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109-680: 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 , M. ohioensis , M. shideleri , M. welchi and M. williamsae , all based on fossil material found in the United States . Fossils unassigned to any particular species have also been found in Canada . The generic name translates to "great writing" and originates from

218-557: A species : see Botanical name and Specific name (zoology) . The rules for the scientific names of organisms are laid down in the nomenclature codes , which allow each species a single unique name that, for animals (including protists ), plants (also including algae and fungi ) and prokaryotes ( bacteria and archaea ), is Latin and binomial in form; this contrasts with common or vernacular names , which are non-standardized, can be non-unique, and typically also vary by country and language of usage. Except for viruses ,

327-403: A balancing organ. The third joint of the swimming paddles of Megalograptus bent the appendages forwards, a rare feature in the eurypterids, otherwise mostly known from the distantly related genus Dolichopterus . The wide swimming paddles of Megalograptus were formed from the sixth joint of the appendage. The seventh joint, which in many genera formed a major part of the paddle, was reduced to

436-458: A biological rudder , but they were also able to articulate and move like a scissor . Given that there are no canals for poison in the telson of Megalograptus , it is possible that they were used almost akin to giant pincers, making the telson and the surrounding structures into a grasping organ, possibly used for defense and during mating. Megalograptus is known from what were once near-shore marine environments. M. ohioensis occurred alongside

545-557: A clade) with both the Eurypteroidea and the Mixopteroidea (now considered a synonym of Carcinosomatoidea ), as well as having a large number of apomorphies (characteristics different from what existed in the ancestor of an organism). Depending on how the analysis was conducted, Megalograptus changed position in the phylogenetic tree, only sometimes being recovered as basal within the Mixopteroidea (if taxa where less than one third of

654-421: A handicap. Potential mates know that the ornament indicates quality because inferior mates could not afford to produce such wastefully extravagant ornaments. More specifically, ornaments may indicate the underlying genetic quality of the male, for example, in peafowls their tail size and symmetry is largely dictated by genetics. In other words, each peafowl grows the best tail they are able to and only those with

763-675: A harem, or obtain access to territories Examples of animals that use armaments to compete in battle against rival males include deer and antelope; scarabid, lucanid, and cerambycid beetles; certain fish, and narwhales. A buck in peak physical health will shed his antlers later than a weaker buck. Antlers harden just before the breeding season and drop off afterward, and they only occur in males (except in caribou). Antlers are used extensively for fighting and ritualized antler to antler shoving matches. Biological ornaments are used in courtship displays in many species, especially insects, fish, and birds. A well known ornament used in courting displays

872-411: A hitherto undetermined species, only growing to about 10 cm (3.9 in) in length. Morphologically , Megalograptus was highly distinct. The two most distinctive features of Megalograptus were its massive and spined forward-facing appendages , far larger than similar structures in other eurypterids, and its telson (the last division of the body). The sharp spike-shaped telson of Megalograptus

981-401: A large grasping organ. In other eurypterids, the telson tends to be an undivided structure in the shape of a paddle or spike, meaning that the cercal blades distinguish Megalograptus from nearly all other eurypterids. Cercal blades are only known from one other eurypterid, Holmipterus , and are lacking in the basal ("primitive") megalograptid Pentecopterus . Taken together with the telson,

1090-643: A later homonym of a validly published name is a nomen illegitimum or nom. illeg. ; for a full list refer to the International Code of Nomenclature for algae, fungi, and plants and the work cited above by Hawksworth, 2010. In place of the "valid taxon" in zoology, the nearest equivalent in botany is " correct name " or "current name" which can, again, differ or change with alternative taxonomic treatments or new information that results in previously accepted genera being combined or split. Prokaryote and virus codes of nomenclature also exist which serve as

1199-621: A long time and redescribed as new by a range of subsequent workers, or if a range of genera previously considered separate taxa have subsequently been consolidated into one. For example, the World Register of Marine Species presently lists 8 genus-level synonyms for the sperm whale genus Physeter Linnaeus, 1758, and 13 for the bivalve genus Pecten O.F. Müller, 1776. Within the same kingdom, one generic name can apply to one genus only. However, many names have been assigned (usually unintentionally) to two or more different genera. For example,

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1308-422: A male will mate and has been shown to affect survival of their offspring. The offspring of males with larger eyespots on their ornamented tails have been shown to weigh more and were more likely to be alive after 2 years than the progeny of males with fewer eyespots. Ornaments that play a role in reproduction develop under the influence of two series of genes. First, it develops from genes in males that determine

1417-410: A new species, M. ohioensis . The type material of M. welchi was compared to the new fossils by Caster and Kjellesvig-Waering, though only in the "walking legs" (i.e. the second to fifth pair of appendages) given that they were the only body part preserved for both M. welchi and M. ohioensis . While recognized as being of the same genus, Caster and Kjellesvig-Waering also noted differences, supporting

1526-409: A reference for designating currently accepted genus names as opposed to others which may be either reduced to synonymy, or, in the case of prokaryotes, relegated to a status of "names without standing in prokaryotic nomenclature". An available (zoological) or validly published (botanical) name that has been historically applied to a genus but is not regarded as the accepted (current/valid) name for

1635-417: A relatively small structure. The eighth joint, not preserved in any known Megalograptus fossil material, is indicated as existing by attachment points in the seventh joint, which also indicate that it was significantly smaller than in other eurypterids. The mesosoma of Megalograptus (the first six segments after the head) was distinctly similar to the same segments in modern scorpions and different from

