127-434: Carcinosomatoidea is an extinct superfamily of eurypterids , an extinct group of chelicerate arthropods commonly known as "sea scorpions". It is one of the superfamilies classified as part of the suborder Eurypterina . Some carcinosomatoid genera have been suggested to have been fully marine as opposed to living in near-shore brackish or hypersaline environments. The majority of carcinosomatoid taxa are known from
254-578: 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
381-509: 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 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,
508-408: 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
635-597: A body segment) from Lower Devonian deposits of the Beartooth Butte Formation in Wyoming . The species name howelli honours Dr. Benjamin Howell of Princeton University, who loaned the fossil specimens examined in the description to Kjellesvig-Waering and Størmer. This species was assigned to Jaekelopterus as Jaekelopterus howelli by Norwegian palaeontologist O. Erik Tetlie in 2007. Jaekelopterus
762-724: A curved free ramus and denticles of different lengths and sizes, all adaptations that correspond to strong puncturing and grasping abilities in extant scorpions and crustaceans. Some puncture wounds on fossils of the poraspid agnathan fish Lechriaspis patula from the Devonian of Utah were likely caused by Jaekelopterus howelli . The latest research indicates that Jaekelopterus was an active and visual predator. Fully grown Jaekelopterus would have been apex predators in their environments and likely preyed upon smaller arthropods (including resorting to cannibalism ) and early vertebrates. A powerful and active predator, Jaekelopterus
889-461: A dual respiratory system was present, which would have allowed for short periods of time in terrestrial environments. The name Eurypterida comes from 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
1016-894: A frontally overlapping visual field, i.e. stereoscopic vision , typical of predatory animals. Structurally, eurypterid eyes were almost identical to the eyes of horseshoe crabs. The square-like pattern of the receptor cells in the compound eyes of Jaekelopterus is also similar, but not identical, to the pattern in horseshoe crabs, suggesting a specialised visual system. The photoreceptors are unusually large in Jaekelopterus . At around 70 μm, they are far larger than those of humans (1-2 μm) and most arthropods (also 1-2 μm) but they match those of modern horseshoe crabs in size. The unique eyes of modern horseshoe crabs are highly distinct from eyes of other modern arthropods and allow increased edge-perception and enhance contrasts, important for animals in low and scattered light conditions. As
1143-742: 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
1270-416: 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
1397-425: 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 ,
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#17327986400591524-450: A misinterpretation by Størmer in 1936, the genital appendage of Jaekelopterus in fact being unsegmented like that of Pterygotus . As such, the family Jaekelopteridae has subsequently been rejected and treated as synonymous with the family Pterygotidae. Another species of Pterygotus , P. howelli , was named by American palaeontologist Erik Kjellesvig-Waering and Størmer in 1952 based on a fossil telson and tergite (the dorsal part of
1651-474: A quiet, shallow estuarine environment. This species has been found together with two other eurypterid species: Dorfopterus angusticollis and Strobilopterus princetonii . The fossil sites yielding J. rhenaniae in the Rhineland have also been interpreted as having been part of a shallow aquatic environment with brackish to fresh water . The chelicerae of Jaekelopterus are enlarged, robust and have
1778-471: 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
1905-474: A separate genus based on an observed difference in the genital appendage. Though this feature has since proved to be a misidentification, other features distinguishing the genus from its relatives have been identified, including a telson with a triangular shape and a different inclination of the denticles of the claws. The chelicerae and compound eyes of Jaekelopterus indicate it was active and powerful with high visual acuity , most likely an apex predator in
2032-414: A total maximum body length of only 180 centimetres (5.9 ft). Positive allometry has not been demonstrated in eurypterid chelicerae as a whole in any other eurypterid genus, including in the closest relatives of Jaekelopterus . There are also some undescribed specimens of J. rhenaniae similar in proportions to the large chelicera, including another claw found in the same strata as the original find. In
2159-559: A triangular shape, as in J. rhenaniae . Its serrated telson margin and the massive elongation of the second intermediate denticle clearly distinguishes it from J. rhenaniae . Furthermore, the type A genital appendage is not bifurcated at its end. J. howelli is much smaller than J. rhenaniae , reaching 80 centimetres (2.6 ft) in length. Jaekelopterus was originally described as a species of Pterygotus , P. rhenaniae , in 1914 by German palaeontologist Otto Jaekel based on an isolated fossil pretelson (the segment directly preceding
2286-553: 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
2413-495: 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
2540-529: 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
