Taxonomic Composition and Trophic Structure of the Continental Bony Fish Assemblage from the Early Late Cretaceous of Southeastern Morocco
Résumé
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.
Domaines
Sciences de la TerreOrigine | Fichiers éditeurs autorisés sur une archive ouverte |
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