About 251mya the Family Prionitidae met in what is now the western USA. This event took place all over the world (? Tethys and northern Panthalassa), but for this report I will stick to the event and those attending in the western US. This Family started with the Genus Meekoceras in the Early Smithian and culminated with the family reunion in the Late Smithian with at least 6 species in 4 genera with a few in open nomenclature.
· Anasibirites Mojsisovics, 1896 2 species
· Hemiprionites Spath, 1929 2 species
· Wasatchites Mathews, 1929 1 species
· Gurleyites Mathews, 1929 1 species
With a few Xenoceltitids and Hedenstroemiids. (See Brayard et al. 2013, Jattiot et al. 2017, Mathews 1929, Smith 1932, for composition of the fauna and Jattiot et al. 2015 for a revision of Anasibirites, Brayard et al. 2020 for a revision of Gurleyites) Recorded in the Thaynes Group, UAZ5 of Jattiot et al. 2017
|Prionitid localities (from Brayard et al 2013)|
CARDIOCERATINAE Siemiradzki, 1891:
About 162mya the Subfamily Cardioceratinae gathered in the Sundance Sea that covered much of Montana and Wyoming along with parts of Utah, Colorado, Idaho, and South Dakota. This reunion started with Quenstedtoceras and Pavloviceras coming in from the north in Montana, and closed with 18 species in 4 genera and 3 subgenera.
· Cardioceras Neumayr & Uhlig, 1881
o Scarburgiceras Buckman, 1924 6 species
o Cardioceras Buckman, 1923 1 species
o Goliathiceras Buckman, 1919 2 species
· Scoticardioceras Buckman, 1925 2 species
· Vertebriceras Buckman, 1920 4 species
· Cawtoniceras Buckman, 1923 3 species
With rare Perisphinctids. (see Imlay 1982, and Reeside 1919 for composition of the fauna, and Howarth 2017 for a revision of the Stephanoceratoidea) This reunion is recorded in the cordatum Zone of the Swift Formation of Montana, the Sundance Formation of Wyoming, Montana, and South Dakota, and the Stump Formation of Utah, Idaho, and Colorado.
|Cardioceratid localities (from Imlay 1982)|
Localities for the reunions in the western US are shown, but the events were probably global.
Brayard, A., Bylund, K. G., Jenks, J., Stephen, D. A., Olivier, N., Escarguel, G., Fara, E. & Vennin, E., 2013, Smithian ammonoid faunas from Utah: implications for Early Triassic biostratigraphy, correlations and basinal paleogeography. Swiss Journal of Paleontology 132:141-219
Brayard, A., Olivier, N., Vennin, E., Jenks, J., Bylund, K., Stephen, D., McShinsky, D., Goudemand, N., Fara, E., Escarguel, G., 2020. New middle and late Smithian ammonoid faunas from the Utah/Arizona border: new evidence for calibrating Early Triassic transgressive-regressive trends and paleobiogeographical signals in the western USA basin. Global and Planetary Change 192
Howarth, Michael K., 2017, Part L, Revised, Volume 3B, Chapter 6: Systematic descriptions of the Stephanoceratoidea and Spiroceratoidea. Treatise Online 84:1–101, 66 fig.
Imlay, R. W., 1982, Jurassic (Oxfordian and Late Callovian) Ammonites from the Western Interior Region of the United States, U.S.G.S. Professional Paper 1232, 44 p., 26 pls.
Jattiot, R., Bucher, H., Brayard, A., Monnet, C., Jenks, J. F. & Hautmann, M., 2015, Revision of the genus Anasibirites Mojsisovics (Ammonoidea): an iconic and cosmopolitan taxon of the late Smithian (Early Triassic) extinction. Papers in Palaeontology 2 (1):155 –188.
Jattiot, R., Bucher, H., Brayard, A., Brosse, M., Jenks, J.F., Bylund, K.G., 2017, Smithian ammonoid faunas from northeastern Nevada: implications for Early Triassic biostratigraphy and correlation within the western USA basin. Palaeontographica A (Paleozoology, Stratigraphy), doi: 10.1127/pala/2017/0070.
Mathews, Asa A. L., 1929, The Lower Triassic Cephalopod Fauna of the Fort Douglas Area, Utah, Walker Museum Memoirs Vol.1 No.1 University of Chicago Press, 46 p., 11 pls.
Reeside, J. B., Jr., 1919, Some American Jurassic Ammonites of the Genera Quenstedticeras, Cardioceras and Amoeboceras, Family Cardioceratidae, U.S.G.S. Professional Paper 118, 64 p., 24 pls.
Smith, J. P., 1932, Lower Triassic Ammonoids of North America, U.S.G.S. Professional Paper 167,199 p., 81 pls.