Hughmilleria

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Hughmilleria
Temporal range: Llandovery-Ludlow, 442–418.7  Ma
Hughmilleria fossils.png
Fossils of H. socialis.
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Order: Eurypterida
Superfamily: Pterygotioidea
Family: Hughmilleriidae
Genus: Hughmilleria
Sarle, 1903
Type species
Hughmilleria socialis
Sarle, 1903
Species
  • H. shawangunk Clarke, 1907
  • H. socialisSarle, 1903
  • H. wangiTetlie, Selden & Ren, 2007

Hughmilleria is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of Hughmilleria have been discovered in deposits of 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.

Contents

H. socialis is the type species of Hughmilleriidae, 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.

Description

Restoration of H. socialis The Eurypterida of New York plate 59.jpg
Restoration of H. socialis

Hughmilleria is the most basal (primitive) known member of the Pterygotioidea. [1] 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). [2] The telson (the most posterior segment of the body), which was lanceolate and styliform, 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. [3] 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. [1] The genus 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. [4]

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 the various characteristics it shares with Eurypterus. [5] [3]

History of research

Fossils of H. shawangunk Hughmilleria shawangunk The Eurypterida of New York.png
Fossils of H. shawangunk

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. [3] This species is the most abundant species of pterygotioid in the area with around 450 specimens found. [6] The generic name derives from Hugh Miller, a Scottish geologist and writer who found fossils of eurypterids of the Silurian, among them Hughmilleria. [7] A variety of H. socialis was also described, Hughmilleria socialis var. robusta, but currently it is considered a synonym of the species mentioned. [8]

Four years later, a second species was discovered among the fauna of the Shawangunk grit at Otisville. It was described as Hughmilleria shawangunk and was smaller than H. socialis. [3] The temporal range of H. shawangunk has been placed between the Llandovery and Ludlow epoch. [1] The largest specimens measured 12 cm (5 in) in length, [2] 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. [3]

The family Pterygotidae 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 the Pterygotidae. In 1961, Erik N. Kjellesvig-Waering split Hughmilleria into two subgenera, Hughmilleria (Hughmilleria) and Hughmilleria (Nanahughmilleria), [9] 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 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 a slightly wider carapace than in the other species. [1] Measuring 6 cm (2 in) in length, H. wangi is the smallest known species of Hughmilleria and of the Pterygotioidea superfamily. [2]

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. [8] It 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. [10] This species has also been related to Nanahughmilleria, but recent studies suggest that H. lanceolata was probably closer to Eurypteroidea. However, the lack of eyes on all specimens of H. lanceolata hinders the resolution of its phylogenetic position. [11]

Classification

Size comparison of the three species of Hughmilleria Hughmilleria Size.svg
Size comparison of the three species of Hughmilleria

Hughmilleria is classified within the family Hughmilleriidae in the superfamily Pterygotioidea. [8] 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. [12]

Hughmilleria and Herefordopterus shared 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 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. [13] 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 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. [14]

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 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. [3]

The cladogram presented below, derived from a 2007 study by researcher O. Erik Tetlie, showcases the interrelationships between the pterygotioid eurypterids. [15]

Pterygotioidea

Paleoecology

Painting painted in 1912 by Charles R. Knight depicting various eurypterids discovered in New York. The painting includes Dolichopterus, Eusarcana, Stylonurus, Eurypterus and Pterygotus. Hughmilleria can be seen in the bottom of the right corner. The Eurypterida of New York figure np 1.jpg
Painting painted in 1912 by Charles R. Knight depicting various eurypterids discovered in New York. The painting includes Dolichopterus , Eusarcana , Stylonurus , Eurypterus and Pterygotus . Hughmilleria can be seen in the bottom of the right corner.

Fossils of Hughmilleria have been found in Silurian deposits from the Llandovery and Ludlow epochs. [15] Together with its close relatives, Hughmilleria dominated the communities in brackish and fresh water, while Pterygotus and Eurypterus dominated marine environments. [16]

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 the crustacean Ceratiocaris and the ostracod Leperditia . [17] 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. [17]

See also

Related Research Articles

<span class="mw-page-title-main">Eurypterid</span> Order of arthropods (fossil)

Eurypterids, often informally called sea scorpions, are a group of extinct 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 group is likely to have appeared first either during the Early Ordovician or Late Cambrian period. With approximately 250 species, the Eurypterida is the most diverse Paleozoic chelicerate order. Following their appearance during the Ordovician, eurypterids became major components of marine faunas during the Silurian, from which the majority of eurypterid species have been described. The Silurian genus Eurypterus accounts for more than 90% of all known eurypterid specimens. Though the group continued to diversify during the subsequent Devonian period, the eurypterids were heavily affected by the Late Devonian extinction event. They declined in numbers and diversity until becoming extinct during the Permian–Triassic extinction event 251.9 million years ago.

