Eurypterus: Difference between revisions - Wikipedia

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'''''Eurypterus''''' ({{IPAc-en|j|ʊəˈr|ɪ|p|t|ər|ə|s}} {{respell|yoo|RIP|tər|əs}}) is an extinct [[genus]] of [[eurypterid]], a group of organisms commonly called "sea scorpions". The genus lived during the [[Silurian]] period, from around 432 to 418 million years ago. ''Eurypterus'' is by far the most well-studied and well-known eurypterid. ''Eurypterus'' fossil specimens probably represent more than 95% of all known eurypterid specimens.<ref name="tetlie2007">{{cite journal|author=O. Erik Tetlie|year=2007|title=Distribution and dispersal history of Eurypterida (Chelicerata)|url=http://fossilinsects.net/pdfs/tetlie_2007_PX3_DistribDispersalEurypterida.pdf|url-status=dead|journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]]|volume=252|issue=3–4|pages=557–574|doi=10.1016/j.palaeo.2007.05.011|bibcode=2007PPP...252..557T |archive-url=https://web.archive.org/web/20110718202232/http://fossilinsects.net/pdfs/tetlie_2007_PX3_DistribDispersalEurypterida.pdf|archive-date=2011-07-18}}</ref>

There are fifteen species belonging to the genus ''Eurypterus'', the most common of which is ''E. remipes'', the first eurypterid [[fossil]] discovered and the [[List of U.S. state fossils|state fossil]] of [[New York (state)|New York]].

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The first fossil of ''Eurypterus'' was found in 1818 by S. L. Mitchill, a fossil collector. It was recovered from the [[Bertie Formation]] of [[New York (state)|New York]] (near [[Westmoreland, New York|Westmoreland, Oneida County]]). Mitchill interpreted the appendages on the carapace as [[Barbel (anatomy)|barbels]] arising from the mouth.<ref name="nudds"/> He consequently identified the fossil as a [[catfish]] of the genus ''[[Silurus]]''.<ref name="madrid"/><ref name="ucmp2">{{cite web|url=http://www.ucmp.berkeley.edu/arthropoda/chelicerata/eurypteridfr.html|title=Eurypterida: Fossil Record|publisher=University of California Museum of Paleontology|access-date=May 21, 2011}}</ref>

It was only after seven years, in 1825, that the American zoologist [[James Ellsworth De Kay]] identified the fossil correctly as an [[arthropod]].<ref name="waering">{{cite journal|author=Erik N. Kjellesvig-Waering|year=1958|title=The genera, species and subspecies of the family Eurypteridae, Burmeister, 1845|journal=Journal of Paleontology|volume=32|issue=6|pages=1107–1148 |issn=0022-3360}}</ref> He named it ''Eurypterus remipes'' and established the genus ''Eurypterus'' in the process. The name means 'wide wing' or 'broad paddle', referring to the swimming legs, from Greek {{lang|grc|εὐρύς}} ({{~~transl~~transliteration|grc|eurús}} 'wide') and {{lang|grc|πτερόν}} ({{~~transl~~transliteration|grc|pteron}} 'wing').<ref name="nudds"/>

However, De Kay thought ''Eurypterus'' was a [[Branchiopoda|branchiopod]] (a group of [[crustacean]]s which include [[Anostraca|fairy shrimp]]s and [[Cladocera|water flea]]s).<ref name="waering"/> Soon after, ''Eurypterus lacustris'' was also discovered in New York in 1835 by the paleontologist [[Richard Harlan]]. Another species was discovered in [[Estonia]] in 1858 by [[Jan Nieszkowski]]. He considered it to be of the same species as the first discovery (''E. remipes''); it is now known as ''E. tetragonophthalmus''.<ref name="nudds"/> These specimens from Estonia are often of extraordinary quality, retaining the actual [[cuticle]] of their exoskeletons. In 1898, the Swedish paleontologist [[Gerhard Holm]] separated these fossils from the bedrock with [[acid]]s. Holm was then able to examine the almost perfectly preserved fragments under a microscope. His remarkable study led to the modern breakthrough on eurypterid [[morphology (biology)|morphology]].<ref name="madrid"/>

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==Description==

[[File:~~Eurypterus size comparison~~Eurypterus_size_comparison_updated.png|left|thumb|Comparison of an average adult human male ({{convert|170|cm|ft|abbr=on}}) with the average ''E. remipes'' length (around {{convert|20|cm|in|abbr=on}}) and the largest known ''Eurypterus ~~remipes~~lacustris'' fossil ({{convert|~~130~~55.4|cm|ftin|abbr=on}}).]]

