Eurypterus
Encyclopedia
Eurypterus is an extinct genus
of sea scorpion
s. They existed during the Silurian
Period, from around 432 to 418 million years ago.
There are fifteen species belonging to the genus Eurypterus, the most common of which is Eurypterus remipes, the first eurypterid
fossil
discovered and the state fossil of New York
.
Members of Eurypterus averaged at about 5 to 9 in (12.7 to 22.9 cm) in length, but the largest individual discovered was 1.3 m (4.3 ft) long. They all possessed spine-bearing appendages and a large paddle they used for swimming. They were generalist species
, equally likely to engage in predation
or scavenging.
of Eurypterus was found in 1818 by S. L. Mitchill, a fossil collector. It was recovered from the Bertie Formation of New York
(near Westmoreland
, Oneida County
). Mitchill interpreted the appendages on the carapace as barbels
arising from the mouth. He consequently identified the fossil as a catfish
of the genus Silurus
.
It was only after seven years, in 1825, that the American zoologist James Ellsworth De Kay
identified the fossil correctly as an arthropod
. 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
εὐρύς (eurús, wide) and πτερόν (pteron, wing).
However, De Kay thought Eurypterus was a branchiopod
(a group of crustacean
s which include fairy shrimps and water flea
s). 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 Eurypterus tetragonophthalmus. 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 lead to the modern breakthrough on eurypterid morphology
.
More fossils were recovered in great abundance in New York in the 19th century, and elsewhere in eastern Eurasia
and North America
. Today, Eurypterus remains one of the most commonly found and best known eurypterid
genera, comprising more than 95% of all known eurypterid fossils.
Eurypteridae
. They are classified under the superfamily Eurypteroidea
, suborder Eurypterina, order
Eurypterida, and the subphylum
Chelicerata
. Until recently, eurypterid
s were thought to belong to the class
Merostomata
along with order Xiphosura
. It is now believed that eurypterids are a sister group to Arachnida, closer to scorpion
s and spider
s than to horseshoe crab
s.
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
developed.
In 1958, several species distinguishable by closer placed eyes and spines on their swimming legs were split off into the separate genus Eiropterus by Erik Kjellesvig-Waering. Another split was proposed by Lief Størmer in 1973 when he reclassified some Eurypterus to Baltoeurypterus based on the size of the 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.
s to have ever existed were eurypterids. The largest known species (Jaekelopterus rhenaniae
) reached up to 2.5 m (8.2 ft) in length, about the size of a crocodile. Species of Eurypterus, however, were much smaller.
E. remipes are usually between 5 to 8 in (12.7 to 20.3 cm) in length. E. lacustris average at larger sizes at 6 to 9 in (15.2 to 22.9 cm) in length. The largest specimen of E. remipes ever found was 1.3 m (4.3 ft) long, currently on display at the Paleontological Research Institution
of New York.
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.
The Eurypterus body is broadly divided into two parts: the prosoma and the opisthosoma
(in turn divided into the mesosoma
and the metasoma
).
The prosoma is the forward part of the body, it is actually composed of six segments fused together to form the head and the thorax
. It contains the semicircular to subrectangular platelike carapace
. On the dorsal side of the latter are two large crescent-shaped compound eyes. They also possessed two smaller light-sensitive simple eyes (the median ocelli) near the center of the carapace on a small elevation (known as the ocellar mound). Underneath the carapace is the mouth and six appendages, usually referred to in Roman numerals
I-VI. Each appendage in turn is composed of nine segments (known as podomeres) labeled in Arabic numerals
1-9. The first segments which connect the appendages to the body are known as the coxa (plural coxae).
The first pair (Appendage I) are the chelicerae
, small pincer
-like arms used for tearing food apart (mastication
) during feeding. After the chelicerae are three pairs of short legs (Appendages II, III, and IV). They are spiniferous, with predominantly two spines on each podomere and with the tipmost segment having a single spine. The last two segments are often indistinguishable and give the appearance of a single segment having three spines. They are used both for walking and for food capture. The next pair (Appendage V) is the most leg-like of all appendages, longer than the first three pairs and are mostly spineless except at the tipmost segments. The last pair (Appendage VI) are two broad paddle-like legs used for swimming. The coxae of Appendage VI are broad and flat, resembling an 'ear'.
The ophisthosoma (the abdomen
) is composed of 12 segments, each consisting of a fused upper plate (tergite) and bottom plate (sternite). It is further subdivided in two ways.
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). 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) segment known as the telson
(the 'tail'). The segment immediately preceding the telson (which also has the largest epimera of the postabdomen) is known as the pretelson.
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). The mesosoma contains the gills and reproductive organs of Eurypterus. Its ventral segments are overlaid by appendage-derived plates known as Blatfüsse (singular Blatfuss, German
for "sheet foot"). Protected within which are the branchial chambers which contain the respiratory organs of Eurypterus. The metasoma, meanwhile, do not possess Blatfüsse.
Some authors incorrectly use mesosoma and preabdomen interchangeably, as with metasoma and postabdomen.
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. They are composed of several layers of stacked thin tissue resembling 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.
Eurypterus are 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. A minority of authors, however, assume the reverse: longer genital appendage for males, shorter for females.
The exoskeleton
of Eurypterus is often covered with small outgrowths known as ornamentation. They include pustules (small protrusions), scales, and striations. They vary by species and are used for identification. For more detailed diagnostic descriptions of each species under Eurypterus, see sections below.
(around 432 million years ago) to sometime during the Přídolí epoch (418.1 million years ago) of the Silurian
period. A span of only around 10 to 14 million years.
During this period, the landmasses were mostly restricted to the southern hemisphere
of the Earth, with the supercontinent
Gondwana
straddling the South Pole
. The equator had three continents (Avalonia
, Baltica
, and Laurentia
) which slowly drifted together form the second supercontinent of Laurussia (also known as Euramerica
, not to be confused with Laurasia
).
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 an 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 ocean
s between the two supercontinents during the Silurian. Their range
were thus limited to the coastlines and the large, shallow, and hypersaline
inland seas of Laurussia.
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.
Eurypterus are very common fossils in their regions of occurrence, millions of specimens are possible in a given area, though access to the rock formations may be difficult. 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 carcasses
) are relatively rare. Fossil eurypterids are often deposited in characteristic windrows, probably a result of wave and wind action.
s and water beetle
s.
