''Enalikter'' ("scourger of the sea") is an extinct arthropod described from the middle

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...

Herefordshire Lagerstätte at the England–Wales border in UK. This genus is known from only one species, ''E. aphson''. ''Enalikter'' is described as late-living example of Megacheira, "great-appendage arthropod". It was once considered as an

annelid The annelids (Annelida , from Latin ', "little ring"), also known as the segmented worms, are a large phylum, with over 22,000 extant species including ragworms, earthworms, and leeches. The species exist in and have adapted to various ecol ...

by other researchers, however subsequent studies denied this. Its interpretation as megacheiran arthropod is questioned in later study.

Morphology

Enalikter_aphson_reconstruction_as_arthropod

''Enalikter'' is small arthropod with length just around long. Head shield is subrectangular and lacked eyes. Median, unpaired

antenna Antenna ( antennas or antennae) may refer to: Science and engineering * Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g., TV or radio) waves * Antennae Galaxies, the name of two collid ...

and three pairs of appendages can be seen on head, and a first appendage had three tapering

flagella A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have f ...

. Twelve trunk segments lack tergites, and is flexible to bend at least 90 degrees. Trunk appendages are biramous. Egg-like shaped telson had two pairs of blade-like processes.

Classification

''Enalikter'' is probably related to ''

Bundenbachiellus ''Bundenbachiellus'' is an extinct genus of arthropod described from the Lower Devonian Hunsrück Slate of Germany. This genus is known from only one species, ''B. giganteus''. Alongside its possible relative ''Enalikter'' from Silurian, it is ...

'', larger arthropod genus from Hunsrück Slate, because of morphological similarities, even though there are some differences of characters. Original description considered that these taxa fall in a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

of short-great-appendage arthropods, Megacheira. These taxa are included in the family Enaliktidae, and probably they are members of the stem clade Leanchoiliida. However, in 2015, other researchers questioned its affinity as arthropod, and considering from characters like lack of tergites, flexible trunk segments, and unpaired antenna, it is considered that is more likely to be an

. This theories, however, denied by two studies, because characters they pointed are also known from various arthropod taxa, in addition there are features that shows arthropod affinity, like ventrally placed mouth and J-shaped gut. Moreover, the characters that used to diagnose as annelids by these researchers are taken from different annelids, and there is no annelid that shares these characteristics. Although it is likely to be an arthropod, its affinity as megacheiran is still questioned. However, ''Enalikter'' and ''Bundenbachiellus'' should be considered of potential importance to clarify the position of '' Oelandocaris'', taxon with questioned characteristics both for stem-crustaceans and megacheiran.

References

{{taxonbar, from=Q112811603 Silurian arthropods of Europe Silurian England Fossils of England Fossil taxa described in 2014 Megacheira