The largest arthropods to have ever existed were eurypterids. The largest known species (''[[Jaekelopterus rhenaniae]]'') reached up to {{convert|2.5|m|ft|abbr=on}} in length, about the size of a crocodile.<ref name="naturenews">{{cite journal|url=http://www.nature.com/news/2007/071120/full/news.2007.272.html|title=Giant sea scorpion discovered|journal=Nature|author=Daniel Cressey|access-date=May 22, 2011|doi=10.1038/news.2007.272|year=2007|doi-access=free}}</ref> Species of ''Eurypterus'', however, were much smaller.

''E. remipes'' are usually between {{convert|5|toand|8|in|cm|abbr=on|order=flip}} in length. ''E. lacustris'' average at larger sizes at {{convert|6|to|9|in|cm|abbr=on|order=flip}} in length.<ref name="size">{{cite web|url=http://eurypterids.net/EurypteridMonth5.html|title=The size that common ''Eurypterus'' species attained (Late Silurian Bertie Group of New York and Ontario, Canada)|author=Samuel J. Ciurca Jr. |publisher=Eurypterids.net|access-date=May 22, 2011|archive-date=August 15, 2011|archive-url=https://web.archive.org/web/20110815213548/http://eurypterids.net/EurypteridMonth5.html|url-status=dead}}</ref> However, a single [[telson]] (the posteriormost division of the body) of a specimen of this species reaches this length, being {{convert|14.8|cm|abbr=on}} long and indicating a specimen of {{convert|55.4|cm|abbr=on}} of length, and that is the largest specimen ever described in literature.<ref>{{cite journal|url=https://bioone.org/journals/bulletin-of-the-peabody-museum-of-natural-history/volume-62/issue-1/014.062.0101/A-Giant-Eurypterus-from-the-Silurian-Pridoli-Bertie-Group-of/10.3374/014.062.0101.short|title=A giant ''Eurypterus'' from the Silurian (Pridoli) Bertie Group of North America|first1=Alexander|last1=Ruebenstahl|first2=Samuel J. Jr.|last2=Ciurca~~, Jr.~~|first3=Derek E. G.|last3=Briggs|journal=Bulletin of the Peabody Museum of Natural History|volume=62|issue=1|pages=3–13|year=2021|doi=10.3374/014.062.0101|s2cid=233015695}}</ref> In the introduction page of ''E. remipes'' in website of [[University of Texas at Austin]] says that the largest specimen ever found was {{convert|1.3|m|ft|abbr=on}} long, currently on display at the [[Paleontological Research Institution]] of New York. However, the text section describes the group eurypterid itself rather than ''Eurypterus'', so it is not possible to determine in context whether the {{convert|1.3|m|ft|abbr=on}} long specimen is actually from ''E. remipes'' or another eurypterid.<ref name="utexas">{{cite web |title=''Eurypterus remipes'' NPL4415 |url=http://www.utexas.edu/tmm/npl/exhibits/eurypterus.html |archive-url=https://web.archive.org/web/20121020211133/http://www.utexas.edu/tmm/npl/exhibits/eurypterus.html |archive-date=Oct 20, 2012 |access-date=May 22, 2011 |publisher=Texas Natural Science Center: Non-vertebrate Paleontology, The University of Texas}}</ref> ~~However, the 1.3m specimen at the PRI is an Acutiramus macrophthalmus, a different species of eurypterid that grew to a much larger size.~~

''Eurypterus'' fossils often occur in similar sizes in a given area. This may be a result of the fossils being "sorted" into [[windrow]]s as they were being deposited in shallow waters by storms and wave action.

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Based on the width and structure of each segment, they can be divided into the broad preabdomen (segments 1 to 7) and the narrow postabdomen (segments 8 to 12).<ref name="paleopedia">{{cite web|url=http://paleopedia.free.fr/invert%E9br%E9_arthropode_eurypteridae.html|title=Les scorpions de mer (les Eurypterida)|language=fr|publisher=Paleopedia|access-date=May 23, 2011}}</ref> The preabdomen is the broader segments of the anterior portion of the ophisthosoma while the postabdomen are the last five segments of the ''Eurypterus body''. Each of the segments of the postabdomen contain lateral flattened protrusions known as the epimera with the exception of the last needle-like (styliform) part of the body known as the telson. The segment immediately preceding the telson (which also has the largest epimera of the [[postabdomen]]) is known as the pretelson.<ref name="lamsdell"/>

