The Phylogenetic Relationships and Biogeography of True Porpoises (Mammalia: Phocoenidae) Based on Morphological Data

Abstract

Prior studies of phylogenetic relationships among phocoenids based on morphology and molecular sequence data conflict and yield unresolved relationships among species. This study evaluates a comprehensive set of cranial, postcranial, and soft anatomical characters to infer interrelationships among extant species and several well‐known fossil phocoenids, using two different methods to analyze polymorphic data: polymorphic coding and frequency step matrix. Our phylogenetic results confirmed phocoenid monophyly. The division of Phocoenidae into two subfamilies previously proposed was rejected, as well as the alliance of the two extinct genera Salumiphocaena and Piscolithax with Phocoena dioptrica and Phocoenoides dalli. Extinct phocoenids are basal to all extant species. We also examined the origin and distribution of porpoises within the context of this phylogenetic framework. Phocoenid phylogeny together with available geologic evidence suggests that the early history of phocoenids was centered in the North Pacific during the middle Miocene, with subsequent dispersal into the southern hemisphere in the middle Pliocene. A cooling period in the Pleistocene allowed dispersal of the southern ancestor of Phocoena sinus into the North Pacific (Gulf of California).

Two new extinct basal phocoenids (Cetacea, Odontoceti, Delphinoidea), from the upper Miocene Koetoi Formation of Japan and their phylogenetic significance

“…Archaeophocaena and Miophocaena are very different from all other phocoenids (Barnes 1985(Barnes , 1990Muizon, 1988a;Heyning, 1989Heyning, , 1997Arnold and Heinsohn, 1996;Fajardo-Mellor et al, 2006;Lambert, 2008) by having an ascending process of the premaxilla attached to the nasal, although it should be noted that the morphology of this region could not be observed in the basal phocoenid Pterophocaena due to fragmentary nature of its holotype. Based on this character, Archaeophocaena and Miophocaena are recognized as basal phocoenids.…”

“…Their fossil record is relatively good, with 12 extinct phocoenid species having been described from late Miocene to Pliocene. Several specimens have recently been reported from the western North Pacific (Ichishima and Kimura, 2000, 2005, 2009Murakami et al, 2012) and they help fill spatial, temporal, and morphological gaps in the fossil record of Phocoenidae. On the basis of extant and extinct species, intra-familial (Muizon, 1984(Muizon, , 1988aBarnes, 1985;Fajardo-Mellor, 2006;Lambert, 2008;Murakami et al, in press) and inter-familial (Muizon, 1984(Muizon, , 1988aHeyning, 1989Heyning, , 1997; Barnes, 1990;Arnold and Heinsohn, 1996;Messenger and McGuire, 1998;Geisler and Sanders, 2003;Geisler et al, 2011;Murakami et al, in press) relationships have been assessed by morphological cladistic analyses. However, no consensus has been reached on either intraor inter-familial relationships.…”

Sexual dimorphism of Dall's porpoise and harbor porpoise skulls

“…In this study we use geometric morphometrics to examine sexual dimorphism of skull shape in the sister species pair (Rosel et al 1995;Fajardo-Mellor et al 2006;May-Collado and Agnarsson 2006) harbor porpoise (Phocoena phocoena) and Dall's porpoise (Phocoenoides dalli). The two species occupy different habitats (Read 2002), which is also reflected in their skull morphology (Galatius et al 2011) and there are indications of different mating systems.…”

Bohaskaia monodontoides, a new monodontid (Cetacea, Odontoceti, Delphinoidea) from the Pliocene of the western North Atlantic Ocean

“…Viewed dorsally, the rostrum of Bohaskaia is broad, compared to other monodontids, with laterally expanded anterior terminations of the premaxillae that dominate the apex of the rostrum, which differs from their anterior constriction in Denebola and Monodon, and the rectilinear ones of Delphinapterus. The premaxillary sac fossae of Bohaskaia are flat, like Delphinapterus, and ovate, but not raised as in Monodon, nor forming the bosses observed in phocoenids, albireonids, and the Belgian monodontid (Barnes 1984(Barnes , 2008Fajardo-Mellor et al, 2006;Lambert and Gigase 2007). The antorbital notches of Bohaskaia are L-shaped, like Pontoporia (Pyenson and Hoch 2007), whereas most other monodontids possess U-shaped ones; the Belgian monodontid approaches this condition (Lambert and Gigase 2007: fig.…”