Eburneopecten burlesonensis (Harris, 1919)
HARRIS, G. D. 1919. Pelecypoda of the St. Maurice and
Claiborne Stages. Bulletins of American Paleontology, 6 (31): 1-268, pls. 1-59. [p. 26, pl. 14, figs. 11-13]
1919 Pecten clarkeanus var. burlesonensis Harris, 1919
G. D. Harris, 1919, plate 14.
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«P. (Chlamys) clarkeanus Dall, Trans. Wag. Ill, p. 739, '98.
P. deshayesii Heilp., Proc. Phila. Acad. Nat. Sci., 1890, p. 403. P. deshayesi Kennedy, Proc. Phila. Acad., &c., '95. This is the form in Texas that has usually passed under the name of deshayesi in reports on Eocene paleontology of the State, but it is really much more nearly related to clarkeanus as described elsewhere in these Bulletins. However, it is generally somewhat higher, or narrower with a less expanding umbonal angle, thicker or heavier, and with more pronouncedly radiately sculptured than clarkeanus. The surface about the umbones when smooth have a somewhat worn appearance without the fine umbonal radiation and the Camptonectes marking so well shown in clarkeanus. The only reason for referrring this to clarkeanus at all, is that, although it is generally of the rather sharply ribbed type, it does show, say at Burleson's Bluff, a vast range in surface markings both as to number, strength and extent of ribs. In this respect it resembles clarkeanus. It will be interesting to note in the future the characteristics of the related types found in Louisiana and Mississippi. Type.— Burleson Shell Bluff, C. U. Mus. Horizon.— St. Maurice Eocene. Specimens figured.— Fig. 11, loaned from U. S.Nat. Mus. Figs. 12, 13, deposited in C. U. Paleont. Mus. Localites.— Burleson Shell Bluff, Collier's Ferry or Black Bluff shoals and Smithville, Tex.» GILBERT DENNISON HARRIS, 1919
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«In the present study, the tribe Eburneopectinini is limited to the genus Eburneopecten because of morphological and stratigraphic evidence that this genus evolved from coarsely ribbed Dhondtichlamys in the early to mid-Eocene of eastern North America and is phylogenetically independent of so-called "Eburneopecten" in Europe (Fig. 1.2, Node E1 compared to A6). Well-preserved specimens of E. scintillatus consistently display fine radial costellae on the left beak that are ontogenetically decoupled from later costae that may appear near the ventral margin. The species retains costae throughout ontogeny on its right anterior auricle, whereas the costae on other auricles are absent or limited to early ontogeny. Similar decoupling of ribbing occurs within the range of variation of two older species that resemble E. scintillatus, and they are included here in Eburneopecten. One of these is E. clarkeanus (Aldrich, 1895) from the Cook Mountain Formation of Alabama of Bartonian age; the other is E. burlesonensis (Harris, 1919) from the Weches Formation of Texas of middle Lutetian age. The latter, older species resembles Dhondtichlamys in having strong steep-sided plicae but differs in having much finer antimarginal microsculpture in the rib interspaces. Both of these species exhibit great variation in the degree of rib interruption, with some specimens approaching the nearly smooth condition of Eburneopecten scintillatus. (See illustrations of these species in Harris 1919, pI. 14,
figs. 11-13 and pI. 15, figs. 8-13.)» WALLER, T. R. 2006. New Phylogenies of the Pectinidae (Mollusca: Bivalvia): reconciling Morphological and Molecular Approaches. In: S.E. Shumway & G.J. Parsons (Ed.), 2006: Scallops: Biology, Ecology and Aquaculture, 1-44, figs. 1.1-1.4. [p. 14, 15]
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Figure 1.2. A phylogeny of the six tribes of the subfamily Palliolinae.
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"Type.— Burleson Shell Bluff, Cornell University Museum.
"Horizon.— St. Maurice Eocene." Harris, 1919. Chlamys burlesonensis (Harris) described from Burleson Bluff apparently includes a hybrid complex of forms ranging broadly from the strongly ribbed P. clarkeanus Aldrich type to Eburneopecten scintillatus var. corneoides Harris. The more strongly and regularly sculptured forms may approach Chlamys wahtubbeana Dall (PI. 10, fig. 24). The ribbing is perhaps the most obvious of the variable features. This may be decided and persistent from the umbones to the base. The umbones and the marginal area may be ribbed, while the intermediate surface may be smooth except for incremental and Camptonectes-Iike sculpture. Ribbing may be absent on the umbones but developed either abruptly or gradually at some distance away from them. Forms not fully developed may therefore be devoid of ribbing. The sculpture of the ears varies with that of the disk and is strongest on those forms in which ribbing is best developed. The Camptonectes-like sculpture is beautifully shown in fresh forms.
Although Chlamys burlesonensis exhibits so wide a range in number and complexity of ribs, in the aggregate of characters the species is well defined and readily discriminated. The shells are of medium size, about 20 millimeters high and almost 20 millimeters wide, but thinner than the average. The apical angle is about 90°. The disk is closely corrugated with rounded ribs which mayor may not have their beginnings at the umbones. They may increase by intercalation or they may bifurcate toward the ventral margin. The submargins are narrow and not radially striate. The auricles are of moderate dimensions, and the 2 to 5 Iirae which thread them are fine to rather coarse. On the Brazos River in east-centrlil Texas, Chlamys burlesonensis is characteristic of a 20-foot zone at the base of the Weches member of the Mt. Selman formation. In Nuevo Le6n, the individuals referred tentatively to b·urlesonensis are associated with Ostrea lisbonensis near the top of the Mount Selman at U.S.G.S. sta. 13622 (L-23), U.S.G.S. sta. 13623 (L-24), and U.S.G.S. sta. 13635 (M-24). Relatively large imperfect examples exhibiting more regular sculpture have been recovered from the glauconitic and calcareous sandstone below the Ostrea lisbonensis zone in Santa Ana, Nuevo León, U.S.G.S. sta. 13626 (L-24).» GARDNER, J. 1945. Mollusca of the Tertiary formations of northeastern Mexico. Geological Society of America Memoirs, 11: 1-332, pls. 1-27. [p. 64, 65]
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Pecten burlesonensis Harris; Renick, B. C. & H. B. Stenzel, 1931, The Lower Claiborne on the Brazos River, Texas, plate 6, figures 1, 2.
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