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Late Paleocene examples of residual coloration and embryonic features in juvenile marine mollusks from Northwest Louisiana

Lloyd N. Glawe, John F. Anderson, and Dennis E. Bell

Plain Language Abstract

Core samples from rock layers beneath the surface of northwest Louisiana contain well-preserved sea shells that are at least 55 million years old. The fossil shells display pale shades of yellow, orange, and red that are similar to the coloration of slightly weathered seashells found along present-day beaches of the Gulf of Mexico. Many of the shells exhibit larval features.

Resumen en Español

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Traducción: Enrique Peñalver

Résumé en Français

Exemples de coloration résiduelle du Paléocène supérieur et caractéristiques embryonnaires chez des mollusques marins juvéniles du nord-ouest de la Louisiane

Les mollusques marins ont joué un rôle important dans la résolution de la stratigraphie du Paléogène de la Plaine Côtière du Golfe dans le sud des Etats-Unis. L'enquête suivante documente les occurrences de microscopiques spécimens pré-adultes d'espèces de mollusques du Paléocène supérieur, dans un ensemble presque continu, pratiquement non altérés, de carottage de sous-sol de 2158 pieds (658 mètres) de longueur totale du nord-ouest de la Louisiane. La durée de la séquence de carottage est estimé de s'étendre à partir d'environ 60 Ma à environ 55 Ma; les couches contiennent la zone de Planorotalites pseudomenardii trouvée dans le monde entier au Paléocène. Bien qu'âgé de millions d'années, les coquilles des mollusques de notre étude montre une coloration partiellement dégradé, allant du jaune pâle, à l'orange pâle, au rouge pâle. L'origine probable de la coloration est biologique; la coloration conservée est attribué à un enfouissement rapide dans un environnement sédimentaire deltaïque. Certaines coquilles présentent des caractéristiques embryonnaires fragiles, y compris des protoconches de gastéropodes et des prodissoconches de bivalves. Cette enquête définit une limite paléontologique importante au sein du Paléocène supérieur; étendant la gamme stratigraphique connu pour neuf espèces de mollusques en Louisiane; documente une série stratigraphique durant environ 600000 années pour l'huître guide-fossiles, Odontogryphaea thirsae (Gabb, 1861); et contribue à la paléontologie et la paléobiologie de 25 espèces de mollusques du Paléocène supérieur, en décrivant pour la première fois la coloration résiduelle de leur coquille et / ou des caractéristiques embryonnaires.

Mots-clés: Paléocène; coloration résiduelle; caractéristiques embryonnaires; Mollusques marins; Zone Planorotalites pseudomenardii; Wilcox Group

Translator: Kenny J. Travouillon

Deutsche Zusammenfassung

Beispiele von Restfärbung und Embryo-Merkmalen in juvenilen marinen Mollusken aus dem späten Paläozän von Nordwest-Louisiana

Marine Mollusken haben einen wichtigen Beitrag geleistet, die paläogene Stratigraphie der Küstenebene des Golfes der südlichen Vereinigten Staaten zu erschließen. Die vorliegende Untersuchung befasst sich mit dem Auftauchen von mikroskopisch großen, prä-adulten Exemplaren von spätpaläozänen Molluskenarten. Diese stammen aus einer Sequenz nahezu durchgehender, quasi verwitterungsfreier oberflächennaher Kerne aus dem nordwestlichen Lousiana mit einer Gesamtlänge von 659 Metern (2158 feet). Die Zeitdauer, die durch diese Sequenz abgebildet wird, dürfte schätzungsweise von 60 – 55 Mio Jahre reichen, die Schichten enthalten die weltweit im Paläozän vorkommende Planorotalites pseudomenardii-Zone. Obwohl Millionen von Jahre alt, zeigen die Mollusken-Schalen unserer Studie nur teilweise abgebaute Farben, die von blaßgelb über schwachorange bis schwachrot reichen. Die Färbung ist wahrscheinlich biologischen Ursprungs; die Erhaltung der Färbung wird einer schnellen Zuschüttung in einer Delta-Umgebung mit viel Sediment zugeschrieben. Einige der Exemplare zeigen fragile embryogene Züge, z.B. Protoconche von Gastropoden und Prodissoconche von Bivalven. Diese Untersuchung beschreibt eine wichtige paläontologische Grenze im späten Paläozän; erweitert das bekannte stratigraphische Vorkommen von neun Mollusken-Arten in Louisiana; dokumentiert eine stratigraphische Reichweite von ca. 600.000 Jahren für die Auster Odontogryphaea thirsae (Gabb, 1861), ein Leitfossil; und trägt zur Paläontologie und Paläobiologie von 25 Mollusken-Arten des späten Paläozäns bei, indem erstmalig die Restfarben der Schalen und/oder embryogene Merkmale beschrieben werden.

