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46-437: 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 members of the superfamily Pterygotioidea , in contrast with the more derived (more "advanced") families Pterygotidae and Slimonidae . Despite their classification as pterygotioids,

92-429: A eurypterid family classified in the superfamily Pterygotioidea that is differentiated by their streamlined bodies, the enlargement of their medium-sized chelicerae and the presence of paired spines on the walking appendages . With the biggest specimen measuring 20 centimetres (8 inches) in length, Hughmilleria is considered a eurypterid of small size. Hughmilleria is the most basal (primitive) known member of

138-526: A Scottish geologist and writer who found fossils of eurypterids of the Silurian, among them Hughmilleria . A variety of H. socialis was also described, Hughmilleria socialis var. robusta , but currently it is considered a synonym of the species mentioned. Four years later, a second species was discovered among the fauna of the Shawangunk grit at Otisville . It was described as Hughmilleria shawangunk and

184-518: A family of their own. Slimonia was considered too distinct from Hughmilleria in 1962, placed by Nestor Ivanovich Novojilov in its own family, the Slimonidae. The other hughmilleriids would also be reclassified, Hastimima representing a mycteroptidae and Grossopterus a waeringopterid . This left Hughmilleria as the only genus in the family, rendering it monotypic (including only one subordinate taxon). Hughmilleriidae remained monotypic until

230-519: A keel and marginal ornamentation, characteristics also noted within Pterygotidae. The lanceolate shape of their telsons suggests they did not use it as a rudder to swim. The family is characterized by the presence of spines in the second to fifth pair of appendages, swimming legs with the 7th and 8th leg segments narrow, both twice as long as wide, and the 9th segment small, small and streamlined bodies, slightly enlarged chelicerae (frontal appendages) and

276-728: A marginal rim in the carapace much broader anteriorly than posteriorly. The genus Hughmilleria was erected by Clifton J. Sarle in 1903 to contain the species H. socialis , which was recovered for the first time in the Pittsford Shale Member of the Vernon Formation . The generic name derives from Hugh Miller , a Scottish geologist and writer that found fossils of several Silurian eurypterids, such as Hughmilleria itself. Sarle considered Hughmilleria as an intermediate form between Eurypterus and Pterygotus . However, he did not assigned Hughmilleria to any family. Hughmilleria

322-465: A slightly wider carapace than in the other species. Measuring 6 cm (2 in) in length, H. wangi is the smallest known species of Hughmilleria and of the Pterygotioidea superfamily. In addition, if the problematic H. lanceolata , which has been suggested by some researchers to belong to this genus, really did so, it would extend the range of Hughmilleria to the Silurian of Scotland. It

368-552: A species of Hughmilleria , H. banksii , was raised to the level of a separate genus, Herefordopterus , by O. Erik Tetlie in 2006. With two genera of hughmilleriids known, several diagnostic traits of the family could properly be established, such as the presence of spiniferous appendages. The Hughmilleriidae are classified as part of the Pterygotioidea superfamily, within the Diploperculata infraorder and Eurypterina suborder. The Hughmilleriidae has sometimes been interpreted as

414-436: A subtriangular carapace outline with the pterygotids and the wide telson and genital appendages of all three taxa were similar, although the genital appendages of Hughmilleria and Herefordopterus were more similar to those of Slimonia by the division of these into three segments, in contrast to the undivided morphology in the pterygotids. Still, Hughmilleria and Herefordopterus differed from pterygotids and slimonids by

460-435: A wide array of different eurypterids, like Erettopterus gigas , Eurypterus cephalaspis , Nanahughmilleria pygmaea , Marsupipterus sculpturatus , Salteropterus abbreviatus and potentially Slimonia (depending on the identity of S. stylops ). Hughmilleria Hughmilleria is a genus of eurypterid , an extinct group of aquatic arthropods . Fossils of Hughmilleria have been discovered in deposits of

506-418: Is distinctly a Eurypterus -like feature. The marginal compound eyes , the relatively large chelae and the cordate (heart-shaped) metastoma (a large plate that is part of the abdomen) show a great resemblance to Pterygotus . The carapace was parabolic or subquadrate with oval marginal eyes, the chelicerae were able to extend beyond the carapace margin and the appendages II–V were spiniferous. The genus

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552-641: Is in honor of Junqing Wang, who found the fossil of the species in 1992. This species was recovered from the Xiaoxiyu Formation of Hunan, in deposits that suggest that it lived in the Telychian age of the Silurian, which makes it the oldest eurypterid discovered in China. H. wangi differs from the North American species by the presence of epimera (lateral "extensions" of the segment) on the entire postabdomen and

