Cetacean Taxonomy and Classification Lisa T. Ballance SIO 133 Marine Mammal Biology Spring 2018 Photo credits: Robert L. Pitman
Prologue
Definitions: Taxonomy identification, naming, description, and classification of organisms A very old science Classification the arrangement of taxa into a hierarchy Systematics the study of biological diversity with emphasis on evolutionary histories among organisms* Classifications are today based on systematics *More in Cetacean Systematics & Evolution lecture
Naming System Binomial nomenclature ( two names ) Dates to Carl von Linné (1700s) Latin Genus capitalized, underlined/italicized, always a noun Species not capitalized, underlined/italicized, usually an adjective Hierarchical categorization K-P-C-O-F-G-S Super (greater than); Sub (less than); Infra (even less than Sub) The distinctions between each category and which organisms fit where is based on science, but the dividing lines can be subjective and artificial (human constructs).
A note on methods: Morphological evidence (esp. skeletal) - cornerstone of vertebrate taxonomy and classification New disciplines increasingly incorporated into T&C (e.g., genetics, acoustics) The field of molecular genetics in particular has and will continue to change our understanding due to rapidly changing technological advancements. The number of taxa (e.g., species, sub-species, families) is ever-changing.
Classifications are often hotly debated, change with time, and will continue to do so. Committee on Taxonomy. 2017. List of marine mammal species and subspecies. Society for Marine Mammalogy, www.marinemammalscience.org, consulted on 6 April 2018.
Marine Mammal Diversity ~5400 species of mammals 2.3% (~126) marine mammal species Why such low diversity?
Order Cetartiodactyla 1 Cetacea 2 : whales, dolphins, porpoises Completely independent of land skin essentially lacking hair, although present in newborns and as vibrissae in Mysticetes well-developed layer of blubber pectoral limbs modified as flippers Hyperphalangy (increased number of bones in digits) hind limbs absent pelvic girdle reduced to two free-floating bones (inominates) tail modified into flukes no external pinna nostrils modified as a blowhole skull greatly modified --telescoping Include: Baleen whales Toothed whales 1 artiodactyls and cetaceans 2 currently an unnamed clade
The Baleen Whales Suborder Mysticeti ( mustached whales ) 4 Families, 14 species no functional teeth, although approximately 50 present in fetus baleen plates to strain prey 2 external blowholes skull symmetrical vibrissae present large body size (7 33+ m in length) including the largest animals ever to live females larger than males most make long-range, seasonal migrations, summering in high latitudes and wintering in low latitudes group sizes tend to be small (1-3)
Balaenidae (right whales) 2 genera 4 species
Balaenidae Morphology no dorsal fin no gular grooves 5 digits 7 cervical vertebrae fused extremely convex profile of upper surface of skull head ~1/3 of body length Distribution all oceans except northern Indian Ocean neritic when calving; generally oceanic when feeding Ecology longest, finest baleen of all mysticetes generally slow swimmers, low maneuverability Species Eubalaena glacialis Eubalaena japonica (resurrected within past 15 years) Eubalaena australis Balaena mysticetus
Photo: J Durban/NOAA
Neobalaenidae (pygmy right whale) 1 genus 1 species
Neobalaenidae Morphology short, falcate dorsal fin one pair of shallow gular grooves moderately arched mouthline head ~1/4 of body length Distribution temperate-to-sub-polar oceans of Southern Hemisphere Ecology poorly known Species Caperea marginata
Photo: C Johnson Eschrichtiidae (gray whale) 1 genus 1 species
Eschrichtiidae Morphology dorsal hump (no dorsal fin) 2-5 gular grooves 4 digits present --first digit absent 7 cervical vertebrae --not fused upper surface of skull with slightly convex profile Distribution restricted to coastal waters of the eastern Pacific relict population present in the western Pacific North Atlantic population extirpated within last 300 hundred years Ecology short, stiff baleen (~40 cm in length) body usually covered with barnacles and whale lice slow-moving largely benthic feeders in shallow waters Species Eschrichtius robustus Western Pacific population critically endangered
