Origin of Whales from Early Artiodactyls: Hands and Feet of Eocene Protocetidae from Pakistan

Department of Geological Sciences and Museum of Paleontology, The University of Michigan, Ann Arbor, MI 48109-1079, USA.
Science (Impact Factor: 33.61). 10/2001; 293(5538):2239-42. DOI: 10.1126/science.1063902
Source: PubMed


Partial skeletons of two new fossil whales, Artiocetus clavis and Rodhocetus balochistanensis, are among the oldest known protocetid archaeocetes. These came from early Lutetian age (47 million years ago) strata in
eastern Balochistan Province, Pakistan. Both have an astragalus and cuboid in the ankle with characteristics diagnostic of
artiodactyls; R. balochistanensis has virtually complete fore- and hind limbs. The new skeletons are important in augmenting the diversity of early Protocetidae,
clarifying that Cetacea evolved from early Artiodactyla rather than Mesonychia and showing how early protocetids swam.

Download full-text


Available from: Iyad S. Zalmout
  • Source
    • "However, the utility of detailed morphological information in such research has become increasingly questioned (see Springer et al. [2013] comment on O'Leary et al. [2013a, b]). Therefore, we emphasize that patterns of phenotypic variation (including morphology) among biological structures form the basis for understanding gene function (e.g., Morgan, 1911; Abzhanov et al., 2006), developmental mechanisms (e.g., Harjunmaa et al., 2012), ecological adaptation (e.g., Losos, 1990; Frost et al., 2003), and evolutionary history (e.g., Leakey et al., 1964; Ostrom, 1975; Gingerich et al., 2001). Given its importance in a diverse set of biological disciplines, we believe that morphological information remains highly relevant to scientific discovery and advancement. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Three-dimensional geometric morphometric (3DGM) methods for placing landmarks on digitized bones have become increasingly sophisticated in the last 20 years, including greater degrees of automation. One aspect shared by all 3DGM methods is that the researcher must designate initial landmarks. Thus, researcher interpretations of homology and correspondence are required for and influence representations of shape. We present an algorithm allowing fully automatic placement of correspondence points on samples of 3D digital models representing bones of different individuals/species, which can then be input into standard 3DGM software and analyzed with dimension reduction techniques. We test this algorithm against several samples, primarily a dataset of 106 primate calcanei represented by 1,024 correspondence points per bone. Results of our automated analysis of these samples are compared to a published study using a traditional 3DGM approach with 27 landmarks on each bone. Data were analyzed with morphologika(2.5) and PAST. Our analyses returned strong correlations between principal component scores, similar variance partitioning among components, and similarities between the shape spaces generated by the automatic and traditional methods. While cluster analyses of both automatically generated and traditional datasets produced broadly similar patterns, there were also differences. Overall these results suggest to us that automatic quantifications can lead to shape spaces that are as meaningful as those based on observer landmarks, thereby presenting potential to save time in data collection, increase completeness of morphological quantification, eliminate observer error, and allow comparisons of shape diversity between different types of bones. We provide an R package for implementing this analysis. Anat Rec, 298:249-276, 2015. © 2014 Wiley Periodicals, Inc. © 2014 Wiley Periodicals, Inc.
    Full-text · Article · Jan 2015 · The Anatomical Record Advances in Integrative Anatomy and Evolutionary Biology
  • Source
