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Gryposuchus

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Gryposuchus
Temporal range: Miocene (Colhuehuapian-Huayquerian)
~21–6.8 Ma
Fossils of the skull and mandible of G. colombianus, Museo Geológico José Royo y Gómez, Bogotá.
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauromorpha
Clade: Archosauriformes
Order: Crocodilia
Family: Gavialidae
Subfamily: †Gryposuchinae
Genus: †Gryposuchus
Gurich 1912
Species

Gryposuchus is an extinct genus of gavialoid crocodilian. It is the type genus of the subfamily Gryposuchinae. Fossils have been found from Argentina, Colombia, Venezuela, Brazil and the Peruvian Amazon. The genus existed in the Miocene epoch (Colhuehuapian to Huayquerian).[1] One recently described species, G. croizati, grew to an estimated length of 10 metres (33 ft).

Species

The type species of Gryposuchus is G. jessei, named based on a well-preserved rostrum collected along the Pauini River of Brazil in 1912. The specimen was probably destroyed during World War II by the 1943 bombing of Hamburg.[2] Another specimen named UFAC 1272, consisting of a premaxilla and maxilla, was discovered in the nearby Sena Madureia locality of the late Miocene Solimões Formation,[1] in and referred to the species in 1997.[3] G. jessei is also referred to from the Urumaco Formation of northwestern Venezuela.[1] A second species, G. neogaeus, was referred to the genus in 1982; specimens from this species were first described from the late Miocene Ituzaingó Formation of Argentina in 1885,[1] although it was referred to Rhamphostomopsis at the time.[2][4][5]

Another species, G. colombianus, has been recovered from deposits from the Middle Miocene Honda Group of Colombia, and the late Miocene Urumaco Formation in Venezuela.[1] This species, named in 1965, was originally referred to Gavialis.[6] Fragmentary material of Gryposuchus from the Fitzcarrald Arch in the Peruvian Amazon dating back to the late middle Miocene bear a close resemblance to G. colombianus, but differ in rostrum proportions.[1][7]

Scale diagram showing the size of G. croizati (light blue)
Gryposuchus is located in South America
Gryposuchus
Gryposuchus
Gryposuchus
Gryposuchus
Gryposuchus
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Gryposuchus fossil localities
Colloncuran
Laventan
Chasicoan
Huayquerian

A species described in 2008, G. croizati, also found from the upper Miocene Urumaco Formation in Venezuela,[1] can be distinguished from other species of Gryposuchus on the basis of a reduced number of maxillary teeth, a slender parietal interfenestral bar, and widely separated and reduced palatine fenestrae, and other characters. Based on measurements of the orbital cranial skeleton, the length of the animal has been estimated at around 10.15 metres (33.3 ft) in length, with a total mass of about 1,745 kilograms (3,847 lb). Measuring the entire length of the skull from the end of the rostrum to the supraoccipital would result in a much larger size estimate, up to three times as great. However, because there is considerable variation seen in rostral proportions among crocodilians, the latter measurements are probably not an accurate way of estimating body mass and length.[8] Despite this, the species is still one of the largest crocodilians known to have existed, and it may indeed have been the largest gavialoid to have ever existed if a recent revision in the estimated size of the large tomistomine Rhamphosuchus is correct (the genus was once considered to be 15 metres (49 ft) in length; the new estimate puts it at approximately 10 metres (33 ft)).[9]

Some skull material also recovered from Peruvian Amazon (Iquitos) in the Pebas Formation of the Middle Miocene,[1] was named as Gryposuchus pachakamue in 2016 by Rodolfo Salas-Gismondi et al. It includes the holotype MUSM 987, a well preserved skull that lacks of temporal and occipital bones; it measures 623.2 millimeters in length, and a series of referred specimens, including possible juveniles. The species was named after the Quechuan word for a primordial god and "storyteller".[10] This new species is characterized by have 22 teeth in the mandible and the maxilla, a snout comparable in relative length to the modern Gavialis gangeticus, and is notable since that its orbits were wider than long and not so upturned as another species of gavialids, including the gryposuchines, which implies that G. pachakamue doesn't had the "telescoped" orbits (protruding eyes) condition fully developed. Since that it species, that inhabited the proto-Amazon fluvial system 13 million years ago, is the oldest record of gavialids in this area and it had a primitive telescoped eyes condition, it shows that the development of such condition was a case of convergent evolution with the species of Gavialis also found in fluvial environments.[10]

