The early history and phylogeny of the chelicerates

Gravitational Constraints on the Burial of Chengjiang Fossils

“…Lieberman (2008), a telson is a post−segmental terminal structure that lacks appendages. Dunlop and Selden (1997) considered a telson to be absent in Cheloniellon, but we identify the conical projection posterior to the ultimate leg pair and cerci (Stürmer and Bergström 1978: figs. 2, 3, 10, 11) as being most consistent with an identity as a telson.…”

“…Cladistic analysis including the best−known members of Megacheira, including leanchoiliids, has been conducted by Cotton and Braddy (2004) and Vannier et al (2009). The taxo− nomic sampling used by Cotton and Braddy (2004) included several megacheiran genera, representative chelicerates, a number of taxa representing groups that have been proposed as possible chelicerate relatives (e.g., Sidneyia, Aglaspis, Cheloniellon) in other analyses (Dunlop and Selden 1997;Hou and Bergström 1997), and members of the major lineages of the Artiopoda sensu Hou and Bergström (1997), i.e., trilo− bite−allied lamellipedians. Because artiopodan inter−relation− ships have remained quite stable through a series of phylogen− etic analyses (Edgecombe and Ramsköld 1999;Cotton and Braddy 2004;Hendricks and Lieberman 2008;Paterson et al 2010) and artiopodans are now often regarded as less closely related to Megacheira than is Chelicerata Cotton and Braddy 2004;Dunlop 2006), we have reduced the sampling of Artiopoda in the present analysis.…”

Complete Sequence of the 24-mer Hemocyanin of the TarantulaEurypelma californicum

“…To estimate the divergence times, the PAM matrix was imported into the Microsoft EXCEL 97 spreadsheet program (32). A linearized tree that corresponds to the phylogeny of the chelicerate hemocyanins was calculated on the basis that Merestomata and Arachnida separated about 450 MYA 1 (33). The confidence limits were estimated using the observed standard deviation of the protein distances.…”

“…These taxa split between 420 and 480 MYA (33). Under the assumption of an approximate divergence time of about 450 MYA, a mean amino acid substitution rate of 6.4 Ϯ 0.4 ϫ 10 Ϫ10 /site/year was inferred from the distance data set.…”

The arthropodOffacolus kingi(Chelicerata) from the Silurian of Herefordshire, England: computer based morphological reconstructions and phylogenetic affinities

“…Several phylogenetic and taxonomic schemes have been used for the chelicerates, and a number of cladistic studies have been published in recent years (Dunlop & Selden 1997;Wills et al 1998;Wheeler & Hayashi 1998). In order to analyse the position of Offacolus, we have made use of the database of Wills et al (1995Wills et al ( , 1998, which is based on a large number of characters and includes both fossil and extant taxa.…”