Benjamin P. Kear

Current status of species-level representation in faunas from selected fossil localities in the Riversleigh World Heritage Area, northwestern Queensland

Current lists of species-level representation in faunas from 80 Cenozoic fossil localities at the Riversleigh World Heritage Area have been compiled by review of recorded occurrences of taxa obtained from both published and unpublished sources. More than 290 species-level taxa are represented, comprising mammals, amphibians, reptiles, birds, fishes, molluscs and crustaceans. The data are presented for the purpose of ongoing palaeoecological and biochronological studies.

A primitive protostegid from Australia and early sea turtle evolution.

Sea turtles (Chelonioidea) are a prominent group of modern marine reptiles whose early history is poorly understood. Analysis of exceptionally well preserved fossils of Bouliachelys suteri gen. et sp. nov., a large-bodied basal protostegid (primitive chelonioid) from the Early Cretaceous (Albian) of Australia, indicates that early sea turtles were both larger and more diverse than previously thought. The analysis implies at least five distinct sea turtle lineages existed around 100 million years ago. Currently, the postcranially primitive Ctenochelys and Toxochelys are interpreted as crown-group sea turtles closely related to living cheloniids (e.g. Chelonia); in contrast, the new phylogeny suggests that they are transitional (intermediate stem-taxa) between continental testudines and derived, pelagic chelonioids.

A NEW ELASMOSAURID PLESIOSAUR FROM THE LOWER CRETACEOUS OF QUEENSLAND, AUSTRALIA

Abstract A nearly complete but badly crushed elasmosaurid plesiosaur skull is described from the Upper Albian Toolebuc Formation of northern Queensland, Australia. The specimen has a long history, being previously referred to the Australian Aptian genus ‘Woolungasaurus’ (considered a nomen dubium), as well as provisionally to Elasmosauridae gen. et sp. nov., and most recently to Tuarangisaurus (Campanian-Maastrichtian, New Zealand and potentially Patagonia). The present assessment alternatively proposes assignment to a new taxon, Eromangasaurus carinognathus, gen. et sp. nov., uniquely characterized by the presence of seven premaxillary teeth (three lateral pairs, one midline), an elongate mandibular symphysis with prominent ventral midline keel, and a combination of osteological features variably developed in other elasmosaurids. Cladistic analysis using 43 discrete cranio-dental and vertebral characters coded for 16 ingroup and one outgroup taxon supports this conclusion, indicating that E. carinognathus is a crown-group elasmosaurid of more derived grade than Occitanosaurus (Lower Jurassic, Toarcian, France). Affinities with other Cretaceous elasmosaurids are poorly resolved. Nevertheless, a close relationship with Tuarangisaurus is not substantiated; instead, E. carinognathus forms a discrete clade with Terminonatator (Campanian, Canada).

Unusual gut contents in a Cretaceous ichthyosaur.

Despite ichthyosaurs being one of the most extensively studied Mesozoic marine reptile groups, there is little documented direct evidence of dietary habits in most taxa. Here, we report the discovery of hatchling-sized marine protostegid turtle remains and an enantiornithine bird (in association with actinopterygian fish and phosphatic nodules) within the body cavity of a gravid female ichthyosaur (Platypterygius longmani) from the Lower Cretaceous of Australia; this is the first evidence, to our knowledge, of feeding by ichthyosaurs upon both turtles and birds. The exceptionally preserved gut contents show little evidence of digestion, suggesting consumption shortly before the ichthyosaurs death. Poor swimming ability may have made hatchling turtles easy prey that could have been either swallowed whole or processed by shake feeding. Ingestion of bird remains probably occurred through scavenging. Opportunistic feeding on vertebrates is at odds with existing interpretations of dietary habits in Cretaceous ichthyosaurs, which favour predation primarily upon cephalopods. Such specialization is considered a contributing factor in the groups ultimate extinction. However, the evidence here that at least some forms were able to use a wide range of available food types suggests that the decline of ichthyosaurs in the mid-Cretaceous may be linked to other factors such as competition with ecologically analogous pursuit predators.

An archaic crested plesiosaur in opal from the Lower Cretaceous high-latitude deposits of Australia

Umoonasaurus demoscyllus gen. et sp. nov. is a new small-bodied (approx. 2.5 m) pliosauroid plesiosaur from the Lower Cretaceous (Aptian–Albian) of southern Australia. It is represented by several partial skeletons (one with a near complete skull is the most complete opalized vertebrate fossil yet known), and is unique in having large crests on the skull midline and above the orbits. Umoonasaurus is surprisingly archaic despite its relatively late age (approx. 115 Myr ago)—being simultaneously the most basal (primitive) and last surviving rhomaleosaurid. Notably, it lacks the ‘pliosauromorph’ features (large head, short neck, gigantism) typically characterizing many more derived Jurassic rhomaleosaurids; thus, reinforcing the suspected convergent evolution of the ‘pliosauromorph’ hypercarnivore body plan. Umoonasaurus inhabited an Early Cretaceous high-latitude (approx. 70° S) inland seaway subject to seasonally near-freezing climatic conditions. This extreme environment supported a diverse range of plesiosaur taxa, suggesting that these marine reptiles might have possessed adaptations (e.g. heightened metabolic levels) to cope with cold-water temperatures. Indeed, survival of ancient endemic lineages such as Umoonasaurus is a common phenomenon in Australian Cretaceous vertebrate assemblages and might have been facilitated by isolation in low-temperature high-latitude regions.

