DOI: 10.5061/dryad.b5mkkwhh2
title: Data for: Taxonomy and paleobiogeography of rudist bivalves from Upper Cretaceous strata, Gulf Coastal Plain and Puerto Rico, USA

description: This study provides the first focused investigation
 of rudist bivalves from the Upper Cretaceous of the Gulf
 Coastal Plain (GCP) in the southern US and previously undescribed
 specimens from the Flor de Alba Limestone Member of
 the Pozas Formation in Puerto Rico.
 Identified rudists from the GCP comprise
 the Monopleuridae Munier-Chalmas, 1873,
 including Gyropleura Douvillé, 1887, as well
 as Radiolitidae d’Orbigny, 1847,
 including Biradiolites cardenasensis Böse,
 1906, Durania Douvillé,
 1908, Durania maxima (Logan,
 1898), Radiolites Lamarck, 1801, Guanacastea
 jamaicensis (Trechmann,
 1924), Radiolites acutocostata (Adkins, 1930),
 and Sauvagesia Choffat, 1886. Integrating
 rudist occurrences within
 well-established GCP biostratigraphy allows for
 extension of upper ranges of D.
 maxima and R. acutocostata into the
 late Campanian, and lower ranges
 of B. cardenasensis and G. jamaicensis into the early Campanian. Identified rudists from Puerto Rico comprise the Hippuritidae Gray, 1848, and include Barrettia monilifera Woodward, 1862, which supports the age of the Flor de Alba Limestone Member of the Pozas Formation as middle Campanian. Combined taxonomic, biostratigraphic, and paleobiogeographic analyses indicate there is no rudist fauna endemic to the GCP, and the region marks the northeastern range of the Caribbean genera Biradiolites, Durania, Guanacastea, Gyropleura, Radiolites, and Sauvagesia during the Campanian and Maastrichtian. The new occurrences help inform future updates of Late Cretaceous sea surface current reconstructions for the Caribbean and Western Interior Seaway, USA.  
description: Over 200 Upper Cretaceous rudists
 from the GCP were available for study–146 specimens from the Alabama
 Museum of Natural History Paleontology Collections (ALMNH:Paleo:),
 University of Alabama, Tuscaloosa, Alabama, and 63 specimens from the
 Mississippi Museum of Natural Science (MMNS), Mississippi Department of
 Wildlife, Fisheries, and Parks, Jackson, Mississippi. Specimens were
 housed in Alabama and Mississippi, yet they were collected from a broad
 geographic area across the east and west provinces of the GCP, including
 Alabama, Mississippi, Arkansas, and Texas (see Supplemental Data 1 for
 list of specimen identification numbers; information on precise collecting
 localities are available on request from respective museums). Formations
 of the Selma Group, which cover the East GCP, yielded the majority of
 rudist specimens at 200, including 151 specimens from the Mooreville, 17
 from the Demopolis, four from the Ripley, 27 from the Prairie Bluff, and
 one from the Owl Creek (Table 1, left column). Formations of the Taylor
 Group, which span the West GCP and is equivalent in age to the lower part
 of the Selma Group, yielded nine specimens, including four from the Ozan,
 four from the Annona, and one from the Marlbrook (Table 1, center
 column). Many of the GCP
 specimens were donated by avocational collectors or not found exactly
 <em>in situ</em>, though 75% of specimens are well-resolved
 stratigraphically. Regarding ALMNH:Paleo: material, 64% of specimens were
 sourced from the Harrell Station Paleontological Site (HSPS). HSPS has a
 precise stratigraphic placement based on foraminifera, ostracodes, and
 nannoplankton biostratigraphy, as recently reviewed by Ehret and Harrell
 (2018). Located in central Alabama, HSPS possesses over 140 acres of
 exposed chalk gullies and yielded the most rudists of any single site at
 94 specimens. Regarding MMNS material, if not from <em>in
 situ</em>, specimens were stratigraphically traceable to within a
 meter or so of source points. In addition, localities yielding specimens
 contributed by hobbyists were field checked. Puerto Rico material consisted of 50
 samples from the Flor de Alba Limestone Member of the Pozas Formation
 (Table 1). Specimens were collected from one locality near Flor de Alba
 Hacienda, which is southwest of Ciales, Puerto Rico. The rock exposure
 consisted of a limestone layer in a cave ceiling that was near a meter in
 thickness and followed along an adjacent valley. Flor de Alba figured
 specimens, reference fossil, and rock materials, and locality data are
 housed in the Indiana University Paleontology Collections (IUPC),
 Department of Earth and Atmospheric Sciences, Indiana University,
 Bloomington, Indiana, USA. Specimens are assigned IUPC numbers
 101110-101113 for figured specimens and 101114-101160 for reference
 specimens. Specimens were
 photographed and described in terms of taxonomy and taphonomy. Each
 specimen was identified to the lowest taxonomic rank using presence of
 identifiable morphologic characters, including height and width of radial
 bands, presence or absence of a ligamental ridge, shape of shell costae,
 outer layer shell thickness, and shell geometry. When possible, specimens
 were measured to determine the posterior-anterior diameter, dorsal-ventral
 length, costae width, and taxa-specific traits such as beading and rays in
 <em>Barrettia </em>specimens or radial band width in
 Radiolitidae genera (Supplemental Data 2). The preservation type of each
 specimen was documented as original shell material, permineralized, or
 preserved as a mold/cast. The relative completeness of each shell was
 assessed qualitatively and shell sections that were not present were also
 noted. The degree of shell breakage was assessed qualitatively and noted
 in terms such as the most ventral section of the right valve. If epibionts
 were preserved with the shell, the number, shell location, and size were
 described. If a specimen possessed more than one preserved rudist then the
 total number was counted, and the shell orientation was documented.
 Finally, the determined taxonomic designations were placed within the
 lithostratigraphic and biostratigraphic framework provided in the
 literature of the GCP and Caribbean (Figure 2). GCP specimens were not cut
 or sectioned because high-quality rudist specimens from that region are
 rare. Furthermore, these specimens are primarily found as weathered lower
 valves that are not encased in matrix, and the myophores, upper valves,
 and teeth are usually not preserved. Thus, they do not require transverse
 sections to identify the shell shape, whereas many rudist specimens from
 the Caribbean or Central America are encased in dense limestone matrix and
 need to be cut to view shell morphology. Also, given that most GCP
 specimens are missing upper valves, teeth, and myophores, there is far
 less usefulness in cutting transverse sections and permanently damaging
 the specimens. Repositories and institutional
 abbreviations.<strong>—</strong>Figured and
 reference specimens examined in this study are deposited in the following
 institutions: Alabama Museum of Natural History (ALMNH:Paleo:), University
 of Alabama, Tuscaloosa, Alabama, USA; Mississippi Museum of Natural
 Science (MMNS), Mississippi Department of Wildlife, Fisheries, and Parks,
 Jackson, Mississippi, USA; and Indiana University Paleontology Collections
 (IUPC), Department of Earth and Atmospheric Sciences, Indiana University,
 Bloomington, Indiana, USA.
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