It was a real surprise when the researchers realized this Alnashetri was not a highly specialized, late-stage Alvarezsauroid. Instead, it occupied an early branching position among the earlier, basal members of the clade, despite living in the Late Cretaceous.
This combination of small size and early branching status fundamentally disrupts our previous model of how these animals evolved. If the miniaturization of Alvarezsauroids was strictly related to their lifestyle as fine-armed insectivores, early diverging species Alnashetri it must have some transitional properties in a steady, large-scale march toward this extreme endpoint. But it didn’t seem that way.
“It’s a very long-legged animal, so it was probably quite fast. My best analogy would be something like a roadrunner from the American West,” Makovicky said.
Arms and teeth
The last Alvaressaurids had small, sturdy forelegs less than half the length of their femurs. Alnashetrialthough it sported relatively long forelegs that were 61 percent of its entire hind leg length. Although it had three-fingered hands with a robust first digit, which was the hallmark of its group, it still retained slender second and third digits, unlike its later relatives.
Other features that challenge the established evolutionary model of miniature dinosaurs Alnashetrijaws and teeth. Their teeth have serrated teeth set in sockets, but importantly, these teeth are not very small, as in late Alvaressaurids. Enthusiasm or Jaculinykus. “This decoupled the evolution of small body size from anatomical specializations,” Makovicky said.
The team concluded that extreme miniaturization in Alvarezsaurids did not co-evolve with the evolution of small arms better suited for digging, or the evolution of small teeth designed to crush ants and/or termites. A new evolutionary model instead of a large-scale trend in which an entire generation steadily shrinks over time Alnashetri It shows that Alvarezsaurid body mass varied many times. Alnashetriit appears that the 700-gram frame was achieved independently of other highly specialized alvarezsaurid species.
