Carcinosomatid
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Carcinosomatidae (the name deriving from the
type genus In biological taxonomy, the type genus (''genus typica'') is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearin ...
''
Carcinosoma ''Carcinosoma'' (meaning "crab body") is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of ''Carcinosoma'' are restricted to deposits of late Silurian (Late Llandovery to Early Pridoli) age. Classified as part of the fam ...
'', meaning "crab body")Meaning o
soma
at ''www.dictionary.com''. Retrieved 7 September 2018.
is a family of
eurypterids Eurypterids, often informally called sea scorpions, are a group of extinct marine arthropods that form the order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period, 467.3 million years ago. The ...
, an extinct group of aquatic
arthropods Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...
. They were members of the superfamily
Carcinosomatoidea Carcinosomatoidea is an extinct superfamily of eurypterids, an extinct group of chelicerate arthropods commonly known as "sea scorpions". It is one of the superfamilies classified as part of the suborder Eurypterina. Some carcinosomatoid genera ...
, also named after ''Carcinosoma''. Fossils of carcinosomatids have been found in
North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
,
Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...
and
Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...
, the family possibly having achieved a worldwide distribution, and range in age from the Late
Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era, and the second of twelve periods of the Phanerozoic Eon (geology), Eon. The Ordovician spans 41.6 million years f ...
to the Early
Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...
. They were among the most marine eurypterids, known almost entirely from marine environments. Carcinosomatids varied considerably in size, from species only a few centimetres in length to some of the largest known arthropods. The largest carcinosomatid species, ''Carcinosoma punctatum'', reached lengths of at least and rivalled the largest eurypterid of all, ''
Jaekelopterus ''Jaekelopterus'' is a genus of predatory eurypterid Eurypterids, often informally called sea scorpions, are a group of extinct marine arthropods that form the Order (biology), order Eurypterida. The earliest known eurypterids date to the ...
'', in size. Morphologically, carcinosomatids were highly distinct from other eurypterids, known for their powerful and spiny set of forelimbs, a broad and rounded central body and a slender and tubular tail ending in a
telson The telson () is the hindmost division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment (biology), segment of the arthropod body, or an additional division that is not a true segm ...
(the posteriormost division of the body) that was typically curved in some way. With these adaptations, the carcinosomatids were quite similar to
scorpions Scorpions are predatory arachnids of the Order (biology), order Scorpiones. They have eight legs and are easily recognized by a pair of Chela (organ), grasping pincers and a narrow, segmented tail, often carried in a characteristic forward cur ...
, and the group may have helped contribute to the common name of eurypterids becoming 'sea scorpions'. The family contains four, possibly five, genera: ''Carcinosoma'', '' Eocarcinosoma'', ''
Eusarcana ''Eusarcana'' (meaning "true flesh") is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of ''Eusarcana'' have been discovered in deposits ranging in age from the Early Silurian to the Early Devonian. Classified as part of ...
'', ''
Rhinocarcinosoma ''Rhinocarcinosoma'' is a genus of eurypterid, an extinct group of aquatic Arthropod, arthropods. Fossils of ''Rhinocarcinosoma'' have been discovered in deposits ranging of Late Silurian age in the United States, Canada and Vietnam. The genus c ...
'' and possibly the problematic genus '' Holmipterus''. It is unlikely that the carcinosomatids were strong and active swimmers, given their non-streamlined shape. It is more probable that they were nektobenthic (swimming near the bottom), possibly being
top predators An apex predator, also known as a top predator or superpredator, is a predator at the top of a food chain, without natural predators of its own. Apex predators are usually defined in terms of trophic dynamics, meaning that they occupy the hig ...
(given their size) or
scavengers Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding ...
, digging for food or perhaps even burrowing and lying in wait as
ambush predators Ambush predators or sit-and-wait predators are carnivorous animals that capture their prey via stealth, luring or by (typically instinctive) strategies utilizing an element of surprise. Unlike pursuit predators, who chase to capture prey usi ...
.


