138-485: Slimonia is a genus of eurypterid , an extinct group of aquatic arthropods . Fossils of Slimonia have been discovered in deposits of Silurian age in South America and Europe . Classified as part of the family Slimonidae alongside the related Salteropterus , the genus contains three valid species, S. acuminata from Lesmahagow , Scotland , S. boliviana from Cochabamba , Bolivia and S. dubia from
276-578: A cosmopolitan distribution . Though the eurypterids continued to be abundant and diversify during the Early Devonian (for instance leading to the evolution of the pterygotid Jaekelopterus , the largest of all arthropods), the group was one of many heavily affected by the Late Devonian extinction . The extinction event, only known to affect marine life (particularly trilobites, brachiopods and reef -building organisms) effectively crippled
414-408: A lung , plastron or a pseudotrachea . Plastrons are organs that some arthropods evolved secondarily to breathe air underwater. This is considered an unlikely explanation since eurypterids had evolved in water from the start and they would not have organs evolved from air-breathing organs present. In addition, plastrons are generally exposed on outer parts of the body while the eurypterid gill tract
552-459: A few genera, such as Adelophthalmus and Pterygotus , achieved a cosmopolitan distribution with fossils being found worldwide. Like all other arthropods , eurypterids possessed segmented bodies and jointed appendages (limbs) covered in a cuticle composed of proteins and chitin . As in other chelicerates , the body was divided into two tagmata (sections); the frontal prosoma (head) and posterior opisthosoma (abdomen). The prosoma
690-742: A gait like that of most modern insects. The weight of its long abdomen would have been balanced by two heavy and specialized frontal appendages, and the center of gravity might have been adjustable by raising and positioning the tail. Preserved fossilized eurypterid trackways tend to be large and heteropodous and often have an associated telson drag mark along the mid-line (as with the Scottish Hibbertopterus track). Such trackways have been discovered on every continent except for South America. In some places where eurypterid fossil remains are otherwise rare, such as in South Africa and
828-658: A gigantic system of dislocations, whereby successive masses of the oldest gneisses , have been exhumed from below and thrust over the younger formations. In 1855 Murchison was appointed director-general of the British Geological Survey and director of the Royal School of Mines and the Museum of Practical Geology in Jermyn Street, London, in succession to Sir Henry De la Beche , who had been
966-670: 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 likely to have appeared first either during the Early Ordovician or Late Cambrian period. With approximately 250 species, the Eurypterida is the most diverse Paleozoic chelicerate order. Following their appearance during
1104-416: A manner similar to modern horseshoe crabs, by grabbing and shredding food with their appendages before pushing it into their mouth using their chelicerae. Fossils preserving digestive tracts have been reported from fossils of various eurypterids, among them Carcinosoma , Acutiramus and Eurypterus . Though a potential anal opening has been reported from the telson of a specimen of Buffalopterus , it
1242-522: A member of the Pterygotidae, until it was reclassified alongside Hughmilleria and other genera to the family Hughmilleriidae in 1951 by Erik N. Kjellesvig-Waering. Nestor Ivanovich Novojilov classified Slimonia as part of a family of its own in 1968. Slimonia is one of the most closely related genera to the pterygotid family and the Slimonidae is often interpreted as a sister-taxon to
1380-425: A meter (1.64 ft) even if the extended chelicerae are not included. Two other eurypterids have also been estimated to have reached lengths of 2.5 metres; Erettopterus grandis (closely related to Jaekelopterus ) and Hibbertopterus wittebergensis , but E. grandis is very fragmentary and the H. wittenbergensis size estimate is based on trackway evidence, not fossil remains. The family of Jaekelopterus ,
1518-522: A new genus to contain the species, as several distinctive characteristics made the species considerably different from other known species of Pterygotus , among them the shape of the carapace and S. acuminata lacking the large cheliceral claws known from Pterygotus . The generic name is derived from and honors Robert Slimon, a fossil collector and surgeon from Lesmahagow. Slimon was the first to discover eurypterid fossils in Lesmahagow, bringing them to
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#17327932996901656-436: A possible life position. They further argued that since the telson of Slimonia also possessed a keel, this would have created significant drag on it while Slimonia was trying to laterally sweep the telson to stab its prey. Lastly, they argued that the serrations on the telson would most likely be attachment points for setae that would have aided the animal in sensing the water flow to make steering much easier. Visual acuity ,
1794-471: A rowing type of propulsion similar to that of crabs and water beetles . Larger individuals may have been capable of underwater flying (or subaqueous flight ) in which the motion and shape of the paddles are enough to generate lift , similar to the swimming of sea turtles and sea lions . This type of movement has a relatively slower acceleration rate than the rowing type, especially since adults have proportionally smaller paddles than juveniles. However, since
1932-453: A single row of large marginal scales that form a linear serrated edge. A slight dorsal keel is present along the telson. There was a triangular area at the base of the telson which could have been a point of union with the muscles. S. boliviana differed from S. acuminata in having the keel much less developed, narrower and not reaching the terminal spike. The latter was wider, not as pointed and with less developed serrations. The telson itself
2070-712: Is a Murchison Avenue in Old Bexley, southeast London. Scarborough in North Yorkshire has a Murchison Street. Murchison's View is named after him. The viewpoint within the Wren's Nest area of Dudley gives a panoramic view over much of Birmingham and the Black Country. Murchinson's visits to the limestone hills of Dudley helped him to develop his understanding of the Silurian System. When he returned to
2208-553: Is a genital appendage. This appendage, an elongated rod with an internal duct, is found in two distinct morphs, generally referred to as "type A" and "type B". These genital appendages are often preserved prominently in fossils and have been the subject of various interpretations of eurypterid reproduction and sexual dimorphism. Type A appendages are generally longer than those of type B. In some genera they are divided into different numbers of sections, such as in Eurypterus where
2346-495: Is a lightweight build. Factors such as locomotion, energy costs in molting and respiration, as well as the actual physical properties of the exoskeleton , limit the size that arthropods can reach. A lightweight construction significantly decreases the influence of these factors. Pterygotids were particularly lightweight, with most fossilized large body segments preserving as thin and unmineralized. Lightweight adaptations are present in other giant paleozoic arthropods as well, such as
2484-529: Is also possible and the structure may represent the unfused tips of the appendages. Located between the dorsal and ventral surfaces of the Blattfüsse associated with the type A appendages is a set of organs traditionally described as either "tubular organs" or "horn organs". These organs are most often interpreted as spermathecae (organs for storing sperm ), though this function is yet to be proven conclusively. In arthropods, spermathecae are used to store
