A new <i>Bothriembryon</i> from the Nullarbor Plain, Western Australia, with insights on the age of <i>Bothriembryon praecursor</i> from Kangaroo Well, Northern Territory

Fossil <i>Bothriembryon</i> specimens were recovered from the northwestern edges of the Nullarbor Plain, Western Australia, ∼300 km inland from the current southern coastline. This locality is significant because extant species of <i>Bothriembryon</i> from the Nullarbor are confined to within 50 km of the coastline. Principle component analysis (PCA) was used to compare the Nullarbor <i>Bothriembryon</i> species with a morphologically comparable extant species from the Eucla Basin, <i>Bothriembryon barretti</i>, and geographically closest fossil species: <i>Bothriembryon kremnobates</i> and <i>Bothriembryon praecursor</i>. Results showed strong support for a new fossil species herein described as <i>Bothriembryon pilkiensis</i> sp. nov. Specimens were found as internal moulds within pisolitic calcrete overlying the early Miocene Colville Sandstone. The chronology of the pisolitic calcrete is poorly studied; here we discuss the results of palynological and U–Th disequilibrium investigations which attempted to constrain the time of deposition and fossilization, with palynology results suggesting the late Pliocene. The type locality of <i>B. praecursor</i>, Kangaroo Well, Northern Territory, was also re-evaluated in age to the early Miocene, using biocorrelation of two balbarid species to taxa found within Riversleigh World Heritage Area assemblages. http://zoobank.org/urn:lsid:zoobank.org:pub:E33B1587-1023-419D-AFE8-11FD8C443A27 <i>Helen E. Ryan [</i>[e-mail]<i>], Collection and Research Centre, WA Museum, 49 Kew Street, Welshpool, WA, 6106; Kenny J. Travouillon [</i>[e-mail]<i>], Collection and Research Centre, WA Museum, 49 Kew Street, Welshpool, WA, 6106; Lynne A. Milne [</i>[e-mail]<i>], School of Earth and Planetary Sciences, Curtin University, Kent Street, Bentley, WA, 6102; Sarah K. Martin [</i>[e-mail]<i>], Geological Survey of Western Australia, Department of Energy, Mines, Industry Regulation and Safety, 100 Plain Street, East Perth, WA, 6004; Kailah M. Thorn [</i>[e-mail]<i>], Collection and Research Centre, WA Museum, 49 Kew Street, Welshpool, WA, 6106; Corey S. Whisson [</i>[e-mail]<i>], Collection and Research Centre, WA Museum, 49 Kew Street, Welshpool, WA, 6106.</i>研究于西澳大利亚州纳拉伯平原（Nullarbor Plain）西北边缘，即距当前南部海岸线内陆约300公里的区域，采获了双脐蜗牛属（*Bothriembryon*）的化石标本。该化石点具有重要科研价值，因为纳拉伯平原现生的双脐蜗牛属（*Bothriembryon*）物种仅分布在距海岸线50公里的范围内。本研究采用主成分分析（PCA），将纳拉伯平原的双脐蜗牛属物种与尤克拉盆地（Eucla Basin）中形态学特征相似的现生物种——巴雷特双脐蜗牛（*Bothriembryon barretti*），以及地理上最邻近的化石物种：克诺姆双脐蜗牛（*Bothriembryon kremnobates*）和前双脐蜗牛（*Bothriembryon praecursor*）进行形态对比。分析结果为一个新的化石物种提供了强有力的支撑，本文将其正式描述为皮尔基双脐蜗牛新种（*Bothriembryon pilkiensis* sp. nov.）。 本次发现的标本以赋存于早中新世科尔维尔砂岩（Colville Sandstone）之上的豆状钙结岩内模形式产出。目前针对该豆状钙结岩的年代学研究尚不完善；本文探讨了通过孢粉学分析与铀-钍不平衡测年法对其沉积及化石形成时间进行限定的研究结果，其中孢粉学分析结果指示其形成时代为上新世晚期。 此前被定为前双脐蜗牛（*B. praecursor*）模式产地的北领地袋鼠井（Kangaroo Well），本次研究通过将两种巴尔巴类（balbarid）物种与里弗斯利世界遗产地（Riversleigh World Heritage Area）的化石类群进行生物地层对比，将其年代重新修订为早中新世。 http://zoobank.org/urn:lsid:zoobank.org:pub:E33B1587-1023-419D-AFE8-11FD8C443A27 海伦·E·赖安 [[e-mail]]，西澳大利亚博物馆收藏与研究中心，澳大利亚西澳大利亚州威尔士普尔丘路49号，邮编6106；肯尼·J·特拉武伊隆 [[e-mail]]，西澳大利亚博物馆收藏与研究中心，澳大利亚西澳大利亚州威尔士普尔丘路49号，邮编6106；琳恩·A·米尔恩 [[e-mail]]，科廷大学地球与行星科学学院，澳大利亚西澳大利亚州本特利肯特街，邮编6102；萨拉·K·马丁 [[e-mail]]，西澳大利亚地质调查局，能源、矿产、工业监管与安全部，澳大利亚西澳大利亚州东珀斯普莱恩街100号，邮编6004；凯拉·M·索恩 [[e-mail]]，西澳大利亚博物馆收藏与研究中心，澳大利亚西澳大利亚州威尔士普尔丘路49号，邮编6106；科里·S·惠森 [[e-mail]]，西澳大利亚博物馆收藏与研究中心，澳大利亚西澳大利亚州威尔士普尔丘路49号，邮编6106。