Description

Carcinosomatid
eurypterids Eurypterids, often informally called sea scorpions, are a group of extinct marine arthropods that form the order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period, 467.3 million years ago. The ...
differed considerably in size depending on the genus and species, though most species were quite large. The largest species was ''
Carcinosoma ''Carcinosoma'' (meaning "crab body") is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of ''Carcinosoma'' are restricted to deposits of late Silurian (Late Llandovery to Early Pridoli) age. Classified as part of the fam ...
punctatum'' at , one of the largest eurypterids of all, with some specimens suggesting that it may even have reached lengths of , rivalling ''
Jaekelopterus ''Jaekelopterus'' is a genus of predatory eurypterid Eurypterids, often informally called sea scorpions, are a group of extinct marine arthropods that form the Order (biology), order Eurypterida. The earliest known eurypterids date to the ...
'', the largest eurypterid, in size. The smallest carcinosomatid species was ''
Eusarcana ''Eusarcana'' (meaning "true flesh") is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of ''Eusarcana'' have been discovered in deposits ranging in age from the Early Silurian to the Early Devonian. Classified as part of ...
obesus'', at 4 centimetres (1.5 in) in length. Morphologically, the carcinosomatids were highly distinct among the eurypterids. They were swimming eurypterids (belonging to the suborder
Eurypterina Eurypterina is one of two suborders of eurypterids, an extinct group of chelicerate arthropods commonly known as "sea scorpions". Eurypterine eurypterids are sometimes informally known as "swimming eurypterids". They are known from fossil depos ...
), with large swimming paddles, a set of powerful and spiny forelimbs, a broad and rounded preabdomen (central body) and a slender, tubular abdomen, which ended in a
telson The telson () is the hindmost division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment (biology), segment of the arthropod body, or an additional division that is not a true segm ...
(the posteriormost division of the body) of variable morphology, often curved. In a sense, the carcinosomatids were rather scorpion-like in appearance, and may have contributed to the common name of eurypterids having become 'sea scorpions'. There was considerable variety in morphology within the group. The carapace was triangular to subtriangular in shape in all members of the group, through the exact shape could vary. In ''
Rhinocarcinosoma ''Rhinocarcinosoma'' is a genus of eurypterid, an extinct group of aquatic Arthropod, arthropods. Fossils of ''Rhinocarcinosoma'' have been discovered in deposits ranging of Late Silurian age in the United States, Canada and Vietnam. The genus c ...
'', there was a distinctive, shovel-shaped protrusion at the front of the carapace. The preabdomen was wide in all species, but the width also differed from species to species. The widest species, relatively speaking, was ''Eusarcana obesus'', in which the fourth segment was as wide as the first eight segments combined were long. The spinosity (how many spines) and size of the forelimbs also varied from genus to genus, with the forelimbs of ''Eusarcana'' for instance being more powerful than those of ''Rhinocarcinosoma''. The telson varied considerably between genera: in ''Rhinocarcinosoma'' it was robust and flattened, curving slightly upwards, in ''Eusarcana'' it was cylindrical and fashioned into a sharp, scorpion-like tail spike and in ''Carcinosoma'' it was flattened, ending in an expanded and segmented structure unseen in other eurypterids.


