A recently discovered site in southern Mississippi considered early Arikareean based on identified mammals represents the first of this age from the Gulf Coastal Plain outside of Florida. The Jones Branch Local Fauna was recovered from deltaic/estuarine deposits low in the Catahoula Formation resting unconformably on marl/clay beds of the subjacent, upper Rupelian (lower Oligocene), marine Paynes Hammock Formation. In addition to well-preserved plant material plus reptiles, amphibians, and fishes, the mammals are represented primarily by species previously known almost exclusively from the Great Plains, the northern Rocky Mountains (Montana), and/or John Day region, Oregon, with only a few apparently endemic to the Gulf Coastal Plain. Genera representative of the former include the proscalopid Mesoscalops, the sciurid Hesperopetes, the aplodontiid Downsimus, the putative early castoroid Eutypomys, the castorid Microtheriomys, the eomyids Apeomys and Leptodontomys, the florentiamyid Kirkomys, the mustelids Corumictis and Promartes, the tapir Protapirus, the leptochoerid Leptochoerus, the anthracothere Elomeryx, and the hornless ruminants Hypertragulus and ?Leptomeryx. Mesoscalops, Downsimus, and Apeomys are represented by new species. Additionally, a new genus and species of lagomorph is described, Oligolagus welleri, as is a new genus and new species of eomyid, Paraktioeomys palmeri. Known from both regions is the marsupial Herpetotherium, an apatemyid provisionally referred to Sinclairella, and the borophagine Phlaocyon. Gulf Coastal Plain endemics include the protoceratid Prosynthetoceras orthrionanus and apparently Oligolagus n. gen. and Paraktioeomys n. gen. The geographically broadly distributed horse Miohippus, rhinoceros Diceratherium, and giant entelodont Daeodon are also present. Marine mammals are represented by the dugong Crenatosiren olseni and the odontocete Agorophius pygmaeus. Additionally noted are two taxa from stratigraphically lower formations that are not part of the Jones Branch LF. These include a large species of the entelodont Archaeotherium and the anthracothere Elomeryx armatus, both of which were previously unknown along the Gulf Coastal Plain. The long recognized biotic disparity between the Midcontinent and Gulf Coastal Plain by the early Miocene was not yet strongly apparent during the early to middle Oligocene.UUID: http://zoobank.org/c1b57f31-4ed1-42fb-bf31-c803e2e61cfd

Isolated elasmobranch and teleost teeth, jaws, otoliths, scales, vertebrae, and fin spines were recovered from the upper Oligocene (Chattian) Catahoula Formation in Wayne County, Mississippi, USA. A total of 13 551 specimens were examined and 12 340 of these were identified at least to the ordinal level. These remains represent 49 unequivocal fish taxa, viz. 29 elasmobranchs and 20 teleosts. The 3614 elasmobranch remains indicate that Carcharhiniformes is the most diverse group of Elasmobranchii, with 12 taxa belonging to five families. Orectolobiformes and Lamniformes are represented by far fewer taxa (three and four, respectively). Carcharhinus acuarius (Probst, 1879) constitutes 49% of the total number of shark teeth in our sample. Ten batoids have been identified within Myliobatiformes (seven taxa) and Rhinopristiformes (three taxa). Partial teeth of durophagous myliobatids (three genera) are the most abundant batoid remains, constituting 41% of the total number of ray fossils. However, teeth of Dasyatidae and Rhynchobatus cf. pristinus (Probst, 1877) are abundant and represent 36.5% and 15.4%, respectively, of the specimens identified. Herein, we erect five new elasmobranch taxa, including Galeocerdo platycuspidatum sp. nov., Hemipristis intermedia sp. nov., Hypanus? heterodontus sp. nov., “Sphyrna” gracile sp. nov., and “Sphyrna” robustum sp. nov. The Catahoula Formation sample includes over 9935 teleost fossils, which constitutes 73% of the total fish sample. Nine bony fish taxa are represented solely by teeth, jaw elements, or fin spines. Although otoliths are much less common than the other identifiable remains (409 versus roughly 8430, respectively), they allowed us to identify four taxa not known from other skeletal remains. Albulidae, Sciaenidae, and Sparidae are represented by isolated teeth, jaw elements, and otoliths, but we could not ascertain whether the various teeth and jaw elements are conspecific with the otolith-based species we identified. The remains of Sciaenidae (teeth, jaw elements, otoliths) dominate the Catahoula Formation bony fish assemblage, constituting 70% of the teleost specimens identified at least to the ordinal level. Our sample includes the first Oligocene occurrence of Tetraodontidae in the Western Hemisphere. The vertebrate assemblage within the Catahoula Formation at the study site indicates an estuarine depositional environment, which is consistent with previous interpretations based on lithology. At the study site the Catahoula Formation disconformably overlies the Paynes Hammock Limestone, and we believe the disconformable contact locally represents the Rupelian (early Oligocene)/Chattian (late Oligocene) boundary. The fish fauna described herein is therefore of Chattian age.

