Central nervous system of a 310-m.y.-old horseshoe crab: Expanding the taphonomic window for nervous system preservation

Abstract

The central nervous system (CNS) presents unique insight into the behaviors and ecology of extant and extinct animal groups. However, neurological tissues are delicate and prone to rapid decay, and thus their occurrence as fossils is mostly confined to Cambrian Burgess Shale–type deposits and Cenozoic amber inclusions. We describe an exceptionally preserved CNS in the horseshoe crab Euproops danae from the late Carboniferous (Moscovian) Mazon Creek Konservat-Lagerstätte in Illinois, USA. The E. danae CNS demonstrates that the general prosomal synganglion organization has remained essentially unchanged in horseshoe crabs for >300 m.y., despite substantial morphological and ecological diversification in that time. Furthermore, it reveals that the euarthropod CNS can be preserved by molding in siderite and suggests that further examples may be present in the Mazon Creek fauna. This discovery fills a significant temporal gap in the fossil record of euarthropod CNSs and expands the taphonomic scope for preservation of detailed paleoneuroanatomical data in the Paleozoic to siderite concretion Lagerstätten of marginal marine deposits.

An earliest Triassic age forTasmaniolimulusand comments on synchrotron tomography of Gondwanan horseshoe crabs

“…Muscle traces have also been described from specimens of Euproops danae from the Upper Pennsylvanian (Virgilian) Lawrence Formation, Kansas ( Feldman et al, 1993 ; Babcock & Merriam, 2000 ; Bicknell et al, 2022b ). Further examination of the Lawrence Formation specimens would determine if the muscles exhibit moldic preservation—as is common for Mazon Creek fossils ( Clements, Purnell & Gabbott, 2019 ; Bicknell et al, 2021c )—or if there are additional, unexpressed anatomical features. The collection of novel soft anatomy from these and other fossil xiphosurids are vitally important in presenting and revising hypotheses regarding homology with extant xiphosurids ( sensu Briggs et al, 2005 ; Bicknell et al, 2022b ) and resolving conflicts between phylogenetic hypotheses ( e.g.…”

Peer Review #2 of "An earliest Triassic age for Tasmaniolimulus and comments on synchrotron tomography of Gondwanan horseshoe crabs (v0.2)"

“…Muscle traces have also been described from specimens of Euproops danae from the Upper Pennsylvanian (Virgilian) Lawrence Formation, Kansas (Feldman et al, 1993;Babcock & Merriam, 2000;Bicknell et al, 2022b). Further examination of the Lawrence Formation specimens would determine if the muscles exhibit moldic preservation-as is common for Mazon Creek fossils (Clements et al, 2019;Bicknell et al, 2021e)-or if there are additional, unexpressed anatomical features. The collection of novel soft anatomy from these and other fossil xiphosurids are vitally important in presenting and revising hypotheses regarding homology with extant xiphosurids (sensu Briggs et al, 2005;Bicknell et al, 2022b) and resolving conflicts between phylogenetic hypotheses (e.g., Ballesteros & Sharma, 2019;Lamsdell, 2020).…”

Interpreting fossilized nervous tissues

“…In the past decade, there has been a surge of studies presenting evidence of fossilized nervous tissues, mainly in fossil arthropods from Cambrian Konservat‐Lagerstätten, [ 1–10 ] but also, more rarely, from more recent deposits. [ 11 ] The question of whether such labile tissues—that is, prone to rapid decay—as ganglia and nerves can be preserved in settings of BST deposits has been discussed at length before. [ 12–14 ] The possibility of direct fossilization of nervous tissues (as opposed to, e.g., skull endocasts [ 15 ] ) rests on three key observations: (1) the experimental demonstration that nervous tissues in invertebrates can be persistent to decay, all other conditions being equal, [ 14 ] (2) the demonstration that the timing of decay observed under controlled experimentation does not correspond to the range of preservation seen in fossils, [ 12 ] particularly in BST deposits, [ 16 ] and (3) the well‐established presence in these fossils of other labile tissues, such as muscles, digestive tracts, and even eggs.…”