The Qaidam hyena cranium prepared

Continued from Part IIb: the Qaidam hyena cranium discovered

With the help of Senior Preparator Mr. Howell Thomas at the Department of Vertebrate Paleontology (LACM), I opened up the jacket and began preparing the specimen in February 2008. After several weeks of careful preparation, we realized that the cranium was as complete as I had imagined, even though other crew members had some doubts about the completeness of the material by its state of deterioration in the field.

In addition, I was also able to confirm the identity of the specimen. It is the cranium of a hyena in the genus Adcrocuta. This genus is known so far by a single species, Adcrocuta eximia. However, without extensive comparison to other Chinese specimens of that species, I was not going to assign a species name to it just yet. The genus itself is significant because it is an index fossil. This means that the occurrences of this genus is restricted to a specific time period, in this case the later part of the late Miocene epoch. Even though the specimen itself probably does not reveal a great deal of new anatomical information, its occurrence in the Shengou locality area gives us another line of evidence of the geological age by its fossil animal remains (termed biochronology). In the absence of volcanic deposits to give us absolute dates, we have to rely on biochronological interpretations of geological ages of the fossil fauna.

[Jack prepares the Qaidam hyena cranium while Gabriella, the stuffed hyena, looks on]

[The cranium of Adcrocuta compared to a modern striped hyena (top left) and a spotted hyena (top right)]

In June 2008, the prepared Adcrocuta cranium was hand-carried back to the IVPP (Chinese Academy of Sciences), where I will be photographing and describing the skull in a scientific study of the important specimen later this year.

Carnivore fossils are generally rare occurrences; it was truly an honor for a student of carnivore paleontology to find a specimen of his research focus.

Check back soon for next in this series: fossil horns and antlers!


Growing fangs

On a recent visit to the George C. Page Museum, better known as Rancho La Brea, I examined a series of sabertooth skulls (Smilodon fatalis).

[milk teeth of a very young baby sabertooth]

In an ongoing effort to calculate the growth rate of the elongate upper canine of this species, I am working with Dr. Robert Feranec of the New York State Museum on correlating degree of tooth eruption versus enamel isotopic signals of growth. We are re-examining a growth series of sabertooth specimens originally described by Chris Shaw, the resident carnivore man at Rancho La Brea.

[another young individual, with some tooth wear]

By measuring the canine length erupted and the location of the line of enamelization, we could then calculate the rate of enamel deposition by dividing the metric differences in enamel length between young and older individuals by the already analyzed duration represented per unit enamel length acquired from isotope studies.

[a young sabertooth with fully erupted milk dentition]

Then, with an assumption of identical rates of growth between tooth eruption and enamelization, we could estimate the total time it took for the complete growth of an adult sabertooth canine.

[a specimen showing replacement of milk dentition by permanent teeth]

The calculations and measurements are still underway! Stay tuned for our results.

[a full adult Smilodon fatalis, with a saber measured at 163 millimetres (6.4 inches)!]