However, larger individuals may have been capable of underwater flying (or subaqueous flight
), in which the sinuous motions and shape of the paddles themselves acting as hydrofoil
s are enough to generate lift
. 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.
Juveniles probably swam using the rowing type, the rapid acceleration afforded by this propulsion is more suited for quickly escaping predators. A small 16.5 cm (6.5 in) Eurypterus could achieve two and a half body lengths per second immediately. Larger adults, meanwhile, probably swam with the subaqueous flight type. The maximum velocity of adults when cruising would have been 3 to 4 m (9.8 to 13.1 ft) per second, slightly faster than turtles and sea otter
s.
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 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
by larger adults.
Eurypterus were most probably marine
animals, as their remains are mostly found in intertidal shallow environments. The concentrations of Eurypterus fossils in certain sites has been interpreted to be a result of mass mating and molting behavior. Juveniles were likely to have inhabited nearshore hypersaline environments, safer from predators, and moved to deeper waters as they grew older and larger. Adults that reach sexual maturity would then migrate
en masse to shore areas in order to mate, lay eggs, and molt. Activities that would have made them more vulnerable to predators. This could also explain why a the vast majority of fossils found in such sites are molts and not of actual animals. The same behavior can be seen in modern horseshoe crabs.
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. They were protected under platelike appendages (which actually formed the apparent 'belly' of Eurypterus) known as Blatfüsse. These gills may have also played a role in osmoregulation
.
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.
The function of the book gills are usually interpreted to be for aquatic breathing, while the Kiemenplatten are supplementary for temporary breathing on land. 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. Eurypterus, however, were undoubtedly primarily aquatic.
) in contrast to the trapezoid
al 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.
Species belonging to the genus, their diagnostic descriptions, synonyms (if present), and distribution
are as follows:
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).
sometime in the Llandovery. The following is the phylogenetic tree
of Eurypterus based on phylogenetic studies by O. Erik Tetlie in 2006. Some species are not represented.
in 1984.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of sea scorpion
Sea Scorpion
Sea Scorpion may refer to:* Eurypterids, members of the extinct class Eurypterida* some members of the Cottidae family of fish including the Long-spined Sea Scorpion and Short-spined Sea Scorpion...
s. They existed during the Silurian
Silurian
The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...
Period, from around 432 to 418 million years ago.
There are fifteen species belonging to the genus Eurypterus, the most common of which is Eurypterus remipes, the first eurypterid
Eurypterid
Eurypterids are an extinct group of arthropods related to arachnids which include the largest known arthropods that ever lived. They are members of the extinct order Eurypterida ; which is the most diverse Paleozoic chelicerate order in terms of species...
fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
discovered and the state fossil of New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
.
Members of Eurypterus averaged at about 5 to 9 in (12.7 to 22.9 cm) in length, but the largest individual discovered was 1.3 m (4.3 ft) long. They all possessed spine-bearing appendages and a large paddle they used for swimming. They were generalist species
Generalist and specialist species
A generalist species is able to thrive in a wide variety of environmental conditions and can make use of a variety of different resources . A specialist species can only thrive in a narrow range of environmental conditions or has a limited diet. Most organisms do not all fit neatly into either...
, equally likely to engage in predation
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
or scavenging.
Discovery
The first fossilFossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
of Eurypterus was found in 1818 by S. L. Mitchill, a fossil collector. It was recovered from the Bertie Formation of New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
(near Westmoreland
Westmoreland, New York
Westmoreland is a town in Oneida County, New York, United States. The population was 6,207 at the 2000 census.The Town of Westmoreland is in the west-central part of the county. The New York State Thruway passes across the town. Westmoreland is west of Utica, New York.The Westmoreland Central...
, Oneida County
Oneida County, New York
Oneida County is a county located in the U.S. state of New York. As of the 2010 census, the population was 234,878. The county seat is Utica. The name is in honor of the Oneida, an Iroquoian tribe that formerly occupied the region....
). Mitchill interpreted the appendages on the carapace as barbels
Barbel (anatomy)
A barbel on a fish is a slender, whiskerlike tactile organ near the mouth. Fish that have barbels include the catfish, the carp, the goatfish, sturgeon, the zebrafish and some species of shark...
arising from the mouth. He consequently identified the fossil as a catfish
Catfish
Catfishes are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the heaviest and longest, the Mekong giant catfish from Southeast Asia and the second longest, the wels catfish of Eurasia, to detritivores...
of the genus Silurus
Silurus
Silurus is a genus of catfish in the Siluridae family.It contains the following species:* Silurus glanis * Silurus aristotelis * Silurus furness* Silurus mento...
.
It was only after seven years, in 1825, that the American zoologist James Ellsworth De Kay
James Ellsworth De Kay
James Ellsworth De Kay was an American zoologist.-Biography:...
identified the fossil correctly as an arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...
. 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
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
εὐρύς (eurús, wide) and πτερόν (pteron, wing).
However, De Kay thought Eurypterus was a branchiopod
Branchiopoda
Branchiopoda is a class of crustaceans. It is the sister group to the remaining crustaceans, and comprises fairy shrimp, clam shrimp, Cladocera, Notostraca and the Devonian Lepidocaris...
(a group of crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s which include fairy shrimps and water flea
Cladocera
Cladocera is an order of small crustaceans commonly called water fleas. Around 620 species have been recognised so far, with many more undescribed. They are ubiquitous in inland aquatic habitats, but rare in the oceans. Most are long, with a down-turned head, and a carapace covering the apparently...
s). Soon after, Eurypterus lacustris was also discovered in New York in 1835 by the paleontologist Richard Harlan
Richard Harlan
Richard Harlan was an American naturalist, zoologist, physicist and paleontologist....
. Another species was discovered in Estonia
Estonia
Estonia , officially the Republic of Estonia , is a state in the Baltic region of Northern Europe. It is bordered to the north by the Gulf of Finland, to the west by the Baltic Sea, to the south by Latvia , and to the east by Lake Peipsi and the Russian Federation . Across the Baltic Sea lies...