History of research

The earliest carcinosomatid species to be described was ''Carcinosoma punctatum'', first described under the name ''
Pterygotus ''Pterygotus'' is an extinct genus of giant predatory eurypterid, a group of extinct aquatic arthropods. Fossils of ''Pterygotus'' have been discovered in deposits ranging in age from Middle Silurian to Late Devonian, and have been referred to s ...
punctatus'' by
John William Salter John William Salter (15 December 1820 – 2 December 1869) was an English naturalist, geologist, and palaeontologist. Salter was apprenticed in 1835 to James De Carle Sowerby, and was engaged in drawing and engraving the plates for Sowerby' ...
in 1859. The earliest genus later seen as a carcinosomatid to be described was ''Eusarcus'' (and its type species ''E. scorpionis''), described by August R. Grote and William Henry Pitt in 1875 based on fossils recovered from the Pridoli-age Buffalo Waterlime of
New York State New York, also called New York State, is a state in the northeastern United States. Bordered by New England to the east, Canada to the north, and Pennsylvania and New Jersey to the south, its territory extends into both the Atlantic Ocean and ...
. The description of the genus was lacking and seemingly based only on the outline and shape of the fossil, which led Henry Woodward to refer ''E. scorpionis'' to ''Eurypterus'' on the grounds that it was similar in shape to ''Eurypterus punctatus'' (''Pterygotus punctatus'' having been reclassified as a species of ''Eurypterus''). Unbeknownst to Grote and Pitt, '' Eusarcus'' had already been named as a genus of extant (currently living) laniatorid
harvestmen The Opiliones (formerly Phalangida) are an Order (biology), order of arachnids, Common name, colloquially known as harvestmen, harvesters, harvest spiders, or daddy longlegs (see below). , over 6,650 species of harvestmen have been discovered w ...
of the family
Gonyleptidae Gonyleptidae is a neotropical family of harvestmen (order Opiliones) with more than 800 species, the largest in the suborder Laniatores and the second largest of the Opiliones as a whole. The largest known harvestmen are gonyleptids. Like most h ...
, in 1833 and as such constituted a
preoccupied name In biology, a homonym is a name for a taxon that is identical in spelling to another such name, that belongs to a different taxon. The rule in the International Code of Zoological Nomenclature is that the first such name to be published is the s ...
. The name being preoccupied went unnoticed until the 1930s. Also described in the late 19th century was the genus ''Eurysoma'', named alongside its type species, ''E. newlini'', by Edward Waller Claypole in 1890. When Claypole discovered later in 1890 that the name was preoccupied by a genus of modern
beetles Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Holometabola. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 40 ...
, he replaced the name ''Eurysoma'' with the name ''Carcinosoma''. In 1912,
John Mason Clarke John Mason Clarke (April 15, 1857 – May 29, 1925) was an American teacher, geologist and paleontologist. __TOC__ Early career Born in Canandaigua, New York, the fifth of six children of Noah Turner Clarke and Laura Mason Merrill, he attended ...
and
Rudolf Ruedemann Rudolf Ruedemann (October 16, 1864–June 18, 1956) was a German American paleontologist, widely known as an expert in graptolites, enigmatic fossil animals. He worked at the New York State Museum for over 40 years, including a decade as State ...
declared that the differences between ''Eusarcus'' and all related forms of eurypterids were so great that it was "entirely evident" that ''Eusarcus'' was distinct from other eurypterids. Clarke and Ruedemann referred several new species to ''Eusarcus'', including new species that would later be seen as species of the genus ''Rhinocarcinosoma'', and also concluded that ''Eusarcus'' was sufficiently similar to ''Carcinosoma'' to be synonymised. Because ''Eusarcus'' had been named earlier than ''Carcinosoma'', the taxonomical laws of priority dictated that ''Eusarcus'' would be the name of the taxon. ''Eusarcus'' was finally recognised as a preoccupied name by
Leif Størmer Leif Størmer (1 July 1905 – 15 May 1979) was a Norway, Norwegian paleontologist and geologist. He was professor of historical geology at the University of Oslo from 1946 to 1975. His father was the mathematician Carl Størmer, and his son the ...
in 1934. Størmer substituted the name for the next oldest available non-preoccupied synonym, ''Carcinosoma''. Størmer also introduced the family Carcinosomatidae, initially under the name 'Carcinosomidae', in 1934, to contain the four genera ''Carcinosoma'', ''
Mixopterus ''Mixopterus'' is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of ''Mixopterus'' have been discovered in deposits from Late Silurian age, and have been referred to several different species. Fossils have been recovered f ...
'', ''
Echinognathus ''Echinognathus'' is a genus of eurypterid, an extinct group of aquatic arthropods. The type and only species of ''Echinognathus'', ''E. clevelandi'', is known from deposits of Late Ordovician age in the United States. The generic name is derive ...
'' and ''
Megalograptus ''Megalograptus'' is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of ''Megalograptus'' have been recovered in deposits of Katian (Late Ordovician) age in North America. The genus contains five species: ''M. alveolatus ...
''. The family was amended by Erik N. Kjellesvig-Waering in Størmer's 1955 ''
Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology,'' published from 1953–2007 by the Geological Society of America and the University of Kansas, then 2009–present by the University of Kansas Paleontological Institute, is a definitive multi-authore ...
'', with the name changed to the correct Carcinosomatidae and the genera other than ''Carcinosoma'' transferred to their own families (''Mixopterus'' to the
Mixopteridae The Mixopteridae are a family of eurypterids, an extinct group of chelicerate arthropods commonly known as "sea scorpions". The family is one of two families contained in the superfamily Carcinosomatoidea (along with Carcinosomatidae), which in ...
and ''Megalograptus'' and ''Echinognathus'' to the
Megalograptidae Megalograptidae are a family of eurypterids, an extinct group of chelicerate arthropods commonly known as "sea scorpions". The megalograptids were likely the first major successful group of eurypterids, evidenced by a Late Ordovician radiation. ...
). In 1942,
Embrik Strand Embrik Strand (2 June 1876 – 3 November 1947) was an entomologist and arachnologist who classified many insect and spider species, including the greenbottle blue tarantula. Life and career Strand was born in Ål, Norway. He studied at t ...
proposed another replacement name for ''Eusarcus'', ''Eusarcana'', despite the matter having been dealt with by Størmer eight years prior. ''Rhinocarcinosoma'' was split off from ''Carcinosoma'' in 1962 by Nestor Ivanovich Novozhilov, based on its carapace being different from that of other ''Carcinosoma''. When revising the carcinosomatids in 1964, Kenneth Edward Caster and Erik N. Kjellesvig-Waering recognised ''Eusarcus'' and ''Carcinosoma'' to be distinct genera, determining the 1912 synonymisation to have been erroneous. Since ''Eusarcus'' was preoccupied, Caster and Kjellesvig-Waering, likely unaware of Strand's ''Eusarcana'', coined the replacement name ''Paracarcinosoma'' for the species previously referred to ''Eusarcus''. Also in 1964, Caster and Kjellesvig-Waering named the new genus '' Eocarcinosoma'' to account for Ordovician specimens of ''Eusarcus''/''Paracarcinosoma''. Though most of those specimens have since been identified as
pseudofossils Pseudofossils are inorganic objects, markings, or impressions that might be mistaken for fossils. Pseudofossils may be misleading, as some types of mineral deposits can mimic lifeforms by forming what appear to be highly detailed or organized st ...
, the type specimen of ''Eocarcinosoma'' is an authentic fossil and the earliest record of the family. The known geographical range of the carcinosomatids was considerably extended with the discovery of ''Rhinocarcinosoma'' fossils in Vietnam in the late 20th century, named as the species ''R. dosonensis'' in 2002. Though ''Paracarcinosoma'' was frequently used by later researchers, ''Eusarcana'', named earlier, was recognised by Jason A. Dunlop and James Lamsdell in 2012 as the valid replacement name of ''Eusarcus'', transferring the species assigned to ''Paracarcinosoma'' to that genus and designating ''Paracarcinosoma'' as a junior synonym. A 2015 phylogenetic analysis by Lamsdell and colleagues recovered '' Holmipterus'', a problematic eurypterid genus of uncertain affinities, as a basal carcinosomatid. The position of ''Holmipterus'', on account of incomplete fossil material and an apparent combination of traits from different families, is far from certain within the eurypterid family tree and its fossils may even represent two different genera, mistakenly grouped together.