G. neogaeus and G. colombianus have been proposed as synonyms of G. jessei,[11] but this is unlikely due to the number of anatomical differences between them.[2][3] Furthermore, indeterminate finds of Gryposuchus were noted from the early Miocene Castillo Formation of Venezuela, middle Miocene Pebas Formation of Peru, middle/late Miocene Tranquitas Formation of Argentina and from the late Miocene formations Urumaco of Venezuela and Solimões in both Brazil and Peru.[1] Additionally, indeterminate finds of gavialoids (both in coastal/marine sediments) are present in early Miocene Jimol Formation and for the early/middle Miocene Castilletes Formation in Colombia, as per Moreno-Bernal et al.[1][12]

Paleoecology

The Miocene epoch represents the only history of gavialoids (solely of the subfamily Gryposuchinae) into South America, from a Caribbean launchpad (Aktiogavialis from the Late Oligocene of Puerto Rico,[13] and Dadagavialis from the Early Miocene of Panama).[14] Although there were six other confirmed genera of gryposuchine, Gryposuchus was almost certainly the most successful, with an existence potentially encompassing almost all of the Miocene, and a range from Venezuela to Argentina in the Late Miocene. This dominance was likely due to the fact that Gryposuchus was one of only two freshwater adapted gryposuchines (other than Hesperogavialis),[15] whereas the others (such as Siquisiquesuchus and Piscogavialis) were either primarily estuarine, coastal or marine based predators.[16][17] This would certainly have been useful in taking advantage of the extensive continental waterways and swamps of what would become the Amazon basin. Gryposuchus can be observed far and wide, from coastally adjacent and inclusive formations, such as the Urumaco Formation of Venezuela,[18][19] to even beyond the northern drainage basins, into Argentina. This is in contrast with almost all the other species within the subfamily, which are limited to certain time periods near or on coast, with only Hesperogavialis penetrating into Brazil in the Late Miocene.

Although Gryposuchus had already reached Argentina by the Middle Miocene, known species diversity reached its peak by the Late Miocene, with four of the five species present, three of which were also overlapping in the Urumaco Formation. Gryposuchinae diversity also reached its peak, at five genera across South America. However, at the Miocene/Pliocene boundary, all Gavialoidea and Crocodyloidea (another superfamily colonising in the Miocene) were likely extirpated from South America, with the endemic Caimaninae undergoing a severe reduction in size and diversity as well. This was likely due to the continuing elevation of the northern sections of the Andes chain reshaping the future Amazon basin, re-rerouting drainage flowing towards Caribbean to the much cooler Atlantic, and thus restricting the space and food resources of these large, food-intensive specialist crocodilians.[1][20]

