Anoualerpeton
| Anoualerpeton | ||||||||||
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Holotype of Anoualerpeton unicus , an isolated, incomplete right premaxillary. Left: lingual view. Right: laterolingual view. |
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| Temporal occurrence | ||||||||||
| Middle Jurassic ( Bathonian ) to Lower Cretaceous (? Berriasium ) | ||||||||||
| 168.3 to 139.3 million years | ||||||||||
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| Systematics | ||||||||||
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| Scientific name | ||||||||||
| Anoualerpeton | ||||||||||
| Gardner et al., 2003 | ||||||||||
Anoualerpeton is a genus of the Albanerpetontidae family, a completely extinct subgroup of modern amphibians ( Lissamphibia ). It is known so far from two species, Anoualerpeton priscus and Anoualerpeton unicus , from the Central Jurassic ( Bathon ) of Great Britain and from the Lower Cretaceous (? Berrias ) of Morocco.
etymology
The name "Anoualerpeton" is composed of Anoual, the name of a city in the eastern High Atlas (Morocco), in the relative vicinity of which the type material of the type species Anoualerpeton unicus was found, and the ancient Greek word ἑρπετόν herpeton , which means 'lower land vertebrate' means (see → Herpetology ) and is often used in generic names of fossil amphibians. The epithets “priscus” and “unicus” mean “old” and “only”, which refers to the fact that Anoualerpeton priscus is the geologically oldest Albanian petontid and Anoualerpeton unicus is the only Albanian petontid that occurs on the former large southern continent of Gondwana .
features
Anoualerpeton has no unique selling points ( autapomorphies ), but is characterized by a mosaic of features that occur either in Albanian peton , but not Celtedens or in Celtedens , but not Albanian peton . The occlusal edge of the maxillary and dentals is convex in the labial or lingual view and the teeth in the middle third of the row of teeth are longest, both of which are otherwise only known from the Albanian peton nexuosus . The processus internasalis of the azygic frontal, d. H. the end of the bone that has emerged from the fusion of the originally paired frontalia and which is flanked by the nasals, pointing towards the tip of the snout, tapers to a point. The lateral edges of this process are designed as a kind of groove into which the edges of the nasals reach (cf. → tongue-and-groove connection ), both of which occur in Albanian peton but not in Celtedens . In addition, the length-width ratio of the frontal is relatively large and the frontal is more bell-shaped than triangular in the dorsal and ventral view, features that Anoualerpeton only shares with Celtedens , but not with Albanian peton.
The two Anoualer peton species differ primarily in terms of the location of the suprapalatal pit. This is a depression in the inside (lingual side) of that part of the premaxillary that reaches up to the roof of the skull (pars dorsalis). In Anoualerpeton priscus , the suprapalatal pit is located in the medial edge of the outer nostril. In Anoualerpeton unicus, on the other hand, it lies further mediad, outside the border of the outer nostril.
Fossil record and conservation
As is common for Albanian petontids, the remains of Anoualerpeton all come from so-called microvertebrate localities, that is, they are isolated, relatively small bones that were obtained by slurrying and sieving samples of the sedimentary rock in which they were embedded. So far, Anoualerpeton is only known from the type localities of the two species.
The older species Anoualerpeton priscus comes from the Kirtlington Mammal Bed ("Kirtlington mammal layer") in the lowest part of the Forest Marble Formation of the Bathons of Central England . The Kirtlington Mammal Bed is the richest microvertebrate deposit in Washford Quarry, a neglected limestone quarry west of Kirtlington, about 15 kilometers north of Oxford . It consists of a weakly consolidated clayey marl , which was probably deposited in a swampy environment and also contains the teeth of dinosaurs and early Mammaliaformes . The material from Kirtlington classified as Anoualerpeton priscus was previously assigned to the genera Albanerpeton and Celtedens .
The younger species Anoualerpeton unicus , which is also a type of the genus, was identified in the microvertebrate fauna of the locality Ksar Met Lili in the eastern High Atlas. The locality is in the south of the Talsint province of Morocco, approx. 100 kilometers east of the city of Anoual. The deposit is located in a lens of a non-marine limestone , which is embedded in marine deposits in the upper part of the so-called Couches Rouges ("red layers"). These marine sediments have been dated uncertainly to Berrias using coccolithophores . Dinosaurs are also found in Ksar Met Lili and, due to their lower geological age, also representatives of the mammalian crown group ( Mammalia ).
Systematics
According to previous knowledge, Anoualerpeton occupies the most basic position within the Albanerpetontiden, which is consistent with its stratigraphic range. The following cladogram shows a current (2013) hypothesis of the kinship relationships of the Albanerpetontiden.
| Albanerpetontidae |
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literature
- James D. Gardner, Susan E. Evans, Denise Sigogneau-Russell: New albanerpetontid amphibians from the Early Cretaceous of Morocco and Middle Jurassic of England. Acta Palaeontologica Polonica. Vol. 48, No. 2, 2003, pp. 301-319 ( online )
- James D. Gardner, Madelaine Böhme: Review of the Albanerpetontidae (Lissamphibia), with Comments on the Paleoecological Preferences of European Tertiary Albanerpetontids. Pp. 178-218 in: Julia T. Sankey, Sven Baszio (eds.): Vertebrate Microfossil Assemblages - Their Role in Paleoecology and Paleobiogeography. University of Indiana Press, Bloomington (IN) 2008, ISBN 978-0-253-34927-9 ( PDF )
Individual evidence
- ^ Susan E. Evans, Andrew R. Milner: Middle Jurassic microvertebrate assemblages from the British Isles. Pp. 303-321 in: Nicholas C. Fraser, Hans-Dieter Sues (Ed.): In the Shadow of the Dinosaurs: Early Mesozoic Tetrapods. Cambridge University Press, Cambridge (UK) 1994, ISBN 0-521-45242-2 , pp. 305 f.
- ↑ Denise Sigogneau-Russell, Susan E. Evans, Jay F. Levine, Dale A. Russell: The Early Cretaceous microvertebrate locality of Anoual, Morocco: A glimpse at the small vertebrate assemblages of Africa. In: Spencer G. Lucas, James I. Kirkland, John W. Estep: Lower and Middle Cretaceous terrestrial ecosystems. New Mexico Museum of Natural History Bulletin. Vol. 14, 1998, pp. 177-182 ( online )
- ↑ Steven C. Sweetman, James D. Gardner: A new albanerpetontid amphibian from the Barremian (Early Cretaceous) Wessex Formation of the Isle of Wight, southern England. Acta Palaeontologica Polonica. Vol. 58, No. 2, 2013, pp. 295-324, doi : 10.4202 / app.2011.0109
Web links
- Anoualerpeton in the Paleobiology Database