Molaria Temporal range: | |
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Molaria spinifera in dorsal and lateral views from a plate in Walcott, 1912 | |
Molaria spinifera life restoration | |
Scientific classification | |
Kingdom: | Animalia |
Phylum: | Arthropoda |
(unranked): | † Artiopoda |
Genus: | † Molaria Walcott, 1912 [1] |
Type species | |
Molaria spinifera Walcott, 1912 | |
Other species | |
Molaria steiniPeel, 2017 |
Molaria is a genus of Cambrian arthropod, the type species M. spinifera is known from the Middle Cambrian Burgess Shale. 144 specimens of Molaria are known from the Greater Phyllopod bed, where they comprise 0.27% of the community. [2] A second species M. steini was described from the Sirius Passet in Greenland in 2017. [3]
The body of Molaria consisted of a head shield (cephalon), a trunk consisting of eight sections (tergites), and a telson, which included a short ventral spine and a long posterior spine. Three pairs of legs were beneath the cephalon and another eight pairs were attached to the trunk. Eyes were lacking, but a pair of short antennae was present on the cephalon. Specimens of Molaria ranged from 8 to 26 mm in length from cephalon to telson, with the posterior spine slightly longer than the body length. [4] Molaria was superficially similar to Habelia , another Burgess Shale arthropod with a long tail spine, but which possessed 12 trunk tergites. [4] It is currently considered a member of Artiopoda. [3]
The genus name derives from "Molar", the name of a mountain peak east of the Valley of the Ten Peaks in Alberta, Canada. [1]
Opabinia regalis is an extinct, stem group arthropod found in the Middle Cambrian Burgess Shale Lagerstätte of British Columbia. Opabinia was a soft-bodied animal, measuring up to 7 cm in body length, and its segmented trunk had flaps along the sides and a fan-shaped tail. The head shows unusual features: five eyes, a mouth under the head and facing backwards, and a clawed proboscis that probably passed food to the mouth. Opabinia probably lived on the seafloor, using the proboscis to seek out small, soft food. Fewer than twenty good specimens have been described; 3 specimens of Opabinia are known from the Greater Phyllopod bed, where they constitute less than 0.1% of the community.
Marrella is an extinct genus of marrellomorph arthropod known from the middle Cambrian Burgess Shale of British Columbia. It is the most common animal represented in the Burgess Shale, with tens of thousands of specimens collected. Much rarer remains are also known from deposits in China.
Sidneyia is an extinct arthropod known from fossils found from the Early Cambrian-age Maotianshan Shales to the Mid Cambrian Burgess Shale formation of British Columbia. 144 specimens of Sidneyia are known from the Greater Phyllopod bed, where they comprise 0.27% of the community.
Ottoia is a stem-group archaeopriapulid worm known from Cambrian fossils. Although priapulid-like worms from various Cambrian deposits are often referred to Ottoia on spurious grounds, the only clear Ottoia macrofossils come from the Burgess Shale of British Columbia, which was deposited 508 million years ago. Microfossils extend the record of Ottoia throughout the Western Canada Sedimentary Basin, from the mid- to late- Cambrian. A few fossil finds are also known from China.
Yohoia is an extinct genus of megacheiran arthropod from the Cambrian period that has been found as fossils in the Burgess Shale formation of British Columbia, Canada. It has been placed among the arachnomorpha, a group of arthropods that includes the chelicerates and possibly the trilobites. Fossils range in size from 7 to 23 mm. 711 specimens of Yohoia are known from the Greater Phyllopod bed, where they comprise 1.35% of the community.
Canadaspis is an extinct genus of bivalved Cambrian arthropod, known from North America and China. They are thought to have been benthic feeders that moved mainly by walking and possibly used its biramous appendages to stir mud in search of food. They have been placed within the Hymenocarina, which includes other bivalved Cambrian arthropods.
Cheloniellida is a taxon of extinct Paleozoic arthropods. As of 2018, 7 monotypic genera of cheloniellids had been formally described, whose fossils are found in marine strata ranging from Ordovician to Devonian in age. Cheloniellida has a controversial phylogenetic position, with previous studies associated it as either a member or relative of various fossil and extant arthropod taxa. It was later accepted as a member of Vicissicaudata within Artiopoda.