Schlüsselwörter: Spätes Paläozän, Restfarbe, Embryo-Merkmale, marine Mollusken, Planorotalites pseudomenardii Zone; Wilcox Gruppe

Translator: Anke Konietzka

Arabic

Translator: Ashraf M.T. Elewa

 

 

FIGURE 1. Geographic setting and location of the study well in northwest Louisiana. The Carter #2 Well location is indicated by 425-1.

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FIGURE 2. Occurrences of Paleocene Wilcox molluscan species by their drilling depths in feet at the Carter #2 Core Hole (Sabine Parish, Louisiana). The first occurrence for each species encountered in the cores is circled in red. Occurrence data are listed in Table 1. Stratigraphic terminology and Geologic Ages are explained in the text.

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FIGURE 3. Residual coloration and embryonic features of Paleocene Wilcox juvenile mollusks. All figured specimens are from Carter #2 core, Sabine Parish, Louisiana (except for 3.32, 3.33). Descriptions of shell coloration are made by comparisons with Geological Society of America Rock-Color Chart (1970). Figured specimens: 1, bivalve Calorhadia aldrichiana (Harris, 1897); LV interior with light brownish gray coloration (GSA R-CC 5 YR 6/1), height 1.79 mm, USNM 546627, drilling depth 1507 ft, Marthaville Fm., showing prominent taxodont hinge and subtle curvature within shell posterior for siphons; 2, LV exterior of previous specimen showing prominent growth lines and produced posterior; 3, bivalve Nuculana corpulentoidea ( Aldrich, 1895); double valve, LV exterior view with grayish yellow coloration (GSA R-CC 5 Y 8/4), height 1.01 mm, USNM 546628, drilling depth 715 ft, Pendleton Fm., medial portion of valve corpulent with concentric ridges; 4, RV view of previous specimen with broken ventral margin, valve height 0.94 mm; 5, gastropod Adeorbis cf. A. sylvaerupis Harris, 1899; apical view, diameter 3.66 mm, USNM 546629, drilling depth 2327 ft, Lower Wilcox, showing spiral and growth line ornamentation; protoconch (828 microns in diameter) recognizable in the center by smooth whorls that increases in size with growth; 6, umbilical view of previous specimen that reveals the protoconch with three or four whorls, a sediment-filled shell, and broken aperture; 7, bivalve Corbula sp. of Barry and LeBlanc, 1942; RV exterior, height 3.89 mm, USNM 546630, drilling depth 2327 ft, Lower Wilcox; shell exterior of this unnamed species is characterized by fine radial ornamentation and by prominent concentric threads along ventral margin; Barry and LeBlanc report this species from the Logansport Fm.; 8, bivalve Corbula cappa Barry, 1942 in Barry and LeBlanc, 1942; RV interior of an incomplete specimen, USNM 546631, drilling depth 1805 ft, Lower Wilcox, showing hinge with prominent socket; 9, bivalve Corbula cappa Barry, 1942 in Barry and LeBlanc, 1942; LV exterior, height 3.31 mm, USNM 546632, drilling depth1805 ft, Lower Wilcox, with prominent concentric ridges; 10, gastropod Epitonium cf. E. multiliniferum Aldrich, 1921; apertural view with grayish orange coloration (GSA R-CC 10 YR 7/4), height 0.52 