1744-587: A scenario in which female ornamentation occurs is in the pipefish . Within this species of fish, sex roles are reversed so the male is responsible for the postzygotic care. Accordingly, females must compete for access to male parental care. Thus, females have been selected for ornamentation as the benefit of producing the ornamentation, namely male paternal care, outweighs the costs, such as the energy requirements. Most notably, their venter becomes more colourful during breeding season. Males tend to prefer females with more colourful venters, with research showing that there

1853-417: A species. Female ornamentation has long been overlooked because of the greater prevalence of elaborate displays in males. However, the circumstances under which females would benefit from honestly signaling their quality are limited. Females are not expected to invest in ornamentation unless the fitness benefits of the ornament exceed those from investing the resources directly into offspring. An example of

1962-427: A taxon; however, the names published in suppressed works are made unavailable via the relevant Opinion dealing with the work in question. In botany, similar concepts exist but with different labels. The botanical equivalent of zoology's "available name" is a validly published name . An invalidly published name is a nomen invalidum or nom. inval. ; a rejected name is a nomen rejiciendum or nom. rej. ;

2071-455: A total of c. 520,000 published names (including synonyms) as at end 2019, increasing at some 2,500 published generic names per year. "Official" registers of taxon names at all ranks, including genera, exist for a few groups only such as viruses and prokaryotes, while for others there are compendia with no "official" standing such as Index Fungorum for fungi, Index Nominum Algarum and AlgaeBase for algae, Index Nominum Genericorum and

2180-458: A typical Late Ordovician fauna, including trilobites ( Isotelus and Flexicalymene ), bryozoans , gastropods , pelecypods , brachiopods , ostracods and scolecodonts . The late Ordovician fossils of M. ohioensis , as well as the associated fauna, were found in a rock layer containing remnants of volcanic ash , indicating that the ecosystem in which they lived was destroyed through a volcanic eruption. The fauna co-occurring with M. shideleri

2289-641: Is a positive association between this ornament and the condition of the female. As this ornamentation reliably indicates mate quality, it can be considered an honest signal . In the phalaropes and the Eurasian dotterel , females are more brightly colored than males, and it is the males who are primarily responsible for parental care. It has been proposed that when females gain direct benefits from mating, females may instead be selected for ornamentation that deceives males about their reproductive state. In empidid dance flies, males frequently provide nuptial gifts and it

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2398-659: Is also seen in the common roach fish, Rutilus rutilus . Male roach develop sexual ornaments ( breeding tubercles ) during the breeding season. Roach display lek-like spawning behavior, whereby females choose between males, usually choosing the more elaborately ornamented ones. There are many instances in which decorations may appear ornamental but actually serve other functions. For example, some species of spiders decorate their webs with shimmering ornaments in order to lure prey. Orb-weaver spiders use elaborate, ultraviolet coloured web ornaments to attract bees that specialize in taking nectar from similarly coloured flowers. In turn,

2507-472: Is considered unlikely that Megalograptus would have been able to crush shelled, bio-mineralized organisms. Because of the large size of the coprolites and the presence of fossil material of M. ohioensis in and around them, it has been suggested that they are coprolites of M. ohioensis itself, thus representing evidence of cannibalism . Because cannibalism is prevalent in modern chelicerates, such as spiders and scorpions (particularly in mating situations), it

2616-596: Is discouraged by both the International Code of Zoological Nomenclature and the International Code of Nomenclature for algae, fungi, and plants , there are some five thousand such names in use in more than one kingdom. For instance, A list of generic homonyms (with their authorities), including both available (validly published) and selected unavailable names, has been compiled by the Interim Register of Marine and Nonmarine Genera (IRMNG). The type genus forms

2725-543: Is possible that eurypterids would have practiced cannibalism as well. Similar coprolites assigned to the eurypterid Lanarkopterus dolichoschelus , also from the Ordovician of Ohio, contain, in addition to remains of jawless fish , fragments of smaller specimens of Lanarkopterus itself. If the coprolites belong to Megalograptus , they also further indicate that the genus had a carnivorous diet. The large spines on its third pair of appendages already indicate that Megalograptus

2834-415: Is seen in peafowls . Male peacocks spread and shake their tails to attract and impress potential mates. Peahens choose the peacocks with the largest number of eyespots on their tails, because only the healthiest peacocks can afford to divert energy and nutrients towards growing expensive and cumbersome plumage, as explained by the handicap principle. More elaborate ornamentation increases the likelihood that

2943-460: Is somewhat arbitrary. Although all species within a genus are supposed to be "similar", there are no objective criteria for grouping species into genera. There is much debate among zoologists about whether enormous, species-rich genera should be maintained, as it is extremely difficult to come up with identification keys or even character sets that distinguish all species. Hence, many taxonomists argue in favor of breaking down large genera. For instance,

3052-474: Is the type species , and the generic name is permanently associated with the type specimen of its type species. Should the specimen turn out to be assignable to another genus, the generic name linked to it becomes a junior synonym and the remaining taxa in the former genus need to be reassessed. In zoological usage, taxonomic names, including those of genera, are classified as "available" or "unavailable". Available names are those published in accordance with