    • "Like other marine tetrapods, cetaceans are descended from terrestrial ancestors, although for most of the nineteenth and twentieth centuries, the fossil record did not provide much illumination on the deeper relationships between cetaceans and other mammals or their dramatic morphological disparity (Gingerich, 2005). Paleontological work in the past 30 years has vastly improved this situation, providing conclusive evidence for the artiodactyl ancestry of cetaceans (Gingerich et al., 2001; Thewissen et al., 2001) and the sequence of morphological transformations that accompanied the ecological transition from a semi-aquatic lifestyle to an obligate aquatic existence (Thewissen and Williams, 2002; Gingerich, 2003; Thewissen et al., 2007; Gingerich et al., 2009). However , the so-called " land to sea " transition in early cetaceans accounts for Palaeogeography, Palaeoclimatology, Palaeoecology 400 (2014) 1–8 ⁎ Corresponding author. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The dominant consumers in today’s ocean ecosystems are marine mammals, including cetaceans, sirenians, and pinnipeds, and other marine carnivorans. The ecological dominance of marine mammals can be traced back to at least seven independent transitions during the Cenozoic, when different lineages of terrestrial mammals underwent land to sea evolutionary transformations. However, the evolution of marine mammals represents only the most recent set of marine invasions by tetrapods over the past 250 million years. During the Mesozoic, over a dozen different reptile lineages (e.g., mosasaurs, ichthyosaurs, turtles, snakes) evolved obligate marine lineages, including a few lineages that persist to today, such as sea turtles. Birds, which are phylogenetically nested among diapsid reptiles, have also repeatedly adapted to marine life since the Cretaceous. Attempts to understand the common patterns of marine tetrapod evolution, and the processes that have shaped them, have largely been limited to individual groups. Placed in a broad comparative view from the Mesozoic to the Cenozoic eras, the macroevolution of marine tetrapods reveals evolutionary drivers at different scales, along with morphological parallels, unique evolutionary innovations, and the strong influence of historical constraints. Major physical, environmental drivers appear to be responsible for some patterns in marine tetrapod evolution at some temporal and geographic scales, but these drivers are not unique causes, as biological drivers (e.g., escalation) likely also play a role. The culmination of this trophic ascendancy has been dramatically altered by human hunting (especially of marine mammals), underscoring the need for historical datasets that extend into deep time to understand the ecological history of marine tetrapods.
    Full-text · Article · Apr 2014 · Palaeogeography Palaeoclimatology Palaeoecology
  • Source
    • "Ancestors of Artiodactyla and Cetacea are unknown. Cetacea were considered to descend from Cretaceous Eutheria (Simpson, 1945; Dechaseaux, 1961; Mchedlidze, 1970) or later groups, i.e., Mesoo nychia (Van Valen, 1966; Luo and Gingerich, 1999), Artiodactyla (Gingerich et al., 2001; Rose, 2001; Geii sler et al., 2007), Suiformes of the family Raoellidae (Thewissen et al., 2009), or an extinct artiodactyl taxon similar to the extant African traguline genus Hyemoschus (Thewissen et al., 2009). The origin of the order Artiodactyla was thought to be connected with Cretaceous Eutheria (Kowalevsky, 1873–1874, 1875; Novacek, 1986, 1992; Prothero, 1993; Janis et al., 1998; Vislobokova, 1998, 2001; Vislobokova, Trofii mov, 2002), archaic Condylarthra or Arctocyonidae ungulates (Van Valen, 1966), or a taxon close to Unguu latomorpha (Nessov et al., 1998). "
    [Show abstract] [Hide abstract]
    ABSTRACT: The analysis of biodiversity and ecological evolution of Eocene Cetartiodactyla against the background of changes in the biosphere, biota, and paleogeography has provided a model for the origin, development, and dispersal of this group. The main trends in ecogenesis, occurrence data, relationships between the main evolutionary events and great abiotic and biotic events are considered and the possibility of Cretaceous origin of Cetartiodactyla is corroborated. Cetartiodactyla could have arise in the Late Cretaceous in Asia south of 30°–40° N or in the southern Indochina Peninsula; they diverged very early into Cetacea and Artiodactyla. The model proposed confirms monophyly of Cetartiodactyla, Artiodactyla, and Cetacea. The existence of a missing initial link explains considerable changes in the Archaeoceti structure (in particular, dentition), as compared to that of Artiodactyla. Eocene Artiodactyla were closer in ecology to the initial type of Cretaceous Eutheria.
    Full-text · Article · Sep 2013 · Paleontological Journal
Show more