Vera Weisbecker

Flinders University · College of Science and Engineering

The ectotympanic, malleus and incus of the developing mammalian middle ear (ME) are initially attached to the dentary via Meckel’s cartilage, betraying their origins from the primary jawjoint of land vertebrates. This recapitulation has prompted mostly unquantified suggestions that several suspected—but similarly unquantified—key evolutionary trans...

This chapter deals with some of the many prejudices surrounding the value of marsupials and monotremes as research organisms. It shows that most published research on mammalian biology actually only deals with placentals, and explains the historical background to the lack of scientific interest in monotremes and marsupials. Montremes are a complex...

Evolutionary increases in mammalian brain size relative to body size are energetically costly but are also thought to confer selective advantages by permitting the evolution of cognitively complex behaviors. However, many suggested associations between brain size and specific behaviors - particularly related to social complexity - are possibly conf...

This chapter provides an evolutionary context to comparative research on monotremes and marsupials. It explains the evolutionary origins of the three mammalian clades in the mammalian (and pre-mammalian) from the ancient lineage of synapsids, summarizes their most obvious biological differences, and briefly the difference between the terms “Monotre...

The profound evolutionary success of mammals has been linked to behavioral and life-history traits, many of which have been tied to brain size. However, studies of the evolution of this key trait have yet to explore the full potential of the fossil record, being limited by the difficulty of obtaining endocranial data from fossils. Using measurement...

The evolution of marsupial postcranial diversity and adaptation has long been conceptually tied to the ability of the otherwise highly immature neonates to actively move to the mother’s pouch after birth. This requirement is reflected in an unusually well-developed forelimb and anterior postcranial skeleton, which gave rise to the long-standing con...

The metatherians (crown-clade marsupial mammals and their fossil relatives) originated in the Late Jurassic or Early Cretaceous of Laurasia, and have since spread worldwide with diversification in South America and Australasia during the Cenozoic. Despite this long evolutionary history, paleoneurology is known for a few taxa from the Americas and A...

Specimen identification is the backbone of archeozoological research. The challenge of differentiating postcranial skeletal elements of closely related wild animals in biodiverse regions can prove a barrier to understanding past human foraging behaviours. Morphometrics are increasingly being employed to classify paleozoological animal remains, howe...

Studies on the evolution of brain size variation usually focus on large clades encompassing broad phylogenetic groups. This risks introducing ‘noise’ in the results, often obscuring effects that might be detected in less inclusive clades. Here, we focus on a sample of endocranial volumes (endocasts) of 18 species of rabbits and hares (Lagomorpha: L...

Due to an abundance of feral predators on the mainland, native rodent species Leporillus conditor (greater stick-nest rats) live almost exclusively on small islands off the coast of South Australia. Many of these islands are heavily degraded novel ecosystems, overrun with African Boxthorn. African boxthorn ( Lycium ferocissimum ) is an aggressive i...

One of the best‐preserved crocodylian fossil specimens from the Cenozoic of Australia is the holotype of the mekosuchine Trilophosuchus rackhami, from the middle Miocene (13.56 ± 0.67 Ma) Ringtail Site at Riversleigh, northwestern Queensland. Although lacking most of the snout, the holotype skull of T. rackhami (QMF16856) has an exceptionally well‐...

Morphology-based taxonomic research frequently applies linear morphometrics (LMM) in skulls to quantify species distinctions. The choice of which measurements to collect generally relies on the expertise of the investigators or a set of standard measurements, but this practice may ignore less obvious or common discriminatory characters. In addition...

Specimen identification is the backbone of archeozoological research. The challenge of differentiating postcranial skeletal elements of closely related wild animals in biodiverse regions can prove a barrier to understanding past human foraging behaviours. Morphometrics are increasingly being employed to classify paleozoological animal remains, howe...

Nocturnal birds display diverse adaptations of the visual system to low-light conditions. The skulls of birds reflect many of these and are used increasingly to infer nocturnality in extinct species. However, it is unclear how reliable such assessments are, particularly in cases of recent evolutionary transitions to nocturnality. Here, we investiga...

The pursuit of simple, yet fair, unbiased, and objective measures of researcher performance has occupied bibliometricians and the research community as a whole for decades. However, despite the diversity of available metrics, most are either complex to calculate or not readily applied in the most common assessment exercises (e.g., grant assessment,...

Taxonomic distinction of species forms the foundation of biodiversity assessments and conservation priorities. However, traditional morphological and/or genetics-based taxonomic assessments frequently miss the opportunity of elaborating on the ecological and functional context of species diversification. Here, we used 3D geometric morphometrics of...

