Pruemopterus

''Pruemopterus'' is a genus of eurypterid, an extinct group of aquatic arthropods. The type and only species of ''Pruemopterus'', ''P. salgadoi'', is known only from a single fossil specimen, discovered in deposits of Early Devonian age in Germany. The generic name is derived from the Prüm river and the surrounding Prüm valley, which contains the finding place of the fossil, and the Greek πτερόν (pteron, "wing"), referring to the eurypterid swimming paddles, and the species name honors the Brazilian photographer and photojournalist Sebastião Salgado.

''Pruemopterus'' was a very small adelophthalmid eurypterid, with the type and only known specimen only measuring about 2.5 centimeters (0.98 in) in length. Although superficially similar to the related genus ''Parahughmilleria'', ''Pruemopterus'' can be distinguished from other adelophthalmids by several features, most notably its wide and vaguely rectangular carapace (head plate) and its rounded, rather than elongated, eyes. ''Pruemopterus'' lived alongside other Early Devonian animals, including several other eurypterid genera, in a shallow brackish to fresh water environment.

Description

''Pruemopterus'' was a very small adelophthalmid eurypterid, only measuring about 2.5 centimeters (0.98 in) in length. The carapace (head plate) of ''Pruemopterus'' was vaguely rectangular in shape, and was about 3.8 millimeters (0.15 in) long and 7.5 millimeters (0.3 in) wide. The compound eyes of ''Pruemopterus'' were round and placed in an anterior centrimesial (forward-central) position. Along the seventh to twelfth segments of the opisthosoma ( posterior body), ''Pruemopterus'' had strong lateral epimera (spines along the edges). The posterior body of ''Pruemopterus'' was relatively wide, with the pretelson (the penultimate body segment) being about half as long as it was wide. The telson (the last body segment) itself was lanceolate (lance-shaped) and robust. As in other adelophthalmids, the walking legs of ''Pruemopterus'' were spiniferous (having spines). Though they are only preserved fragmentarily, the amount of spinosity (how spiniferous the legs were) appears to have been similar to the related ''Adelophthalmus''.

''Pruemopterus'' differs from other adelophthalmid eurypterids mainly in features of its carapace and its eyes. The short and rectangular carapace of ''Pruemopterus'', and its eyes being rounded rather than elongated, easily distinguishes the genus from the Adelophthalmid genera ''Eysyslopterus'', ''Pittsfordipterus'', ''Bassipterus'' and ''Nanahughmilleria'' and ''Adelophthalmus''. The same also applies to the genus ''Parahughmilleria'', which co-occurred with ''Pruemopterus'', although the species ''Parahughmilleria hefteri'' (possibly a younger growth stage of the species ''Parahughmilleria major'') is superficially similar to ''Pruemopterus'' in its streamlined body shape and the lateral epimera along the same segments of the opisthosoma. ''Pruemopterus'' can be distinguished from ''Parahughmilleria hefteri'' by several features, including its more centrally positioned and rounder eyes, its wider carapace, the epimera being much more prominent and the telson being broader and more robust. Another obvious difference between ''Pruemopterus'' and ''Parahughmilleria'' is that the opisthosomal segments of ''Pruemopterus'' are more or less constant in length, whereas they increase in length posteriorly in ''Parahughmilleria''. The genus '' Unionopterus'', probably an adelophthalmid, is fragmentarily known, which complicates comparisons, but is clearly different from ''Pruemopterus'' in its smaller eyes and the wider marginal rim of its carapace.

History of research

The only known specimen of ''Pruemopterus'' was discovered by the German paleontologist Markus J. Poschmann in the 1980s in an old, now disused, sandstone quarry within the municipality of Hermespand in Weinsheim, Germany, about 800 meters north of the village of Hermespand itself, close to the village of Willwerath. The fossil deposits the specimen was uncovered in belong to the Klerf Formation and are of Early Devonian age, of the uppermost Lower Emsian epoch. Given that the fossil appears to preserve what eurypterid researchers refer to as a type A genital appendage, it appears to have been a female individual.

The specimen is today housed at the Generaldirektion Kulturelles Erbe, Direktion Landesarchäologie/Erdgeschichte in Koblenz, Germany, and is part of the State Collection of Natural History of Rhineland-Palatinate. Originally given the provisional designation 355-D by Poschmann, the specimen has the repository number PWL 2014/5186-LS a,b (a being the part and b being the counterpart of the compression fossil). The fossil was not formally described by Poschmann until 2020, when he determined that the combination of traits displayed suggested that it was an adelophthalmid eurypterid similar to ''Parahughmilleria'', known from the same deposits, but differing in features of its carapace, opisthosoma and telson. Poschmann thus named the new genus and species ''Pruemopterus salgadoi'' to accommodate the specimen.

The generic name ''Pruemopterus'' is derived from the Prüm river and the surrounding Prüm valley, wherein Hermespand and Willwerath are located, and the suffix '-''opterus''', derived from the Greek πτερόν (pteron, "wing"), often used in naming eurypterids due to the broad, wing-like swimming appendages of the eurypterine suborder. The species name ''salgadoi'' honors the Brazilian photographer and photojournalist Sebastião Salgado.

Classification

Poschmann referred ''Pruemopterus'' to the eurypterid family Adelophthalmidae, the only family within the superfamily Adelophthalmoidea. In particular, Poschmann noted that morphological comparisons with other adelophthalmid genera suggest that ''Pruemopterus'' was most closely related to ''Parahughmilleria''.

Poschmann also noted in his description of the type specimen that there were also close similarities to the Hughmilleriidae in the Pterygotioidea superfamily, though ''Pruemopterus'' differed from the genera in that family in having prominent lateral epimera on its opisthosomal segments (a feature for the most part missing among the hughmilleriids) and its eyes not being placed on the margin of the carapace.

Paleoecology

The deposits in which the ''Pruemopterus'' fossil was discovered are part of the so-called "Fossil-Lagerstätte Willwerath", a "classic" Early Devonian fossil locality that has yielded numerous early land plants, arthropods and vertebrates. Among the chelicerates, to which the eurypterids belong, the Early Devonian deposits have yielded both arachnids and early xiphosurans (genus ''Willwerathia''). Eurypterids are especially diverse in these deposits, accounting for five genera in addition to ''Pruemopterus'': ''Jaekelopterus'', ''Rhenopterus'', ''Erieopterus'', ''Adelophthalmus'' and ''Parahughmilleria''. ''Pruemopterus'' appears to have lived in non-marine aquatic environments. The Early Devonian eurypterid-yielding fossil sites in the Rhineland have been interpreted as having been part of a shallow aquatic environment with brackish to fresh water.

See also

* List of eurypterid genera
* Timeline of eurypterid research

References

{{Eurypterida

Devonian eurypterids
Eurypterids of Europe
Fossil taxa described in 2020
Adelophthalmoidea