There is a growing body of evidence demonstrating the impacts of human arrival in new “pristine” environments, including terrestrial habitat alterations and species extinctions. However, the effects of marine resource utilization prior to industrialized whaling, sealing, and fishing have largely remained understudied. The expansion of the Norse across the North Atlantic offers a rare opportunity to study the effects of human arrival and early exploitation of marine resources. Today, there is no local population of walruses on Iceland, however, skeletal remains, place names, and written sources suggest that walruses existed, and were hunted by the Norse during the Settlement and Commonwealth periods (870–1262 AD). This study investigates the timing, geographic distribution, and genetic identity of walruses in Iceland by combining historical information, place names, radiocarbon dating, and genomic analyses. The results support a genetically distinct, local population of walruses that went extinct shortly after Norse settlement. The high value of walrus products such as ivory on international markets likely led to intense hunting pressure, which—potentially exacerbated by a warming climate and volcanism—resulted in the extinction of walrus on Iceland. We show that commercial hunting, economic incentives, and trade networks as early as the Viking Age were of sufficient scale and intensity to result in significant, irreversible ecological impacts on the marine environment. This is to one of the earliest examples of local extinction of a marine species following human arrival, during the very beginning of commercial marine exploitation.
Background Trematosaurines are a widespread group of early tetrapods (Temnospondyli, Stereospondyli) known from all continents except South America and Antarctica. They radiated rapidly during the Early Triassic just after the End Permian mass extinction and are of interest to understand the recovery of the ecosystems just after extinction. Trematosaurines disappeared during the Late Triassic. Objective Herein, a re-description of the genus Angusaurus is presented based on a new specimen. This genus is known from the Early Olenekian (Early Triassic) of Russia and comprises four valid species, although the diagnostic characters that deine some of them are vague and controversial. Methods The new specimen described, using MicroCT scanner and 3D digital modeling, sheds light on the anatomical details of the external and inner cranial structure, and provides new details of the neurocranium as well as the ontogeny of this genus. Results and Discussion A cladistic analysis of trematosaurines (including most trematosauroids) confirms the problematic nature of some Angusaurus species and provides a basis for detailed discussion about the phylogeny of trematosaurines.
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