Probable cause of the cat-gap

The history of carnivorous mammals is characterized by a series of rise-and-fall patterns of diversification in which declining clades are replaced by phylogenetically distinct but functionally similar clades. Over the past 50 million years, successive clades of small and large carnivorous mammals diversified and then declined to extinction. In most instances, the cause of the decline was energetic constraints and pervasive selection for larger size (Cope's rule) that lead to (hypercarnivory) dietary specialization. Hypercarnivory leads to increased vulnerability of extinction. The nimravids were large cats that occupied this ecomorphic niche in the ecosystem until 26 Ma. It is highly likely that their hypercarnivory led to their extinction in North America. After the extinction of the nimravids there were no other feliform or Felidae species until other felids arrived from Eurasia after crossing the Bering land bridge 18.5 million years ago. During this time there was great diversity among the other carnivorous mammals in North America – both hypocarnivory and hypercarnivory species – and other hypercarnivory species existed before, during, and after the cat gap. In biology, phylogenetics (pron.: /fa?l?d?n?t?ks/) is the study of evolutionary relationships among groups of organisms (e.g. species, populations), which are discovered through molecular sequencing data and morphological data matrices. The term phylogenetics derives from the Greek terms phyle () and phylon (?), denoting "tribe", "clan", "race"[1] and the adjectival form, genetikos (?), of the word genesis (?) "origin," "source," "bi th".[2] The result of phylogenetic studies is a hypothesis about the evolutionary history of taxonomic groups: their phylogeny.[3] Evolution is regarded as a branching process, whereby populations are altered over time and may split into separate branches, hybridize together, or terminate by extinction. This may be visualized in a phylogenetic tree, a hypothesis of the order in which evolutionary events are assumed to have occurred. Phylogenetic analyses have become essential in researching the evolutionary tree of life. The overall goal of National Science Foundation's Assembling the Tree of Life activity (AToL) is to resolve evolutionary relationships for large groups of organisms throughout the history of life, with the research often involving large teams working across institutions and disciplines. Investigators are typically supported for projects in data acquisition, analysis, algorithm development and dissemination in computational phylogenetics and phyloinformatics. For example, RedToL aims at reconstructing the Red Algal Tree of Life. Taxonomy, the classification, identification, and naming of organisms, is usually richly informed by phylogenetics, but remains methodologically and logically distinct.[4] The degree to which taxonomy depends on phylogenies differs between schools of taxonomy: numerical taxonomy ignored phylogeny altogether, trying to represent the similarity between organisms instead; phylogenetic systematics tries to reproduce phylogeny in its classification without loss of information; evolutionary taxonomy tries to find a compromise between them in order to represent stages of evolution.