Nigerpeton

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Nigerpeton
Temporal range: Changhsingian
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Nigerpeton.jpg
Nigerpeton
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Order:† Temnospondyli
Family:† Cochleosauridae
Subfamily:† Cochleosaurinae
Genus:† Nigerpeton
Sidor et al., 2005
Species
  • Nigerpeton ricqlesi

Nigerpeton (Niger, for the country, and herpeton (Greek), meaning crawler) [1] is an extinct genus of crocodile-like temnospondyls from the late Permian (Changhsingian) period. [2] These temnospondyls lived in modern-day Niger, which was once part of central Pangaea, about 250 million years ago. Nigerpeton is a member of the Cochleosauridae family, a group of edopoid temnospondyl amphibians known from the late Carboniferous (Pennsylvanian) and early Permian (Cisuralian). [2]

Contents

History and discovery

Joulia [3] was the first to publish a notice of vertebrate remains in the Permian Moradi Formation, located in northern Niger in 1960. In the late 1960s, French paleontologists set out on three short expeditions to this formation but only described a single taxon, the captorhinid reptile Moradisaurus grandis. [4] [5] [6] Taquet in 1978 [7] was the first to mention any temnospondyl remains in the Upper Permian rocks in northern Niger but did not describe the fossils. In their 1982 description of the Moradisaurus grandis skull, Ricqlès and Taquet reported finding numerous temnospondyl remains during their three expeditions in the 1960s. [2]

The first specimens of Nigerpeton were collected during fieldwork in 2000, 2003, and 2006, when new fossils representing two new temnospondyl genera were discovered by Sidor et al. [8] [9] These new temnospondyls were named by Sidor et al. [9] as Nigerpeton ricqlesi and Saharastega moradiensis. [1] [2] [10] [11] [12] [13] These specimens were collected from a layer of conglomerate in the Moradi Formation, approximately 20 km west of Arlit in north-central Niger.

Previously, it was believed that edopoids lived only during the late Carboniferous and early Permian periods, and were restricted to a narrow latitudinal band in Europe and America straddling the paleo-equator. [14] [15] [16] The discovery of these new edopoids in the Moradi formation extended the time span of early Euramerican edopoids and created awareness of new African species. [1]

Description

Skull

Skull of Nigerpeton Ricqlesi MNN MOR108 in dorsal view Nigerpeton specimen MNN MOR108.png
Skull of Nigerpeton Ricqlesi MNN MOR108 in dorsal view
Mandible of Nigerpeton Ricqlesi MNN MOR108 in ventral view Nigerpeton Mandible MNN MOR108.jpg
Mandible of Nigerpeton Ricqlesi MNN MOR108 in ventral view

When viewed dorsally, the Nigerpeton skull is triangular, a feature present in temnospondyl forms, and somewhat elongated in shape. The full skull length ranges from 45 cm to a midline length of 56 cm. Dermal bones are 2 to 6 mm in thickness. Along the lateral margins, the Nigerpeton skull is straight until it hits the external naris where lateral bulges are visible. This is a distinctive characteristic in Chochleosaurine. The orbits on Nigerpeton are located in the posterior and are dorsally elevated, with wide spacing in between the orbits on the roof of the skull. Due to the posterior positioning of the orbits, the skull has a very elongated preorbital region along with a short postorbital region, a distinctive condition of cochleosaurids. [14] Nigerpeton holds a record for the longest preorbital region among edopoids, corresponding to more than 80% of its skull length. [2] The tip of a Nigerpeton snout is rounded and pierced by two paired circular anterior cavities for positioning of the symphyseal tusks, a distinct feature in Nigerpeton. Anteriorly, the skull decreases in height, resulting in a flat snout with the external nostril rims elevated above the snout. Other features seen in the skulls are deep and wide longitudinal canals, covered by pronounced longitudinal ridges. [2]

Nigerpeton possesses a honey-comb pattern as an ornament trait on the roof of its skull and its mandible, as well as alternating and elongated ridges and groove ornamentation at the periphery and reaching toward the bone. This ridge and groove ornamentation has been suggestive of areas that experience intensive growth, for instance, the premaxillary, maxillary, and nasal regions which other edopids experience. [2]

A lateral line system is visible in Nigerpeton during the adult stage, a sensory system that is only found in aquatic vertebrates. There are canals 3–10 mm wide and 3–6 mm deep located on the external surface of the skull, as well as preorbital canals on the anterior part of the snout. A depression located posteromedial to the anterior paired cavities could be indication of transverse prenarial sulus. [2]

