A New Furileusaurian Abelisaurid from La Invernada (Upper Cretaceous, Santonian, Bajo De La Carpa Formation), Northern Patagonia, Argentina

Abstract

Abelisaurids are among the most abundant and diverse Patagonian Late Cretaceous theropods. Here, we present a new furileusaurian abelisaurid, Llukalkan aliocranianus gen. et sp. nov., represented by cranial remains from the Bajo de la Carpa Formation (Santonian) at La Invernada fossil area, northwestern Patagonia. Features characterizing this taxon include a possible caudal tympanic recess posterior to the columellar recess, a T-shaped lacrimal with jugal ramus lacking a suborbital process, and large foramina for caudal middle cerebral veins widely separated from the median supraoccipital crest. In addition to this, a bulge on the anteromedial border of the supratemporal fossa, tall and posteriorly projected paroccipital processes, basal tubera interconnected distally, a triangular basisphenoid recess, and a single foramen for the sphenoidal artery on the basisphenoid, differentiate Llukalkan from Viavenator exxoni. The latter is the other furileusaurian taxon from the same area and stratigraphic unit. Although the holotype of Llukalkan probably corresponds to a sub-adult-as the lacrimal morphology suggests-the possibility that it represents a juvenile of V. exxoni is discarded based mainly on the presence of a caudal tympanic recess (which is absent in V. exxoni). The probable coexistence of two abelisaurid taxa demonstrates that the abelisaurids were one of the most important-and likely the main-predator component of the ecosystems, not only in this area, but also in all of Patagonia, during the Late Cretaceous.

New spinosaurids from the Wessex Formation (Early Cretaceous, UK) and the European origins of Spinosauridae

“…Ecological demands require that large predators occur at low taxonomic diversity 66 . Despite this, numerous Jurassic and Cretaceous dinosaur assemblages include two or more comparably sized, morphologically similar, sympatric theropods 67 ; examples are present in various geological formations worldwide (e.g., 21,[68][69][70][71][72][73][74][75] ). The presence of two or more spinosaurid taxa in the same geological unit is therefore not without precedent and may in fact be typical 76 -the above mentioned Early Cretaceous of Iberia appears to testify this diversity.…”

Elemgasem nubilus: a new brachyrostran abelisaurid (Theropoda, Ceratosauria) from the Portezuelo Formation (Upper Cretaceous) of Patagonia, Argentina

“…2017; Delcourt & Iori 2020; Gianechini et al . 2021). This uncertainty also affects the origin of this group such that, depending on the analysis, it is interpreted as originating in the Middle Jurassic or in the Early Cretaceous.…”

“…Ekrixinatosaurus , Ilokelesia , Skorpiovenator ; Pol & Rauhut 2012; Rauhut & Carrano 2016; Delcourt 2017; Gianechini et al . 2021; Ibiricu et al . 2021), whereas, post‐Coniacian brachyrostrans constitute a natural group, Furileusauria (Filippi et al .…”

“…2016; Delcourt 2017; Gianechini et al . 2021). Here, we adopt the latter given the unstable behaviour of Abelisaurus in phylogenetic analyses published during the last 10 years, in which it has been placed in a basal position within Abelisauridae (Canale et al .…”

“…2020; Gianechini et al . 2021) and several indeterminate specimens (e.g. Ezcurra & Méndez 2009; Gianechini et al .…”