Açu Formation
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The Açu Formation is an Early Cretaceous (Albian) geologic formation of the Potiguar Basin in Ceará, northeastern Brazil. The formation comprises coarse-grained sandstones deposited in a fluvio-deltaic environment. The Açu Formation, belonging to the Apodi Group, has provided fossils of an indeterminate rebbachisaurid.
Description
The Açu Formation was deposited in a passive margin setting, overlying the Alagamar Formation and is overlain by the Jandaíra Formation. In the petroleum producing Potiguar Basin, the formation is a reservoir rock.
Fossil content
The following fossils were reported from the formation:
| Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon | Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited. | |||||
| Taxon | Reclassified taxon | Taxon falsely reported as present | Dubious taxon or junior synonym | Ichnotaxon | Ootaxon | Morphotaxon |
Dinosaurs
Sauropods
| Sauropods of the Açu Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Rebbachisauridae indet. | Indeterminate | Ceará | Albian | Vertebrae | ||
| Tiamat | T. valdecii | Ceará | Albian to Cenomanian | Caudal vertebrae | A titanosaurian sauropod; closely related to Andesaurus delgadoi. | |
| Titanosauria Indet. | Indeterminate | Ceará | Albian | Osteoderm |
Theropods
| Theropods of the Açu Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Abelisauridae Indet. | Indeterminate | Ceará | Albian to Cenomanian | Teeth & Completed Femur | ||
| Baryonychinae Indet. | Indeterminate | Ceará | Albian | Tooth | A spinosaurid theropod | |
| Carcharodontosauridae Indet. | Indeterminate | Ceará | Albian | Vertebrae | ||
| Megaraptora Indet. | Indeterminate | Ceará | Albian | Vertebrae | ||
| Noasauridae Indet. | Indeterminate | Ceará | Albian to Cenomanian | Teeth | ||
| Paraves Indet. | Indeterminate | Ceará | Albian | Vertebrae | A maniraptoran theropod | |
| Spinosaurinae Indet. | Indeterminate | Ceará | Albian | Tooth | A spinosaurid theropod |
Crocodylomorphs
| Crocodylomorps of the Açu Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Candidodontidae Indet. | Indeterminat | Ceará | Albian to Cenomanian | |||
| Itasuchidae Indet. | Indeterminate | Ceará | Albian to Cenomanian | |||
| Peirosauridae Indet. | Indeterminate | Ceará | Albian | Insolated Tooth | ||
| Sphagesauria Indet. | Indeterminate | Ceará | Albian to Cenomanian |
Fish
| Fish of the Açu Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Arganodus | A. tiguidiensis | Ceará | Albian | Teeth | A arganodontid lungfish | |
| Ceratodus | C. brasilensis | Ceará | Albian | Teeth | A ceratodontid lungfish | |
| Bawitius | B. bartheli | Ceará | Albian | Scales & Tooth | A bichir | |
| Distobatus | D. potiguarense | Ceará | Albian to Cenomanian | A distobatid hybodont | ||
| Lepisosteus | L. sp. | Ceará | Albian to Cenomanian | Scales & Tooth | A gar | |
| Mawsonia | M. gigas | Ceará | Albian to Cenomanian | A mawsoniid coelacanth | ||
| Pycnodontiformes Indet. | Indeterminate | Ceará | Albian | Teeth | ||
| Tharrhias | T. castelhanoi | Ceará | Albian | Scales | A gonorynchiform fish | |
| Tribodus | T. limae | Ceará | Albian to Cenomanian | A hybodont shark | ||
| Vidalamiinae Indet. | Indeterminate | Ceará | Albian |
Crustaceans
| Crustaceans of the Açu Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Unusuropode | U. castroi | Ceará | Albian | A isopod |
Molluscs
Bivalves
| Bivalves of the Açu Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Brachidontes | B. sp. | Ceará | Albian | A mytilid mussel | ||
| Mytilus | M. rosadoi | Ceará | Albian | A mytilid mussel |
Gastropods
| Gastropods of the Açu Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Gastropoda Indet. | Indeterminate | Ceará | Albian |
Echinoderms
| Echinoderms of the Açu Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Echinodermata Indet. | Indeterminate | Rio Grande do Norte | Albian |
Plants
| Plants of the Açu Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Palmoxylon | P. sp. | Rio Grande do Norte | Albian |
Bibliography
- Gomes da Costa Pereira, Paulo Victor; Ribeiro, Theo Baptista; Brusatte, Stephen Louis; Dos Anjos Candeiro, Carlos Roberto; da Silva Marinho, Thiago; Paglarelli Bergqvist, Lilian (2020), (PDF), Cretaceous Research, in press 104517, doi:, hdl:
- Maraschin, Anderson; Mizusaki, Ana Maria P.; Vasconcelos, P.M.; Hinrichs, Ruth (2010), , Pesquisas Em Geociencias, 37: 85–96, doi: