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In a cladogram, a point from which two or more new branches diverge, representing either of two cases:
a. A multiple speciation event in which two or more species diverge from the same ancestor. Also called hard polytomy.
b. A speciation event in which two or more species are presumed to descend from the same ancestor, but the order of speciation is unknown. Also called soft polytomy.

[poly- + -tomy (on the model of dichotomy).]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
References in periodicals archive ?
Phylogenetically, Oregonichthys is either sister to Tiaroga of the Gila and San Pedro Rivers of the American Southwest (based on mtDNA) or part of a polytomy (based on nuclear DNA) including Tiaroga, Rhinichthys, and numerous eastern genera (Simons and others 2003; Buffalino and Mayden 2010; Smith and others 2017).
mongolicus are grouped in two separate clusters, which stand in a polytomy with M.
None of the sequences from "Group A" matched a particular species and, due to weak nodal support, formed a polytomy with the Codiaceae and Bryopsidaceae (Fig.
The MP analysis returned a polytomy for these tribes within Cyperoideae.
Based on molecular data the polytomy of Ciconia may reflect a rapid process of speciation, because the trees of consensus have their branches collapsed (generating polytomies), when the trees from where they came (hybridisation DNA-DNA and analysis of cytochrome b), have the branches short (SLIKAS, 1997).
The maximum likelihood tree had a negative log likelihood of-2020.75868 and placed the samples in a polytomy of Anatrachyntis badia BOLD vouchers (Fig.
(2000) cast doubts about the relationship between Cryphaeaceae and Pterobryaceae by finding a polytomy involving Cryphaeaceae and Leucodontaceae.