3161-621: The International Code of Zoological Nomenclature ; the earliest such name for any taxon (for example, a genus) should then be selected as the " valid " (i.e., current or accepted) name for the taxon in question. Consequently, there will be more available names than valid names at any point in time; which names are currently in use depending on the judgement of taxonomists in either combining taxa described under multiple names, or splitting taxa which may bring available names previously treated as synonyms back into use. "Unavailable" names in zoology comprise names that either were not published according to

3270-799: The International Plant Names Index for plants in general, and ferns through angiosperms, respectively, and Nomenclator Zoologicus and the Index to Organism Names for zoological names. Totals for both "all names" and estimates for "accepted names" as held in the Interim Register of Marine and Nonmarine Genera (IRMNG) are broken down further in the publication by Rees et al., 2020 cited above. The accepted names estimates are as follows, broken down by kingdom: The cited ranges of uncertainty arise because IRMNG lists "uncertain" names (not researched therein) in addition to known "accepted" names;

3379-488: The Martinsburg Formation of New York and Pennsylvania. Shortly after being recognized as a eurypterid in the early 20th century, Megalograptus was noted by Foerste in 1912 as being similar, and likely closely related, to the genus Echinognathus . In 1934, Størmer classified Megalograptus and Echinognathus , together with the genera Mixopterus and Carcinosoma , into the family Carcinosomatidae . The taxonomy

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3488-499: The appendages of Megalograptus unusually had one more joint than was common in eurypterids. Among the appendages, the third pair (counting the simple chelicerae , pincers or mouth parts, as the first pair) are the most notable. In Megalograptus these were massive structures, covered in pairs of great spines, only comparable to the same structures in Mixopterus , another eurypterid. The appendages of Megalograptus , about 3.5 times

3597-582: The genes that produce the ornament will be passed on to her offspring , increasing their own reproductive fitness . As Ronald Fisher noted, the male offspring will inherit the ornament while the female offspring will inherit the preference for said ornament, which can lead to a positive feedback loop known as a Fisherian runaway . These structures serve as cues to animal sexual behaviour , that is, they are sensory signals that affect mating responses. Therefore, ornamental traits are often selected by mate choice. There are several evolutionary explanations for

3706-404: The platypus belongs to the genus Ornithorhynchus although George Shaw named it Platypus in 1799 (these two names are thus synonyms ) . However, the name Platypus had already been given to a group of ambrosia beetles by Johann Friedrich Wilhelm Herbst in 1793. A name that means two different things is a homonym . Since beetles and platypuses are both members of the kingdom Animalia,

3815-425: The trilobite Isotelus and of eurypterids, including M. ohioensis itself, interpreted as coprolites (fossilized dung). Based on its foraging strategy which would have suited for consuming flat organisms, Megalograptus may have hunted pelagic soft-bodied prey such as freshly-molted trilobites , sea jellies , ctenophores , and other nektobenthic taxa; given that it likely didn't have fortified gnathobases, it

3924-469: The French botanist Joseph Pitton de Tournefort (1656–1708) is considered "the founder of the modern concept of genera". The scientific name (or the scientific epithet) of a genus is also called the generic name ; in modern style guides and science, it is always capitalised. It plays a fundamental role in binomial nomenclature , the system of naming organisms , where it is combined with the scientific name of

4033-594: The Katian of Ohio: M. shideleri and M. williamsae . M. shideleri was named based on fragmentary fossil specimens originally found by William H. Shideler in the Saluda Formation near Oxford, Ohio , and in Indiana . The species is named in his honor. M. shideleri differs from M. ohioensis in that its gnathobases have fewer denticles and a much more developed second tooth. The M. shideleri fossils could not be compared to

4142-869: The Katian-age deposits of the Whitewater Formation near Oxford, Ohio, referring these specimens to Megalograptus . In 2002, fossils belonging to a small variety of Megalograptus were first reported from Katian-age deposits of the Nicolet River Formation in Quebec, Canada. Megalograptus fossils found in Katian-age deposits in the US state of Georgia and in the Shawangunk Ridge of New York may also represent two distinct new species. Additionally, fossils potentially referrable to Megalograptus have been reported from

4251-516: The Megalograptidae since 1955. In 2015, the genus Pentecopterus was also assigned to the family. Kenneth E. Caster and Erik N. Kjellesvig-Waering revised Megalograptus in 1955, owing to the discovery of more complete fossil material of the new species M. ohioensis . Caster and Kjellesvig-Waering conducted further work on Megalograptus over the following years. In 1964, they named the species M. shideleri and M. williamsae and reclassified

4360-415: The appendages of larger specimens, including the spiny and large forelimbs, were almost entirely black in color and with black spines, although in smaller specimens, the appendages were typically lighter in color. Connective tissue in the appendages was pale brown in color. The appendage immediately preceding the swimming paddles was not entirely black, instead just darkening to a very dark brown. The metastoma

4469-533: The appendages, the scaly ornamentation and the longitudinal ridges of the preserved segment. Foerste also noted that the fossils of M. welchi were not morphologically distinct enough from other eurypterids to differentiate it, with its earlier age instead serving as the main distinction of the genus and species. Megalograptus was considerably revised in 1955 by Caster and Kjellesvig-Waering in Leif Størmer 's 1955 Treatise on Invertebrate Paleontology , from which