mm, USMN 546633, drilling depth1315 ft, Pendleton Fm., showing sinuous axial ornamentation and a protoconch; 11, bivalve Macrocallista sp. RV interior, height 0.97 mm, USNM 546634, drilling depth 667 ft, Pendleton Fm., showing blade-like cardinal and lateral teeth; 12, RV exterior of previous specimen showing indistinct growth lines and a prosogyral beak; 13, bivalve Trinacria cf. T. microcancellata Barry, 1942 in Barry and LeBlanc, 1942; LV interior with coloration, height 1.12 mm, USNM 546635, drilling depth 1507 ft, Marthaville Fm., specimen with “taxodont” dentition; 14, LV exterior of previous specimen showing prosogyral beak and prominent growth lines, but without radial ornamentation; 15, gastropod Skenae pignus (Gregorio, 1890), convex side with grayish orange coloration (GSA R-CC 10 YR 7/4), diameter 0.55 mm, USNM 546636, drilling depth 1006 ft, Pendleton Fm., showing a nearly planispiral coil with faint growth lines; 16, concave side of previous specimen; 17, scaphopod Cadulus abruptus Meyer and Aldrich, 1886; side view, height 2.07 mm, USNM 546637, drilling depth 1507 ft, Marthaville Fm., showing a slightly curved shell with growth lines and broken aperture; 18, scaphopod Dentalium microstria Heilprin, 1881; side view with grayish orange coloration (GSA R-CC 10YR 7/4), height 1.52 mm, USNM 546638, drilling depth 2324 ft, Lower Wilcox, showing prominent radial ribs; 19, gastropod Turritella cf. T. eurynome Whitfield, 1865 side view of broken specimen, height 2.76 mm, USNM 546639, drilling depth 713 ft, Pendleton Fm., characterized by three subequal spiral lirae per whorl; 20, bivalve Nucula ovula Lea, 1833; LV interior, height 1.79 mm, USNM 546640, drilling depth 1496 ft, Pendleton Fm., showing prosogyral, ovate shell with taxodont hinge and pale red coloration (GSA R-CC 10R 6/2); ventral margin exhibits short, radial ribbing; 21, LV exterior of previous specimen shows irregular concentric ornamentation, faint radial lines, and an internal mold of prodissoconch; 22, gastropod sp. umbillical view, diameter 1.10 mm, USNM 546641, drilling depth 1351 ft, Pendleton Fm., transparent, cinder cone volcano-shaped shell with very faint growth lines and a deep umbilicus; 23, gastropod Cerithiella sp. apertural view with bluish white coloration (GSA R-CC 5B 9/1), height 3.11 mm, USNM 546642, drilling depth 987 ft, Pendleton Fm., showing spiral and radial ornamentation and a protoconch with different axis of coiling than the conch; 24, gastropod Rudiscala harrisi Palmer, 1937; apertural view with yellowish gray coloration (GSA R-CC 5Y 8/1), height 0.83 mm, USNM 546643, drilling depth 1612 ft, Lower Wilcox, showing curved axial ribs and an apertural lip; 25, gastropod Melanella wheeleri Palmer, 1937; apertural view with yellowish gray coloration (GSA R-CC 5Y 8/1), height 0.55 mm, USNM 546644 drilling depth 1507 ft, Marthaville Fm., exhibiting a sutural collar; 26, bivalve Venericardia densata pendletonensis Gardner and Bowles, 1939; interior with grayish orange coloration (GSA R-CC 10YR 7/4), height 1.79 mm, USNM 546645,depth 668 ft, Pendleton Fm., showing