Pakasuchus

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Pakasuchus
Temporal range: Cenomanian–Campanian
Pakasuchus.jpg
Life restoration of Pakasuchus.
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauria
Clade: Pseudosuchia
Clade: Crocodylomorpha
Clade: Crocodyliformes
Clade: Notosuchia
Clade: Ziphosuchia
Genus: Pakasuchus
O’Connor et al., 2010
Species
  • P. kapilimaiO'Connor et al., 2010 (type)

Pakasuchus is a genus of notosuchian crocodyliform distinguished by its unusual mammal-like appearance, including mammal-like teeth that would have given the animal the ability to chew. It also had long, slender legs and a doglike nose. Fossils have been found in the Galula Formation of Rukwa Rift Basin of southwestern Tanzania, and were described in 2010 in the journal Nature . [1] Pakasuchus is originally considered to lived approximately 105 million years ago, in the mid-Cretaceous, [2] but later age of site is reconsidered to the late Cretaceous, Cenomanian to Campanian instead. [3] The type species is P. kapilimai. Pakasuchus means "cat crocodile" (paka meaning "cat" in Kiswahili) in reference to its catlike skull. [4]

Description

Dentition of Pakasuchus. Gray areas are restored parts of the skull missing in the holotype. Pakasuchus dentition.svg
Dentition of Pakasuchus. Gray areas are restored parts of the skull missing in the holotype.

Pakasuchus was around 50 centimetres (20 in) long. Like all notosuchians, it was an active terrestrial animal. It probably hunted small prey such as insects. It had a short, broad skull somewhat similar in shape to a cat. Unlike living crocodilians, Pakasuchus had distinctive heterodont teeth that varied in shape throughout its jaws. There are large, sharp teeth near the front of the jaws, and broad molar-like teeth at the back of the mouth. While multicuspid teeth are seen in many other notosuchians such as Simosuchus and Yacarerani , they are most complex in Pakasuchus. The molar-like teeth show a level of complexity that matches that of mammals, being able to occlude, or fit with one another, and provide sharp shearing edges for slicing food. [4]

Pakasuchus also differed from modern crocodilians, and many other crocodyliforms, in the reduction of osteoderms covering the body. Small, reduced osteoderms overlie the dorsal vertebrae, but fewer in number and are not as large as those of other notosuchians. However, caudal osteoderms still covered the tail. The loss of osteoderms on the body and retention of them on the tail is unique among crocodyliforms. [4]

Discovery

A complete skeleton of Pakasuchus was found in 2008 in southwestern Tanzania by an international research team funded by the National Science Foundation and the National Geographic Society as part of the Rukwa Rift Basin Project. Remains from six other individuals were later uncovered. [5] The specific name honors Saidi Kapilima, one of the leaders of the Rukwa Rift Basin Project and who helped in the excavation of the specimens. [6]

The most complete specimen includes a nearly complete skull. Because the jaws were closed in this specimen, some of the teeth were obscured. The describers of the specimens used X-ray computed tomography scanning, or CT scanning, to image the teeth. This provided a detailed view of the animal's dentition that could not normally be observed in the specimen. [6]

Phylogeny

Below is a cladogram modified from O’Connor et al., 2010:

Notosuchia  

Paleobiology

Pakasuchus was probably very mammal-like in behavior as well as appearance. The molariform teeth are well suited to shearing food like modern mammalian carnivores (for example, all many species of bears, canids, big cats, hyenas, mustelids, procyonids, mongooses and pinnipeds). In fact, the teeth are so similar to those of mammals that it has led paleontologist Greg Buckley to state "If only isolated teeth had been discovered, without the skull, it is very likely that some of the molariform teeth would have been mistaken for a mammal's." [4]

The relative lack of osteoderms on the body may have been an adaptation for an active terrestrial lifestyle, as it would have lightened the animal. However, the retention of osteoderms on the tail is hard to explain, as they would have been quite heavy. The long legs and slender build would also have made Pakasuchus more agile. [4]

Pakasuchus was probably an herbivore; its dentition was at least as complex as those of modern herbivorous lizards. [7]

