Two new Silurian species ofEurypterus(Chelicerata: Eurypterida) from Norway and Canada and the phylogeny of the genus

Abstract

SYNOPSIS A new species of Eurypterus from the Wenlock of Ringerike, Norway is described as E. hankeni sp. nov., based on fine pustular ornament on the carapace and opisthosoma, an enlarged distal podomere of the swimming leg and long angular epimera on the pretelson. Eurypterus species are reviewed: the oldest species, E. minor Laurie, 1898 from the Llandovery of the Pentland Hills in Scotland is redescribed and diagnosed as having eyes with large palpebral lobes, posterior second order opisthosomal differentiation, a coarse pustular ornament on both carapace and tergites and lacking the rows of raised scales found in other representatives of the genus. Material described previously and left in open nomenclature from the Late Ludlow of Somerset Island, Canada, is here named E. leopoldi sp. nov. It is relatively similar to E. pittsfordensis, but differs in the rhombiovate outline of the metastoma. An overview of morphological features carrying phylogenetic information in Eurypterus is provided. A phylogenetic analysis indicates that the earlier-used gen us, Baltoeurypterus Størmer, 1973, is not monophyletic and even use of the name for its type species only (and its sister taxon) will render Eurypterus paraphyletic, unless assigning most terminals to new genera. This is not considered appropriate and the genus name Eurypterus is here proposed for use for all species, including the three previously assigned to Baltoeurypterus.

Babes in the wood – a unique window into sea scorpion ontogeny

“…As the metastomal width decreases, so does that of the shoulders, which makes the notch angle more acute. A decrease in the relative width of the metastoma through ontogeny has also been noted in Stoermeropterus Lamsdell, 2011 and Moselopterus Størmer, 1974 [64] and, while it appears that the metastoma in Eurypterus retains its dimensions throughout ontogeny [80], the new evidence here from Jaekelopterus and Strobilopterus (below) suggests that the stasis in Eurypterus may be the exception rather than the rule.…”

“…The genal spines have been reduced to small posterolateral extensions of the carapace by stage β, with the first opisthosomal tergite shown to be fully laterally expressed behind the flattened carapace posterior margin. Similar posterolateral extensions are known from a number of other eurypterids, including Eurypterus [80], Drepanopterus [50], and Adelophthalmus [85], and it is possible that these, too, represent the vestigial remnants of genal spines. In the γ and δ instars the lateral portions of the second opisthosomal tergite expand anteriorly until they are overlapped by the carapace posterolateral extensions, the lateral portions of the first tergite apparently having been reduced.…”

A new Ordovician eurypterid (Arthropoda: Chelicerata) from southeast Turkey: Evidence for a cryptic Ordovician record of Eurypterida

“…The species was given a modern redescription by Tetlie (2006), who considered it to be a Eurypterus. Tetlie and Cuggy (2007), however, showed it to be phylogenetically distinct from Eurypterus but did not change the taxonomy due to uncertainty as to the exact position of the species.…”

“…While it shares many characteristics with Paraeurypterus anatoliensis, the difference in opisthosomal ornamentation clearly places P. anatoliensis phylogenetically closer to the Eurypteridae and the two species are therefore assigned to different genera. Tetlie (2006) listed NMS G.1897.32.110 as a second paratype, but this specimen number is actually associated with a specimen of Drepanopterus pentlandicus Laurie, 1892. The accession number of the Pentlandopterus second paratype is at present unknown.…”

New trace fossil evidence for eurypterid swimming behaviour

“…The biomechanical properties of the eurypterine swimming appendage were previously considered by three studies that each proposed a different predictive swimming model (Selden ; Plotnick ; Knight ; see Plotnick () for a review of earlier swimming hypotheses). Selden () performed the first in‐depth analysis of eurypterid swimming locomotion based on an exhaustive morphological examination of Eurypterus (= Baltoeurypterus ; Tetlie ). Selden () proposed that swimming eurypteroids (i.e.…”