Comparing Cats: A Discussion of Similarities & Differences

[LandSeaLion]

On the topic of skull comparisons, here is an interesting study on the morphology of cat skulls (and the performance of jaw and neck muscles), published about 10 years ago in the Zoological Journal of the Linnean Society by F. Sicuro and L. Oliveira.

https://academic.oup.com/zoolinnean/article/161/2/414/2732061

This was performed with Principal Component Analysis (PCA) on various measurements. Full discussion of their methodology is provided in the link. 

In the first part on morphology, PC1 (horizontal axis) is associated with skull size, while PC2 (vertical axis) is associated with the skull shape:

“The measurements mainly associated with PC2 were: anterior width across parietals, just behind the supraorbital process (POC) and the masseteric scar width (MSW), both with negative coefficients; and temporal fossa length (TFL), with a positive coefficient. PC2 is associated with the breadth of the anterior part of the braincase, masseter robustness, and the elongation of the posterior half of the skull (denoted by the length of the temporal fossa). The coefficient of POC was considerably higher than the others, indicating a leading role in the morphological aspect depicted by this PC.”

All cats in the study:

*This image is copyright of its original author

https://academic.oup.com/view-large/figure/81729526/ZOJ_636_f3.gif

And the pantherine cats in particular:

*This image is copyright of its original author

https://academic.oup.com/view-large/figure/81729530/ZOJ_636_f4.gif

“The PC1 scores (Fig. 4) reflect the size superiority of the panthers among the felids (F7, 607= 240.61, P < 0.0000001; Tukey's HSD test, P < 0.0001). Lions and tigers are the largest species, and the clouded leopard is the smallest one (F5, 118= 138.30, P < 0.00001). There is no difference in the overall skull size between lions (Panthera leo) and tigers (Panthera tigris), and both are bigger than all of the other cat species (Tukey's HSD test, P < 0.001). The jaguar (Panthera onca) is the second biggest cat (P < 0.001), followed by leopards (Panthera pardus) and snow leopards (Uncia uncia), which are of the same size (P < 0.001).

The PC2 scores denote a marked dichotomy between the elongated skull pattern of the clouded leopard (Neofelis nebulosa), with a narrow width of anterior portion of braincase, and the short and broad skull of U. uncia. The intermediate-sized panthers (P. onca and P. pardus) show a bias to the elongated/narrow pattern, whereas the big panthers have more regular skulls. The PC2 scores indicate no significant differences between lions and tigers (F5, 118= 45.16, P < 0.00001; Tukey's HSD test, P> 0.18), regarding the skull measurements associated with the second principal component. This could be noted as an overall morphological similarity between the skulls of P. leo and P. tigris, despite the conspicuous features exhibited by these species. However, this result takes into account the pooled within variance among the very diverse panther species. The direct comparison between the PC2 scores of P. leo and P. tigris indicates that they are clearly different (F1, 41= 6.81, P < 0.01).

The comparison of measurement ratios allowed for a better perception of the panthers skull design. For instance, U. uncia shows the largest postorbital constriction (POC/CBL, F5, 118= 33.51, P < 0.00001; Tukey's HSD test, P < 0.001) among the panthers; N. nebulosa possesses the highest proportion of temporal fossa length (TFL/CBL, F5, 118= 33.80, P < 0.00001; Tukey's HSD test, HSD test, P < 0.04). Panthera leo and P. onca equally show the largest ratios of height of jaw bone at M1(JHM1/CBL, F5, 118= 24.54, P < 0.00001; Tukey's HSD test, P < 0.04); whereas P. tigris exhibits the widest jaw bone at M1(JWM1/CBL, F5, 118= 13.14, P < 0.00001; Tukey's HSD test, P < 0.04). These two latter measurements are related to the robustness of the dental bone, and, together, they are indicative of the potential load that a jaw could resist during the bite.

(Cont.)”

The second part focused on force indexes. Here, PC1 is indicative of bite strength and neck muscle robustness, while PC2 is associated with “contribution of the temporalis and masseter mechanical systems to the final bite force” / “the influence of the skull design to the jaw muscles performance.”

Not surprisingly, lions and tigers topped the list, with jaguars coming in third and leopards fourth:

*This image is copyright of its original author

https://academic.oup.com/view-large/figure/81729598/ZOJ_636_f12.gif

*This image is copyright of its original author

https://academic.oup.com/view-large/figure/81729601/ZOJ_636_f13.gif

“Panthers, as expected, have the most powerful bite and neck robustness among felids (Fig. 13). Lions (P. leo) and tigers (P. tigris) show a similar final bite force, with both of them being more powerful than all other cats (H26, 599 = 563.97, P < 0.0001, Dunn's testP < 0.01). A bite strength gradient is observed on other panthers, with an obvious correlation to their skull and body sizes. Leopards (P. pardus) and snow leopards (U. uncia) show a similar efficiency on jaw occlusion (Dunn's testP > 0.05), despite their skull shape differences.

Lions and tigers share an overall similarity in skull morphology and size, and have the same potential for strong bites at the canines. However, according to PC2, the jaw occlusion of P. leo is greatly influenced by the action of the masseteric complex, which is quite different from that of P. tigris(F5, 118 = 57.97, P < 0.0001; Tukey's HSD test, P < 0.001).

Tigers (P. tigris) show the same pattern in jaw occlusion that is observed in jaguars (P. onca), leopards (P. pardus), and snow leopards (U. uncia). All these species display a smaller contribution of the masseteric muscle system to the bite than that observed in lions (P. leo).
On the other hand, the jaw occlusion of clouded leopards is deeply marked by the mechanical system of the temporalis muscle (PC2 scores, Tukey's HSD test, P < 0.001), and the participation of the masseteric complex is much less substantial than that observed in other panthers. 

(Cont.)”

There’s more info in that link, including contrasts between the morphological and functional analyses. Reply