2667-673: Is classified within the family Pterygotidae in the superfamily Pterygotioidea . Jaekelopterus is similar to Pterygotus , virtually only distinct in features of its genital appendage and potentially its telson. The close similarities between the two genera have prompted some researchers to question if the pterygotids are oversplit on the generic level. Based on some similarities in the genital appendage, American palaeontologists James C. Lamsdell and David A. Legg suggested in 2010 that Jaekelopterus , Pterygotus and even Acutiramus could be synonyms of each other. Though differences have been noted in chelicerae, these structures were questioned as
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#17327986400592794-489: 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
2921-487: 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,
3048-469: Is missing a quarter of its length, suggesting that the full chelicera would have been 45.5 centimetres (17.9 in) long. If the ratio of body length to chelicera length matches those of other giant pterygotids , such as Acutiramus and Pterygotus , where the ratio between claw size and body length is relatively consistent, the organism that possessed the chelicera would have measured between 233 and 259 centimetres (7.64 and 8.50 ft) in length. With
3175-521: 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
3302-408: Is more than twice the length of any principal denticle. Though such growth in the denticles of pterygotids has been described in other genera, the massive elongation of the second intermediate denticle through ontogeny is unique to Jaekelopterus , particularly to J. howelli . The metastoma of Jaekelopterus also altered its dimensions as the animal matured. In J. rhenaniae , the relative width of
3429-544: 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
3556-638: 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
3683-560: Is required to resolve whether the genera are synonyms of each other. The cladogram below is based on the nine best-known pterygotid species and two outgroup taxa ( Slimonia acuminata and Hughmilleria socialis ). Jaekelopterus had previously been classified as a basal sister taxon to the rest of the Pterygotidae since its description as a separate genus by Waterston in 1964 due to its supposedly segmented genital appendages (fused and undivided in other pterygotids), but restudy of
3810-439: 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
3937-816: 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
Carcinosomatoidea - Misplaced Pages Continue
4064-418: 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
4191-686: The Early Ordovician or Late Cambrian period. With approximately 250 species, the Eurypterida is the most diverse Paleozoic chelicerate order. Following their appearance during 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
4318-622: The Eurypteroidea . This eurypterid -related article is a stub . You can help Misplaced Pages by expanding it . 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 likely to have appeared first either during
4445-532: 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
4572-536: 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, 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
4699-433: The metastoma (a large plate that is part of the abdomen) and telson discovered by German palaeontologist Walter R. Gross near Overath , Germany, Norwegian palaeontologist Leif Størmer provided a more comprehensive and detailed description of the species in 1936. Størmer interpreted the genital appendages as being segmented, distinct from other species of Pterygotus . British palaeontologist Charles D. Waterston erected
4826-668: The paleocontinents of Laurentia , Baltica and Avalonia . Isolated and fragmentary fossils from the Late Silurian of Vietnam and the Czech Republic show that the terranes of Annamia and Perunica were within the geographical range of the carcinosomatoids. Only a few basal carcinosomatoids (e.g. Carcinosoma and Paracarcinosoma ) have been found in deeper waters whilst the more derived forms, such as Mixopterus and Lanarkopterus have not. Basal carcinosomatoids ( Carcinosomatidae ) are likely responsible for
4953-442: 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
5080-405: 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
5207-678: The telson , the posteriormost division of the body, which in most species took the form of a blade-like shape. In some lineages, notably 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
Carcinosomatoidea - Misplaced Pages Continue
5334-539: 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
5461-825: 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
5588-602: 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
5715-658: 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
5842-573: The Permian. Jaekelopterus Jaekelopterus is a genus of predatory eurypterid , a group of extinct aquatic arthropods . Fossils of Jaekelopterus have been discovered in deposits of Early Devonian age, from the Pragian and Emsian stages. There are two known species: the type species J. rhenaniae from brackish to fresh water strata in the Rhineland , and J. howelli from estuarine strata in Wyoming . The generic name combines
5969-494: 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
6096-598: 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
6223-550: 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
6350-521: The actual properties of the exoskeleton restrict the size of arthropods. Other than the robust and heavily sclerotised claws, most of the preserved large body segments of the pterygotids are thin and unmineralised. Even tergites and sternites (the plates that form the surfaces of the abdominal segments) are generally preserved as paper-thin compressions, suggesting that pterygotids were very lightweight in construction. Similar lightweight adaptations can be observed in other Paleozoic giant arthropods, such as