First Dinosaurs from Saudi Arabia

Dinosaur remains from the Arabian subcontinent are exceedingly rare, and those that have been documented manifest indeterminate affinities. Consequently the discovery of a small, but diagnostic, accumulation of elements from Campanian-Maastrichtian (∼75 Ma) deposits in northwestern Saudi Arabia is significant because it constitutes the first taxonomically identifiable dinosaur material described from the Arabian Peninsula. The fossils include a series of possible lithostrotian titanosaur caudal vertebrae, and some isolated theropod marginal teeth that share unique character states and metric parameters (analyzed using multivariate statistical methods) with derived abelisaurids – this is the first justifiable example of a non-avian carnivorous dinosaur clade from Arabia. The recognition of titanosaurians and abelisaurids from Saudi Arabia extends the palaeogeographical range of these groups along the entire northern Gondwanan margin during the latest Cretaceous. Moreover, given the extreme paucity of coeval occurrences elsewhere, the Saudi Arabian fossils provide a tantalizing glimpse into dinosaurian assemblage diversity within the region.

The Australian Cretaceous ichthyosaur Platypterygius australis: a description and review of postcranial remains

ABSTRACT Australian Cretaceous ichthyosaur material is amongst the most complete in the world. This study describes postcranial remains referred to the upper Albian species Platypterygius australis, including the first record of pelvic and hind limb elements for this taxon. A combination of phylogenetically significant traits such as lack of fusion between the atlas-axis complex and third cervical centrum, the presence of three distal facets on both the humerus/femur for accommodation of the anterior zeugopodial elements plus the radius/tibia and ulna/fibula, concave preaxial accessory facet surfaces on both the humerus and the femur, and complete fusion of the ischiopubis with closure of the obturator foramen, are considered diagnostic for the species and (in conjunction with other previously identified cranial/postcranial features) may serve to distinguish P. australis from the other paleogeographically disparate Platypterygius spp.

Phylogenetic relationships of living and recently extinct bandicoots based on nuclear and mitochondrial DNA sequences

Bandicoots (Peramelemorphia) are a major order of australidelphian marsupials, which despite a fossil record spanning at least the past 25 million years and a pandemic Australasian range, remain poorly understood in terms of their evolutionary relationships. Many living peramelemorphians are critically endangered, making this group an important focus for biological and conservation research. To establish a phylogenetic framework for the group, we compiled a concatenated alignment of nuclear and mitochondrial DNA sequences, comprising representatives of most living and recently extinct species. Our analysis confirmed the currently recognised deep split between Macrotis (Thylacomyidae), Chaeropus (Chaeropodidae) and all other living bandicoots (Peramelidae). The mainly New Guinean rainforest peramelids were returned as the sister clade of Australian dry-country species. The wholly New Guinean Peroryctinae was sister to Echymiperinae. The poorly known and perhaps recently extinct Seram Bandicoot (Rhynchomeles) is sister to Echymipera. Estimates of divergence times from relaxed-clock Bayesian methods suggest that living bandicoots originated in the late Oligocene or early Miocene, much earlier than currently thought based on fossils. Subsequent radiations within Peramelemorphia probably took place on the Australian mainland during the Miocene, with diversification of rainforest taxa on the newly emergent New Guinean landmasses through the middle-late Miocene and complete establishment of modern lineages by the early Pliocene.

Postcranial anatomy of Platypterygius americanus (Reptilia: Ichthyosauria) from the Cretaceous of Wyoming

ABSTRACT Ichthyosaurs remains from the Albian and Cenomanian of Wyoming have been assigned to Platypterygius americanus, but apart from structures of the distal humerus, few other unequivocal character states have been proposed to differentiate this species from its congeners. The purpose of this study was to reevaluate the postcranial morphology of Platypterygius americanus, in order to assess the validity of this species and distinguish postcranial traits relevant for specific diagnoses. Several applicable features were identified, including the location of extrazeugopodial facets on the distal humerus and femur, shape of the intermedium, relative degree of fusion within the atlas-axis complex, number of presacral centra, and varying lengths of the anterior caudal centra. Comparative assessment suggests that Platypterygius americanus is a valid taxon, and that it is possible to differentiate the various Platypterygius spp. independent of stratigraphical and/or geographical occurrence data. Nevertheless, a future review of cranial morphology in all Platypterygius spp. is necessary to bolster these conclusions.

PLESIOSAUR REMAINS FROM CRETACEOUS HIGH-LATITUDE NON-MARINE DEPOSITS IN SOUTHEASTERN AUSTRALIA

Australian plesiosaur remains are common although currently poorly documented. At present, most of the described material is derived from extensive Early Cretaceous epicontinental marine rocks in central and northeastern Australia (Kear, 2003). In recent years, however, a number of fragmentary specimens have been recovered from Lower Cretaceous non-marine sequences in the southeastern part of the continent (Fig. 1). The fossil-producing strata are included within the middle Valanginian– early Albian Wonthaggi (Gippsland Basin) and Eumeralla (Otway Basin) formations, southern Victoria, and early–middle Albian Griman Creek Formation (Surat Basin), Lightning Ridge, New South Wales/ Surat region, Queensland. Interestingly, these units were deposited in an Early Cretaceous high-latitude zone (60–80o S), subject to highly seasonal, cool to cold conditions and months of winter darkness near the southern pole. Fossils recorded include a diverse range of freshwater/ terrestrial vertebrates, non-marine invertebrates, and plants (see Dettmann et al., 1992 for summary). Although several previous reports have mentioned plesiosaur material from southeastern Australia (e.g. Rich et al., 1988; Rich and Rich, 1989; Vickers-Rich, 1996; Smith, 1999; Rich and Vickers-Rich, 2000; Kear, 2003), none of the remains have yet been described. It is therefore, the purpose of this paper to present an up-to-date summary of the existing specimens (Table 1) and assess their taxonomic and paleoecological implications. Abbreviations—AM, Australian Museum, Sydney; NMV, Museum Victoria, Melbourne; QM, Queensland Museum, Brisbane.