Editing Loon (section)

==Systematics and evolution==
All living species are placed in the genus ''Gavia''. It has been suggested that the genus ''Gavia'' originated in Europe during the [[Paleogene]]. The earliest species, ''G. egeriana'', was found in [[early Miocene]] deposits in [[Dolnice]] in the Czech Republic. During the remainder of the [[Miocene]], ''Gavia'' managed to disperse into North America via the [[Atlantic]] coastlines, eventually making their way to the continent's [[Pacific]] coastlines by the [[Late Miocene]].<ref name=M98>{{Cite journal|last1=Mlíkovský|first1=Jiří|year=1998|title=A new loon (Aves: Gaviidae) from the middle Miocene of Austria|url=http://verlag.nhm-wien.ac.at/pdfs/99A_331339_Mlikovsky.pdf|journal=Annalen des Naturhistorischen Museums in Wien, Serie A|pages=331–339}}</ref> Study of the interrelationships of the extant species has found that the red-throated loons are the most basal of the five species.<ref name="Boertmann90">{{cite journal|author=Boertmann, D. |year=1990|title=Phylogeny of the divers, family Gaviidae (Aves)|journal=Steenstrupia |volume=16|pages=21–36}}</ref>
{{Cladogram|caption=Cladogram of the extant ''Gavia'' species.<ref name="Boertmann90" />
|clades=
{{clade
|1={{clade
   |1={{clade
      |1=''Gavia stellata'' }}
|2={{clade
   |1={{clade
      |1=''G. arctica''
      |2=''G. pacifica'' }}
   |2={{clade
      |1=''G. immer''
      |2=''G. adamsii'' }}
}}
}}
}}
}}

{| class="wikitable collapsible"
|-
! Lineage
! Image
! Scientific name
! Distribution
|-
!rowspan="1"  style="text-align:center;"| Basal lineage
|[[File:Red-throated Loon (Gavia stellata) - Summer plumage breeding adult2.jpg|120px]]
|[[Red-throated loon]] or red-throated diver,<br>''Gavia stellata''
|Northern hemisphere generally north of 50°, inland in summer and in coastal areas in winter as far south as Florida and southern China<ref>{{cite iucn|url=https://www.iucnredlist.org/species/22697829/131942584 |title=Red-throated Loon: ''Gavia stellata'' |author=BirdLife International |author-link=BirdLife International |year=2018 |access-date=22 March 2021 |page= e.T22697829A131942584 |doi=10.2305/IUCN.UK.2018-2.RLTS.T22697829A131942584.en}}</ref>
|-
!rowspan="2"  style="text-align:center;"| Black-throated lineage
|[[File:Gavia arctica EM1B1934 (48009481846).jpg|120px]]
|[[Black-throated loon]], Arctic loon, or black-throated diver, <br>''Gavia arctica''
|Northern Europe and Asia, breeding inland and wintering on Atlantic and Pacific coasts<ref>{{cite iucn |author=BirdLife International |date=2018 |title=''Gavia arctica'' |volume=2018 |page=e.T22697834A132606505 |doi=10.2305/IUCN.UK.2018-2.RLTS.T22697834A132606505.en |access-date=13 November 2021}}</ref>
|-
|[[File:PacificLoon24.jpg|120px]]
|[[Pacific loon]] or Pacific diver,  <br>''Gavia pacifica'' (formerly in ''G. arctica'')
|northern Canada and eastern Siberia, and winters along the Pacific coast of North America
|-
!rowspan="2"  style="text-align:center;"| Black-headed lineage
|[[File:Gavia immer (Common Loon) 1APR2017.jpg|120px]]
|[[Common loon]], or great northern diver, <br> ''Gavia immer''
|coasts and lakes of Canada and the US as far south as Mexico, and on the Atlantic coast of Europe
|-
|[[File:Yellow-billed Loon Chipp South 8-12-13 Ryan Askren.jpg|120px]]
| [[Yellow-billed loon]] or white-billed diver, <br>''Gavia adamsii''
| Russia, Canada and the United States, Mexico and Spain.
|-
|}