Post-cranial skeleton

Behind the Nigerpeton skull, an atlas was found consisting of a 41 mm high and 47 mm wide, well-ossified, and disk-shaped intercentrum. The intercentrum has a subtriangular profile measuring 21 mm in ventral length and shows a feasible attachment surface for the pluerocentrum on its right medial side. The posterior face is straight to convex while the anterior face is concaved. [2]

About a meter from where one of the Nigerpeton fossils was located, three presacral vertebrae along with their associated ribs and an isolated femur were found. This vertebra consists of isolated neural arches, the usual shape of temnospondyls. The prezygapophyses are well developed with their contact face with the corresponding postzygapophyses being very elongated. [2] Neural spines are elongated and posterodorsally oriented. Their lateral crests end in relatively smooth dorsolateral apophyses, which are a usual character in adult temnospondyls. [17] The transverse processes is said to extend between 90 and 140 degrees from the body arch. Relative to Nigerpeton's small sized ribs and slight curvature this suggests the vertebrae be anteriorly located alongside the vertebral column. [2]

Paleobiology

Feeding ecology

Nigerpeton's unique dentation suggests a highly carnivorous ecology. Even though complete Nigerpeton teeth are not available, the visible tooth row shows the dentation was usually rounded in cross-section like in non-stereospondyl temnospondyls. Nigerpeton’s great heterodonty such as the numerous and differently sized marginal and palatal tusks is great among temnospondyls and is likely associated with the capability to catch and sustain prey in the mouth before swallowing. [2]

Classification

Nigerpeton belongs to the clade Cochleosauridae, a subdivision of the greater clade Edopoidea. Edopoidea belongs to the clade Temnospondyli so there are many cranial features that unite Nigerpeton to the basal temnospondyl clade Edopoidea. [2]

The cladogram below shows the relationships between these clades based on Sidor et al., 2005 [1] and Steyer et al., 2006, [2] which were based on the matrix of Sequeria 2004 [15] who proposed a phylogeny of 17 basal temnospondyls constructed from an analysis of 61 characters. [1] [2]

Edopoidea

Paleoenviroment

All Nigerpeton specimens were retrieved from the upper one-third of the Moradi Formation located in Arlit, Niger, a late Permian formation approximately 259 to 252 Ma. During this geologic period, the region was part of Central Pangea. During the Late Permian, desert-like conditions replaced the previous moderate climate according to geologic data and climate simulations. [18] [19] [20] Recent work exhibits that arid to hyperarid conditions occurred during Moradi deposition. [21] [22]

Related Research Articles

<span class="mw-page-title-main">Temnospondyli</span> Ancestors of modern amphibians adapted to life on land

Temnospondyli or temnospondyls is a diverse ancient order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carboniferous, Permian and Triassic periods, with fossils being found on every continent. A few species continued into the Jurassic and Early Cretaceous periods, but all had gone extinct by the Late Cretaceous. During about 210 million years of evolutionary history, they adapted to a wide range of habitats, including freshwater, terrestrial, and even coastal marine environments. Their life history is well understood, with fossils known from the larval stage, metamorphosis and maturity. Most temnospondyls were semiaquatic, although some were almost fully terrestrial, returning to the water only to breed. These temnospondyls were some of the first vertebrates fully adapted to life on land. Although temnospondyls are amphibians, many had characteristics such as scales and armour-like bony plates that distinguish them from the modern soft-bodied lissamphibians.

<i>Rhinesuchus</i> Extinct genus of temnospondyls

Rhinesuchus is a large temnospondyl. Remains of the genus are known from the Permian of the South African Karoo Basin's Tapinocephalus and Cistecephalus assemblage zones, both belonging to the Beaufort Group. The skull of Rhinesuchus had a flat triangular shape with blunt snout similar to some of the other large temnospondyls, and had a palate filled with small sharp teeth, suggesting that it hunted fish. Also, the small eyes were on top of the head suggesting that it approached its prey from below.

<i>Cochleosaurus</i> Extinct genus of temnospondyls

Cochleosaurus (“spoon lizard”, from the Latin cochlear "spoon" and Greek sauros “lizard”_ were medium-sized edopoid temnospondyls that lived in Euramerica during the Muscovian period. Two species, C. bohemicus and C. florensis, have been identified from the fossil record.