6477-537: 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
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#17327986400596604-442: 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
6731-454: 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
6858-413: The basis of generic distinctions in eurypterids by Charles D. Waterston in 1964 since their morphology is dependent on lifestyle and varies throughout ontogeny (the development of the organism following its birth). Whilst telson morphology can be used to distinguish genera in eurypterids, Lamsdell and Legg noted that the triangular telson of Jaekelopterus might still fall within the morphological range of
6985-414: 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
7112-458: 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
7239-466: The chelicerae extended, another metre would be added to this length. This estimate exceeds the maximum body size of all other known giant arthropods by almost half a metre even if the extended chelicerae are not included. Jaekelopterus is similar to other pterygotid eurypterids in its overall morphology , distinguished by its triangular telson (the hindmost segment of its body) and inclined principal denticles on its cheliceral rami (the moving part of
7366-436: The chelicerae in enough detail to allow for study of the denticles. Two of these chelicerae were assumed to come from juveniles and two were assumed to be from adults. The morphology of the chelicerae is similar across all ages, with the same arrangement and number of denticles, but there were also some noticeable differences. Particularly, the principal denticles grew in size relative to the intermediate denticles, being 1.5 times
7493-404: The chelicerae of other eurypterid groups. Another feature distinguishing the group from other eurypterid groups is their flattened and expanded telsons, likely used as rudders when swimming. J. howelli , known from over 30 specimens, has an almost identical pattern of denticulation on the chelicerae as J. rhenaniae and also preserves a flattened posterior margin of the telson, which results in
7620-407: The claws). The pterygotids, a group of highly derived ("advanced") eurypterids, differ from other groups in several features, especially in the chelicerae and the telson. The chelicerae of the Pterygotidae are enlarged and robust, clearly adapted for active prey capture, with chelae (pincers) more similar to the claws of some modern crustaceans , with well-developed teeth on the claws, relative to
7747-420: 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
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#17327986400597874-695: 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
8001-422: The deep-bodied walking forms in the Hibbertopteridae , such as the almost 2-metre-long Hibbertopterus , may have rivalled the pterygotids and other giant arthropods in weight, if not surpassed them. American palaeontologist Alexander Kaiser and South African palaeontologist Jaco Klok suggested in 2008 that the massive size estimates for Jaekelopterus are exaggerated, noting that the size estimates assume that
8128-584: The ecosystems of Early Devonian Euramerica . Although eurypterids such as Jaekelopterus are often called "sea scorpions", the strata in which Jaekelopterus fossils have been found suggest that it lived in fresh water environments. Jaekelopterus is the largest known eurypterid and the largest known arthropod to have ever existed. This was determined based on a chelicera (claw) from the Emsian Klerf Formation of Willwerath, Germany , that measures 36.4 centimetres (14.3 in) long, but
8255-409: 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
8382-411: 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
8509-453: 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
8636-413: The eyes of Jaekelopterus were very similar, it too likely had the same adaptations. With its highly specialised eyes, Jaekelopterus was very well adapted to its predatory lifestyle. The morphology and body construction of Jaekelopterus and other eurypterids in the Pterygotidae suggests they were adapted to a completely aquatic lifestyle. Braddy, Poschmann and Tetlie considered in a 2007 study that it
8763-454: 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
8890-538: The fossil remains in Vietnam and the Czech Republic and may have had a distribution similar to the cosmopolitan distribution of the pterygotioids , though they were not as common nor as successful. The Carcinosomatoidea have a poorly resolved internal phylogeny, though can be easily recognised by scorpion -like appearance and heavily spinose appendages. Numerous characteristics support a close relationship to
9017-476: 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
9144-426: The full complement of adult opisthosomal appendages (appendages attached to the opisthosoma , the posterior segments of the body), but extant spiders are fully direct developers. Studies of fossil specimens of Strobilopterus and Jaekelopterus suggest that the ontogeny of eurypterids broadly parallelled that of modern horseshoe crabs, but that eurypterids (like arachnids) were true direct developers, hatching with
9271-582: 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
9398-656: 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
9525-473: The genus Jaekelopterus in 1964 to accommodate Pterygotus rhenaniae , which he considered sufficiently distinct from other species of Pterygotus to warrant its own genus, primarily due to the abdominal appendages of Jaekelopterus being segmented as opposed to those of Pterygotus . Waterston diagnosed Jaekelopterus as a pterygotid with segmented genital appendages, a trapezoid prosoma , narrow and long chelicerae with terminal teeth almost at right angles to