598-469: Is in various ways similar to the more derived eurypterids of its superfamily, the Pterygotioidea, however, it lacked the expanded and flattened telson that the pterygotids and Slimonia had. This suggests that Hughmilleria did not need to use the telson as a rudder to swim. Hughmilleria is distinguished from other members of Pterygotioidea by its streamlined body, its subquadrate prosoma (head), its medium-sized chelicerae, its small overall size and

644-809: Is within the Salina from western Pennsylvania and New York on west. In the central part of theses states on east in is the lowest member of the Wills Creak. This difference again is due to erosional clastic material moving westward from the Taconic Highlands. In the East or Wills Creak area, the Middle Vernon has occasional red shales, particularly in the southeast. Generally, however it is predominantly green shale, with interbedded dolomite and siltstone. Moving west dolomite replaces shale and anhydrite becomes prevalent. Within

690-614: The Llandovery and Ludlow epochs . Together with its close relatives, Hughmilleria dominated the communities in brackish and fresh water , while Pterygotus and Eurypterus dominated marine environments. The Silurian deposits of the Pittsford Shale Member in which fossils of H. socialis have been found shelter various faunas of eurypterids, including Mixopterus multispinosus , Erettoperus osiliensis , Eurypterus pittsfordensis and Carcinosoma spiniferus , among others. Fossils from other organisms were also found, such as

736-482: The Pterygotioidea . It was a small-sized eurypterid, with the largest specimen measuring 20 cm (8 in), being surpassed by other members of its superfamily, such as Slimonia acuminata , which measured 100 cm (39 in) in length, and Pterygotus grandidentatus , which could reach 1.75 meters (5 ft 8 in). The telson (the most posterior segment of the body), which was lanceolate and styliform,

782-608: The Silurian age in China and the United States . Classified as part of the basal family Hughmilleriidae , the genus contains three species, H. shawangunk from the eastern United States , H. socialis from Pittsford, New York , and H. wangi from Hunan , China . The genus is named in honor of the Scottish geologist Hugh Miller . H. socialis is the type species of Hughmilleriidae ,

828-589: The crustacean Ceratiocaris and the ostracod Leperditia . Geological features of the formation, such as the friable and calcareous mudstone , the argillaceous dolomite and the lithology and associated biota suggests that the environment was marginal marine, very shallow and probably brackish. Vernon Formation The Vernon Formation mostly is within the Salina Group. However, in Central Pennsylvania and Central New York onward East

874-490: The pterygotids which would surpass lengths of 2 metres and become the largest known arthropods to ever live. Like all other chelicerates , and other arthropods in general, the hughmilleriid eurypterids possessed segmented bodies and jointed appendages (limbs) covered in a cuticle composed of proteins and chitin . The chelicerate body is divided into two tagmata (sections); the frontal prosoma (head) and posterior opisthosoma (abdomen). The appendages were attached to

920-507: The Lower Vernon is further into two units the A1 and A2. Each unit has a lower division of evaporite (salt or anhydrite) and the upper section is a carbonate, typically dolomite. In the east the Lower Vernon contains predominantly red shale. Moving west this is gradually replaced with green shale, then grey shale. Finally dolomite, anhydrite and halite in the western extent. The Middle Vernon (Unit B)

966-463: The Pittsford Shale Member in which fossils of Hughmilleria socialis have been found shelter various faunas of eurypterids, including Mixopterus multispinosus , Erettoperus osiliensis , Eurypterus pittsfordensis and Carcinosoma spiniferus , among others. In the other hand, the Late Silurian of Herefordshire , where most of the fossils of Herefordopterus have been discovered, was home to

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1012-408: The Pterygotidae. In 1961, Erik N. Kjellesvig-Waering split Hughmilleria into two subgenera , Hughmilleria ( Hughmilleria ) and Hughmilleria ( Nanahughmilleria ), although Nanahughmilleria would be later raised to the genus level. In 2007, a new species of Hughmilleria from Hunan, China, was described as H. wangi based on an almost complete specimen (CNU-E-HLT2006001). The specific name

1058-561: The Salina parts of the formation there may be up to seven distinct salt beds. The base of the Middle Vernon is marked in the Salina by the last salt bed, and a slight overall rise in gamma. With in the Wills Creek area, it is marked by a general overall rise in gamma. The Upper Vernon, is composed of shale and siltstone. Red and green shale to the east with grey and green to the west. In western Pennsylvania dolomite and anhydrite appear. Generally evaporites are not common in this section. The base