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 Eurypterus tetragonophthalmus. These specimens from Estonia are often of extraordinary quality, retaining the actual cuticle
Cuticle
A cuticle , or cuticula, is a term used for any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticles" are non-homologous; differing in their origin, structure, function, and chemical composition...
of their exoskeletons. In 1898, the Swedish paleontologist Gerhard Holm separated these fossils from the bedrock with acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...
s. Holm was then able to examine the almost perfectly preserved fragments under a microscope
Microscope
A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...
. His remarkable study lead to the modern breakthrough on eurypterid morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
.
More fossils were recovered in great abundance in New York in the 19th century, and elsewhere in eastern Eurasia
Eurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...
and North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. Today, Eurypterus remains one of the most commonly found and best known eurypterid
Eurypterid
Eurypterids are an extinct group of arthropods related to arachnids which include the largest known arthropods that ever lived. They are members of the extinct order Eurypterida ; which is the most diverse Paleozoic chelicerate order in terms of species...
genera, comprising more than 95% of all known eurypterid fossils.
Classification
The genus Eurypterus belongs to the familyFamily (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Eurypteridae
Eurypteridae
Eurypteridae are an extinct family of eurypterids. They were members of the superfamily Eurypteroidea.-Description:Eurypteridae, which lived during the Silurian period, were characterized by small to large exoskeletons with inconspicuous semilunar scales or curved ridges. The telson, was...
. They are classified under the superfamily Eurypteroidea
Eurypteroidea
Eurypteroidea are an extinct superfamily of eurypterids.-Description:Eurypteroidea, which lived from the Ordovician to Permian periods, were characterized by their last pair of prosomal appendages, which were developed as swimming legs, carrying paddles formed by the expansion of the two...
, suborder Eurypterina, order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
Eurypterida, and the subphylum
Subphylum
In life, a subphylum is a taxonomic rank intermediate between phylum and superclass. The rank of subdivision in plants and fungi is equivalent to subphylum.Not all phyla are divided into subphyla...
Chelicerata
Chelicerata
The subphylum Chelicerata constitutes one of the major subdivisions of the phylum Arthropoda, and includes horseshoe crabs, scorpions, spiders and mites...
. Until recently, eurypterid
Eurypterid
Eurypterids are an extinct group of arthropods related to arachnids which include the largest known arthropods that ever lived. They are members of the extinct order Eurypterida ; which is the most diverse Paleozoic chelicerate order in terms of species...
s were thought to belong to the class
Class (biology)
In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...
Merostomata
Merostomata
Merostomata is the name given to a grouping of the extinct Eurypterida and the Xiphosura . The term was originally used by James Dwight Dana to refer to Xiphosura only, but was emended by Henry Woodward to cover both groups....
along with order Xiphosura
Xiphosura
Xiphosura is an order of marine chelicerates which includes a large number of extinct lineages and only four recent species in the family Limulidae, which include the horseshoe crabs...
. It is now believed that eurypterids are a sister group to Arachnida, closer to scorpion
Scorpion
Scorpions are predatory arthropod animals of the order Scorpiones within the class Arachnida. They have eight legs and are easily recognized by the pair of grasping claws and the narrow, segmented tail, often carried in a characteristic forward curve over the back, ending with a venomous stinger...
s and spider
Spider
Spiders are air-breathing arthropods that have eight legs, and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms...
s than to horseshoe crab
Horseshoe crab
The Atlantic horseshoe crab, Limulus polyphemus, is a marine chelicerate arthropod. Despite its name, it is more closely related to spiders, ticks, and scorpions than to crabs. Horseshoe crabs are most commonly found in the Gulf of Mexico and along the northern Atlantic coast of North America...
s.
Eurypterus was the first recognized taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
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
Pterygotidae
Pterygotidae are an extinct family of eurypterids. They were members of the superfamily Pterygotioidea, and were the only eurypterids to have a truly worldwide distribution, and include the largest arthropods to have ever lived.-Description:...
and Stylonuridae
Stylonuridae
Stylonuridae are an extinct family of prehistoric eurypterids within the Superfamily Stylonuroidea.-Description:Stylonuridae, which lived from the Ordovician to Lower Permian periods, were small to very large forms with scales developing into tubercules and knobs. The prosoma exhibited variable...
). The genus was eventually split into several genera as the science of taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
developed.
In 1958, several species distinguishable by closer placed eyes and spines on their swimming legs were split off into the separate genus Eiropterus by Erik Kjellesvig-Waering. Another split was proposed by Lief Størmer in 1973 when he reclassified some Eurypterus to Baltoeurypterus based on the size of the 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.
Description
The largest arthropodArthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...
s to have ever existed were eurypterids. The largest known species (Jaekelopterus rhenaniae
Jaekelopterus rhenaniae
Jaekelopterus rhenaniae is an extinct species of the Eurypterida . At an estimated length of 2.5 meters , it is one of the two largest arthropods ever discovered...
) reached up to 2.5 m (8.2 ft) in length, about the size of a crocodile. Species of Eurypterus, however, were much smaller.
E. remipes are usually between 5 to 8 in (12.7 to 20.3 cm) in length. E. lacustris average at larger sizes at 6 to 9 in (15.2 to 22.9 cm) in length. The largest specimen of E. remipes ever found was 1.3 m (4.3 ft) long, currently on display at the Paleontological Research Institution
Paleontological Research Institution
The Paleontological Research Institution, or PRI, is a natural history museum in Ithaca, New York with a mission including both research and education...
of New York.
Eurypterus fossils often occur in similar sizes in a given area. This may be a result of the fossils being 'sorted' into windrow
Windrow
A windrow is a row of cut hay or small grain crop. It is allowed to dry before being baled, combined, or rolled. For hay, the windrow is often formed by a hay rake, which rakes hay that has been cut by a mower machine or by scythe into a row, or it may naturally form as the hay is mowed...
s as they were being deposited in shallow waters by storms and wave action.
The Eurypterus body is broadly divided into two parts: the prosoma and the opisthosoma
Opisthosoma
The opisthosoma is the posterior part of the body in some arthropods, behind the prosoma . It is a distinctive feature of the subphylum Chelicerata...
