The scleritome of Eccentrotheca from the Lower Cambrian of South Australia: Lophophorate affinities and implications for tommotiid phylogeny

Chronology of early Cambrian biomineralization

“…There is no unambiguous evidence of the existence of bilaterian superphyla in the Precambrian (Budd, 2008;Budd & Jensen, 2000, 2003, although some bilaterally symmetrical forms from the late Ediacaran, younger than 555 Ma, are interpreted as their representatives (e.g. Fedonkin & Waggoner, 1997).…”

“…These fossils have been interpreted as sclerites of larger scleritomes of problematic animals (Bengtson, 1970(Bengtson, , 2004Holmer et al 2008;Skovsted et al 2008Skovsted et al , 2009b. The taxonomy of tommotiids was discussed by Landing (1984Landing ( , 1995, Bengtson (1986), Laurie (1986), Bengtson et al (1990), Conway Morris & Chen (1990), Esakova & Zhegallo (1996) and Skovsted et al (2009a).…”

“…Based on the organophosphatic shell composition and morphological similarities, tommotiids have been regarded as closely related to brachiopods (Williams & Holmer, 2002). Recent discoveries of articulated tommotiids show distinct affinities to lophophorates, including a sessile habit and brachiopod-like shells within the scleritome (Skovsted et al 2008(Skovsted et al , 2009bHolmer et al 2008).…”

Setatella significans, a new name for mickwitziid stem group brachiopods from the lower Cambrian of Greenland and Labrador

“…Subsequently, evidence for shell penetrating setae has been found in a wide range of brachiopods from Cambrian and Ordovician strata (Balthasar 2004;Holmer & Caron 2006;Holmer et al 2008a;Jin et al 2008;Popov et al 2009) and the structure of recently discovered articulated tommotiid scleritomes has further strengthened the tommotiid-brachiopod link (Skovsted et al 2008(Skovsted et al , 2009aHolmer et al 2008b;). The original specimens from North-East Greenland were referred to the genus Mickwitzia Schmidt, 1888 by Holmer et al (2002) and were considered close to Mickwitzia occidens Walcott, 1908 from the Lower Cambrian of Nevada by Skovsted & Holmer (2003).…”

Depth related brachiopod faunas from the lower Cambrian Forteau Formation of southern Labrador and western Newfoundland, Canada

“…The first representatives appear in the Tommotian Stage of Siberia and Mongolia (Terrenuvian Series, Unnamed Stage 2; Skovsted et al, 2014bSkovsted et al, , 2015 and the brachiopod stem group (i.e. tommotiids; Skovsted et al, 2008Skovsted et al, , 2009Skovsted et al, , 2011Skovsted et al, , 2014aLarsson et al, 2014) is known from even older strata of the Fortunian Stage (Maloof et al, 2010;Kouchinsky et al, 2012). Brachiopods diversified rapidly during the early Cambrian and most of the main Palaeozoic lineages (Class) had appeared by the middle Cambrian (Cambrian Series 3) by which time brachiopods were well represented in most benthic communities worldwide (Ushatinskaya, 2001).…”