Doswell Formation
Genus Species Sub-unit Basin Abundance Notes
Macrotaniopteris M. crassinervis , M. magnifolia Stagg Creek member , Vinita member Richmond , Taylorsville common A cycad
Plicarizamites P. lanceolatus Vinita member ( Winterpock assemblage ) Richmond
Podozamites P. lanceolatus , P. tenuistriatus Stagg Creek member , Vinita member Richmond , Taylorsville A type of leaf referable to conifers
Primaraucaria P. wielandii Vinita member Richmond fairly common An araucariacean conifer
Pterophyllum P. affinae , P. braunianum , P. inaequale , P. giganteum , P. grandifolium , P. taxinum , P. tenuinervis Stagg Creek member , Vinita member Richmond , Taylorsville Very common A cycadeoid bennetitalean
Sagenopteris S. rhoifolia Vinita member ( Winterpock assemblage ) Richmond A seed fern
Sphenobaiera S. striata Stagg Creek member , Vinita member Richmond , Taylorsville common A ginkgophyte
Sphenopteris S. sitholeyi Stagg Creek member , Vinita member Richmond , Taylorsville common A seed fern
Sphenozamites S. rogersianus Stagg Creek member , Vinita member Richmond , Taylorsville common A cycad
Stangerites S. obliqua , S. planus Vinita member ( Winterpock assemblage ) Richmond A cycad
Taeniopteris T. diminuta Vinita member ( Winterpock assemblage ) Richmond common Leaves of a Pentoxylon -like plant
Triassiflorites T. grandiflora Vinita member ( Winterpock assemblage ) Richmond A cone , possibly from a bennetitalean
Zamiostrobus Z. lissocardius Vinita member ( Winterpock assemblage ) Richmond A cone from a cycad or conifer
Zamites Z. powellii Stagg Creek member Taylorsville A cycadeoid bennetitalean
Paleobiota -- Gymnosperms
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The Doswell Formation (also known as the Doswell Group) is a geologic unit of Upper Triassic age, part of the Newark Supergroup. The Doswell Formation was originally named to refer to a geological sequence which forms the lower part of the sedimentary fill of the Taylorsville Basin in Virginia and Maryland. This sequence was deposited by lakes and rivers in the developing rift basin. However, a 2016 study determined that several geological layers in Pennsylvania as well as the neighboring Richmond Basin of Virginia also qualified as components of the Doswell Formation. The most diverse and fossiliferous component of the Doswell formation is the Vinita member, also sometimes referred to as the Turkey Branch, Tuckahoe, or Falling Creek Formations in earlier publications. The Doswell formation is biostratigraphically characterized by a fauna including the fish Dictyopyge macrurus and the conchostracan Laxitextella multireticulata. The Richmond Basin has several notable fossil sites, such as the Tomahawk site which has hundreds of fossils from the cynodont Boreogomphodon, and the Winterpock site which has an extraordinarily diverse assortment of plants. The Taylorsville Basin is much more restricted in terms of fossil locales, but it was home to the unusual armored reptile Doswellia. The Doswell Formation is among the oldest Triassic formations on the east coast of the United States. It is believed to belong to the early Carnian (Cordevolian) age of the Triassic based on its fauna and flora, which is distinctly dominated by tetrapods similar to gondwanan groups, as well as a high diversity of humidity-loving plants such as ferns and cycads. This gives it a distinct disconnect from the younger formations of the Newark Supergroup, which typically have a fauna similar to the Triassic formations of the western United States and a flora including elements such as conifer trees, which are better adapted for drier conditions.