| Globidentosuchus | |
|---|---|
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Archosauria |
| Order: | Crocodilia |
| Family: | Alligatoridae |
| Subfamily: | Caimaninae |
| Genus: | †Globidentosuchus Scheyeret al.,2013 |
| Type species | |
| †Globidentosuchus brachyrostris Scheyeret al., 2013 | |
Globidentosuchus is anextinctgenus ofbasalcaimaninecrocodylian known from the lateMiddle to Late Miocene of the Middle and the Upper Members of theUrumaco Formation atUrumaco,Venezuela.[2] Its skull was very short and robust, with large units of spherical teeth used to break the shells of molluscs as part of itsdurophagus diet.[3][2] It is thought to be one of the most basal Caimanines, even sharing some traits with alligatorids.[2]
The generic nameGlobidentosuchus is derived from the Latin rootsglobus meaning "sphere" anddens meaning "tooth", referring to the spherical teeth in the posterior skull, and Greeksouchos meaning "crocodile" after its classification. The species namebrachyrostris is derived from the Greekbrachys meaning "short" and Latinrostrum meaning "snout" after the truncated and robust rostrum of the species.[2]
Globidentosuchus was described in 2013 by T. M. Scheyer and colleagues, the type and only species beingG. brachyrostris, on the basis of cranial and mandibular remains that had been collected from the El Picache and Domo de Agua Blanca localities inUrumaco,Venezuela, the fossils coming from theUpper Miocene aged strata of the Upper and Middle Members of theUrumaco Formation.[2] The chosen holotype (AMU-CURS-222) consists of a nearly skull with associated mandibles, including several of the spherical crushing teeth, and the paratype (AMU-CURS-224) was more fragmentary, consisting of only an incomplete skull associated with mandibles. Some other fragmentary specimens were referred in 2013 and 2016, but all were either fossils of the skull or mandible.[2][3] In 2017, a partial skull that was first described as a skull ofMelanosuchus fisheri from the Urumaco Formation ofFalcón, Venezuela was reassigned toGlobidentosuchus, making it the first knownGlobidentosuchus specimen.[4]
Globidentosuchus was a small caimanine species at only 1.72 metres (5.6 ft) meters in length and 16.7 kilograms (37 lb) in weight, around the same size as the average adult maleCaiman crocodilus.[5] The most notable feature ofGlobidentosuchus is its U-shaped, wide, and short skull and robust, deep mandibles that were built for crushing hard prey like molluscs.[6][2]Globidentosuchus differentiates from other caimanines in several areas, such as; a fused external naris that was not bisected by thenasals, the smooth skull with weak preorbital ridges and norostral orinterorbital ridges, in strong contrast to the strong ridges in gavialoids and some caimans.[6][2] Each mandible preserves 18 teeth, 10 conical teeth in the anterior portion and 8 spherical, robust teeth in the posterior portion. These spherical teeth were tightly packed, making a crushing unit that was built to crush molluscs.[2] This morphology is also observed in several other caimanines, likeCaiman brevirostris,[7]C. latirostris, andAllognathosuchus, though none of these taxa have crushing units like inGlobidentosuchus.[2] The mandible has 13 alvelovi, the largest being in the back of the mandible but they get much smaller after the 4th alvelovi, a trait missing in other caimanines but was likely convergently evolved as some early alligatoroids bare this.[2]
Globidentosuchus is often recovered as one of or the most basal caimanines, with the original phylogenetic analysis in 2013 finding it to be a stem caimanine and the sister taxon to all other caimanines, even more basal than Paleogene caimanines likeNecrosuchus andEocaiman.[2] Hastings et al. (2013) proposed that this phylogenetic position is because of a potential relict population of basal caimanines that persisted in Central America and/or northern South America into the Late Miocene, as shown byGlobidentosuchus and its basal relativesGnatusuchus andCulebrasuchus,[8][6] though more fossils are needed to confirm this.[9]
The following tree is based on the results recovered by Cidadeet al. (2017),[10] excluding the North AmericanOrthogenysuchus and including the then newly namedMourasuchus pattersoni while also following the synonymy ofM. nativus withM. arendsi. This analysis also recoversGlobidentosuchus as one of the most basal caimanines at a similar level toCulebrasuchus andGnatusuchus.[4][2]
| Alligatoridae |
| ||||||||||||||||||||||||||||||||||||
As the Proto-Amazonian lake system and the Pebas system began to dissipate with the onset of the transcontinental Amazon Drainage,Globidentosuchus inhabited the wetlands of the northernUrumaco Formation in Venezuela into the Late Miocene before eventually dying out by the Early Pliocene like much of the large crocodilian fauna of the Miocene wetlands. These wetlands provided favorable conditions to the native reptilian fauna, with several lineages of crocodilians reaching enormous sizes during the Mid to Late Miocene and also diversifying in ecology. Some of the enormous crocodilians that coexisted withGlobidentosuchus included the enormous caimainPurussaurus, the bizarreMourasuchus and large-bodied gharials of the genusGryposuchus, some species of which reaching lengths of over 10 meters.[11] The largest turtle known,Stupendemys, with one specimen preserving a 2.86 meter long carapace, was also present in the region as an omnivore.[12] Other durophagus caimanines inhabited the Urumaco, including the unusualCaiman brevirostris and extantC. latirostris.[3] Besides the aforementioned reptiles, the waterways of Late Miocene South America were also inhabited by fish, includingcatfish such asPhractocephalus andCallichthyidae,characids such asAcregoliath rancii and thetambaqui (Colossoma macropomum), theSouth American lungfish (Lepidosiren paradoxa),trahiras (e.g.Paleohoplias assisbrasiliensis) and freshwaterrays andsharks. Other turtles andtortoises found in the same deposits areChelus columbiana (a fossil relative of themata mata) andChelonoidis. Further aquatic vertebrates includedriver dolphins and the largedarter"Anhinga" fraileyi. Palynofloras found in the Urumaco Formation suggest a continuation of the Amazonian forest into northwestern Venezuela during the Miocene,[13][14] while the Early Pliocene replaced these forests with xerophyte-dominated habitats after the collapse of the Urumaco delta and its environment,[15] which ended the great crocodilian diversity that was present in Venezuela.[16][15]
Extinctcrocodilians | |||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| |||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||
