Taphonomic studies of the fossil insects of the Middle Eocene Kishenehn Formation

Abstract

The lacustrine oil shales of the Coal Creek Member of the Kishenehn Formation in northwestern Montana comprise a relatively unstudied middle

The first fossil New World Dixidae with a critical discussion of generic definitions

“…For instance, Dixa fluvica prefers slow flowing watercresschoked springs (almost ditches) and Dixella cornuta and Dixa pseudindiana occur in streams and rivers, respectively (Moulton, personal obs.). Although the four new fossil species of Dixella were collected at three different sites, all of the sites had shallow near-shore depositional environments (Greenwalt et al, 2015).…”

“…However, given 1) our desire to distinguish these four species from all fossil dixids described previously and 2) the observation that designations such as "Genus incertae sedis" or "Genus indeterminate" are often not recorded in commonly used databases, a generic designation has been provided. The four new species described herein are assigned to the genus Dixella, not necessarily based on morphological criteria, but rather on the near-shore lacustrine environment in which they lived and were deposited (Greenwalt et al, 2015;see Discussion). This of course presumes that genus-specific ecological niches (fast-flowing waters in the mid-stream of waterways or water falls [Dixa] vs. still waters of near-shore lake or pond environments [Dixella] [Nowell, 1951]) had already been established 46 Ma.…”

“…The environment that existed when the Kishenehn sediments were deposited was seasonal subtropical/tropical. Sediments formed in a shallow near-shore environment that exhibited little or no water flow (Greenwalt et al, 2015). 40 Ar/ 39 Ar analysis and 43.5 ± 4.9 Ma by fission-track analysis (Constenius, 1996).…”

Fossil Ants (Hymenoptera: Formicidae) of the Middle Eocene Kishenehn Formation

“…The Coal Creek Member (estimated to be ca. 46 million years old) of the Kishenehn Formation located in northwestern Montana (Fig 1) has recently been the focus of several paleoentomological studies (Huber & Greenwalt, 2011;Greenwalt et al, 2015;Greenwalt et al 2013;Shockley & Greenwalt, 2013;Greenwalt & Rust, 2014) based on a large and growing collection of fossils at the National Museum of Natural History (Washington, DC). The paleoclimate of the Kishenehn Basin 46 million years ago was tropical, with a mean annual temperature as much as 15°C higher than the region's current temperatures (Wolfe, 1995;Zachos et al, 2001;Huber & Caballero, 2011), and characterized by low temperature seasonality, similar to extant tropical forests RESEARCH ARTICLE -ANTS 1 -Towson University, Towson, Maryland, USA 2 -National Museum of Natural History, Smithsonian Institution, Washington, D.C., USA (Archibald et al, 2010(Archibald et al, , 2013.…”

Findings of Daphnia (Ctenodaphnia) Dybowski et Grochowski (Branchiopoda: Cladocera) in Cenozoic volcanogenic lakes in Germany, with discussion of their indicator value

“…They originated in the Palaeozoic (Frey, 1987;Sacherová and Hebert, 2003;Kotov, 2013), but the authors of all papers with descriptions of Palaeozoic cladoceran-like fossils (Smirnov, 1970;Anderson et al, 2004;Womack et al, 2012) did not represent really strong evidences of their belonging to the cladocerans (Kotov, 2013). Only a few papers were published on Palaeogene and Miocene cladocerans (Frey, 1964;Yixin, 1995;Peñalver et al, 1996;Greenwalt et al, 2014;Wappler et al, 2014), in contrast to very numerous publications concerning their remains from Neogene, specially Holocene (Frey, 1964;Rautio, 2007;Nevalainen et al, 2011). At least for some Cenozoic Central European Maar lakes like Messel (Lutz, 1991;Richter and Wedmann, 2005) and Randeck (Heizmann and Schweigert, 1988) or the lacustrine sediments from Rott (von Heyden, 1862;Rolfe, 1963) ephippia of Daphnia were reported, but no adequate descriptions of the fossils were made, nor accurate determinations were provided, and no conclusions on their stratigraphic significance were made.…”