66 - The Tale of Two Skulls: A Cat Canine Chronicle

Poster Board Number: 66
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Odd poster #s – first hour
Even poster #s – second hour

Abstract Body : Introduction & Objective
In the 1800s the first Smilodon fatalis (Felidae, Machairodontinae) was found by Leidy (1868). Since then scientists have wondered how Smilodon moved, what it ate and how it killed prey.
Reconstructions to date have shown the elongate maxillary canines with more than 50% of the tooth exposed. However, these reconstructions do not consider the depth of the canine alveoli and the gape is estimated to be up to 110-120º of mandibular rotation, larger than any living cat.
Correlating data can help answer these questions, including the movements of the mandible. Showing the canines in the proper placement and why could change the previous theories on how Smilodon ate. Our work combines the results of previous studies and proposes the proper location of the canines and a gape that realistically represents what the living sabertooth could do.

Methods and Materials
We used measuring tools: a centimeter ruler, a quarter, a dial caliper, a log book, and a Nikon Z6 ii camera with a 24-70/4s lens.

Results
A study of S. fatalis at Rancho la Brea identified two skulls with associated canines, one from the recent pit 23 LACMP23-7550, and the other from Pit 13 2001-3 in the 1900s. This is unusual because most specimens were conserved prior to 1930 with the canines disassociated.
There is pit wear on LACMP23-7550, that goes through the skull and into the dentine of the canine showing that this canine is associated. The other skull has a canine, broken due to pit wear, but retains an intact root. Changes in the alveolus include cracks and shrinkage.

Conclusions
These two skulls both show that the alveolus had shrunk and cracked along the sutures. Bones shrink 8%-12% post-mortem. A shrunken alveolus does not allow the canine to be fully seated and having matrix in the majority of alveoli in other skulls confounds the ability to seat the canines (to 50% of their total length).

Significance/Implication
The shrunken and often matrix-filled alveolus changes the placement of the canines. Additionally, pit wear usually confounds any analysis of Rancho La Brea specimens, but in this case, the pit wear proves the provenance of the teeth beyond even the conservation record. The skull from pit 23 has a hole that was most likely formed by pit wear and the damage is through the skull, into the alveolus, through the enamel, and into the dentine. This proves without a doubt that the canines were present in this specimen in vivo.
These two skulls with pit wear show that the canines are associated and placed correctly. The ability to show that the canines are associated with a specific skull and that the placement of the canines are seated at 50% of the tooth length in the alveoli changes the displayed length of the canine, changes the degree of gape, and changes the mandibular rotation so that it puts Smilodon’s gape in line with that of extant big cats.