Palaeozoic Xiphosurans and Aglaspidids
16th January 2008

Many people are fascinated by these animals, from the horseshoe crabs of today to their ancient predecessors in the fossil record.

There have been a number of exciting recent discoveries, including the very modern looking Lunataspis from the Ordovician of Manitoba and the youngest synziphosurine, Anderella, from the Carboniferous Bear Gulch Limestone of Montana. Further revelations lie in store from the Ordovician of Morocco.

Here is a small gallery of images from the Palaeozoic of North America, Europe and North Africa.

<-- Index | Showing 1-16 of 16 pictures | Index -->

"Aglaspis", a 20 mm aglaspidid complete with limbs and antennae, Upper Cambrian, Weeks Formation, Millard County, Utah.
 Drawing of the 20 mm Weeks Formation aglaspidid. Notice how the prosoma in this individual is only a quarter of the animal length excluding telson whereas the Beckwithia has a cephalon which is more than a third of the animal's length excluding telson.
Drawing of the 20 mm Weeks Formation aglaspidid. Notice how the prosoma in this individual is only a quarter of the animal length excluding telson whereas the Beckwithia has a cephalon which is more than a third of the animal's length excluding telson.
 Beckwithia typa, 3 cm complete. Weeks Formation, Upper Cambrian, Millard County, Utah, USA.
Beckwithia typa, 3 cm complete. Weeks Formation, Upper Cambrian, Millard County, Utah, USA.
 45 mm xiphosuran. Lower Ordovician, near Zagora, Morocco. I think this guy may have been a male since the more robust front appendage could be interpreted as the first pedipalp (used for grasping the female in the modern Limulus). A beautifully chelate limb and a pushing leg are well seen in this specimen.
45 mm xiphosuran. Lower Ordovician, near Zagora, Morocco. I think this guy may have been a male since the more robust front appendage could be interpreted as the first pedipalp (used for grasping the female in the modern Limulus). A beautifully chelate limb and a pushing leg are well seen in this specimen.
Drawing of 45 mm xiphosuran.
Drawing of 45 mm xiphosuran.
 6 mm synziphosurine (similar to Bunodidae). Note presence of limbs beneath prosoma at top right. Lower Ordovician, near Zagora, Morocco.
6 mm synziphosurine (similar to Bunodidae). Note presence of limbs beneath prosoma at top right. Lower Ordovician, near Zagora, Morocco.
 Drawing of the small Moroccan arthropod. There didn't seem to be any more of a telson than this in the matrix. Notice the clear distinction between mesosoma (8 segments) and metasoma.
Drawing of the small Moroccan arthropod. There didn't seem to be any more of a telson than this in the matrix. Notice the clear distinction between mesosoma (8 segments) and metasoma.
 Limuloides limuloides, prosoma of a primitive horseshoe crab (synziphosuran). Church Hill, Leintwardine, Herefordshire, UK. The prosoma is encrusted by a bryozoan colony (see
Limuloides limuloides, prosoma of a primitive horseshoe crab (synziphosuran). Church Hill, Leintwardine, Herefordshire, UK. The prosoma is encrusted by a bryozoan colony (see "walking hotel" comment under the Euproops rotundatus).
A Victorian drawing of Limuloides limuloides by La Touche, 1884.
A Victorian drawing of Limuloides limuloides by La Touche, 1884.
 Paleolimulus longispinus, 60 mm, with well preserved chelate limbs in micrite. Filamentous algae, productid brachiopod and nematode worms on reverse. Taylor Formation, Bear Gulch, Fergus County, Montana, USA. A new synziphosurine (Anderella) has recently been described from this deposit (Moore et al. 2007).
Paleolimulus longispinus, 60 mm, with well preserved chelate limbs in micrite. Filamentous algae, productid brachiopod and nematode worms on reverse. Taylor Formation, Bear Gulch, Fergus County, Montana, USA. A new synziphosurine (Anderella) has recently been described from this deposit (Moore et al. 2007).
 Paleolimulus sp, 23 mm. Francis Creek Shale Member, Carbondale Formation, Westphalian D, Upper Carboniferous. Pit 11, near Essex, Kankakee Co., Illinois, USA.
Paleolimulus sp, 23 mm. Francis Creek Shale Member, Carbondale Formation, Westphalian D, Upper Carboniferous. Pit 11, near Essex, Kankakee Co., Illinois, USA.
 Euproops danae, 28 mm. Francis Creek Shale, Desmoinesian, Pennsylvanian, Upper Carboniferous. Mazon Creek, Illinois, USA.
Euproops danae, 28 mm. Francis Creek Shale, Desmoinesian, Pennsylvanian, Upper Carboniferous. Mazon Creek, Illinois, USA.
Euproops rotundatus. 40 mm wide, excellent xiphosuran. Westphalian A, Upper Carboniferous. Roof Shales above Wigan 4 Foot Coal Seam, Crock Hey Open Cast, Wigan, Lancashire, England. This individual carries many small Spirorbis worm tubes which reminds me of the
Euproops rotundatus. 40 mm wide, excellent xiphosuran. Westphalian A, Upper Carboniferous. Roof Shales above Wigan 4 Foot Coal Seam, Crock Hey Open Cast, Wigan, Lancashire, England. This individual carries many small Spirorbis worm tubes which reminds me of the "walking hotels" nickname for modern horseshoe crabs.
 Bellinurus trilobitoides. 23 mm complete specimen. Westphalian A, Upper Carboniferous. Roof Shales above Wigan 4 Foot Coal Seam, Crock Hey Open Cast, Lancashire, UK.
Bellinurus trilobitoides. 23 mm complete specimen. Westphalian A, Upper Carboniferous. Roof Shales above Wigan 4 Foot Coal Seam, Crock Hey Open Cast, Lancashire, UK.
 Bellinurus trilobitoides. 30 mm. Upper Carboniferous. Rochdale, Greater Manchester, England.
Bellinurus trilobitoides. 30 mm. Upper Carboniferous. Rochdale, Greater Manchester, England.
Liomesaspis laevis. 15 mm. Upper Carboniferous. Rochdale, Greater Manchester, England.
Liomesaspis laevis. 15 mm. Upper Carboniferous. Rochdale, Greater Manchester, England.
© 1998-2009 R.D.A.SMITH - All copyrights rest with the Author
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