Q.: Should We Be Thinking Of What We Call "Rex"... As At Least THREE Species?

We are in sore need of some less-ominous news than large Ukraine nuclear plants set ablaze by Russian conscripts, tonight. . . so we will look backward in time:

Of course, what we call them is of secondary importance. . . to how they have completely captured the imaginations. . . of generations of all our kids.

It is rather exciting though, that we might soon refer to "Regina" instead of "Rex" -- for our "Sue" at the Field Museum. We shall see -- here is the story tonight, and a bit:

. . .Of the Tyrannosaurus specimens, 28 could be identified in distinct layers of sediment (stratigraphy) at the Lancian upper Masstrichtian formations in North America (estimated to be from between 67.5 to 66 million years ago). The authors compared Tyrannosaurus specimens with other theropod species found in lower layers of sediment. . . .

The authors nominate two potential new species of Tyrannosaurus based on their analysis. The first, Tyrannosaurus imperator (tyrant lizard emperor), relates to specimens found at the lower and middle layers of sediment, characterized with more robust femurs and usually two incisor teeth. The authors argue these features have been retained from earlier ancestors (tyrannosaurids). The second, Tyrannosaurus regina (tyrant lizard queen), is linked to specimens from the upper and possibly middle layers of sediment, characterized with slenderer femurs and one incisor tooth. The recognized species Tyrannosaurus rex (tyrant lizard king) was identified in the upper and possibly middle layer of sediment with specimens classed as retaining more robust femurs while having only one incisor tooth. Some specimens could not be identified based on their remains so were not assigned to a species. . . .

The authors acknowledge that they cannot rule out that the observed variation is due to extreme individual differences, or atypical sexual dimorphism, rather than separate groups, and they also caution that the location within sediment layers is not known for some specimens. The authors discuss the difficulties of assigning fossil vertebrates to a potential new species.

The authors conclude that the physical variation found in Tyrannosaurus specimens combined with their stratigraphy are indicative of three potential groups that could be nominated as two new species, T. I and T. Regina, alongside the only recognized species to date, T. Rex. . . .

We are grinning with crinkly eyes, now -- thinking of the wide array of various plaster, balsa wood and/or stuffed cloth home-made Tyrannosaurs we conjured up and assembled primarily late at night (for science project diaramas), at what is now almost two decades ago, but it seems to me to have been just. . . the other night (see lower portion of the image, for proof). Smile -- sweet times.

नमस्ते