''Pulmonoscorpius'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

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 ...

scorpion Scorpions are predatory arachnids of the Order (biology), order Scorpiones. They have eight legs and are easily recognized by a pair of Chela (organ), grasping pincers and a narrow, segmented tail, often carried in a characteristic forward cur ...

from the Mississippian (Early

Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

) of

Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...

. It contains a single named

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

, ''Pulmonoscorpius kirktonensis''. It was one of the largest scorpions to have ever lived, with the largest known individual having an estimated length exceeding 70 cm (28 inches). ''Pulmonoscorpius'' retains several general arthropod features which are absent in modern scorpions, such as large lateral eyes and a lack of adaptations for a burrowing lifestyle. It was likely an active diurnal predator, and the presence of

book lungs A book lung is a type of respiration organ used for atmospheric gas-exchange that is present in many arachnids, such as scorpions and spiders. Each of these organs is located inside an open, ventral-abdominal, air-filled cavity (atrium) and co ...

indicates that it was fully terrestrial.

Discovery

East Kirkton Quarry in West Lothian in Scotland 1

Fossils of ''Pulmonoscorpius kirktonensis'' have been found at the East Kirkton Quarry,

West Lothian West Lothian (; ) is one of the 32 council areas of Scotland, bordering (in a clockwise direction) the City of Edinburgh council area, Scottish Borders, South Lanarkshire, North Lanarkshire and Falkirk (council area), Falkirk. The modern counci ...

. Rock layers exposed at the quarry date back to the

, specifically the

Viséan The Visean, Viséan or Visian is an age in the ICS geologic timescale or a stage in the stratigraphic column. It is the second stage of the Mississippian, the lower subsystem of the Carboniferous. The Visean lasted from to Ma. It follows ...

and

Serpukhovian The Serpukhovian is in the ICS geologic timescale the uppermost stage or youngest age of the Mississippian, the lower subsystem of the Carboniferous. The Serpukhovian age lasted from Ma to Ma. It is preceded by the Visean and is followed ...

stages of the Mississippian (Early Carboniferous) subperiod, around 336.0 – 326.4 million years ago. The

name A name is a term used for identification by an external observer. They can identify a class or category of things, or a single thing, either uniquely, or within a given context. The entity identified by a name is called its referent. A person ...

derives from "

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

''pulmonis'', a lung, and

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

''skorpios'', a scorpion." The species name "kirktonensis" refers to the East Kirkton Quarry. ''Pulmonoscorpius'' was described in 1994 based on 16 complete specimens and over 300 additional fragments from East Kirkton. In each specimen, only the outer layer of

hyaline A hyaline substance is one with a glassy appearance. The word is derived from , and . Histopathology Hyaline cartilage is named after its glassy appearance on fresh gross pathology. On light microscopy of H&E stained slides, the extracellula ...

cuticle A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...

is preserved, estimated to only be 15-18 μm thick in the largest specimen. Scorpion cuticle is present in the East Kirkton Limestone (lower exposed unit) and Little Cliff Shale (middle exposed unit), but not the Geikie Tuff (upper exposed unit). Although cuticle could be found in a variety of

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...

and

carbonate A carbonate is a salt of carbonic acid, (), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word "carbonate" may also refer to a carbonate ester, an organic compound containing the carbonate group ...

facies In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with distinctive characteristics. The characteristics can be any observable attribute of rocks (such as their overall appearance, composition, or con ...

, it is most easily prepared out of finely-laminated

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

, which can be dissolved away with dilute

hydrochloric acid Hydrochloric acid, also known as muriatic acid or spirits of salt, is an aqueous solution of hydrogen chloride (HCl). It is a colorless solution with a distinctive pungency, pungent smell. It is classified as a acid strength, strong acid. It is ...

while leaving the organic cuticle unharmed. Almost all material is completely flattened, so three-dimensional reconstructions are mostly hypothetical.

Description

The diet of ''Pulmonoscorpius'' is not known directly, but it is probable that it preyed on smaller

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, and small

tetrapod A tetrapod (; from Ancient Greek :wiktionary:τετρα-#Ancient Greek, τετρα- ''(tetra-)'' 'four' and :wiktionary:πούς#Ancient Greek, πούς ''(poús)'' 'foot') is any four-Limb (anatomy), limbed vertebrate animal of the clade Tetr ...

s (new arrivals). Most complete specimens were in length, while a large, fragmentary specimen is estimated to have been long when alive. The only portions preserved were the outer portions of the cuticle.

Dorsal surface

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 ''cepha ...

(the head section, also known as a cephalothorax) of ''Pulmonoscorpius'' is covered by a

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 ...

(a large plate), where it possess two pairs of eyes. These include a pair of anterior-positioned median eyes (near the center of the carapace) and a pair of compound lateral eyes (on the edge of the carapace), with each lateral eye bearing between 40 and 60 lateral

ocelli A simple eye or ocellus (sometimes called a pigment pit) is a form of eye or an optical arrangement which has a single lens without the sort of elaborate retina that occurs in most vertebrates. These eyes are called "simple" to distinguish the ...