2622-523: Is large for a predatory arthropod, Slimonia would be exceeded in length by later and more derived (more "advanced") members of the closely related pterygotid family of eurypterids, which would become the largest known arthropods to ever live. Slimonia is in many ways similar to the more derived (more "advanced") eurypterids of its superfamily, the Pterygotioidea . In particular, the expanded and flattened telson (the most posterior segment of
2760-489: Is located behind the Blattfüssen . Instead, among arthropod respiratory organs, the eurypterid gill tracts most closely resemble the pseudotracheae found in modern isopods . These organs, called pseudotracheae, because of some resemblance to the tracheae (windpipes) of air-breathing organisms, are lung-like and present within the pleopods (back legs) of isopods. The structure of the pseudotracheae has been compared to
2898-487: Is made up of the first six exoskeleton segments fused together into a larger structure. The seventh segment (thus the first opisthosomal segment) is referred to as the metastoma and the eighth segment (distinctly plate-like) is called the operculum and contains the genital aperature. The underside of this segment is occupied by the genital operculum, a structure originally evolved from ancestral seventh and eighth pair of appendages. In its center, as in modern horseshoe crabs,
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#17327932996903036-786: Is more closely related to the Pterygotidae than the Hughmilleriidae is. The cladogram below is simplified from a study by O. Erik Tetlie (2007), and showcases the position of Slimonia relative to the rest of the Eurypterina suborder of eurypterids, with the Stylonurina suborder as an outgroup . Stylonurina Megalograptoidea Eurypteroidea Carcinosomatoidea Waeringopteroidea Adelophthalmoidea Hughmilleria Herefordopterus Slimonia Pterygotidae In 2017, W. Scott Persons IV and John Acorn reported finding an S. acuminata specimen, MB.A 863, in
3174-521: Is more likely that the anus was opened through the thin cuticle between the last segment before the telson and the telson itself, as in modern horseshoe crabs. Eurypterid coprolites discovered in deposits of Ordovician age in Ohio containing fragments of a trilobite and eurypterid Megalograptus ohioensis in association with full specimens of the same eurypterid species have been suggested to represent evidence of cannibalism . Similar coprolites referred to
3312-544: Is much more of a marine influence in many of the sections yielding Adelophthalmus than has previously been acknowledged." Similarly, a study of the eurypterid Hibbertopterus from the Carboniferous of New Mexico concluded that the habitat of some eurypterids "may need to be re-evaluated". The sole surviving eurypterine family, Adelophthalmidae, was represented by only a single genus, Adelophthalmus . The hibbertopterids, mycteroptids and Adelophthalmus survived into
3450-638: Is possible that many eurypterid species thought to be distinct actually represent juvenile specimens of other species, with paleontologists rarely considering the influence of ontogeny when describing new species. Studies on a well-preserved fossil assemblage of eurypterids from the Pragian -aged Beartooth Butte Formation in Cottonwood Canyon , Wyoming , composed of multiple specimens of various developmental stages of eurypterids Jaekelopterus and Strobilopterus , revealed that eurypterid ontogeny
3588-470: Is referred to as the metastoma, originally derived from a complete exoskeleton segment. The opisthosoma itself can be divided either into a " mesosoma " (comprising segments 1 to 6) and " metasoma " (comprising segments 7 to 12) or into a "preabdomen" (generally comprising segments 1 to 7) and "postabdomen" (generally comprising segments 8 to 12). The underside of the opisthosoma was covered in structures evolved from modified opisthosomal appendages. Throughout
3726-439: Is the first record of land locomotion by a eurypterid. The trackway provides evidence that some eurypterids could survive in terrestrial environments, at least for short periods of time, and reveals information about the stylonurine gait. In Hibbertopterus , as in most eurypterids, the pairs of appendages are different in size (referred to as a heteropodous limb condition). These differently sized pairs would have moved in phase, and
3864-816: Is the metastoma becoming proportionally less wide. This ontogenetic change has been observed in members of several superfamilies, such as the Eurypteroidea, the Pterygotioidea and the Moselopteroidea . No fossil gut contents from eurypterids are known, so direct evidence of their diet is lacking. The eurypterid biology is particularly suggestive of a carnivorous lifestyle. Not only were many large (in general, most predators tend to be larger than their prey), but they had stereoscopic vision (the ability to perceive depth). The legs of many eurypterids were covered in thin spines, used both for locomotion and
4002-418: Is unlikely the "gill tract" contained functional gills when comparing the organ to gills in other invertebrates and even fish. Previous interpretations often identified the eurypterid "gills" as homologous with those of other groups (hence the terminology), with gas exchange occurring within the spongy tract and a pattern of branchio-cardiac and dendritic veins (as in related groups) carrying oxygenated blood into
4140-790: The American Antiquarian Society . Three years later, he was elected to the American Philosophical Society . In 1863 he was made a KCB , and three years later he was created a baronet . The learned societies of his own country bestowed their highest rewards upon him: the Royal Society gave him the Copley Medal , the Geological Society its Wollaston medal , and the Royal Society of Edinburgh its Brisbane Medal. There
4278-533: The Ancient Greek words εὐρύς ( eurús ), meaning 'broad' or 'wide', and πτερόν ( pterón ), meaning 'wing', referring to the pair of wide swimming appendages present in many members of the group. The eurypterid order includes the largest known arthropods ever to have lived. The largest, Jaekelopterus , reached 2.5 meters (8.2 ft) in length. Eurypterids were not uniformly large and most species were less than 20 centimeters (8 in) long;
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4416-636: The English border counties , were embodied in The Silurian System (1839). The English naturalist, geologist, and palaeontologist John William Salter assisted Murchison in his work on Siluria (1854 and later editions). The establishment of the Silurian system was followed by that of the Devonian system, an investigation in which Murchison assisted, both in the south-west of England and in
4554-581: The Highlands Controversy . James Nicol recognised the fallacy in Murchison's theory and propounded his own ideas; in the 1880s these were superseded by the correct theory of Charles Lapworth , which was corroborated by Benjamin Peach and John Horne . Their subsequent research showed that the infraposition of the fossiliferous rocks is not their original place, but had been brought about by
4692-613: The Kirusillas Formation , of Ludlow - Pridoli (Late Silurian) age, in Cochabamba , Bolivia . Named S. boliviana , the holotype (BLV15, deposited at the National Museum of Natural History of France ) comprises a well-preserved telson typical of the genus, being laterally inflated and with a dagger-like terminal point. It was anteriorly covered with small scales semilunar to mucronitic ("spined") grouped into
4830-626: The Old Red Sandstone could be grouped into a definite order of succession. The result was the establishment of the Silurian system under which were grouped, for the first time, a remarkable series of formations, each replete with distinctive organic remains other than and very different from those of the other rocks of England. These researches, together with descriptions of the coalfields and overlying formations in South Wales and