(in turn divided into the mesosoma
Mesosoma
The mesosoma is the middle part of the body, or tagma, of arthropods whose body is composed of three parts, the other two being the prosoma and the metasoma. It bears the legs, and, in the case of winged insects, the wings....
and the metasoma
Metasoma
The metasoma is the posterior part of the body, or tagma, of arthropods whose body is composed of three parts, the other two being the prosoma and the mesosoma. In insects, it contains most of the digestive tract, respiratory system, and circulatory system, and the apical segments are typically...
).
The prosoma is the forward part of the body, it is actually composed of six segments fused together to form the head and the thorax
Thorax
The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...
. It contains the semicircular to subrectangular platelike carapace
Carapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
. On the dorsal side of the latter are two large crescent-shaped compound eyes. They also possessed two smaller light-sensitive simple eyes (the median ocelli) near the center of the carapace on a small elevation (known as the ocellar mound). Underneath the carapace is the mouth and six appendages, usually referred to in Roman numerals
Roman numerals
The numeral system of ancient Rome, or Roman numerals, uses combinations of letters from the Latin alphabet to signify values. The numbers 1 to 10 can be expressed in Roman numerals as:...
I-VI. Each appendage in turn is composed of nine segments (known as podomeres) labeled in Arabic numerals
Arabic numerals
Arabic numerals or Hindu numerals or Hindu-Arabic numerals or Indo-Arabic numerals are the ten digits . They are descended from the Hindu-Arabic numeral system developed by Indian mathematicians, in which a sequence of digits such as "975" is read as a numeral...
1-9. The first segments which connect the appendages to the body are known as the coxa (plural coxae).
The first pair (Appendage I) are the chelicerae
Chelicerae
The chelicerae are mouthparts of the Chelicerata, an arthropod subphylum that includes arachnids, Merostomata , and Pycnogonida . Chelicerae are pointed appendages which are used to grasp food, and are found in place of the chewing mandibles most other arthropods have...
, small pincer
Pincer (biology)
A pincer is the part of an arthropod that enables it to carry loads, to defend against other creatures, or to attack prey. In insects, the pincers are usually part of the creature's mandible, and often venom or acid can be injected through the pincer into an enemy during a pincer strike.Some...
-like arms used for tearing food apart (mastication
Mastication
Mastication or chewing is the process by which food is crushed and ground by teeth. It is the first step of digestion and it increases the surface area of foods to allow more efficient break down by enzymes. During the mastication process, the food is positioned between the teeth for grinding by...
) during feeding. After the chelicerae are three pairs of short legs (Appendages II, III, and IV). They are spiniferous, with predominantly two spines on each podomere and with the tipmost segment having a single spine. The last two segments are often indistinguishable and give the appearance of a single segment having three spines. They are used both for walking and for food capture. The next pair (Appendage V) is the most leg-like of all appendages, longer than the first three pairs and are mostly spineless except at the tipmost segments. The last pair (Appendage VI) are two broad paddle-like legs used for swimming. The coxae of Appendage VI are broad and flat, resembling an 'ear'.
The ophisthosoma (the abdomen
Abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
) is composed of 12 segments, each consisting of a fused upper plate (tergite) and bottom plate (sternite). It is further subdivided in two ways.
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). 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) segment known as the telson
Telson
The telson is the last division of the body of a crustacean. It is not considered a true segment because it does not arise in the embryo from teloblast areas as do real segments. It never carries any appendages, but a forked "tail" called the caudal furca is often present. Together with the...
(the 'tail'). The segment immediately preceding the telson (which also has the largest epimera of the postabdomen) is known as the pretelson.
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). The mesosoma contains the gills and reproductive organs of Eurypterus. Its ventral segments are overlaid by appendage-derived plates known as Blatfüsse (singular Blatfuss, German
German language
German is a West Germanic language, related to and classified alongside English and Dutch. With an estimated 90 – 98 million native speakers, German is one of the world's major languages and is the most widely-spoken first language in the European Union....
for "sheet foot"). Protected within which are the branchial chambers which contain the respiratory organs of Eurypterus. The metasoma, meanwhile, do not possess Blatfüsse.
Some authors incorrectly use mesosoma and preabdomen interchangeably, as with metasoma and postabdomen.
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. They are composed of several layers of stacked thin tissue resembling 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.
Eurypterus are sexually dimorphic
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
. 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. A minority of authors, however, assume the reverse: longer genital appendage for males, shorter for females.
The exoskeleton
Exoskeleton
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...
of Eurypterus is often covered with small outgrowths known as ornamentation. They include pustules (small protrusions), scales, and striations. They vary by species and are used for identification. For more detailed diagnostic descriptions of each species under Eurypterus, see sections below.
Distribution and geologic time range
Members of Eurypterus existed for a relatively short time, yet they are the most abundant eurypterids found today. They flourished between the Late Llandovery epochEpoch (geology)
An epoch is a subdivision of the geologic timescale based on rock layering. In order, the higher subdivisions are periods, eras and eons. We are currently living in the Holocene epoch...
(around 432 million years ago) to sometime during the Přídolí epoch (418.1 million years ago) of the Silurian
Silurian
The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...
period. A span of only around 10 to 14 million years.
During this period, the landmasses were mostly restricted to the southern hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...
of the Earth, with the supercontinent
Supercontinent
In geology, a supercontinent is a landmass comprising more than one continental core, or craton. The assembly of cratons and accreted terranes that form Eurasia qualifies as a supercontinent today.-History:...
Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
straddling the South Pole
South Pole
The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is one of the two points where the Earth's axis of rotation intersects its surface. It is the southernmost point on the surface of the Earth and lies on the opposite side of the Earth from the North Pole...
. The equator had three continents (Avalonia
Avalonia
Avalonia was a microcontinent in the Paleozoic era. Crustal fragments of this former microcontinent underlie south-west Great Britain, and the eastern coast of North America. It is the source of many of the older rocks of Western Europe, Atlantic Canada, and parts of the coastal United States...
, Baltica
Baltica
Baltica is a name applied by geologists to a late-Proterozoic, early-Palaeozoic continent that now includes the East European craton of northwestern Eurasia. Baltica was created as an entity not earlier than 1.8 billion years ago. Before this time, the three segments/continents that now comprise...
, and Laurentia
Laurentia
Laurentia is a large area of continental craton, which forms the ancient geological core of the North American continent...
