The term "Mobula worm" refers to the extinct genus of Cambrian kerygmachelid lobopodians called Mobulavermis from the Pioche Shale, which is part of the Combined Metals Member of the Pioche Formation in Nevada, USA. Based on the holotype and paratype, M. adustus is the type species.
Etymology
The genus name "Mobula," which refers to the extant manta rays and devil rays, is the source of the generic name Mobulavermis (IPA: [ˊmɒbjuləˈuɛrmɪs]). This is compared to Mobula rays' large swimming flaps and elongated, flexible caudal spines, which mimic the shape of the new taxon. The Latin word "vermis," which means "worm," is added to this. The particular name adustus is derived from a Latin word that can mean "burnt," "singed," or "sun-burnt" (IPA: [ˌaduˈstʊs]). This alludes to the dry circumstances of the original site as well as the striking yellow, red, and black coloring of the two known specimens.
Description
Two specimens of Mobulavermis have been described by McCall (2023). The holotype KUMIP 298510's undamaged posterior section extends approximately 80.60 mm (3.2 in) along the body's curvature. The paratype, KUMIP 298511, is an incomplete individual that retains the posterior part of the body, but remnants of the trunk and flaps extend towards the front. It measures around ~50.7 mm (2.0 in) along the sagittal curve of the trunk. The trunk has fine transverse annulations and is unsclerotized. In the holotype, there is a circular feature next to the intestine that could be a digestive gland. More lateral flaps than any other known lobopodian or radiodont are said to be present; at least 18 throughout the trunk's length, with the number decreasing in an acuminate distribution toward the caudal spine. The flaps' front borders seem flatter, whilst the posterior margins are round and smooth. Perhaps the texture of the flaps was not as strong as that of Kerygmachela's wrinkled flaps. The caudal spine, which appears to be shorter and more flexible than those of Kerygmachela, neatly transitions from the trunk part. Based on complete specimens of Kerygmachela, adult individuals may have grown between ~30 cm (11.8 in) and ~50 cm (19.7 in), making it a big animal among Cambrian species. Its elongate compound eyes on the bottom of its head are another clue that it was a pelagic species, preying on tiny food in the water column, according to Kerygmachela.
Classification
McCall (2023) identified Mobulavermis among the "gilled lobopodians" (Utahnax and Kerygmachela) in his phylogenetic study. The research also reveals that "gilled lobopodians" belong to the monophyletic clade Kerygmachelidae, which is also defined in the same study. However, the term "gilled lobopodians" was previously used colloquially to refer to the group rather than having a valid clade name. It was previously proposed that the lobopod limbs of Kerygmachela and Utahnax may have been inadequately demonstrated, and that they may have evolved their lateral flaps independently from radiodonts, opabiniids, and Pambdelurion through a flattening of the walking lobopods of their ancestors. This theory seems supported by the description of a new kerygmachelid that lacked lobopodous legs. The phylogenetic output of a consensus tree with a 50% majority rule is shown in the cladogram that follows.
Total-group Euarthropoda |
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