internal ribbing along ventral margin; 27, RV exterior of previous specimen exhibiting denticulations on ribs; 28, gastropod Dorsanum scalatum (Heilprin, 1891); apertural view with light brown (GSA RCC 5YR 6/4) and grayish orange (GSA 10YR 7/4) coloration on shell, height 2.00 mm, USNM 546646, drilling depth 987 ft, Pendleton Fm., showing development of external ornamentation on the whorls from radial lines to spiral lines to nodes; small, internal nodes are visible on the outer lip of aperture; 29, gastropod Ringicula butleriana Aldrich, 1895; apertural view, height 1.52 mm, USNM 546647, drilling depth 2299 ft, Lower Wilcox, showing spiral grooves on shell exterior, prominent columellar folds; 30, gastropod Buccitriton sagenum (Conrad, 1833); apertural view with grayish orange coloration (GSA R-CC 10YR 7/R), height 2.90 mm, USNM 546648, drilling depth 666 ft, Pendleton Fm., showing a similar development of ornamentation as observed in Dorsanum scalatum except B. sagenum lacks the development of prominent nodes on whorls; 31, gastropod Atys cf . A. robustoides Aldrich, 1895; apertural view with grayish orange coloration (GSA R-CC 10 YR 7/4), height 1.24 mm, USNM 546649, drilling depth 666 ft, Pendleton Fm, showing loose coiling with spiral grooves in outer shell; axial liration in posterior and sigmoid liration in anterior; 32, bivalve Odontogryphaea thirsae (Gabb, 1861); RV interior, height 2.20 mm, ULM-38, Nanafalia Landing on Tombigbee River, Alabama, Nanafalia Fm., barely showing posterior adductor muscle scar; 33, RV exterior of previous specimen showing a low convex shell with internal mold of prodissoconch and a tapered bore hole; 34, bivalve O. thirsae (Gabb, 1861); RV exterior, height 1.00 mm, ULM-40, drilling depth 1507 ft, Marthaville Fm., exhibiting an early dissoconch stage (juvenile) with an attached prodissoconch (height 0.42 mm); 35, gastropod Natica aperta Whitfield, 1865; apertural view with grayish orange coloration (GSA R-CC 10 YR 7/4), height 1.70 mm, USNM 546650, drilling depth 668 ft, Pendleton Fm., showing a low trochospiral coil slightly flattened on top, and an upper columellar lip reflected over the umbilicus; aperture reveals a hole in the body whorl and an inner shell layer with crinkled texture; 36, gastropod Teinostoma barryi LeBlanc, 1942; umbilical view with somewhat iridescent coloration, maximum diameter 2.62 mm, USNM 546651, drilling depth 713 ft, Pendleton Fm., shell exhibits low, curved ridges extending from a callous-filled umbilicus toward the shell margin where spiral punctate lines are present; outer lip of aperture is missing. Scale bars equal 1 mm unless labeled otherwise. Figured specimens are deposited in the U.S. National Museum (USNM), Washington, DC and in the University of Louisiana Monroe (ULM) Natural History Museum, Monroe, LA. Digital images are produced by light photography, except for SEM image 3.32. Images 3.33 and 3.34 are from Glawe et al. (2011). Original descriptions of species are indicated by author and year of publication; the complete bibliographic sources are included in the REFERENCES section.