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4578-442: The base for higher taxonomic ranks, such as the family name Canidae ("Canids") based on Canis . However, this does not typically ascend more than one or two levels: the order to which dogs and wolves belong is Carnivora ("Carnivores"). The numbers of either accepted, or all published genus names is not known precisely; Rees et al., 2020 estimate that approximately 310,000 accepted names (valid taxa) may exist, out of

4687-579: The body was preserved were removed). Tetlie speculated that Megalograptus and its family could be very basal, given their early age, retaining Megalograptoidea as a distinct superfamily, though with a highly uncertain phylogenetic position, either very basal, between the Onychopterelloidea and the Eurypteroidea, or more derived, between the Eurypteroidea and the Mixopteroidea. No phylogenetic analysis ever recovered Megalograptus in these positions and

4796-410: The characteristic may become exaggerated due to sexual selection. The females will select for more and more elaborate ornamentation, which represents better survival skills because the male with those characteristics must be physically fit enough to handle the unwanted predator attention that comes with the ornament. Therefore, the males with the most extreme ornamentation will have more offspring, and

4905-405: The competition for mates. The interesting thing about sexual ornaments is that they impede the male's chances for survival, yet they continue to be passed on from generation to generation. The larger the male peacock's tail feathers are, or the brighter the birds feathers are, the harder it is for them to escape predators and maneuver through trees, and the more food they will need to eat to develop

5014-410: The coxal gnathobases, so that the second pair then could rip the immobilized prey. The fourth pair of appendages were short and spiny, but the fifth pair, immediately preceding the swimming paddles (placed on the sixth and final pair of appendages), were completely spineless. This unusual limb is similar to the same appendage in the distantly related genus Eurypterus , where it has been interpreted as

5123-613: The evolution of ornaments in males that reliably reveal the level of oxidative stress in potential mating partners. Ornamentation is a common biological trait seen in birds. The male quetzal has elaborate ornamentation to aid in mating. Male quetzals have iridescent green wing coverts, back, chest and head, and a red belly. During mating season, male quetzals grow twin tail feathers that form an amazing train up to three feet long (one meter) with vibrant colors. Most female quetzals have no ornamentation and are drab. Coloration and tail feather length in quetzals help determine mate choice because

5232-449: The females choose the more elaborately ornamented males. Other birds that exhibit ornamentation include sage grouses and widowbirds . Sage grouse birds gather in a lek , or a special display area, and strut and display their plumage to attract a mate. Whereas, the extraordinary tail feathers of the male long-tailed widowbird are displayed to choosy females while the male flies above his grassland territory. Biological ornamentation

5341-446: The form "author, year" in zoology, and "standard abbreviated author name" in botany. Thus in the examples above, the genus Canis would be cited in full as " Canis Linnaeus, 1758" (zoological usage), while Hibiscus , also first established by Linnaeus but in 1753, is simply " Hibiscus L." (botanical usage). Each genus should have a designated type , although in practice there is a backlog of older names without one. In zoology, this

5450-443: The fossil site had irreversibly damaged what remained of the eurypterid fossils. The status of Megalograptus as a graptolite was first questioned in 1908 by Rudolf Ruedemann , who was researching Ordovician graptolites. Ruedemann instead recognized the remains of M. welchi as eurypterid fossils. That same year, Ruedemann's suspicions were confirmed in discussions with August Foerste and Edward Oscar Ulrich , who also agreed that

5559-404: The fossils were of a eurypterid. Foerste was invited to contribute with his understanding of Megalograptus to Ruedemann's and John Mason Clarke 's 1912 monograph The Eurypterida of New York . He recognized Megalograptus as similar to the eurypterid Echinognathus clevelandi , assuming them to either be related or of the same genus. The features uniting the two were noted to be the spines of

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5668-529: The fragmentary eurypterid Ctenopterus alveolatus as a species of Megalograptus . Megalograptus lived in near-shore marine environments, where it used its large appendages, and possibly its telson and cercal blades, to capture prey. Possible coprolites (fossilized dung) are known from M. ohioensis , which contain fossil trilobite fragments as well as fragments of M. ohioensis itself. This suggests that Megalograptus might have been cannibalistic at times, like many modern chelicerates . Megalograptus

5777-527: The gene for "showiness" will be passed on. This evolution can then lead to organs of excessive size that may become troublesome for the males, such as large, bushy tails, bright feathers, etc. The point of equilibrium is reached when their ornamentation becomes too much of a handicap on the male's survival, and the "vital" natural selection goes to work, altering the exaggerated characteristic until it reaches an equilibrium point. Sexually selected ornaments of males may impose survival costs but advance success in

5886-677: The generic name (or its abbreviated form) still forms the leading portion of the scientific name, for example, Canis lupus lupus for the Eurasian wolf subspecies, or as a botanical example, Hibiscus arnottianus ssp. immaculatus . Also, as visible in the above examples, the Latinised portions of the scientific names of genera and their included species (and infraspecies, where applicable) are, by convention, written in italics . The scientific names of virus species are descriptive, not binomial in form, and may or may not incorporate an indication of their containing genus; for example,

5995-425: The genus was often excluded from analyses due to its perceived strange mix of features. The description of Pentecopterus , the only other genus in the Megalograptidae, in 2015 by Lamsdell and colleagues saw the megalograptids again considered to be close relatives of the mixopterids and carcinosomatids. The phylogenetic analysis accompanying the description of the new genus resolved the Megalograptidae as basal within

