Maip

Chapter • Meet the dinosaur

Overview

Maip macrothorax was a large predatory dinosaur belonging to the megaraptorids, a group of slender but powerful theropods that dominated South America towards the end of the Cretaceous. At an estimated 9–10 metres long and weighing roughly 3.5–5 tonnes, Maip is the largest megaraptorid described so far. The species name macrothorax refers to its unusually wide chest: the preserved ribs indicate a thoracic cavity at least 1.2 metres across. Its vertebrae were riddled with air-filled chambers, just as in modern birds, keeping the skeleton light for an animal of that size. Like other coelurosaurs, Maip is thought to have carried at least simple filament-like feathers on parts of its body, although no skin impressions are known for this particular species. Megaraptorids looked very different from the heavy-skulled tyrannosaurs of the northern hemisphere. They had long, muscular arms ending in enormous, strongly curved claws on the thumb and index finger — in the related Megaraptor the thumb claw exceeded 35 centimetres. The skull was long and comparatively narrow, lined with small, blade-like teeth. Researchers interpret this combination to mean that Maip did not kill with a bone-crushing bite, but instead grappled prey with its forelimbs and inflicted rapid slashing bites. The body was held horizontally over two powerful hind legs, with the long tail stretched out behind as a counterweight, never dragging on the ground. Maip lived in a cool, humid landscape in what is now southern Patagonia, and was probably one of the region's apex predators during the last few million years of the Cretaceous. Likely prey included small titanosaurs, elasmarian ornithopods and other medium-sized vertebrates sharing the same floodplains. Because only part of the skeleton is preserved — cervical, dorsal and caudal vertebrae, ribs, chevrons, part of the shoulder girdle and a metacarpal — many of the size estimates rely on comparison with better-known relatives such as Megaraptor and Aerosteon. The holotype, catalogued as MPM 21545, was recovered at Estancia La Anita near El Calafate in Santa Cruz Province, Argentina, from beds of the Chorrillo Formation. Excavations took place in 2019 and 2020, and the species was formally described in 2022 by Alexis Aranciaga Rolando and colleagues in Scientific Reports. The name Maip comes from the mythology of the Aonikenk (Tehuelche) people, in which Maip is an evil shadow that kills with cold wind — a fitting nod to the freezing gales of the Patagonian steppe.

Chapter • Where it lived

Habitat

Maip lived roughly 72–70 million years ago, during the Maastrichtian stage at the close of the Cretaceous, in what is now southern Patagonia. Its fossils come from the Chorrillo Formation at Estancia La Anita in Santa Cruz Province, Argentina, not far from El Calafate. The landscape was one of floodplains and meandering rivers, with forests of Nothofagus-like trees, ferns and early flowering plants. The region lay at a high southern latitude, meaning cool temperatures and strongly seasonal daylight. The same beds have yielded titanosaurs, ornithopods, unenlagiine dromaeosaurids, early mammals and a rich plant fossil assemblage.

Chapter • Wild behavior

Behavior & Ecology

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Chapter • Scientific place

Taxonomy