On the appendicular anatomy of the xiphosurid Tachypleus syriacus and the evolution of fossil horseshoe crab appendages

A revision ofProlimulus woodwardiFritsch, 1899 with comparison to other highly paedomorphic belinurids

“…Belinurids represent the most successful Carboniferous and Permian xiphosurid group that explored freshwater niches ( Lamsdell, 2016 ; Shpinev & Vasilenko, 2018 ; Shpinev, 2018 ; Bicknell, Pates & Botton, 2019 ). The group also has an exceptional diversity and disparity, which is unusual when compared to the Late Mesozoic and Cenozoic forms ( Bicknell, 2019 ; Bicknell et al, 2019a ; Bicknell et al, in press-a ). Several attempts to colonize freshwater environments likely drove the Belinurina to evolve features that contrast the ‘typical’ xiphosurid morphology, and added to their extreme diversity and disparity ( Lamsdell, 2016 ; Lamsdell, 2020a ).…”

“…Such statements are mostly applicable to the late Mesozoic and Cenozoic forms ( Avise, Nelson & Sugita, 1994 ; Rudkin & Young, 2009 ; Kin & Błażejowski, 2014 ; Lamsdell & McKenzie, 2015 ; Błazejowski, Gieszcz & Tyborowski, 2016 ; Bicknell & Pates, 2019 ; Bicknell et al, 2019b ; Bicknell & Pates, 2019 ). Conversely, most Paleozoic and early Mesozoic forms record evolutionary exploration ( Bicknell, 2019 ; Bicknell, Amati & Hernández, 2019 ; Bicknell et al, 2019a ; Bicknell, Naugolnykh & Brougham, 2020 ; Bicknell et al, in press ; Bicknell, Hecker & Heyng , 2021 ; Bicknell & Pates, 2020 ). The evolutionary history of these earlier species illustrate morphological plasticity and exploration of different ecological niches ( Lamsdell, 2016 ; Lamsdell, 2020a ; Bicknell et al, 2019b ).…”

“…Furthermore, phylogenetic analyses illustrated that Belinurina was a monophyletic superfamily traditionally thought to contain Alanops (Racheboeuf, Vannier & Anderson, 2002), Anacontium (Raymond, 1944), Belinurus (Pictet, 1846), Euproops (Meek & Worthen, 1865), Liomesaspis (Raymond, 1944), and Prolimulus (Fritsch, 1899). Despite the interest in belinurids, an array of species described in the early 20th century require revision (see Lamsdell & McKenzie, 2015;Bicknell et al, 2019a: Bicknell, Lustri & Brougham, 2019Bicknell & Pates, 2020;Bicknell & Smith, in press for revisions of similar historical material). Expanding on the recent pulse in the revision of such historically important species, we reevaluate Prolimulus woodwardi Fritsch, 1899. We present a phylogenetic analysis including P. woodwardi and the morphologically comparable Stilpnocephalus pontebbanus Selden, Simonetto & Marsiglio, 2019, as well as a geometric morphometric analysis of species within Belinurina.…”

Xiphosurid from the Tournaisian (Carboniferous) of Scotland confirms deep origin of Limuloidea

“…The major limulid evolutionary events after A. bottoni are increased size, aligning with Cope’s Law 68 , and the maintenance of an overall morphology similar to A. bottoni . This suggests that evolutionary conservation within the group may have persisted over 350 million years 69 . Curiously, the key autapomorphy of A. bottoni —the pustulose cuticle ornament—was not retained, suggesting that it represents a derived trait in this taxon, or was lost in younger taxa.…”

First xiphosuran traceway in the middle Muschelkalk facies (Middle Triassic) of the Catalan Basin (NE Iberian Peninsula)

“…The xiphosurans show a maximum diversity during the Carboniferous and Triassic periods (Moore et al, 2007). Xiphosuran trace fossils provide additional information about the palaeobiology of these animals and their habitats (Gaillard, 2011;Fernández & Pazos, 2013;Mujal et al, 2018a;Bicknell et al, 2019;Shibata & Varricchio, 2020).…”