''Vernonopterus'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

eurypterid Eurypterids, often informally called sea scorpions, are a group of extinct arthropods that form the order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period 467.3 million years ago. The group is ...

, a group of extinct aquatic

arthropods Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chitin, oft ...

Fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s of ''Vernonopterus'' have been discovered in

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. ...

of the Carboniferous period in

Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to th ...

. The name of the genus derives from the location where the only known fossil has been discovered,

Mount Vernon Mount Vernon is an American landmark and former plantation of Founding Father, commander of the Continental Army in the Revolutionary War, and the first president of the United States George Washington and his wife, Martha. The estate is ...

near Airdrie in

Lanarkshire Lanarkshire, also called the County of Lanark ( gd, Siorrachd Lannraig; sco, Lanrikshire), is a historic county, lieutenancy area and registration county in the central Lowlands of Scotland. Lanarkshire is the most populous county in Scot ...

, Scotland. A single

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

of ''Vernonopterus'' is recognized, ''V. minutisculptus'', based on fragmentary fossilized

tergites A ''tergum'' (Latin for "the back"; plural ''terga'', associated adjective tergal) is the dorsal ('upper') portion of an arthropod segment other than the head. The anterior edge is called the 'base' and posterior edge is called the 'apex' or 'mar ...

, segments on the upper side of the

abdomen The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the tors ...

. The species name ''minutisculptus'' refers to the

ornamentation An ornament is something used for decoration. Ornament may also refer to: Decoration *Ornament (art), any purely decorative element in architecture and the decorative arts * Biological ornament, a characteristic of animals that appear to serve o ...

scales Scale or scales may refer to: Mathematics * Scale (descriptive set theory), an object defined on a set of points * Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original * Scale factor, a number ...

that covers the entirety of the preserved parts of the eurypterid. Although little can confidently be said about the appearance of ''Vernonopterus'', it is likely to have been similar to its relatives within the

hibbertopterid Hibbertopteridae (the name deriving from the type genus ''Hibbertopterus'', meaning "Hibbert's wing") is a family of eurypterids, an extinct group of aquatic arthropods. They were members of the superfamily Mycteropoidea. Hibbertopterids were larg ...

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

, ''

Hibbertopterus ''Hibbertopterus'' is a genus of eurypterid, a group of extinct aquatic arthropods. Fossils of ''Hibbertopterus'' have been discovered in deposits ranging from the Devonian period in Belgium, Scotland and the United States to the Carboniferous ...

'' and ''

Campylocephalus ''Campylocephalus'' is a genus of eurypterid, a group of extinct aquatic arthropods. Fossils of ''Campylocephalus'' have been discovered in deposits ranging from the Carboniferous period in the Czech Republic (the species ''C. salmi'') to the Pe ...

''. The hibbertopterids were large eurypterids with broad heads and bodies and

appendages An appendage (or outgrowth) is an external body part, or natural prolongation, that protrudes from an organism's body. In arthropods, an appendage refers to any of the homologous body parts that may extend from a body segment, including antenn ...

developed for sweep-feeding, a technique involving blade-like adaptations to search for food in the

substrate Substrate may refer to: Physical layers *Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached ** Substrate (locomotion), the surface over which an organism lo ...

of its living

environment Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...

. Compared to both ''Hibbertopterus'' and ''Campylocephalus'', ''Vernonopterus'' would have been small, reaching lengths of about 50 centimetres (19.7 inches).

Description

Classified as a member of the

eurypterids Eurypterids, often informally called sea scorpions, are a group of extinct arthropods that form the order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period 467.3 million years ago. The group is l ...

, ''Vernonopterus'' is assumed to have been overall similar to the other members of the family. The scant

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

remains attributed to the eurypterid suggests that it was a large and broad-bodied animal that probably measured around 50 centimetres (19.7 inches) in length. Although limited in number by the fragmentary nature of the fossil remains, some distinguishing features of ''Vernonopterus'' have been established. In particular, the more

posterior Posterior may refer to: * Posterior (anatomy), the end of an organism opposite to its head ** Buttocks, as a euphemism * Posterior horn (disambiguation) * Posterior probability, the conditional probability that is assigned when the relevant evidenc ...

