This collaborative project involves university and museum scientists in research on a key evolutionary novelty: the genetic origin and morphological evolution of baleen and filter feeding in baleen (mysticete) whales. Living baleen whales lack teeth, and use plates of baleen to feed, but they evolved from ancestors that had teeth. Study of baleen structure, its bony correlate (palate vascularization) and other anatomical characters related to whale feeding mechanisms will focus on an enigmatic group of fossil baleen whales ('cetotheres') implicated in the evolution of extant lineages of mysticetes. Newly discovered baleen whale fossils will be prepared and described. Hypotheses on the evolution of feeding in mysticetes also will be tested. Anatomical, molecular, and combined datasets will provide context for documenting this major evolutionary transition in mysticetes.
This research will use evidence from fossils, development, molecules, and phylogeny to document a major macroevolutionary transition from toothed mysticetes that pursued individual prey items to baleen-bearing mysticetes that are bulk-feeding predators. This project will provide training for both undergraduate and graduate students. Results of this study will be incorporated into a project website and exhibits on whale evolution at the San Diego Natural History Museum.
This collaborative project involved university and museum scientists in research on a key evolutionary novelty-the origin and morphological evolution of baleen and batch filter feeding in mysticete whales. This remarkable batch-feeding behavior described as the world’s largest biomechanical event is achieved via a series of behavioral and anatomical modifications. The principal structure involved in batch filter feeding is baleen. Baleen is an epidermal tissue that hangs in racks suspended from the roof of the mouth and is used to strain fish and zooplankton. Our study focused on the structure and comparative anatomy of baleen, its bony correlate (palate vascularization) and other anatomical characters related to feeding (e.g. wide skull, large mouths, flexible jaws). We identified a step-wise transition of morphological characters, such as a broad rostrum, thin lateral margins of the maxillae and lateral bowing of the jaws which evolved early (prior to 28 million years ago) among baleen whales before the evolution of nutrient foramina that nourish and innervate the baleen and subsequent loss of the teeth. Anatomical, molecular and combined datasets were employed to provide an evolutionary context for documenting this major evolutionary transition. This research used evidence from fossils, development, molecules and phylogeny to document a major macroevolutionary transition from stem toothed mysticetes as single prey pursuit predators to baleen-bearing mysticetes as batch feeding predators. The importance of morphological characters, particularly fossil data, was critical to understanding the relative order of the more important evolutionary modifications involved in feeding. This project provided training for two undergraduate students, four Master’s students and one postdoctoral fellow in the Department of Biology at San Diego State University.
