Halkieriids and wiwaxiids are cosmopolitan sclerite-bearing metazoans from the Lower and Middle Cambrian. Although they have similar scleritomes, their phylogenetic position is contested. A new scleritomous fossil from the Burgess Shale has the prominent anterior shell of the halkieriids but also bears wiwaxiid-like sclerites. This new fossil defines the monophyletic halwaxiids and indicates th...

The hyolith fauna of the middle Bystraya Formation (Cambrian Series 2) eastern Transbaikalia (Zabaykalsky Krai), Siberia, includes at least 17 described taxa distributed between orders Hyolithida and Orthothecida. Species Microcornus, Parkula, Conotheca, Neogloborilus Cupitheca are widely reported from Cambrian strata elsewhere. Triplicatella uslonica sp. nov. is known only Transbaikalia. Dauri...

Abstract. We introduce permutrees, a unified model for permutations, binary trees, Cambrian trees and binary sequences. On the combinatorial side, we study the rotation lattices on permutrees and their lattice homomorphisms, unifying the weak order, Tamari, Cambrian and boolean lattices and the classical maps between them. On the geometric side, we provide both the vertex and facet descriptions...