) which slowly drifted together form the second supercontinent of Laurussia (also known as Euramerica
Euramerica
Euramerica was a minor supercontinent created in the Devonian as the result of a collision between the Laurentian, Baltica, and Avalonia cratons .300 million years ago in the Late Carboniferous tropical rainforests lay over the equator of Euramerica...
, not to be confused with Laurasia
Laurasia
In paleogeography, Laurasia was the northernmost of two supercontinents that formed part of the Pangaea supercontinent from approximately...
).
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 an invasive species
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
, 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
Eurypteroidea
Eurypteroidea are an extinct superfamily of eurypterids.-Description:Eurypteroidea, which lived from the Ordovician to Permian periods, were characterized by their last pair of prosomal appendages, which were developed as swimming legs, carrying paddles formed by the expansion of the two...
), however, were unable to cross vast expanses of ocean
Ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...
s between the two supercontinents during the Silurian. Their range
Range (biology)
In biology, the range or distribution of a species is the geographical area within which that species can be found. Within that range, dispersion is variation in local density.The term is often qualified:...
were thus limited to the coastlines and the large, shallow, and hypersaline
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
inland seas of Laurussia.
They are now only known from fossils from North America, Europe, and northwestern Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
, craton
Craton
A craton is an old and stable part of the continental lithosphere. Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tectonic plates. They are characteristically composed of ancient crystalline basement rock, which may be covered by...
s that were the former components of Laurussia. While three species of Eurypterus were purportedly discovered in China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
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.
Eurypterus are very common fossils in their regions of occurrence, millions of specimens are possible in a given area, though access to the rock formations may be difficult. Most fossil eurypterids are the disjointed shed exoskeleton (known as exuvia
Exuvia
Exuviae is a term used in biology to describe the remains of an exoskeleton and related structures that are left after ecdysozoans have moulted...
e) of individuals after molting (ecdysis
Ecdysis
Ecdysis is the moulting of the cuticula in many invertebrates. This process of moulting is the defining feature of the clade Ecdysozoa, comprising the arthropods, nematodes, velvet worms, horsehair worms, rotifers, tardigrades and Cephalorhyncha...
). Some are complete but are most probably exuviae as well. Fossils of the actual remains of eurypterids (i.e. their carcasses
Cadaver
A cadaver is a dead human body.Cadaver may also refer to:* Cadaver tomb, tomb featuring an effigy in the form of a decomposing body* Cadaver , a video game* cadaver A command-line WebDAV client for Unix....
) are relatively rare. Fossil eurypterids are often deposited in characteristic windrows, probably a result of wave and wind action.
Paleobiology and paleoecology
Eurypterus belongs to the suborder Eurypterina, eurypterids in which the sixth appendage had developed a broad swimming paddle remarkably similar to modern-day swimming crabs. These appendages could only be moved in near-horizontal planes (i.e. they can not be bent much upwards or downwards). They are generally thought to utilize a rowing type of locomotion. The paddles are almost vertically oriented on the backward and down stroke, pushing the animal forward and lifting it up. They 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 crabCrab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
s and water beetle
Water beetle
A water beetle is a beetle adapted to living in water. Water beetles rise to the water surface and take atmospheric air into their tracheal systems. There are approximately 2000 species of water beetles. The rest marine species tend to live in the intertidal zone...
s.
However, larger individuals may have been capable of underwater flying (or subaqueous flight
Aquatic locomotion
Swimming is biologically propelled motion through a liquid medium. Swimming has evolved a number of times in a range of organisms ranging from arthropods to fish to molluscs.-Evolution of swimming:...
), in which the sinuous motions and shape of the paddles themselves acting as hydrofoil
Hydrofoil
A hydrofoil is a foil which operates in water. They are similar in appearance and purpose to airfoils.Hydrofoils can be artificial, such as the rudder or keel on a boat, the diving planes on a submarine, a surfboard fin, or occur naturally, as with fish fins, the flippers of aquatic mammals, the...
s are enough to generate lift
Lift (force)
A fluid flowing past the surface of a body exerts a surface force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the surface force parallel to the flow direction...
. This type is similar to that found in sea turtle
Sea turtle
Sea turtles are marine reptiles that inhabit all of the world's oceans except the Arctic.-Distribution:...
s and sea lion
Sea Lion
Sea lions are pinnipeds characterized by external ear-flaps, long fore-flippers, the ability to walk on all fours, and short thick hair. Together with the fur seal, they comprise the family Otariidae, or eared seals. There are six extant and one extinct species in five genera...
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
Drag coefficient
In fluid dynamics, the drag coefficient is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment such as air or water. It is used in the drag equation, where a lower drag coefficient indicates the object will have less aerodynamic or...
, using this type of propulsion is more energy-efficient.
Juveniles probably swam using the rowing type, the rapid acceleration afforded by this propulsion is more suited for quickly escaping predators. A small 16.5 cm (6.5 in) Eurypterus could achieve two and a half body lengths per second immediately. Larger adults, meanwhile, probably swam with the subaqueous flight type. The maximum velocity of adults when cruising would have been 3 to 4 m (9.8 to 13.1 ft) per second, slightly faster than turtles and sea otter
Sea Otter
The sea otter is a marine mammal native to the coasts of the northern and eastern North Pacific Ocean. Adult sea otters typically weigh between 14 and 45 kg , making them the heaviest members of the weasel family, but among the smallest marine mammals...
s.
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 species
Generalist and specialist species
A generalist species is able to thrive in a wide variety of environmental conditions and can make use of a variety of different resources . A specialist species can only thrive in a narrow range of environmental conditions or has a limited diet. Most organisms do not all fit neatly into either...
, equally likely to engage in predation
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
or scavenging. They hunted small soft-bodied invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
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
Cannibalism (zoology)
In zoology, cannibalism is the act of one individual of a species consuming all or part of another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded for more than 1500 species...
by larger adults.