Notosuchians were widespread across Gondwana throughout the Cretaceous. Pakasuchus, as well as many other notosuchians, would have filled ecological niches in these areas that were otherwise occupied by mammals in the northern continents. [1] Mammals were relatively uncommon in Gondwana at the time, making it possible for notosuchians to occupy a similar niche. [2]

The Rukwa Rift Basin is known for a rich vertebrate fauna that existed during the Cretaceous. During the Early Cretaceous, the basin was part of a large river system with braided channels and low-lying vegetated floodplains. Several dinosaurs are known from the basin that would have lived alongside Pakasuchus, including large sauropods and theropods. Aquatic crocodyliforms inhabited the rivers along with turtles and fishes. [5]

Related Research Articles

<i>Sarcosuchus</i> Extinct genus of reptiles

Sarcosuchus is an extinct genus of crocodyliform and distant relative of living crocodilians that lived during the Early Cretaceous, from the late Hauterivian to the late Cenomanian, 133 to 93 million years ago of what are now North Africa and South America. The genus name comes from the Greek σάρξ (sarx) meaning flesh and σοῦχος (souchus) meaning crocodile. It was one of the largest pseudosuchians, with the largest specimen of S. imperator reaching approximately 9–9.5 metres (29.5–31.2 ft) long and weighing up to 3.45–4.3 metric tons. It is known from two species; S. imperator from the early Albian Elrhaz Formation of Niger, and S. hartti from the Late Hauterivian of northeastern Brazil. Other material is known from Morocco and Tunisia and possibly Libya and Mali.

<i>Deinosuchus</i> Genus of a giant crocodylian

Deinosuchus is an extinct genus of alligatoroid crocodilian, related to modern alligators and caimans, that lived 82 to 73 million years ago (Ma), during the late Cretaceous period. The name translates as "terrible crocodile" and is derived from the Greek deinos (δεινός), "terrible", and soukhos (σοῦχος), "crocodile". The first remains were discovered in North Carolina in the 1850s; the genus was named and described in 1909. Additional fragments were discovered in the 1940s and were later incorporated into an influential, though inaccurate, skull reconstruction at the American Museum of Natural History. Knowledge of Deinosuchus remains incomplete, but better cranial material found in recent years has expanded scientific understanding of this massive predator.

<i>Doratodon</i> Extinct genus of reptiles

Doratodon is an extinct genus of Late Cretaceous crocodylomorph that may have been a member of the Sebecosuchia. Doratodon was a relatively small animal with ziphodont teeth, meaning the teeth had flattened sides and serrated edges. Two species of Doratodon are known to science: D. carcharidens from Austria and Hungary, the type species; and D. ibericus from Spain. Teeth similar to those of Doratodon are also known from Italy and Romania, though they cannot be confidently assigned to this genus.

<i>Simosuchus</i> Extinct genus of reptiles

Simosuchus is an extinct genus of notosuchian crocodyliforms from the Late Cretaceous of Madagascar. It is named for its unusually short skull. Fully grown individuals were about 0.75 metres (2.5 ft) in length. The type species is Simosuchus clarki, found from the Maevarano Formation in Mahajanga Province, although one isolated multicuspid tooth of this genus was discovered in Kallamedu Formation of India.

<i>Mahajangasuchus</i> Extinct genus of reptiles

Mahajangasuchus is an extinct genus of crocodyliform which had blunt, conical teeth. The type species, M. insignis, lived during the Late Cretaceous; its fossils have been found in the Maevarano Formation in northern Madagascar. It was a fairly large predator, measuring up to 4 metres (13 ft) long.

<i>Anatosuchus</i> Extinct genus of reptiles

Anatosuchus is an extinct genus of notosuchian crocodylomorph discovered in Gadoufaoua, Niger, and described by a team of palaeontologists led by the American Paul Sereno in 2003, in the Journal of Vertebrate Paleontology. Its duck-like snout coincidentally makes it resemble a crocoduck, an imagined hybrid animal with the head of a crocodile and the body of a duck.

