Limulus polyphemus: Living Fossil in the Laboratory

Renwick, George

doi:10.2307/4442109

Cited by 2 publications

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“…Modern xiphosurans have been intensively studied for around 150 years, spurred on by their archaic appearance (Renwick 1968) and importance as both a biomedical and economic resource (Botton and Ropes 1987). While early questions regarding their position within the arthropod tree (Lankester 1881) and the number of extant species (Waterman 1958) are long since resolved, the application of molecular phylogenetic methods to the group has raised new uncertainty about the interrelationships of the Asian species (Shishikura et al 1982;Avise et al 1994;Xia 2000;Kamaruzzaman et al 2011;Obst et al 2012).…”

Section: Discussionmentioning

confidence: 99%

Tachypleus syriacus (Woodward)—a sexually dimorphic Cretaceous crown limulid reveals underestimated horseshoe crab divergence times

Lamsdell

McKenzie

2015

Org Divers Evol

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The fossil record represents an important test to molecular divergence estimates, with known occurrences representing minimum divergence times for sister taxa. As such, accurately placing fossils in phylogenies is integral to understanding the patterns and processes that shape the tree of life. The chelicerate order Xiphosura comprises classic archetypes of morphological stasis, with the earliest known Ordovician representatives exhibiting all key morphological characteristics of the group. Molecular studies on the four extant species consistently retrieve a basal split between Limulinae and Tachypleinae, but conflict regarding the relationships of the three Asian species. Molecular divergence estimates using either no or a single fossil calibration point infer a Cretaceous or Palaeogene origin for Limulidae and a Palaeogene or Neogene origin for Tachypleinae and Tachypleus. Here, we present male and female specimens of Tachypleus syriacus (='Mesolimulus' syriacus) from the Cretaceous of Lebanon, revealing an anterior scalloped carapace margin in males-a derived condition of sexual dimorphism shared with Tachypleus tridentatus. Morphological phylogenetic analysis of total group Limulidae retrieves a monophyletic Tachypleus with a minimum divergence time during the Cretaceous, while crown-group Tachypleinae and Limulidae are both present during the Triassic, showing that molecular clock analyses have significantly underestimated the divergence times for these taxa.

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Section: Discussionmentioning

confidence: 99%

Tachypleus syriacus (Woodward)—a sexually dimorphic Cretaceous crown limulid reveals underestimated horseshoe crab divergence times

Lamsdell

McKenzie

2015

Org Divers Evol

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“…While the higher-level taxonomy of Xiphosura was updated to accommodate the phylogenetic topology ( Lamsdell, 2016 ), no in-depth diagnoses of the higher taxa was attempted, and no diagnostic revision of genera was undertaken. Given that many paleobiological meta-analyses operate at the genus level ( Hendricks et al, 2014 ) and that Xiphosura is a clade of particular interest to evolutionary biologists ( Renwick, 1968 ; Barthel, 1974 ; Fisher, 1981 ; Fisher, 1984 ; Fisher, 1990 ; Mattei et al, 2010 ; Faurby et al, 2011 ; Haug et al, 2012 ; Kin & Błażejowski, 2014 ; Moreau et al, 2014 ; Göpel & Wirkner, 2015 ; Lamsdell, 2016 ; Lamsdell, 2020 ; Lamsdell, in press ; Periasamy, Ingole & Meena, 2017 ; Shingate et al, 2020 ), it is critical that the lower-level taxonomy of horseshoe crabs also be revised in line with their phylogenetic relationships.…”

Section: Introductionmentioning

confidence: 99%

The phylogeny and systematics of Xiphosura

Lamsdell

2020

PeerJ

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Xiphosurans are aquatic chelicerates with a fossil record extending into the Early Ordovician and known from a total of 88 described species, four of which are extant. Known for their apparent morphological conservatism, for which they have gained notoriety as supposed ‘living fossils’, recent analyses have demonstrated xiphosurans to have an ecologically diverse evolutionary history, with several groups moving into non-marine environments and developing morphologies markedly different from those of the modern species. The combination of their long evolutionary and complex ecological history along with their paradoxical patterns of morphological stasis in some clades and experimentation among others has resulted in Xiphosura being of particular interest for macroevolutionary study. Phylogenetic analyses have shown the current taxonomic framework for Xiphosura—set out in the Treatise of Invertebrate Paleontology in 1955—to be outdated and in need of revision, with several common genera such as Paleolimulus Dunbar, 1923 and Limulitella Størmer, 1952 acting as wastebasket taxa. Here, an expanded xiphosuran phylogeny is presented, comprising 58 xiphosuran species as part of a 158 taxon chelicerate matrix coded for 259 characters. Analysing the matrix under both Bayesian inference and parsimony optimisation criteria retrieves a concordant tree topology that forms the basis of a genus-level systematic revision of xiphosuran taxonomy. The genera Euproops Meek, 1867, Belinurus König, 1820, Paleolimulus, Limulitella, and Limulus are demonstrated to be non-monophyletic and the previously synonymized genera Koenigiella Raymond, 1944 and Prestwichianella Cockerell, 1905 are shown to be valid. In addition, nine new genera (Andersoniella gen. nov., Macrobelinurus gen. nov., and Parabelinurus gen. nov. in Belinurina; Norilimulus gen. nov. in Paleolimulidae; Batracholimulus gen. nov. and Boeotiaspis gen. nov. in Austrolimulidae; and Allolimulus gen. nov., Keuperlimulus gen. nov., and Volanalimulus gen. nov. in Limulidae) are erected to accommodate xiphosuran species not encompassed by existing genera. One new species, Volanalimulus madagascarensis gen. et sp. nov., is also described. Three putative xiphosuran genera—Elleria Raymond, 1944, Archeolimulus Chlupáč, 1963, and Drabovaspis Chlupáč, 1963—are determined to be non-xiphosuran arthropods and as such are removed from Xiphosura. The priority of Belinurus König, 1820 over Bellinurus Pictet, 1846 is also confirmed. This work is critical for facilitating the study of the xiphosuran fossil record and is the first step in resolving longstanding questions regarding the geographic distribution of the modern horseshoe crab species and whether they truly represent ‘living fossils’. Understanding the long evolutionary history of Xiphosura is vital for interpreting how the modern species may respond to environmental change and in guiding conservation efforts.

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Limulus polyphemus: Living Fossil in the Laboratory

Cited by 2 publications

References 2 publications

Tachypleus syriacus (Woodward)—a sexually dimorphic Cretaceous crown limulid reveals underestimated horseshoe crab divergence times

Tachypleus syriacus (Woodward)—a sexually dimorphic Cretaceous crown limulid reveals underestimated horseshoe crab divergence times

The phylogeny and systematics of Xiphosura

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