Were Mosasaurs Warm Blooded?

Endothermic mosasaurs? Possible thermoregulation of Late Cretaceous mosasaurs (Reptilia, Squamata) indicated by stable oxygen isotopes in fossil bioapatite in comparison with coeval marine fish and pelagic seabirds

Authors:

Lynn Harrell et al

Abstract:

The thermoregulatory style of Late Cretaceous mosasaurs has become a highly controversial subject in vertebrate palaeontology. These extinct marine reptiles have previously been described as poikilothermic, endothermic or gigantothermic. Here we analyse three genera of mosasaurs from the Mooreville Chalk in Alabama (USA) of differing body mass, and compare their δ18OPO4 derived body temperatures (Tb) with those of coeval poikilothermic fish (Enchodus) and endothermic pelagic seabirds (Ichthyornis). Results show that all mosasaurs, Clidastes (Tb = 33.1°C), Platecarpus (Tb = 36.3°C), and Tylosaurus (Tb = 34.3°C), had elevated average body temperatures in relation to those of the fish (Tb = 28.3°C) and were closer to those of Ichthyornis (Tb = 38.6°C). The temperatures calculated for Enchodus compare well with previously reported temperature estimates for the Mooreville Chalk and the Tb of Ichthyornis compares well with temperatures that have been reported for modern seabirds, suggesting that this method provides accurate results. Finally, although there are small differences of body temperature among mosasaur genera, these are independent of size, and thus inferred body mass, suggesting that mosasaurs were not gigantotherms, but rather endotherms.

Giant Monitor Lizards Survived in Australia at Least Until Humans Arrived

As if life wasn't hard enough during the last Ice Age, research led by the University of Queensland has found Australia's first human inhabitants had to contend with giant killer lizards.

UQ vertebrate palaeoecologist Dr Gilbert Price said researchers working in Central Queensland were amazed when they unearthed the first evidence that Australia's early human inhabitants and giant apex predator lizards had overlapped.

"Our jaws dropped when we found a tiny fossil from a giant lizard during a two metre deep excavation in one of the Capricorn Caves, near Rockhampton," Dr Price said.

"The one-centimetre bone, an osteoderm, came from under the lizard's skin and is the youngest record of a giant lizard on the entire continent."

Dr Price and his colleagues used radiocarbon and uranium thorium techniques to date the bone as about 50,000 years old, coinciding with the arrival of Australia's Aboriginal inhabitants.

"We can't tell if the bone is from a Komodo dragon -- which once roamed Australia -- or an even bigger species like the extinct Megalania monitor lizard, which weighed about 500kg and grew up to six metres long," Dr Price said.

"The find is pretty significant, especially for the timeframe that it dates."

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Did Small Theropods Compete With Varanid Lizards in the Tropics of Campanian Cretaceous Texas?

A theropod tooth assemblage from the lower Aguja Formation (early Campanian) of West Texas, and the roles of small theropod and varanoid lizard mesopredators in a tropical predator guild

Authors:

Wick et al

Abstract:

A theropod tooth assemblage from the lower shale member of the Aguja Formation in West Texas is part of a diverse microvertebrate fauna, designated the Lowerverse local fauna, of early Campanian age (c. 80 – 82 Ma). The fauna includes as many as nine distinct theropod taxa along with several indeterminate archosaurs and birds. Theropod tooth types (indeterminate tyrannosaurids, cf. Saurornitholestes, cf. Richardoestesia, cf. Paronychodon) are similar to those found in the upper shale member of the Aguja, as well as in other Campanian theropod assemblages from western North America. However, the most abundant tooth morphotype is unique, and attributed to a new varanoid lizard with remarkably theropod-like dentition, herein designated Dryadissector shilleri (gen. et sp. nov.). The presence of many unique theropod tooth morphotypes in the Lowerverse local fauna suggests that there remains significant undiscovered diversity among small theropods in southern latitude faunas, and accords with recognition of distinct latitudinal biomes during Campanian time in western North America. Due to their similar dentition, small theropods, along with varanoid lizards, may have served similar ecological roles as competitive mesopredators in the Campanian tropical predator guild.

Monitor Lizards in Miocene Neogene Spain

Early Miocene dispersal of the lizard Varanus into Europe: Reassessment of vertebral material from Spain

Authors:

Delfino et al

Abstract:

Iberovaranus Hoffstetter, 1969 was erected as a monotypic genus of varanine varanid lizard on the basis of a single trunk vertebra from the Miocene of Spain. Thanks to the study of the holotype, as well as of a still undescribed cervical vertebra from the same locality, we show that the vertebral morphology of Iberovaranus is contained within the known variability of Varanus. Therefore, Iberovaranus Hoffstetter, 1969 is considered a subjective junior synonym of Varanus Merrem, 1820, and the species Iberovaranus catalaunicus Hoffstetter, 1969 should be considered a nomen dubium.