Tiny, long-armed dinosaur leads to rethink of dinosaur miniaturization
摘要
阿尔瓦雷斯龙类是一类小型兽脚类恐龙，曾被古生物学家误认为早期不会飞的鸟类，后确认为非鸟类恐龙中食蚁的一支。长期以来，学界认为其经历了与取食蚂蚁等社会性昆虫直接相关的罕见小型化演化过程。然而，新发现的一种名为Alnashetri cerropoliciensis的极小阿尔瓦雷斯龙化石表明，其演化过程可能并非如此简单线性。研究指出，该物种可能并非以蚂蚁为食，而是
Alvarezsaurids were mostly small-bodied theropods that paleontologists originally misinterpreted as early flightless birds, only to later recognize them as an ant-eating lineage of non-avian dinosaurs. For years, we suspected that Alvarezsaurids underwent a rare process of evolutionary miniaturization directly coupled to a diet of social insects like ants and termites. It was a tidy hypothesis: They got smaller to become more efficient at catching ants.
Now, a recently discovered fossil of one of the smallest alvarezsaurids ever found suggests that the evolution of miniature dinosaurs likely wasn’t as neat and linear as we thought. This new species, called Alnashetri cerropoliciensis, probably did not feed on ants at all. “It was a pursuit predator actively hunting insects and small mammals,” said Peter Makovicky, a paleontologist at the University of Minnesota.
The oddball
Alverezsaurids, found mostly in the Late Cretaceous rocks of Asia and South America, had short forelimbs tipped with a single oversized thumb claw built for digging. They also had minute teeth and sensory adaptations akin to those in modern nocturnal birds—everything necessary to work on termite mounds. “The explanation of their small body size has been tied to this specialization,” Makovicky explained.
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