<i>Pterygotus</i> Extinct genus of eurypterid

Pterygotus is a 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 several different species. Fossils have been recovered from four continents; Australia, Europe, North America and South America, which indicates that Pterygotus might have had a nearly cosmopolitan (worldwide) distribution. The type species, P. anglicus, was described by Swiss naturalist Louis Agassiz in 1839, who gave it the name Pterygotus, meaning "winged one". Agassiz mistakenly believed the remains were of a giant fish; he would only realize the mistake five years later in 1844.

<i>Slimonia</i> Extinct genus of arthropods

Slimonia is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of Slimonia have been discovered in deposits of Silurian age in South America and Europe. Classified as part of the family Slimonidae alongside the related Salteropterus, the genus contains three valid species, S. acuminata from Lesmahagow, Scotland, S. boliviana from Cochabamba, Bolivia and S. dubia from the Pentland Hills of Scotland and one dubious species, S. stylops, from Herefordshire, England. The generic name is derived from and honors Robert Slimon, a fossil collector and surgeon from Lesmahagow.

<i>Acutiramus</i> Extinct genus of arthropods

Acutiramus is a genus of giant predatory eurypterid, an extinct group of aquatic arthropods. Fossils of Acutiramus have been discovered in deposits of Late Silurian to Early Devonian age. Eight species have been described, five from North America and two from the Czech Republic. The generic name derives from Latin acuto and Latin ramus ("branch"), referring to the acute angle of the final tooth of the claws relative to the rest of the claw.

<i>Nanahughmilleria</i> Extinct genus of arthropods

Nanahughmilleria is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of Nanahughmilleria have been discovered in deposits of Devonian and Silurian age in the United States, Norway, Russia, England and Scotland, and have been referred to several different species.

<i>Pittsfordipterus</i> Genus of arthropods (fossil)

Pittsfordipterus is a genus of eurypterid, an extinct group of aquatic arthropods. Pittsfordipterus is classified as part of the family Adelophthalmidae, the only clade in the derived ("advanced") Adelophthalmoidea superfamily of eurypterids. Fossils of the single and type species, P. phelpsae, have been discovered in deposits of Silurian age in Pittsford, New York state. The genus is named after Pittsford, where the two only known specimens have been found.

Salteropterus is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of Salteropterus have been discovered in deposits of Late Silurian age in Britain. Classified as part of the family Slimonidae, the genus contains one known valid species, S. abbreviatus, which is known from fossils discovered in Herefordshire, England, and a dubious species, S. longilabium, with fossils discovered in Leintwardine, also in Herefordshire. The generic name honours John William Salter, who originally described S. abbreviatus as a species of Eurypterus in 1859.

<i>Erettopterus</i> Extinct genus of arthropods

Erettopterus is a genus of large predatory eurypterid, an extinct group of aquatic arthropods. Fossils of Erettopterus have been discovered in deposits ranging from Early Silurian to the Early Devonian, and have been referred to several different species. Fossils have been recovered from two continents; Europe and North America. The genus name is composed by the Ancient Greek words ἐρέττω (eréttō), which means "rower", and πτερόν (pterón), which means "wing", and therefore, "rower wing".

<i>Parahughmilleria</i> Extinct genus of arthropods

Parahughmilleria is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of Parahughmilleria have been discovered in deposits of the Devonian and Silurian age in the United States, Canada, Russia, Germany, Luxembourg and Great Britain, and have been referred to several different species. The first fossils of Parahughmilleria, discovered in the Shawangunk Mountains in 1907, were initially assigned to Eurypterus. It would not be until 54 years later when Parahughmilleria would be described.

<span class="mw-page-title-main">Pterygotidae</span> Extinct family of eurypterids

Pterygotidae is a family of eurypterids, an extinct group of aquatic arthropods. They were members of the superfamily Pterygotioidea. Pterygotids were the largest known arthropods to have ever lived with some members of the family, such as Jaekelopterus and Acutiramus, exceeding 2 metres (6.6 ft) in length. Their fossilized remains have been recovered in deposits ranging in age from 428 to 372 million years old.

