Chelicerata, Class, Merostomata, Order Xiphosura
Time: Late Jurassic, Kimmeridgian Stage (~ 150 million years
Site: Solnhoen Limestone Lagerstätte, Malm Zeta 2, Eichstatt,
crabs are members of Order
Xiphosura in Subphylum Chelicerata,
and thus related to the extinct Eurypterids, and more distantly
to spiders and scorpions. They in the latest Cambrian to the
earliest Ordovician, and remain extant today, apparent little
changed over geologic time.
This Jurassic fossil is from the famous
Solnhofen lithographic limestone deposits near Eichstatt, Germany. This 150 million year old lagerstätte is renkowned for exceptionally
well-preserved fossils, by far the most famous being the ancient
they have ostensibly changed little over some 485 million years,
extant horseshoe crabs are often considered by some to be so-called
living fossils. They were highly diverse during the Palaeozoic
Era, although extant genera number but three, with but five
species remaining. Horseshoe crabs possess a large shield covering
their cephalothorax, and a carapace that is hinged between the
cephalothorax and the abdomen.
A strong exoskeleton has three parts, the large semicircular
cephalothorax, the opisthosoma that is the posterior portion
body behind the cephalothorax, and a long tail spine (telson).
The trilobite-like morphology
is apparent, and some scientists consider Xiphosura to be the
closest living relative of trilobites.
see: Solnhofen Fossils