''Pruemopterus'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

eurypterid Eurypterids, often informally called sea scorpions, are a group of extinct marine arthropods that form the Order (biology), order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period, 467.3 Myr, mil ...

, an extinct group of aquatic

arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

s. The

type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * ...

and only species of ''Pruemopterus'', ''P. salgadoi'', is known only from a single fossil specimen discovered in geological deposits of

Early Devonian The Early Devonian is the first of three Epoch (geology), epochs comprising the Devonian period, corresponding to the Lower Devonian Series (stratigraphy), series. It lasted from and began with the Lochkovian Stage , which was followed by the Pr ...

age in

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

. The name of the genus is derived from the

Prüm river Prüm () is a town in the Westeifel (Rhineland-Palatinate), Germany. Formerly a district capital, today it is the administrative seat of the ''Verbandsgemeinde'' ("collective municipality") Prüm (Verbandsgemeinde), Prüm. Geography Prüm lies o ...

and the surrounding Prüm valley, which contains the finding place of the fossil, and the

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

πτερόν (''pteron'', "wing"), referring to the eurypterid swimming paddles, and the species name honors the Brazilian photographer and photojournalist

Sebastião Salgado Sebastião Ribeiro Salgado Júnior (8 February 1944 – 23 May 2025) was a Brazilian social documentary photographer and photojournalist. He traveled in more than 120 countries for his photographic projects, which appeared in numerous press p ...

. ''Pruemopterus'' was a very small adelophthalmid eurypterid, with the only known specimen measuring about 2.5 centimeters (0.98 in) in length. Although superficially similar to the related genus ''

Parahughmilleria ''Parahughmilleria'' (meaning "near ''Hughmilleria''"Meaning opara-at ''www.dictionary.com''. Retrieved 17 July 2018.) is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of ''Parahughmilleria'' have been discovered in depo ...

'', ''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 Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...

fresh water Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salt (chemistry), salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include ...

environment.

Description

''Pruemopterus'' was a very small adelophthalmid

, only measuring about 2.5 centimeters (0.98 in) in length. The

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...

(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 A compound eye is a visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidia, which are tiny independent photoreception units that consist of a cornea, lens, and photoreceptor cells which distin ...

of ''Pruemopterus'' were round and placed in an

anterior Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

centrimesial (forward-central) position. Along the seventh to twelfth segments of the

opisthosoma The opisthosoma is the posterior part of the body in some arthropods, behind the prosoma ( cephalothorax). It is a distinctive feature of the subphylum Chelicerata (arachnids, horseshoe crabs and others). Although it is similar in most respects ...

( posterior body), ''Pruemopterus'' had strong lateral epimera ("extensions" along the edges). The posterior body of ''Pruemopterus'' was relatively wide, with the pretelson (the last body segment, before the tail) being about half as long as it was wide. The

telson The telson () is the hindmost division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment (biology), segment of the arthropod body, or an additional division that is not a true segm ...

("tail") 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 ''Adelophthalmus'' is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of ''Adelophthalmus'' have been discovered in deposits ranging in age from the Early Devonian to the Early Permian, which makes it the longest lived of ...

''. The genital appendage (a ventral "rod" part of the

reproductive system The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are al ...

) is present in the only known specimen but it is poorly preserved, with its

distal Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provi ...

end missing. It spanned from the first to the third

sternite The sternum (: sterna) is the ventral portion of a segment of an arthropod thorax or abdomen. In insects, the sterna are usually single, large sclerites, and external. However, they can sometimes be divided in two or more, in which case the su ...

(ventral half of the body segment) and was of type A, that is, the specimen was female.

History of research

The only known specimen of ''Pruemopterus'' was discovered by the German paleontologist Markus J. Poschmann in the 1980s. It was discovered in a now disused sandstone quarry within the municipality of Hermespand, close to the village itself and to that of Willwerath, in Weinsheim, Germany. The fossil

deposits A deposit account is a bank account maintained by a financial institution in which a customer can deposit and withdraw money. Deposit accounts can be savings accounts, current accounts or any of several other types of accounts explained below. ...

the specimen was uncovered in belong to the

Klerf Formation The Klerf Formation is an Early Devonian (Emsian) formation that includes a Lagerstätte in the Northern Eifel hills, at Willwerath near Prüm, Rhineland-Palatinate, Germany. In it ''Jaekelopterus rhenaniae'', a giant eurypterid was discovered. ...

and are of

age, specifically the uppermost Lower

Emsian The Emsian is one of three faunal stages in the Early Devonian Epoch. It lasted from 410.62 ±1.95 million years ago to 393.47 ±0.99 million years ago. It was preceded by the Pragian Stage and followed by the Eifelian Stage. It is named after ...

epoch. 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 ''

'', known from the same deposits, but differing in features of its carapace, opisthosoma and telson. Poschmann thus named the new

and species ''Pruemopterus salgadoi'' to accommodate the specimen. The specimen is today housed at the Generaldirektion Kulturelles Erbe, Direktion Landesarchäologie/Erdgeschichte in

Koblenz Koblenz ( , , ; Moselle Franconian language, Moselle Franconian: ''Kowelenz'') is a German city on the banks of the Rhine (Middle Rhine) and the Moselle, a multinational tributary. Koblenz was established as a Roman Empire, Roman military p ...