An alternative way to divide the ophisthosoma is by function. It can also be divided into the mesosoma (segments 1 to 6), and the metasoma (segments 7 to 12).<ref name="rich"/><ref name="lamsdell"/><ref name="plotnick">{{cite journal|author=Roy Plotnick|url=http://accessscience.com/content/Eurypterida/246600|title=Eurypterida|publisher=Access Science|access-date=May 23, 2011|doi=10.1036/1097-8542.246600}}</ref> The mesosoma contains the gills and reproductive organs of ''Eurypterus''. Its ventral segments are overlaid by appendage-derived plates known as ~~Blatfüsse~~Blattfüsse (singular ~~Blatfuss~~Blattfuss, [[German language|German]] for "sheet foot").<ref>{{cite web | url=https://core.ac.uk/reader/213406250 | title=Selectivity in the evolution of Palaeozoic arthropod groups, with focus on mass extinctions and radiations: A phylogenetic approach }}</ref> Protected within which are the branchial chambers which contain the respiratory organs of ''Eurypterus''.<ref name="dunlopwebster">{{cite journal|author1=Jason A. Dunlop |author2=Mark Webster |year=1999|title=Fossil Evidence, Terrestrialization and Arachnid Phylogeny|journal=The Journal of Arachnology|volume=27|pages=86–93|issn=0161-8202|url=http://www.museunacional.ufrj.br/mndi/Aracnologia/pdfliteratura/Dunlop%20&%20Webster%20JOA%201999%20Fossil%20Arach%20terrestrialization.pdf|access-date=May 23, 2011 }}</ref><ref name="resp"/> The metasoma, meanwhile, do not possess ~~Blatfüsse~~Blattfüsse.<ref name="plotnick"/>

Some authors incorrectly use mesosoma and preabdomen interchangeably, as with metasoma and postabdomen.

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The main respiratory organs of ''Eurypterus'' were what seems to be [[book gills]], located in branchial chambers within the segments of the mesosoma. They may have been used for underwater respiration.<ref name="burk"/> They are composed of several layers of thin tissue stacked in such a way as to resemble the pages of a book, hence the name. In addition, they also possessed five pairs of oval-shaped areas covered with microscopic projections on the ceiling of the second branchial chambers within the mesosoma, immediately below the gill tracts. These areas are known as Kiemenplatten (or gill-tracts, though the former term is preferred). They are unique to eurypterids.<ref name="resp">{{cite journal|author1=Phillip L. Manning|author2=Jason A. Dunlop|year=1995|title=The respiratory organs of Eurypterids|journal=Palaeontology|volume=38|issue=2|pages=287–297|issn=0031-0239|access-date=May 21, 2011|url=http://palaeontology.palass-pubs.org/pdf/Vol%2038/Pages%20287-297.pdf|archive-url=https://web.archive.org/web/20120309062653/http://palaeontology.palass-pubs.org/pdf/Vol%2038/Pages%20287-297.pdf|archive-date=March 9, 2012|url-status=dead|df=mdy-all}}</ref><ref name="selden">{{cite journal|author=P. A. Selden|year=1985|title=Eurypterid respiration|journal=Philosophical Transactions of the Royal Society of London|volume=B 309|issue=1138|pages=219–226|doi=10.1098/rstb.1985.0081|bibcode=1985RSPTB.309..219S|issn=0080-4622|url=http://homepage.mac.com/paulselden/Sites/Website/EuryResp.pdf|archive-url=https://web.archive.org/web/20110803072635/http://homepage.mac.com/paulselden/Sites/Website/EuryResp.pdf|url-status=dead|archive-date=August 3, 2011|access-date=May 22, 2011}}</ref>

''Eurypterus'' are [[Sexual dimorphism|sexually dimorphic]]. On the bottom side of the first two segments of the mesosoma are central appendages used for reproduction. In females, they are long and narrow. In the males they are very short.<ref name="Størmer">{{cite book|author=Lief Størmer| editor =C. Raymond| title =Treatise on Invertebrate Paleontology, Part P: Arthropoda 2: Chelicerata, Pycnogonida & Palaeoisopus| year =1955| publisher =Geological Society of America and University of Kansas Press| isbn =978-0-8137-3016-5| pages =31–34| chapter =Merostomata| title-link =Treatise on Invertebrate Paleontology}}</ref> A minority of authors, however, assume the reverse: longer genital appendage for males, shorter for females.<ref name="autec"/>

