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By oilshale
Kingdom: Animalia
Phylum: Chordata Haeckel 1874
Class: incertae sedis
Order: Palaeonisciformes
Family: incertae sedis
Genus: Beagiascus
Species: Beagiascus pulcherrimus
Author Citation Mickle, Lund & Grogan 2009
Eon: Phanerozoic
Era: Paleozoic
Period: Carboniferous
Sub Period: Mississippian
Epoch: Late
International Age: Serpukhovian
Big Snowy Group
Heath Formation
Acquired by: Purchase/Trade
Length: 10 cm
Bear Gulch
Fergus County
Montana
United States
Taxonomy according to Mickle et al., 2009.
The University of Montana, UM Paleontology Center website (Browse Collections - College of Humanities and Sciences / UM Paleontology Center - University Of Montana (umt.edu)) lists "Yogoniscus gulo" as an old taxon on some specimens (but not on all specimens) of Beagiascus pulcherrimus. Obviously, confusion has occurred.
Diagnosis from Mickle et al., p. 639: “A lower actinopterygian fish defined by the following combination of characters: elongate fusiform body, narrow in cross section; premaxillae narrowly sutured in midline; nasal notched anteriorly and posteriorly; posterodorsal process of antorbital forms base of posterior nasal notch; frontal with a sinuous sagittal suture; crescent-shaped dermosphenotic; large dermopterotic with a wide posterior plate, laterally spurred, anteromedial process situated within a notch in the frontal; three large suborbitals situated within curve of preoperculum, small fourth suborbital overlapping large suborbital, suborbital between posteroventral infraorbital and maxilla; four infraorbitals – narrow infraorbital ventral to orbit, crescent-shaped posteroventral infraorbital, an intervening element, and T-shaped posterodorsal infraorbital, tapered anterior end of posterodorsal infraorbital comes in contact with tapered posterior end of nasal; mosaic of several small bones in curve of posterodorsal infraorbital for spiracular bone; long maxillary plate; two rows of pointed, posteriorly inclined teeth down length of maxilla; prominent posteroventral process of maxilla; anteriorly inclined hatchet shaped preoperculum; one row of 5 or 6 anteopercular bones along anterior margin of operculum – ventral-most anteopercular bone wider and longer than the others; rectangular, anteriorly inclined operculum with transverse ganoine ridges; rhombic suboperculum with vertical ganoine ridges; total of 14 or 15 branchiostegal rays – five above mandibular corner, 9 or 10 at and below mandibular corner, first branchiostegal twice as high as second; anterior and posterior extrascapular rows sharing median extrascapular (anterior row – three lateral bones, posterior-single bone bearing supratemporal commissure); unsutured postspiracular; one row of rhombic postcleithral scales; narrow ventrolateral flank scales; f ank scales finely pectinated; fan-like pectoral fin; triangular pelvic fin, triangular dorsal and anal fins with posterior edges tapering off gradually; heterocercal caudal fin deeply forked, accessory flap on epicaudal lobe; all fins bear long, stout, overlapping fringing fulcra on leading edges; precaudal ridge scales continuous between the anal and caudal, and dorsal and caudal fins. Meristic, morphometric, and cranial measurements are presented in Tables 9 to 12.”
Line drawing from Mickle et al., 2009, p. 642:
ID by oilshale using Mickle et al., 2009.
Reference:
Mickle, K. E., Lund, R. and Grogan. E. D. (2009): Three new palaeoniscoid fishes from the Bear Gulch limestone (Serpukhovian, Mississippian) of Montana (USA) and the relationships of lower actinopterygians. Geodiversitas 31(3):623-668. DOI: 10.5252/g2009n3a6
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