Virtual Reconstruction and Prey Size Preference in the Mid Cenozoic Thylacinid, <i>Nimbacinus dicksoni</i> (Thylacinidae, Marsupialia)

<div><p>Thylacinidae is an extinct family of Australian and New Guinean marsupial carnivores, comprizing 12 known species, the oldest of which are late Oligocene (∼24 Ma) in age. Except for the recently extinct thylacine (<i>Thylacinus cynocephalus</i>), most are known from fragmentary craniodental material only, limiting the scope of biomechanical and ecological studies. However, a particularly well-preserved skull of the fossil species <i>Nimbacinus dicksoni</i>, has been recovered from middle Miocene (∼16-11.6 Ma) deposits in the Riversleigh World Heritage Area, northwestern Queensland. Here, we ask whether <i>N. dicksoni</i> was more similar to its recently extinct relative or to several large living marsupials in a key aspect of feeding ecology, i.e., was <i>N. dicksoni</i> a relatively small or large prey specialist. To address this question we have digitally reconstructed its skull and applied three-dimensional Finite Element Analysis to compare its mechanical performance with that of three extant marsupial carnivores and <i>T. cynocephalus</i>. Under loadings adjusted for differences in size that simulated forces generated by both jaw closing musculature and struggling prey, we found that stress distributions and magnitudes in the skull of <i>N. dicksoni</i> were more similar to those of the living spotted-tailed quoll (<i>Dasyurus maculatus</i>) than to its recently extinct relative. Considering the Finite Element Analysis results and dental morphology, we predict that <i>N. dicksoni</i> likely occupied a broadly similar ecological niche to that of <i>D. maculatus</i>, and was likely capable of hunting vertebrate prey that may have exceeded its own body mass.</p></div