<i>Mariliasuchus</i> Extinct genus of reptiles

Mariliasuchus is an extinct genus of Late Cretaceous notosuchian crocodyliforms found near Marilia, Brazil. The first bone remains were found and collected in 1995 by Brazilian paleontologist William Nava, in red rocks from the fossiliferous Adamantina Formation. Four years later, it was described as Mariliasuchus amarali, by Brazilian paleontologists Ismar de Souza Carvalho and Reinaldo J. Bertini.

Malawisuchus is an extinct genus of notosuchian mesoeucrocodylian from the Early Cretaceous Dinosaur Beds of Malawi. It was described in 1997 by Elizabeth Gomani as a member of the family Notosuchidae. The type species is M. mwakasyungutiensis, referring to Mwakasyunguti, the area of northern Malawi where it was found. It was classified as a member of the family Itasuchidae by Carvalho and colleagues in 2004.

Trematochampsidae is an extinct family of mesoeucrocodylian crocodyliforms. Fossils are present from Madagascar, Morocco, Niger, Argentina, and Brazil. Possible trematochampsids have been found from Spain and France, but classification past the family level is indeterminant. The trematochampsids first appeared during the Barremian stage of the Early Cretaceous and became extinct during the late Maastrichtian stage of the Late Cretaceous.

<i>Armadillosuchus</i> Extinct genus of reptiles

Armadillosuchus is an extinct genus of sphagesaurid crocodylomorph. It was described in February 2009 from the late Campanian to early Maastrichtian Adamantina Formation of the Bauru Basin in Brazil, dating to approximately 70 Ma. Armadillosuchus was among the larger and more robust sphagesaurids, with a total length of approximately 2 metres (6.6 ft).

<i>Bergisuchus</i> Extinct genus of reptiles

Bergisuchus is an extinct genus of small sebecosuchian mesoeucrocodylian known primarily from the Eocene Messel Pit in Germany. Few fossils of Bergisuchus have been discovered, only a single incomplete snout, a few partial lower jaws and some teeth. Despite being fragmentary, the jaw bones are enough to indicate that Bergisuchus had a short, deep, narrow snout and serrated teeth, quite unlike the broad flat snouts of modern crocodylians.

<i>Kaprosuchus</i> Genus of crocodyliform from the Late Cretaceous period

Kaprosuchus is an extinct genus of mahajangasuchid crocodyliform. It is known from a single nearly complete skull collected from the Upper Cretaceous Echkar Formation of Niger. The name means "boar crocodile" from the Greek κάπρος, kapros ("boar") and σοῦχος, soukhos ("crocodile") in reference to its unusually large caniniform teeth which resemble those of a boar. It has been nicknamed "BoarCroc" by Paul Sereno and Hans Larsson, who first described the genus in a monograph published in ZooKeys in 2009 along with other Saharan crocodyliformes such as Anatosuchus and Laganosuchus. The type species is K. saharicus.

<i>Sebecus</i> Extinct genus of reptiles

Sebecus is an extinct genus of sebecid crocodylomorph from Eocene of South America. Like other sebecosuchians, it was entirely terrestrial and carnivorous. The genus is currently represented by two species, the type S. icaeorhinus and S. ayrampu. Several other species have been referred to Sebecus, but were later reclassified as their own genera.

<i>Galulatherium</i> Fossil taxon

Galulatherium is an extinct genus of possibly gondwanathere mammal, from the Late Cretaceous (Turonian-Campanian)-aged Galula Formation of Tanzania. It is known solely from the type specimen TNM 02067 a fragmentary fossil dentary. The short, deep bone is about 19.5 mm (0.77 in) long, but the back part is broken off. It contains a large, forward-inclined incisor with a root that extends deep into the jaw, separated by a diastema (gap) from five cheekteeth. Very little remains of the teeth, but enough to determine that they are hypsodont (high-crowned). The third cheektooth is the largest and the roots of the teeth are curved. First described in 2003, TNM 02067 has been tentatively identified as a sudamericid—an extinct family of high-crowned gondwanathere mammals otherwise known from South America, Madagascar, India, and Antarctica. If truly a gondwanathere, it would be the only African member of the group and may be the oldest. The describers could not exclude other possibilities, such as that the jaw represents some mammalian group known only from younger, Cenozoic times. In 2019 the fossil was CT scanned, which revealed additional details of the specimen.

