Rare fossil polychelid lobsters in turbiditic palaeoenvironments

Abstract

Polychelidan lobsters are one of the rare groups of decapod crustaceans which were first discovered as fossils long before being identified in extant deep-sea environments. As other decapods, their fossil record is highly incomplete, which complicates the reconstruction of their evolutionary history. Another problem hinders a better knowledge of the group: the familial assignments, which can be difficult in the absence of a complete revision of known fossil taxa. As a result, only three fossil Polychelidae have been identified to date, the oldest dating back to the Callovian (Middle Jurassic). In the present study, we consider two rarely studied species, Palaeopolycheles crymensis Levitski, 1974 from the Toarcian-Aalenian (Early-Middle Jurassic) of Crimea (Ukraine), and Eryon neocomiensis Woodward, 1881 from the Valanginian (Early Cretaceous) of the Outer Carpathians (Czech Republic). Our reinvestigations indicate they present several characters typical of Polychelidae, and are actually morphologically quite similar to extant species, notably in the structure of the anterior part of carapace and the small ocular incisions. Two new genera are erected to accommodate them: Tauricheles nov. gen., and Woodwardicheles nov. gen. These reinvestigations show that: (1) the evolutionary history of Polychelidae is much older; (2) Polychelidae have inhabited deep-water for a long time; (3) both species are probably autochthonous or parautochthonous to turbiditic palaeoenvironments; (4) Woodwardicheles neocomiensis nov. comb. is one of the rare benthic macrofossil of the Silesian Basin.

A new polychelidan lobster preserved with its eggs in a 165 Ma nodule

“…The establishment of the long-lived planktic larva (eryoneicus), probably during the Cretaceous 7 or after, likely offered the possibility to polychelidan lobsters to survive in the deep sea, while shallow water taxa went extinct 1 , possibly owing to the evolution of true crabs that likely competed for similar resources and habitats 23,24 . At the same time, the limited resources of this harsh environment may have been constraining brood size in polychelidan lobsters.…”

Proeryon, a geographically and stratigraphically widespread genus of polychelidan lobsters

“…Polychelidan lobsters (also referred to as Eryonoidea Haan, 1841) are decapod crustaceans characterized by their four to five pairs of clawed pereiopods. They are discovered in various fossil environments, from shallow waters, as in the Solnhofen or Monte Fallano plattenkalks (Garassino and Schweigert, 2006;Bravi et al, 2014) to deep-water environments (Audo et al, 2014c;Audo et al, 2018a). Fossil representatives have been first described in the early 19th century (Desmarest, 1817), and since then, numerous species have been described by various authors, with varying level of details and terminology, leading to numerous taxonomic imprecisions and the description of synonymous species (see synonymy list of Cycleryon propinquus in Garassino and Schweigert, 2006 as a good example).…”

Palaeoecology of Voulteryon parvulus (Eucrustacea, Polychelida) from the Middle Jurassic of La Voulte-sur-Rhône Fossil-Lagerstätte (France)

“…Nevertheless, the evolutionary history of polychelidans, their palaeobathymetry, and their visual systems are complex. Indeed, two distinct visual systems, apposition and reflective superposition, occur within polychelidans 5 , and while many species are reported from shallow waters, some of the earliest species inhabited deep waters 6,7 . To understand the evolutionary history of the group through time it is of utmost importance to examine the environment of each species and their phylogenetic relationships.…”