References

  1. ^ a b c d e f g h i j k Cidade, Giovanne; Fortier, Daniel; Hsiou, Annie (2018-12-01). "The crocodylomorph fauna of the cenozoic of South America and its evolutionary history: A review". Journal of South American Earth Sciences. 90. doi:10.1016/j.jsames.2018.12.026.
  2. ^ a b c de Souza, R.G.; Riff, D.; de Souza-Filho, J.P.; Kellner, A.W.A. (2018). "Revisiting Gryposuchus jessei Gürich, 1912 (Crocodylia: Gavialoidea): specimen description and comments on the genus". Zootaxa. 4457 (1): 167–178. doi:10.11646/zootaxa.4457.1.9. PMID 30314186.
  3. ^ a b Langston, W.; Gasparini, Z. (1997). "Crocodilians, Gryposuchus, and the South Americans gavials". In Kay, R.F.; Madden, R.H.; Cifelli, R.L.; Flynn, J.J. (eds.). Vertebrate Paleontology in the Neotropics: The Miocene Fauna of La Venta, Colombia. Washington: Smithsonian Institution. pp. 113–154.
  4. ^ Burmeister, G. (1885). "Examen crítico de los mamíferos y los reptiles denominados pot Don Augusto Bravard". Anales del Museo Púbtico de Buenos Aires. 3: 95–173.
  5. ^ Cozzuol, M. A. (2006). "The Acre vertebrate fauna: Age, diversity, and geography". Journal of South American Earth Sciences. 21: 185–203. doi:10.1016/j.jsames.2006.03.005.
  6. ^ Langston, W. (1965). "Fossil crocodilians from Colombia and the Cenozoic history of the Crocodilia in South America". University of California Publications in Geological Sciences. 52: 1–152. {{cite journal}}: Invalid |ref=harv (help)
  7. ^ Salas-Gismondi, R.; Antoine, P. O.; Baby, P.; Brusset, S.; Benammi, M.; Espurt, N.; de Franceschi, D.; Pujos, F.; Tejada, J.; Urbina, M (2007). "Middle Miocene crocodiles from the Fitzcarrald Arch, Amazonian Peru". In Díaz-Martínez, E.; Rábano, I. (eds.). 4th European Meeting on the Palaeontology and Stratigraphy of Latin America. Cuadernos del Museo Geominero. Vol. 8. Madrid: Instituto Geológico y Minero de España.
  8. ^ Riff, D.; Aguilera, O. A. (2008). "The world's largest gharials Gryposuchus: description of G. croizati n. sp. (Crocodylia, Gavialidae) from the Upper Miocene Urumaco Formation, Venezuela". Paläontologische Zeitschrift. 82 (2): 178–195. doi:10.1007/bf02988408. {{cite journal}}: Invalid |ref=harv (help)
  9. ^ Head, J. J. (2001). "Systematics and body size of the gigantic, enigmatic crocodyloid Rhamphosuchus crassidens, and the faunal history of Siwalik Group (Miocene) crocodylians". Journal of Vertebrate Paleontology. 21 (Supplement to No. 3): 59A.
  10. ^ a b Salas-Gismondi, Rodolfo; Flynn, John J.; Baby, Patrice; Tejada-Lara, Julia V.; Claude, Julien; Antoine, Pierre-Olivier (2016). "A New 13 Million Year Old Gavialoid Crocodylian from Proto-Amazonian Mega-Wetlands Reveals Parallel Evolutionary Trends in Skull Shape Linked to Longirostry". PLoS ONE. 11 (4): e0152453. doi:10.1371/journal.pone.0152453. PMC 4838223. PMID 27097031. {{cite journal}}: Invalid |ref=harv (help)CS1 maint: unflagged free DOI (link)
  11. ^ Buffetaut, E. (1982). "Systematique, origine et évolution des Gavialidae Sud Américains". Geobios. 16 (1S): 127–140. doi:10.1016/S0016-6995(82)80107-1.
  12. ^ Moreno-Bernal, Jorge W.; Head, Jason; Jaramillo, Carlos A. (2016-05-03). "Fossil Crocodilians from the High Guajira Peninsula of Colombia: Neogene faunal change in northernmost South America". Journal of Vertebrate Paleontology. 36 (3): e1110586. doi:10.1080/02724634.2016.1110586. ISSN 0272-4634.
  13. ^ Vélez-Juarbe, Jorge; Brochu, C.A.; Santos, H. (2007). "A gharial from the Oligocene of Puerto Rico: transoceanic dispersal in the history of a non-marine reptile". Proceedings of the Royal Society B. 274 (1615): 1245–1254. doi:10.1098/rspb.2006.0455. PMC 2176176. PMID 17341454.
  14. ^ Salas-Gismondi, Rodolfo; Moreno-Bernal, Jorge W.; Scheyer, Torsten M.; Sánchez-Villagra, Marcelo R.; Jaramillo, Carlos (2019-06-18). "New Miocene Caribbean gavialoids and patterns of longirostry in crocodylians". Journal of Systematic Palaeontology. 17 (12): 1049–1075. doi:10.1080/14772019.2018.1495275. ISSN 1477-2019.
  15. ^ Kay, R. F. and Madden, R. H. (1997). Paleogeography and paleoecology. In: Kay, R. F., Madden, R. H, Cifelli, R. L., and Flynn, J. J., eds., Vertebrate paleontology in the neotropics: the Miocene fauna of La Venta, Colombia. Smithsonian Institution Press; Washington, DC. pp. 520–550.
  16. ^ Kraus, R (1998). "The cranium of Piscogavialis jugaliperforatus n. gen., n. sp. (Gavialidae, Crocodylia) from the Miocene of Peru". Paläontologische Zeitschrift. 72: 389–406. doi:10.1007/bf02988368.
  17. ^ Brochu, C. A.; Rincon, A. D. (2004). "A gavialoid crocodylian from the Lower Miocene of Venezuela". Special Papers in Palaeontology. 71: 61–78.
  18. ^ Linares, O. J. (2004). "Bioestratigrafia de la fauna de mamiferos de las Formaciones Socorro, Urumaco y Codore (Mioceno Medio–Plioceno Temprano) de la region de Urumaco, Falcon, Venezuela". Paleobiologia Neotropical. 1: 1–26.
  19. ^ Sánchez-Villagra, M. R.; Aguilera, O. A. (2006). "Neogene vertebrates from Urumaco, Falcón State, Venezuela: diversity and significance". Journal of Systematic Palaeontology. 4: 213–220. doi:10.1017/s1477201906001829.
  20. ^ "Fourteen closely related crocodiles existed around 5 million years ago". ScienceDaily. Retrieved 2020-04-19.
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