Classification

The carcinosomatids are classified as part of the superfamily
Carcinosomatoidea Carcinosomatoidea is an extinct superfamily of eurypterids, an extinct group of chelicerate arthropods commonly known as "sea scorpions". It is one of the superfamilies classified as part of the suborder Eurypterina. Some carcinosomatoid genera ...
, within the infraorder
Diploperculata Diploperculata is an infraorder of eurypterids, an extinct group of aquatic arthropods commonly known as "sea scorpions". The name, derived from Greek διπλόω ("double") and ''operculum'', refers to the distinguishing feature that unites the ...
. The Carcinosomatoidea also contains the families MixopteridaeDunlop, J. A., Penney, D. & Jekel, D. 2018
A summary list of fossil spiders and their relatives
In World Spider Catalog. Natural History Museum Bern
and Megalograptidae. Carcinosomatidae was previously, from 1989 to the early 2000s, grouped with the family
Hughmilleriidae Hughmilleriidae (the name deriving from the type genus ''Hughmilleria'', which is named in honor of Scottish geologist Hugh Miller) is a family of eurypterids, an extinct group of aquatic arthropods. The hughmilleriids were the most basal member ...
in the superfamily 'Hughmillerioidea', on account of the spined limbs and all limbs, with the exception of the swimming paddles, being of a consistent type. The Hughmilleriidae is today regarded as basal members of the superfamily
Pterygotioidea Pterygotioidea (the name deriving from the type genus ''Pterygotus'', meaning "winged one") is a superfamily (taxonomy), superfamily of eurypterids, an extinct group of aquatic arthropods. Pterygotioids were the most Derived trait, derived membe ...
. The internal phylogeny of the Carcinosomatoidea is poorly resolved (unclear). The first cladogram below follows a 2007 study by eurypterid researcher O. Erik Tetlie, which was in turn based on results from various phylogenetic analyses on eurypterids conducted between 2004 and 2007, whereas the second cladogram follows a 2015 study by James Lamsdell and colleagues. Both cladograms have been simplified to only display the Carcinosomatoidea. Tetlie (2007) recovered the Carcinosomatidae as a
paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...
grouping, accounting for basal members of the Carcinosomatoidea, whereas Lamsdell ''et al''. (2015) recovered the carcinosomatids as a
monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...
group. Tetlie (2007) Lamsdell ''et al.'' (2015)