6104-453: The highest genetic quality can produce the most impressive tails. The tail of a peafowl is an honest signal for the female in determining the health status of a potential mate. In 1982, William Hamilton and Merlene Zuk proposed that male ornaments may enable healthy males to advertise the fact that they are free of diseases and parasites, a theory that is now known as the "Bright Male" hypothesis. According to this hypothesis, if an animal

6213-432: The idea that a newly defined genus should fulfill these three criteria to be descriptively useful: Moreover, genera should be composed of phylogenetic units of the same kind as other (analogous) genera. The term "genus" comes from Latin genus , a noun form cognate with gignere ('to bear; to give birth to'). The Swedish taxonomist Carl Linnaeus popularized its use in his 1753 Species Plantarum , but

6322-448: The idea that elaborate male ornaments allow females to assess the 'quality' of a male's genes so that she can ensure that her offspring get the best genes (health, physical vigor, etc.). In 1975, Amotz Zahavi proposed the handicap principle , which is the idea that elaborate male ornaments are actually a handicap and that males with such ornaments are demonstrating their physical quality by showing that they can survive despite having such

6431-628: The integument (the scales) was a lighter brown color. A similar, but darker, brown and black color scheme has been inferred for M. ohioensis , and its fossils being better preserved allows for more detailed examination. M. williamsae also had a similar color scheme, with its tergites indicating black scales against light brown integument. The colors of Megalograptus inferred by Caster and Kjellesvig-Waering are similar to those inferred by Kjellesvig-Waering of Carcinosoma newlini , another eurypterid also inferred to have been brown and black, in 1958. According to Caster and Kjellesvig-Waering, M. ohioensis

6540-418: The intensity of the expression of ornamentation in males reflects their level of oxidative stress . It is considered that female choice may select for traits in males that reliably indicate level of oxidative stress, as such traits would be a good indicator of male quality Elevated oxidative stress can lead to increased DNA damage that can contribute to aging or cancer . Female choice thus may promote

6649-628: The largest component, with 23,236 ± 5,379 accepted genus names, of which 20,845 ± 4,494 are angiosperms (superclass Angiospermae). By comparison, the 2018 annual edition of the Catalogue of Life (estimated >90% complete, for extant species in the main) contains currently 175,363 "accepted" genus names for 1,744,204 living and 59,284 extinct species, also including genus names only (no species) for some groups. The number of species in genera varies considerably among taxonomic groups. For instance, among (non-avian) reptiles , which have about 1180 genera,

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6758-419: The length of the carapace, were significantly larger than those of Mixopterus . On the fourth joint of the appendages, one pair of spines end in bulbous structures, rather than sharp points, and were perhaps sensory. This third pair, presumably used for seizing and constraining prey, had notable flexibility, indicating that its hypertrophied spines would have been used to hold prey and bring them to chelicerae and

6867-402: The life coloration of the species based on a collection of well-preserved specimens. In some fossils of M. shideleri , the fossils retained their original coloration, with no replacement having taken place (meaning that mineralization during fossilization did not distort the original color scheme of the fossils). M. shideleri was brown, with scales varying in color from dark brown to black and

6976-420: The lizard genus Anolis has been suggested to be broken down into 8 or so different genera which would bring its ~400 species to smaller, more manageable subsets. Biological ornament A biological ornament is a characteristic of an animal that appears to serve a decorative function rather than a utilitarian function. Many are secondary sexual characteristics , and others appear on young birds during

7085-511: The main body, the scales were rounded, raised and nearly elliptical in shape. Many of the scales on the carapace, the fifth pair of appendages, the mesosoma and metasoma and some on the appendages had holes in their center, suggesting that they once supported bristles (stiff hairs). In life, Megalograptus may have had an almost hirsute (hairy) appearance. In the 1964 description of M. ohioensis , M. shideleri and M. williamsae , Kenneth E. Caster and Erik N. Kjellesvig-Waering made inferences of

7194-466: The mesosomas of other eurypterids. The body contracted after the last segment of the mesosoma, rather than after the first segment of the metasoma (the last six segments), which was otherwise typical for eurypterids. In most eurypterids, the mesosoma was widest at the fourth or fifth segment, but in Megalograptus it was widest at the third. The first segment of the mesosoma was considerably shorter than

7303-400: The mistaken original belief that Megalograptus was a type of graptolite , often given names ending with - graptus (meaning 'writing'). Megalograptus was a large predatory megalograptid eurypterid, with the largest and best known species, M. ohioensis , reaching body lengths of 78 centimeters (2 ft 7 in). Some species were substantially smaller, with the smallest, belonging to

7412-465: The modern understanding of the genus originates. The revision was made possible with the discovery of new fossil material, consisting of what at the time was the best preserved Ordovician eurypterid fossil material discovered. These fossils, found in deposits of Katian age alongside the Ohio River road (U.S. Route 52), approximately 14.5 kilometres (9.0 mi) north of Manchester, Ohio , were assigned to

7521-653: The more acute, hooked and stouter end points in M. ohioensis . The species M. alveolatus was originally named as a species of the very distantly related Ctenopterus by Ellis W. Shuler in 1915, based on fossil fragments, including of the appendages and the telson spike, collected in Late Ordovician deposits along Walker Mountain in Virginia belonging to the Bays Formation . It was the first eurypterid to be described from Virginia. The species name alveolatus refers to