The [[exoskeleton]] of ''Eurypterus'' is often covered with small outgrowths known as ornamentation. They include pustules (small protrusions), [[Scale (anatomy)|scales]], and striations.<ref name="ea"/> They vary by species and are used for identification. For more detailed diagnostic descriptions of each species under ''Eurypterus'', see [[Eurypterus#Species|sections below]].<ref name="eur"/>

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''Eurypterus'' was the first recognized [[taxon]] of eurypterids and is the most common. As a consequence, nearly every remotely similar eurypterid in the 19th century was classified under the genus (except for the distinctive members of the family [[Pterygotidae]] and [[Stylonuridae]]). The genus was eventually split into several genera as the science of [[Taxonomy (biology)|taxonomy]] developed.<ref name="waering"/>

In 1958, several species distinguishable by closer placed eyes and spines on their swimming legs were split off into the separate genus ''[[Erieopterus]]'' by Erik Kjellesvig-Waering.<ref name="waering"/> Another split was proposed by Leif Størmer in 1973 when he reclassified some ''Eurypterus'' to ''Baltoeurypterus'' based on the size of some of the last segments of their swimming legs. O. Erik Tetlie in 2006 deemed these differences too insignificant to justify a separate genus. He merged ''Baltoeurypterus'' back into ''Eurypterus''. It is now believed that the minor variations described by Størmer are simply the differences found in adults and juveniles within a species.<ref name="tollerton">{{cite journal|author=V. P. Tollerton Jr. |year=1989|title=Morphology, Taxonomy, and Classification of the Order Eurypterida Burmeister, 1843|journal=Journal of Paleontology|volume=63|issue=5|pages=642–657 |doi=10.1017/S0022336000041275|bibcode=1989JPal...63..642T |s2cid=46953627 |issn=0022-3360}}</ref>

[[File:The_Eurypterida_of_New_York_figure_np_1.jpg|thumb|Painting painted in 1912 by [[Charles R. Knight]] depicting various eurypterids discovered in New York. The painting includes ''[[Dolichopterus]]'', ''[[Eusarcana]]'', ''[[Stylonurus]]'', ''Eurypterus'' and ''[[Hughmilleria]]''. ]]

The genus ''Eurypterus'' derives from ''E. minor'', the oldest known species from the Llandovery of Scotland. ''E. minor'' is believed to have diverged from ''[[Dolichopterus|Dolichopterus macrocheirus]]'' sometime in the Llandovery. The following is the [[phylogenetic tree]] of ''Eurypterus'' based on [[Phylogeny|phylogenetic studies]] by O. Erik Tetlie in 2006. Some species are not represented.<ref name="eur"/>

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[[File:Eurypterus.jpg|thumb|right|''E. lacustris'' from the [[Muséum national d'histoire naturelle]], France.]]

[[File:Eurypterus dekayi Exhibit Museum of Natural History.JPG|thumb|right|''E. dekayi'' from the [[University of Michigan Exhibit Museum of Natural History]], [[Michigan]].]]

[[File:Eurypterus tetragonophthalmus - Amherst College Museum of Natural History.jpg|thumb|right|''Eurypterus tetragonophthalmus'' from the [[Amherst College Museum of Natural History]], [[Massachusetts]].]]

[[File:Eurypterus fischeri (YPM IP 548869).jpg|thumb|right|''Eurypterus fischeri'' caparace from the collections of the [[Yale Peabody Museum of Natural History]], Connecticut.]]

[[File:Eurypterus pittsfordensis (YPM IP 239030).jpg|thumb|right|''Eurypterus pittsfordensis'' partial abdomen, pretelson and telson from the collections of the [[Yale Peabody Museum of Natural History]], Connecticut.]]