1104-470: The Slimonidae was more closely related to the Pterygotidae than the Hughmilleriidae was, establishing Hughmilleriidae as the most basal group of pterygotioid eurypterids. The family has been recovered as paraphyletic in a number of phylogenetic analyses and does thus not form an actually valid scientific grouping. Nevertheless, the family is retained and routinely used by eurypterid researchers. Within

1150-619: The Taconic Highlands slowly filling the basin. In the west the basin was filled with carbonates and shales. The Base of the Vernon is marked in the west typically by a sharp drop in gamma logs. This is due to the disappearance of shale and moving into a crystalline near pure carbonite unit. The would be either the Lockport or the Guelph dolomites, depending on location. Within the Michigan Basin and Ohio

1196-519: The Vernon is part of both the Wills Creek and Bloomsburg due to erosional deposits migrating from the east. Lower Vernon (or Unit A) is the base of both the Vernon and Salina in western Pennsylvania and New York, continuing into Ohio and Michigan. In north central Pennsylvania and central New York it is a part of the Bloomsburg. The Bloomsburg is an ancient delta system carrying sediment westward from

1242-732: The adelophthalmid eurypterid Eysyslopterus , indicating that it might be a plesiomorphic trait (a trait present in a common ancestor). The cladogram presented below, derived from a 2007 study by researcher O. Erik Tetlie, showcases the interrelationships between the pterygotioid eurypterids. Hughmilleria wangi Hughmilleria socialis Hughmilleria shawangunk Herefordopterus banksii Slimonia acuminata Ciurcopterus ventricosus Pterygotus anglicus Jaekelopterus rhenaniae Acutiramus macrophthalmus Acutiramus bohemicus Erettopterus bilobus Erettopterus serricaudatus Erettopterus osiliensis Erettopterus waylandsmithi The fossils of

1288-445: The derived features that would come to evolve in the Slimonidae and Pterygotidae, such as flattened and expanded telsons (the posteriormost segment of the body, this feature is shared by both derived families) and enlarged cheliceral claws (exclusive to the pterygotids). In spite of the great similarity of both genera, Herefordopterus had derived characteristics that suggest a close relationship with Slimonidae and Pterygotidae, such as

1334-417: The eyes and the relatively large chelae . However, by its cordate metastoma , the intramarginal to marginal position of the compound eyes , the slightly longer preoral appendages, less developed swimming legs and the opercular appendage, Hughmilleria was more like Pterygotus . The cladogram presented below, derived from a 2007 study by researcher O. Erik Tetlie, showcases the interrelationships between

1380-416: The family, both genera shared several characteristics such as the carapace being much broader anteriorly than posteriorly , appendages II-V being spiniferous (possessing spines), swimming legs similar to those of Hughmilleria itself, the slight enlargement of their chelicerae and their small and streamlined bodies. However, the marginal ornamentation of the telson and the possession of 12-13 gnathobasic (of

1426-454: The gnathobase, a lower appendage used in feeding) teeth in the appendage VI suggests that Herefordopterus was a derived hughmilleriid. In turn, Hughmilleria lacked the marginal ornamentation of the telson and its appendage VI had 18-20 gnathobasic teeth, so it is considered the most basal genus of Pterygotioidea. The triangular anterior carapace margin present in Hughmilleria is shared by

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1472-412: The gnathobase, a lower appendage used in the alimentation) teeth on appendage VI, unlike Herefordopterus and the pterygotids, who had 12-13. Therefore, Hughmilleria represents the most basal form of Pterygotioidea. According to Clifton J. Sarle, Hughmilleria was very similar to Eurypterus , and could be confused with a species of this genus if it was not for the presence of the marginal position of

1518-560: The group, such as the slightly enlarged chelicerae (frontal appendages) and the streamlined shape of their bodies. The family contains only two genera, Hughmilleria and Herefordopterus , though other genera have been referred to the family in the past, such as genera now considered part of families such as the Mycteroptidae and the Waeringopteridae . The hughmilleriids were the most basal group of pterygotioid eurypterids, lacking

1564-412: The hughmilleriids have been found in Silurian deposits ranging from the Llandovery to Ludlow epochs in the United States , China and England . While Hughmilleria lived in brackish and fresh water communities, Herefordopterus was present in a benthic (at the lowest level of water) environment near an intertidal sandy shore and intertidal sandy mudflat environments. The Silurian deposits of

1610-465: The hughmilleriids possessed several characteristics shared with other eurypterid groups, such as the lanceolate telson (the most posterior segment of the body). Hughmilleriids are defined as pterygotioid eurypterids with swimming legs similar to those of the type genus, Hughmilleria (that is, 7th and 8th leg segments narrow and 9th segment very small), and whose second to fifth pair of appendages were spiniferous. Some further diagnostic characters unite

