Palaeoecological inferences for the fossil Australian snakesYurlunggurandWonambi(Serpentes, Madtsoiidae)

Abstract

Madtsoiids are among the most basal snakes, with a fossil record dating back to the Upper Cretaceous (Cenomanian). Most representatives went extinct by the end of the Eocene, but some survived in Australia until the Late Cenozoic. Yurlunggur and Wonambi are two of these late forms, and also the best-known madtsoiids to date. A better understanding of the anatomy and palaeoecology of these taxa may shed light on the evolution and extinction of this poorly known group of snakes and on early snake evolution in general. A digital endocast of the inner ear of Yurlunggur was compared to those of 81 species of snakes and lizards with known ecological preferences using three-dimensional geometric morphometrics. The inner ear of Yurlunggur most closely resembles both that of certain semiaquatic snakes and that of some semifossorial snakes. Other cranial and postcranial features of this snake support the semifossorial interpretation. While the digital endocast of the inner ear of Wonambi is too incomplete to be included in a geometric morphometrics study, its preserved morphology is very different from that of Yurlunggur and suggests a more generalist ecology. Osteology, palaeoclimatic data and the palaeobiogeographic distribution of these two snakes are all consistent with these inferred ecological differences.

The internal cranial anatomy of Champsosaurus (Choristodera: Champsosauridae): Implications for neurosensory function

“…ecology and the endosseous labyrinth. It has repeatedly been suggested that canal morphology is closely associated with ecology [9][10][11]14,15 , but as discussed above, the morphology of the canals also carries a strong phylogenetic signal 13 . Shape analyses have repeatedly been conducted on reptiles, but have focused on relatively closely related groups, such as snakes 12 or squamates as a whole 9 .…”

Cranial osteology of Hypoptophis (Aparallactinae: Atractaspididae: Caenophidia), with a discussion on the evolution of its fossorial adaptations

“…The ascending process of Aparallactus , Hypoptophis , Macrelaps and to some extent, Amblyodipsas is similar to that of uropeltids. Interestingly, all these extant taxa are fossorial, while among the extinct ones, at least Dinilysia , Coniophis , and Yurlunggur (a madtsoiid) had some traits indicating a semifossorial lifestyle (Longrich et al, 2012 ; Palci et al, 2017 , 2018 ). The same might (or might not) apply to Najash as well (Apesteguía & Zaher, 2006 ).…”

“…As a step toward bridging the knowledge gap in aparallactine osteology, cranial elements of Hypoptophis wilsonii are described using micro‐computed tomographic (μCT) scans of three specimens. The endocast of the inner ear was also prepared and described, as this region has proved to be of particular importance in drawing paleoecological inference (Palci et al, 2017 ; Palci et al, 2018 ; Yi & Norell, 2015 ). We discuss the fossorial adaptation in the cranium of Hypoptophis against the broader backdrop of fossorial traits in atractaspidids and Serpentes in general.…”

Endocranial anatomy of plesiosaurians (Reptilia, Plesiosauria) from the Late Cretaceous (Turonian) of Goulmima (southern Morocco)

“…However, Callawayasaurus exhibits a taller endosseous labyrinth than both Libonectes specimens (Neenan et al, 2017) resulting in a dorsal extension of both the posterior and anterior semicircular canals and a longer crus communis. Such variability could rely on a phylogenetic signal (e.g., Palci et al, 2017) but also be linked to ecological factors (e.g., Palci et al, 2018). According to Neenan et al (2017), the labyrinth in sauropterygians is closely linked with both locomotor style and body proportions.…”