4968-564: The Patrick Burn Formation of Scotland, dated to the Telychian , around 430 million years ago. The specimen was a complete and articulated series of telsonal, postabdominal and preabdominal segments, and it showed a very strong lateral curvature in the postabdomen. Persons and Acorn admitted that it might have experienced some disarticulation postmortem or could represent a partial molt (exuviae), but concluded that since there
5106-520: The Pentland Hills of Scotland and one dubious species, S. stylops , from Herefordshire , England . The generic name is derived from and honors Robert Slimon, a fossil collector and surgeon from Lesmahagow. Out of the four described species of Slimonia , three measured below or up to 20 centimetres (7.9 in) in length. Only S. acuminata was larger, with the largest specimens measuring 100 centimetres (39 in) in length. Though this
5244-520: The Permian–Triassic extinction event (or sometime shortly before) 251.9 million years ago. Although popularly called "sea scorpions", only the earliest eurypterids were marine ; many later forms lived in brackish or fresh water , and they were not true scorpions . Some studies suggest that a dual respiratory system was present, which would have allowed for short periods of time in terrestrial environments. The name Eurypterida comes from
5382-534: The Pterygotioidea , the Hibbertopteridae and the Mycteroptidae , the telson was flattened and may have been used as a rudder while swimming. Some genera within the superfamily Carcinosomatoidea , notably Eusarcana , had a telson similar to that of modern scorpions and may have been capable of using it to inject venom . The coxae of the sixth pair of appendages were overlaid by a plate that
5520-572: The Rhineland . Soon afterwards Murchison projected an important geological campaign in Russia with the view of extending to that part of the Continent the classification he had succeeded in elaborating for the older rocks of western Europe. He was accompanied by Édouard de Verneuil (1805–1873) and Count Alexander von Keyserling (1815–1891), in conjunction with whom he produced a work on Russia and
5658-532: The Stylonuroidea , Kokomopteroidea and Mycteropoidea as well as eurypterine groups such as the Pterygotioidea, Eurypteroidea and Waeringopteroidea . The most successful eurypterid by far was the Middle to Late Silurian Eurypterus , a generalist , equally likely to have engaged in predation or scavenging . Thought to have hunted mainly small and soft-bodied invertebrates, such as worms , species of
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5796-620: The Ural Mountains . The publication of this monograph in 1845 completes the first and most active half of Murchison's scientific career. He was elected a Foreign Honorary Member of the American Academy of Arts and Sciences in 1840. In 1846 he was knighted, and in the same year he presided over the meeting of the British Association at Southampton . During the later years of his life, a large part of his time
5934-442: The rhizodonts , were the new apex predators in marine environments. However, various recent findings raise doubts about this, and suggest that these eurypterids were euryhaline forms that lived in marginal marine environments, such as estuaries, deltas, lagoons, and coastal ponds. One argument is paleobiogeographical; pterygotoid distribution seems to require oceanic dispersal. A recent review of Adelophthalmoidea admitted that "There
6072-405: The spermatophore received from males. This would imply that the type A appendage is the female morph and the type B appendage is the male. Further evidence for the type A appendages representing the female morph of genital appendages comes in their more complex construction (a general trend for female arthropod genitalia). It is possible that the greater length of the type A appendage means that it
6210-539: The Devonian, large two meter (6.5+ ft) pterygotids such as Acutiramus were already present during the Late Silurian. Their ecology ranged from generalized predatory behavior to ambush predation and some, such as Pterygotus itself, were active apex predators in Late Silurian marine ecosystems. The pterygotids were also evidently capable of crossing oceans, becoming one of only two eurypterid groups to achieve
6348-825: The Middle Ordovician suggests that eurypterids either originated during the Early Ordovician and experienced a rapid and explosive radiation and diversification soon after the first forms evolved, or that the group originated much earlier, perhaps during the Cambrian period. As such, the exact eurypterid time of origin remains unknown. Though fossils referred to as "primitive eurypterids" have occasionally been described from deposits of Cambrian or even Precambrian age, they are not recognized as eurypterids, and sometimes not even as related forms, today. Some animals previously seen as primitive eurypterids, such as
6486-602: The Middle Ordovician, 467.3 million years ago . There are also reports of even earlier fossil eurypterids in the Fezouata Biota of Late Tremadocian (Early Ordovician) age in Morocco , but these have yet to be thoroughly studied, and are likely to be peytoiid appendages. Pentecopterus was a relatively derived eurypterid, part of the megalograptid family within the carcinosomatoid superfamily. Its derived position suggests that most eurypterid clades, at least within
6624-602: The Middle Silurian and the Early Devonian, with an absolute peak in diversity during the Pridoli epoch , 423 to 419.2 million years ago, of the very latest Silurian. This peak in diversity has been recognized since the early twentieth century; of the approximately 150 species of eurypterids known in 1916, more than half were from the Silurian and a third were from the Late Silurian alone. Though stylonurine eurypterids generally remained rare and low in number, as had been
6762-542: The Ordovician, eurypterids became major components of marine faunas during the Silurian , from which the majority of eurypterid species have been described. The Silurian genus Eurypterus accounts for more than 90% of all known eurypterid specimens. Though the group continued to diversify during the subsequent Devonian period, the eurypterids were heavily affected by the Late Devonian extinction event . They declined in numbers and diversity until becoming extinct during
6900-1106: The Pentland Hills, where remains of S. dubia have been found, preserve fossils of a large amount of other eurypterids, including Drepanopterus pentlandicus , Laurieipterus elegans , Parastylonurus ornatus , Hardieopterus macrophthalmus , Carcinosoma scoticus , Stoermeropterus conicus and Pentlandopterus minor . Also preserved are fossils of orthocerids , such as Geisonoceras maclareni . Similar levels of eurypterid diversity are also observed in fossil deposits where other species of Slimonia have been found. S. acuminata has been found associated with Nanahughmilleria lanceolata , Hardieopterus lanarkensis , Eusarcana obesus , Parastylonurus sigmoidalis , Carcinosoma scorpionis and Erettopterus bilobus and S. stylops have been found associated with Nanahughmilleria pygmaea , Eusarcana salteri , Hardieopterus megalops , Erettopterus brodiei , E. gigas , Hughmilleria banksi , Eurypterus cephalaspis and Pterygotus ludensis . The living environment of
7038-478: The Permian. Roderick Murchison Sir Roderick Impey Murchison, 1st Baronet (19 February 1792 – 22 October 1871 ) was a Scottish geologist who served as director-general of the British Geological Survey from 1855 until his death in 1871. He is noted for investigating and describing the Silurian , Devonian and Permian systems. Murchison was born at Tarradale House , Muir of Ord , Ross-shire ,
