View source for Tsoabichi

{{Short description|Extinct genus of reptiles}}
{{Automatic taxobox
| fossil_range = [[Eocene]]: [[Ypresian]], {{fossilrange|56|47.8|ref=<ref name="Rio2021">{{cite journal |last1=Rio |first1=Jonathan P. |last2=Mannion |first2=Philip D. |date=6 September 2021 |title=Phylogenetic analysis of a new morphological dataset elucidates the evolutionary history of Crocodylia and resolves the long-standing gharial problem |journal=[[PeerJ]] |volume=9 |pages=e12094 |doi=10.7717/peerj.12094 |pmid=34567843 |pmc=8428266 |doi-access=free}}</ref>}}
| image = Tsoabichi greenriverensis cast Catalog number FOBU801.jpg
| image_caption = ''Tsoabichi greenriverensis'' cast at [[Fossil Butte National Monument]], [[Lincoln County, Wyoming]]
| taxon = Tsoabichi
| authority = Brochu, 2010
| type_species = {{extinct}}'''''Tsoabichi greenriverensis'''''
| type_species_authority = Brochu, 2010
}}

'''''Tsoabichi''''' (from [[Shoshoni language|Shoshone]] "''tso’abichi’''", meaning "monster") is an [[extinct]] [[genus]] of [[caimanine]] [[crocodylia]]n. Fossils are known from the [[Green River Formation]] in [[Wyoming]], and date back to the [[Ypresian]] stage of the [[Eocene]] ([[Wasatchian]] stage of [[North American land mammal age|North American age]]). The genus was named and [[scientifically described|described]] in 2010 by paleontologist Christopher A. Brochu, with the [[type species]] being '''''Tsoabichi greenriverensis'''''.<ref name="BCA10">{{cite journal |last=Brochu |first=C.A.  |year=2010 |title=A new alligatorid from the lower Eocene Green River Formation of Wyoming and the origin of caimans  |journal=Journal of Vertebrate Paleontology |volume=30 |issue=4 |pages=1109–1126 |doi=10.1080/02724634.2010.483569|s2cid=129231903 }}</ref> According to the current understanding of caiman evolutionary relationships, ''Tsoabichi'' is a [[Basal (phylogenetics)|basal]] member of [[Caimaninae]] and may have evolved after caimans dispersed into North America from northern and central South America, their main center of diversity in the [[Cenozoic]].<ref name=HBJRM13>{{Cite journal | last1 = Hastings | first1 = A. K. | last2 = Bloch | first2 = J. I. | last3 = Jaramillo | first3 = C. A. | last4 = Rincon | first4 = A. F. | last5 = MacFadden | first5 = B. J. | title = Systematics and biogeography of crocodylians from the Miocene of Panama | doi = 10.1080/02724634.2012.713814 | journal = Journal of Vertebrate Paleontology | volume = 33 | issue = 2 | pages = 239 | year = 2013 | bibcode = 2013JVPal..33..239H | s2cid = 83972694 | doi-access = free }}</ref>

==Description==
Some living caimans such as the [[Spectacled Caiman]] have a "spectacle", or a bony ridge between the eyes. ''Tsoabichi'' lacks a spectacle, but it does have three smaller ridges between the [[orbit (anatomy)|orbits]], or eye sockets. In ''Tsoabichi'', distinct rims are seen around the [[Temporal fenestra|supratemporal fenestrae]], two holes on the [[Skull roof|skull table]]. Much of the [[supraoccipital]] bone is also found on the skull table, and forms a V-shape. To either side of the V-shaped supraoccipitals are the [[parietal bone]]s, which form the posterior margin of the skull table. Along the snout, the [[nasal bone]] forms a thin ridge, and narrows as it approaches the external [[naris]] where the nostrils are located.<ref name=BCA10/>

The dorsal [[osteoderm]]s (bony scutes along the back) are wider than those of other caimans. Some have two keels on their outer surface. ''Tsoabichi'' also has bipartite ventral osteoderms on its underside.<ref name=BCA10/>