===Fossil record===
{{Cladogram|caption=Cladogram of the ''Gavia'' species with the inclusion of fossil species.<ref name="Olson&Rasmussen2001">{{Cite journal |last1=Olson |first1=S. L. |last2=Rasmussen |first2= P. C. |year=2001 |title=Miocene and Pliocene birds from the Lee Creek Mine, North Carolina. |journal=Smithsonian Contributions to Paleobiology |volume = 90 |issue = |pages = 233–365|doi=10.5479/si.00810266.90.233 |url=https://www.biodiversitylibrary.org/part/351988 }}</ref>
|clades=
{{clade
|1={{clade
   |1={{clade
      |1=†''Gavia egeriana''
      |2={{clade
         |1=†''G. schultzi''
         |2={{clade
            |1={{clade
               |1=†''G. howardae''
               |2=''G. stellata'' }}
            |2={{clade
               |1=†''G. brodkorbi''
               |2=†''G. paradoxa''
               |3={{clade
                  |1={{clade
                     |1=†''G. moldavica''
                     |2={{clade
                        |1=†''G. concinna''
                        |2={{clade
                           |1=''G. arctica''
                           |2=''G. pacifica'' }} }} }}
                  |2={{clade
                     |1=†''G. fortis''
                     |2={{clade
                        |1=''G. adamsii''
                        |2=''G. immer''}} }} }} }}
}}
}}
}}
}}
}}
}}

Nearly ten prehistoric species have been named to date in the genus ''Gavia'', and about as many undescribed ones await further study. The genus is known from the Early Miocene onwards, and the oldest members are rather small (some are smaller than the [[red-throated loon]]). Throughout the late [[Neogene]], the genus by and large follows [[Cope's Rule]] (that population lineages tend to increase in body size over evolutionary time). [[File:Gavia fossil Vienna.jpg|thumb|Fossil of ''[[Gavia schultzi|G. schultzi]]'' in Vienna]] 

'''List of fossil ''Gavia'' species'''
* †''[[Gavia brodkorbi|G. brodkorbi]]'' <small>Howard, 1978</small> (Late Miocene of Orange County, United States)
* †''G. concinna'' <small>[[Alexander Wetmore|Wetmore]], 1940</small> (Late Miocene/Early Pliocene of west and east United States)
* †''[[Gavia egeriana|G. egeriana]]'' <small>Švec, 1982</small> (Early Miocene of Czechoslovakia ?and Cheswold, Delaware, United States –? Yorktown Early Pliocene of Lee Creek Mine, North Carolina, United States)<ref>A small loon, smaller than ''G. howardae'': [[#Olson|Olson (1985: pp. 213–214)]], [[#Rasmussen|Rasmussen (1998)]], [[#Mlikovsky|Mlíkovský (2002: p. 63)]]</ref>
* †''[[Gavia fortis|G. fortis]]'' <small>[[Storrs Olson|Olson]] & [[Pamela C. Rasmussen|Rasmussen]], 2001</small> (Yorktown Early Pliocene of Lee Creek Mine, North Carolina, United States)<ref name="Olson&Rasmussen2001"/>
* †''[[Gavia howardae|G. howardae]]'' <small>[[Pierce Brodkorb|Brodkorb]], 1953</small> ([[San Diego Formation]], California<ref name="Brodkorb1953">{{Cite journal |last1=Brodkorb |first1=P. |year=1953 |title=A review of the Pliocene loons. |journal=The Condor |volume = 54 |issue = 4 |pages = 211–214|doi=10.2307/1364769 |jstor=1364769 }}</ref> and Yorktown Formation, North Carolina<ref name="Olson&Rasmussen2001"/>
* †''[[Gavia moldavica|G. moldavica]]'' <small>Kessler, 1984</small> (Late Miocene of Chişinău, Moldova)<ref name = milkovsky2002-64>[[#Mlikovsky|Mlíkovský (2002: p. 64)]]</ref>
* †''G. palaeodytes'' <small>Wetmore, 1943</small> (Bone Valley Early/Middle Pliocene of Pierce, Florida, United States)<ref>Known from a few limb bones. Roughly similar in size to [[Pacific loon]], but proportions seem to differ and apparently not close to any living species except maybe [[red-throated loon]]: [[#Brodkorb1953|Brodkorb (1953)]].</ref>
* †''G. paradoxa'' <small>Umanska, 1981</small> (Late Miocene of Čebotarevka, Ukraine)<ref name = milkovsky2002-64/>
* †''[[Gavia schultzi|G. schultzi]]'' <small>Mlíkovský, 1998</small> (Middle Miocene of Sankt Margarethen, Austria)<ref name=M98>{{Cite journal|last1=Mlíkovský|first1=Jiří|year=1998|title=A new loon (Aves: Gaviidae) from the middle Miocene of Austria|url=http://verlag.nhm-wien.ac.at/pdfs/99A_331339_Mlikovsky.pdf|journal=Annalen des Naturhistorischen Museums in Wien, Serie A|pages=331–339}}</ref>