Species belonging to the genus, their diagnostic descriptions, [[Synonym (biology)|synonyms]] (if present), and [[Range (biology)|distribution]] are as follows:<ref name="dunlop"/>

'''''Eurypterus''''' De Kay, 1825

*?'''''Eurypterus cephalaspis''''' Salter, 1856 – Silurian, England

::Uncertain placement. Only 3 of the specimens described in 1856 are probably ''Eurypterus'', the rest probably belonged to [[Hughmilleriidae]]. Its name means 'shield head', from Greek {{wikt-lang|grc|κεφαλή}} ({{~~transl~~transliteration|grc|kephalē}} 'head'), and {{wikt-lang|grc|ἀσπίς}} ({{~~transl~~transliteration|grc|aspis}} 'shield or bowl'). Specimens recovered from [[Herefordshire]], England.<ref name="dunlop"/><ref name="eur"/>

*'''''Eurypterus dekayi''''' Hall, 1859 – Silurian, United States & Canada

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*'''''Eurypterus megalops''''' Clarke & Ruedemann, 1912 – Silurian, USA

::Specific name means "large eye", from Greek {{wikt-lang|grc|μέγας}} ({{~~transl~~transliteration|grc|megas}} 'big or large') and {{wikt-lang|grc|ὤψ}} ({{~~transl~~transliteration|grc|ōps}} 'eye'). Discovered in [[New York (state)|New York]], United States.<ref name="dunlop"/>

*?'''''Eurypterus minor''''' Laurie, 1899 – Silurian, Scotland

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*'''''Eurypterus remipes''''' DeKay, 1825 – Silurian, USA, Canada

:::= ''Carcinosoma trigona'' (Ruedemann, 1916) – Silurian, USA

::The most common ''Eurypterus'' species. Has four raised scales at the posterior margin of the carapace. Appendages I to IV has two spines on each podomere. Postabdomen has small epimera. Pretelson has small, semiangular epimera with imbricate scale ornamentation at the margins. The telson has serrated margins along most of its length. It is very similar to ''E. lacustris'' and can often only be distinguished by the position of the eyes. The specific name means 'oar-foot', from Latin {{wikt-lang|la|remo|rēmus}} ('oar') and {{wikt-lang|la|pes}} ('foot'). Found in New York and Ontario, and is the state fossil of New York.<ref name="eur"/>

*'''''Eurypterus serratus''''' (Jones & Woodward, 1888) – Silurian, Sweden

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:::= ''Eurypterus fischeri'' Eichwald, 1854 – Silurian, Ukraine

:::= ''Eurypterus fischeri '' var. ''rectangularis'' Schmidt, 1883 – Silurian, Estonia

::Four raised scales on the posterior margin of the carapce. Appendages II to IV each have two spines on each podomere. Postabdomen has small epimera. The pretelson has large, rounded epimera with imbricate scale ornamentation at the margins. Telson has imbricate scale ornamentations at the margins of the base which become serrations towards the tip. The specific name means 'four-edged eye', from Greek {{wikt-lang|grc|tetra-|τέσσαρες}} ({{~~transl~~transliteration|grc|tessares}} 'four'), {{wikt-lang|grc|γωνία}} ({{~~transl~~transliteration|grc|gōnia}} 'angle'), and {{wikt-lang|grc|ophthalmo-|ὀφθαλμός}} ({{~~transl~~transliteration|grc|ophthalmos}} 'eye'). Found in the [[Rootsiküla, Saare County|Rootsiküla Formation]] of [[Saaremaa]] (Ösel), Estonia, with additional discoveries in Ukraine, Norway, and possibly Moldova and Romania.<ref name="eur"/>

The list does not include the large number of fossils previously classified under ''Eurypterus''. Most of them are now reclassified to other genera, identified as other animals (like [[crustacean]]s) or [[pseudofossils]], or remains of doubtful placement. Classification is based on Dunlop ''et al.''(2011).<ref name="dunlop"/>

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''Eurypterus'' belongs to the suborder Eurypterina, eurypterids in which the sixth appendage had developed a broad swimming paddle remarkably similar to that of the modern-day [[swimming crab]]. Modeling studies on ''Eurypterus'' swimming behavior suggest that they utilized a drag-based rowing type of locomotion where appendages moved synchronously in near-horizontal planes.<ref name="autec"/> The paddle blades are almost vertically oriented on the backward and down stroke, pushing the animal forward and lifting it up. The blades are then oriented horizontally on the recovery stroke to slash through the water without pushing the animal back. This type of swimming is exhibited by [[crab]]s and [[water beetle]]s.<ref name="merck">{{cite web|url=http://www.geol.umd.edu/~jmerck/bsci392/lecture10/lecture10.html|title=The biomechanics of swimming|author=John W. Merck Jr. |publisher=Department of Geology, University of Maryland|access-date=May 23, 2011|archive-url=https://web.archive.org/web/20110724192433/http://www.geol.umd.edu/~jmerck/bsci392/lecture10/lecture10.html|archive-date=2011-07-24|url-status=dead}}</ref>