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#17327932996907176-473: The Persons and Acorn study claimed that the fossil didn't show any signs of disarticulation, Lamsdell, Marshall, and Briggs showed this is likely not true. They argued that both tergite 8 and 10 clearly overlapped the other tergites in an unnatural way. Furthermore, they noted that the specimen was definitely a molt rather than a carcass, and argued that this meant that the pose the fossil was in did not represent
7314-494: The Pterygotidae, is noted for several unusually large species. Both Acutiramus , whose largest member A. bohemicus measured 2.1 meters (6.9 ft), and Pterygotus , whose largest species P. grandidentatus measured 1.75 meters (5.7 ft), were gigantic. Several different contributing factors to the large size of the pterygotids have been suggested, including courtship behaviour, predation and competition over environmental resources. Giant eurypterids were not limited to
7452-472: The Pterygotidae. The other Pterygotioid family, the Hughmilleriidae , has also been interpreted as the most closely related sister-taxon to the pterygotids. The discovery of Ciurcopterus , the most primitive known pterygotid, and studies revealing that Ciurcopterus combines features of Slimonia (the appendages are particularly similar) and of more derived pterygotids, revealed that the Slimonidae
7590-833: The Royal Geographical Society and the British Geological Survey." The chief geological investigation of the last decade of his life was devoted to the Highlands of Scotland, where he wrongly believed he had succeeded in showing that the vast masses of crystalline schists , previously supposed to be part of what used to be termed the Primitive formations, were really not older than the Silurian period, since underneath them lay beds of limestone and quartzite containing Lower Silurian ( Cambrian ) fossils . This started off what became known as
7728-517: The Silurian classification into other countries. In 1845, whilst visiting Carclew in Cornwall , he met several Cornish miners who were going to Australia. Believing that there might be gold there, he asked them to send back likely samples. They did this, and thus Murchison knew of the existence of gold in Australia before Edward Hargraves ' discovery. In 1857, Murchison was elected a member of
7866-598: The Stylonurina, this appendage takes the form of a long and slender walking leg, while in the Eurypterina, the leg is modified and broadened into a swimming paddle. Other than the swimming paddle, the legs of many eurypterines were far too small to do much more than allow them to crawl across the sea floor . In contrast, a number of stylonurines had elongated and powerful legs that might have allowed them to walk on land (similar to modern crabs ). A fossil trackway
8004-550: The abundance and diversity previously seen within the eurypterids. A major decline in diversity had already begun during the Early Devonian and eurypterids were rare in marine environments by the Late Devonian. During the Frasnian stage four families went extinct, and the later Famennian saw an additional five families going extinct. As marine groups were the most affected, the eurypterids were primarily impacted within
8142-399: The adjoining parts of Hampshire and Surrey , on which, aided by Fitton, he wrote his first scientific paper, read to the Geological Society of London in 1825. Turning his attention to Continental geology, he and Lyell explored the volcanic region of Auvergne , parts of southern France, northern Italy, Tyrol and Switzerland. A little later, with Sedgwick as his companion, Murchison attacked
8280-537: The ancient continent of Laurentia , and demersal (living on the seafloor ) and basal animals from the continents Avalonia and Gondwana. The Laurentian predators, classified in the family Megalograptidae (comprising the genera Echinognathus , Megalograptus and Pentecopterus ), are likely to represent the first truly successful eurypterid group, experiencing a small radiation during the Late Ordovician. Eurypterids were most diverse and abundant between
8418-442: The animal in question could possibly have measured just short of 2 meters (6.6 ft) in length. More robust than the pterygotids, this giant Hibbertopterus would possibly have rivalled the largest pterygotids in weight, if not surpassed them, and as such be among the heaviest arthropods. The two eurypterid suborders, Eurypterina and Stylonurina , are distinguished primarily by the morphology of their final pair of appendages. In
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#17327932996908556-454: The appendage via tracts, but these supposed tracts remain unpreserved in available fossil material. Type B appendages, assumed male, would have produced, stored and perhaps shaped spermatophore in a heart-shaped structure on the dorsal surface of the appendage. A broad genital opening would have allowed large amounts of spermatophore to be released at once. The long furca associated with type B appendages, perhaps capable of being lowered like
8694-983: The arcade on the west side of the central path. The crater Murchison on the Moon and at least fifteen geographical locations on Earth are named after him. These include: the Murchison Range, part of the Stauning Alps , and the Murchison Sound in Greenland ; Mount Murchison in Banff National Park , Canada; Mount Murchison in the Mountaineer Range , Antarctica; Mount Murchison, just west of Squamish, British Columbia , Canada; tiny Murchison Island in Haida Gwaii in
8832-418: The area in 1849 he was greeted by 15,000 locals who declared him the King of Siluria. A memorial tablet was installed on 3 November 2005 in front of School #9 in Perm in Russia. It consists of a stone base, irregular in form, about two metres long, and bearing a dark stone plate with the following inscription (in Russian): To Roderick Impey Murchison, Scottish geologist, explorer of Perm Krai , who gave to
8970-416: The attention of Roderick Murchison in 1851. S. acuminata remains the largest known species, with the largest specimens measuring up to 100 cm (39 in) in length. In 1899, an additional species, S. dubia , would be referred to the genus. This species was recovered from slightly earlier deposits (Llandovery age) in the Pentland Hills of Scotland and could be distinguished from S. acuminata by
9108-449: The body was very stiff, and that the flattened telson would likely have served as a rudder that would have allowed the animals to be agile and capable of quick turns when chasing after prey, contradicting previous hypotheses that the telson would have served a propulsive function. Whilst the postabdomen of Slimonia was likely similarly stiff and inflexible dorsally (up and down), Persons and Acorn claimed that their specimen suggested that it
9246-439: The body) of Slimonia is similar to that of the pterygotid eurypterids and is a feature that Slimonia and the pterygotids only share with some derived hibbertopterid eurypterids (where the feature convergently evolved). The pterygotid telson was in general slightly larger than that of Slimonia and was more slender. The telson spike of Slimonia was much longer than any seen in the Pterygotidae (constituting just over half of
9384-414: The body. The primary analogy used in previous studies has been horseshoe crabs, though their gill structure and that of eurypterids are remarkably different. In horseshoe crabs, the gills are more complex and composed of many lamellae (plates) which give a larger surface area used for gas exchange. In addition, the gill tract of eurypterids is proportionally much too small to support them if it is analogous to
9522-458: The case during the preceding Ordovician, eurypterine eurypterids experienced a rapid rise in diversity and number. In most Silurian fossil beds, eurypterine eurypterids account for 90% of all eurypterids present. Though some were likely already present by the Late Ordovician (simply missing from the fossil record so far), a vast majority of eurypterid groups are first recorded in strata of Silurian age. These include both stylonurine groups such as
