacific ◽  
Morphological Pattern ◽  
Geometric Morphometric ◽  
Morphometric Variation ◽  
Size And Shape ◽  
Morphometric Analyses

Chromis is a circumglobal tropical and temperate genus with over 84 species of damselfishes. Studies based in osteological and molecular data have cited the relationship between Azurina and Chromis in the eastern Pacific. The main objectives of the study are: (1) to characterize size and shape in all Chromis and Azurina species of the eastern Pacific, (2) explore the phylogenetic signal of external morphology, and (3) present a hypothesis of the diversification process of this group. According to the results, there is no significant relationship between size and shape. The variation in body shape among all species is related to the height of the trunk, position of the snout and eye, and length of the caudal peduncle. The main morphologic variation between Azurina and Chromis is the degree of elongation of the body. Both Azurina species are closely related to C. punctipinnis and C. atrilobata. The morphological pattern of Azurina integrated it into Chromis. The phylogenetic pattern found by geometric morphometric analyses presented a high similarity with previous results based on molecular data. Phylogeny recovered two main clades, slender-bodied and deep-bodied species. This pattern of morphometric variation is closely related to exploitation of two different reef environments.

Intersexual and intrasexual selection for neck musculature in men: Attractiveness, dominance, and actual fighting success

2021 ◽  
Author(s):  
Neil Robert Caton ◽  
David M. G. Lewis
Keyword(s):  
Sexual Dimorphism ◽  
Evolutionary Biology ◽  
Theoretical Work ◽  
Human Anatomy ◽  
Geometric Morphometric ◽  
World Region ◽  
Sexual Characteristics ◽  
Neck Strength ◽  
Neck Musculature ◽  
Secondary Sexual

Countless organisms are equipped with physiological armor that reduce damage from opponents. Because humans have sustained a long evolutionary history of hand-to-hand combat, selection would have been placed on morphological structures which reduce rotational acceleration to the head and increase the likelihood of victory. Grounded in over 60 years of sports performance theory and recent theoretical work in evolutionary biology, geometric morphometric analyses revealed that larger neck musculature in professional combatants (N = 715) was associated with greater real-world fighting success, after for adjusting for allometry (Study 1). Because sexual dimorphism emerges from selection on morphological structures that improve men’s fighting success, we then discovered that the human neck is the most sexually dimorphic feature of human anatomy when compared to 91 other anatomical features (N = 6,068; Study 2). This male-biased sexual dimorphism held after controlling for these 91 allometric measurements, and held across every world region (Africa, Asia, Europe, Oceania, and North, Central, and South America). Because human psychological systems consequently evolved to attend to men’s secondary sexual characteristics, we discovered that men (N = 564 stimuli) with larger neck musculature (Study 3: geometric morphometrics; Study 4: physiological neck strength; Study 5: photorealistic stimuli) are rated (N = 772 raters) as stronger, more masculine, and higher in fighting ability and short-term attractiveness, after accounting for allometry. Combined, our research introduced a new secondary sexual characteristic to the biological, anthropological, and psychological sciences: the human neck.

Nest temperature´s influence on morphology of Dermochelys coriacea hatchlings incubated in hatcheries in Oaxaca, Mexico

2021 ◽  
Author(s):  
Jesús García-Grajales ◽  
Juan Francisco Meraz ◽  
José Luis Arcos García ◽  
Eustacio Ramírez Méndez
Keyword(s):  
Incubation Temperature ◽  
Carapace Width ◽  
Principal Component ◽  
Dermochelys Coriacea ◽  
Egg Mass ◽  
Natural Environments ◽  
Data Logger ◽  
Geometric Morphometric ◽  
Low Weight ◽  
Incubation Temperatures

The influence of nest incubation temperatures on the carapace shape and morphological traits of Dermochelys coriacea (Vandelli 1761) hatchlings incubated in two hatcheries of Oaxaca, Mexico was evaluated. This study was carried out from October 2016 through May 2017. On each beach, there are community groups consisting of volunteers without association with universities, that protect and relocate the nests to increase hatching success. In each translocated nest, a data logger was placed in the centre of the egg mass. Hatchlings were collected as they emerged from each nest. The carapaces of the hatchlings were photographed and subjected to geometric morphometric analysis; later, hatchlings were weighed and their bodies were measured. The mean temperature of 12 nests in each hatchery were recorded, with no significant differences between hatcheries. The principal component analysis (PCA) revealed an overlapping of the carapace shape under different duration of temperature. Temperature had a significant influence on hatchling morphology. Higher mean incubation temperatures produced hatchlings with low weight, smaller appendage; narrower carapace width and shorter flippers length. Lower mean incubation temperatures produced hatchlings that had greater weight, greater appendage width, wider carapace width and longer flipper length. Results indicate that the D. coriacea hatchlings incubated in hatcheries demonstrate morphology that varies in relation to nest incubation temperature in a similar way to hatchlings produced in natural environments.

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