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，非鸭嘴龙类禽龙类（non-hadrosauroid iguanodontians，基干禽龙类basal iguanodontians）的多样性在早白垩世（Early Cretaceous）达到鼎盛。不过，该演化支（clade）的冈瓦纳（Gondwanan）代表类群极为稀少，在澳大利亚仅以神秘的穆塔布拉龙（Muttaburrasaurus langdoni，阿尔布阶晚期upper Albian；马孔达组Mackunda Formation）为代表。本次研究描述了产自澳大利亚新南威尔士州（New South Wales）闪电岭（Lightning Ridge）森诺曼阶（Cenomanian）格里曼溪组（Griman Creek Formation）的全新禽龙类物种：Fostoria dhimbangunmal，gen. et sp. nov.（新属新种）。其正模标本（holotype）与归入标本（referred specimens）全部以欧泊（opal）形式保存，来自一处从地下欧泊矿中发掘的单优势骨层（monodominant bone bed），至少对应4个个体。该化石点是澳大利亚首个以鸟脚类（ornithopod）为主导的骨层。标本涵盖了身体大部分区域的骨骼元素，包括新南威尔士州境内首次发现的恐龙部分头骨。这一新类群具有多项独有衍征（autapomorphies），包括但不限于：背视（dorsal view）下额骨（frontal）的侧缘呈阶梯状，以及额骨前外侧角处的粗壮突起（stout protuberance）。基于近期公开数据集开展的系统发育分析（phylogenetic analysis）显示，Fostoria为一支冈瓦纳禽龙类演化支的姊妹群（sister taxon），该演化支包含阿纳比塞蒂龙（Anabisetia saldiviai）、塔伦肯龙（Talenkauen santacrucensis）与穆塔布拉龙（Muttaburrasaurus langdoni）。新类群与穆塔布拉龙（M. langdoni）是目前已知仅有的产自埃罗曼加陆表海（epeiric Eromanga Sea）东缘的禽龙类；而该类群在维多利亚州（Victoria）同期以鸟脚类为主导的澳南极裂谷带（Australian-Antarctic rift valley）生态系统中完全缺失。