Abstract
The transition of early semi-aquatic archaeocetes to fully aquatic modern whales and dolphins is documented by a wealth of fossil evidence, and one of the most profound and well-studied macroevolutionary events in mammalian history. However, despite a fairly comprehensive understanding of the cetacean evolutionary pathway, only very few modern accounts have amalgamated arrangements of the soft tissue in the shoulder and forelimb with evolutionary aspects.
In this study, a total of 62 specimens comprising 15 species have been investigated and morpho-functional characteristics of the shoulder and forelimb integrated into behavioural, physiological and phylogenetic aspects. A thorough literature research complemented these findings.
In Chapter 2 Caperea new osteological characteristics, and for the first time myological arrangements, are described for the pygmy right whale (Caperea marginata), the sole member of the family Neobalaenidae. Some unique traits, only seen in fossil Cetotheriidae, give credence to a possible close affiliation with this extinct family. Other morphological attributes of the forelimb are the unique ability amongst whales to change the contour of the flipper and possibly also correlated functional attributes.
Chapter 3 Berardius investigates for the first time soft tissue arrangements of the shoulder and forelimb in Arnoux’s beaked whale (Berardius arnuxii, Ziphiidae). Despite highly derived morphological, physiological and behavioural adaptations to extreme deep-diving, Arnoux’s beaked whales reveal astonishingly unspecialised flipper attributes.
Chapter 4 Functional anatomy presents detailed descriptions of soft tissue arrangements in two dolphins (Grampus griseus, Cephalorhynchus hectori) and one porpoise (Phocoena dioptrica). These and other findings of this study are then analysed and combined with previously published accounts of the cetacean and mammalian forelimb, inclusive fossil specimens. The resulting conclusions are then presented within a phylogenetic context detailing possible locomotory adaptations of early archaeocetes and arrangements of flipper morphology in fully aquatic later archaeocetes and modern cetaceans.