''Mictomerus'' is an extinct genus of

Cambrian The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...

euthycarcinoid Euthycarcinoidea are an enigmatic group of extinct, possibly amphibious arthropods that ranged from Cambrian to Triassic times. Fossils are known from Europe, North America, Argentina, Australia, and Antarctica. Description The euthycarcinoid bod ...

s from the Potsdam Group of

Quebec Quebec is Canada's List of Canadian provinces and territories by area, largest province by area. Located in Central Canada, the province shares borders with the provinces of Ontario to the west, Newfoundland and Labrador to the northeast, ...

, Canada. The genus contains a single species, ''Mictomerus melochevillensis'', known from 29 specimens, all but one preserved ventrally.

Description

''Mictomerus'' cephalic area is poorly known, with an elongate oval structure at the anterior portion with a narrow medial invagination, and two circular structures which may be eyes. The thorax has five to six overlapping

tergites A ''tergum'' (Latin for "the back"; : ''terga'', associated adjective tergal) is the dorsal ('upper') portion of an arthropod segment other than the head. The anterior edge is called the 'base' and posterior edge is called the 'apex' or 'margin'. ...

, with varying posterolateral margins. Due to the ventral preservation of the specimens, their dorsal surfaces are unknown. The thorax's segmentation is also unknown, however it can be inferred from the limbs. The abdomen is composed of five limbless segments, decreasing slightly in width. The abdomen lacks ornamentation, and the telson is not known. The limbs are uniramous and composed of three to five segments, with the first being the widest. These limbs decrease in size towards the posterior of the animal. ''Mictomerus'' likely lived in intertidal regions, with brief forays onto land evidenced by trackways, feeding on microbial mats and detritus via gnathobases (inferred from the very closely spaced limbs and ventromedial groove). The limbs of ''Mictomerus'' are much more robust than other euthycarcinoids, suggesting it walked along the bottom when moving through water. It also may have burrowed into mud as an anti-desiccation measure, as evidenced by casts preserved at the end of '' Cruziana''-like fossils.

Etymology

''Mictomerus'' derives from the Greek words ''miktous'' meaning "mixed" and ''meros'' meaning "parts". The specific name ''melochevillensis'' is named after Melocheville, Quebec, where the holotype was found.

References

{{Taxonbar, from=Q107325368 Paleozoic life of Quebec Fossil taxa described in 2010 Cambrian arthropods of North America Cambrian genus extinctions