Dyrosauridae

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Not to be confused with Dryosauridae
Dyrosauridae
Temporal range: 70–35Ma
Maastrichtian - Eocene
Arambourgisuchus.jpg
Skull of the dyrosaurid Arambourgisuchus khouribgaensis
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Superorder: Crocodylomorpha
Clade: Neosuchia
Suborder: Tethysuchia
Family: Dyrosauridae
de Stefano, 1903
Genera

See below

Dyrosauridae is a family of extinct neosuchian crocodyliforms that lived from the Late Cretaceous (Maastrichtian) to the Eocene. Dyrosaurid fossils are globally distributed, having been found in Africa, Asia, Europe, North America and South America. Over a dozen species are currently known, varying greatly in overall size and cranial shape. All were presumably aquatic, with species inhabiting both freshwater and marine environments. Ocean-dwelling dyrosaurids were among the few marine reptiles to survive the Cretaceous–Paleogene extinction event.

Paleobiogeography[edit]

Dyrosaurids were once considered an African group, but more recent discoveries indicate they inhabited the majority of the continents.[1] In fact, basal forms suggest that their cradle may have been North America.

Genera[edit]

Genus Status Age Location Description Images
Acherontisuchus Valid Paleocene  Colombia A large-bodied, long-snouted freshwater dyrosaurid from the Cerrejón Formation
Anthracosuchus In press Paleocene  Colombia A short-snouted freshwater dyrosaurid from the Cerrejón Formation
Arambourgisuchus Valid Paleocene  Morocco A long-snouted marine dyrosaurid
Atlantosuchus Valid Paleocene  Morocco A long-snouted marine dyrosaurid with the longest snout length in proportion to body size of any dyrosaurid
Cerrejonisuchus Valid Paleocene  Colombia A small-bodied, short-snouted freshwater dyrosaurid from the Cerrejón Formation
Chenanisuchus Valid Maastrichtian-Paleocene  Mali
 Morocco
The genus spans the K-Pg boundary Chenanisuchus BW.jpg
Congosaurus Valid Paleocene  Angola
Dyrosaurus Valid Eocene  Algeria
 Tunisia
A large-bodied, long-snouted marine dyrosaurid Dyrosaurus BW.jpg
Guarinisuchus Valid Paleocene  Brazil A marine dyrosaurid Guarinisuchus munizi.jpg
Hyposaurus Valid Maastrichtian-Paleocene  Brazil
 Mali
 Nigeria
 USA
Five species have been named, the most of any dyrosaurid genus; the genus spans the K-Pg boundary
Phosphatosaurus Valid Eocene  Mali
 Tunisia
A large-bodied, long-snouted marine dyrosaurid with blunt teeth and a spoon-shaped snout tip
Rhabdognathus Valid Maastrichtian-Paleogene  Mali
 Nigeria
A large-bodied, long-snouted marine dyrosaurid; the genus spans the K-Pg boundary
Sokotosaurus Junior synonym Junior synonym of Hyposaurus
Sokotosuchus Valid Maastrichtian  Nigeria A long-snouted marine dyrosaurid
Tilemsisuchus Valid Eocene  Mali

Phylogeny[edit]

Jouve et al. (2005) diagnose Dyrosauridae as a clade based on the following seven synapomorphies or shared characters:

  • Posteromedial wing of the retroarticular process dorsally situated ventrally on the retroarticular process
  • Occipital tuberosities small
  • Exoccipital participates largely to the occipital condyle
  • Supratemporal fenestra anteroposteriorly strongly elongated
  • Symphysis about as wide as high
  • Quadratojugal participates largely to the cranial condyle for articulation with the jaw
  • 4 premaxillary teeth

Below is a cladogram after Jouve et al. (2005) showing phylogenetic relationships of Dyrosauridae and other closely related neosuchians:

Neosuchia


Eutretauranosuchus



Elosuchus



Sarcosuchus





Terminonaris


Dyrosauridae

Chenanisuchus





Sokotosuchus



Phosphatosaurus





Dyrosaurus





Arambougisuchus



Congosaurus



Hyposaurus rogersii





Rhabdognathus rarus



Rhabdognathus sp.









Composite cladogram for Dyrosauridae (from Jouve et al. 2008 and Barbosa et al. 2008):

Dyrosauridae 

Chenanisuchus



 Phosphatosaurinae 

Sokotosuchus



Phosphatosaurus



 Dyrosaurinae 

Dyrosaurus




Arambourgisuchus



Guarinisuchus




Hyposaurus




Congosaurus




Atlantosuchus



Rhabdognathus








Dyrosauridae incertae sedis: Tilemsisuchus


Cladogram after Hastings et al. (2011) showing geographic occurrences of taxa:[2]

Neosuchia 

Sarcosuchus imperator Cartography of Africa.svg




Terminonaris robusta Cartography of North America.svg




Elosuchus cherifiensis Cartography of Africa.svg


 Dyrosauridae 

Chenanisuchus lateroculi Cartography of Africa.svg




Sokotosuchus ianwilsoni Cartography of Africa.svg




Phosphatosaurus gavialoides Cartography of Africa.svg




Cerrejonisuchus improcerusCartography of South America.svg




Arambourgisuchus khouribgaensis Cartography of Africa.svg





Dyrosaurus phophaticus Cartography of Africa.svg



Dyrosaurus maghribensis Cartography of Africa.svg





Hyposaurus rogersii Cartography of North America.svg



Acherontisuchus guarjiraensis Cartography of South America.svg



Congosaurus bequaerti Cartography of Africa.svg





Atlantosuchus Cartography of Africa.svg



Guarinisuchus Cartography of South America.svg





Rhabdognathus keiniensis Cartography of Africa.svg



Rhabdognathus aslerensis Cartography of Africa.svg














Analysis suggest that the closest relatives of dyrosaurids are Sarcosuchus and Terminonaris.

