Plant and invertebrate macrofossils from the Pipe Creek Sinkhole (Late Neogene), Grant County, Indiana

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 <i>Carya</i> spp., <i>Corylus</i> sp., <i>Fraxinus</i> sp., aff. Pinaceae, <i>Quercus</i> sp., aff. Rosaceae, and an unknown gymnosperm, possibly Ginkgophyta or Cycadophyta. Fossil nuts of a new species, <i>Carya pipecreekensis</i> Swinehart and Farlow sp. nov., are described. Other terrestrial plant macrofossils include a species of Asteraceae, <i>Vitis</i> sp., <i>Xanthium</i> 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 <i>Chara</i> sp. and two <i>Potamogeton</i> spp. as well as the animals <i>Helisoma</i> sp., <i>Physa</i> sp., Sphaeriidae, and ostracoda. The terrestrial flora suggests a temperate woodland savanna community with a canopy that includes <i>Carya, Fraxinus, Quercus, Corylus</i>, and Pinaceae, a sub-canopy with <i>Vitis</i>, 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.

对美国印第安纳州晚新近纪（late Neogene）派普克里克落水洞（Pipe Creek Sinkhole）中的大化石（macrofossils）开展研究，共获得15个不同的植物分类单元、1个真菌分类单元以及6个无脊椎动物分类单元。该植物组合在物种丰富度与个体丰度上均以陆生类群为主导。在12个陆生植物分类单元中，8个为乔木或灌木，包括2个山核桃属（Carya）物种、1个榛属（Corylus）物种、1个梣属（Fraxinus）物种、松科近缘类群（aff. Pinaceae）、1个栎属（Quercus）物种、蔷薇科近缘类群（aff. Rosaceae），以及1个未知裸子植物，推测其隶属于银杏植物门（Ginkgophyta）或苏铁植物门（Cycadophyta）。本文记述了一个新种——派普克里克山核桃（Carya pipecreekensis）Swinehart & Farlow sp. nov.的化石坚果。其余陆生植物大化石包括1个菊科（Asteraceae）物种、葡萄属（Vitis）未定种、苍耳属（Xanthium）未定种，以及未鉴定的禾本科（Poaceae）植物（Poaceae indet.）。木炭化的木材残体、菊科瘦果与禾本科茎基残体表明，火灾曾是调控该生态系统结构的关键因素。部分大化石的保存状态显示其经历了高能沉积后搬运过程。水生类群包括轮藻属（Chara）未定种、2个眼子菜属（Potamogeton）物种，以及动物类群：扁卷螺属（Helisoma）未定种、膀胱螺属（Physa）未定种、球蚬科（Sphaeriidae）生物与介形类（Ostracoda）。该陆生植物群指示出温带稀树草原林群落：上层乔木层包含山核桃属、梣属、栎属、榛属与松科植物，下层亚乔木层包含葡萄属植物，地表层则包含1个菊科物种与大量禾本科植物。该化石组合与美国田纳西州年代相近的格雷化石点（Gray Fossil Site）共享诸多类群与特征。