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    Tridenticeras peramplum (Lasswitz, 1904)


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    Images:

    Heteromorph
    • Excerpt from W. J. Kennedy (1984): "

       

      Family NOSTOCERATIDAE Hyatt, 1894

      [Jouaniceratidae Wright, 1952, p. 218; Bostrychoceratinae Spath, 1953, p. 16; Emperoceratinae Spath, 1953, p. 17; Hyphantoceratinae Spath, 1953, p. 16]

       

      Genus TRIDENTICERAS Wiedmann, 1962

      Type species. Turrilites tridens Schlüter, 1876, p. 136, pl. 35, fig. 9; pl. 36, fig. 1; by original designation.

       

      Diagnosis. Turricone, ornamented by strong, flared ribs with three rows of tubercles, the lower two close together, and with non-tuberculate finer ribs between.

       

      Discussion. Schlüter figured only one specimen of his T. tridens, but Wiedmann (1962, p. 193, pl. 11, figs. 3, 7) has illustrated two views of a Spanish specimen agreeing closely with the original. To this can be added a specimen from the Coniacian of Terradillos de Sedano, Burgos, Spain, in the Oxford University Museum Collection (no. KZ14152) and two specimens from the Coniacian of Zûazû Navarra, Spain, Kindly loaned by Dr. G. Ernst of Braunschweig (casts are OUM KZ19173-19174). These show convincingly that, rather than being a survivor of the Turrilitidae which are otherwise restricted to the Albian and Cenomanian, Tridenticeras is a recoiled nostoceratid. It is suggested that the origin of the genus lies in Hyphantoceras Hyatt, 1900 or an allied genus. Turonian species of Hyphantoceras have a loosely and irregularly coiled spire and a recurved body chamber. Ornament of the spire consists of flared ribs with up to four rows of tubercles, with finer, non-tuberculate ribs between. Evolution simply involved recoiling, a trend widely shown by other heteromorphs.

         Weidmann also referred Turrilites peramplus Lasswitz (1904, p. 14, pl. 14, fig. 1) to the genus, while it is here suggested that T. varians Schlüter, 1876 (p. 137, pl. 35, figs. 11-13; pl. 36, figs. 2-5) is a further representative. This species has early whorls ornamented by fine, non-tuberculate ribs and periodic stronger trituberculate ribs, and a body whorl with flared, feebly tuberculate ribs and weaker non-tuberculate ribs between. This change in ornament matches that shown on adult H. reussianum (d'Orbigny, 1850), while the disparate sizes of the two adult specimens of Tridenticeras varians illustrated by Schlüter indicate dimorphism in the genus.

       

      Occurrence. Coniacian of Germany, France, northern Spain, and Texas, U.S.A."

       

       

      Personal notes: More information on the genus Tridenticeras can be found here and here.

       

      REFERENCES

       

       

      Wiedmann, J. (1962). Die Gabbioceratinae Breistroffer (Notizen zur Systematik der Kreideammoniten II.). Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen, Bd. 115, p. 1–43.

       

      Ulrich Kaplan und William James Kennedy (1994). Ammoniten des westfälischen Coniac. Geologie und Paläontologie in Westfalen, Heft 31, 155 S. 

       

      Zdenek Vašíček (1990). Coniacian ammonites from Štíty in Moravia (Czechoslovakia). Sbornik geologickych ved, Paleontologie 32, Pages 163-195. 

       

      W. J. Kennedy (1984). Systematic Paleontology and Stratigraphic Distribution of the Ammonite Faunas of the French Coniacian. Palaeontological Association, London, Special Papers in Palaeontology, No. 31. 

       

      Barbra L. Emerson, John H. Emerson, Rosemary E. Akers and Thomas J. Akers (1994). Texas Cretaceous Ammonites and Nautiloids. Paleontology Section, Houston Gem and Mineral Society, Texas Paleontology Series Publication No. 5, 438 pp.

