Potamotherium
{{Short description|Extinct genus of mammals}}
{{Automatic taxobox
| fossil_range = {{Fossil range|23.03|11.1}} Aquitanian - Tortonian
| image = Potamotherium valetoni skeleton.jpg
| image_caption = P. valletoni skeleton
| taxon = Potamotherium
| authority = Geoffroy, 1833
| subdivision_ranks = Species
| subdivision =
- P. valletoni (Geoffroy, 1833) (type)
- P. miocenicum (Peters, 1868)
}}
Potamotherium ('river beast') an extinct genus of caniform carnivoran from the Miocene epoch of France and Germany. It has historically been assigned to the family Mustelidae (otters, weasels, etc.), but more recent studies suggest that it represents a primitive relative of pinnipeds (seals, sea lions, etc.)
Classification
The genus was first described in 1833. Carroll (1988) assigned it to the family Mustelidae as a member of the subfamily Oligobuninae. However, it was recently suggested that Potamotherium was not a mustelid at all, but rather a very basal pinniped.{{cite web
| url = http://blogs.discovermagazine.com/notrocketscience/2009/04/22/puijila-the-walking-seal-a-beautiful-transitional-fossil/#.UofLgtK-2So
| title = Puijila, the walking seal – a beautiful transitional fossil
| author = Ed Yong
| author-link = Ed Yong
| date = 2009-04-22
| website = Not Exactly Rocket Science
| publisher = Discover Magazine
| archive-url = https://web.archive.org/web/20121103174758/http://blogs.discovermagazine.com/notrocketscience/2009/04/22/puijila-the-walking-seal-a-beautiful-transitional-fossil/
| archive-date = 3 November 2012
| url-status = live
| access-date = 2014-10-07}}{{cite journal
|author1=Natalia Rybczynski |author2=Mary R. Dawson |author3=Richard H. Tedford | title=A semi-aquatic Arctic mammalian carnivore from the Miocene epoch and origin of Pinnipedia
| journal=Nature
| year=2009
| volume=458
| issue=7241
| pages=1021–1024
| bibcode=2009Natur.458.1021R
| doi=10.1038/nature07985
| pmid=19396145|s2cid=4371413 }} Berta et al. (2018) placed Potamotherium along with Puijila and Semantor in the family Semantoridae.Berta, A., Churchill, M., & Boessenecker, R.W. (2018). "The Origin and Evolutionary Biology of Pinnipeds: Seals, Sea Lions, and Walruses". Annual Review of Earth and Planetary Sciences. 0. doi:10.1146/annurev-earth-082517-010009.
Two species have been identified in the genus: P. valletoni, the type species, and P. miocenicum.{{cite web |url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=41157 |title=Potamotherium at the Paleobiology Database. |publisher=paleodb.org |access-date=2008-11-25}}
Distribution
File:Potamotherium valetoni skull 45.jpg
Finds range from the mid-latitudes of Europe and North America, dated from the Oligocene/Miocene boundary and surviving through to the end of the Miocene.Tedford, R. H. et al. (2004): Late Cretaceous and Cenozoic Mammals of North America (ed. Woodburne, M. O.), pp 169–231 (Columbia Univ. Press, 2004)Mörs, T. & Von Koenigswald, W. (2000): Potamotherium valletoni (Carnivora, Mammalia) aus dem Oberoligozän von Enspel im Westerwald. Senckenberg. Leth. no 80: pp 257–273 It has been interpreted by several researchers as a basal, non-marine ancestor of seals and sea lions, suggesting a freshwater phase in the evolutionary transition of pinnipeds from land to sea; geochemical analysis supports this hypothesis, finding P. valletoni to have been a freshwater dweller.{{Cite journal |last1=Kocsis |first1=László |last2=Rabi |first2=Márton |last3=Ulianov |first3=Alex |last4=Cipriani |first4=Anna |last5=Farkas |first5=Izabella M. |last6=Botfalvai |first6=Gábor |date=23 August 2023 |title=Geochemical investigation of the mixed Máriahalom vertebrate fauna at the Paleogene–Neogene boundary in the Central Paratethys: environmental conditions and age constrain |journal=Swiss Journal of Palaeontology |language=en |volume=142 |issue=1 |page=17 |doi=10.1186/s13358-023-00281-7 |doi-access=free |bibcode=2023SwJP..142...17K |issn=1664-2376 |hdl=11380/1328492 |hdl-access=free }} If Potamotherium was indeed a pinniped instead of a mustelid, its relatives were possibly early bears (whose ancestors at the time were small and generally weasel-like).
Palaeobiology
Physically, Potamotherium resembled a modern otter, and was {{convert|1.5|m|ft|sigfig=1}} long, with an elongated, slender body and short legs. With a flexible backbone and a streamlined shape, it was probably a good swimmer. Analysis of fossils suggests that Potamotherium had a poor sense of smell, but made up for this with good vision and hearing.{{cite book |editor=Palmer, D.|year=1999 |title= The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals|publisher= Marshall Editions|location=London|page= 215|isbn= 1-84028-152-9}}
Fossils of Potamotherium are so complete that the shape of the brain can be inferred via a digital endocast of the skull. The coronal gyrus (a fold on the lateral surface of the brain) is broad, slanted backwards and partially split by a small groove. The brain is nearly identical to that of Enaliarctos, an extinct mammal universally agreed to be close to pinnipeds. Modern pinnipeds and the extinct Pinnarctidion have an expanded coronal gyrus with a distinctive vertical orientation. The carnivorans with the largest coronal gyrus are freshwater foragers such as the otter civet (Cynogale bennetti) and certain otter species (in the genera Lutra and Lontra). They primarily emphasize sensitive whiskers (vibrissae) or the lips while hunting, rather than the hands. It is likely that the same was true for Potamotherium. Modern pinnipeds are unique among marine mammals for their large whiskers, which were probably inherited from an ancestor similar to Potamotherium.{{Cite journal |last1=Lyras |first1=George A. |last2=Werdelin |first2=Lars |last3=van der Geer |first3=Bartholomeus G. M. |last4=van der Geer |first4=Alexandra A. E. |date=2023-08-17 |title=Fossil brains provide evidence of underwater feeding in early seals |journal=Communications Biology |language=en |volume=6 |issue=1 |page=747 |doi=10.1038/s42003-023-05135-z |pmid=37591929 |issn=2399-3642|pmc=10435510 }}
References
{{Reflist}}
{{Pan-Pinnipedia|P.}}
{{Taxonbar|from=Q1636008}}
Category:Miocene mammals of North America
Category:Aquitanian genus first appearances
Category:Tortonian extinctions
Category:Prehistoric pinnipeds of North America
Category:Miocene mammals of Europe