Palaeoecology

Carcinosomatid eurypterids were among the most marine eurypterids, known from deposits that were once reefs, some in lagoonal settings, and deeper waters. This is in sharp contrast to their closest relatives, the mixopterids, which are not known from deeper waters. The only other eurypterid family known from deeper waters are the pterygotids, which had a similar distribution to the carcinosomatids, albeit more successful. Based on the distribution of the pterygotids, it is possible that carcinosomatids ranged worldwide. They are, alongside the pterygotids, the only eurypterid family known from the southern continent of
Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...
in the
Silurian The Silurian ( ) is a geologic period and system spanning 23.5 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the third and shortest period of t ...
and
Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...
. The only carcinosomatid genus known from non-marine deposits is ''
Rhinocarcinosoma ''Rhinocarcinosoma'' is a genus of eurypterid, an extinct group of aquatic Arthropod, arthropods. Fossils of ''Rhinocarcinosoma'' have been discovered in deposits ranging of Late Silurian age in the United States, Canada and Vietnam. The genus c ...
'' (though it is also known marine deposits), which has been found in fluvial (river) and
lacustrine A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from t ...
(lake) settings as well. Because of their bodies not being as streamlined as those of many other swimming eurypterids, and on account of the unique morphologies of their telsons, it is considered likely that the carcinosomatids were not very active swimmers, probably adopting a more nektobenthic (swimming near the bottom) lifestyle. This lifestyle is especially exemplified in ''Rhinocarcinosoma'', where the shovel-like protrusion at the front of its carapace may have been used for digging, or "mud-grubbing", and the swimming paddles were reduced in size compared to those of other carcinosomatids. Given their size, carcinosomatids may have been
top predators An apex predator, also known as a top predator or superpredator, is a predator at the top of a food chain, without natural predators of its own. Apex predators are usually defined in terms of trophic dynamics, meaning that they occupy the hig ...
or
scavengers Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding ...
, digging for food or perhaps even burrowing and lying in wait as
ambush predators Ambush predators or sit-and-wait predators are carnivorous animals that capture their prey via stealth, luring or by (typically instinctive) strategies utilizing an element of surprise. Unlike pursuit predators, who chase to capture prey usi ...
. They may have fed on
worms The World Register of Marine Species (WoRMS) is a taxonomic database that aims to provide an authoritative and comprehensive catalogue and list of names of marine organisms. Content The content of the registry is edited and maintained by scien ...
, other arthropods,
brachiopods Brachiopods (), phylum Brachiopoda, are a phylum of animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the fron ...
and fish, using their forelimbs to push food into their mouths.


See also

*
List of eurypterid genera This list of eurypterid genera is a comprehensive listing of all genera that have ever been included in the order Eurypterida, excluding purely vernacular terms. The list includes all commonly accepted genera, but also genera that are now consider ...
*
Timeline of eurypterid research This timeline of eurypterid research is a chronologically ordered list of important fossil discoveries, controversies of interpretation, and Biological taxonomy, taxonomic revisions of eurypterids, a group of extinct aquatic arthropods closely re ...
*
Megalograptidae Megalograptidae are a family of eurypterids, an extinct group of chelicerate arthropods commonly known as "sea scorpions". The megalograptids were likely the first major successful group of eurypterids, evidenced by a Late Ordovician radiation. ...
*
Mixopteridae The Mixopteridae are a family of eurypterids, an extinct group of chelicerate arthropods commonly known as "sea scorpions". The family is one of two families contained in the superfamily Carcinosomatoidea (along with Carcinosomatidae), which in ...


Notes


References

{{Taxonbar, from=Q5038169 Carcinosomatoidea Ordovician first appearances Devonian extinctions Prehistoric arthropod families