<i>Barreirosuchus</i> Extinct genus of reptiles

Barreirosuchus is an extinct genus of trematochampsid notosuchian known from the Late Cretaceous of São Paulo State, southeastern Brazil. It contains a single species, Barreirosuchus franciscoi. It is most closely resembles Caririsuchus camposi from the Araripe Basin and Itasuchus jesuinoi also from the Bauru Basin, and shares with them several synapomorphies.

Rukwasuchus is an extinct genus of peirosaurid crocodyliforms known from the middle Cretaceous Galula Formation of southwestern Tanzania. It contains a single species, Rukwasuchus yajabalijekundu.

Shingopana is a genus of titanosaurian sauropod from the Upper Cretaceous Galula Formation of Tanzania. It is known from only the type species, S. songwensis. Gorscak & O'Connor's phylogenetic testing suggest Shingopana is more closely related to the South American titanosaur family of Aeolosaurini than any of the titanosaurs found so far in North & South Africa.

The Galula Formation is a geological formation located south of Lake Rukwa in Tanzania, part of the Red Sandstone Group of the Rukwa Rift Basin. Along with the unconformably overlying Oligocene Nsungwe Formation. It is divided into two members, the lower Mtuka Member and the upper Namba Member.

Barrosasuchus is a genus of peirosaurid notosuchian from the Santonian of Argentina and part of the extensive peirosaurid record of Late Cretaceous Patagonia. It contains one species, Barrosasuchus neuquenianus. B. neuquenianus is known from an almost complete skull and the majority of the articulated postcranial skeleton, making it the best preserved Patagonian peirosaurid.

<i>Confractosuchus</i> Extinct genus of eusuchian

Confractosuchus is a genus of extinct eusuchian crocodyliform from the Cretaceous Winton Formation of Australia. Described as a macro-generalist, Confractosuchus was found with the bones of a juvenile ornithopod dinosaur in its abdomen. It currently contains a single species, Confractosuchus sauroktonos, which literally means "broken dinosaur killer."

References

  1. 1 2 O’Connor, P.M.; Sertich, J.W.; Stevens, N.J.; Roberts, E.M.; Gottfried, M.D.; Hieronymus, T.L.; Jinnah, Z.A.; Ridgely, R.; Ngasala, S.E.; Temba, J. (2010). "The evolution of mammal-like crocodyliforms in the Cretaceous Period of Gondwana". Nature. 466 (7307): 748–751. Bibcode:2010Natur.466..748O. doi:10.1038/nature09061. PMID   20686573. S2CID   4405106.
  2. 1 2 Ker Than (4 August 2010). "Fossil "Cat Crocodile" Had Mammal-like Teeth". National Geographic Daily News. Archived from the original on August 5, 2010.
  3. Widlansky, Sarah J.; Clyde, William C.; O'Connor, Patrick M.; Roberts, Eric M.; Stevens, Nancy J. (2018-03-01). "Paleomagnetism of the Cretaceous Galula Formation and implications for vertebrate evolution". Journal of African Earth Sciences. 139: 403–420. doi: 10.1016/j.jafrearsci.2017.11.029 . ISSN   1464-343X.
  4. 1 2 3 4 5 Bonner, John (4 August 2010). "Tooth to tail oddities in ancient croc". Nature News. doi:10.1038/news.2010.389.
  5. 1 2 "Mammal-Like Crocodile Fossil Found in East Africa, Scientists Report". ScienceDaily. August 4, 2010.
  6. 1 2 Young, Ed (4 August 2010). "Pakasuchus – the crocodile that's trying to be a mammal". Not Exactly Rocket Science. Discover Magazine. Retrieved 8 August 2010.
  7. "Repeated Evolution of Herbivorous Crocodyliforms during the Age of Dinosaurs". ResearchGate. Retrieved 2019-09-01.