Situated throughout the southeastern United States within the Laurentian craton are occurrences of various aged deposits (Late Proterozoic to Early Paleogene) that contain volcanics spanning from lamprophyres to carbonatites and basalts to rhyolites. Several are intrusive, while others have been reworked detritally, deposited as river gravels out onto the Gulf Coastal Plain. The earliest occurrence of igneous gravel clasts in the coastal plain of the lower Mississippi Valley lie along the Mississippi River’s eastern valley wall in the ancestral Mississippi River’s pre-loess terrace deposits (PLTDs). The coarse clastics of the PLTDs are dominantly chert gravels derived from Paleozoic carbonate bedrock, but also include clasts of Precambrian Sioux Quartzite, glacially faceted and striated stones, and ice-rafted boulders, which indicate a direct relationship between the PLTDs and glacial outwash during the cyclic glaciation of the Pleistocene Epoch. The PLTDs also contain the oldest known examples of igneous gravels exposed at the surface in Mississippi. An understanding of their igneous bedrock provenance and the timing of their contribution to the sedimentary record of the lower Mississippi River Valley sheds a valuable light onto the geologic history and evolution of the ancestral Mississippi River during the Pleistocene Epoch. The use of fusion inductively coupled plasma mass-spectroscopy (ICP-MS) in the identification of the igneous suites of one of the pre-loess terraces, well-delineated by geologic mapping, adds important geochemical source data from the gravel constituents for the further interpretation and correlation of the individual PLTD allounits. Gravel constituent geochemistry also offers a better understanding of the evolution of the ancestral Mississippi River watershed and the contributions of bedrock sources during Pleistocene glaciation. This petrological study suggests that the igneous gravels sampled from within the Rawhide PLTD allounit originated from the St. Francois Mountains (SFMs) in southwestern Missouri, with the implications that the SFM igneous terrain was in the direct path of the Independence “Kansan” glaciation. This could indicate a glacial extent further southwest than previously documented.

We describe two small, compressed seeds from the Gulf of Mexico Coastal Plain that display a reticulate-foveolate seed coat pattern as species of Passiflora subgenus Passiflora. One was obtained from the basal layer of the Catahoula Formation in Wayne County, Mississippi, and is late Oligocene in age (25-23.8 Ma), supported by planktonic foraminferal and nannofossil zones. The other is from a Pleistocene river terrace (luminescent dating of 85-82 ka) on the banks of the Mobile River in Alabama. The Oligocene seed is tridentate (consisting of a central apical appendage and well-displayed lateral protrusions to the sides of this appendage), symmetrical, and has a palisade seed coat structure with ruminate endosperm. Its characters allow tentative placement within supersection Laurifolia and series Tiliifolia. Extensive comparisons with seeds of extant species of Passiflora subgenus Passiflora serve as the basis for recognizing it as a new species, Passiflora axsmithii sp. nov. The Pleistocene seed is obovate, slightly asymmetrical, has a small crown around the base of the apical appendage, and insubstantial lateral projections. As the Pleistocene seed is geologically young and fits the description of seeds produced by the native extant species Passiflora incarnata (supersection Passiflora, series Passiflora), we consider it very likely to be a representative of that species. The Oligocene seed is the earliest reliable record, thus far, of genus Passiflora. The Pleistocene seed is likely the earliest record, to date, of the extant species P. incarnata.

Hydrologic reconstructions from North America are largely unknown for the Middle Miocene. Examination of fungal palynomorph assemblages coupled with traditional plant-based palynology permits delineation of local, as opposed to regional, climate signals and provides a baseline for study of ancient fungas. Here, the Fungi in a Warmer World project presents paleoecology and paleoclimatology of 351 fungal morphotypes from 3 sites in the United States: the Clarkia Konservat-Lagerstätte site (Idaho), the Alum Bluff site (Florida), and the Bouie River site (Mississippi). Of these, 83 fungi are identified as extant taxa and 41 are newly reported from the Miocene. Combining new plant-based paleoclimatic reconstructions with funga-based paleoclimate reconstructions, we demonstrate cooling and hydrologic changes from the Miocene climate optimum to the Serravallian. In the southeastern United States, this is comparable to that reconstructed with pollen and paleobotany alone. In the northwestern United States, cooling is greater than indicated by other reconstructions and hydrology shifts seasonally, from no dry season to a dry summer season. Our results demonstrate the utility of fossil fungi as paleoecologic and paleoclimatic proxies and that warmer than modern geological time intervals do not match the “wet gets wetter, dry gets drier” paradigm. Instead, both plants and fungi show an invigorated hydrological cycle across mid-latitude North America.

Our understanding of Miocene floras in eastern North America is hampered by the rarity of megafossil sites. An early report from the middle Miocene Hattiesburg Formation in Mississippi included palms and Ulmus. A later report listed Taxodium, Salix, either Morus or Celtis, and monocot fragments. The floral assemblage described here was recently recovered from along the Bouie River in southern Mississippi. Ferns are represented by complete Salvinia specimens including attached sporocarps, Wood-wardia, and Osmunda. Conifers are represented by branchlets of Taxodium. Angiosperms include leaves attributable to the Lauraceae. Platanus is known from leaves, stipules, and fruits. Leaflets of Sambucus are common. Cercis is recognized from leaves with palmate venation and pulvini. Leaves of Quercus sections Lobatae and Quercus have been recovered. The Juglandaceae include fruits of Juglans and two species of Carya. Morus, Populus, and Salix leaves have been recovered. Of particular biogeographical interest is a seed of Sargentodoxa, which is the first record from the southeastern coastal plain of this current Chinese endemic. Monocots include Cyperus and two types of palm, including one with armed petioles. The first vegetative fossils of Lemna from North America have been identified. Because most of the fossils are related to plants still found in the region today, the climate was probably similar to that of the modern central Gulf Coastal Plain. This flora is now one of the most extensively known in the Neogene of southeastern North America and helps to fill a major gap in our understating of Miocene plant evolution.