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Gigantism among Late Jurassic limulids: New ichnological evidence from the Causses Basin (Lozère, France) and comments on body-size evolution among horseshoe crabs

2014; Elsevier BV; Volume: 47; Issue: 4 Linguagem: Inglês

10.1016/j.geobios.2014.06.005

1777-5728

Jean‐David Moreau, Emmanuel Fara, Georges Gand, Gérard Lafaurie, Louis Baret,

Gait Recognition and Analysis

An abundant ichnological material composed of xiphosuran trackways and isolated traces was discovered in Upper Jurassic limestones from the Causses Basin (Causse Méjean, Lozère, France).The morphology of the imprints supports their identification as Kouphichnium isp.In contrast to the most frequent case, the trackways are composed of omnipresent pusher imprints sometime associated with leg traces, but with no telson mark.We argue that this pattern reflects actual surface traces rather than an incomplete set of undertracks.The size distribution of the sampled ichnites is broadly bimodal.This is best explained by sexual dimorphism, a phenomenon frequently observed in modern xiphosurans.Analysis of the trace fossils further suggests that several growth stages are recorded and that the horseshoe crabs were walking in a protected and flat environment like a lagoon.This area,