9652-525: 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
9779-429: 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,
9906-405: The giant millipede-like Arthropleura , and it has been suggested to be vital for the evolution of giant arthropod sizes. A lightweight build decreases the influence of factors that restrict body size. Despite being the largest arthropods, the lightweight build of Jaekelopterus and other giant pterygotid eurypterids meant they likely were not the heaviest. Other giant eurypterids, particularly
10033-412: 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
10160-587: 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 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
10287-432: 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 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
10414-580: 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
10541-491: 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
10668-431: 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
10795-523: 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; 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
10922-402: The largest known eurypterids, such as Pterygotus and Acutiramus . Several factors have been suggested that might have contributed to the unprecedented large size of Jaekelopterus , its relatives and other large Paleozoic invertebrates, such as predation, courtship behaviour, competition and environmental resources. Factors such as respiration, the energy costs of moulting , locomotion and
11049-497: 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
11176-470: The low IOA and many lenses in their compound eyes. Further studies on the compound eyes of fossilised specimens of J. rhenaniae , including a large specimen with the right eye preserved from the uppermost Siegenian and a small and likely juvenile specimen, confirmed the high visual acuity of the genus. The overall average IOA of Jaekelopterus (0.87°) is comparable to that of modern predatory arthropods. The visual acuity of Jaekelopterus increased with age,
11303-757: The maximum sizes reached by the species in question, which was suggested to possibly have been an evolutionary trait of the group per Cope's rule ("phyletic gigantism") by Braddy, Poschmann and Tetlie. Hughmilleria socialis (20 cm, 7.9 in) Slimonia acuminata (100 cm, 3.3 ft) Ciurcopterus ventricosus (70 cm, 2.3 ft) Erettopterus waylandsmithi (60 cm, 1.97 ft) Erettopterus osiliensis (90 cm, 2.95 ft) Erettopterus serricaudatus (60 cm, 1.97 ft) Erettopterus bilobus (70 cm, 2.3 ft) Pterygotus anglicus (160 cm, 5.2 ft) Jaekelopterus rhenaniae (250 cm, 8.2 ft) Acutiramus macrophthalmus (200 cm, 6.6 ft) Acutiramus bohemicus (210 cm, 6.9 ft) The pterygotid eurypterids include many of
11430-471: The metastoma decreased through ontogeny. The metastoma in J. howelli is also broader in juveniles than in adults, although the length–width ratios measured in juveniles and adults were not as disparate as assumed, being 1.43 in juveniles and 1.46 in adults. Such a change in metastomal dimensions has been noted in other eurypterid genera as well, such as Stoermeropterus , Moselopterus and Strobilopterus . The cheliceral morphology and visual acuity of
11557-426: The millipede Arthropleura . J. howelli was much smaller, reaching 80 centimetres (2.6 ft) in length. In overall appearance, Jaekelopterus is similar to other pterygotid eurypterids, possessing a large, expanded telson (the hindmost segment of the body) and enlarged pincers and forelimbs. Both species of Jaekelopterus were first described as species of the closely related Pterygotus but were raised as
11684-609: The name of German paleontologist Otto Jaekel , who described the type species, and the Greek word πτερόν ( pteron ) meaning "wing". Based on the isolated fossil remains of a large chelicera (claw) from the Klerf Formation of Germany, J. rhenaniae has been estimated to have reached a size of around 2.3–2.6 metres (7.5–8.5 ft), making it the largest arthropod ever discovered, surpassing other large arthropods such as fellow eurypterids Acutiramus and Pterygotus ;
11811-507: 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 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
11938-753: The opinion of Braddy, Poschmann and Tetlie, who replied to Kaiser and Klok the same year, the size estimates around 2.5 metres (8.2 ft) remain the most accurate estimates on the maximum size of the species yet. Like all other arthropods, eurypterids matured through a sequence of stages called " instars " consisting of periods of ecdysis (moulting) followed by rapid growth. Unlike many arthropods, such as insects and crustaceans, chelicerates (the group to which eurypterids like Jaekelopterus belongs, alongside other organisms such as horseshoe crabs , sea spiders and arachnids ) are generally direct developers, meaning that there are no extreme morphological changes after they have hatched. Extant xiphosurans hatch without
12065-812: The opisthosoma was covered in structures evolved from modified opisthosomal appendages. Throughout 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
12192-424: 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
12319-540: The paddle-shaped telsons present in Pterygotus and Acutiramus . Genital appendages can vary even within genera; for instance, the genital appendage of Acutiramus changes from species to species, being spoon-shaped in earlier species and then becoming bilobed and eventually beginning to look similar to the appendage of Jaekelopterus . Lamsdell and Legg concluded that an inclusive phylogenetic analysis with multiple species of Acutiramus , Pterygotus and Jaekelopterus
