Editing Seabird (section)

== Creation and structure ==
Seabirds, by virtue of living in a [[geology|geologically]] depositional environment (that is, in the sea where [[sediment]]s are readily laid down), are well represented in the [[fossil]] record.<ref name="Burger" /> They are first known to occur in the [[Cretaceous]] period, the earliest being the [[Hesperornithes]]. These were flightless seabirds that could dive in a fashion similar to grebes and loons (using its feet to move underwater),<ref>{{cite journal |last1=Bell |first1=Alyssa |last2=Chiappe |first2=Luis M. |date=2022-04-01 |title=The Hesperornithiformes: A Review of the Diversity, Distribution, and Ecology of the Earliest Diving Birds |journal=Diversity |volume=14 |issue=4 |article-number=267 |doi=10.3309/d14040267 |url=https://www.mdpi.com/1424-2818/14/4/267}}</ref> but had beaks filled with sharp teeth.<ref>{{cite journal |last=Gregory | first=Joseph T. |year=1952|title=The jaws of the Cretaceous toothed birds, ''Ichthyornis'' and ''Hesperornis'' |journal=Condor |volume=54 |issue=2 | pages=73–88 |url=http://sora.unm.edu/sites/default/files/journals/condor/v054n02/p0073-p0088.pdf|doi=10.2307/1364594|jstor=1364594}}</ref> Other Cretaceous seabirds included the gull-like [[Ichthyornithes]].<ref>{{Cite journal |last1=Lowi-Merri |first1=Talia M. |last2=Demuth |first2=Oliver E. |last3=Benito |first3=Juan |last4=Field |first4=Daniel J. |last5=Benson |first5=Roger B.J. |last6=Claramunt |first6=Santiago |last7=Evans |first7=David C. |date=2023-03-08 |title=Reconstructing locomotor ecology of extinct avialans: a case study of ''Ichthyornis'' comparing sternum morphology and skeletal proportions |journal=Proceedings of the Royal Society B |volume=209 |issue=1994 |article-number=20222020 |doi=10.1098/rspb.2022.2020 |url=https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2022.2020|pmc=9993061 }}</ref> Flying Cretaceous seabirds do not exceed wingspans of two meters; piscivorous [[pterosaur]]s occupied seagoing niches above this size.<ref>{{Cite journal | last1=Longrich | first1=N. R. | last2=Martill | first2=D. M. | last3=Andres | first3=B. | date=2018 | title=Late Maastrichtian pterosaurs from North Africa and mass extinction of Pterosauria at the Cretaceous-Paleogene boundary | journal=PLOS Biology | volume=16 | issue=3 | pages=e2001663 | doi=10.1371/journal.pbio.2001663 | pmid=29534059 | pmc=5849296 | doi-access=free}}</ref>

[[File:Hesperornis.jpeg|thumb|right|alt=skull of ancient seabird with teeth set into bill|The Cretaceous seabird ''Hesperornis'']]

While ''Hesperornis'' is not thought to have left descendants, the earliest [[Neornithes|modern]] seabirds also occurred in the Cretaceous, with a species called ''[[Tytthostonyx|Tytthostonyx glauconiticus]]'', which has features suggestive of Procellariiformes and Fregatidae.<ref name=olson1987>Olson, S.; Parris, D.C. (1987). "[https://repository.si.edu/bitstream/handle/10088/1985/SCtP-0063-Lo_res.pdf?sequence=2&isAllowed=y#page=22 The Cretaceous Birds of New Jersey.]" ''Smithsonian Contributions to Paleontology'', '''63''': 22pp.</ref> As a clade, the Aequornithes either became seabirds in a single transition in the Cretaceous or some lineages such as pelicans and frigatebirds adapted to sea living independently from freshwater-dwelling ancestors.<ref name="Vermeij2018">{{cite journal |last1=Vermeij |first1=Geerat | first2=Ryosuke | last2=Motani |title=Land to sea transitions in vertebrates: The dynamics of colonization |journal=Paleobiology |date=2018 |volume=44 |issue=2 |pages=237–250 |doi=10.1017/pab.2017.37|bibcode=2018Pbio...44..237V |s2cid=91116726 }}</ref> In the [[Paleogene]] both pterosaurs and marine reptiles became extinct, allowing seabirds to expand ecologically. These post-extinction seas were dominated by early [[Procellariidae]], giant [[penguin]]s and two [[extinct]] [[family (biology)|families]], the [[Pelagornithidae]] and the [[Plotopteridae]] (a group of large seabirds that looked like the penguins).<ref>{{cite journal|last=Goedert | first=James L. |year=1989|title=Giant late Eocene marine birds (Pelecaniformes: Pelagornithidae) from northwestern Oregon|jstor=1305659|journal=Journal of Paleontology |volume=63 |issue=6|pages= 939–944|doi=10.1017/S0022336000036647| bibcode=1989JPal...63..939G | s2cid=132978790 }}</ref> Modern genera began their wide radiation in the [[Miocene]], although the [[genus]] ''[[Puffinus]]'' (which includes today's [[Manx shearwater]] and [[sooty shearwater]]) might date back to the [[Oligocene]].<ref name="Burger" /> Within the Charadriiformes, the gulls and allies ([[Lari (bird)|Lari]]) became seabirds in the late Eocene, and then waders in the middle Miocene ([[Langhian]]).<ref name="Vermeij2018"/> The highest diversity of seabirds apparently existed during the Late Miocene and the [[Pliocene]]. At the end of the latter, the oceanic [[food web]] had undergone a period of upheaval due to extinction of considerable numbers of marine species; subsequently, the spread of marine mammals seems to have prevented seabirds from reaching their erstwhile diversity.<ref>{{cite journal|author1=Olson, S.  |author2=Hasegawa, Y.  |year=1979|title=Fossil counterparts of giant penguins from the north Pacific|journal=Science |volume=206 |issue=4419 |pages= 688–689|doi=10.1126/science.206.4419.688 |pmid=17796934|bibcode=1979Sci...206..688O  |s2cid=12404154 }}</ref>{{Update inline|date=April 2021|reason=Apparently conveys uncertainty, which may have been resolved}}