scientificillustration:“A phylogenetic blueprint for a modern whale (Balaenoptera musculus).
scientificillustration: “A phylogenetic blueprint for a modern whale (Balaenoptera musculus). The topology traces the inferred evolutionary history of an extant cetacean based on results summarized in Figs. 7–9 and Table 1. Changes extend back to the base of Artiodactyla (A–D). The long sequence of character transformations on the stem lineage to crown Cetacea (branches E–O), on the stem lineage to crown Mysticeti (branches a–f), and within crown Mysticeti (branches g–h) has culminated in the extant blue whale. A subset of the changes on these internal branches (Table 1) are marked by colored circles that indicate the internode where each character evolved and, when applicable, the approximate anatomical position of each derived character state (delayed transformation optimization): B-1 = three primary lung bronchi and multi-chambered stomach, B-2 = fibro-elastic penis with sparse cavernous tissue, C-1 = sparse hair, sebaceous glands absent, and transition to freshwater, C-2 = scrotum absent, can give birth underwater, and can nurse underwater, D = involucrum (thickening of medial wall of auditory bulla), E = robust tail, F–G = transition to saltwater, G = incisive foramina absent and vomeronasal organ inferred absent, H = short cervical (neck) vertebrae, K = posterior positioning of nasal aperture, L = no articulation between vertebrae and pelvis (sacroiliac joint absent), M1 = very short hindlimbs, M2 = tail flukes inferred present, O-1 = external ears absent, O-2 = immobile elbow joint, O-3 = sweat glands absent, a = broad rostrum, b = thin lateral margins of maxillae, c-1 = lateral nutrient foramina on palate and baleen inferred present, c-2 = unsutured mandibular symphysis, d = no teeth in adults, e-1 = telescoping of skull (anterior extension of occipital shield), e-2 = bowed mandibles, g-1 = fibrous temporomandibular joint, g-2 = muscle of tongue reduced (predominantly connective tissue) and ventral throat pouch with numerous grooves, h = enormous body size. Branch lengths are not proportional to time. Artwork is by Carl Buell. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)” A phylogenetic blueprint for a modern whale. Gatesy J, Geisler JH, Chang J, Buell C, Berta A, Meredith RW, Springer MS, McGowen MR. Mol Phylogenet Evol. 2012 Oct 26. pii: S1055-7903(12)00418-6. doi: 10.1016/j.ympev.2012.10.012. (pdf) -- source link
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