Editing Pakicetidae (section)

==Description==
{{Harvnb|Dehm|Oettingen-Spielberg|1958}} described the first pakicetid, ''[[Ichthyolestes]]'', but at the time they did not recognize it as a cetacean, identifying it, instead, it as a [[fish]]-eating [[Mesonychidae|mesonychid]]. Robert West was the first to identify pakicetids as cetaceans in 1980 and, after discovering a braincase, Phillip Gingerich and Donald Russell described the genus ''[[Pakicetus]]'' in 1981. During the following two decades, more research resulted in additional pakicetid cranial material and by 2001 postcranial material for the family had been described. Though all parts of pakicetid postcrania are known, no complete [[skeleton]] from a single individual has been recovered.<ref name="thewetal-2001">{{Harvnb|Thewissen|Williams|2002| pp=75–8}}</ref>
The pakicetid goldmine is the "H-GSP Locality 62" site in the [[Kala Chitta Range|Kala Chitta Hills]] where fossils from all three genera have been found.  However, this site is so littered with bones that identifying bones from a single individual is impossible, and pakicetid skeletons are consequently composites of bones from several individuals.<ref name=":0">{{Harvnb|Thewissen|Cooper|George|Bajpai|2009|p=277}}</ref>

Pakicetids have been found in or near [[river]] deposits in northern Pakistan and northwestern [[India]], a region which was probably [[arid]] with only temporary streams when these animals lived there. No pakicetids have been found in marine deposits, and they were apparently [[Terrestrial animal|terrestrial]] or freshwater animals. Their long limbs and small hands and feet also indicate they were poor swimmers. Their bones are heavy and compact and were probably used as [[ballast]]; they clearly indicate pakicetids were not fast runners notwithstanding their otherwise [[cursorial]] morphology. Most likely, pakicetids lived in or near bodies of freshwater and their diet could have included both land animals and aquatic organisms. During the [[Eocene]], [[Pakistan]] was an island-continent off the coastal region of the [[Eurasia]]n land mass and therefore an ideal habitat for the evolution and diversification of the Pakicetids.<ref name="thewetal-2001" />

{| class="wikitable"
 | Pakicetids have many [[apomorphic]] traits (derived traits shared by several taxa) found in [[Even-toed ungulate|artiodactyls]], including:<ref name="Uhen-2010" />
 | Traits linking pakicetids to cetaceans include:<ref name="Uhen-2010" />
|-
|
* small [[mandibular foramina]] and [[Mandibular canal|canals]]
* elongated [[cervical vertebrae]]
* long and gracile limbs featuring "double-pulleyed" [[Talus bone|astragalus]] in the ankle
* long [[metapodial]]s and
* four fused [[sacrum|sacral]] vertebrae
|
* a pachyosteosclerotic (thick, heavy bone) [[auditory bulla]] with an [[involucrum]] and [[sigmoid process]]
* cheek teeth adapted for shearing with reentrant grooves on the anterior surfaces
* lower [[Molar (tooth)|molars]] lacking [[trigonid]] and [[talonid]] basins and upper molars with very small [[Molar (tooth)#Tribosphenic|trigon]] basins
* incisors and canines aligned to the cheek teeth
* narrow elongated postorbital (behind eyes) cranium
|}