9660-401: The clarity of vision, can be determined in arthropods by determining number of lenses in their compound eyes and the interommatidial angle (shortened as IOA and referring to the angle between the optical axes of the adjacent lenses). The IOA is especially important as it can be used to distinguish different ecological roles in arthropods, being low in modern active arthropod predators. Slimonia
9798-403: The closing public acts of Murchison's life was the founding of a chair of geology and mineralogy at the University of Edinburgh . Under his will there was established the Murchison Medal and a geological fund ( The Murchison Fund ) to be awarded annually by the council of the Geological Society in London. Murchison died in 1871 and is buried in Brompton Cemetery , London, near the north end of
9936-420: The coastlines and shallow inland seas of Euramerica. During the Late Silurian the pterygotid eurypterids, large and specialized forms with several new adaptations, such as large and flattened telsons capable of being used as rudders, and large and specialized chelicerae with enlarged pincers for handling (and potentially in some cases killing) prey appeared. Though the largest members of the family appeared in
10074-695: The cuticle) after which they underwent rapid and immediate growth. Some arthropods, such as insects and many crustaceans, undergo extreme changes over the course of maturing. Chelicerates, including eurypterids, are in general considered to be direct developers, undergoing no extreme changes after hatching (though extra body segments and extra limbs may be gained over the course of ontogeny in some lineages, such as xiphosurans and sea spiders ). Whether eurypterids were true direct developers (with hatchlings more or less being identical to adults) or hemianamorphic direct developers (with extra segments and limbs potentially being added during ontogeny) has been controversial in
10212-536: The difficult problem of the geological structure of the Alps . Their joint paper giving the results of their study is a classic in the literature of Alpine geology. Murchison was an opponent of Charles Darwin 's theory of evolution. He opposed the transmutation of species and supported successive creation . In 1831 he went to the England–Wales border , to attempt to discover whether the greywacke rocks underlying
10350-403: The enlarged cheliceral claws of the pterygotids and was smaller in size than the largest members of that group. Prey likely included jawless fish such as heterostracans and early osteostracans , which Slimonia would have seized with its frontal appendages. Slimonia traversed its living environment on spindly legs or through using its swimming appendages. The lungs of the genus were located on
10488-409: The eurypterine suborder, had already been established at this point during the Middle Ordovician. The earliest known stylonurine eurypterid, Brachyopterus , is also Middle Ordovician in age. The presence of members of both suborders indicates that primitive stem-eurypterids would have preceded them, though these are so far unknown in the fossil record. The presence of several eurypterid clades during
10626-411: The eurypterine suborder. Only one group of stylonurines (the family Parastylonuridae ) went extinct in the Early Devonian. Only two families of eurypterines survived into the Late Devonian at all ( Adelophthalmidae and Waeringopteridae). The eurypterines experienced their most major declines in the Early Devonian, during which over 50% of their diversity was lost in just 10 million years. Stylonurines, on
10764-515: The eurypterine swimming paddles varied from group to group. In the Eurypteroidea , the paddles were similar in shape to oars. The condition of the joints in their appendages ensured their paddles could only be moved in near-horizontal planes, not upwards or downwards. Some other groups, such as the Pterygotioidea, would not have possessed this condition and were probably able to swim faster. Most eurypterines are generally agreed to have utilized
10902-454: The family Pterygotidae. An isolated 12.7 centimeters (5.0 in) long fossil metastoma of the carcinosomatoid eurypterid Carcinosoma punctatum indicates the animal would have reached a length of 2.2 meters (7.2 ft) in life, rivalling the pterygotids in size. Another giant was Pentecopterus decorahensis , a primitive carcinosomatoid, which is estimated to have reached lengths of 1.7 meters (5.6 ft). Typical of large eurypterids
11040-470: The first to hold these offices. Official routine now occupied much of his time, but he found opportunity for the Highland researches just alluded to, and also for preparing successive editions of his work Siluria (1854, ed. 5, 1872), which was meant to present the main features of the original Silurian System together with a digest of subsequent discoveries, particularly of those that showed the extension of
11178-476: The found tracks each being about 7.6 centimeters (3.0 in) in diameter. Other eurypterid ichnogenera include Merostomichnites (though it is likely that many specimens actually represent trackways of crustaceans) and Arcuites (which preserves grooves made by the swimming appendages). In eurypterids, the respiratory organs were located on the ventral body wall (the underside of the opisthosoma). Blattfüsse , evolved from opisthosomal appendages, covered
11316-582: The gathering of food. In some groups, these spiny appendages became heavily specialized. In some eurypterids in the Carcinosomatoidea, forward-facing appendages were large and possessed enormously elongated spines (as in Mixopterus and Megalograptus ). In derived members of the Pterygotioidea, the appendages were completely without spines, but had specialized claws instead. Other eurypterids, lacking these specialized appendages, likely fed in
11454-656: The genus Strabops from the Cambrian of Missouri , are now classified as aglaspidids or strabopids . The aglaspidids, once seen as primitive chelicerates, are now seen as a group more closely related to trilobites. The fossil record of Ordovician eurypterids is quite poor. The majority of eurypterids once reportedly known from the Ordovician have since proven to be misidentifications or pseudofossils . Today only 11 species can be confidently identified as representing Ordovician eurypterids. These taxa fall into two distinct ecological categories; large and active predators from
11592-525: The genus (of which the most common is the type species, E. remipes ) account for more than 90% (perhaps as many as 95%) of all known fossil eurypterid specimens. Despite their vast number, Eurypterus are only known from a relatively short temporal range, first appearing during the Late Llandovery epoch (around 432 million years ago) and being extinct by the end of the Pridoli epoch. Eurypterus
11730-429: The giant millipede Arthropleura , and are possibly vital for the evolution of giant size in arthropods. In addition to the lightweight giant eurypterids, some deep-bodied forms in the family Hibbertopteridae were also very large. A carapace from the Carboniferous of Scotland referred to the species Hibbertoperus scouleri measures 65 cm (26 in) wide. As Hibbertopterus was very wide compared to its length,
11868-412: The gills of other groups. To be functional gills, they would have to have been highly efficient and would have required a highly efficient circulatory system. It is considered unlikely, however, that these factors would be enough to explain the large discrepancy between gill tract size and body size. It has been suggested instead that the "gill tract" was an organ for breathing air, perhaps actually being
