Abstract
ObjectiveTwo separate and distinctive skills are necessary to find prey: Detection of its presence and determination of its location. Surface microscopy of the dentary of albertosaurines revealed a previously undescribed sensory modification, as will be described here. While dentary “foramina” were previously thought to contain tactile sensory organs, the potential function of this theropod modification as a unique localizing system is explored in this study.MethodDentary surface perforations were examined by surface epi-illumination microscopy in tyrannosaurine and albertosaurine dinosaurs to characterize their anatomy. Fish lateral lines were examined as potentially comparable structures.ResultIn contrast to the subsurface vascular bifurcation noted in tyrannosaurines (which lack a lateral dentary surface groove), the area subjacent to the apertures in albertosaurine grooves has the appearance of an expanded chamber. That appearance seemed to be indistinguishable from the lateral line of fish.ConclusionDentary groove apertures in certain tyrannosaurid lines (specifically albertosaurines) not only have a unique appearance, but one with significant functional and behavior implications. The appearance of the perforations in the dentary groove of albertosaurines mirrors that previously noted only with specialized neurologic structures accommodating derived sensory functions, as seen in the lateral line of fish. The possibility that this specialized morphology could also represent a unique function in albertosaurine theropods for interacting with the environment or facilitating prey acquisition cannot be ignored. It is suggested that these expanded chambers function in perceiving and aligning the body relative to the direction of wind, perhaps a Cretaceous analogue of the contemporary midwestern weathervane.
Highlights
The appearance of the perforations in the dentary groove of albertosaurines mirrors that previously noted only with specialized neurologic structures accommodating derived sensory functions, as seen in the lateral line of fish. The possibility that this specialized morphology could represent a unique function in albertosaurine theropods for interacting with the environment or facilitating prey acquisition cannot be ignored
The ratio of the relative size of the olfactory lobes of the brain compared to the greatest longitudinal linear measurement of the cerebral hemispheres has been utilized as a measure of sensory, or at least of olfactory function, in a wide variety of predatory and scavenging species of birds and dinosaurs [1,2,3,4]
Zelinitsky et al (2011) surveyed 157 taxa of birds and theropod dinosaurs using this method to assess the degree of olfactory capability in these animals
Summary
The ratio of the relative size of the olfactory lobes of the brain compared to the greatest longitudinal linear measurement of the cerebral hemispheres has been utilized as a measure of sensory, or at least of olfactory function, in a wide variety of predatory and scavenging species of birds and dinosaurs [1,2,3,4]. Zelinitsky et al (2011) suggest the same habits for Albertosaurines even though their olfactory ratios are uncertain Because of this lack of definitive information, it is desirable to generate an additional standard by which the olfactory sensory capabilities of tyrannosaurids and albertosaurines can be measured. The localization of prey or carrion by such methods, is more complex than is spotting it visually These feeding efforts might involve special sensory organs. Vertebrates depend on a typical set of five sensory modalities, some species have evolved the ability to detect other environmentally-pertinent information [7, 8] At times these enhancements have even resulted in the modification of sense organs for other purposes (Table 1)
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