'''List of fossil ''Gavia'' specimens'''
* ''Gavia'' sp. (Early-Middle Miocene of eastern United States)<ref>A tiny loon, smaller and more delicate than even the [[sympatric]] contemporary ''G. egeriana''-like birds. Probably a distinct species – [[sexual dimorphism]] in loons is not very pronounced: [[#Rasmussen|Rasmussen (1998)]].</ref>
* ''Gavia'' sp. (Calvert Middle Miocene ?or Pleistocene of Maryland, United States) – same as ''Gavia'' cf. ''immer'' below?<ref>[[USNM]] 16612, [[Anatomical terms of location#Proximal and distal|distal]] right [[tibiotarsus]]. Smaller than [[common loon]]; the polished-bone look and large size of the specimen makes a Miocene origin rather unlikely: Wetmore (1941), [[#Olson|Olson (1985: p. 214)]].</ref>
* ''Gavia'' spp. (Middle Miocene of Steinheim, Germany) – three species<ref name = milkovsky2002-64/>
* ''Gavia'' sp. (Early Pliocene of Empoli, Italy)<ref>Known from a skull very similar to the [[black-throated loon]]. Initially assigned to ''G. concinna'', but this is not very likely: [[#Mlikovsky|Mlíkovský (2002: p. 64)]], and see also at ''"Gavia" portisi''.</ref>
* ''Gavia'' sp. (Early Pliocene of Kerč Peninsula, Ukraine)<ref name=milkovsky2002-64/>
* ''Gavia'' cf. ''concinna'' (San Diego Middle/Late<ref name=":0">{{Cite web|url=https://sora.unm.edu/sites/default/files/journals/condor/v055n04/p0211-p0214.pdf|title=A REVIEW OF THE PLIOCENE LOONS|last=BRODKORB|first=PIERCE|date=July 1953|website=Searchable Ornothological Research Archive}}</ref><!-- only Late? --> Pliocene of San Diego, California, United States) – two species?<ref>Initially in part (specimens [[LACM]] 2110, 2142) assigned to ''G. concinna'', but apparently one or two undescribed smaller species, about the size of the [[Pacific loon]]: [[#Brodkorb1953|Brodkorb (1953)]], [[#Mlikovsky|Mlíkovský (2002: p. 64)]].</ref>
* ''Gavia'' sp. (Early Pleistocene of Kairy, Ukraine)<ref name=milkovsky2002-64/>
* ''Gavia'' cf. ''immer'' (Pleistocene of California and Florida, United States) – possibly a ''G. immer'' [[paleosubspecies]]<ref name=b53>[[#Brodkorb1953|Brodkorb (1953)]]</ref>

''"Gavia" portisi'' from the [[Late Pliocene]] of [[Orciano Pisano]], [[Italy]], is known from a [[cervical vertebra]] that may or may not have been from a loon. If so, it was from a bird slightly smaller than the [[common loon]]. Older authors were quite sure the bone was indeed from a ''Gavia'' and even considered ''G. concinna'' a possibly [[junior synonym]] of it. This is now regarded as rather unlikely due to the quite distinct range and age. The [[Early Pliocene]] ''Gavia'' skull from [[Empoli]] (Italy) was referred to ''G. concinna'', and thus could conceivably have been of ''"G." portisi'' if that was indeed a loon. The [[holotype]] vertebra may now be lost, which would make ''"G." portisi'' a ''[[nomen dubium]]''.<ref name=b53/><ref>[[#Brodkorb1963|Brodkorb (1963: p. 224)]], [[#Mlikovsky|Mlíkovský (2002: pp. 64, 256–57)]]</ref>