(further towards the back)

( segments on the upper side of the

) tend to become more and more trilobate (shaped so that they almost have three distinct lobes), in the middle of the tergites the

(something typical of eurypterid

exoskeleton An exoskeleton (from Greek ''éxō'' "outer" and ''skeletós'' "skeleton") is an external skeleton that supports and protects an animal's body, in contrast to an internal skeleton ( endoskeleton) in for example, a human. In usage, some of the ...

s) form a series of tracts that almost morph into three ridges. Due to the tergites being the only known parts of ''Vernonopterus'', next to nothing can be said about other parts of its body such as the head and the

(limbs). They are likely to have resembled those of its relatives, where 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 und ...

(exoskeleton covering the head) was large and broad (similar to the rest of the body) with appendages developed to sweep-feeding, a technique involving blade-like adaptations to search for food in the

of its living

. The

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

plates of ''Vernonopterus'' were granulated finely (had a rough surface) with small

being present near the posterior borders of the plates. In the middle of the tergites, the ornamentation is more pronounced than at their borders, taking the form of semi-lunar (almost moon-shaped) scales. Further back on the eurypterids' body, these scales change into larger scales grouped into large longitudinal ridges. On the borders of the later tergites, these large scales protrude and form structures similar to

crenulations In a geological context, crenulation or crenulation cleavage is a fabric formed in metamorphic rocks such as phyllite, schist and some gneiss by two or more stress directions causing the formation of the superimposed foliations. Formation Crenula ...

. The longitudinal ridges divide the tergites of ''Vernonopterus'' into axial (spine) and pleural (ribs) parts, which differentiates it from all other hibbertopterids.Hughes, Emily (2019).
Discerning the Diets of Sweep-Feeding Eurypterids Through Analyses of Mesh-Modified Appendage Armature
'. West Virginia University Graduate Theses, Dissertations, and Problem Reports.

History of research

The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of seve ...

and only known specimen of ''Vernonopterus'' was discovered by local fossil hunter Robert Dunlop in coal measures at

near Airdrie in

in 1884. The fossil, at the present stored at the

Royal Scottish Museum The National Museum of Scotland in Edinburgh, Scotland, was formed in 2006 with the merger of the new Museum of Scotland, with collections relating to Scottish antiquities, culture and history, and the adjacent Royal Scottish Museum (opened in ...

with the specimen number 1957.1.4992, consists of a series of fragmentary tergites. It wasn't described scientifically until 1905, when British

geologist A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes Earth and other terrestrial planets, as well as the processes that shape them. Geologists usually study geology, earth science, or geophysics, alt ...

Ben Peach Benjamin Neeve Peach (6 September 1842 – 29 January 1926) was a British geologist. Life Peach was born at Gorran Haven in Cornwall on 6 September 1842 to Jemima Mabson and Charles William Peach, an amateur British naturalist and geologi ...

described the specimen and assigned it to a new

of the

''Glyptoscorpius'' (a name today recognized as synonymous with ''

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 ...

'') as ''G. minutisculptus''. Peach's description has been criticized by later researchers as inadequate and in some ways misleading. Peach considered the fossil's horizon to prove that ''Glyptoscorpius'' was a land animal since it was preserved alongside plant fossils. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

''minutisculptus'' refers to the ornementation that covers the entirety of the preserved portions of the animal. The specimen was given a more complete description by British geologist Charles D. Waterston in 1957, who instead referred it to the genus ''

Eurypterus ''Eurypterus'' ( ) is an extinct genus of eurypterid, a group of organisms commonly called "sea scorpions". The genus lived during the Silurian period, from around 432 to 418 million years ago. ''Eurypterus'' is by far the most well-studied and ...