. In modern scorpions, lateral eyes are strongly reduced, but those of ''Pulmonoscorpius'' are large, similar to other basal scorpions and most other arthropods. The prosoma is followed by a

mesosoma The mesosoma is the middle part of the body, or tagma, of arthropods whose body is composed of three parts, the other two being the prosoma and the metasoma. It bears the legs, and, in the case of winged insects, the wings. Wasps, bees and a ...

(the broad portion of the

abdomen The abdomen (colloquially called the gut, belly, tummy, midriff, tucky, or stomach) is the front part of the torso between the thorax (chest) and pelvis in humans and in other vertebrates. The area occupied by the abdomen is called the abdominal ...

-like

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 ...

), which has seven segments each covered by a tergite (smaller, broad plate). The surface of the carapace and tergites are relatively smooth in juveniles, and become tuberculated as individuals mature. The

metasoma The metasoma is the posterior part of the body, or tagma (biology), tagma, of arthropods whose body is composed of three parts, the other two being the prosoma and the mesosoma. In insects, it contains most of the digestive tract, respiratory sy ...

(the so-called "tail") has five segments, not counting the bulbous

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 ...

(stinging section, the actual, post-anal tail) at the end. The last (5th) metasomal segment does not exceed the length of the preceding (4th) metasomal segment. Metasomal segments are boxy and ornamented by 4 pairs of carinae (tuberculated ridges) in adults. The strongest carinae are the dorsal (upper) pair, and superior lateral (upper part of the side). Inferior lateral (lower part of the side), and inferior median (underside) carinae are also present.

Sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

may be present in ''Pulmonoscorpius'', as some specimens (females?) have wider metasomal segments. In ''Pulmonoscorpius kirktonensis'', the vesicle (venom-bearing portion of the telson) has a pair of strong carinae on its underside. One unique juvenile specimen is observed to lack these carinae, and may belong to a separate species (''Pulmonoscorpius'' sp. A).

Ventral structures

20210110 Pulmonoscorpius juvenile ventral

The coxae of each leg (the segment closest to the body) converge along the underside of the prosoma. The

sternum The sternum (: sternums or sterna) or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major bl ...

(ventral plate between the coxae of legs 3 and 4) is characteristically elongated, with a Y-shaped sulcus at the rear. The underside of the mesosoma possesses a bilobed and laterally elongated genital operculum (a covering of the

gonopore A gonopore, sometimes called a gonadopore, is a genital pore in many invertebrates. Hexapods, including insects, have a single common gonopore, except mayflies, which have a pair of gonopores. More specifically, in the unmodified female, it is ...

), followed by pectines (comb-like sensory appendages) with 150–160 narrow teeth, and finally ventral plates (3 in juveniles and 4 in adults). In juveniles, the first ventral plate has a unique median lobation. As with modern scorpions, four pairs of

were present at the corresponding ventral plates.

Appendages

Like other scorpions, ''Pulmonoscorpius'' has four pairs of walking legs as well as larger pincer-like

pedipalps Pedipalps (commonly shortened to palps or palpi) are the secondary pair of forward appendages among Chelicerata, chelicerates – a group of arthropods including spiders, scorpions, horseshoe crabs, and sea spiders. The pedipalps are lateral to ...

and smaller pincer-like

chelicerae The chelicerae () are the arthropod mouthparts, mouthparts of the subphylum Chelicerata, an arthropod group that includes arachnids, horseshoe crabs, and sea spiders. Commonly referred to as "jaws", chelicerae may be shaped as either articulated ...

(mouthparts). One characteristic trait of ''Pulmonoscorpius'' is the presence of a long spur on each of the apophyses (an extension of the coxa). The chelicerae and legs were noted be to be similar to those of extant scorpions, except that the coxa and

femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...

(first and third segments) in legs 3 and 4 are less elongated, and the

tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...

(fifth segment) of these legs are elongated to about the same length as their femur. In the pedipalps, the femur and patella (fourth segment) are lined with carinae.

Setae In biology, setae (; seta ; ) are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Depending partly on their form and function, protostome setae may be called macrotrichia, chaetae ...

(hairs) are sparse and clustered, particularly in larger individuals. Setae density is highest on the large (fixed) finger of the pedipalps. One juvenile specimen has 30% more setae on its fixed finger than any other ''Pulmonoscorpius kirktonensis'' specimen. This specimen may belong to a separate species (''Pulmonoscorpius'' sp. B). Aside from the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

, two other specimens were noted to possibly be distinct: one having juvenile pedipalp fingers with 30% more

seta In biology, setae (; seta ; ) are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Depending partly on their form and function, protostome setae may be called macrotrichia, chaetae, ...

l follicles than ''P. kirktonensis,'' and one lacking tuberculateventral carinae on the vesicle of its

References

External links

* https://web.archive.org/web/20061023072618/http://www.langsfossils.com/museum/pages/m-scld-002.htm * http://dml.cmnh.org/1999Jun/msg00432.html
Images of the holotype fossil at GB3D
{{Taxonbar, from=Q612611 Prehistoric scorpions Paleozoic arachnids Carboniferous arthropods of Europe Carboniferous arachnids Viséan life Carboniferous Scotland Fossils of Scotland Fossil taxa described in 1994