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Stephen Wroe

Publications and source records attributed to Stephen Wroe.

8 recordsLinked to original sources
PubMed2005

Bottom-feeding plesiosaurs.

Elasmosaurid plesiosaurs were an important part of Cretaceous marine reptile communities and are generally considered to have been predators of small, agile, free-swimming fish and cephalopods. Two elasmosaurid specimens from Aptian and Albian deposits in Queensland, Australia, include fossilized gut contents dominated by benthic invertebrates: bivalves, gastropods, and crustaceans. Both specimens also contained large numbers of gastroliths (stomach stones). These finds point to a wider niche than has previously been supposed for these seemingly specialized predators and may also influence long-running controversy over the question of gastrolith function in plesiosaurs.

Animals↗
PubMed2005

Prolonged coexistence of humans and megafauna in Pleistocene Australia.

Recent claims for continent wide disappearance of megafauna at 46.5 thousand calendar years ago (ka) in Australia have been used to support a "blitzkrieg" model, which explains extinctions as the result of rapid overkill by human colonizers. A number of key sites with megafauna remains that significantly postdate 46.5 ka have been excluded from consideration because of questions regarding their stratigraphic integrity. Of these sites, Cuddie Springs is the only locality in Australia where megafauna and cultural remains are found together in sequential stratigraphic horizons, dated from 36-30 ka. Verifying the stratigraphic associations found here would effectively refute the rapid-overkill model and necessitate reconsideration of the regional impacts of global climatic change on megafauna and humans in the lead up to the last glacial maximum. Here, we present geochemical evidence that demonstrates the coexistence of humans and now-extinct megafaunal species on the Australian continent for a minimum of 15 ka.

Analysis of Variance↗
PubMed2005

Bite club: comparative bite force in big biting mammals and the prediction of predatory behaviour in fossil taxa.

We provide the first predictions of bite force (BS) in a wide sample of living and fossil mammalian predators. To compare between taxa, we calculated an estimated bite force quotient (BFQ) as the residual of BS regressed on body mass. Estimated BS adjusted for body mass was higher for marsupials than placentals and the Tasmanian devil (Sarcophilus harrisii) had the highest relative BS among extant taxa. The highest overall BS was in two extinct marsupial lions. BFQ in hyaenas were similar to those of related, non-osteophagous taxa challenging the common assumption that osteophagy necessitates extreme jaw muscle forces. High BFQ in living carnivores was associated with greater maximal prey size and hypercarnivory. For fossil taxa anatomically similar to living relatives, BFQ can be directly compared, and high values in the dire wolf (Canis dirus) and thylacine (Thylacinus cynocephalus) suggest that they took relatively large prey. Direct inference may not be appropriate where morphologies depart widely from biomechanical models evident in living predators and must be considered together with evidence from other morphological indicators. Relatively low BFQ values in two extinct carnivores with morphologies not represented among extant species, the sabrecat, Smilodon fatalis, and marsupial sabretooth, Thylacosmilus atrox, support arguments that their killing techniques also differed from extant species and are consistent with 'canine-shear bite' and 'stabbing' models, respectively. Extremely high BFQ in the marsupial lion, Thylacoleo carnifex, indicates that it filled a large-prey hunting niche.

Animals↗
PubMed2004

On the rarity of big fierce carnivores and primacy of isolation and area: tracking large mammalian carnivore diversity on two isolated continents.

The hypothesis that low productivity has uniquely constrained Australia's large mammalian carnivore diversity, and by inference the biota in general, has become an influential backdrop to interpretations of ecology on the island continent. Whether low productivity has been primary impacts broadly on our understanding of mammalian biogeography, but investigation is complicated by two uniquely Australian features: isolation and the dominance of marsupials. However, until the great American biotic interchange (GABI), South America was also isolated and dominated by pouched carnivores. Here, we examine the low-productivity hypothesis empirically, by comparing large mammalian carnivore diversities in Australia and South America over the past 25 Myr. We find that pre-GABI diversity in Australia was generally comparable to or higher than diversity in South America. Post-GABI, South American diversity rose dramatically, pointing to isolation and phylogenetic constraint as primary influences. Landmass area is another important factor. Comparisons of diversity among the world's seven largest inhabited landmasses show that large mammalian hypercarnivore diversity in Australia approached levels predicted on the basis of landmass area in Late Pleistocene-Recent times, but large omnivore diversity was low. Large marsupial omnivores also appear to have been rare in South America. Isolation and competition with large terrestrial birds and cryptic omnivore taxa may have been more significant constraints in this respect. Relatively high diversity has been achieved in Late Quaternary America, possibly as a result of 'artificially' high immigration or origination rates, whereas that in contemporaneous Africa has been surprisingly poor. We conclude that isolation and landmass area, rather than productivity, are the primary constraints on large mammalian carnivore diversity. Our results quantify the rarity of large hypercarnivorous mammals worldwide.

Animals↗
PubMed2004

The size of the largest marsupial and why it matters.

We show that at 2786 kg, the largest known marsupial, Diprotodon optatum, was much larger than has previously been suggested. Our results contradict the conclusion that the maximum attainable body mass of an Australian marsupial has been constrained by low productivity.

Animals↗