12446-552: 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
12573-433: 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
12700-434: 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,
12827-559: The pterygotid eurypterids separates them into distinct ecological groups. The primary method for determining visual acuity in arthropods is by determining the number of lenses in their compound eyes and the interommatidial angle (IOA), which is the angle between the optical axes of 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. Both Jaekelopterus rhenaniae and Pterygotus anglicus had high visual acuity, as suggested by
12954-522: The rami and the primary teeth slightly angled anteriorly and with a telson with an expanded terminal spine and dorsal keel. The generic name honours Otto Jaekel; the Greek word πτερόν ( pteron ), meaning "wing", is a common epithet in eurypterid names. In 1974, Størmer erected a new family to house the genus, Jaekelopteridae, due to the supposed considerable differences between the genital appendage of Jaekelopterus and other pterygotids. This diverging feature has since been proven to simply represent
13081-452: 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
13208-456: The relative proportions between the chelicerae and body length would stay the same as the animal matured. The denticles (the serrations of the claws) were observed as showing positive allometry (being proportionally larger in larger specimens), which Kaiser and Klok suggest could have occurred in the chelicerae as a whole. Furthermore, the largest coxae (limb segments) found of the same species, measuring 27 centimetres (11 in) wide, suggest
13335-445: 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
13462-458: 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
13589-435: 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
13716-405: 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
13843-416: The same number of appendages and segments as adults. Though several fossilised instars of Jaekelopterus howelli are known, the fragmentary and incomplete status of the specimens makes it difficult to study its ontogeny in detail. Despite this, there are some noticeable changes occurring in the chelicerae, telson and metastoma. Four of the J. howelli specimens studied by Lamsdell and Selden (2013) preserve
13970-413: 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
14097-429: The sixth pair of appendages were overlaid by a plate that 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
14224-415: The size of the intermediate denticles in juveniles, but up to 3.5 times the size of the intermediate denticles in adults. Furthermore, the terminal denticle was far larger and more robust in adult specimens than in juveniles. Perhaps most extreme of all, the second intermediate denticle is not different in size from the other intermediate denticles in juveniles, but it is massively elongated in adults, where it
14351-417: The smaller specimens having relatively worse eyesight. This is consistent with other pterygotids, such as Acutiramus , and has been interpreted as indicating that adult Jaekelopterus lived in darker environments, such as in deeper water. Trace fossil evidence of eurypterids also supports such a conclusion, indicating that eurypterids migrated to nearshore environments to mate and spawn. Jaekelopterus had
14478-441: 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
14605-404: The specimens in question revealed that the genital appendage of Jaekelopterus also was undivided. The material examined and phylogenetic analysis conducted by British palaeontologist Simon J. Braddy, German palaeontologist Markus Poschmann and O. Erik Tetlie in 2007 revealed that Jaekelopterus was not a basal pterygotid, but one of the most derived taxa in the group. The cladogram also contains
14732-427: 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
14859-498: 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
14986-662: The telson) he received that had been discovered at Alken in Lower Devonian deposits of the Rhineland in Germany. Jaekel considered the pretelson to be characteristic of Pterygotus , other discovered elements differing little from previously known species of that genus, such as P. buffaloensis , and he estimated the length of the animal in life to be about 1 metre (1.5 metres if the chelicerae are included, 3.3 and 4.9 ft). Based on more comprehensive material, including genital appendages, chelicerae and fragments of
15113-468: 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
15240-414: 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
15367-400: 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
15494-429: 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
15621-400: 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
15748-505: 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
15875-501: Was highly unlikely that an arthropod with the size and build of Jaekelopterus would be able to walk on land. Eurypterids such as Jaekelopterus are often popularly referred to as "sea scorpions", but the deposits from which Jaekelopterus fossils have been discovered suggest that it lived in non-marine aquatic environments. The Beartooth Butte Formation in Wyoming, where J. howelli fossils have been discovered, has been interpreted as
16002-452: 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)
16129-518: 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
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