Fosiliferní uloženiny chadronského souvrství z oblasti Badlands v jižní Dakotě obsahují velmi diverzifikované společenství obratlovců. Podstatnou část z nich představují savčí pozůstatky, i když časté jsou i nálezy krokodýlů, želv a ještěrů. Obrovští lichokopytníci brontotéria, náležející mezi nejpůsobivější tvory té doby, tvořili spolu s vyhynulými sudokopytníky oreodonty dominantní komponentu tohoto svrchnoeocenního terestrického ekosystému. Kromě nich zahrnovala chadronská fauna ještě celou řadu dalších skupin licho- a sudokopytníků, například bezrohé nosorožce hyrakodonty a amynodonty, malé tříprsté koně, tapíry, entelodonty, antrakotéria, velbloudy, pekari a leptomerycidy. Početní byli i představitelé dvou řádů masožravých savců, kreodontů a šelem, zastoupení hyenodonty, nimravidy, psovitými a amfikýonidy. Nacházejí se zde i pozůstatky malých savců, především hlodavců, hmyzožravců a vačnatců. Pozoruhodný relikt představují multituberkuláti, jejichž největší rozvoj spadá do období druhohor. Výzkum této lokality tak nabízí jedinečnou příležitost k získání cenných poznatků, týkajících se nejen evoluce jednotlivých čeledí a řádů, ale rovněž i trendů změn životního prostředí v minulosti., The fossiliferous layers called Chadron formation of Badlands area in South Dakota contain a highly diverse assemblage of vertebrates. Numerous species of mammals represent a substantial part of revealed findings. The research of these ancient fossils offers a unique opportunity to obtain valuable information on the evolution of individual orders and families, and also about environmental changes in the past., and Stanislav Knor.
Specific transcription factors participate in the decision making process that controls cell fate and differentiation. They function in the environment of chromatin and directly affect its structure and activity. This influence is especially apparent during the development regulation of gametes and in the course of the development of an early embryo. This review focuses on the role that Snf2h (Smarca 5) and Brg1 (Smarca 4), two factors belonging to the SWI/SNF2 family, play in the establishment of chromatin structure in germinal and early embryonic development.
Sycophila pistacina (Rondani), which was previously synonymized with Sycophila biguttata (Swederus), is revalidated. Morphological, morphometric and molecular data confirm its status as a separate species. Diagnostic characters are provided for distinguishing it from S. biguttata. The nomenclature of the S. biguttata complex is updated.
We examined the song sharing and variation pattern of 44 Anna’s hummingbird males at syllable level in San Francisco, California. Full songs of Anna’s hummingbird were composed of repeated blocks of phrases. Each male sang from three to six syllable types and syllable repertoire size averaged 5.1. A total of 38 syllable types were identified in songs of the population examined, which can be classified into five basic syllable categories. Each syllable category exhibited different variability among individuals. We quantified the variation of each category and found the variability was highest in the first phrase of song. Using Jaccard’s similarity coefficient, we found the syllable sharing among birds was significantly greater within one sample site than between sites. Using Mantel tests, we demonstrated that syllable sharing among birds tended to decline with the increase of inter-individual geographic distance. A microgeographic song variation pattern that nearest neighbours tend to sing more similar songs than non-neighbours was supported in these analyses. However, hierarchical cluster analysis suggested not all individuals singing the most similar songs were nearest neighbors. It might be due to possible postbreeding immigration and song learning pattern that syllable is a unit of learning in this species.