    Taxonomy

    Kingdom: Animalia
    Phylum: Mollusca
    Class: Cephalopoda
    Order: Ancyloceratina
    Family: Nostoceratidae
    Genus: Tridenticeras
    Species: T. peramplum
    Author Citation Lasswitz, 1904

    Geological Time Scale

    Eon: Phanerozoic
    Era: Mesozoic
    Period: Cretaceous
    Epoch: Late
    International Age: Coniacian (middle/late)

    Stratigraphy

    Austin Group
    Atco Formation

    Provenance

    Collector: Me
    Date Collected: 09/08/2017
    Acquired by: Field Collection

    Dimensions

    Height: 4.3cm
    Diameter: 1.9cm

    Location

    Texas
    United States

    Comments

    Excerpt from W. J. Kennedy (1984): "

     

    Family NOSTOCERATIDAE Hyatt, 1894

    [Jouaniceratidae Wright, 1952, p. 218; Bostrychoceratinae Spath, 1953, p. 16; Emperoceratinae Spath, 1953, p. 17; Hyphantoceratinae Spath, 1953, p. 16]

     

    Genus TRIDENTICERAS Wiedmann, 1962

    Type species. Turrilites tridens Schlüter, 1876, p. 136, pl. 35, fig. 9; pl. 36, fig. 1; by original designation.

     

    Diagnosis. Turricone, ornamented by strong, flared ribs with three rows of tubercles, the lower two close together, and with non-tuberculate finer ribs between.

     

    Discussion. Schlüter figured only one specimen of his T. tridens, but Wiedmann (1962, p. 193, pl. 11, figs. 3, 7) has illustrated two views of a Spanish specimen agreeing closely with the original. To this can be added a specimen from the Coniacian of Terradillos de Sedano, Burgos, Spain, in the Oxford University Museum Collection (no. KZ14152) and two specimens from the Coniacian of Zûazû Navarra, Spain, Kindly loaned by Dr. G. Ernst of Braunschweig (casts are OUM KZ19173-19174). These show convincingly that, rather than being a survivor of the Turrilitidae which are otherwise restricted to the Albian and Cenomanian, Tridenticeras is a recoiled nostoceratid. It is suggested that the origin of the genus lies in Hyphantoceras Hyatt, 1900 or an allied genus. Turonian species of Hyphantoceras have a loosely and irregularly coiled spire and a recurved body chamber. Ornament of the spire consists of flared ribs with up to four rows of tubercles, with finer, non-tuberculate ribs between. Evolution simply involved recoiling, a trend widely shown by other heteromorphs.

       Weidmann also referred Turrilites peramplus Lasswitz (1904, p. 14, pl. 14, fig. 1) to the genus, while it is here suggested that T. varians Schlüter, 1876 (p. 137, pl. 35, figs. 11-13; pl. 36, figs. 2-5) is a further representative. This species has early whorls ornamented by fine, non-tuberculate ribs and periodic stronger trituberculate ribs, and a body whorl with flared, feebly tuberculate ribs and weaker non-tuberculate ribs between. This change in ornament matches that shown on adult H. reussianum (d'Orbigny, 1850), while the disparate sizes of the two adult specimens of Tridenticeras varians illustrated by Schlüter indicate dimorphism in the genus.

     

    Occurrence. Coniacian of Germany, France, northern Spain, and Texas, U.S.A."

     

     

    Personal notes: More information on the genus Tridenticeras can be found here and here.

     

    REFERENCES

     

     

    Wiedmann, J. (1962). Die Gabbioceratinae Breistroffer (Notizen zur Systematik der Kreideammoniten II.). Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen, Bd. 115, p. 1–43.

     

    Ulrich Kaplan und William James Kennedy (1994). Ammoniten des westfälischen Coniac. Geologie und Paläontologie in Westfalen, Heft 31, 155 S. 

     

    Zdenek Vašíček (1990). Coniacian ammonites from Štíty in Moravia (Czechoslovakia). Sbornik geologickych ved, Paleontologie 32, Pages 163-195. 

     

    W. J. Kennedy (1984). Systematic Paleontology and Stratigraphic Distribution of the Ammonite Faunas of the French Coniacian. Palaeontological Association, London, Special Papers in Palaeontology, No. 31. 

     

    Barbra L. Emerson, John H. Emerson, Rosemary E. Akers and Thomas J. Akers (1994). Texas Cretaceous Ammonites and Nautiloids. Paleontology Section, Houston Gem and Mineral Society, Texas Paleontology Series Publication No. 5, 438 pp.

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