Facial tilt in extant leporids is strongly correlated with locomotor mode – fast movers have more strongly tilted faces. There’s a lot of homoplasy, which is to be expected with characters that are strongly driven by current function. Kraatz and Sherratt (2016: fig. 5).
Judgmental readers will recall that I have dabbled in mammal skulls, thanks to the corrupting influence of my friend and colleague, Brian Kraatz. At the end of my last post on this sordid topic, I mentioned that Brian and Emma Sherratt were working on a version 2.0 based in 3D morphometrics. The first volley from that project was published today in PeerJ.
Happily for all of us, Brian and Em confirmed the relationship between facial tilt and locomotor mode that we first documented last year, using more taxa, more landmarks, and two more dimensions (Kraatz and Sherratt 2016: 12):
…in accordance with previous findings by Kraatz et al. (2015), facial tilt angle is correlated with locomotor mode (D-PGLS, F(2,17) = 11.13, P = 0.003), where lower facial tilt angle, meaning more pronounced cranial flexion, is found in cursorial species, and high angles are found in generalist species.
That’s just the most personally relevant tip of a very large, multifaceted iceberg, including a monster supplementary info package on FigShare with, among other things, 3D models of bunny skulls. It’s all free and awesome, so go have fun.
That homoplastic pattern shown in figure 5, above? It’s been going on for a while. I’m gonna go out on a limb and guess that Hypolagus was a rocket. Kraatz and Sherratt (2016: fig. 7).