![]() ![]() ![]() As a result, the skull shows a complex architecture made of several bone bars, typical also for other theropod dinosaurs. In addition to the ancestral temporal fenestrae, large cranial openings in the snout and the lower jaw are thought to decrease skull weight and to better distribute strain when processing food, but also other morphofunctional reasons have been discussed such as specific muscle insertions, shock absorption, pneumaticity, and internal skull mobility 6, 8, 9. Its skull length is about a sixth of the total body length, and cranial performance analyses resulted in reconstructions of a very powerful bite force 3, 4, 5, 6, 7. Its unique anatomy, including an immense skull and small forelimbs, has inspired a number of morphofunctional experiments 1, 2. The hypercarnivore Tyrannosaurus rex (Theropoda) is an icon of paleontology and evolution. As such, this study provides a framework for future research focusing on the evolution of modularity on lower taxonomic levels. Our general conclusions on amniote skull integrity are obviously preliminary and should be tested in subsequent studies. Mode of food processing primarily shaped skull integration among amniotes, however, phylogenetic patterns of skull integration are low in our sampling. The complex tyrannosaur skull modularity likely represents a refined mosaic of phylogenetic and ecological factors with food processing being probably most important for shaping its skull architecture. Kinetic forms also show great diversity in modularity. The akinetic skull of opossum, alligator, and leatherback turtle evolved in independent ways mirrored in different patterns of skull modularity. Independent pathways of bone reduction in opossum and chicken resulted in different degrees of cranial complexity with chicken having a typical sauropsidian pattern. Our results reveal that the tyrannosaur has the most modular skull organization among the amniotes included in our study, with an unexpected separation of the snout in upper and lower sub-modules and the presence of a lower adductor chamber module. We apply for the first time anatomical network analysis to study skull bone integration and modular constructions in tyrannosaur and compare it with five representatives of the major amniote groups in order to get an understanding of the general patterns of amniote skull modularity. Extant fully terrestrial vertebrates (amniotes) provide the best opportunities in that regard, as their skull performance is known from life. Understanding morphofunctional complexity of this impressive skull architecture requires a broad scale phylogenetic comparison with skull types different to that of dinosaurs with fundamentally diverging cranial regionalization. rex, they are thought to decrease skull weight, because, unlike most other amniotes, the skull proportion is immense compared to the body. In addition, like in other dinosaurs, its snout and lower jaw show large cranial fenestrae. Like other diapsids, Tyrannosaurus rex has two openings in the temporal skull region. ![]()
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