Based on the known fossil record, the majority of crocodylians from the Cenozoic Era of Australia are referred to the extinct clade Mekosuchinae. The only extant crocodylians in Australia are two species of Crocodylus. Hence, the viewpoint that Crocodylus and mekosuchines have been the only crocodylians inhabiting Australia during the Cenozoic has...

Understanding feeding ecology of extinct kangaroos is fundamental to understanding the evolution of kangaroos and the Australia paleoenvironment during the Oligo-Miocene. Comparisons with extant species have suggested that the macropodiforms of the Oligo/Miocene (kangaroos and allies) from the Riversleigh World Heritage Area, northern Australia, we...

Smmary Mammals can amplify their strides through unique up-and-down spinal movements. This ability was long considered to have evolved from lizard-like ancestors with spines moving sideways. A new study now suggests that, instead, it derived from an extinct, previously unknown spinal form.

Relative brain size has long been considered a reflection of cognitive capacities and has played a fundamental role in developing core theories in the life sciences. Yet, the notion that relative brain size validly represents selection on brain size relies on the untested assumptions that brain-body allometry is restrained to a stable scaling relat...

Taxonomic distinction of species forms the foundation of biodiversity assessments and conservation priorities. However, traditional morphological and/or genetics-based taxonomic assessments frequently miss the opportunity of elaborating on the ecological and functional context of species diversification. Here, we used 3D geometric morphometrics of...

Relative brain size has long been considered a reflection of cognitive capacities and has played a fundamental role in developing core theories in the life sciences. Yet, the notion that relative brain size validly represents selection on brain size relies on the untested assumptions that brain-body allometry is restrained to a stable scaling relat...

Considerable controversy exists about which hypotheses and variables best explain mammalian brain size variation. We use a new, high-coverage dataset of marsupial brain and body sizes, and the first phylogenetically imputed full datasets of 16 predictor variables, to model the prevalent hypotheses explaining brain size evolution using phylogenetica...

The causes of Sahul’s megafauna extinctions remain uncertain, although several interacting factors were likely responsible. To examine the relative support for hypotheses regarding plausible ecological mechanisms underlying these extinctions, we constructed the first stochastic, age-structured models for 13 extinct megafauna species from five funct...

Considerable controversy exists about which hypotheses and variables best explain mammalian brain size variation. We use a new, high-coverage dataset of marsupial brain and body sizes, and the first phylogenetically imputed full datasets of 16 predictor variables, to model the prevalent hypotheses explaining brain size evolution using phylogenetica...

Sex determination and differentiation in reptiles is complex. Temperature-dependent sex determination (TSD), genetic sex determination (GSD) and the interaction of both environmental and genetic cues (sex reversal) can drive the development of sexual phenotypes. The jacky dragon ( Amphibolurus muricatus ) is an attractive model species for the stud...

Little is known about how the large brains of mammals are accommodated into the dazzling diversity of their skulls. It has been suggested that brain shape is influenced by relative brain size, that it evolves or develops according to extrinsic or intrinsic mechanical constraints, and that its shape can provide insights into its proportions and func...

Phenotypic convergence, describing the independent evolution of similar characteristics, offers unique insights into how natural selection influences developmental and molecular processes to generate shared adaptations. The extinct marsupial thylacine and placental gray wolf represent one of the most extraordinary cases of convergent evolution in m...

The crocodylian fossil record from the Cenozoic of Australasia is notable for its rich taxonomic diversity, and is primarily represented by members of the clade Mekosuchinae. Reports of crocodylian fossils from Australia date back to the late nineteenth century. In 1886, Charles Walter de Vis proposed the name Pallimnarchus pollens for crocodylian...

Little is known about how the large brains of mammals are accommodated into the dazzling diversity of their skulls. It has been suggested that brain shape is influenced by relative brain size, that it evolves or develops according to extrinsic or intrinsic mechanical constraints, and that its shape can provide insights into its proportions and func...

The pursuit of simple, yet fair, unbiased, and objective measures of researcher performance has occupied bibliometricians and the research community as a whole for decades. However, despite the diversity of available metrics, most are either complex to calculate or not readily applied in the most common assessment exercises (e.g., grant assessment,...

The causes of Sahul’s megafauna extinctions remain uncertain, although multiple, interacting factors were likely responsible. To test hypotheses regarding plausible ecological mechanisms underlying these extinctions, we constructed the first stochastic, age-structured models for 13 extinct megafauna species from five functional/taxonomic groups, as...

