New Early Devonian pteraspidids (Agnatha, Heterostraci) from east-central Nevada

Abstract

Three new species and genera of pteraspidids (Agnatha, Heterostraci), Tuberculaspis elyensis, Pirumaspis lancasteri, and Lamiaspis longiripa, are described from the Sevy Dolomite, east-central Nevada. They form part of a vertebrate fauna of typical Early Devonian aspect that indicates a correlation with previously described faunas from the Beartooth Butte and Water Canyon Formations of Utah and Wyoming, thus improving the known distribution and diversity of these faunas. Correlation with an accurately dated fauna in Death Valley, California, enables this fauna to be dated to the late Emsian (inversus–serotinus Zones).

Exploring phylogenetic relationships of Pteraspidiformes heterostracans (stem-gnathostomes) using continuous and discrete characters

“…Characters used in the phylogenetic analysis were obtained from direct observations of specimens, and species descriptions from published literature, and were adapted from the character lists from previous phylogenies (Ilyes & Elliott 1994 Goloboff et al 2006). Twenty-two continuous characters were used in this analysis in the form of ratio data to standardize for size variation (definitions are given in the character list; characters 66À87).…”

“…The first cladistic study to utilize global parsimony in a computerized analysis was undertaken by Ilyes & Elliott (1994). They focused on forms from the western USA (Fig.…”

“…This includes all genera outlined in Blieck 's (1984) extensive Pteraspidiformes review, along with newly described, or redescribed, taxa (Elliott 1983(Elliott , 1984Ilyes & Elliott 1994;Elliott & Ilyes 1996;Pern egre 2002;Pern egre & Goujet 2007;Voichyshyn 2011). Where possible, the type species of each genus has been used, unless that species is inadequately preserved, the material is missing, or another species from within the genus is substantially better known (see Supplemental Table 1).…”

“…Only a handful of heterostracan phylogenies have been constructed, most of which concentrate on the 'higher heterostracans' À that is, Cyathaspididae and Pteraspidiformes. Containing over 110 species and 47 genera (Dineley & Loeffler 1976;Elliott 1983Elliott , 1984Blieck 1984;Ilyes & Elliott 1994;Elliott & Ilyes 1996;Elliott et al 2000;Pern egre 2002Pern egre , 2006Novitskaya 2004;Pern egre & Goujet 2007; Pern egre & Elliott 2008;Voichyshyn 2011), Pteraspidiformes are the largest and most-studied group of heterostracans. They are relatively morphologically diverse, with a wide palaeogeographical range (Laurussia, Baltica, Kara and Avalonia) and a stratigraphical range from the Late Silurian to the Middle Devonian (Pr ıdoli-Givetian) (Blieck & Janvier 1999;Elliott et al 2000;Novitskaya 2007;Sansom 2009;Sansom et al 2015).…”

“…The latest occurring member of the group is Helaspis, found in the Yahatinda Formation of Givetian age in southern Alberta and British Columbia (Elliott et al 2000). Despite being the most heavily studied and numerous heterostracan group, there is yet to be a phylogeny containing all described genera: only subsets of the taxa have been subjected to phylogenetic analyses (Ilyes & Elliott 1994 & Elliott 2008).…”