12006-429: The highly fragmentary nature of the known fossils make a precise identification difficult and problematic. Only one specimen, the anterior part of a carapace with the compound eyes placed on the margin, is known and though it does resemble Slimonia , it could also potentially be referred to Hughmilleria or even represent the carapace of Salteropterus abbreviatus (a closely related slimonid eurypterid known only from
12144-580: The invaginations leading to asphyxiation . Furthermore, most eurypterids would have been aquatic their entire lives. No matter how much time was spent on land, organs for respiration in underwater environments must have been present. True gills, expected to have been located within the branchial chamber within the Blattfüssen , remain unknown in eurypterids. Like all arthropods, eurypterids matured and grew through static developmental stages referred to as instars . These instars were punctuated by periods during which eurypterids went through ecdysis (molting of
12282-491: The larger sizes of adults mean a higher drag coefficient , using this type of propulsion is more energy-efficient. Some eurypterines, such as Mixopterus (as inferred from attributed fossil trackways), were not necessarily good swimmers. It likely kept mostly to the bottom, using its swimming paddles for occasional bursts of movements vertically, with the fourth and fifth pairs of appendages positioned backwards to produce minor movement forwards. While walking, it probably used
12420-505: The largest known arthropod ever to have lived, is Jaekelopterus rhenaniae . A chelicera from the Emsian Klerf Formation of Willwerath, Germany measured 36.4 centimeters (14.3 in) in length, but is missing a quarter of its length, suggesting that the full chelicera would have been 45.5 centimeters (17.9 in) long. If the proportions between body length and chelicerae match those of its closest relatives, where
12558-537: The largest known arthropods to ever live. Slimonia can be distinguished from other members of its family, the Slimonidae , by a variety of characteristics. The prosoma (head) is quadrate (square-shaped) in shape and had small compound eyes on the frontal corners. The bodies were large and cordate (heart-shaped), with a narrow postabdomen and a telson with a strongly expanded anterior half. The chelicerae (frontal appendages) were small in comparison to those of
12696-497: The last ever radiation within the eurypterids, which gave rise to several new forms capable of "sweep-feeding" (raking through the substrate in search of prey). Only three eurypterid families—Adelophthalmidae, Hibbertopteridae and Mycteroptidae—survived the extinction event in its entirety. It was assumed that these were all freshwater animals, which would have rendered the eurypterids extinct in marine environments, and with marine eurypterid predators gone, sarcopterygians , such as
12834-837: The last period of the Paleozoic era the name of Permian. The decision to perpetuate the explorer's name was accepted by the school administration and pupils in connection with a discussion to establish in Perm a pillar or an arch devoted to Roderick Murchison. In 2009, the Ural-Scottish Society erected a memorial to Murchison on the banks of the Chusovaya River . There is a commemorative blue plaque on his residence at 21 Galgate in Barnard Castle (County Durham). A fictionalised version of Murchison appears in
12972-433: The limbs tended to get larger the farther back they were. In the Eurypterina suborder , the larger of the two eurypterid suborders, the sixth pair of appendages was also modified into a swimming paddle to aid in traversing aquatic environments. The opisthosoma comprised 12 segments and the telson , the posteriormost division of the body, which in most species took the form of a blade-like shape. In some lineages, notably
13110-441: The more elongated telson (also not as broad in the parts furthest back), thinner telson spike and a slightly different, tapering, body shape that tapers evenly the whole way instead of suddenly narrowing near the seventh segment as in S. acuminata . The type specimen of S. dubia is a badly preserved carapace, with fragments of various degrees of completion of the first eleven segments found associated. Despite its fragmentary nature,
13248-494: The mouth. In one lineage, the Pterygotidae , the chelicerae were large and long, with strong, well-developed teeth on specialised chelae (claws). The subsequent pairs of appendages, numbers II to VI, possessed gnathobases (or "tooth-plates") on the coxae (limb segments) used for feeding. These appendages were generally walking legs that were cylindrical in shape and were covered in spines in some species. In most lineages,
13386-712: The opisthosoma, these structures formed plate-like structures termed Blattfüsse ( lit. ' leaf-feet ' in German). These created a branchial chamber (gill tract) between preceding Blattfüsse and the ventral surface of the opisthosoma itself, which contained the respiratory organs. The second to sixth opisthosomal segments also contained oval or triangular organs that have been interpreted as organs that aid in respiration. These organs, termed Kiemenplatten or "gill tracts", would potentially have aided eurypterids to breathe air above water, while Blattfüssen , similar to organs in modern horseshoe crabs , would cover
13524-480: The other eurypterid Drepanopterus abonensis , a sweep-feeder that used the marginal rim to search the substrate of its living environment for prey. If the pustules of S. acuminata had setae, these pustules may have functioned as tactile and sensory organs used for locating and identifying prey, together with the pedipalps (the gracile second pair of appendages, behind the chelicerae). Eurypterid Eurypterids , often informally called sea scorpions , are
13662-424: The other hand, persisted through the period with more or less consistent diversity and abundance but were affected during the Late Devonian, when many of the older groups were replaced by new forms in the families Mycteroptidae and Hibbertopteridae. It is possible that the catastrophic extinction patterns seen in the eurypterine suborder were related to the emergence of more derived fish. Eurypterine decline began at
13800-552: The parts that serve for underwater respiration . The appendages of opisthosomal segments 1 and 2 (the seventh and eighth segments overall) were fused into a structure termed the genital operculum, occupying most of the underside of the opisthosomal segment 2. Near the anterior margin of this structure, the genital appendage (also called the Zipfel or the median abdominal appendage) protruded. This appendage, often preserved very prominently, has consistently been interpreted as part of
13938-433: The past. Hemianamorphic direct development has been observed in many arthropod groups, such as trilobites , megacheirans , basal crustaceans and basal myriapods . True direct development has on occasion been referred to as a trait unique to arachnids . There have been few studies on eurypterid ontogeny as there is a general lack of specimens in the fossil record that can confidently be stated to represent juveniles. It
14076-434: The point when jawless fish first became more developed and coincides with the emergence of placoderms (armored fish) in both North America and Europe. Stylonurines of the surviving hibbertopterid and mycteroptid families completely avoided competition with fish by evolving towards a new and distinct ecological niche. These families experienced a radiation and diversification through the Late Devonian and Early Carboniferous,
14214-570: The pterygotids and the walking legs had denticles, but no spines. Genital appendages were long and narrow in both males and females. The type species of Slimonia , S. acuminata , was first described as a species of Pterygotus , " Pterygotus acuminata " ( acuminata being Latin for "sharp" or "tapering"), by John William Salter in 1856, based on fossils recovered from deposits of Llandovery - Wenlock (Early to Middle Silurian) age in Lesmahagow , Scotland . That same year David Page erected