An alternative hypothesis for ''Eurypterus'' swimming behavior is that individuals were capable of underwater flying (or [[Aquatic locomotion|subaqueous flight]]), in which the sinuous motions and shape of the paddles themselves acting as [[hydrofoil]]s are enough to generate [[Lift (force)|lift]].<ref>{{Cite journal|last=Plotnick|first=Roy E.|date=1985|title=Lift based mechanisms for swimming in eurypterids and portunid crabs|url=https://www.cambridge.org/core/journals/earth-and-environmental-science-transactions-of-royal-society-of-edinburgh/article/lift-based-mechanisms-for-swimming-in-eurypterids-and-portunid-crabs/89954954F4CB25CD197F5BC4BB1F55D6|journal=Earth and Environmental Science Transactions of the Royal Society of Edinburgh|language=en|volume=76|issue=2–3|pages=325–337|doi=10.1017/S0263593300010543|bibcode=1985EESTR..76..325P |s2cid=85908528 |issn=1755-6929}}</ref> This type is similar to that found in [[sea turtle]]s and [[sea lion]]s. It has a relatively slower acceleration rate than the rowing type, especially since adults have proportionally smaller paddles than juveniles. But since the larger sizes of adults mean a higher [[drag coefficient]], using this type of propulsion is more energy-efficient.<ref name="autec"/><ref name="merck2"/>

Juveniles probably swam using the rowing type, the rapid acceleration afforded by this propulsion is more suited for quickly escaping predators. A small {{convert|16.5|cm|in|abbr=on}} ''Eurypterus'' could achieve two and a half body lengths per second immediately.<ref name="autec"/> Larger adults, meanwhile, probably swam with the subaqueous flight type. The maximum velocity of adults when cruising would have been {{convert|3|to|4|m|ft|abbr=on}} per second, slightly faster than turtles and [[sea otter]]s.<ref name="merck2">{{cite web|url=http://www.geol.umd.edu/~jmerck/bsci392/lecture25/lecture25.html|title=Eurypterids, arachnids, and the arthropod invasion of the land|author=John W. Merck Jr. |publisher=Department of Geology, University of Maryland|access-date=May 23, 2011|archive-url=https://web.archive.org/web/20110724192518/http://www.geol.umd.edu/~jmerck/bsci392/lecture25/lecture25.html|archive-date=2011-07-24|url-status=dead}}</ref><ref name="gknight">{{cite web|url=http://gknight.tripod.com/|title=The story of one man's plight to make fossils swim|access-date=May 23, 2011}}</ref>

[[File:Rowing.png|thumb|right|Rowing in ''Eurypterus''.]]

Trace fossil evidence indicates that ''Eurypterus'' employed a rowing stroke when in close proximity to the seafloor.<ref>{{Cite journal|last1=Vrazo|first1=Matthew B.|last2=Ciurca, ~~Jr.~~|first2=Samuel J. Jr.|date=2018-03-01|title=New trace fossil evidence for eurypterid swimming behaviour|journal=Palaeontology|language=en|volume=61|issue=2|pages=235–252|doi=10.1111/pala.12336|s2cid=133765946 |issn=1475-4983|doi-access=free|bibcode=2018Palgy..61..235V }}</ref> ''[[Arcuites|Arcuites bertiensis]]'' is an [[Ichnotaxon|ichnospecies]] that includes a pair of crescent-shaped impressions and a short medial drag, and it has been found in upper Silurian eurypterid [[Lagerstätte|Lagerstatten]] in Ontario and Pennsylvania. This trace fossil is very similar to traces made by modern aquatic swimming insects that row such as [[Corixidae|water boatmen]], and is considered to have been made by juvenile to adult-sized eurypterids while swimming in very shallow nearshore marine environments. The morphology of ''[[Arcuites|A. bertiensis]]'' suggests that ''Eurypterus'' had the ability to move its swimming appendages in both the horizontal and vertical plane.