<i>Eryosuchus</i> Extinct genus of temnospondyls

Eryosuchus is an extinct genus of capitosauroid temnospondyl from the Middle Triassic of northern Russia. It was a very large predator: the largest specimen known could reach up to 3.5 m (11.5 ft) in length, with a skull over 1 m long.

<i>Edops</i> Extinct genus of amphibians

Edops is an extinct genus of temnospondyl amphibian from the Late Carboniferous - Early Permian periods. Unlike more advanced temnospondyls of the time, such as Eryops, Edops exhibited an archaic pattern of palatal bones, and still possessed various additional bones at the back of the skull. Edopoids also had particularly big premaxillae and proportionally small external nostrils. Within the clade, the most basal member seems to be Edops from the Early Permian Archer City Formation of the US, a broad-skulled animal with large palatal teeth.

<i>Capetus</i> (amphibian) Extinct genus of amphibians

Capetus is an extinct genus of temnospondyl from the Upper Carboniferous of the Czech Republic. It reached a length of 150 cm.

<i>Saharastega</i> Extinct genus of amphibians

Saharastega is an extinct genus of basal temnospondyl which lived during the Late Permian period, around 251 to 260 million years ago. Remains of Saharastega, discovered by paleontologist Christian Sidor at the Moradi Formation in Niger, were described briefly in 2005 and more comprehensively in 2006. The description is based on a skull lacking the lower jaws.

<i>Chenoprosopus</i> Extinct genus of temnospondyls

Chenoprosopus is a genus of extinct cochleosauridae that lived during late Carboniferous and early Permian periods. Two known species of Chenoprosopus are C. milleri and C. lewisi. Chenoprosopus lewisi was described in the basis of a virtually complete skull with maximum skull length of 95 mm. It is significantly smaller than Chenoprosopus milleri and was differentiated from that taxon by Hook (1993) based on sutural patterns of the skull roof. Hook also mentioned the reduced size of the vomerine tusks differentiated C. lewisi from C. milleri, but the different size of these tusks may be different ontogenetic stages of growth. Many of other cochleosaurids from the same time period have an elongated vomer and wide and elongate choana. However, Chenoprosopus is distinguished by its more narrowly pointed snout and separation between the nasal from the maxilla by the broad lacrimal-septomaxilla contact.

<span class="mw-page-title-main">Cochleosauridae</span> Extinct family of temnospondyls

Cochleosauridae is a family of edopoid temnospondyl amphibians, among the most basal of temnospondyls. Most members of this family are known from the late Carboniferous (Pennsylvanian) and early Permian (Cisuralian) of Europe and North America, though Nigerpeton is known from the Late Permian (Lopingian) of Niger in North Africa.

<i>Microposaurus</i> Extinct genus of amphibians

Microposaurus is an extinct genus of trematosaurid temnospondyl. Fossils are known from the Cynognathus Assemblage Zone of the Beaufort Group in South Africa and the Rouse Hill Siltstone of Australia that date back to the Anisian stage of the Middle Triassic. These aquatic creatures were the short snouted lineage from Trematosaurinae.

<i>Rhineceps</i> Extinct genus of temnospondyls

Rhineceps is an extinct genus of temnospondyl amphibian in the family Rhinesuchidae. Rhineceps was found in Northern Malawi in Southern Africa known only from its type species R. nyasaensis. Rhineceps was a late Permian semi-aquatic carnivore that lived in streams, rivers, lakes or lagoons. Rhineceps is an early divergent Stereopondyl within the family Rhinesuchidae, which only existed in the late Permian (Lopingian) and failed to survive the Permian-Triassic extinction unlike other stereospondyl families.

Wellesaurus is an extinct genus of mastodonsauroid temnospondyl. They were amphibious carnivores that lived in freshwater environments.

Christian Alfred Sidor is an American vertebrate paleontologist. He is currently a Professor in the Department of Biology, University of Washington in Seattle, as well as Curator of Vertebrate Paleontology and Associate Director for Research and Collections at the Burke Museum of Natural History and Culture. His research focuses on Permian and Triassic tetrapod evolution, especially on therapsids.

