Empeirodytes
| Empeirodytes Temporal range:Oligocene
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Scientific classification
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Suliformes |
| Family: | †Plotopteridae |
| Genus: | †Empeirodytes Ohashi & Hasegawa, 2020 |
| Type species | |
| Empeirodytes okazakii Ohashi & Hasegawa, 2020
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Empeirodytesis anextinctgenusofPlotopteridae,a family of largeflightless birdknown from theLate Eoceneto theEarly Mioceneof theWest Coast of the United States,British ColumbiaandJapan.Remains associated withEmpeirodyteshave been found inOligocenerocks of theAshiya Group,on the islands ofAinoshimaandKaijima,nearKitakyushu,Japan.[1]
History and Etymology
[edit]In 2020,Ohashi TomoyukiandHasegawa Yoshikazufirst described the remains ofEmpeirodytes okazakii,assigning asholotypeKMNH VP 600011,a partial leftcoracoidfound inOligocene-aged rocks of theAshiya Groupon the island ofAinoshima,Japan.They referred asparatypea right coracoid from the same horizon, discovered on the nearbyKaijima.[1]
Etymology
[edit]The genus name,Empeirodytes,is formed from theGreekprefix "Empeiros",meaning" proficient ", and the suffix" -dytes",meaning" diver ", referencing the adaptation towards wing-propelled diving exhibited by plotopterids.[1]
The species name, "okazakii",honoursOkazaki Yoshihiro,anothervertebrateresearcher who worked onfossilsfrom the Ashiya Group.[1]
Description
[edit]The genusEmpeirodytesis only known from two isolatedcoracoids.It is assumed from the size of those remains that the bird was a medium-sized plotopterid, smaller than the large genera of Japanese tonsalin plotopteridsCopepteryxandHokkaidornis,but larger than the derivedPlotopterum.Empeirodytesis mostly differentiated from other genera of plotopterids by the presence of a high and sharp ridge on the caudal margin of the labrum internum, and of a clear depression on the ventral surface of the portion where the shaft of the coracoid articulates with thehumerus.The presence of that depression may indicate the attachment of thesupracoracoideus muscle,used by plotopterids to propel themselves through water, potentially indicating thatEmpeirodytesand its relativeStenornishad better swimming abilities than most other plotopterids.[1]
Palaeobiology
[edit]During theOligocene,the sea that composes today theYamaga Formationand theJinnobaru Formationof theAshiya Groupwas home to at least four species of plotopterids, the medium-sizedEmpeirodytes,the large-sizedStenornis kanmonensisandCopepteryx hexeris,and the giantCopepteryx titan.Alongside these, those waters were also populated by theeomysticetidwhaleYamatocetus,sharks andpelagornithidseabirds.[1]
References
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