Project 1228: J. C. Lamsdell, S. C. McKenzie. 2015. Tachypleus syriacus (Woodward) - a sexually dimorphic Cretaceous crown limulid reveals underestimated horseshoe crab divergence times. Organisms Diversity & Evolution. 15:681–693.
Specimen: † Mesolimulus syriacus

Abstract

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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Article DOI: 10.​1007/​s13127-015-0229-3

Project DOI: 10.7934/P1228, http://dx.doi.org/10.7934/P1228
This project containsMatrices
  • 1 Media
  • 1 Matrix
  • 18 Taxa
  • 1 Specimen
  • 20 Characters
Total size of project's media files: 4 MB

Download Project SDD File
Total scored cells: 287
Total media associated with cells: 0
Total labels associated with cell media: 0
Characters
Total characters: 20
Total characters with associated media: 0
Total characters with media with labels: 0
Total character states: 40
Total character states with associated media: 0
Total character states with media with labels:0
Total unordered/ordered characters:20/0
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MorphoBank Project 1228


    Members

    member name taxa specimens media chars character
    media
    labels
    cell scorings
    (scored, NPA, "-")
    cell
    medialabels
    rules
    James Lamsdell
    Project Administrator
    Last logged in 12/03/15
    18112000287
    (287, 0, 0)
    000


    Taxonomic Overview for Matrix 'M2794' (18 Taxa)

    taxon unscored
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    scored
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    NPA
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    [1] † Paleolimulus signatus
    Last Modified in 07/22/14
    2181800001
    [2] Carcinoscorpius rotundicauda
    Last Modified in 07/22/14
    0202000001
    [3] † Crenatolimulus paluxyensis
    Last Modified in 07/22/14
    6141400001
    [4] † Limulitella bronni
    Last Modified in 07/22/14
    7131300001
    [5] † Limulitella vicensis
    Last Modified in 07/22/14
    8121200001
    [6] † Limulus coffini
    Last Modified in 07/22/14
    119900001
    [7] † Limulus decheni
    Last Modified in 07/22/14
    4161600001
    [8] Limulus polyphemus
    Last Modified in 07/22/14
    0202000001
    [9] † Limulus sp.
    Last Modified in 07/22/14
    5151500001
    [10] † Mesolimulus crespelli
    Last Modified in 07/22/14
    6141400001
    [11] † Mesolimulus syriacus
    Last Modified in 07/22/14
    3171700001
    [12] † Mesolimulus walchi
    Last Modified in 07/22/14
    2181800001
    [13] † Tachypleus gadeai
    Last Modified in 07/22/14
    4161600001
    [14] Tachypleus gigas
    Last Modified in 07/22/14
    0202000001
    [15] Tachypleus tridentatus
    Last Modified in 07/22/14
    0202000001
    [16] † Tarracolimulus rieki
    Last Modified in 07/22/14
    6141400001
    [17] † Victalimulus mcqueeni
    Last Modified in 07/22/14
    3171700001
    [18] † Yunnanolimulus luopingensis
    Last Modified in 07/22/14
    6141400001


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    Media views2405Media search (2087 views); M336520 (318 views);
    Matrix views1234Matrix landing page (1095 views); Limulidae (139 views);
    Specimen list1090
    Bibliography465
    Taxon list3254




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