==Phylogeny==
''Tsoabichi'' was included in a phylogenetic analysis when it was described in 2010. Brochu (2010) found it to be a [[Basal (phylogenetics)|basal]] member of [[Caimaninae]] closely related to the living genus ''[[Paleosuchus]]''.<ref name=BCA10/> The analysis of Hastings ''et al. ''(2013), which included several more species of caimans, also placed ''Tsoabichi'' in a basal position within Caimaninae as the [[sister taxon]] to [[crown group]] caimans (the smallest clade that includes all living caimans and their [[most recent common ancestor]]). ''[[Eocaiman]]'' and ''[[Culebrasuchus]]'' were successively more basal than ''Tsoabichi'', as shown in the [[cladogram]] below:<ref name=HBJRM13/>
{{clade| style=font-size:85%;line-height:85%
|1={{clade
   |1={{extinct}}''[[Stangerochampsa mccabei]]''
   |2={{clade
      |1={{extinct}}''[[Brachychampsa montana]]''
      |2={{extinct}}''[[Brachychampsa sealeyi]]''}}
   |label3=&nbsp;[[Alligatoridae]]&nbsp;
   |3={{clade
      |1=[[Alligatorinae]]
      |label2=&nbsp;[[Caimaninae]]&nbsp;
      |2={{clade
         |1={{extinct}}''[[Culebrasuchus mesoamericanus]]''
         |2={{clade
            |1={{extinct}}''[[Eocaiman cavernensis]]''
            |2={{clade
               |1={{extinct}}'''''Tsoabichi greenriverensis'''''
               |label2=[[crown group]] [[caimans]]
               |2={{clade
                  |1={{clade
                     |1=''Paleosuchus palpebrosus'' [[Cuvier's dwarf caiman]]
                     |2=''Paleosuchus trigonatus'' [[Smooth-fronted caiman]] }}
                  |2={{clade
                     |1={{clade
                        |1={{extinct}}''[[Centenariosuchus gilmorei]]''
                        |2={{clade
                           |1={{extinct}}''[[Purussaurus neivensis]]''
                           |2={{clade
                              |1={{extinct}}''[[Mourasuchus]]''
                              |2={{extinct}}''[[Orthogenysuchus olseni]]''}} }} }}
                     |2={{clade
                        |1={{clade
                           |1=''Caiman crocodilus'' [[Spectacled caiman]]
                           |2=''Caiman yacare'' [[Yacare caiman]] }}
                        |2={{clade
                           |1=''Caiman latirostris'' [[Broad-snouted caiman]]
                           |2={{extinct}}''[[Caiman lutescens]]''
                           |3={{clade
                              |1={{extinct}}''[[Melanosuchus fisheri]]''
                              |2=''Melanosuchus niger'' [[Black caiman]] }} }} }} }} }} }} }} }} }} }} }}

==Biogeography==
''Tsoabichi'' is one of the few caimanines known to have lived north of what is now Mexico; the majority of caimans living and extinct are known from Central and South America. Caimans are thought to have originated in North America in the [[Late Cretaceous]], yet ''Tsoabichi'' most likely originated from a South American population that reentered North America in the Early Eocene. The route by which a population of caimans could have reached North America in the Early [[Eocene]] is unknown. A sea route is unlikely given that living caimans have low tolerance for salt water, yet North and South America were separated by a large expanse of ocean. A continuous land route would not appear until the [[Isthmus of Panama]] formed several tens of millions of years later in the [[Pliocene]], and a potentially crossable island chain would not form until [[tectonic uplift]] between the two continents occurred in the Late Eocene. An alternative biogeographic explanation is that ''Tsoabichi'' descended from a population of ancestral caimans that never left North America, but this hypothesis is unlikely given that it would necessitate multiple independent dispersals into Central and South America (including one for ''Culebrasuchus'', one for ''Eocaiman'', one for ''Paleosuchus'', and one for [[Derived trait|derived]] caimans).<ref name=HBJRM13/>

==References==
{{Reflist}}
 
{{Portal|Paleontology}}

{{Extinct Crocodilia|A.}}
{{Taxonbar|from=Q7849815}}

[[Category:Alligatoridae]]
[[Category:Eocene reptiles of North America]]
[[Category:Fossil taxa described in 2010]]
[[Category:Eocene crocodylomorphs]]
[[Category:Prehistoric pseudosuchian genera]]