''Eurypterus'' did not swim to hunt, rather they simply swam in order to move from one feeding site to another quickly. Most of the time they walked on the substrate with their legs (including their swimming leg). They were [[Generalist and specialist species|generalist species]], equally likely to engage in [[predation]] or [[scavenging]]. They hunted small soft-bodied [[invertebrate]]s like worms. They utilized the mass of spines on their front appendages to both kill and hold them while they used their chelicerae to rip off pieces small enough to swallow. Young individuals may also have fallen prey to [[Cannibalism (zoology)|cannibalism]] by larger adults.<ref name="autec">{{cite journal|author=Selden|first=Paul A.|year=1981|title=Functional morphology of the prosoma of Baltoeurypterus tetragonophthalmus (Fischer) (Chelicerata: Eurypterida)|url=https://www.cambridge.org/core/journals/earth-and-environmental-science-transactions-of-royal-society-of-edinburgh/article/functional-morphology-of-the-prosoma-of-baltoeurypterus-tetragonophthalmus-fischer-chelicerata-eurypterida/D47ECC0D4657530A7931691566F08D5F|journal=Transactions of the Royal Society of Edinburgh: Earth Sciences|volume=72|pages=9–48|access-date=February 9, 2018|doi=10.1017/s0263593300003217|s2cid=87664903 }}</ref>

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===Respiration===

[[File:Eurypterus Paleoart.jpg|thumb|left|[[Life restoration]] of ''Eurypterus'' in its environment]]

Examinations of the [[respiratory system]]s of ''Eurypterus'' have led many paleontologists to conclude that it was capable of breathing air and walking on land for a short amount of time. ''Eurypterus'' had two types of respiratory systems. Its main organs for breathing were the book gills inside the segments of the mesosoma. These structures were supported by semicircular 'ribs' and were probably attached near the center of the body, similar to the gills of modern horseshoe crabs.<ref name="resp"/> They were protected under platelike appendages (which actually formed the apparent 'belly' of ''Eurypterus'') known as ~~Blatfüsse~~Blattfüsse.<ref name="seldenjeram"/> These gills may have also played a role in [[osmoregulation]].<ref name="autec"/>

The second system are the Kiemenplatten, also referred to as gill-tracts. These oval-shaped areas within the body wall of the preabdomen. Their surfaces are covered with numerous small spines arranged into hexagonal 'rosettes'. These areas were [[vascularized]], hence the conclusion that they were secondary breathing organs.<ref name="selden"/>

The function of the book gills are usually interpreted to be for aquatic breathing, while the Kiemenplatten are supplementary for temporary breathing on land.<ref name="resp"/> However, some authors have argued that the two systems alone could not have supported an organism the size of ''Eurypterus''. Both structures might actually have been for breathing air and the true gills (for underwater breathing) of ''Eurypterus'' have yet to be discovered.<ref name="selden"/><ref name="seldenjeram"/> ''Eurypterus'', however, were undoubtedly primarily aquatic.<ref name="seldenjeram">{{cite journal|author1=Paul A. Selden|author2=Andrew J. Jeram|year=1989|title=Palaeophysiology of terrestrialisation in the Chelicerata|journal=Transactions of the Royal Society of Edinburgh: Earth Sciences|volume=80|issue=3–4|pages=303–310|issn=0263-5933|url=http://homepage.mac.com/paulselden/Sites/Website/Palaeophysiology.pdf|archive-url=https://web.archive.org/web/20110803072642/http://homepage.mac.com/paulselden/Sites/Website/Palaeophysiology.pdf|url-status=dead|archive-date=August 3, 2011|access-date=May 23, 2011|doi=10.1017/s0263593300028741|bibcode=1989EESTR..80..303S |s2cid=84851238 }}</ref>

===Ontogeny===

Juvenile ''Eurypterus'' differed from adults in several ways. Their carapaces were narrower and longer ([[parabola|parabolic]]) in contrast to the trapezoidal carapaces of adults. The eyes are aligned almost laterally but move to a more anterior location during growth. The preabdomen also lengthened, increasing the overall length of the ophisthosoma. The swimming legs also became narrower and the telsons shorter and broader (though in ''E. tetragonophthalmus'' and ''E. henningsmoeni'' the telsons changed from being angular in juveniles to larger and more rounded in adults). All these changes are believed to be a result of the respiratory and reproductive requirements of adults.<ref name="eur">{{cite journal|author=O. Erik Tetlie|year=2006|title=Two new Silurian species of ''Eurypterus'' (Chelicerata: Eurypterida) from Norway and Canada and the phylogeny of the genus|journal=Journal of Systematic Palaeontology|volume=4|issue=4|pages=397–412|doi=10.1017/S1477201906001921 |bibcode=2006JSPal...4..397T|s2cid=83519549|issn=1478-0941|url=http://www.museunacional.ufrj.br/mndi/Aracnologia/Eurypterida/Tetlie%202006%20Silurian%20Eurypterus.pdf|access-date= May 20, 2011|archive-date=June 6, 2020|archive-url=https://web.archive.org/web/20200606161847/http://www.museunacional.ufrj.br/mndi/Aracnologia/Eurypterida/Tetlie%202006%20Silurian%20Eurypterus.pdf|url-status=dead}}</ref>