Among vertebrates, placental mammals are particularly variable in the covariance between cranial shape and body size (allometry), with rodents being a major exception. Australian murid rodents allow an assessment of the cause of this anomaly because they radiated on an ecologically diverse continent notably lacking other terrestrial placentals. Her...

The biogeographic distribution of diversity among populations of threatened mammalian species is generally investigated using population genetics. However, intraspecific phenotypic diversity is rarely assessed beyond taxonomy‐focused linear measurements or qualitative descriptions. Here, we use a technique widely used in the evolutionary sciences—g...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Analyses of morphological disparity have been used to characterize and investigate the evolution of variation in the anatomy, function and ecology of organisms since the 1980s. While a diversity of methods have been employed, it is unclear whether they provide equivalent insights. Here, we review the most commonly used approaches for characterizing...

Multidimensional analysis of traits are now common in ecology and evolution and are based on trait spaces in which each dimension summarizes the observed trait combination (a morphospace or an ecospace). Observations of interest will typically occupy a subset of this space, and researchers will calculate one or more measures to quantify how organis...

The Night Parrot (Pezoporus occidentalis) is a rare, nocturnal parrot species that has largely escaped scientific investigation due to its behaviour and habitat preferences. Recent field studies have revealed some insights into Night Parrot behaviour, but nothing is known of its sensory abilities. Here, we used μCT scans of an intact Night Parrot s...

Among vertebrates, placental mammals are particularly variable in the covariance between their cranial shapes and body size (allometry), with the notable exception of rodents. Australian murid rodents present an opportunity to assess the cause of this anomaly because they radiated on an ecologically diverse continent unique for lacking other terres...

The hippocampus is well known for its roles in spatial navigation and memory, but it is organized into regions that have different connections and functional specializations. Notably, the region CA2 has a role in social and not spatial cognition, as is the case for the regions CA1 and CA3 that surround it. Here, we investigated the evolution of the...

Background: Within-species skull shape variation of marsupial mammals is widely considered low and strongly size-dependent (allometric), possibly due to developmental constraints arising from the altricial birth of marsupials. However, species whose skulls are impacted by strong muscular stresses - particularly those produced through mastication o...

Although mammalian tail length relative to body length is considered indicative of locomotor mode, this association has been difficult to quantify. This could be because the counterweight function of the tail might associate it more with body weight than body length. Alternatively, relative tail length might not be evolutionarily flexible owing to...

Multidimensional analysis of traits are now a common toolkit in ecology and evolution and are based on trait-spaces in which each dimension summarise the observed trait combination (a morphospace or an ecospace). Observations of interest will typically occupy a subset of this trait-space, and researchers will apply one or more metrics to quantify t...

The hippocampus is well known for its roles in spatial navigation and memory, but it is organized into regions that have different connections and functional specializations. Notably, the region CA2 has a role in social and not spatial cognition, as is the case for the regions CA1 and CA3 that surround it. Here we investigated the evolution of the...

Background Within-species skull shape variation of marsupial mammals is widely considered low and strongly size-dependent (allometric), possibly due to developmental constraints arising from the altricial birth of marsupials. However, species whose skulls are impacted by strong muscular stresses – particularly those produced through mastication of...

Abstract Vertebrate sex differentiation follows a conserved suite of developmental events: the bipotential gonads differentiate and shortly thereafter sex specific traits become dimorphic. However, this may not apply to squamates, a diverse vertebrate lineage comprising of many species with thermosensitive sexual development. Of the three species w...

Background Advances in 3D shape capture technology have made powerful shape analyses, such as geometric morphometrics, more feasible. While the highly accurate micro-computed tomography (µCT) scanners have been the “gold standard,” recent improvements in 3D surface scanners may make this technology a faster, portable, and cost-effective alternative...

Supplementary methods for optimal use of an HD109 3D surface scanner for small biological specimens This standard operating procedures outlines the best practices for 3D scanning, which we chose after extensive trial and error.

Raw landmark coordinates produced by digitizing 3D mesh files in Viewbox This is the raw format of our shape data produced by exporting the landmark coordinates once landmarking in Viewbox was finished.

Sex identification for specimens in intra-specific analyses This table is nearly identical to Table S1 except that the “Catalogue Number” column heading is shortened to “CatNum” to ease the merging datasets. This dataset is necessary to perform the intra-specific analyses presented here.