1656-518: The marginal ornamentation of the telson. On the other hand, Hughmilleria had certain resemblance to the basal adelophthalmid Eysyslopterus , sharing a triangular anterior carapace margin, possibly a plesiomorphic (of a common ancestor) trait. Hughmilleriid eurypterids ranged in size from 6 to 20 centimetres (2 to 8 inches), representing a group of relatively small eurypterids. Hughmilleriids would be dwarfed by some of their more derived (more "advanced") relatives within their superfamily, especially

1702-427: The presence of paired spines on the walking appendages, that along with the characteristics that Slimonia and Ciurcopterus share, suggest that the hughmilleriids were more distant from the pterygotids than Slimonia was. Within Hughmilleriidae, both genera possessed a marginal rim much broader anteriorly than posteriorly and appendages spiniferous of Hughmilleria -type, but Hughmilleria had 18-20 gnathobasic (of

1748-522: The prosoma, and were characterized in hughmilleriids as being spiniferous (possessing spines), a feature that distinguishes the group from the pterygotids and the slimonids , both groups possessing non-spiniferous appendages. The telson (the posteriormost segment of the body), which was lanceolate and styliform, is a feature shared with other eurypterid groups, such as the closely related Adelophthalmoidea . Although these telsons were not flattened and expanded as in both derived families, Herefordopterus had

1794-509: The pterygotioid eurypterids. Hughmilleria wangi Hughmilleria socialis Hughmilleria shawangunk Herefordopterus banksii Slimonia acuminata Ciurcopterus ventricosus Pterygotus anglicus Jaekelopterus rhenaniae Acutiramus macrophthalmus Acutiramus bohemicus Erettopterus bilobus Erettopterus serricaudatus Erettopterus osiliensis Erettopterus waylandsmithi Fossils of Hughmilleria have been found in Silurian deposits from

1840-548: The sister-taxon of the Pterygotidae. Sarle interpreted Hughmilleria in 1903 as an intermediate form between Eurypterus and Pterygotus , being closer to the latter. For this to happen, the loss of spines in Slimonia and the pterygotids would be convergent. The discovery of Ciurcopterus , the most primitive known pterygotid, and studies revealing that Ciurcopterus combines features of Slimonia (the appendages are particularly similar) and of more derived pterygotids, revealed that

1886-497: The various characteristics it shares with Eurypterus . The genus Hughmilleria was erected by the American geologist Clifton J. Sarle in 1903 to contain the species H. socialis , which was recovered for the first time in the Pittsford Shale Member of the Vernon Formation , New York . This species is the most abundant species of pterygotioid in the area with around 450 specimens found. The generic name derives from Hugh Miller ,

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1932-469: Was erected in 1912 by John Mason Clarke and Rudolf Ruedemann to constitute a group for the genera Pterygotus , Slimonia , Hastimima and Hughmilleria . However, Erik N. Kjellesvig-Waering emended the family in 1951, when the genera Hastimima , Hughmilleria , Grossopterus and Slimonia were referred to their own family, the Hughmilleriidae , which left Pterygotus as the only genus within

1978-461: Was first considered as a genus in the Pterygotidae, being one of the initial members of that family alongside Pterygotus , Slimonia and Hastimima upon its creation by John Mason Clarke and Rudolf Ruedemann in 1912. The family Hughmilleriidae was created by Erik N. Kjellesvig-Waering in 1951, who considered the genera Hastimima , Slimonia and Hughmilleria and the new genus Grossopterus sufficiently distinct from Pterygotus to be in

2024-465: Was originally described as a new species of the new genus Himantopterus (a preoccupied name, now Erettopterus ) by the English geologist and paleontologist John William Salter . The body of this species was elongate and attenuated behind. Its telson was lanceolated and its swimming legs were narrow. This species has also been related to Nanahughmilleria , but recent studies suggest that H. lanceolata

2070-538: Was probably closer to Eurypteroidea . However, the lack of eyes on all specimens of H. lanceolata hinders the resolution of its phylogenetic position. Hughmilleria is classified within the family Hughmilleriidae in the superfamily Pterygotioidea . Historically Hughmilleria was first considered a member of the Pterygotidae until it was assigned to its own family alongside other genera that would later be reclassified. Hughmilleria and Herefordopterus shared

2116-407: Was smaller than H. socialis . The temporal range of H. shawangunk has been placed between the Llandovery and Ludlow epoch . The largest specimens measured 12 cm (5 in) in length, and differ from the type species by the carapace, which was broader, and the compound eyes which were larger and more prominent than the eyes of H. socialis , among other aspects. The family Pterygotidae

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