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Tomlinsonus
''Tomlinsonus'' is an extinct genus of marellomorph arthropod known from the Late Ordovician ( Katian) Kirkfield Formation of Ontario, Canada. It is a member of Marellida, and closely related to '' Mimetaster''. Description Only a single partial specimen (ROMIP 66233) was recovered during fieldwork in September 2020, by independent researcher Marc Haensel. This specimen preserves a mostly complete head and some appendages. Like other marellids, the head is composed of a cephalic shield with pairs of spine-like projections, with two large pairs present in ''Tomlinsonus''. These projections curve posteriorly. Like most other marellids, these projections are covered in second-order spines. There is also a pair of smaller projections without spines extending posteriorly from the back of the head. Attached to the head is a pair of extremely elongate appendages, around in length, with 9 podomeres, with a spine present on the end of the 8th podomere, which is the longest leg segm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marrellomorpha
Marrellomorpha are an extinct group of arthropods known from the Cambrian to the Early Devonian. They lacked mineralised hard parts, so are only known from areas of exceptional preservation, limiting their fossil distribution. The best known member is ''Marrella'', with thousands of specimens found in the Cambrian aged Burgess Shale of Canada. The group is divided up into two major orders, Marrellida and Acercostraca. Marrellida is recognised by the possession of head shields with two or three pairs of elongate spine-like projections, and three pairs of uniramous appendages on the cephalon, while Acercostraca generally have large ovoid carapaces that cover the entire upper half of the body, and five pairs of uniramous cephalic appendages. Both groups have unbranched antennules and a segmented trunk with biramous appendages. Recent research has suggested the previously enigmatic Cambrian trliobite-like arthropods ''Skania'' and ''Primicaris'' may belong to this group. Their phylo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mimetaster
''Mimetaster'' is an extinct genus of Marrellomorpha, marrellomorph arthropod. The type species, ''Mimetaster hexagonalis'' is known from the Lower Devonian (Pragian-Emsian) Hunsrück Slate, and amongst the most common arthropods from the locality, with over 120 specimens including three juveniles. Description The head shield of ''M. hexagonalis'' is oval shaped and raised on its upper surface, with three pairs of elongate straight projections radiating outwards, which have pairs of spines. On the upper surface was attached pair of probable eyes on segmented stalks. Attached on the underside was a pair of forward-projecting elongate segmented antennae, the first 10 segments of which were elongate, while the subsequent 14 were short and Flagellum, flagella-like, as well as two pairs of large uniramous leg-like appendages. The first of the two pairs was substantially larger than the second. Also present on the underside of the head was a Hypostome (trilobite), hypostome, as well as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
