The phylogenetic significance of the morphology of the syrinx, hyoid and larynx, of the southern cassowary, Casuarius casuarius (Aves, Palaeognathae)

Microstructural and crystallographic evolution of palaeognath (Aves) eggshells

The avian palaeognath phylogeny has been recently revised significantly due to the advancement of genome-wide comparative analyses and provides the opportunity to trace the evolution of the microstructure and crystallography of modern dinosaur eggshells. Here, eggshells of all major clades of Palaeognathae (including extinct taxa) and selected eggshells of Neognathae and non-avian dinosaurs are analysed with electron backscatter diffraction. Our results show the detailed microstructures and crystallographies of (previously) loosely categorized ostrich-, rhea-, and tinamou-style morphotypes of palaeognath eggshells. All rhea-style eggshell appears homologous, while respective ostrich-style and tinamou-style morphotypes are best interpreted as homoplastic morphologies (independently acquired). Ancestral state reconstruction and parsimony analysis additionally show that rhea-style eggshell represents the ancestral state of palaeognath eggshells both in microstructure and crystallography. The ornithological and palaeontological implications of the current study are not only helpful for the understanding of evolution of modern and extinct dinosaur eggshells, but also aid other disciplines where palaeognath eggshells provide useful archive for comparative contrasts (e.g. palaeoenvironmental reconstructions, geochronology, and zooarchaeology).

An investigation of syrinx morphometry and sound frequency association during the chirping period in lovebirds ( Agapornis fischeri)

Background: In the issue of biodiversity, the domestication of birds as pets and trade animals requires special attention as a conservation effort. Lovebirds ( Agapornis fischeri) are popular birds worldwide, due to their varied ornamentation and melodic chirping sound. Syrinx structure is suspected to be the main source of sound production during the chirping period. This study aimed to investigate syrinx morphometry and its correlation with sound frequency produced in lovebirds. Methods: A total of 24 lovebirds of different ages and gender were investigated. Polymerase chain reaction method was performed to determine lovebird gender, meanwhile bird age was identified based on post-hatch recordings at the breeding farm. Thus, we enrolled male (n=12) and female (n=12) lovebirds aged 2 (n=4), 3 (n=4), and 4 (n=4) months in the investigation group, respectively. Fast Fourier Transform (FFT) was performed to evaluate sound frequency during chirping period. Then, syrinx morphometry was identified using a topographic approach and methylene blue staining. Each variable was evaluated with Image J software and vernier caliper. Results: Based on a topographical approach, we reported the general cartilage structure of the tracheosyringeal, bronchosyringeal, paired protrusions, tracheolateral muscles, sternotracheal muscles, and syringeal muscles in lovebird syrinx. In particular, the tympaniform membranes lateral lead a crucial role in modulating the frequency of male lovebirds more significantly (p=0,009) compared to female. On the other hand, the tympaniform membranes lateral dexter (p=0,02) and sinister (p=0,05) in females showed wider compared to male. We also reported a negative correlation between sound frequency compared to tympaniform membranes lateral dexter (y = -913,56x + 6770,8) and sinister (y = -706,16x + 5736). Conclusions: It can be concluded that the tympaniform membranes lateral produced the lovebirds' primary sound. The sound frequency of male lovebirds was higher compared to female, however negatively correlated with the area of tympaniform membranes lateral.

The Length Polymorphism of the 9th Intron in the Avian CHD1 Gene Allows Sex Determination in Some Species of Palaeognathae

In palaeognathous birds, several PCR-based methods and a range of genes and unknown genomic regions have been studied for the determination of sex. Many of these methods have proven to be unreliable, complex, expensive, and time-consuming. Even the most widely used PCR markers for sex typing in birds, the selected introns of the highly conserved CHD1 gene (primers P2/P8, 1237L/1272H, and 2550F/2718R), have rarely been effective in palaeognathous birds. In this study we used eight species of Palaeognathae to test three PCR markers: CHD1i9 (CHD1 gene intron 9) and NIPBLi16 (NIPBL gene intron 16) that performed properly as Psittaciformes sex differentiation markers, but have not yet been tested in Palaeognathae, as well as the CHD1iA intron (CHD1 gene intron 16), which so far has not been used effectively to sex palaeognathous birds. The results of our research indicate that the CHD1i9 marker effectively differentiates sex in four of the eight species we studied. In Rhea americana, Eudromia elegans, and Tinamus solitarius, the electrophoretic patterns of the amplicons obtained clearly indicate the sex of tested individuals, whereas in Crypturellus tataupa, sexing is possible based on poorly visible female specific bands. Additionally, we present and discuss the results of our in silico investigation on the applicability of CHD1i9 to sex other Palaeognathae that were not tested in this study.

Redescription of the skull of the Australian flatback sea turtle, Natator depressus, provides new morphological evidence for phylogenetic relationships among sea turtles (Chelonioidea)

Chelonioidea (sea turtles) are a group where available morphological evidence for crown-group relationships are incongruent with those established using molecular data. However, morphological surveys of crown-group taxa tend to focus on a recurring subset of the extant species. The Australian flatback sea turtle, Natator depressus, is often excluded from comparisons and it is the most poorly known of the seven extant species of Chelonioidea. Previous descriptions of its skull morphology are limited and conflict. Here we describe three skulls of adult N. depressus and re-examine the phylogenetic relationships according to morphological character data. Using X-ray micro Computed Tomography we describe internal structures of the braincase and identify new phylogenetically informative characters not previously reported. Phylogenetic analysis using a Bayesian approach strongly supports a sister-group relationship between Chelonia mydas and N. depressus, a topology that was not supported by previous analyses of morphological data but one that matches the topology supported by analysis of molecular data. Our results highlight the general need to sample the morphological anatomy of crown-group taxa more thoroughly before concluding that morphological and molecular evidence are incongruous.