''Cascolus'' is an extinct genus of stem-mandibulate known from the

Coalbrookdale Formation Coalbrookdale Formation, earlier known as Wenlock Shale or Wenlock Shale Formation and also referred to as Herefordshire Lagerstätte in palaeontology, is a fossil-rich deposit ('' Konservat-Lagerstätte'') in Powys and Herefordshire at the Engl ...

Description

''Cascolus'' is a long, somewhat vermiform arthropod, roughly 9 millimetres long. It has a head segment containing a head shield, stalked eyes and five pairs of limbs, the first similar to megacheirans and the other four

biramous The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip, ...

with gnathobases, followed by a nine-segmented thorax and two possibly limbless segments near the posterior. The trunk remains similar in size through tergites 1-4, and then decreases in width onwards into the limbless segments.

Ecology

''Cascolus'' appears to have been a nektobenthic animal, possibly a scavenger.

Etymology

''Cascolus'' was named in honour of

Sir David Attenborough Sir David Frederick Attenborough (; born 8 May 1926) is an English broadcaster, biologist, natural historian and writer. He is best known for writing and presenting, in conjunction with the BBC Studios Natural History Unit, the nine nature d ...

. The genus name derives from "castrum" ("stronghold") and "colus" ("dwelling in"), alluding to the Middle or Old English source for the name "Attenborough". The specific name ''ravitis'' derives from "Ratae" (the Roman name for

Leicester Leicester ( ) is a city status in the United Kingdom, city, Unitary authorities of England, unitary authority area, and the county town of Leicestershire in the East Midlands of England. It is the largest city in the East Midlands with a popula ...

), "vita" ("life") and "commeatis" ("messenger")

Distribution

''Cascolus'' is known from a single specimen from the

Silurian The Silurian ( ) is a geologic period and system spanning 23.5 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 third and shortest period of t ...

Coalbrookdale Formation in England, a diverse Silurian Lagerstatte.

Classification

''Cascolus'' was originally considered as a stem-group

phyllocarid Phyllocarida is a subclass of crustaceans, comprising the extant order Leptostraca and the extinct orders Hymenostraca and Archaeostraca. This clade of marine crustaceans diversified extensively during the Ordovician The Ordovician ( ) is a ...

. According to phylogenic analysis in Pulsipher ''et al.'' (2022), it is considered as stem-mandibulate instead.

References