<i>Adamanterpeton</i> Extinct genus of temnospondyls

Adamanterpeton is a genus of Edopoid Temnospondyl within the family Cochleosauridae. The type species A. ohioensis was named in 1998 and is currently the only known species within this genus. Adamanterpeton is rare in the Linton vertebrate assemblage, with other amphibians like Sauropleura, Ophiderpeton, and Colosteus being more common. Unlike other Linton vertebrates, Adamanterpeton may have been adapted to a terrestrial lifestyle.

<span class="mw-page-title-main">Edopoidea</span> Extinct superfamily of amphibians

Edopoidea is a clade of primitive temnospondyl amphibians including the genus Edops and the family Cochleosauridae. Edopoids are known from the Late Carboniferous and Early Permian of North America and Europe, and the Late Permian of Africa. They are among the most basal temnospondyls, and possess a number of primitive features that were lost in later members of the group.

<i>Bunostegos</i> Genus of reptiles (fossil)

Bunostegos is an extinct genus of pareiasaur parareptile from the Late Permian of the Agadez Region in Niger. The type species, Bunostegos akokanensis, was named from the Moradi Formation in 2003. It was a cow-sized animal with a distinctive skull that had large bony knobs, similar in form to those of other pareiasaurs but far larger. The species appears to have lived in a desert in the centre of the supercontinent of Pangaea.

The Moradi Formation is a geological formation in Niger. It is of Late Permian age. It is informally divided into three subunits. The lower portion of the formation consists of red mudstone, with muddy calcareous sandstone and quartz-granlule conglomerate present as lenses. The middle portion consists of muddy siltstone in thick beds interbedded with red argillaceous sandstone. The lower two thirds of the upper portion of the formation consist of red siltstone intercalated with channel lag intraformational conglomerates, while the upper third consists of barchanoid shaped lenses of conglomeratic sandstone with ventifacts. These facies are indicatived of deposition under arid conditions, with less than 300 millimetres (12 in) of annual rainfall in the Central Pangean desert, with annual temperatures of 30 to 35 °C, but with ephemeral water presence including lakes.

Macrerpeton is a genus of edopoid temnospondyl within the family Cochleosauridae. It contains a single species, Macrerpeton huxleyi. It was discovered in the fossil-rich Allegheny Formation of Linton, Ohio.

<i>Moradisaurus</i> Extinct genus of large captorhinid reptile

Moradisaurus is an extinct genus of large captorhinid reptile, with a single species Moradisaurus grandis, known from the late Permian (Lopingian) aged Moradi Formation of Niger. It is the largest captorhinid known, estimated to have reached a snout-vent length of over two metres. Similar to other members of Moradisaurinae, it possessed multiple tooth rows, which is associated with a high-fiber herbivorous diet.