'' as ''E. minutisculptus''. By this time it had been encased in a collar of "fibrenyle" packaging (a type of plastic) to give strength to and preserve the very fragile fossil. Features revealed during Waterston's second examination of the fossil in 1968 made it clear that the eurypterid was not congeneric with known species of ''Eurypterus'', nor part of the

eurypterine Eurypterina is one of two suborders of eurypterids, an extinct group of chelicerate arthropods commonly known as "sea scorpions". Eurypterine eurypterids are sometimes informally known as "swimming eurypterids". They are known from fossil deposi ...

suborder Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...

(eurypterids that possessed swimming paddles) at all. Instead, Waterston inferred that ''E. minutisculptus'' had very clearly been a broad-bodied and large eurypterid, although any detailed statements about the

prosoma The cephalothorax, also called prosoma in some groups, is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. (The terms ''prosoma'' and ''opisthosoma'' are equivalent to ''ce ...

(head), appendages and the

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

(the posteriormost division of the body, often taking the shape of a tail spike) could not be made as those portions of the body were unknown. Waterston created a new genus to contain the species, ''Vernonopterus'', with the name deriving from the location where the fossil had been found, Mount Vernon. Waterston referred the new genus to the family "Woodwardopteridae" (now referred to as the

Mycteroptidae Mycteroptidae are a family of eurypterids, a group of extinct chelicerate arthropods commonly known as "sea scorpions". The family is one of three families contained in the superfamily Mycteropoidea (along with Hibbertopteridae and Drepanopter ...

), but no particular reasoning was given. ''Vernonopterus'' was assigned to ''

'' by Cuban paleontolgost Erik N. Kjellesvig-Waering in 1966 as ''H. minutisculptus'', but he noted that this classification was not certain. Similarities between the ''Vernonopterus'' specimen and specimens referred to ''Dunsopterus'' (today recognized as a junior synonym of ''Hibbertopterus'') were noted by Waterston and Norwegian paleontologist

Leif Størmer Leif Størmer (1 July 1905 – 15 May 1979) was a Norwegian paleontologist and geologist. He was professor of historical geology at the University of Oslo from 1946 to 1975. His father was the mathematician Carl Størmer, and his son the mathemat ...

in 1968. Modern researchers classify the genus within the Hibbertopteridae instead, sometimes noting that its position is somewhat uncertain due to its fragmentary nature.

Classification

''Vernonopterus'' is classified as part of the family Hibbertopteridae, a family of eurypterids within the

superfamily SUPERFAMILY is a database and search platform of structural and functional annotation for all proteins and genomes. It classifies amino acid sequences into known structural domains, especially into SCOP superfamilies. Domains are functional, str ...

Mycteropoidea Mycteropoidea is an extinct superfamily of eurypterids, an extinct group of chelicerate arthropods commonly known as "sea scorpions". It is one of four superfamilies classified as part of the suborder Stylonurina. Mycteropoids have been recovered ...

, alongside the genera ''Hibbertopterus'' and ''

''. The genus contains one species; ''V. minutisculptus'' from the Carboniferous of Lanarkshire, Scotland.Dunlop, J. A., Penney, D. & Jekel, D. 2015. A summary list of fossil spiders and their relatives. In World Spider Catalog. Natural History Museum Bern, online at http://wsc.nmbe.ch, version 16.0 http://www.wsc.nmbe.ch/resources/fossils/Fossils16.0.pdf (PDF). The hibbertopterids are united as a group by being large mycteropoids with broad prosomas, a hastate (e.g. shaped like a ''

gladius ''Gladius'' () is a Latin word meaning "sword" (of any type), but in its narrow sense it refers to the sword of ancient Roman foot soldiers. Early ancient Roman swords were similar to those of the Greeks, called '' xiphe'' (plural; singular ''xi ...