7630-543: The morphology of the appendage described by Shuler in 1915 demonstrated that the fossils undoubtedly belonged to Megalograptus . M. alveolatus was kept as a distinct species on account of the third joint of the appendage being proportionally larger than the same joint in M. ohioensis . In addition to the five described species assigned to the genus, there may be as many as four distinct undescribed species of Megalograptus . Caster and Kjellesvig-Waering noted in 1964 that there were very fragmentary eurypterid fossils known from

7739-403: The most (>300) have only 1 species, ~360 have between 2 and 4 species, 260 have 5–10 species, ~200 have 11–50 species, and only 27 genera have more than 50 species. However, some insect genera such as the bee genera Lasioglossum and Andrena have over 1000 species each. The largest flowering plant genus, Astragalus , contains over 3,000 species. Which species are assigned to a genus

7848-428: The name could not be used for both. Johann Friedrich Blumenbach published the replacement name Ornithorhynchus in 1800. However, a genus in one kingdom is allowed to bear a scientific name that is in use as a generic name (or the name of a taxon in another rank) in a kingdom that is governed by a different nomenclature code. Names with the same form but applying to different taxa are called "homonyms". Although this

7957-931: The ornament. A peacock's tail almost certainly reduces survival of the peacock as they reduce maneuverability, power of flight, and make the bird more conspicuous to predators. Ornaments, therefore, have a great effect on the fitness of the animals that carry them, but the benefits of having an ornament must outweigh the costs for them to be passed on. Biological ornamentation has been shown to affect parental favoritism in nestlings. This can be observed several species of water birds. For example, baby American coots hatch out with long, orange-tipped plumes on their backs and throats which provide signals to parents used to determine which individuals to feed preferentially. In experiments in which ornaments have been physically altered on baby coots, elaborate ornamentation has been proven to be beneficial to young offspring. Ornamented individuals received more frequent feedings from parents. Therefore,

8066-465: The others. First described by Samuel Almond Miller in 1874, based on fragmentary fossil remains of the species M. welchi , Megalograptus being a graptolite was not formally questioned until 1908, when Rudolf Ruedemann recognized the fossils as eurypterid remains. Megalograptus was noted as being similar to Echinognathus by August Foerste in 1912 and the two genera have been considered closely related since then, and have been grouped together in

8175-481: The period when they are dependent on being fed by their parents. Ornaments are used in displays to attract mates , which may lead to the evolutionary process known as sexual selection . An animal may shake, lengthen, or spread out its ornament in order to get the attention of the opposite sex, which will in turn choose the most attractive one with which to mate . Ornaments are most often observed in males, and choosing an extravagantly ornamented male benefits females as

8284-543: The presence and characteristics of the ornament, and second it develops from genes in females that draw her to this kind of ornamentation. Important studies concerning this have been conducted in the Stalk-eyed fly , showing that females are attracted to mates that share characteristics with their fathers. Therefore, sexual selection is a mechanism that differently affects both sexes. Initially, an ornament may have been selected for reasons not linked to reproduction, but over time,

8393-509: The presence of ornaments. Darwin was the first to correctly hypothesize that sexual selection by female choice was responsible for the evolution of elaborate plumage and remarkable displays in male birds such as the quetzal and the sage grouse . Sexual selection is selection acting on variation among individuals in their ability to obtain access to mating partners. In his 1871 book The Descent of Man, and Selection in Relation to Sex , Darwin

8502-433: The pronounced development of the alveolar processes (pits) around the spines. Because of the fragmentary state of its fossils, M. alveolatus has had a complex taxonomic history. Although Kjellesvig-Waering initially believed that it might have been a species of Mixopterus , tentatively designating it as " Mixopterus (?) alveolatus ", Caster and Kjellesvig-Waering assigned the species to Megalograptus in 1964, arguing that

8611-526: The provisions of the ICZN Code, e.g., incorrect original or subsequent spellings, names published only in a thesis, and generic names published after 1930 with no type species indicated. According to "Glossary" section of the zoological Code, suppressed names (per published "Opinions" of the International Commission of Zoological Nomenclature) remain available but cannot be used as the valid name for

8720-675: The relative growth rates of ornamented chicks were much higher compared with the experimentally altered chicks. Male animals are typically more elaborately ornamented than females. The classic sexual selection theory notes that because sperm are cheaper to produce than eggs, and because males generally compete more intensely for reproductive opportunities and invest less in parental care than females, males can obtain greater fitness benefits from mating multiple times. Therefore, sexual selection typically results in male-biased sex differences in secondary sexual characteristics , which are non-reproductive body parts that help distinguish between sexes in

8829-877: The relatively derived Carcinosomatoidea superfamily, which also includes the Carcinosomatidae and Mixopteridae. The cladogram below is simplified from the study by Lamsdell et al. (2015), collapsed to only display the Carcinosomatoidea. Pentecopterus decorahensis Echinognathus clevelandi Megalograptus williamsae Megalograptus ohioensis Megalograptus welchi Lanarkopterus dolichoschelus Mixopterus kiaeri Mixopterus multispinosus Holmipterus suecicus Rhinocarcinosoma vaningeni Carcinosoma newlini Carcinosoma libertyi Eusarcana acrocephalus Eusarcana scorpionis Discovered alongside specimens of M. ohioensis were tube-like structures containing fossil fragments of