Waptia fieldensis is an extinct species of arthropod from the Middle Cambrian Burgess Shale Lagerstätte of Canada. It grew to a length of about 8 cm (3 in) and resembled modern shrimp in both morphology and habit. It had a large bivalved carapace and a segmented body terminating into a pair of tail flaps. It was an active swimmer and likely a predator of soft-bodied prey. It is also one of the oldest animals with direct evidence of brood care.
Buenellus higginsi is an average size trilobite, which lived during the Lower Cambrian period, in what is now North-West Greenland. It is a prominent member of the Sirius Passet fauna. Buenellus higginsi is the only known species in the genus Buenellus.
A number of assemblages bear fossil assemblages similar in character to that of the Burgess Shale. While many are also preserved in a similar fashion to the Burgess Shale, the term "Burgess Shale-type fauna" covers assemblages based on taxonomic criteria only.
Actaeus is a Cambrian organism with a resemblance to the great appendage arthropods, containing the single species Actaeus armatus. It is known from a single specimen recovered from the Burgess Shale of British Columbia, Canada. The specimen is over 6 cm long and has a body consisting of a head shield, 11 body tergites, and a terminal plate.
Sarotrocercus is a small Cambrian arthropod known from Burgess shale, reaching a centimetre or two in length (0.39–0.79 in). Sarotrocercus is only known from 7 specimens. It may lie in the arthropod crown group, and a recent study has revised some points of its original description.
Alalcomenaeus is one of the most widespread and longest-surviving arthropod genera of the Early and Middle Cambrian. Known from over 300 specimens in the Burgess Shale, and the Chengjiang, it bears great similarity to the opabiniids.
Plenocaris plena is a Cambrian arthropod with a bivalved carapace, and is known from the Burgess shale and Chengjiang. Originally described as a species of Yohoia by Walcott in 1912, it was placed into its own genus in 1974.
Schinderhannes bartelsi is a species of hurdiid radiodont (anomalocaridid) known from one specimen from the lower Devonian Hunsrück Slates. Its discovery was astonishing because previously, radiodonts were known only from exceptionally well-preserved fossil beds (Lagerstätten) from the Cambrian, 100 million years earlier.
Isoxys is a genus of extinct, pelagic bivalved Cambrian arthropod; the various species of which are thought to have been freely swimming predators. It had a pair of large spherical eyes, and two large frontal appendages It is possible that these appendages are homologous to the great appendages of radiodonts and megacheirans.
Emeraldella is a genus of arthropod known from the Middle Cambrian of North America. The type species E. brocki was described in 1912 from the Burgess Shale. 21 specimens of Emeraldella are known from the Greater Phyllopod bed, where they comprise < 0.1% of the community. A re-study on the species was done in 2012. A second species E. brutoni is known from the Wheeler Shale, which was described in 2011. An additional specimen of E. brutoni was described in 2019, which revealed more of the anatomy. It has been placed as part of the Artiopoda, a group of arthropods containing trilobites and their relatives.
Kiisortoqia soperi is an extinct species of arthropod from the Early Cambrian Sirius Passet Lagerstätte in Greenland. While it had a superficially trilobite-like bodyform, it also possessed large frontal appendages similar to those of radiodonts.
Buenaspis is a genus of small nektaspid arthropod, that lived during the early Cambrian period. Fossil remains of Buenaspis were collected from the Lower Cambrian Sirius Passet Lagerstätte of North Greenland. Buenaspis looks like a soft eyeless trilobite. It has a headshield slightly larger than the tailshield (pygidium), and in between them six thoracic body segments (somites). The genus is monotypic, its sole species being Buenaspis forteyi.
Arthroaspis is an extinct genus of arthropod known from the Cambrian aged Sirius Passet Lagerstatte in Greenland. It is relatively large in size for Cambrian arthropods, attaining a length of up to 215 mm. It is a common component of the Passet fauna, being located at multiple localities within the formation. It possessed 14 tergites. In the describing paper, it was recovered as a member of a non-monophyletic Artiopoda. It has subsequently been considered a potential close relative of nektaspids.