==Paleoecology==

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The ancestors of ''Eurypterus'' were believed to have originated from Baltica (eastern Laurussia, modern western Eurasia) based on the earliest recorded fossils. During the Silurian, they spread to Laurentia (western Laurussia, modern North America) when the two continents began to collide. They rapidly colonized the continent as [[invasive species]], becoming the most dominant eurypterid in the region. This accounts for why they are the most commonly found genus of eurypterids today. ''Eurypterus'' (and other members of [[Eurypteroidea]]), however, were unable to cross vast expanses of oceans between the two supercontinents during the Silurian. Their [[Range (biology)|range]] were thus limited to the coastlines and the large, shallow, and [[Salinity|hypersaline]] inland seas of Laurussia.<ref name="madrid"/><ref name="dist"/>

[[File:Eurypterus distribution.png|thumb|Locations where ''Eurypterus'' fossils have been found<ref name="paleodb">{{cite web|url=http://paleodb.org/cgi-bin/bridge.pl?a=checkTaxonInfo&taxon_no=18968&is_real_user=1|title=''Eurypterus''|publisher=Paleobiology Database|access-date=May 20, 2011}}</ref>]]

They are now only known from fossils from North America, Europe, and northwestern [[Asia]], [[craton]]s that were the former components of Laurussia. While three species of ''Eurypterus'' were purportedly discovered in China in 1957, the evidence of them belonging to the genus (or if they were even eurypterids at all) is nonexistent. No other traces of ''Eurypterus'' in modern continents from Gondwana are currently known.<ref name="dist">{{cite journal|author=O. Erik Tetlie|year=2007|title=Distribution and dispersal history of Eurypterida (Chelicerata)|journal=Palaeogeography, Palaeoclimatology, Palaeoecology|volume=252|issue=3–4|pages=557–574|doi=10.1016/j.palaeo.2007.05.011|bibcode=2007PPP...252..557T |issn=0031-0182|url=http://fossilinsects.net/pdfs/tetlie_2007_PX3_DistribDispersalEurypterida.pdf|access-date=May 20, 2011|url-status=dead|archive-url=https://web.archive.org/web/20110718202232/http://fossilinsects.net/pdfs/tetlie_2007_PX3_DistribDispersalEurypterida.pdf|archive-date=July 18, 2011}}</ref>

''Eurypterus'' are very common fossils in their regions of occurrence, millions of specimens are possible in a given area, though access to the [[Formation (stratigraphy)|rock formations]] may be difficult.<ref name="lacustris fauna">{{cite web|url=http://eurypterids.net/EurypteruslacustrisFauna.html|title=''Eurypterus lacustris'' Fauna|author=Samuel J. Ciurca Jr. |publisher=Eurypterids.net|access-date=May 22, 2011|archive-date=August 15, 2011|archive-url=https://web.archive.org/web/20110815213946/http://eurypterids.net/EurypteruslacustrisFauna.html|url-status=dead}}</ref> Most fossil eurypterids are the disjointed shed exoskeleton (known as [[exuvia]]e) of individuals after molting ([[ecdysis]]). Some are complete but are most probably exuviae as well. Fossils of the actual remains of eurypterids (i.e. their [[Cadaver|carcasses]]) are relatively rare.<ref name="madrid"/> Fossil eurypterids are often deposited in characteristic windrows, probably a result of wave and wind action.<ref name="wave">{{cite web|url=http://eurypterids.net/EurypterusLacustris4.html|title=Commentary on a specimen of an Eurypterid|author=Samuel J. Ciurca Jr. |publisher=Eurypterids.net|access-date=May 22, 2011|archive-date=August 15, 2011|archive-url=https://web.archive.org/web/20110815213906/http://eurypterids.net/EurypterusLacustris4.html|url-status=dead}}</ref>

==See also==

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*[http://eurypterid.net/ Eurypterids.net] maintained by Samuel J. Ciurca, Jr.

*[http://gknight.tripod.com/ Fossil biomechanics]

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[[Category:Eurypterids of Europe]]

[[Category:Bertie Formation]]

[[Category:Fossil taxa described in 1825]]