8938-510: The size estimate was based only on two fragmentary tergites (upper portions of body segments ), wherein the dimensions of the ornamental scales were unusually large, interpreted as suggesting a giant body size. The fact that scales can vary in size across the bodies of megalograptid eurypterids and that one of the relevant tergites of M. shideleri was not longer than 3 cm (1.2 in) suggests that this species did not reach lengths of more than 56 cm (1 ft 10 in). The length of

9047-449: The size of some species of Megalograptus as substantially larger, with the type species M. welchi once believed to have reached lengths of 150 cm (4 ft 11 in) in length. According to a 2009 study by James Lamsdell and Simon J. Braddy, such estimates are dubious as they are based on ornamentation in incomplete fossils. In the case of M. shideleri , once estimated to have reached lengths of 200 cm (6 ft 7 in),

9156-444: The species M. alveolatus is uncertain, but it was much smaller than M. ohioensis , and M. williamsae grew to about 50 cm (1 ft 8 in). The smallest known species of Megalograptus was an as yet undescribed Canadian species which only grew to 10 cm (3.9 in) in length. Megalograptus was morphologically unique and easily distinguishable from other eurypterids. The carapace (head plate) of Megalograptus

9265-495: The species distinction of M. welchi and M. ohioensis , including the leg of M. welchi being stouter, with thicker and shorter spines, and some differences in the joints (in M. welchi , the second joint had spines, which it did not in M. ohioensis , and in M. welchi , the spine-shaped ultimate joint was blunt and thick, whereas it was slender in M. ohioensis ). In 1964, Caster and Kjellesvig-Waering named two new species of Megalograptus based on additional fossil material from

9374-488: The species name welchi honors, near Liberty, Ohio , in rocks of Katian (Late Ordovician) age of the Elkhorn Formation . With the exception of the type material, M. welchi is only fragmentarily known. It is probable that more fossils could have been uncovered if it had been immediately recognized as a large eurypterid. By the time it was recognized as such and the fossils were deemed to be of interest, further work at

9483-497: The specific name particular to the wolf. A botanical example would be Hibiscus arnottianus , a particular species of the genus Hibiscus native to Hawaii. The specific name is written in lower-case and may be followed by subspecies names in zoology or a variety of infraspecific names in botany . When the generic name is already known from context, it may be shortened to its initial letter, for example, C. lupus in place of Canis lupus . Where species are further subdivided,

9592-557: The spider captures the bee in its nest and reaps the food benefits. In this case, what may seem as an ornament to attract mates is actually used as a lure to trap food. Armaments are anatomical weapons which have evolved amongst species whose males compete intra-sexually for access to females. Armaments are used in direct contests for the opportunity to mate or for the resources needed to attract mates. These weapons such as tusks, antlers, horns, spurs, and lips increase success in rivalry among competitors to gain or maintain dominance, control

9701-533: The sponge Brachiospongia and various crinoids, such as Glyptocrinus and Dendrocrinus . M. alveolatus occurred with a typical Late Ordovician fauna, including brachiopods, such as Orthorhynchula , and bivalves , such as Byssonychia . Genus The composition of a genus is determined by taxonomists . The standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. There are some general practices used, however, including

9810-412: The standard format for a species name comprises the generic name, indicating the genus to which the species belongs, followed by the specific epithet, which (within that genus) is unique to the species. For example, the gray wolf 's scientific name is Canis lupus , with Canis ( Latin for 'dog') being the generic name shared by the wolf's close relatives and lupus (Latin for 'wolf') being

9919-422: The succeeding segments, which were otherwise approximately of the same length. The last few segments of the body were slightly longer than the preceding segments. The metastoma (a large plate located on the underside of the body) of Megalograptus was roughly egg-shaped, unusually wide and broadly subtriangular (almost triangular) in shape, differentiating it from the same structure in all other eurypterids, where it

10028-498: The superfamily Mixopteracea (later renamed to Mixopteroidea). In 1989, Victor P. Tollerton, perceiving them to be distinct enough, placed the Megalograptidae into their own superfamily, the Megalograptoidea. In 2004, O. Erik Tetlie determined Megalograptus , and by extension the Megalograptidae, to be taxonomically problematic, perceiving the genus to share several potential synapomorphies ( derived , "advanced", traits unique to

10137-403: The taxon is termed a synonym ; some authors also include unavailable names in lists of synonyms as well as available names, such as misspellings, names previously published without fulfilling all of the requirements of the relevant nomenclatural code, and rejected or suppressed names. A particular genus name may have zero to many synonyms, the latter case generally if the genus has been known for

10246-421: The telson–pretelson assemblage of Megalograptus forms a flattened structure, superficially similar to the flattened telsons of many genera in the superfamily Pterygotioidea . Megalograptus was ornamented with small scales of irregular size across its body. On the carapace, they were flat and disc-like and scattered without any obvious pattern. On the fifth pair of appendages, the scales were more elongated. On

10355-532: The type material of M. welchi as there is no overlap in the preserved body parts. M. williamsae was named based on a cercal blade, alongside fragments of tergites and appendages, discovered in the Waynesville Formation , near Clarksville, Ohio , by Carrie Williams, whom the species name honors. M. williamsae differs from M. ohioensis in its cercal blades, with a slightly different pattern of scales and longer, narrower and sharper end points, rather than