'', a

Roman Roman or Romans most often refers to: *Rome, the capital city of Italy *Ancient Rome, Roman civilization from 8th century BC to 5th century AD * Roman people, the people of ancient Rome *'' Epistle to the Romans'', shortened to ''Romans'', a lett ...

sword) telson with paired keels on the ventral side, ornamentation consisting of scales or other similar structures on the exoskeleton, the fourth pair of appendages possessing spines, the more posterior tergites of the abdomen possessing tongue-shaped scales near their edges and there being lobes positioned posterolaterally (posteriorly on both sides) on the prosoma. The features of ''Campylocephalus'' and ''Vernonopterus'' makes it clear that both genera represent hibbertopterid eurypterids, but the incomplete nature of all fossil specimens referred to them make any further study of the precise

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

relationships within the Hibbertopteridae difficult. Both genera could even represent synonyms of ''Hibbertopterus'' itself, though the highly incomplete nature of their remains again makes that hypothesis impossible to confirm. By comparing the ornamentation of various hibbertopterids in 2019, American geologist Emily Hughes could conclude that several genera were actually congeneric, subsuming some previously recognized hibbertopterids (such as ''Cyrtoctenus'') into ''Hibbertopterus''. She noted that the distinct ornamentation of ''Vernonopterus'' supported it as a distinct genus.

Paleoecology

''Vernonopterus'' lived during the Westphalian age in modern-day Lanarkshire, Scotland. Though they probably would not have been prey items to ''Vernonopterus'', a diverse contemporary fauna of actinopterygian fish are known from Lanarkshire as well, including species such as ''

Rhadinichthys ''Rhadinichthys'' is an extinct genus of prehistoric bony fish. It is known from several species that lived in the Late Devonian epoch, the Carboniferous period and the Cisuralian epoch (early Permian) in what is now Europe, South Africa, and ...

ornatocephalum'', ''R. glabrolepis'', ''R. plumosum'', '' Pseudogonatodus aurulentum'' and '' Lanarkichthys gardineri''. Out of this actinopterygian diversity, there are many haplolepid fishes, a small and basal group, known, including '' Blairolepis wallacei'', '' Parahaplolepis poppaea'', ''P. elenae'', ''P. alexandrae'', '' Braccohaplolepis fenestratum'', '' Andrewsolepis lochlani'', '' Protohaplolepis isabellae'', ''P. limnades'', ''P. traquairi'', '' Pyritocephalus youngii'' and '' Millerolepis eleionomae''. ''Vernonopterus'' and these fish would have lived in a

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 salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does incl ...

environment. Hibbertopterids such as ''Vernonopterus'' were sweep-feeders, having modified spines on their forward-facing prosomal appendages that allowed them to rake through the substrate of their living environments. Though sweep-feeding was used as a strategy by many genera within the

Stylonurina Stylonurina is one of two suborders of eurypterids, a group of extinct arthropods commonly known as "sea scorpions". Members of the suborder are collectively and informally known as "stylonurine eurypterids" or "stylonurines". They are known fro ...

, it was most developed within the hibbertopterids, which possessed blades on the second, third and fourth pair of appendages. Some species of the closely related ''Hibbertopterus'' had specialized comb-like

rachis In biology, a rachis (from the grc, ῥάχις [], "backbone, spine") is a main axis or "shaft". In zoology and microbiology In vertebrates, ''rachis'' can refer to the series of articulated vertebrae, which encase the spinal cord. In this c ...

(shafts) that were able to entrap small prey and other organic food particles. Though they would have been slow owing to their massive size and robust form, studies on ''Hibbertopterus'' footprints discovered in Scotland have demonstrated that hibbertopterids would have been able to walk on land for at least short periods of time. The tracks discovered indicate that they would have utilized a lumbering, jerking and dragging movement and that the keeled belly and the telson left a central groove behind. Some studies suggest that eurypterids possessed a dual respiratory system (capable of breathing in both air and underwater), which would have allowed for this kind of occasional terrestrial movement.

References

{{Taxonbar, from=Q48847559 Carboniferous eurypterids Stylonurina Eurypterids of Europe Carboniferous arthropods of Europe

Description

History of research

Classification

Paleoecology

See also

References