Palaeobiology[edit]

Habitat[edit]

Most dyrosaurids were marine crocodiles. Dyrosaurids found from what is now northern and western Africa are thought to have inhabited the Trans-Saharan Sea, an epicontenental seaway that covered low-lying basins that formed during the late Mesozoic breakup of Africa and South America through crustal attenuation and fault reactivation, during a time of great global sea level elevation.[3][4]

Dyrosaurids have also been found from nonmarine sediments. In northern Sudan, dyrosaurids are known from fluvial deposits, indicating that they lived in a river setting.[5] Bones from indeterminate dyrosaurids have been found in inland deposits in Pakistan as well. Some dyrosaurids, such as those from the Umm Himar Formation in Saudi Arabia, inhabited estuarine environments near the coast. The recently named dyrosaurids Cerrejonisuchus and Acherontisuchus have been recovered from the Cerrejón Formation in northwestern Colombia, which is thought to represent a transitional marine-freshwater environment surrounded by rainforest more inland than the estuarine environment of the Umm Himar Formation.[6] Cerrejonisuchus and Acherontisuchus lived in a neotropical setting during a time when global temperatures were much warmer than they are today.[7][8]

Reproduction[edit]

In 1978, it was proposed that dyrosaurids lived as adults in the ocean but reproduced in inland freshwater environments. Remains belonging to small-bodied dyrosaurids from Pakistan were interpreted as juveniles. Their presence in inland deposits was viewed as evidence that dyrosaurids hatched far from the ocean.[9] Recently however, the large-bodied and fully mature dyrosaurids of the Cerrejón Formation have shown that some dyrosaurids lived their entire lives in inland environments, never returning to the coast.[2]

References[edit]

  1. ^ Jouve et al. (2008)
  2. ^ a b Hastings, A.K., Bloch, J. and Jaramillo, C.A. (2011). "A new longirostrine dyrosaurid (Crocodylomorpha, Mesoeucrocodylia) from the Paleocene of north-eastern Colombia: biogeographic and behavioural implications for new-world dyrosauridae". Paleontology 54 (5): 1095–116. doi:10.1111/j.1475-4983.2011.01092.x. Retrieved 14 Sep 2011. 
  3. ^ Greigert, J. (1966). "Description des formations Crétacées et Tertiaires du bassin des Iullemmeden (Afrique occidentale)". Direction des Mines et de la Géologie, Niger. Publication 2: 1–273. 
  4. ^ Reyment, R. (1980). "Biogeography of the Saharan Cretaceous and Paleocene epicontinental transgressions". Cretaceous Research 1: 299–327. doi:10.1016/0195-6671(80)90041-5. 
  5. ^ Buffetaut, E.; Bussert, R.; Brinkmann, W. (1990). "A new nonmarine vertebrate fauna in the Upper Cretaceous of northern Sudan". Berliner Geowissenschaftlische Abhandlungen 120: 183–202. 
  6. ^ Hastings, A. K; Bloch, J. I.; Cadena, E. A.; Jaramillo, C. A. (2010). "A new small short-snouted dyrosaurid (Crocodylomorpha, Mesoeucrocodylia) from the Paleocene of northeastern Colombia". Journal of Vertebrate Paleontology 30 (1): 139–162. doi:10.1080/02724630903409204. 
  7. ^ Head, J. J.; Bloch, J. I.; Hastings, A. K.; Borque, J. R.; Cadena, E. A.; Herrera, F. A.; Polly, P. D.; Jaramillo, C. A. (2009). "Giant boid snake from the Palaeocene neotropics reveals hotter past equatorial temperatures". Nature 457 (7230): 715–717. doi:10.1038/nature07671. PMID 19194448. 
  8. ^ Kanapaux, B. (February 2, 2010). "UF researchers: Ancient crocodile relative likely food source for Titanoboa". University of Florida News. Retrieved February 3, 2010. 
  9. ^ Buffetaut, E. (1978). "Crocodilian remains from the Eocene of Pakistan". Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 156: 262–283. 
  • Barbosa, J.A., Kellner, A.W.A. and Viana, M.S.S. (2008). New dyrosaurid crocodylomorph and evidences for faunal turnover at the K–P transition in Brazil. Proceedings of the Royal Sociey B: Biological Sciences: Firstcite
  • Buffetaut, E. (1985). L'evolution des crocodiliens. Les animaux disparus-Pour la science, Paris 109.
  • Jouve, S.; Bouya, B.; Amaghzaz, M. (2008). "A long-snouted dyrosaurid (Crocodyliformes, Mesoeucrocodylia) from the Paleocene of Morocco: phylogenetic and palaeogeographic implications". Palaeontology 51 (2): 281–294. doi:10.1111/j.1475-4983.2007.00747.x. 
  • Jouve, S.; Iarochène, M.; Bouya, B.; Amaghzaz, M. (2005). "A new dyrosaurid crocodyliform from the Palaeocene of Morocco and a phylogenetic analysis of Dyrosauridae". Acta Palaeontologica Polonica 50 (3): 581–594. 

External links[edit]