Fostoria dhimbangunmal, gen. et sp. nov., a new iguanodontian (Dinosauria, Ornithopoda) from the mid-Cretaceous of Lightning Ridge, New South Wales, Australia

Globally, non-hadrosauroid iguanodontians (‘basal iguanodontians’) reached their acme in terms of diversity during the Early Cretaceous. However, Gondwanan representatives of this clade are rare and are represented in Australia only by the enigmatic Muttaburrasaurus langdoni (upper Albian; Mackunda Formation). Here, we describe a new iguanodontian, Fostoria dhimbangunmal, gen. et sp. nov., from the Cenomanian Griman Creek Formation at Lightning Ridge, New South Wales, Australia. The holotype and referred specimens, preserved entirely in opal, pertain to at least four individuals from a monodominant bone bed excavated from an underground opal mine. This deposit constitutes the first ornithopod-dominated bone bed from Australia. Elements from most parts of the body are represented, including the first partial skull of a dinosaur recovered from New South Wales. The new taxon is identified by a number of autapomorphies that include, but are not restricted to, a stepped lateral margin of the frontal in dorsal view and a stout protuberance on the anterolateral corner of the frontal. Phylogenetic analysis based on a recently published data set recovers Fostoria as the sister taxon to a clade of Gondwanan iguanodontians that includes Anabisetia saldiviai, Talenkauen santacrucensis, and Muttaburrasaurus langdoni. The new taxon and M. langdoni represent the sole iguanodontians known from the eastern margin of the epeiric Eromanga Sea, whereas the group is conspicuously absent from the contemporaneous ornithopod-dominated ecosystems of the Australian-Antarctic rift valley in Victoria.

全球范围内，非鸭嘴龙型禽龙类（non-hadrosauroid iguanodontians，即基干禽龙类（basal iguanodontians））的物种多样性在早白垩世达到鼎盛。然而，该演化支的冈瓦纳大陆分布类群十分稀少，在澳大利亚仅以产自阿尔布阶晚期马昆达组（Mackunda Formation）的神秘兰氏穆塔布拉龙（Muttaburrasaurus langdoni）为代表。本文记述了一件产自澳大利亚新南威尔士州闪电岭森诺曼阶格里曼溪组（Griman Creek Formation）的全新禽龙类——新属新种Fostoria dhimbangunmal（gen. et sp. nov.）。其正模标本及归入标本全部保存在蛋白石中，来自一处地下蛋白石矿场发掘的单优势类群骨床，至少代表4个个体。该沉积层是澳大利亚首个以鸟脚类为主导的骨床。标本涵盖身体大部分区域，包括新南威尔士州境内首次发现的恐龙部分头骨。该新类群具有多项自有衍征，包括但不限于：背视下额骨侧缘呈阶梯状，以及额骨前外侧角处的粗壮突起。基于近期发表的数据集开展的系统发育分析显示，Fostoria为一支冈瓦纳禽龙类演化支的姊妹群，该演化支包含萨氏阿尼贝赛特龙（Anabisetia saldiviai）、圣克鲁斯塔伦肯龙（Talenkauen santacrucensis）以及兰氏穆塔布拉龙（Muttaburrasaurus langdoni）。该新类群与兰氏穆塔布拉龙（M. langdoni）是仅有的已知产自陆表埃罗曼加海（epeiric Eromanga Sea）东缘的禽龙类；而该类群在维多利亚州同期以鸟脚类为主导的澳南极裂谷带生态系统中完全缺失。