Geology Reports⌕ Search
Home/Archive/USGS

USGS · 70018550

Bivalves and gastropods from the middle Campanian Anacacho limestone, South Central Texas

W.P. Elder
View original source ↗Export metadata ↓

Abstract

The Anacacho Limestone was deposited during the Campanian and represents two depositional intervals, one of early Campanian and one of middle Campanian age. These two intervals correspond to periods of major eustatic sea level rise. This study focuses on the molluscan paleontology of the middle Campanian interval in the eastern part of the Anacacho exposure belt in Medina County, Texas. Molluscan assemblages in this area are indicative of inner to mid-shelf environments. No significant reef components are present. These eastern Anacacho deposits are interpreted to represent more offshore, deeper water environments than those to the southwest, where reef and lagoonal deposits have been reported.

Explore related subjects

Journal of PaleontologyArticle

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

W.P. Elder. 2016-05-20. Bivalves and gastropods from the middle Campanian Anacacho limestone, South Central Texas. https://doi.org/10.1017/s0022336000023337

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2017

Evolution, biogeography, and systematics of Puriana: evolution and speciation in Ostracoda, III.

Three types of geographic isolation—land barriers, deep water barriers, and climatic barriers—resulted in three distinct evolutionary responses in Neogene and Quaternary species of the epineritic ostracode genus Puriana . Through systematic, paleobiogeographic, and morphologic study of several hundred fossil and Recent populations from the eastern Pacific, western Atlantic, Gulf of Mexico, and the Caribbean, the phylogeny of the genus and the geography of speciation events were determined. Isolation of large populations by the Isthmus of Panama during the Pliocene did not lead to lineage splitting in species known to have existed before the Isthmus formed. Conversely, the establishment of small isolated populations on Caribbean islands by passive dispersal mechanisms frequently led to the evolution of new species or subspecies. Climatic changes along the southeastern United States during the Pliocene also catalyzed possible parapatric speciation as populations that immigrated to the northeastern periphery of the genus' range split to form new species. The results provide evidence that evolutionary models describing the influence of abiotic events on patterns of evolution and speciation can be tested using properly selected tectonic and climatic events and fossil groups amenable to species-level analysis. Two new species, P. bajaensis and P. paikensis , are described.

Journal of Paleontology↗
USGS2017

Maastrichtian ammonites chiefly from the Prairie Bluff Chalk in Alabama and Mississippi

The Prairie Bluff Chalk of Alabama and Mississippi yields a diverse ammonite fauna of Maastrichtian age. Twenty-eight species, of which three are new, are recorded herein: Pseudophyllites indra (Forbes, 1846), Hauericeras rembda (Forbes, 1846), Pachydiscus ( Pachydiscus ) maconensis n. sp., P. ( P. ) cf. gollevillensis (d'Orbigny, 1850), P. ( P. ) jacquoti (Seunes, 1890), P. ( P. ) egertoni (Forbes, 1846), Sphenodiscus lobatus (Tuomey, 1854), S. pleurisepta (Conrad, 1857), Coahuilites sheltoni Böse, 1928, Nostoceras ( Nostoceras ) alternatum (Tuomey, 1854), N. ( N. ) mendryki Cobban, 1974a, N. ( N. ) magdadiae Lefeld and Uberna, 1991, N. ( N. ) irregulare n. sp., Glyptoxoceras torquatum (Morton, 1834), Glyptoxoceras sp. A, Glyptoxoceras ? sp., Baculites lomaensis Anderson, 1958, Baculites spp. A–C, Eubaculites labyrinthicus (Morton, 1834), E. carinatus (Morton, 1834), Baculites ? trabeatus (Morton, 1834), Trachybaculites columna (Morton, 1834), Discoscaphites conradi (Morton, 1834), D. gulosus (Morton, 1834), Jeletzkytes criptonodosus Riccardi, 1983, Trachyscaphites alabamensis n. sp., and T. yorkensis (Stephenson, 1941). One genus, Trachybaculites , is new. The bulk of the fauna can be referred to a Discoscaphites conradi assemblage zone, but some elements in the fauna are significantly older.

Journal of Paleontology↗
USGS2017

Ascaulocardium armatum (Morton 1833), new genus (Late Cretaceous): the ultimate variation on the bivalve paradigm

Cretaceous clavagellid pelecypods are a poorly known group, and have previously received little study. Ascaulocardium armatum is conchologically the most complex burrowing pelecypod known. From the study of living clavagellids, it is possible to interpret the various tubes extending outward from the adventitious crypt of A. armatum as devices for hydraulic burrowing and deposit feeding. The conchologically complex A. armatum occurs near the beginning of the history of the Clavagellidae, and does not seem to have given rise to any younger species. Ascaulocardium armatum is known only from the Upper Cretaceous rocks (Santonian–Maastrichtian) of the east Gulf and Atlantic Coastal Plains of the United States of America, as is probably the genus Ascaulocardium . All known Cretaceous clavagellids are burrowing species having a free right valve, and this is the ancestral mode of life of the Clavagellidae. Clavagellids that have a boring habit are a more recent evolutionary development, as are burrowing species having both juvenile valves cemented to the crypt. Clavagellids probably evolved from Jurassic–Early Cretaceous pholadomyids. Almost all Cretaceous clavagellids occur outside the Tethyan Zoogeographic Realm; this distribution is in marked contrast to the modern distribution of the family. Living species mostly inhabit clear, shallow seas in subtropical to tropical shelf areas.

Journal of Paleontology↗