Editing Cetacea (section)

== Baleen whales and toothed whales ==
{{More citations needed section|date=November 2019}}
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|image1=Eubalaena glacialis (North Atlantic right whale) 1 (30986325841).jpg
|caption1=Skull of the [[North Atlantic right whale]] (Mysticeti)

|image2=Orca Schaedel Senckenberg.jpg
|caption2=Skull of the [[orca]] (Odontoceti)

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The two parvorders, [[baleen whale]]s (Mysticeti) and [[toothed whale]]s (Odontoceti), are thought to have diverged around thirty-four million years ago.<ref>{{Cite journal|last1=Cerchio|first1=Salvatore|last2=Tucker|first2=Priscilla|date=1998-06-01|title=Influence of Alignment on the mtDNA Phylogeny of Cetacea: Questionable Support for a Mysticeti/Physeteroidea Clade|journal=Systematic Biology|volume=47|issue=2|pages=336–344|doi=10.1080/106351598260941|pmid=12064231|s2cid=16270218 |issn=1076-836X|doi-access=free}}</ref>

Baleen whales have bristles made of [[keratin]] instead of [[teeth]]. The bristles filter [[krill]] and other small [[invertebrate]]s from seawater. [[Grey whale]]s feed on bottom-dwelling mollusks. [[Rorqual]] [[Family (biology)|family]] (balaenopterids) use throat pleats to expand their mouths to take in food and sieve out the water.<ref>{{Citation |last=Marshall |first=Christopher D. |title=Feeding Morphology |date=2018-01-01 |encyclopedia=Encyclopedia of Marine Mammals (Third Edition) |pages=349–354 |editor-last=Würsig |editor-first=Bernd |url=https://linkinghub.elsevier.com/retrieve/pii/B9780128043271001254 |access-date=2025-02-09 |publisher=Academic Press |doi=10.1016/b978-0-12-804327-1.00125-4 |isbn=978-0-12-804327-1 |editor2-last=Thewissen |editor2-first=J. G. M. |editor3-last=Kovacs |editor3-first=Kit M.}}</ref> [[Balaenidae|Balaenids]] ([[right whales]] and [[bowhead whales]]) have massive heads that can make up 40% of their body mass. Most mysticetes prefer the food-rich colder waters of the Northern and Southern Hemispheres, migrating to the Equator to give birth. During this process, they are capable of fasting for several months, relying on their fat reserves.

The parvorder of Odontocetes – the toothed whales – include sperm whales, beaked whales, orcas, dolphins and porpoises. Generally their teeth have evolved to catch fish, squid or other [[marine invertebrates]], not for chewing them, so prey is swallowed whole. Teeth are shaped like cones (dolphins and sperm whales), spades ([[porpoise]]s), pegs ([[Beluga whale|beluga]]s), tusks ([[narwhals]]) or variable (beaked whale males). Female beaked whales' teeth are hidden in the gums and are not visible, and most male beaked whales have only two short tusks. Narwhals have vestigial teeth other than their tusk, which is present on males and 15% of females and has millions of nerves to sense water temperature, pressure and salinity. A few toothed whales, such as some [[orca]]s, feed on mammals such as [[pinnipeds]] and other whales.<ref>{{Cite news |last=Roth |first=Annie |date=2022-01-29 |title=Orcas Are Able to Kill and Eat Blue Whales, Scientists Confirm |url=https://www.nytimes.com/2022/01/29/science/orcas-blue-whales.html |access-date=2025-02-09 |work=The New York Times |language=en-US |issn=0362-4331}}</ref><ref>{{Cite web |title=BBC Two - Expedition Killer Whale - Capturing the secret lives of pack ice killer whales |url=https://www.bbc.co.uk/programmes/articles/52HKYPGNzVgK62gbtQXz3mD/capturing-the-secret-lives-of-pack-ice-killer-whales |access-date=2025-02-09 |website=BBC |language=en-GB}}</ref>

Toothed whales have well-developed senses – their eyesight and hearing are adapted for both air and water, and they have advanced [[Animal echolocation#Toothed whales|sonar capabilities]] using their [[melon (cetacean)|melon]]. Their hearing is so well-adapted for both air and water that some blind specimens can survive. Some species, such as sperm whales, are well adapted for diving to great depths. Several species of toothed whales show [[sexual dimorphism]], in which the males differ from the females, usually for purposes of sexual display or aggression.<ref>{{Citation |last1=Ralls |first1=Katherine |title=Sexual Dimorphism |date=2009-01-01 |encyclopedia=Encyclopedia of Marine Mammals (Second Edition) |pages=1005–1011 |editor-last=Perrin |editor-first=William F. |url=https://linkinghub.elsevier.com/retrieve/pii/B9780123735539002339 |access-date=2025-02-09 |place=London |publisher=Academic Press |doi=10.1016/b978-0-12-373553-9.00233-9 |isbn=978-0-12-373553-9 |last2=Mesnick |first2=Sarah |editor2-last=Würsig |editor2-first=Bernd |editor3-last=Thewissen |editor3-first=J. G. M.}}</ref>