14352-444: The pterygotids differed from genus to genus, with some (such as Pterygotus ) being found in estuaries, while other (such as Jaekelopterus ) were found in freshwater environments; Slimonia has been found in environments which appear to have been intertidal to marine, Patrick Burn Formation for example is estimated to be non-marine or marginal marine or just marine environment. Slimonia likely preyed on smaller fish, as it lacked
14490-485: The quadrangular (square) shape of the carapace and the eyes placed at its corners allowed zoologist and paleontologist Malcolm Laurie to place it within Slimonia when describing it in 1899. The size of the carapace suggests that the species would have grown to 12 cm (5 in) in length. Another species, S. stylops , was first considered a species of Pterygotus when described by John William Salter in 1859, and
14628-452: The ratio between claw size and body length is relatively consistent, the specimen of Jaekelopterus that possessed the chelicera in question would have measured between 233 and 259 centimeters (7.64 and 8.50 ft), an average 2.5 meters (8.2 ft), in length. With the chelicerae extended, another meter (3.28 ft) would be added to this length. This estimate exceeds the maximum body size of all other known giant arthropods by almost half
14766-445: The reproduction and sexual dimorphism of eurypterids is difficult, as they are only known from fossilized shells and carapaces. In some cases, there might not be enough apparent differences to separate the sexes based on morphology alone. Sometimes two sexes of the same species have been interpreted as two different species, as was the case with two species of Drepanopterus ( D. bembycoides and D. lobatus ). The eurypterid prosoma
14904-458: The reproductive system and occurs in two recognized types, assumed to correspond to male and female. Eurypterids were highly variable in size, depending on factors such as lifestyle, living environment and taxonomic affinity . Sizes around 100 centimeters (3.3 ft) are common in most eurypterid groups. The smallest eurypterid, Alkenopterus burglahrensis , measured just 2.03 centimeters (0.80 in) in length. The largest eurypterid, and
15042-435: The rest of the former supercontinent Gondwana , the discoveries of trackways both predate and outnumber eurypterid body fossils. Eurypterid trackways have been referred to several ichnogenera, most notably Palmichnium (defined as a series of four tracks often with an associated drag mark in the mid-line), wherein the holotype of the ichnospecies P. kosinkiorum preserves the largest eurypterid footprints known to date with
15180-682: The retreat to Corunna and the final battle there. After eight years of service Murchison left the army and married Charlotte Hugonin (1788–1869), the only daughter of General Hugonin of Nursted House, Hampshire. Murchison and his wife spent two years in mainland Europe, particularly in Italy. They then settled in Barnard Castle , County Durham, England, in 1818, where Murchison made the acquaintance of Sir Humphry Davy . Davy urged Murchison to turn his energy to science, after hearing that he wasted his time riding to hounds and shooting. With encouragement from his wife Charlotte, Murchison became fascinated by
15318-405: The same genera. The primary function of the long, assumed female, type A appendages was likely to take up spermatophore from the substrate into the reproductive tract rather than to serve as an ovipositor, as arthropod ovipositors are generally longer than eurypterid type A appendages. By rotating the sides of the operculum, it would have been possible to lower the appendage from the body. Due to
15456-909: The same province; the Murchison Falls in Uganda; the Murchison River in Western Australia. Murchison has two other rivers named after him in Western Australia: the Roderick River and the Impey River , both tributaries of the Murchison. The town of Murchison in the Tasman Region of New Zealand's South Island was also named after him. Murchison Road is one of the streets in east London, and there
15594-413: The short stride length indicates that Hibbertopterus crawled with an exceptionally slow speed, at least on land. The large telson was dragged along the ground and left a large central groove behind the animal. Slopes in the tracks at random intervals suggest that the motion was jerky. The gait of smaller stylonurines, such as Parastylonurus , was probably faster and more precise. The functionality of
15732-479: The smallest eurypterid, Alkenopterus , was only 2.03 centimeters (0.80 in) long. Eurypterid fossils have been recovered from every continent. A majority of fossils are from fossil sites in North America and Europe because the group lived primarily in the waters around and within the ancient supercontinent of Euramerica . Only a handful of eurypterid groups spread beyond the confines of Euramerica and
15870-663: The son of Barbara and Kenneth Murchison. His wealthy father died in 1796, when Roderick was four years old, and he was sent to Durham School three years later and then to the Royal Military College, Great Marlow , to be trained for the army. In 1808 he landed with Wellesley in Portugal, and was present at the actions of Roliça and Vimeiro in the Peninsular War as an ensign in the 36th Regt of Foot . Subsequently, under Sir John Moore , he took part in
16008-441: The species Lanarkopterus dolichoschelus from the Ordovician of Ohio contain fragments of jawless fish and fragments of smaller specimens of Lanarkopterus itself. Though apex predatory roles would have been limited to the very largest eurypterids, smaller eurypterids were likely formidable predators in their own right just like their larger relatives. As in many other entirely extinct groups, understanding and researching
16146-427: The spongy structure of the eurypterid gill tracts. It is possible the two organs functioned in the same way. Some researchers have suggested that eurypterids may have been adapted to an amphibious lifestyle, using the full gill tract structure as gills and the invaginations within it as pseudotrachea. This mode of life may not have been physiologically possible, however, since water pressure would have forced water into
16284-498: The structure. Though the Kiemenplatte is referred to as a "gill tract", it may not necessarily have functioned as actual gills. In other animals, gills are used for oxygen uptake from water and are outgrowths of the body wall. Despite eurypterids clearly being primarily aquatic animals that almost certainly evolved underwater (some eurypterids, such as the pterygotids, would even have been physically unable to walk on land), it
16422-531: The telson and metastoma , a large plate part of the abdomen). The fossils were recovered from deposits of Pridoli (Late Silurian) age in Herefordshire , England and suggest that the species grew to 12 cm (5 in) in length. Due to its problematic nature, S. stylops is seen as a nomen dubium by modern researchers. In 1973, another species of Slimonia was named by Kjellesvig-Waering based on one single fossil recovered by Eduardo Rodriguez from
16560-471: The total telson length) however, serrated and ending in a fine point. The largest species of Slimonia , S. acuminata , reached a maximum length of 100 cm (39 in) whilst the smallest, S. dubia , grew to 12 cm (5 in) in length. Though 100 cm is large for a predatory arthropod, Slimonia would be exceeded in length by later and more derived (more "advanced") members of the closely related pterygotid family of eurypterids, which would become
16698-468: The type A appendage is divided into three but the type B appendage into only two. Such division of the genital appendage is common in eurypterids, but the number is not universal; for instance, the appendages of both types in the family Pterygotidae are undivided. The type A appendage is also armed with two curved spines called furca (lit. 'fork' in Latin). The presence of furca in the type B appendage
