Hughmilleria
Encyclopedia
Hughmilleria is a genus of Silurian
eurypterid
. The genus name commemorates the Scottish geologist
Hugh Miller
.
deposits from 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.
to Permian
periods, were small to large forms with outer surfaces that were either smooth or that had transverse integuemental folds or semilunar to pointed scales. The telson
(tail) was lanceolate or somewhat expanded. Hughmilleriidae also had chelicerae
(claws in front of the mouth) that were small to medium-sized, without teeth. Their walking legs were stout, with spines, and their swimming paddles were narrow. The genital appendages of males were narrow, without lateral points.
Hughmilleria is distinguishable from other Hughmilleriidae by the postlateral prolongation of the first postabdominal segment. The telson is lanceolate in form. The chelicerae are medium-sized. The prosoma (head) is ovate, with compound eyes located near the edge of the front corners.
Silurian
The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...
eurypterid
Eurypterid
Eurypterids are an extinct group of arthropods related to arachnids which include the largest known arthropods that ever lived. They are members of the extinct order Eurypterida ; which is the most diverse Paleozoic chelicerate order in terms of species...
. The genus name commemorates the Scottish geologist
Geologist
A geologist is a scientist who studies the solid and liquid matter that constitutes the Earth as well as the processes and history that has shaped it. Geologists usually engage in studying geology. Geologists, studying more of an applied science than a theoretical one, must approach Geology using...
Hugh Miller
Hugh Miller
Hugh Miller was a self-taught Scottish geologist and writer, folklorist and an evangelical Christian.- Life and work :Born in Cromarty, he was educated in a parish school where he reportedly showed a love of reading. At 17 he was apprenticed to a stonemason, and his work in quarries, together with...
.
Stratigraphy and ecology
Fossils of Hughmilleria have been found in SilurianSilurian
The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...
deposits from the Llandovery and Ludlow epochs
Epoch (geology)
An epoch is a subdivision of the geologic timescale based on rock layering. In order, the higher subdivisions are periods, eras and eons. We are currently living in the Holocene epoch...
. Together with its close relatives, Hughmilleria dominated the communities in brackish and fresh water
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
, while Pterygotus
Pterygotus
Pterygotus is the second-largest known eurypterid, or sea scorpion and one of the largest arthropods of all time.-Description:...
and Eurypterus
Eurypterus
Eurypterus is an extinct genus of sea scorpions. They existed during the Silurian Period, from around 432 to 418 million years ago.There are fifteen species belonging to the genus Eurypterus, the most common of which is Eurypterus remipes, the first eurypterid fossil discovered and the state...
dominated marine environments.
Description
The family Hughmilleriidae, which lived from the OrdovicianOrdovician
The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...
to Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
periods, were small to large forms with outer surfaces that were either smooth or that had transverse integuemental folds or semilunar to pointed scales. The telson
Telson
The telson is the last division of the body of a crustacean. It is not considered a true segment because it does not arise in the embryo from teloblast areas as do real segments. It never carries any appendages, but a forked "tail" called the caudal furca is often present. Together with the...
(tail) was lanceolate or somewhat expanded. Hughmilleriidae also had chelicerae
Chelicerae
The chelicerae are mouthparts of the Chelicerata, an arthropod subphylum that includes arachnids, Merostomata , and Pycnogonida . Chelicerae are pointed appendages which are used to grasp food, and are found in place of the chewing mandibles most other arthropods have...
(claws in front of the mouth) that were small to medium-sized, without teeth. Their walking legs were stout, with spines, and their swimming paddles were narrow. The genital appendages of males were narrow, without lateral points.
Hughmilleria is distinguishable from other Hughmilleriidae by the postlateral prolongation of the first postabdominal segment. The telson is lanceolate in form. The chelicerae are medium-sized. The prosoma (head) is ovate, with compound eyes located near the edge of the front corners.
Species
- Hughmilleria shawangunk Clarke, 1907
- Hughmilleria socialis Sarle, 1903
- Hughmilleria wangi Tetlie, Selden & Ren, 2007