Eschrichtiidae: Difference between revisions

Latest revision as of 07:37, 27 January 2025

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Eschrichtiidae or the gray whales is a family of baleen whale (Parvorder Mysticeti) with a single extant species, the gray whale (Eschrichtius robustus), as well as four described fossil genera: Archaeschrichtius (Miocene), Glaucobalaena and Eschrichtioides (Pliocene) from Italy,<ref>Template:Harvnb</ref><ref>Template:Cite journal</ref> and Gricetoides from the Pliocene of North Carolina.<ref>Template:Harvnb</ref> Some phylogenetic studies have found this family to be invalid, with its members nesting inside of the clade Balaenopteridae.<ref name=":0">Template:Cite journal</ref><ref name=":1">Template:Cite web</ref> The names of the extant genus and the family honours Danish zoologist Daniel Eschricht.<ref>Template:Harvnb</ref>

Taxonomy

In his morphological analysis, Template:Harvnb found that eschrichtiids and Cetotheriidae (Cetotherium, Mixocetus and Metopocetus) form a monophyletic sister group of Balaenopteridae.<ref>Template:Harvnb</ref>

A specimen from the Late Pliocene of Northern Italy, named "Cetotherium" gastaldii by Template:Harvnb<ref>Template:Harvnb</ref> and renamed "Balaenoptera" gastaldii by Template:Harvnb, was identified as a basal eschrichtiid by Template:Harvnb who recombined it to Eschrichtioides gastaldii.<ref name="PyeLin-fossils">Template:Harvnb</ref><ref>Template:Harvnb</ref>

Template:Harvnb found that the gray whale is phylogenetically distinct from rorquals and that previous morphological studies were correct in the conclusion that the evolution of gulp feeding was a single event in the rorqual lineage.<ref>Template:Harvnb</ref> In contrast, multiple later studies found the gray whale to fall within the family Balaenopteridae, being more derived than the minke whales but basal to all other members in the family, and reclassified it in Balaenopteridae; the American Society of Mammalogists has followed this classification.<ref name=":0" /><ref name=":1" /><ref>Template:Cite journal</ref>

Evolution

Fossils of Eschrichtiidae have been found in all major oceanic basins in the Northern Hemisphere, and the family is believed το date back to the Late Miocene.<ref name="PyeLin-fossils" /> Today, gray whales are only present in the northern Pacific, but a population was also present in the northern Atlantic before being driven to extinction by European whalers three centuries ago.<ref>Template:Harvnb</ref>

Fossil eschrichtiids from before the Holocene are rare compared to other fossil mysticetes. The only Pleistocene fossil from the Pacific referred to E. eschrichtius is a partial skeleton and an associated skull from California, estimated to be about 200 thousand years old. However, a late Pliocene fossil from Hokkaido, Japan, referred to Eschrichtius sp. is estimated to be Template:Mya and a similar unnamed fossil has been reported from California.<ref name="PyeLin-fossils" />

In their description of Archaeschrichtius ruggieroi from the late Miocene of Italy, Template:Harvnb argued that eschrichtiids most likely originated in the Mediterranean Basin about Template:Mya and remained there, either permanently or intermittently, at least until the Early Pliocene (5–3 Mya),<ref>Template:Harvnb</ref> (but see Messinian salinity crisis.)

References

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External links

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