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1
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Relationships of the Devonian Strobilepis and related Pensylvanian problematica

100%
Hoare R. D., Mapes R. H.
Acta Palaeontologica Polonica
|
1995
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tom 40
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nr 2
111-128
Reinterpretation of the North American Strobilepis spinigera Clarke 1888 from the Devonian and the find of Diadeloplax paragrapsima gen. et sp. n. from the Pennsylvanian provide the basis for the recognition of a new class of uncertain affinity, Multiplacophora. The range of the class is Middle Devonian (Erian) to Pennsylvanian (Morrowan). Multiplacophora differ from the order Hercolepadida and the classes Thambetolepida and Polyplacophora in the number, shape, and arrangement of plates; the presence of large spines; and the complexity of internal canal systems in the plates and spines.
2
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Late Paleozoic turrilepadid machaeridians from North America

81%
Hoare R. D., Mapes R. H., Yancey T. E., Nestell M. K.
Acta Palaeontologica Polonica
|
1996
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tom 41
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nr 2
127-145
Turrilepadids are not uncommon in late Paleozoic shales being often associated with ostracodes, foraminifers, and minute molluscs. In North America they range from the late Missippian (Chesterian) to early Permian (Leonardian). Sclerites of the inner scleritome row are more common than outer sclerites. Some clusters have been found. Sclerite consists of two layers with the thicker, lower layer penetrated by a transverse tubular structures oriented perpendicular to the sclerite surface, which may represent canals related to the papillae on the inner surface of the sclerite. Turrilepas Lepros sp. n., T. trigoniodes sp. n., T. asketos sp. n., Clarkeolepis alloeospinosa sp. n., and Ambonlepidas petalos gen. et sp. n. are proposed.
3
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Exceptional cameral deposits in a sublethally injured Carboniferous orthoconic nautiloid from the Buckhorn Asphalt Lagerstatte in Oklahoma, USA

81%
Seuss B., Mapes R. H., Klug C., Nutzel A.
Acta Palaeontologica Polonica
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2012
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tom 57
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nr 2
The cameral and intrasiphonal deposits of a Pennsylvanian straight nautiloid (Pseudorthoceratidae) are studied in order to understand the formation of these deposits. The specimens from the Buckhorn Asphalt deposit (Oklahoma) are exceptionally preserved including original aragonite and microstructures. The specimen investigated survived a predation attempt and shows bite marks on the phragmocone. This is the second report of an ectocochleate cephalopod and first report of an orthoconic nautiloid which survived massive damage of conch and siphuncle. For the first time, a high−magnesium calcitic mineralogy of cameral deposits is documented. These deposits were formed in alternation with aragonite in a chamber which was perforated during the unsuccessful predation attempt. The animal formed the chamber deposits throughout its entire lifetime and the siphuncle played a major role in formation of the cameral deposits.
4
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Dorsal shell wall in ammonoids

80%
Kulicki C., Tanabe K., Landman N. H., Mapes R. H.
Acta Palaeontologica Polonica
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2001
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tom 46
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nr 1
In ammonoids, a soft body organ (possibly a supracephalicmantle fold), extending from the conch aperture secreted aragonitic wrinkles, forming a layer on the surface of the preceding whorl. The dorsal shell wall consists of the outer and inner components which were deposited sequentially, beginning at the aperture of the living chamber inwards. The dorsal wall attains its full thickness near the last septum. The outer component is visible in the apertural region and is smooth or wrinkled; it is called the wrinkled layer in the latter case. The wrinkles may be continuous, interrupted, or form isolated patches arranged in rows. The wrinkles are usually triangular in cross section. A further stage of dorsal wall development involves filling in the space between the apices of triangles, and then adding one or more inner prismatic layers from the inside of the living chamber. This pattern occurs at least in the postembryonic stage of all genera studied, belonging to five suborders of Ammonoidea ranging from Late Carboniferousto Late Cretaceous. In many genera, the outer component of the dorsal shell wall exhibits remarkable ontogenetic change in its ultrastructure and microornament. It may be compared with the black film of Recent Nautilus shells with respect to place of formation. The outer component of the ammonoid dorsal shell wall is regarded as a product of organic secretion and carbonate precipitation in the area of the supracephalic mantle fold.
5
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Chaetognath grasping spines from the Upper Mississippian of Arkansas [USA]

80%
Doguzhaeva L. A., Mutvel H., Mapes R. H.
Acta Palaeontologica Polonica
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2002
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tom 47
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nr 3
Previously unidentified tiny (about 0.5 mm in length), hollow, gently curved, serrated spines probably originally composed of horny, organic fibers from the Upper Mississippian (Middle Chesterian = Namurian A equivalent or lower Serpukhovian) of Arkansas (USA) are described, and their probable chaetognath affinities are discussed. The specimens are preserved in an oval accumulation (about 15 mm long and 6 mm wide) of approximately 200 specimens within a small (about 25 mm in length) phosphatic concretion. For comparison, the grasping spines of the Recent chaetognath Eukrohnia hamata were examined. The Arkansas specimens are named Eoserratosagitta serrata gen. et sp. nov., and this genus is assigned to the Phylum Chaetognatha. The Upper Mississippian spines are also compared with protoconodonts. This comparison supports the hypothesis that the chaetognaths may have existed in the Cambrian.
6
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Piggyback whorls: A new theoretical morphologic model reveals constructional linkages among morphological characters in ammonoids

71%
Ubukata T., Tanabe K., Shigeta Y., Maeda H., Mapes R. H.
Acta Palaeontologica Polonica
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2008
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tom 53
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nr 1
A new theoretical morphological model is proposed for the analysis of growth, form and morphospace of ammonoid shells. In this model, the shape of a radial cross section through the shell is simulated by “piggybacking” of successive whorls. The “piggyback whorls model” is defined in terms of the enlarging rate of the perimeter and the proportion of the dorsal wall to the whorl periphery, if an isometric relationship is assumed between perimeter and area of the cross−sectioned whorl. Allometric coefficients on these growth parameters determine how compressed and evolute shells are formed. The present model successfully reproduced some correlations among purely geometric variables that have been reported in previous works and were also observed in our biometric analyses. This model yields a hypothesis of “constructional linkages” between aperture shape and coiling geometry that might provide a functional coupling between hydrostatic and hydrodynamic characters. The model may partly explain Buckman’s Law of Covariation between rib features and shell shapes.
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