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Taxonomic composition and trophic structure of the continental bony fish assemblage from the early late cretaceous of Southeastern Morocco.

Cavin L, Boudad L, Tong H, Läng E, Tabouelle J, Vullo R - PLoS ONE (2015)

Bottom Line: The Kem Kem assemblage is characterized by taxa of proportionally large body size, and by a higher average trophic level than the trophic level of the extant compared freshwater ecosystems, but lower than for the extant marine ecosystems.These results should be regarded with caution because they rest on a reconstructed assemblage known mostly by fragmentary remains.They reinforce, however, the ecological oddities already noticed for this mid-Cretaceous vertebrate ecosystem in North Africa.

View Article: PubMed Central - PubMed

Affiliation: Département de géologie et paléontologie, Muséum d'histoire naturelle de Genève, CP 6434, 1211, Geneva 6, Switzerland.

ABSTRACT
The mid-Cretaceous vertebrate assemblage from south-eastern Morocco is one of the most diversified continental vertebrate assemblages of this time worldwide. The bony fish component (coelacanths, lungfishes and ray-finned fishes) is represented by relatively complete specimens and, mostly, by fragmentary elements scattered along 250 kilometres of outcrops. Here we revisit the bony fish assemblage by studying both isolated remains collected during several fieldtrips and more complete material kept in public collections. The assemblage comprises several lungfish taxa, with the first mention of the occurrence of Arganodus tiguidiensis, and possibly two mawsoniid coelacanths. A large bichir cf. Bawitius, is recorded and corresponds to cranial elements initially referred to 'Stromerichthys' from coeval deposits in Egypt. The ginglymodians were diversified with a large 'Lepidotes' plus two obaichthyids and a gar. We confirm here that this gar belongs to a genus distinctive from Recent gars, contrary to what was suggested recently. Teleosteans comprise a poorly known ichthyodectiform, a notopterid, a probable osteoglossomorph and a large tselfatiiform, whose cranial anatomy is detailed. The body size and trophic level for each taxon are estimated on the basis of comparison with extant closely related taxa. We plotted the average body size versus average trophic level for the Kem Kem assemblage, together with extant marine and freshwater assemblages. The Kem Kem assemblage is characterized by taxa of proportionally large body size, and by a higher average trophic level than the trophic level of the extant compared freshwater ecosystems, but lower than for the extant marine ecosystems. These results should be regarded with caution because they rest on a reconstructed assemblage known mostly by fragmentary remains. They reinforce, however, the ecological oddities already noticed for this mid-Cretaceous vertebrate ecosystem in North Africa.

No MeSH data available.


Aerial photograph (A) and geological simplified map (B) of the studied area.The localities mentioned in the text are in black font and the towns and cities are in white font in A. C, Simplified stratigraphic section with the approximate position of the localities. Only the sites situated in the Ifezouane Formation are discussed in the text.
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pone.0125786.g001: Aerial photograph (A) and geological simplified map (B) of the studied area.The localities mentioned in the text are in black font and the towns and cities are in white font in A. C, Simplified stratigraphic section with the approximate position of the localities. Only the sites situated in the Ifezouane Formation are discussed in the text.

Mentions: The continental or brackish deposits from the early Cenomanian of the Ifezouane Formation, sometimes gathered with the Aoufous Formation within the Kem Kem beds, have yielded a very rich assemblage including terrestrial, aquatic and aerial vertebrates [1]. The fossils are located in outcrops extending along more than 250 kilometres, which marks the landscape as the basement of a cliff over hanged by a calcareous plateau (hamada), which is formed by the limestone Akrabou Formation. The Ifezouane Formation is composed mainly of detritic sandstone characterised by cross-stratified structures and channel structures filled with microconglomerates. The Aoufous Formation is composed mainly of clayey sandstones and green marls with gypsum and contains few fossils, except in the Djbel Oum Tkout locality (also called OT1 assemblage [2]), whose assemblage is not discussed in this paper. The overhanging Akrabou Formation is a calcareous series corresponding to the settlement of marine environment. The shallow marine fish and invertebrate assemblage from Agoult is located at the base of the Formation, in an area that has also yielded vertebrate remains in the underlying Ifezouane Formation (Gara Sbâa). The Goulmima assemblage is located higher in the stratigraphical series and is situated in the northern part of the basin. The Cenomanian-Turonian boundary is located in the lower part of the Akrabou Formation. The Goulmima assemblage is well dated to the early Turonian on the basis of ammonites, but the Agoult assemblage is regarded as either Late Cenomanian or Early Turonian. Fish taxa from both marine localities are not discussed here, except for a comparison of trophic webs of the Goulmima assemblage with the Kem Kem assemblage (see below). The geographical distribution and the approximate stratigraphic location of these assemblages are presented in Fig 1. Description of the succession of the fish assemblages is presented in a recent overview of the Moroccan Post-Palaeozoic bony fish record [3], and here we focus on new material collected in the Ifezouane Fm.