Eurypterus were most probably marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
animals, as their remains are mostly found in intertidal shallow environments. The concentrations of Eurypterus fossils in certain sites has been interpreted to be a result of mass mating and molting behavior. Juveniles were likely to have inhabited nearshore hypersaline environments, safer from predators, and moved to deeper waters as they grew older and larger. Adults that reach sexual maturity would then migrate
Animal migration
Animal migration is the relatively long-distance movement of individuals, usually on a seasonal basis. It is a ubiquitous phenomenon, found in all major animal groups, including birds, mammals, fish, reptiles, amphibians, insects, and crustaceans. The trigger for the migration may be local...
en masse to shore areas in order to mate, lay eggs, and molt. Activities that would have made them more vulnerable to predators. This could also explain why a the vast majority of fossils found in such sites are molts and not of actual animals. The same behavior can be seen in modern horseshoe crabs.
Respiration
Examinations of the respiratory systemRespiratory system
The respiratory system is the anatomical system of an organism that introduces respiratory gases to the interior and performs gas exchange. In humans and other mammals, the anatomical features of the respiratory system include airways, lungs, and the respiratory muscles...
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. They were protected under platelike appendages (which actually formed the apparent 'belly' of Eurypterus) known as Blatfüsse. These gills may have also played a role in osmoregulation
Osmoregulation
Osmoregulation is the active regulation of the osmotic pressure of an organism's fluids to maintain the homeostasis of the organism's water content; that is it keeps the organism's fluids from becoming too diluted or too concentrated. Osmotic pressure is a measure of the tendency of water to move...
.
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.
The function of the book gills are usually interpreted to be for aquatic breathing, while the Kiemenplatten are supplementary for temporary breathing on land. 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. Eurypterus, however, were undoubtedly primarily aquatic.
Ontogeny
Juvenile Eurypterus differed from adults in several ways. Their carapaces were narrower and longer (parabolicParabola
In mathematics, the parabola is a conic section, the intersection of a right circular conical surface and a plane parallel to a generating straight line of that surface...
) in contrast to the trapezoid
Trapezoid
In Euclidean geometry, a convex quadrilateral with one pair of parallel sides is referred to as a trapezoid in American English and as a trapezium in English outside North America. A trapezoid with vertices ABCD is denoted...
al 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.
Species
Range (biology)
In biology, the range or distribution of a species is the geographical area within which that species can be found. Within that range, dispersion is variation in local density.The term is often qualified:...
are as follows:
- Eurypterus De Kay, 1825
- ?Eurypterus cephalaspis Salter, 1856 – Silurian, EnglandEnglandEngland is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
-
- 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 κεφαλή (kephalē, head), and ἀσπίς (aspis, shield or bowl). Specimens recovered from HerefordshireHerefordshireHerefordshire is a historic and ceremonial county in the West Midlands region of England. For Eurostat purposes it is a NUTS 3 region and is one of three counties that comprise the "Herefordshire, Worcestershire and Gloucestershire" NUTS 2 region. It also forms a unitary district known as the...
, EnglandEnglandEngland is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
.
- 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 κεφαλή (kephalē, head), and ἀσπίς (aspis, shield or bowl). Specimens recovered from Herefordshire
- Eurypterus dekayi Hall, 1859 – Silurian, USA & CanadaCanadaCanada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
-
- No raised scales on the posterior margin of the carapace or of the three front-most tergites. The rest of the tergites each have four raised scales. Four to six spines on each podomere of Appendages III and IV. Pretelson has large, rounded epimera without ornamentation on the margins. The species is very similar to E. laculatus. The species is named after James Ellsworth De KayJames Ellsworth De KayJames Ellsworth De Kay was an American zoologist.-Biography:...
. Specimens recovered from New YorkNew YorkNew York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
and OntarioOntarioOntario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....
.
- No raised scales on the posterior margin of the carapace or of the three front-most tergites. The rest of the tergites each have four raised scales. Four to six spines on each podomere of Appendages III and IV. Pretelson has large, rounded epimera without ornamentation on the margins. The species is very similar to E. laculatus. The species is named after James Ellsworth De Kay
- Eurypterus flintstonensis Swartz, 1923 – Silurian, USA
-
- Probably a synonym of E. remipes or E. lacustris. Probably named after Flintstone, GeorgiaFlintstone, GeorgiaFlintstone is an unincorporated community in Walker County, Georgia, United States. Located in northwestern Georgia, Flintstone lies approximately 120 miles northwest of Atlanta, 135 miles southwest of Nashville, Tennessee, and 150 miles northeast of Birmingham, Alabama...
(?). Specimen recovered from eastern United States.
- Probably a synonym of E. remipes or E. lacustris. Probably named after Flintstone, Georgia
- Eurypterus hankeni Tetlie, 2006 – Silurian, NorwayNorwayNorway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
-
- Small Eurypterus species, averaging at 10 to 15 cm (3.9 to 5.9 in) long. The largest specimen found is about 20 to 25 cm (7.9 to 9.8 in) in length. They can be distinguished by pustules and six scales at the rear margin of their carapaces. Appendages I to IV has two spines on each podomere. The postabdomen have small epimera. The pretelson has long pointed epimera. Telson has striations near its attachment to the pretelson. The species is named after Norwegian paleontologist Nils-Martin Hanken, of the University of TromsøUniversity of TromsøThe University of Tromsø is the world's northernmost university. Located in the city of Tromsø, Norway, it was established in 1968, and opened in 1972. It is one of eight universities in Norway. The University of Tromsø is the largest research and educational institution in northern Norway...
. Found in the Steinsfjorden Formation of RingerikeRingerikeoskar er kjempe kulRingerike is a municipality in Buskerud county, Norway. It is part of the traditional region of Ringerike...
, NorwayNorwayNorway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
.
- Small Eurypterus species, averaging at 10 to 15 cm (3.9 to 5.9 in) long. The largest specimen found is about 20 to 25 cm (7.9 to 9.8 in) in length. They can be distinguished by pustules and six scales at the rear margin of their carapaces. Appendages I to IV has two spines on each podomere. The postabdomen have small epimera. The pretelson has long pointed epimera. Telson has striations near its attachment to the pretelson. The species is named after Norwegian paleontologist Nils-Martin Hanken, of the University of Tromsø
- Eurypterus henningsmoeni Tetlie, 2002 – Silurian, Norway
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- Eurypterus with broad paddles and metastoma. Postabdomen has small epimera. Pretelson has large rounded epimera with imbricate scales (overlapping, similar to fish scales). It is very similar and closely related to E. tetragonophthalmus. The species was named after the Norwegian paleontologist Gunnar HenningsmoenGunnar HenningsmoenGunnar Henningsmoen was a Norwegian palaeontologist.He was born in Kristiania as a son of Colonel Nils H. Henningsmoen. In 1962 he married Kari Egede Larssen....