<span class="mw-page-title-main">Carcinosomatidae</span> Extinct family of arthropods

Carcinosomatidae is a family of eurypterids, an extinct group of aquatic arthropods. They were members of the superfamily Carcinosomatoidea, also named after Carcinosoma. Fossils of carcinosomatids have been found in North America, Europe and Asia, the family possibly having achieved a worldwide distribution, and range in age from the Late Ordovician to the Early Devonian. They were among the most marine eurypterids, known almost entirely from marine environments.

<span class="mw-page-title-main">Pterygotioidea</span> Extinct superfamily of eurypterids

Pterygotioidea is a superfamily of eurypterids, an extinct group of aquatic arthropods. Pterygotioids were the most derived members of the infraorder Diploperculata and the sister group of the adelophthalmoid eurypterids. The group includes the basal and small hughmilleriids, the larger and specialized slimonids and the famous pterygotids which were equipped with robust and powerful cheliceral claws.

<span class="mw-page-title-main">Adelophthalmidae</span> Family of eurypterids

Adelophthalmidae is a family of eurypterids, an extinct group of aquatic arthropods. Adelophthalmidae is the only family classified as part of the superfamily Adelophthalmoidea, which in turn is classified within the infraorder Diploperculata in the suborder Eurypterina.

<span class="mw-page-title-main">Eurypterina</span> Suborder of eurypterid

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 deposits worldwide, though primarily in North America and Europe.

<span class="mw-page-title-main">Hughmilleriidae</span> Extinct family of eurypterids

Hughmilleriidae 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 families Pterygotidae and Slimonidae. Despite their classification as pterygotioids, the hughmilleriids possessed several characteristics shared with other eurypterid groups, such as the lanceolate telson.

<span class="mw-page-title-main">Slimonidae</span> Extinct family of eurypterids

Slimonidae is a family of eurypterids, an extinct group of aquatic arthropods. Slimonids were members of the superfamily Pterygotioidea and the family most closely related to the derived pterygotid eurypterids, which are famous for their cheliceral claws and great size. Many characteristics of the Slimonidae, such as their flattened and expanded telsons, support a close relationship between the two groups.

<i>Herefordopterus</i> Extinct genus of arthropods

Herefordopterus is a genus of eurypterid, an extinct group of aquatic arthropods. Herefordopterus is classified as part of the family Hughmilleriidae, a basal family in the highly derived Pterygotioidea superfamily of eurypterids. Fossils of the single and type species, H. banksii, have been discovered in deposits of Silurian age in Herefordshire and Shropshire, England. The genus is named after Herefordshire, where most of the Herefordopterus fossils have been found. The specific epithet honors Richard Banks, who found several well-preserved specimens, including the first Herefordopterus fossils.

<i>Eysyslopterus</i> Extinct genus of arthropods

Eysyslopterus is a genus of eurypterid, an extinct group of aquatic arthropods. Eysyslopterus is classified as part of the family Adelophthalmidae, the only clade within the derived ("advanced") Adelophthalmoidea superfamily of eurypterids. One fossil of the single and type species, E. patteni, has been discovered in deposits of the Late Silurian period in Saaremaa, Estonia. The genus is named after Eysysla, the Viking name for Saaremaa, and opterus, a traditional suffix for the eurypterid genera, meaning "wing". The species name honors William Patten, an American biologist and zoologist who discovered the only known fossil of Eysyslopterus.

<i>Ciurcopterus</i> Extinct genus of arthropods

Ciurcopterus is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of Ciurcopterus have been discovered in deposits of Late Silurian age in North America. Classified as part of the family Pterygotidae, the genus contains two species, C. sarlei from Pittsford, New York and C. ventricosus from Kokomo, Indiana. The genus is named in honor of Samuel J. Ciurca, Jr., who has contributed significantly to eurypterid research by discovering a large amount of eurypterid specimens, including the four specimens used to describe Ciurcopterus itself.

<span class="mw-page-title-main">Timeline of eurypterid research</span>

This timeline of eurypterid research is a chronologically ordered list of important fossil discoveries, controversies of interpretation, and taxonomic revisions of eurypterids, a group of extinct aquatic arthropods closely related to modern arachnids and horseshoe crabs that lived during the Paleozoic Era.

References

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