Revision of the Early Jurassic arthropod trackways Camurichnus and Hamipes

Abstract

RESUMEN Los icnogéneros Camurichnus y Hamipes ABSTRACTThe ichnogenera Camurichnus and Hamipes have been reevaluated based on examination of their type specimens, and their geographic and stratigraphic ranges determined based on a review of the literature. The characteristics used to distinguish Camurichnus (originally erected as Sagittarius) and its included ichnospecies alternans, have been observed in Bifurculapes laqueatus and therefore Camurichnus alternans is considered a junior subjective synonym of B. laqueatus herein. Hamipes is a distinct ichnogenus that can be differentiated from similar ichnotaxa by the number, shape, and arrangement of the tracks. Cretaceous trackways from Spain that were attributed to Hamipes belong to Bifurculapes. Additionally, the species H. molassicus is moved to the ichnogenus Conopsoides. Since the only other occurrence of Hamipes was the type specimen, the ichnogenus is again known only from the Early Jurassic of Massachusetts, U.S.A. The ichnotaxonomic reassignment, however, extends the geographic and stratigraphic range of Bifurculapes to the Cretaceous of Europe.

A trace fossil made by a walking crayfish or crayfish-like arthropod from the Lower Jurassic Moenave Formation of southwestern Utah, USA

“…Second, Bolliger & Gubler (1997) hypothesized that their novel, early Miocene ichnospecies Hamipes molassicus was made by a buoyed (presumably swimming) crayfish. Getty (2018) referred these specimens to Conopsoides ; later, Getty & Burnett (2019) suggested that at least some of the specimens may pertain to Acanthichnus , and they differ from SGDS 1290 for the same reasons outlined above for Acanthichnus . Third, De Gibert et al (2000) attributed Early Cretaceous, Spanish specimens that they assigned to Hamipes didactylus to crayfish.…”

“…Third, De Gibert et al (2000) attributed Early Cretaceous, Spanish specimens that they assigned to Hamipes didactylus to crayfish. Getty (2018) attributed these tracks to Bifurculapes and maintained a crustacean track maker for H. didactylus , but was not more specific. However, neither Bifurculapes nor Hamipes resemble experimentally generated crayfish traces ( Fairchild & Hasiotis, 2011 ), or any of the mortichnial decapod traces, and thus are unlikely to have been made by a crayfish-like decapod, at least while walking.…”

“…(J) Foersterichnus rossensis (traced from Pirrie, Feldmann & Buatois, 2004 ). (K) Hamipes didactylus (traced from Getty, 2018 ). (L) Laterigradus lusitanicus (traced from De Carvalho et al, 2016 ).…”

“…Hamipes tracks ( Fig. 4K ) consist of closely spaced, paired, elongate to crescentic impressions oriented parallel to the trackway axis; the outer tracks are longer than their accompanying inner tracks, and the tracks are staggered or alternately arranged ( Getty, 2018 ; Hitchcock, 1858 ). Track morphology readily differentiates Hamipes from SGDS 1290.…”

“…Kouphichnium , are also present. Ichnospecies of Bifurculapes have been variably attributed to insects, possibly beetles, and to crustaceans ( Getty, 2016 , 2018 ; Hitchcock, 1858 , 1865 ); ichnospecies of Diplichnites have been attributed to myriapods ( Briggs, Rolfe & Brannan, 1979 ; Davis, Minter & Braddy, 2007 ; Pollard, Selden & Watts, 2008 ; Shillito & Davies, 2018 ), notostracans ( Lucas et al, 2006a ; Minter et al, 2007 ), and other arthropods ( Melchor & Cardonatto, 2014 ; Minter et al, 2007 ); and ichnospecies of Kouphichnium have been attributed to limulids ( Caster, 1944 ; King, Stimson & Lucas, 2019 ; Lomax & Racay, 2012 ).…”