. Found in BærumBærumis a municipality in Akershus county, Norway. The administrative centre of the municipality is the town of Sandvika. Bærum was established as a municipality on 1 January 1838. A suburb of Oslo, Bærum is located on the west coast of the city....
, Norway.
- Eurypterus with broad paddles and metastoma. Postabdomen has small epimera. Pretelson has large rounded epimera with imbricate scales (overlapping, similar to fish scales). It is very similar and closely related to E. tetragonophthalmus. The species was named after the Norwegian paleontologist Gunnar Henningsmoen
- Eurypterus laculatus Kjellesvig-Waering, 1958 – Silurian, USA & Canada
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- The visual area of the compound eyes of this species are surrounded by depressions. The ocelli and the ocellar mound are small. No pustules or raised scales on the carapace or the first tergite. It is probably closely related to E. dekayi. Its specific name means "four-cornered", from Latin laculatus (four-cornered or checkered). Found in New York and Ontario.
- Eurypterus lacustris Harlan, 1834 – Silurian, USA & Canada
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- = Eurypterus pachycheirus Hall, 1859 – Silurian, USA & Canada
- = Eurypterus robustus Hall, 1859 – Silurian, USA & Canada
- One of the two most common Eurypterus fossils found. It is very similar to E. remipes and often found in the same localities, but the eyes are placed at a more posterior position on the carapace of E. lacustris. It is also slightly larger with a slightly narrower metastoma. Its status as a distinct species was once disputed before diagnostic analysis by Tollerton in 1993. Its specific name means "from a lake", from Latin lacus (lake). Found in New York and Ontario.
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- Eurypterus leopoldi Tetlie, 2006 – Silurian, Canada
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- Frontmost tergite is reduced. Metasoma is rhombiovate in shape with tooth-like projections at the anterior part. The pretelson has serrated edges. the epimera are large, semi-angular with angular striations. The telson is styliform with large angular striations interspersed among smaller more numerous striations. The species is named after Port LeopoldPort LeopoldThe locality Port Leopold is an abandoned trading post in the Qikiqtaaluk Region of Nunavut, Canada. It faces Prince Regent Inlet at the northeast tip of Somerset Island.Elwin Bay is to the south, while Prince Leopold Island is to the north.-History:...
and the Leopold Formation were they were collected. Found in the Leopold Formation of Somerset Island, Canada.
- Frontmost tergite is reduced. Metasoma is rhombiovate in shape with tooth-like projections at the anterior part. The pretelson has serrated edges. the epimera are large, semi-angular with angular striations. The telson is styliform with large angular striations interspersed among smaller more numerous striations. The species is named after Port Leopold
- Eurypterus megalops Clarke & Ruedemann, 1912 – Silurian, USA
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- Specific name means "large eye", from Greek μέγας (megas, big or large) and ὤψ (ōps, eye). Discovered in New YorkNew YorkNew York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
, USA.
- Specific name means "large eye", from Greek μέγας (megas, big or large) and ὤψ (ōps, eye). Discovered in New York
- ?Eurypterus minor Laurie, 1899 – Silurian, ScotlandScotlandScotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
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- Small Eurypterus with large pustules on the carapace and abdomen. Does not possess the scale ornamentation found in other species of Eurypterus. It is the earliest known species of Eurypterus. They have large palpebral lobes (part of "cheeks" of the carapace adjacent to the compound eyes), making it easy to mistake their eyes for being oval. This enlargement is more typical of the genus DolichopterusDolichopterusDolichopterus is a genus of the prehistoric sea scorpions, arthropods in the order Eurypterida.-Distribution:It lived in the Late Silurian in shelf or epicontinental seas of the region where Avalonia, Baltica and Laurentia met during the Caledonian orogeny; its fossils have been found in...
and it may actually belong to DolichopteridaeDolichopteridaeDolichopteridae are an extinct family of eurypterids that lived in the Silurian and Devonian periods.-Description:Dolichopteridae had outer surfaces that were either smooth or with pustules and semilunar scales. Their compound eyes were arcuate and located anteriorly on the prosoma . Their...
. The specific name means "smaller", from LatinLatinLatin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
minor. Found in the Reservoir Formation of Pentland HillsPentland HillsThe Pentland Hills are a range of hills to the south-west of Edinburgh, Scotland. The range is around 20 miles in length, and runs south west from Edinburgh towards Biggar and the upper Clydesdale.Some of the peaks include:* Scald Law...
, ScotlandScotlandScotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
.
- Small Eurypterus with large pustules on the carapace and abdomen. Does not possess the scale ornamentation found in other species of Eurypterus. It is the earliest known species of Eurypterus. They have large palpebral lobes (part of "cheeks" of the carapace adjacent to the compound eyes), making it easy to mistake their eyes for being oval. This enlargement is more typical of the genus Dolichopterus
- Eurypterus ornatus Leutze, 1958 – Silurian, USA
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- Ornamentation of pustules on the entire surface of the carapace and at least the first tergite. Does not possess raised scales. Its specific name means "adorned", from Latin ōrnātus (adorned, ornate). Recovered from FayetteFayette, OhioFayette is a village in Fulton County, Ohio, United States. The population was 1,340 at the 2000 census.- Geography :Fayette is located at ....
, OhioOhioOhio is a Midwestern state in the United States. The 34th largest state by area in the U.S.,it is the 7th‑most populous with over 11.5 million residents, containing several major American cities and seven metropolitan areas with populations of 500,000 or more.The state's capital is Columbus...
.