10464-566: The values quoted are the mean of "accepted" names alone (all "uncertain" names treated as unaccepted) and "accepted + uncertain" names (all "uncertain" names treated as accepted), with the associated range of uncertainty indicating these two extremes. Within Animalia, the largest phylum is Arthropoda , with 151,697 ± 33,160 accepted genus names, of which 114,387 ± 27,654 are insects (class Insecta). Within Plantae, Tracheophyta (vascular plants) make up

10573-429: The virus species " Salmonid herpesvirus 1 ", " Salmonid herpesvirus 2 " and " Salmonid herpesvirus 3 " are all within the genus Salmonivirus ; however, the genus to which the species with the formal names " Everglades virus " and " Ross River virus " are assigned is Alphavirus . As with scientific names at other ranks, in all groups other than viruses, names of genera may be cited with their authorities, typically in

10682-489: Was a genus of large megalograptid eurypterids . The largest species was M. ohioensis , which ranged in length from 49 to 78 centimeters (1 ft 7 in to 2 ft 7 in). M. ohioensis was the second largest megalograptid and the second largest eurypterid of the Ordovician period, smaller only than the related Pentecopterus , which could grow to 170 cm (5 ft 7 in). Previous estimates have placed

10791-541: Was amended by Erik N. Kjellesvig-Waering in 1955, who transferred Mixopterus to its own family, the Mixopteridae , and placed Megalograptus and Echinognathus in their own family, the Megalograptidae. The Megalograptidae has traditionally been interpreted as closely related to the Mixopteridae. In 1964, Caster and Kjellesvig-Waering placed Megalograptidae, alongside Mixopteridae, Carcinosomatidae and Mycteroptidae , into

10900-413: Was dark brown, with black scales, postules (small elevations) and mucrones (tiny spines). The telson of M. ohioensis , as well as much of the preceding segment, was entirely black in color. Fossils of Megalograptus were first described by Samuel Almond Miller in 1874. Miller mistakenly believed the fossil material, consisting of a postabdominal (segments 8–12) tergite and two fragments of an appendage,

11009-454: Was diseased, it would not be able to grow such beautifully colored plumage. Since disease is a major source of juvenile mortality, females would choose the males with the most elaborate ornaments to ensure that they will have healthy offspring. Females may improve survival of offspring by selecting mates on the basis of ornamentation signals that honestly reveal health. Numerous studies have been carried out to test if sexual selection based on

11118-445: Was mostly dark brown, with some black elements. Though no obvious integument pattern has been determined, most of the body, including the head, had dark brown integument, contrasted by black scales. The coxae (base segments of the appendages) were dark brown, with black scales and black gnathobases ("tooth plates" surrounding the mouth). As such, the appendages began as dark brown in color, but quickly darkened towards their ends. Most of

11227-423: Was not venomous , but it was specialized in that it was surrounded by unique cercal blades, capable of grasping. Certain fossils of three different species, M. ohioensis , M. shideleri and M. williamsae , are so well-preserved that researchers have been able to infer the coloration they might have possessed in life. All three were deduced to have been brown and black in color, with M. ohioensis being darker than

11336-444: Was perplexed by the elaborate ornamentation that males of some species have because they appeared to be detrimental to survival and have negative consequences for reproductive success. Darwin proposed two explanations for the existence of such traits: these traits are useful in male-male combat or they are preferred by females. More recently, many alternative theories of sexual selection have been proposed, many of them centered around

11445-436: Was predatory, as they were presumably used for active prey capture, to grasp prey and move it to the mouth. The third pair of appendages were possibly also used for sensory functions, for combats between males, or for display such that the largest third pair with indication of high fitness level would have attracted females. The cercal blades of Megalograptus are believed to have been a considerable aid when swimming, acting like

11554-415: Was similar, consisting of cephalopods , bryozoans, gastropods and scolecodonts. M. williamsae was recovered in a so-called "trilobite bed", alongside several different trilobite species. The fossils of M. welchi were recovered in a crinoid fossil site otherwise popular with fossil hunters. Other fossil fauna known from the fossil site of M. welchi include the trilobites Ceraurus and Dalmanites ,

11663-562: Was the integument of a graptolite (a member of Graptolithina, an extinct group of colonial pterobranchs ), and gave it the name Megalograptus , meaning "great writing" (deriving from the Greek megale , "great", and graptos , "writing", commonly used for graptolite fossils). One reason for Miller's mistaken identification is that the exact outline of the fossils was unclear because they were not properly cleaned yet. The fragmentary fossils of M. welchi were initially recovered by L. B. Welch, whom

11772-472: Was usually cordate (heart-shaped). The most unusual feature of Megalograptus was the structure formed by the telson (the last division of the body) and the immediately preceding segment (the pretelson). Megalograptus had, alongside the sharp and stout telson spike, two paired and rounded blade-formed lobes, the so-called cercal blades. These were attached beneath the telson, directly to the pretelson. The blades were capable of articulation, in effect forming

11881-449: Was vaguely quadratic in shape and flattened, lacking a marginal rim, which was present in some other eurypterids. At the front of the carapace there was a downturn and six small downward-facing spikes, possibly an adaptation for digging in the mud. The compound eyes of Megalograptus were medium-sized and reniform (kidney-shaped), located close to the edge of the carapace. The ocelli (simple eyes located more centrally) were small. Some of

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