Table of digitized points with bilateral symmetry for symmetric shape analysis of fixed landmark-only datasets This table only includes the points which are fixed landmarks and have bilateral symmetry (i.e., a symmetric pair with one point on the right side of the skull and the other point in the corresponding symmetric location on the left side of...

Catalogue numbers and sex information for all specimens Catalogue numbers are searchable in the Queensland Museum database, which also provided the sex information for the 19 delicate mouse (Pseudomys delicatulus) specimens we used in our study.

Landmark, semi-landmark curve, and patch point names and definitions There are a total of 289 points used to capture crania shape. 58 are fixed landmarks (LM): the first 12 are centrally located and the remaining 46 come in right and left pairs (right is odd, left is even in the table numbering system). 145 points were placed along 39 curves as sem...

R script for analyses presented in this study This file should be copied into R, Rstudio, or similar. All datasets required to run the analyses are contained in the supplementary information. Some analyses must be run in MorphoJ, an outside software freely available at: http://www.flywings.org.uk/morphoj_page.htm.

Table of digitized points with bilateral symmetry for symmetric shape analysis for datasets of only fixed landmarks and semi-landmark curve points This table only includes the fixed landmarks and semi-landmark curve points which have bilateral symmetry (i.e., a symmetric pair with one point on the right side of the skull and the other point in the...

Table of all digitized points with bilateral symmetry for symmetric shape analysis This table only includes the points which have bilateral symmetry (i.e., a symmetric pair with one point on the right side of the skull and the other point in the corresponding symmetric location on the left side of the skull). The numbers in the “Right” column are l...

Definitions of semilandmarks as required for sliding in geomorph during Procrustes superimposition This table simply encodes the two neighboring points that a semi-landmark can slide between. Point numbers can be related to their position on the cranium using Fig. 3 or Table S2. This table is necessary to treat sliding semi-landmarks correcting dur...

Background. Advances in three-dimensional (3D) shape capture technology have made powerful shape analyses, such as geometric morphometrics, more feasible. While the highly accurate micro-computed tomography (μCT) scanners have been the “gold standard,” recent improvements in 3D surface scanner resolution may make this technology a faster, more port...

Background. Advances in three-dimensional (3D) shape capture technology have made powerful shape analyses, such as geometric morphometrics, more feasible. While the highly accurate micro-computed tomography (μCT) scanners have been the “gold standard,” recent improvements in 3D surface scanner resolution may make this technology a faster, more port...

A new small-bodied ornithopod dinosaur, Diluvicursor pickeringi , gen. et sp. nov., is named from the lower Albian of the Eumeralla Formation in southeastern Australia and helps shed new light on the anatomy and diversity of Gondwanan ornithopods. Comprising an almost complete tail and partial lower right hindlimb, the holotype (NMV P221080) was de...

Sediments of the ETRW Sandstone showing matrix supported conglomerate hosting the partial postcranium NMV P221080. (A) Eroded vertical surface on block ‘B1’ looking north in the region of the anterior caudal vertebrae. (B) Top view of block ‘B1’ in the region of the right pes. (C) Top view of block ‘B5’ in the region of the posterior caudal vertebr...

D. pickeringi in strict consensus trees derived from the matrix of Boyd (2015).

Pedal digit proportions for selected ornithischians (see Figs S6–S7). Notes: the first pedal phalanges (pd I-1) in D. lettowvorbecki and Eousdryosaurus nanohallucis are alternative identifications using the dimensions for the bones identified as first metatarsals (following Galton, 1981; Escaso et al., 2014). Measurements of elements from literatur...

Map of East Gondwana at ∼113 Ma in the region of Australia and Antarctica.

Relative ages of Eumeralla Formation fossil vertebrate localities.

Lower hind limb skeletal features in selected ornithopods. A–B, distal left crus and proximal tarsus of the Muttaburrasaurus langdoni holotype (QM F6140) in anterior view: (A) image; and (B) schematic. (C) Distal left crus and proximal tarsus of D. altus (YPM 1876, cast) in anterior view. D–G, Anabisetia (MCF-PVPH-74): (D) distal left crus and prox...

Comparative dorsoventral proportions of the anterior caudal vertebrae for selected ornithopods (see Fig. 28). Dorsoventral heights: ‘a’ measured vertically from dorsal tip of spinal process to centre of transverse process; ‘b,’ measured vertically from dorsal tip of spinal process to ventral-most margin of centrum; and ‘c,’ measured from dorsal tip...