- Ornamentation of pustules on the entire surface of the carapace and at least the first tergite. Does not possess raised scales. Its specific name means "adorned", from Latin ōrnātus (adorned, ornate). Recovered from Fayette
- Eurypterus pittsfordensis Sarle, 1903 – Silurian, USA
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- The posterior margin of the carapace has three raised scales. Apendages II to IV has two spines per podomere. The metastoma is rhomboid in shape with a deep notch at the front part. The postabdomen has serrated fringes at the middle with small angular epimera at the sides. The pretelson has large, semiangular epimera with angular striations at the margins. The telson is styliform with sparse angular striations at the margins. The name of the species comes from its place of discovery – the Salina shale formations of PittsfordPittsford (town), New YorkPittsford is a town in Monroe County, New York, United States and is an affluent suburb of Rochester. The population was 29,405 at the 2010 census....
, New York.
- The posterior margin of the carapace has three raised scales. Apendages II to IV has two spines per podomere. The metastoma is rhomboid in shape with a deep notch at the front part. The postabdomen has serrated fringes at the middle with small angular epimera at the sides. The pretelson has large, semiangular epimera with angular striations at the margins. The telson is styliform with sparse angular striations at the margins. The name of the species comes from its place of discovery – the Salina shale formations of Pittsford
- Eurypterus quebecensis Kjellesvig-Waering, 1958 – Silurian, Canada
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- Has six raised scales on the posterior margin of the carapace but does not possess pustule ornamentation. It is named after the location it was recovered from – QuebecQuebecQuebec or is a province in east-central Canada. It is the only Canadian province with a predominantly French-speaking population and the only one whose sole official language is French at the provincial level....
, Canada.
- Has six raised scales on the posterior margin of the carapace but does not possess pustule ornamentation. It is named after the location it was recovered from – Quebec
- Eurypterus remipes DeKay, 1825 – Silurian, USA, Canada
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- = 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 LatinLatinLatin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
rēmus (oar) and pes (foot). Found in New York and Ontario.
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- Eurypterus serratus (Jones & Woodward, 1888) – Silurian, SwedenSwedenSweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
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- Similar to E. pittsfordensis and E. leopoldi but can be distinguished by the dense angular striations on their styliform telson. The specific name means "serrated", from Latin serrātus (sawn [into pieces]). Originally discovered from GotlandGotlandGotland is a county, province, municipality and diocese of Sweden; it is Sweden's largest island and the largest island in the Baltic Sea. At 3,140 square kilometers in area, the region makes up less than one percent of Sweden's total land area...
, Sweden.
- Similar to E. pittsfordensis and E. leopoldi but can be distinguished by the dense angular striations on their styliform telson. The specific name means "serrated", from Latin serrātus (sawn [into pieces]). Originally discovered from Gotland
- Eurypterus tetragonophthalmus Fischer, 1839 – Silurian, UkraineUkraineUkraine is a country in Eastern Europe. It has an area of 603,628 km², making it the second largest contiguous country on the European continent, after Russia...
& EstoniaEstoniaEstonia , officially the Republic of Estonia , is a state in the Baltic region of Northern Europe. It is bordered to the north by the Gulf of Finland, to the west by the Baltic Sea, to the south by Latvia , and to the east by Lake Peipsi and the Russian Federation . Across the Baltic Sea lies...
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- = Eurypterus fischeri Eichwald, 1854 – Silurian, Ukraine
- = Eurypterus fischeri var. rectangularis Schmidt, 1883 – Silurian, EstoniaEstoniaEstonia , officially the Republic of Estonia , is a state in the Baltic region of Northern Europe. It is bordered to the north by the Gulf of Finland, to the west by the Baltic Sea, to the south by Latvia , and to the east by Lake Peipsi and the Russian Federation . Across the Baltic Sea lies...
- 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 τέσσαρες (tessares, four), γωνία (gōnia, angle), and ὀφθαλμός (ophthalmos, eye). Found in the Rootsiküla FormationRootsiküla, Saare CountyRootsiküla, Saare County is a village in Kihelkonna Parish, Saare County in western Estonia....
of SaaremaaSaaremaaSaaremaa is the largest island in Estonia, measuring 2,673 km². The main island of Saare County, it is located in the Baltic Sea, south of Hiiumaa island, and belongs to the West Estonian Archipelago...
(ÖselSaaremaaSaaremaa is the largest island in Estonia, measuring 2,673 km². The main island of Saare County, it is located in the Baltic Sea, south of Hiiumaa island, and belongs to the West Estonian Archipelago...
), EstoniaEstoniaEstonia , officially the Republic of Estonia , is a state in the Baltic region of Northern Europe. It is bordered to the north by the Gulf of Finland, to the west by the Baltic Sea, to the south by Latvia , and to the east by Lake Peipsi and the Russian Federation . Across the Baltic Sea lies...
with additional discoveries in Ukraine, Norway, and possibly MoldovaMoldovaMoldova , officially the Republic of Moldova is a landlocked state in Eastern Europe, located between Romania to the West and Ukraine to the North, East and South. It declared itself an independent state with the same boundaries as the preceding Moldavian Soviet Socialist Republic in 1991, as part...
and RomaniaRomaniaRomania is a country located at the crossroads of Central and Southeastern Europe, on the Lower Danube, within and outside the Carpathian arch, bordering on the Black Sea...
.
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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
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s) or pseudofossils, or remains of doubtful placement. Classification is based on Dunlop et al.(2011).
Phylogeny
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 macrocheirusDolichopterus
Dolichopterus is a genus of the prehistoric sea scorpions, arthropods in the order Eurypterida.-Distribution:It lived in the Late Silurian in shelf or epicontinental seas of the region where Avalonia, Baltica and Laurentia met during the Caledonian orogeny; its fossils have been found in...
sometime in the Llandovery. The following is the phylogenetic tree
Phylogenetic tree
A phylogenetic tree or evolutionary tree is a branching diagram or "tree" showing the inferred evolutionary relationships among various biological species or other entities based upon similarities and differences in their physical and/or genetic characteristics...
of Eurypterus based on phylogenetic studies by O. Erik Tetlie in 2006. Some species are not represented.
In popular culture
Eurypterus remipes was designated the New York State Fossil by the then Governor Mario CuomoMario Cuomo
Mario Matthew Cuomo served as the 52nd Governor of New York from 1983 to 1994, and is the father of Andrew Cuomo, the current governor of New York.-Early life:...
in 1984.
External links
- Eurypterid.co.uk maintained by James Lamsdell
- Eurypterids.net maintained by Samuel J. Ciurca, Jr.
- Fossil biomechanics