References

  1. 1 2 3 4 5 Sidor, C.A., O’Keefe, F.R., Damiani, R., Steyer, J.S., Smith, R.M.H., Larsson, H.C.E., Sereno, P.C., Ide, O., Maga, A., 2005. Permian tetrapods from the Sahara show climate-controlled endemism in Pangaea. Nature434, 886–889. doi : 10.1038/nature03393
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Steyer, J.S., Damiani, R., Sidor, C.A., O’Keefe, F.R., Larsson, H.C.E., Maga, A., Ide, O., 2006. The vertebrate fauna of the Upper Permian of Niger. IV. Nigerpeton ricqlesi (Temnospondyli: Cochleosauridae), and the edopoid colonization of Gondwana. J. Vert. Paleontol. 26, 18–28. doi : 10.1671/0272-4634(2006)26[18:TVFOTU 2.0.CO;2]
  3. ↑ Joulia, F., 1960. Mission de prospection de la bordure occidentale de l’Aïr (République du Niger). Bureau de recherches géologiques et minières, Dakar.
  4. ↑ Ricqlès de,A., Taquet, P., 1982. La Faune de vertébrés du Permien supérieur du Niger. I. Le captorhinomorphe Moradisaurus grandis (Reptilia, Cotylosauria). Ann. Paleontol. (Vert.–Invert.) 68, 33–106
  5. ↑ Taquet, P., 1967. Découvertes paléontologiques récentes dans le Nord du Niger. Problèmes actuels de paléontologie – évolution des Vertébrés. Centre national de la recherche scientifique, Paris, pp. 415–418
  6. ↑ Taquet, P., 1969. Première découverte en Afrique d’un Reptile captorhinomorphe (Cotylosaurien). C. R. Acad. Sci. Paris, Ser. D 268, 779–781.
  7. ↑ Taquet, P. 1978. Niger et Gondwana. Annales de la Société Géologique du Nord 97:337–341.
  8. ↑ Sidor, C. A., H. C. E. Larsson, J. S. Steyer, F. R. O’Keefe, and R. M. H. Smith. 2003b. Late Permian tetrapods from the Sahara. Journal of Vertebrate Paleontology 23(3, supplement):97A. doi : 10.1080/02724634.2003.10010538
  9. 1 2 Sidor, C. A., F. R. O’Keefe, H. C. E. Larsson, R. Damiani, J. S. Steyer, and R. M. H. Smith. 2004. Tetrapod biogeography during the Permian: new insights from West Africa. Geoscience Africa 2004 Abstracts:595.
  10. ↑ Damiani, R., Sidor, C.A., Steyer, J.S., Smith, R.M.H., Larsson, H.C.E., Maga, A., Ide, O., 2006. The vertebrate fauna of the Upper Permian of Niger. V. The primitive temnospondyl Saharastega moradiensis. J. Vert. Paleontol. 26, 559–572. doi : 10.1080/02724634.2006.10010015
  11. ↑ Sidor, C.A., Blackburn, D.C., Gado, B., 2003. The vertebrate fauna of the Upper Permian of Niger – II, preliminary description of a new pareiasaur. Palaeontol. Afr. 39, 45–52.1]2
  12. ↑ Smiley, T.M., Sidor, C.A., Ide, O., Maga, A., 2008. Vertebrate fauna of the Upper Permian of Niger.VI. First evidence of a gorgonopsian therapsid. J. Vert. Paleontol. 28, 543–547 doi : 10.1671/0272-4634(2008)28[543:TVFOTU 2.0.CO;2]
  13. ↑ Tsuji, L.A., Sidor, C.A., Steyer, J.S., Smith, R.M.H., Tabor, N.J., Ide, O., 2013. The vertebrate fauna of the Upper Permian of Niger –VII. Cranial anatomy and relationships of Bunostegos akokanensis (Pareiasauria). J. Vert. Paleontol. 33, 747–763. doi : 10.1080/02724634.2013.739537
  14. 1 2 Milner, A. R., and S. E. K. Sequeira. 1998. A cochleosaurid temnospondyl amphibian from the Middle Pennsylvanian of Linton, Ohio, U.S.A. Zoological Journal of the Linnean Society 122:261–290. doi : 10.1111/j.1096-3642.1998.tb02532.x
  15. 1 2 Sequeira, S. E. K. 2004. The skull of Cochleosaurus bohemicus Fricˇ, a temnospondyl from the Czech Republic (Upper Carboniferous) and cochleosaurid interrelationships. Transactions of the Royal Society of Edinburgh: Earth Sciences 94:21–43. doi : 10.1017/S0263593300000511
  16. ↑ Milner, A. R. in Palaeozoic vertebrate biostratigraphy and biogeography (ed. Long, J. A.) 324–353 (Belhaven, London, 1993).
  17. ↑ Steyer, J. S. 2000. Ontogeny and phylogeny in temnospondyls: a new method of analysis. Zoological Journal of the Linnean Society 130: 449–467. doi : 10.1111/j.1096-3642.2000.tb01637.x
  18. ↑ Gibbs, M. T. et al. Simulations of Permian climate and comparisons with climate-sensitive sediments. J. Geol. 110, 33–55 (2002). doi : 10.1086/324204
  19. ↑ Rees, P. M.et al. Permian phytogeographic patterns and climate data/model comparisons. J. Geol. 110, 1–31 (2002) doi : 10.1086/324203
  20. ↑ Kiehl, J.T., Shields, C.A., 2005. Climate simulation of the Latest Permian: implications for mass extinction. Geology 33, 757–760. doi : 10.1130/G21654.1
  21. ↑ Smith, R.M.H., Sidor, C.A., Tabor, N.J., Steyer, J.S., Chaney, D.S., 2009. Vertebrate taphonomy and ichnology of a Permian “wet desert” in central Pangea. Palaeontol. Afr. 44, 179–183.
  22. ↑ Tabor, N.J., Smith, R.M.H., Steyer, J.S., Sidor, C.A., Poulsen, C.J., 2011. The Permian Moradi Formation of northern Niger: paleosol morphology, petrography andmineralogy. Palaeogeogr. Palaeoclimatol. Palaeoecol. 299, 200–213 doi : 10.1016/j.palaeo.2010.11.002


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