Photo: J Durban/NOAA
Balaenopteridae (rorquals) 2 genera 8 species
Balaenopteridae Morphology large body size (all > 7 m in body length; include largest animals to live on earth) dorsal fin small, set behind midpoint of back numerous, lengthy gular grooves 4 digits present --third digit absent 7 cervical vertebrae --not fused upper surface of skull with flat profile Distribution all oceans of the world; all latitudes; oceanic and neritic waters Ecology baleen generally intermediate in length and thickness; minke whale with shortest baleen (~20 cm in length) generally fast swimmers, highly maneuverable Species Balaenoptera musculus Balaenoptera physalus Balaenoptera borealis Balaenoptera edeni/brydei (unresolved complex) Balaenoptera omurai (described in 2003) Balaenoptera acutorostrata Balaenoptera bonaerensis (resurrected within past 15 years) Megaptera novaeangliae
Photo: P Olson
Photo: W Perryman/NOAA
Photo: W Perryman/NOAA
Photo: J Durban/NOAA
Photo: J Durban/NOAA
10 Families, 76 species (-1) homodont teeth present (can be buried in gum/jawbone) 1 external blowhole skull asymmetrical complex system of nasal sacs fatty melon in head capable of echolocation small-to-medium body size (male sperm whales excepted) most species sexually dimorphic The Toothed Whales - Suborder Odontoceti
Physeteridae (sperm whale) Photo: Google Images 1 genus 1 species
Physeteridae Morphology dorsal hump (no dorsal fin) conical teeth confined to lower jaw; fit into sockets in upper jaw flukes notched head extends beyond lower jaw extreme cranial asymmetry blowhole at left, anterior section of head largest odontocete highest degree of sexual dimorphism of all cetaceans (males larger than females) Distribution all oceans of the world; all latitudes; mainly oceanic males occur in polar regions; females and immatures largely restricted to tropical and temperate regions Ecology and Behavior capable of dives to extreme depth (2000+ m) and length (> 2 h) mainly squid eaters genetically-related groups (matrilines) believed to remain together for life Species Physeter macrocephalus
Kogiidae (pygmy & dwarf sperm whales) 1 genus 2 species
Kogiidae Morphology dorsal fin present extreme cranial asymmetry unique pigmentation mark on lateral sides of head/neck blunt head underslung jaw Distribution oceanic waters in tropical to temperate regions, all oceans of the world Ecology and Behavior capable of deep dives mainly squid eaters small group sizes (typically < 5) poorly known Species Kogia breviceps Kogia sima
Ziphiidae (beaked whales) 6 genera 22 species Photo: D Claridge
Ziphiidae Morphology small dorsal fin set far back on body 2 gular grooves teeth: 1-2 pairs, confined to lower jaw of males (exceptions: Berardius males and females w/ 2 pairs of exposed teeth; Tasmacetus both sexes with long rows of functional teeth in upper and lower jaws) flukes without notch small flippers; fit into grooves on sides of body jaws extend beyond head into a distinct beak medium body size (4-13 m in length) females usually larger than males Distribution oceanic waters of all oceans, all latitudes Ecology and Behavior capable of dives extreme in depth and length mainly squid eaters Mesoplodon with small group sizes (<5); other genera with larger group sizes poorly known
Ziphiidae Species Berardius bairdii Berardius arnuxii Ziphius cavirostris Hyperoodon ampullatus Hyperoodon planifrons Tasmacetus shepherdi (first identified in the wild in early 2000s) Mesoplodon densirostris Mesoplodon grayi Mesoplodon ginkgodens (known only from stranded specimens) Mesoplodon hectori Mesoplodon perrini (described in 2002; known only from stranded specimens) Mesoplodon carlhubbsi Mesoplodon peruvianus (described in 1991) Mesoplodon bidens Mesoplodon europaeus Mesoplodon mirus Mesoplodon layardii Mesoplodon bowdoini (known only from stranded specimens) Mesoplodon stejnegeri Mesoplodon traversii (resurrected within past 15 years; known only from stranded specimens) Indopacetus pacficus (first identified in the wild in 1990s) Mesoplodon hotaula (described in 2013)
