User:Ichthyovenator/Pentecopterus

Ichthyovenator/Pentecopterus; Temporal range: Darriwilian, 467.3–458.4 Ma PreꞒ Ꞓ O S D C P T J K Pg N
	SUI 139941, the holotype specimen of P. decorahensis, consisting of parts of the underside of the head and two appendages
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Chelicerata
Order:	†Eurypterida
Superfamily:	†Carcinosomatoidea
Family:	†Megalograptidae
Genus:	†Pentecopterus; Lamsdell et al., 2015
Species:	†P. decorahensis
Binomial name
	†Pentecopterus decorahensis; Lamsdell et al., 2015

Pentecopterus is a genus of eurypterid, an extinct group of aquatic arthropods. The type and only species of Pentecopterus, P. decorahensis, is known from deposits of Middle Ordovician age in the United States.

Description [WIP]

History of research [WIP]

Eurypterids are poorly known from the Ordovician period. Before the description of Pentecopterus, only 11 species of eurypterids (the order as a whole comprising around 250 species) were recognized as valid, with a majority of the reported eurypterid fossils from the period now being considered either pseudofossils or misidentifications. Pentecopterus is the earliest known eurypterid and the discovery of its fossils extended the known temporal range of the eurypterids further back by about nine million years^[1] (the previous earliest known eurypterid having been Brachyopterus).^[2] In contrast to many other Ordovician eurypterids, the fossils of Pentecopterus are also exceptionally well-preserved, allowing for and almost complete understanding of its external morphology, as well as studies of the microstructure of its body. Additionally, the large number of fossils account not only for adult specimens, but also some juveniles, allowing for study of the ontogeny of Pentecopterus.^[3]

The fossils of Pentecopterus were discovered in Darriwilian-age (467.3–458.4 Ma;^[4] Middle Ordovician) deposits of the Winneshiek Shale near Decorah, Iowa in 2010. Most of the fossils were collected from the uppermost 4 meters (13.1 ft) of the shale. Some specimens were gathered from stone blocks that had eroded during flooding, though they were assumed to have originally also come from the uppermost parts of the shale. In total, more than 300 eurypterid fossils, most being fragmentary, were recovered from the deposits,^[4] out of which more than 150 were assigned to the new genus and species Pentecopterus decorahensis.^[1] Because of the large number of fossils, and because none of the fossils preserve any internal soft tissue, it is possuble that the specimens are exuviae, accumulated in this location during a mass-molting.^[4]

The generic name Pentecopterus derives from the penteconter (Ancient Greek: πεντηκόντερος), an ancient Greek warship, because the body shape of Pentecopterus superficially resembles the ship and because the penteconter being one of the first true warships parallels Pentecopterus being an early predatory eurypterid. The second part of the generic name, -pterus, derives from the Ancient Greek φτερός ("wing") and is the epithet that is most often used for genera of eurypterids. The species name decorahensis references Decorah.^[5] The fossil material referred to Pentecopterus, including the designated type specmen SUI 139941, which consists of portions of the underside of the head and two appendages,^[5] are housed in the Paleontology Repisotory of the Department of Earth and Environmental Sciences at the University of Iowa.^[4]

Classification [WIP]

Paleobiology [WIP]

Cuticle [WIP]

Locomotion [WIP]

Ontogeny [WIP]

Paleoecology [WIP]

The Winneshiek Shale is only found in a circular basin, about 5.6 kilometers (3.5 miles) in diameter, in the area around Decorah. Geological studies suggest that the basin originated through a meteroite impact. Geological evidence indicate that the crater, termed the Decorah Impact Structure, was once home to a tropical nearshore marine to marginal marine environment containing water with low oxygen levels, and possibly also brackish water. During the time of Pentecopterus, the site was located on the shores of the southern continent of Laurentia.^[4]

The fossil fauna of the Winneshiek Shale was first uncovered in 2005 by geologists of the Iowa Geological Survey. Comprising an unusual Middle Ordovician fauna, the fossils found include algae, plant materials, conodonts, possibly jawless fish and various invertebrates. Among the invertebrates, the most diverse and dominant group were the arthropods, but other groups have also been found, including phyllocarids and bivalves. Given that the local fauna is very different from the usual marine shelly fossil fauna of the period, the restricted environment of the basin may have been inhospitable to the typical marine animals found elsewhere.^[4]

All known Ordovician eurypterids fall into one of two distinct ecological categories: large and active predators from Laurentia, or demersal (living on the seafloor) and basal animals from the continents Avalonia and Gondwana.^[1]