, 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 now has the repository number PWL 2014/5186-LS a,b (a being the part and b being the counterpart of the

compression fossil A compression fossil is a fossil preserved in sedimentary rock that has undergone physical compression. While it is uncommon to find animals preserved as good compression fossils, it is very common to find plants preserved this way. The reason f ...

). The generic name ''Pruemopterus'' is derived from the

and the surrounding Prüm valley, wherein Hermespand and Willwerath are located, and the suffix '-''opterus''', derived from the

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

Classification

Poschmann referred ''Pruemopterus'' to the eurypterid family Adelophthalmidae, the only family within the superfamily

Adelophthalmoidea Adelophthalmidae (the name deriving from the type genus ''Adelophthalmus'', meaning "no obvious Compound eyes, eyes") is a Family (biology), family of eurypterids, an extinct group of aquatic arthropods. Adelophthalmidae is the only family class ...

. In particular, Poschmann noted that morphological comparisons with other adelophthalmid genera suggest that ''Pruemopterus'' was most closely related to ''Parahughmilleria''. Still, ''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'', ''

Nanahughmilleria ''Nanahughmilleria'' ("dwarf ''Hughmilleria''") is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of ''Nanahughmilleria'' have been discovered in deposits of Devonian and Silurian age in the United States, Norway, Russia, ...

'' and ''Adelophthalmus''. The same also applies to ''Parahughmilleria'', which lived during the same epoch as ''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 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. Poschmann also noted in his description of the

type specimen In biology, a type is a particular wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...

that there were also close similarities to the

Hughmilleriidae Hughmilleriidae (the name deriving from the type genus ''Hughmilleria'', which is named in honor of Scottish geologist Hugh Miller) is a family of eurypterids, an extinct group of aquatic arthropods. The hughmilleriids were the most basal member ...

in the

Pterygotioidea Pterygotioidea (the name deriving from the type genus ''Pterygotus'', meaning "winged one") is a superfamily (taxonomy), superfamily of eurypterids, an extinct group of aquatic arthropods. Pterygotioids were the most Derived trait, derived membe ...

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 an Early Devonian fossil locality called the "Fossil-Lagerstätte Willwerath" that has yielded numerous early land plants, arthropods and vertebrates. Among the

chelicerates The subphylum Chelicerata (from Neo-Latin, , ) constitutes one of the major subdivisions of the phylum Arthropoda. Chelicerates include the sea spiders, horseshoe crabs, and arachnids (including harvestmen, scorpions, spiders, solifuges, tic ...

, to which the eurypterids belong, the Early Devonian deposits have yielded both

arachnids Arachnids are arthropods in the class Arachnida () of the subphylum Chelicerata. Arachnida includes, among others, spiders, scorpions, ticks, mites, pseudoscorpions, harvestmen, camel spiders, whip spiders and vinegaroons. Adult arachnids ...

('' Devonotarbus hombachensis'' and '' Xenarachne willwerathensis'') and early

xiphosura Xiphosura (; , in reference to its sword-like telson) is an order of arthropods related to arachnids. They are more commonly known as horseshoe crabs (a name applied more specifically to the only extant family, Horseshoe crab, Limulidae). They fir ...

ns (genus ''

Willwerathia ''Willwerathia'' is a genus of Devonian arthropod. It is sometimes classified as synziphosurine, a paraphyletic group of horseshoe crab-like fossil chelicerate arthropods, while some studies compare its morphology to an Artiopoda, artiopod. ''Wi ...

''). Eurypterids are especially diverse in these deposits, accounting for five genera in addition to ''Pruemopterus'': ''

Jaekelopterus ''Jaekelopterus'' is a genus of predatory eurypterid Eurypterids, often informally called sea scorpions, are a group of extinct marine arthropods that form the Order (biology), order Eurypterida. The earliest known eurypterids date to the ...

'', ''

Rhenopterus ''Rhenopterus'' is an extinct prehistoric eurypterid. Fossils of ''Rhenopterus'' have been recovered from deposits of Lower Devonian age in Germany.Dunlop, J. A., Penney, D. & Jekel, D. 2015. A summary list of fossil spiders and their relatives. ...

'', '' 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

, such as an

estuary An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime enviro ...

or a

bay A bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean, a lake, or another bay. A large bay is usually called a ''gulf'', ''sea'', ''sound'', or ''bight''. A ''cove'' is a small, ci ...

. The

lithology The lithology of a rock unit is a description of its physical characteristics visible at outcrop, in hand or core samples, or with low magnification microscopy. Physical characteristics include colour, texture, grain size, and composition. Lit ...

of the deposits in which ''Pruemopterus'' was discovered is composed of

lithified Lithification (from the Ancient Greek word ''lithos'' meaning 'rock' and the Latin-derived suffix ''-ific'') is the process in which sediments compact under pressure, expel connate fluids, and gradually become solid rock. Essentially, lithificati ...

gray

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility. Although its permeabil ...

References

{{Taxonbar, from=Q104856895 Devonian eurypterids Eurypterids of Europe Fossil taxa described in 2020 Adelophthalmoidea

Description

History of research

Classification

Paleoecology

See also

References