Tara Whitty 11 1 2007 SIO 277 Midterm Paper 1 Building on a Skeletal Framework Understanding the Taxonomy Biology and Future of the Beaked Whales The beaked whales family Ziphiidae are one of the least understood groups of mammals Identification and classification of ziphiids at the time of the Challenger Expedition relied on osteological examinations predictably leading to uncertainty Over the next 130 years research has focused on identification and taxonomy Even in the past 10 years new species have been identified while incorrectly assigned species names have been corrected From the 1950s onward there has been an increasing focus on other aspects of beaked whale biology However our understanding of these enigmatic marine mammals remains limited several species have still never been observed alive and most are known from fewer than 50 specimens MacLeod and Mitchell 2005 The Challenger Expedition Working Through Redundancy Around the time of the Challenger expedition in the mid to late 1800s there was a frenzy of beaked whale identifications including 9 currently recognized species Due to the difficulty of identifying specimens based on skeletal remains as well as lack of coordination among naturalists several redundant species names were also created Reeves et al 2002 This milieu is reflected in the Challenger report on cetaceans by Turner Turner 1881 On the expedition naturalists collected four partial beaked whale skeletons from previous strandings Turner identifies three of the specimens through osteological examination as Mesoplodon layardii He describes the past misidentification of M layardii specimens including the names Dolichodon layardii M longirostris M guntheri Callidon guntheri and M floweri Based on the record of strandings Turner gathers that M layardii had an extensive geographic range in the southern hemisphere The fourth Challenger specimen had been identified as Epiodon chathamiensis though naturalist Dr Hector believed that this specimen was identical to the previously described E australis and possibly also to Petrorhynchus capensis Turner argues that these three species plus Ziphius indicus are in fact Ziphius cavirostris He describes the related debate among the naturalist community concerning this identification though at the time it appeared that a consensus was forthcoming From Bones to Genes Identifying Species and Relationships Since the Challenger expedition the main focus of beaked whale research has been the reconciliation of misidentified species with correct names as well as identification of new species Morphological examination was and remains an important tool in identification but many morphological features differ among age and sex classes and can be very similar across species leading to uncertainty in identification Besharse 1971 Dalebout et al 2004 The emergence of genetic analysis as a tool for identification has helped resolve taxanomic confusion Currently 21 species of Ziphiids are recognized assigned to 6 genera Ziphius Mesoplodon Hyperoodon Beradius Indopacetus and Tasmacetus It turns out that Turner was correct in his arguments about Z cavirostris Several of the older species and genera names are no longer recognized such as the genera Dolichodon Callidon Epiodon and Petrorhynchus mentioned in the Challenger report Pre 1990s Methods for species identification remained similar to those used in the time of the Challenger with 9 new species identified through osteological and morphological examination between the publication of the Challenger report and 1990 Radcliffe 1913 Oliver 1937 Moore and Gilmore 1965 Reeves et al 2002 Identifications were confirmed or overturned through reexamination of bones or photographs similar to the Tara Whitty 11 1 2007 SIO 277 Midterm Paper 2 situation described by Turner with Epiodon Rhoads 1902 Orr 1953 McCann 1964 The most important work in identifying relationships within Ziphiidae came in 1968 when Moore used osteological examination of skulls from the 18 recognized species at the time to assign genera to tribes and identify a new genus Indopacetus Moore 1968 1990s Onward Though morphological cues continue to be important genetic analysis has helped confirm identification and define relationships Two new species have been identified since 1990 one of them through mtDNA analysis Reyes et al 1991 Reeves et al 2002 and confusion over incorrect identifications continues to be resolved Henshaw et al 1997 Gomercic et al 2006 Van Helden et al 2002 Phylogenetic analysis of mtDNA has confirmed the genetic distinctiveness of all of the 21 currently recognized species Dalebout et al 2004 and mtDNA diversity within genera and species have identified phylogeographic structure among Z cavirostris and the genus Mesoplodon Dalebout et al 2005 Dalebout et al 2007 DNA reference sequences for all 21 species are now available on a web based program DNA Surveillance Dalebout et al 2007 Thus far the groupings proposed by Moore in 1968 appear to hold Stomach anatomy has even been explored as a method of defining relationships between beaked whales with three principal groups defined based on stomach type Mead 2007 Lambert 2005 has also examined the relationship between fossil beaked whales and extant species The phylogenetic placement of ziphiids within Cetacea whales remains uncertain even with molecular data Milinkovitch et al 1994 The progress made in identification is highlighted by two tales of mysterious beaked whales Almost 40 years after Moore 1968 identified the genus Indopacetus which had never been seen alive fresh strandings were linked to that genus through morphological examinations and mtDNA analysis The strandings matched an unidentified tropical bottlenose whale that had been seen at sea mystifying researchers for years and which is now known as I pacificus Dalebout et al 2003 Another unidentified species known from sightings at sea was described as Mesoplodon species A Pitman et al 1987 Since the original sightings two new Mesoplodon species in the same region were described M peruvianus and M bahamondi Reexamination of measurements and photographs of M sp A confirmed that is was M peruvianus Pitman and Lynn 2001 M bahamondi was later found through mtDNA analysis to be a synonym for the previously identified M traversii Van Helden et al 2002 Other Aspects of Ziphiid Biology Due to the difficulty of studying the shy and elusive beaked whales several aspects of their biology remain poorly understood A