Photo: J Durban
The River Dolphins 4 families*, 4 genera*, 4 species* *1 declared extinct in 2007
River Dolphins (4 Families) Features common due to convergence Morphology dorsal fin usually low and sub-triangular no gular grooves teeth well developed, conical, present in both jaws extremely long beak poor vision in riverine forms heavy reliance on echolocation flukes notched Ecology and Behavior feed mainly on fish small group sizes poorly known
River Dolphins FAMILY PLATANISTIDAE South Asian river dolphin (1 genus, 1 species) distribution restricted to large river systems of South Asia (mainly Ganges and Indus) Species Platanista gangetica FAMILY INIIDAE boto (1 genus, 1 species) distribution restricted to Amazon and Orinoco rivers and drainages, South America distinct pink coloration Species Inia geoffrensis FAMILY LIPOTIDAE baiji (1 genus, 1 species) distribution restricted to Yangtze River declared extinct in 2007 (Turvey et al. 2007. Biology Letters) Species Lipotes vexillifer FAMILY PONTOPORIIDAE franciscana (1 genus, 1 species) distribution restricted to coastal waters of southeast South America Species Pontoporia blainvillei
Monodontidae (narwhal & beluga) Photo: K Laidre 2 genera 2 species
Monodontidae Morphology cervical vertebrae generally not fused no dorsal fin no gular grooves teeth narwhal --2 in upper jaw of males only left canine spirals left to become tusk beluga --8-10 in upper jaw flukes notched head blunt --no distinct beak body size < 6 m Distribution restricted to polar seas in Northern Hemisphere Ecology and Behavior group sizes generally < 10 but can number in the 1000s diet diverse Species Monodon monoceros Delphinapterus leucas
Delphinidae (dolphins) 17 genera 37 species
Delphinidae Morphology dorsal fin of various sizes and shapes, with exception of Lissodelphis (no dorsal fin) no gular grooves teeth well-developed, conical, present in both jaws flukes notched jaws extend beyond head into a distinct beak (exceptions exist) body size small to medium (~2 10 m in length) Distribution all oceans of the world; neritic and oceanic; all latitudes Ecology and Behavior highly diverse w/r/t diet often occurs in large schools
Delphinidae - species Orcaella brevirostris Orcaella heinsohni (described in 2005) Orcinus orca (new species expected) Globicephala melas Lagenorhynchus obliquidens Lagenorhynchus obscurus Lagenorhynchus albirostris Lagenorhynchus acutus Lagenorhynchus cruciger Lagenorhynchus australis Grampus griseus Tursiops truncatus Tursiops aduncus Stenella attenuata Stenella frontalis Stenella longirostris Stenella clymene (resurrected within past 20 years) Stenella coeruleoalba Delphinus delphis Globicephala macrorhynchus Pseudorca crassidens Feresa attenuata Peponocephala electra Sotalia fluviatilis Sotalia guianensis (resurrected within past 15 years) Sousa chinensis Sousa teuszii Sousa plumbea Sousa sahulensis (described in 2014) Steno bredanensis Lagenodelphis hosei (first identified in the wild in 1970s) Lissodelphis borealis Lissodelphis peronii Cephalorhynchus commersonii Cephalorhynchus heavisidii Cephalorhynchus hectori Cephalorhynchus eutropia
Photo: C Johnson
Photo: D Frank
Photo: Wildlife Conservation Society
Photo: P Wade
Photo: C Stinchcomb
Photo: J. Totterdell
Photo: O Carlsson
Photo: J. Durban/NOAA
Phocoenidae (porpoises) 3 genera 7 species
Morphology dorsal fin large and triangular, with exception of Neophocaena (no dorsal fin) no gular grooves teeth well to poorly developed, spatulate, present in both jaws flukes notched head blunt with no distinct beak small body size (all < 2.5 m in length) females larger than males in some species (but males larger in P. dioptrica and Ph. dalli) Distribution all oceans of the world; often neritic with restricted ranges but some oceanic species; one riverine form; all latitudes except polar Ecology and Behavior highly diverse w/r/t diet group sizes typically small (< 5) Phocoenidae Species Phocoenoides dalli Phocoena phocoena Phocoena dioptrica Phocoena spinipinnis Phocoena sinus (world s most critically endangered cetacean) Neophocaena phocaenoides Neophocaena asiaeorientalis
Reading Pp. 65-68; 71-81 in: Berta, A., J.L. Sumich, K.M. Kovacs. Marine Mammals.