An illustration shows what the recently discovered Tyrannosaurus mcraeensis specimen may have looked like when it roamed the Earth.
宾州中央谷. — The ferocious Tyrannosaurus 雷克斯 lived between approximately 68 to 66 million years ago, but a team of researchers that includes a 中国博彩平台 professor has identified a new species of Tyrannosaurus that dates back even further — essentially an ancestor of the fearsomely named "tyrant lizard king.” They published their finding in 科学报告.
D. 爱德华Malinzak, assistant teaching professor of biology at Lehigh Valley, is one of the researchers studying the specimen and co-authored the study, which was led by Sebastian Dalman, doctoral candidate at Montana State University. The specimen is no longer referred to as T. 雷克斯 but by its own species name, Tyrannosaurus mcraeensis. Malinzak said the specific name mcraeensis was chosen in reference to the geologic feature from which the specimen was recovered.
A group of people discovered the specimen — a nearly complete lower jaw — while canoeing on a lake in Elephant Butte in south-central New Mexico in the early 1980s.
“The lower jaw was lying down along the edge of the lake. Eventually the specimen was donated to the New Mexico Museum of Natural History and Science (NMMNH),达尔曼说. “More bones of this Tyrannosaurus were found by the field crew from NMMNH in the late 1990s.”
被认为是T. 雷克斯 at first, further analysis has shown the specimen is actually older than the T. 雷克斯.
它被称为T. 雷克斯 first; however, recent radioisotopic dating of the stratigraphic unit in the Hall Lake Formation in which Tyrannosaurus mcraeensis was found show an age of 74 million years,达尔曼说. “It’s really an ancestor of the T. 北美洲的雷克斯. 人们相信T. 雷克斯 came from Asia, but it looks like they went from North America to Asia and not the other way.”
Discovering and researching the specimen was very much a team effort, 据马林扎克说, 谁在2019年加入了这个项目.
“I met up with [Dalman] in South Dakota and started talking, and I asked if anyone was doing paleobiogeographic work,他说. He later connected with the team from the NMMNH and became part of this project. “人们以为是T. 雷克斯 all this time, but if you look at everything in the whole picture, it doesn’t really come close. With the time gap, there is a temporal difference between the species. It gives us some extremely important information — it’s the origin story for T. 雷克斯.”
Malinzak's contributions to the work focused on comparing the specimen against other closely related tyrannosaurs to better understand the way in which the structure and shape of the jaw differed from other tyrannosaur species.
“I also contributed to the discussion of the specimen in terms of paleobiogeography and evolutionary implications,马林扎克说, who previously conducted work related to Laramidia, an ancient continent comprising the western half of modern-day North America from Alaska to Mexico. "Through several back-and-forth conversations regarding various aspects [of the research process], we were able to synthesize a hypothesis as to the evolutionary implications this specimen/taxon might have in our understanding of ... evolutionary history and specifically the evolution of Tyrannosaurus.”
