Prorastomidae

{{Short description|Extinct family of mammals}} {{Automatic taxobox | fossil_range = Eocene | image = Prorastomus BW.jpg | image_caption = ''Prorastomus sirenoides'' | taxon = Prorastomidae | authority = | subdivision_ranks = Genera | subdivision = †''Pezosiren''<br /> †''Prorastomus'' }} thumb|''Pezosiren portelli'' cast skeleton '''Prorastomidae''' is a family of extinct sirenians from Jamaica, related to the extant manatees and dugong.<ref>{{Cite web|url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=43285|title=Fossilworks: Prorastomidae|website=fossilworks.org|access-date=17 December 2021}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=p84IxiWkAX8C&q=Prorastomidae&pg=PA50|title=Ecology and Conservation of the Sirenia: Dugongs and Manatees|last1=Marsh|first1=Helene|last2=O'Shea|first2=Thomas J.|last3=Reynolds|first3=John Elliott|last4=III|first4=John E. Reynolds|date=December 2011|publisher=Cambridge University Press|isbn=9780521888288}}</ref><ref>{{Cite web|url=http://taxonomicon.taxonomy.nl/TaxonTree.aspx?id=69399&src=1593|title=Family †Prorastomidae - Hierarchy - The Taxonomicon|website=taxonomicon.taxonomy.nl|access-date=2019-06-27}}</ref> The family includes the oldest known fossils of Sirenians, represented in two genera: *''Pezosiren'' ''Pezosiren'' comprises one known species, ''Pezosiren portelli'', that was discovered in modern-day Jamaica.<ref>{{cite journal |last1=Domning |first1=D. P. |title=The earliest known fully quadrupedal Sirenian |journal=Nature |date=2001 |volume=413 |issue=6856 |pages=625–627 |doi=10.1038/35098072 |pmid=11675784 |bibcode=2001Natur.413..625D |s2cid=22005691 |url=https://www.webpages.uidaho.edu/~jacks/Domning.01.pdf |accessdate=22 July 2020}}</ref> One of the earliest true Sirenian species, ''P. portelli'' is distinct from extant Sirenians due to its quadrupedal stature. The species is estimated to have lived 50 million years ago during the Mid Eocene, and the skeletal elements suggest that ''P. portelli'' was able to properly support its body weight while out of the water. However, several morphological features suggest that this species spent significant amounts of time in an aquatic environment, such as ''P. portelli'''s pachyosteosclerotic ribs.<ref>{{cite journal |last1=Prothero |first1=D. R. |title=Evolutionary transitions in the fossil record of terrestrially hoofed animals |journal=Evolution: Education and Outreach |date=2009 |volume=2 |page=239-302 |doi=10.1007/s12052-009-0136-1 |s2cid=32344744 |doi-access=free }}</ref> Similar to an extant manatee's ribs, these ribs provided a ballast and allowed the animal to achieve neutral buoyancy. ''P. portelli'' lacked the large, muscular tail used in modern Sirenians to propel through the water column, and skeletal anatomy suggests that they instead garnered propulsive force through spinal undulations, similar to otters. This evidence suggests that ''P. portelli'' likely divided its time between terrestrial habitats and shallow aquatic habitats, convergently akin to hippopotamuses.<ref>{{cite journal |last1=Domning |first1=D. P. |title=The earliest known fully quadrupedal Sirenian |journal=Nature |date=2001 |volume=413 |issue=6856 |pages=625–627 |doi=10.1038/35098072 |pmid=11675784 |bibcode=2001Natur.413..625D |s2cid=22005691 |url=https://www.webpages.uidaho.edu/~jacks/Domning.01.pdf |accessdate=22 July 2020}}</ref>

*''Prorastomus'' The genus ''Prorastomus'' is also represented by only one known species. ''Prorastomus sirenoides'' lived in modern day Jamaica during the Mid Eocene, and it is thought to be the oldest Sirenian species discovered so far.<ref>{{cite journal |last1=Díaz-Berenguer |first1=E. |last2=Badiola |first2=A. |last3=Moreno-Azanza |first3=M. |last4=Canudo |first4=J. I. |title=First adequately-known quadrupedal sirenian from Eurasia (Eocene, Bay of Biscay, Huesca, northeastern Spain) |journal=Scientific Reports |date=2018 |volume=8 |issue=1 |page=5127 |doi=10.1038/s41598-018-23355-w |pmid=29572454 |pmc=5865116 |bibcode=2018NatSR...8.5127D |url=}}</ref> Similar to ''P. portelli'', this quadrupedal Sirenian likely displayed a lifestyle comparable to hippos, spending large amounts of time both in and out of water. The species was determined to have had relatively large olfactory bulbs for a Sirenian, suggesting that the sense of smell was of importance to ''P. sirenoides'', and the trigeminal nerves, utilized in somatosensory, were found to be enlarged.<ref>{{cite journal |last1=Benoit |first1=J. |last2=Crumpton |first2=M. |last3=Mérigeaud |first3=S. |last4=Tabuce |first4=R. |title=A Memory Already like an Elephant's? The Advanced Brain Morphology of the Last Common Ancestor of Afrotheria (Mammalia) |journal=Brain, Behavior and Evolution |date=2013 |volume=81 |issue=3 |pages=154–69 |doi=10.1159/000348481 |pmid=23548592 |s2cid=6524017 |url=https://www.karger.com/article/fulltext/348481 |accessdate=22 July 2020|doi-access=free }}</ref> Extant Sirenian species possess comparably large trigeminal nerves, allowing for highly sensitive facial tactility.<ref>{{cite journal |last1=Sarko |first1=D. K. |last2=Johnson |first2=J. J |last3=Switzer III |first3=R.C. |last4=Welker |first4=W. I. |last5=Reep |first5=R. R. |title=Somatosensory nuclei of the manatee brainstem and thalamus |journal=The Anatomical Record |date=2007 |volume=290 |issue=9 |pages=1138–65 |doi=10.1002/ar.20573 |pmid=17722080 |s2cid=8328805 |doi-access=free }}</ref> Dentile fossils of ''P. sirenoides'' suggest that the species fed primarily on floating and emergent vegetation along its habitat.<ref>{{cite journal |last1=Savage |first1=R. J. G. |last2=Domning |first2=D. P. |last3=Thewissen |first3=J. G. M. |title=Fossil sirenia of the west Atlantic and Caribbean region. V. The most primitive known sirenian, Prorastomus sirenoides Owen, 1855 |journal=Journal of Vertebrate Paleontology |date=1994 |volume=14 |issue=3 |page=427-449 |doi=10.1080/02724634.1994.10011569 |url=https://www.tandfonline.com/doi/abs/10.1080/02724634.1994.10011569 |accessdate=22 July 2020|url-access=subscription }}</ref>

==See also== {{Portal|Paleontology}} *Evolution of sirenians

== References == {{Reflist}}

Category:Eocene sirenians Category:Prehistoric mammal families Category:Eocene first appearances Category:Eocene extinctions