16836-414: The type A appendage, could have been used to detect whether a substrate was suitable for spermatophore deposition. Until 1882 no eurypterids were known from before the Silurian. Contemporary discoveries since the 1880s have expanded the knowledge of early eurypterids from the Ordovician period. The earliest eurypterids known today, the megalograptid Pentecopterus , date from the Darriwilian stage of
16974-400: The underside and created a gill chamber where the "gill tracts" were located. Depending on the species, the eurypterid gill tract was either triangular or oval in shape and was possibly raised into a cushion-like state. The surface of this gill tract bore several spinules (small spines), which resulted in an enlarged surface area. It was composed of spongy tissue due to many invaginations in
17112-660: The underside of the body in a series of folds. Like many eurypterid species, Slimonia acuminata requires a modern re-description to properly establish defining traits and characteristics. Some traits that appear to be unique to S. acuminata have been described based on specimens housed at the Doncaster Museum and Art Gallery , including rows of pustules (bulges) along the marginal rim of the body and appendages. In some arthropods, pustules serve as attachment points of setae (bristle- or hair-like structures with sensory functions). Similar pustule rows have been discovered in
17250-429: The way different plates overlay at its location, the appendage would have been impossible to move without muscular contractions moving around the operculum. It would have been kept in place when not it use. The furca on the type A appendages may have aided in breaking open the spermatophore to release the free sperm inside for uptake. The "horn organs," possibly spermathecae, are thought to have been connected directly to
17388-489: The young science of geology and joined the Geological Society of London , soon becoming one of its most active members. His colleagues there included Adam Sedgwick , William Conybeare , William Buckland , William Fitton , Charles Lyell and Charles Darwin . Exploring with his wife, Murchison studied the geology of the south of England, devoting special attention to the rocks of the north-west of Sussex and
17526-400: Was also restricted to the continent Euramerica (composed of the equatorial continents Avalonia, Baltica and Laurentia), which had been completely colonized by the genus during its merging and was unable to cross the vast expanses of ocean separating this continent from other parts of the world, such as the southern supercontinent Gondwana. As such, Eurypterus was limited geographically to
17664-496: Was covered by a carapace (sometimes called the "prosomal shield") on which both compound eyes and the ocelli (simple eye-like sensory organs) were located. The prosoma also bore six pairs of appendages which are usually referred to as appendage pairs I to VI. The first pair of appendages, the only pair placed before the mouth, is called the chelicerae ( homologous to the fangs of spiders). They were equipped with small pincers used to manipulate food fragments and push them into
17802-670: Was devoted to the affairs of the Royal Geographical Society , of which he was in 1830 one of the founders, and he was president 1843–1845, 1851–1853, 1856–1859 and 1862–1871. He served on the Royal Commission on the British Museum (1847–1849). Murchison also announced the Permian system to geology in 1841, based on explorations in Perm Krai undertaken with Édouard de Verneuil. Murchison
17940-505: Was discovered in Carboniferous-aged fossil deposits of Scotland in 2005. It was attributed to the stylonurine eurypterid Hibbertopterus due to a matching size (the trackmaker was estimated to have been about 1.6 meters (5.2 ft) long) and inferred leg anatomy. It is the largest terrestrial trackway—measuring 6 meters (20 ft) long and averaging 95 centimeters (3.12 ft) in width—made by an arthropod found thus far. It
18078-536: Was hardly a foreign scientific society of note without his name among its honorary members. The French Academy of Sciences awarded him the prix Cuvier, and elected him one of its eight foreign members in succession to Michael Faraday . In 1855 he was elected a foreign member of the Royal Swedish Academy of Sciences and in 1871 awarded the Founders' Medal of the Royal Geographical Society. One of
18216-421: Was highly flexible laterally (side to side). As such, they theorised that the tail may have been used as a weapon. The telson spine, serrated along the sides and exceeding the flattened telson in length, ends in a sharp tip, and they proposed that it could have been capable of piercing prey. However, the Persons and Acorn theory was challenged in 2018 by James Lamsdell, David Marshall, and Derek Briggs. Even though
18354-452: Was more or less parallel and similar to that of extinct and extant xiphosurans, with the largest exception being that eurypterids hatched with a full set of appendages and opisthosomal segments. Eurypterids were thus not hemianamorphic direct developers, but true direct developers like modern arachnids. The most frequently observed change occurring through ontogeny (except for some genera, such as Eurypterus , which appear to have been static)
18492-434: Was no apparent disarticulation in the metasoma, it was likely that the articulation seen in the postabdominal segments (which is also seen in some other eurypterid fossils, such as of Eurypterus and Alkenopterus ) would have been possible in life. Biomechanical studies on the telsons and postabdominal segments of eurypterids closely related to Slimonia , particularly those of the family Pterygotidae , had revealed that
18630-577: Was responsible for establishing much of the international prestige of British geology, and he viewed the spread of his stratigraphic systems on maps around the world "as a scientific form of imperial expansion". He frequently described geological excursions (such those he made abroad) as "invasions" or "conquests" and enjoyed being dubbed the "King of Siluria". According to the scholar Robert A. Stafford, "Murchinson's tendencies towards militarism , imperialism , and megalomania ran through his career and finally found full expression his simultaneous leadership of
18768-518: Was used as an ovipositor (used to deposit eggs). The different types of genital appendages are not necessarily the only feature that distinguishes between the sexes of eurypterids. Depending on the genus and species in question, other features such as size, the amount of ornamentation and the proportional width of the body can be the result of sexual dimorphism. In general, eurypterids with type B appendages (males) appear to have been proportionally wider than eurypterids with type A appendages (females) of
18906-545: Was very similar to the basal pterygotid Erettopterus in terms of visual acuity, with the number of lenses being comparable to those of Pterygotus and Jaekelopterus and possessing an IOA between 2 and 3 (which is higher than the IOA of Pterygotus and Jaekelopterus , suggesting that the visual acuity of Slimonia was good, but not as good as in the derived pterygotids). Fossils of Slimonia have been recovered in deposits home to diverse eurypterid faunas. Telychian deposits in
19044-481: Was wider and shorter than in the type species. This species was the third Silurian eurypterid in the Southern Hemisphere to be described, the other two coming from Australia . The fossil suggest a total body length of 20 centimetres (7.9 in). Slimonia is classified as part of the eurypterid family Slimonidae , within the superfamily Pterygotioidea . Historically Slimonia was first considered
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