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glaweLloyd N. Glawe
Museum of Natural History
University of Louisiana at Monroe
Monroe, Louisiana 71209-0504
USA
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Lloyd N. Glawe is a retired Professor of Geology at the University of Louisiana in Monroe. He has expertise in the paleontology of mollusks and the Paleogene stratigraphy of the Northern Gulf Coastal Plain, USA and has published on the growth stages and morphologic variation in Paleogene pectens and oysters. He has documented an example of speciation in the genus Pecten. Presently, he is preparing a substitute reference section for the Paleogene Wilcox Group in Louisiana.

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andersonJohn F. Anderson
Department of Atmospheric Science, Earth Science, and Physics
University of Louisiana at Monroe
Monroe, Louisiana 71209-0550
USA
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J.F. Anderson is Associate Professor of Physics at the University of Louisiana-Monroe in Monroe, LA. Dr. Anderson is a researcher in depolarized light scattering of proteins and organic solvents, mathematical modeling of juvenile to adult progression of the oyster, O. thirsae (Gabb), and light and electron imaging of fossil sea shells.

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bellDennis E. Bell (corresponding author)
Department of Biology
University of Louisiana at Monroe
Monroe, Louisiana 71209-0520
USA
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Dennis Bell is an Instructor in the Department of Biology at the University of Louisiana at Monroe. He is a systematic botanist and the Collections Manager of the ULM Herbarium (Index Herbariorum designation - NLU). His contributions to this manuscript include: Light microscopy, graphic layout and design of figures and tables (Photoshop 3), as well as limited editorial contributions.

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TABLE 1. Occurrence data by drilling depths in feet for Paleocene molluscan species or species groups in the Carter #2 Wilcox cores from Sabine Parish, Louisiana. Plots of occurrence data are shown in Figure 2. Most of the species are illustrated in Figure 3.

Adeorbis cf. A. sylvaerupis Harris, 1899: 2327;

Atys cf. A. robustoides Aldrich, 1895: 666, 668, 713, 715, 1496;

Buccitriton sagenum (Conrad, 1833): 666, 667, 668, 713, 717, 987,993, 1006, 1015, 1496, 1612, 2246;

Cadulus abruptus Meyer and Aldrich, 1886: 618, 1316, 1464, 1508, 1511, 2298, 2324, 2353;

Calorhadia aldrichiana (Harris, 1897): 616, 618, 667, 1006, 1495, 1508, 1666, 2346, 2353;

Cerithiella sp.: 987;

Corbula sp : 2326, 2327;

Corbula cappa Barry, 1942 in Barry and LeBlanc, 1942: 1006, 1351, 1397, 1805, 2327;

Dentalium microstria Heilprin, 1881: 2324, 2325, 2344;

Dorsanum scalatum (Heilprin, 1891): 668, 986, 987, 1508;

Epitonium cf. E. multiliniferum Aldrich, 1921: 1315, 1509, 1611;

Gastropod sp.a: 1351, 1508, 1510;

Macrocallista sp.: 666, 667, 715, 1496;

Melanella wheeleri Palmer, 1937: 717, 993, 1006, 1316,1508, 2299;

Natica aperta Whitfield, 1865: 666, 667, 668, 713, 715, 717, 986, 987, 993, 1006, 1496;

Nucula ovula Lea, 1833: 986, 987, 1316, 1488, 1496, 1507, 1612, 2324, 2344, 2353;

Nuculana corpulentoidea (Aldrich, 1895): 666, 713, 715, 986, 1316;

dontogryphaea thirsae (Gabb, 1861): 1316, 1332, 1482, 1491, 1508; 1611?

Ringicula butleriana Aldrich, 1895: 987,2299, 2324;

Rudiscala harrisi Palmer, 1937: 1612;

Skenae pignus (Gregorio, 1890): 1006, 1666;

Solariella sp.: 987;

Teinostoma barryi LeBlanc, 1942 in Barry and LeBlanc, 1942: 713;

Tellina cf . T. bellsiana Aldrich, 1921: 667;

Trinacria cf. T. microcancellata Barry, 1942 in Barry and LeBlanc, 1942: 1508;

Turbonilla sp.: 668, 715, 986;

Turritella spp.: 713, 987, 1006, 1228, 1332;

Venericardia spp.: 666, 667, 668, 713, 715, 717, 986, 993, 1036, 1262, 1316, 1482, 1491, 1510, 2246.