Taxonomic composition and trophic structure of the continental bony fish assemblage from the early late cretaceous of Southeastern Morocco.

Cavin L, Boudad L, Tong H, Läng E, Tabouelle J, Vullo R - PLoS ONE (2015)

Aerial photograph (A) and geological simplified map (B) of the studied area.The localities mentioned in the text are in black font and the towns and cities are in white font in A. C, Simplified stratigraphic section with the approximate position of the localities. Only the sites situated in the Ifezouane Formation are discussed in the text.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4446216&req=5

pone.0125786.g001: Aerial photograph (A) and geological simplified map (B) of the studied area.The localities mentioned in the text are in black font and the towns and cities are in white font in A. C, Simplified stratigraphic section with the approximate position of the localities. Only the sites situated in the Ifezouane Formation are discussed in the text.
Mentions: The continental or brackish deposits from the early Cenomanian of the Ifezouane Formation, sometimes gathered with the Aoufous Formation within the Kem Kem beds, have yielded a very rich assemblage including terrestrial, aquatic and aerial vertebrates [1]. The fossils are located in outcrops extending along more than 250 kilometres, which marks the landscape as the basement of a cliff over hanged by a calcareous plateau (hamada), which is formed by the limestone Akrabou Formation. The Ifezouane Formation is composed mainly of detritic sandstone characterised by cross-stratified structures and channel structures filled with microconglomerates. The Aoufous Formation is composed mainly of clayey sandstones and green marls with gypsum and contains few fossils, except in the Djbel Oum Tkout locality (also called OT1 assemblage [2]), whose assemblage is not discussed in this paper. The overhanging Akrabou Formation is a calcareous series corresponding to the settlement of marine environment. The shallow marine fish and invertebrate assemblage from Agoult is located at the base of the Formation, in an area that has also yielded vertebrate remains in the underlying Ifezouane Formation (Gara Sbâa). The Goulmima assemblage is located higher in the stratigraphical series and is situated in the northern part of the basin. The Cenomanian-Turonian boundary is located in the lower part of the Akrabou Formation. The Goulmima assemblage is well dated to the early Turonian on the basis of ammonites, but the Agoult assemblage is regarded as either Late Cenomanian or Early Turonian. Fish taxa from both marine localities are not discussed here, except for a comparison of trophic webs of the Goulmima assemblage with the Kem Kem assemblage (see below). The geographical distribution and the approximate stratigraphic location of these assemblages are presented in Fig 1. Description of the succession of the fish assemblages is presented in a recent overview of the Moroccan Post-Palaeozoic bony fish record [3], and here we focus on new material collected in the Ifezouane Fm.

Bottom Line: The Kem Kem assemblage is characterized by taxa of proportionally large body size, and by a higher average trophic level than the trophic level of the extant compared freshwater ecosystems, but lower than for the extant marine ecosystems.These results should be regarded with caution because they rest on a reconstructed assemblage known mostly by fragmentary remains.They reinforce, however, the ecological oddities already noticed for this mid-Cretaceous vertebrate ecosystem in North Africa.

View Article: PubMed Central - PubMed

Affiliation: Département de géologie et paléontologie, Muséum d'histoire naturelle de Genève, CP 6434, 1211, Geneva 6, Switzerland.

ABSTRACT
The mid-Cretaceous vertebrate assemblage from south-eastern Morocco is one of the most diversified continental vertebrate assemblages of this time worldwide. The bony fish component (coelacanths, lungfishes and ray-finned fishes) is represented by relatively complete specimens and, mostly, by fragmentary elements scattered along 250 kilometres of outcrops. Here we revisit the bony fish assemblage by studying both isolated remains collected during several fieldtrips and more complete material kept in public collections. The assemblage comprises several lungfish taxa, with the first mention of the occurrence of Arganodus tiguidiensis, and possibly two mawsoniid coelacanths. A large bichir cf. Bawitius, is recorded and corresponds to cranial elements initially referred to 'Stromerichthys' from coeval deposits in Egypt. The ginglymodians were diversified with a large 'Lepidotes' plus two obaichthyids and a gar. We confirm here that this gar belongs to a genus distinctive from Recent gars, contrary to what was suggested recently. Teleosteans comprise a poorly known ichthyodectiform, a notopterid, a probable osteoglossomorph and a large tselfatiiform, whose cranial anatomy is detailed. The body size and trophic level for each taxon are estimated on the basis of comparison with extant closely related taxa. We plotted the average body size versus average trophic level for the Kem Kem assemblage, together with extant marine and freshwater assemblages. The Kem Kem assemblage is characterized by taxa of proportionally large body size, and by a higher average trophic level than the trophic level of the extant compared freshwater ecosystems, but lower than for the extant marine ecosystems. These results should be regarded with caution because they rest on a reconstructed assemblage known mostly by fragmentary remains. They reinforce, however, the ecological oddities already noticed for this mid-Cretaceous vertebrate ecosystem in North Africa.

No MeSH data available.