Anthony L Swinehart

Examination of macrofossils from the late Neogene Pipe Creek Sinkhole in Indiana, USA, yielded 15 distinct plant taxa, one fungal taxon, and six invertebrate taxa. The plant assemblage was dominated by terrestrial taxa both in richness and abundance. Of the 12 terrestrial plant taxa, eight were trees or shrubs including two Carya spp., Corylus sp., Fraxinus sp., aff. Pinaceae, Quercus sp., aff. Rosaceae, and an unknown gymnosperm, possibly Ginkgophyta or Cycadophyta. Fossil nuts of a new species, Carya pipecreekensis Swinehart and Farlow sp. nov., are described. Other terrestrial plant macrofossils include a species of Asteraceae, Vitis sp., Xanthium sp., and Poaceae indet. Charcoalified remains of wood, Asteraceae achenes, and Poaceae crowns suggest fires were an important factor in ecosystem structure. Condition of some of the macrofossils suggests high-energy, post-depositional transport. Aquatic species include the plants Chara sp. and two Potamogeton spp. as well as the animals Helisoma sp., Physa sp., Sphaeriidae, and ostracoda. The terrestrial flora suggests a temperate woodland savanna community with a canopy that includes Carya, Fraxinus, Quercus, Corylus, and Pinaceae, a sub-canopy with Vitis, and a ground flora with a species of Asteraceae and abundant Poaceae. The assemblage shares elements and characteristics with the similarly-aged Gray Fossil Site in Tennessee.

A 1901 report by the Smithsonian Custodian of Paleozoic Plants noted that the nonbiomineralized taxa Buthotrephis divaricata White, 1901, B. newlini White, 1901, and B. lesquereuxi Grote and Pitt, 1876, from the upper Silurian of the Great Lakes area, shared key characteristics in common with the extant green macroalga Codium. A detailed reexamination of these Codium-like taxa and similar forms from the lower Silurian of Ontario, New York, and Michigan, including newly collected material of Thalassocystis striata Taggart and Parker, 1976, aided by scanning electron microscopy and stable carbon isotope analysis, provides new data in support of an algal affinity. Crucially, as with Codium, the originally cylindrical axes of all of these taxa consist of a complex internal array of tubes divided into distinct medullary and cortical regions, the medullary tubes being arranged in a manner similar to those of living Pseudocodium. In view of these findings, the three study taxa originally assigned to Buthotrephis, together with Chondrites verus Ruedemann, 1925, are transferred to the new algal taxon Inocladus new genus, thereby establishing Inocladus lesquereuxi new combination, Inocladus newlini new comb., Inocladus divaricata new comb., and Inocladus verus new comb. Morphological and paleoecological data point to a phylogenetic affinity for Inocladus n. gen. and Thalassocystis within the Codium-bearing green algal order Bryopsidales, but perhaps nested within an extinct lineage. Collectively, this material fits within a large-scale pattern of major macroalgal morphological diversification initiated in concert with the Great Ordovician Biodiversification Event and apparently driven by a marked escalation in grazing pressure. UUID: http://zoobank.org/97c5c737-b291-41a2-aceb-f398cac9537a

A tooth of Phoebodus cf. P. sophiae (Chondrichthyes, Elasmobranchii) was recovered from the Middle Devonian, Early Givetian, Rockport Quarry Limestone Formation in Alpena, Michigan. It is the first known record of the taxon in Michigan and the third known locality from North America. It is the oldest known record in North America, and possibly worldwide, and may extend the known temporal range of the genus. Previous known records for P. sophiae have been confined to the middle Givetian Polygnathus varcus conodont zone, and the taxon was thought to be a possible index fossil for the middle Givetian. The present record extends the taxon to the early Givetian P. hemiansatus conodont zone and, thus, complicates the use of P. sophiae as a proxy index fossil for the P. varcus zone.

The coccoid green algal genus Saturnella Mattauch & Pascher is reported for the first time in North America. Saturnella saturnus (Steincke) Fott was collected from a Sphagnum pool, in Pottawatomie County, Kansas (1976) and in the lagg (wetted shoreline) of a leatherleaf bog in Noble County, Indiana (28 July 1993). The only prior reports of this species that are known are from sites in Europe (Czech Republic, Great Britain, Latvia, Lithuania, Poland, Russia, Sweden, and The Netherlands) and New Zealand.

Fossil wood recovered in gravel at a depth of 129 ft (40 m) from a west-central Indiana water-well drilling was dated at 30,070 ± 240 14C y BP. This date represents a time period in Indiana between ∼23,000–40,000 y BP from which no known previous radiocarbon dates have been recorded. Fragments of wood were determined to be mostly Picea, and at least one fragment is referable to Larix. The macrofossils indicate the presence of boreal conditions in west-central Indiana at the beginning of the Plum Point Interstadial. Analysis of the gravel associated with the wood macrofossils suggests that the organic material was incorporated into the ice of the Lake Michigan lobe of the Laurentide Ice Sheet late in the Altonian Substage of the Late-Wisconsinan between 21,000 y BP and 26,000 y BP.

Discovery of the jaw of an American mastodont (Mammut americanum) and an unusual sedimentary profile in a cornfield in Warren County, Indiana, prompted a multidisciplinary study of the palaeoenvironment of the site. Wood taken from near the base of the deposit was dated at 15,540 ybp. Stratigraphic and textural analyses of the 2.3 m sedimentary profile reveal a series of inundation and desiccation events marked by polygonal fissures. Analysis of pollen from the sediment profile indicates that a boreal flora predominated during much of the time period represented by the profile. Pollen correlation indicates that the sedimentary record was truncated by unconformities around 10,000 ybp. Macrofossil analysis indicates a local environment that began as a forest dominated by white spruce and tamarack. Later inundation of the forest was indicated by the appearance of fish (Perca flavescens), meadow voles (Microtus pennsylvanicus), and submergent aquatic macrophytes (Myriopyllum exalbescens), Potamogeton pusillus, Ceratophyllum demersum, and Najas flexilis). The aquatic environment was interrupted by periods of exposure and desiccation as indicated by the disappearance of identifiable macrofossils and by the stratigraphy. The Shafer fossil assemblage is compared with other localities, and the taphonomy and palaeoenvironment of the mastodont are discussed.