Miocene Tayassuidae (Mammalia) from the Chesapeake Group of the Mid-Atlantic coast and their bearing on marine-nonmarine correlation

Abstract

Four morphologically distinct tayassuid species are present in the marine strata of the lower Chesapeake Group in Maryland and Virginia. The oldest of these, an unnamed species, occurs in bed 2 of the Calvert Formation and is the only terrestrial mammal yet known from this unit. In the upper Calvert and lower Choptank Formations three tayassuid species resemble closely in size and morphology taxa known from the middle and upper Miocene Olcott and Valentine Formations in Nebraska. “Cynorca proterva” and “Prosthennops” xiphidonticus are present in beds 10 and 14, respectively, of the Calvert Formation. “Prosthennops” niobrarensis occurs in bed 17 of the Choptank Formation. These taxa, considered together with the other known terrestrial mammals from the Chesapeake Group, indicate the following correlations with land mammal faunas from western North America: bed 2, ?late Arikareean or early Hemingfordian; bed 10, late Hemingfordian or early Barstovian; bed 14, early late Barstovian; bed 17, late late Barstovian. These correlations are largely concordant with micropaleontogical correlations for the Chesapeake Group, but the age indicated for bed 17 is younger than an age estimate based on diatoms.

Evolutionary trends within bivalve prey of chesapeake group naticid gastropods

“…For each genus, between 11 and 15 stratigraphic levels had sample sizes sufficient for quantitative analysis (about 30 specimens in an ontogenetic series were used for each regression; see below). These samples include a time span of about three million years (Kelley, 1983) or perhaps longer (Wright and Eshelman, 1987).…”

The case for dynamic subsidence of the U.S. east coast since the Eocene

“…If a reconstructed paleoshoreline is topographically lower (higher) than global sea level at the same time, then we can infer relative subsidence (uplift) of the region since that time. We reconstruct Miocene and Eocene shorelines using abundant marine (Paleobiology database, available at http://www.paleodb.org; the data were downloaded from the Paleobiology Database in November 2007 using the following parameters: time intervals = Miocene and Eocene, region = United States, paleoenvironment = marine) and less preserved non‐marine sediments [ Tedford and Hunter , 1984; Wright and Eshelman , 1987; Gazin , 1953] along the U.S. Atlantic coast (Figures 2a and 2b). Paleoshorelines for the Eocene (Figure 2a) and Miocene (Figure 2b) are defined as the furthermost inland location of the marine sediments, positioned just oceanward from the non‐marine location, with the exception of the youngest non‐marine sediments in North Carolina (Figure 2b), which we did not take into account since it captures the lowest Miocene sea level.…”

“…(a) Eocene paleoshoreline reconstructions, (b) Miocene paleoshoreline reconstructions, (c) topographic profile through Chesapeake Bay (shown with a straight line on Figures 2a and 2b). Dots and stars on Figures 2a and 2b indicate locations of marine (Paleobiology database, 2007) and non‐marine [ Tedford and Hunter , 1984; Wright and Eshelman , 1987; Gazin , 1953] sediments, respectively, with ages of the non‐marine sediments indicated. Continuous thick lines show position of reconstructed paleoshorelines, and dashed lines indicate paleoshorelines from Bond [1979].…”

New early Barstovian (middle Miocene) vertebrates from the upper Torreya Formation, eastern Florida panhandle

“…The occurrence of "Cynorca" cf. "c." proterva in the WCF supports a correlation with the Barstovian section of the upper Calvert Formation of Maryland (Wright and Eshelman, 1987) and with the Trinity River and Lower Snake Creek faunas (Woodburne, 1969). Only comparisons at a generic level can be made with west coast faunas.…”

“…However as noted by Woodburne (1969), the Ml does not offer any definitive characters to distinguish between members of the genus, prohibiting species allocation of the WCF specimen to "c." proterva. Wright and Eshelman (1987) regard "Cynorca" as a nomen dubium since the type species of the genus ("C. " proterva) was based only on a canine originally described as a squalodont whale .5 (Cook, 1922) Figure 10C, D Referred Specimens-La Camelia Mine: UF 116820, left P3; UF 116825, right Ml or M2 (cast); possibly Corry Mine: UF 100174, right astragalus.…”