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  • Beagiascus pulcherrimus Mickle et al. 2009


    Images:

    oilshale

    Taxonomy

    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

    Geological Time Scale

    Eon: Phanerozoic
    Era: Paleozoic
    Period: Carboniferous
    Sub Period: Mississippian
    Epoch: Late
    International Age: Serpukhovian

    Stratigraphy

    Big Snowy Group
    Heath Formation

    Provenance

    Acquired by: Purchase/Trade

    Dimensions

    Length: 10 cm

    Location

    Bear Gulch
    Fergus County
    Montana
    United States

    Comments

    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:

    1742443534_Beagiascuslinedrawing.JPG.29dc177dd4afe38bcd021e30129f2e92.JPG

    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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    What a good piece ....:thumbsu:

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    oilshale

    Posted (edited)

    I am having great difficulty identifying Actinopterygii from Bear Gulch. There are probably more than 60 different species known  by nicknames such as bigeye, garden eel,  worm fin, tube snout, pug nose, long pelvic etc. in the literature, but  only a few are described and not a single one is shown. 
    In particular, the descriptions by Lowney 1980 of the species Mesopoma becatense, Fubarichthys rio, F. prolatus. F. brevisYogoniscus gulo, Rhadinichthys vagusAtracauda lundi etc. are not accessible. The PhD thesis of Karen A. Lowney was never published and the species names seem to be not accepted or used in the scientific literature (but frequently by dealers and collectors). Unfortunately, hardly any illustrations of secured reference specimens can be found on the internet.

    Edited by oilshale

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