“Romualdo Formation”的意思、由来-开放百科全书

The Romualdo Formation is a geologic Konservat-Lagerstätte in northeastern Brazil's Araripe Basin where the states of Pernambuco, Piauí and Ceará come together. The geological formation, previously designated as the Romualdo Member of the Santana Formation, named after the village of Santana do Cariri, lies at the base of the Araripe Plateau. It was discovered by Johann Baptist von Spix in 1819. The strata were deposited during the Albian stage of the Early Cretaceous in a lacustrine rift basin with shallow marine incursions of the proto-Atlantic. At that time, the South Atlantic was opening up in a long narrow shallow sea.

The Romualdo Formation earns the designation of Lagerstätte due to an exceedingly well preserved and diverse fossil faunal assemblage. Some 25 species of fossil fishes are often found with stomach contents preserved, enabling paleontologists to study predator–prey relationships in this ecosystem. There are also fine examples of pterosaurs, reptiles and amphibians, invertebrates (particularly insects), crocodylomorphs, and plants. Even dinosaurs are represented (Spinosauridae, Tyrannosauroidea, Compsognathidae). The unusual taphonomy of the site resulted in limestone accretions that formed nodules around dead organisms, preserving even soft parts of their anatomy. In preservation, the nodules are etched away with acid, and the fossils often prepared by the transfer technique.^[1]

Local mining activities for cement and construction damage the sites. Trade in illegally collected fossils has sprung up in the last decade, driven by the remarkable state of preservation and beauty of these fossils and amounting to a considerable local industry. An urgent preservation program is being called for by paleontologists.

In addition, the weathering of Romualdo Formation rocks has contributed soil conditions unlike elsewhere in the region. The Araripe manakin (Antilophia bokermanni) is a very rare bird that was discovered only in the late 20th century; it is not known from anywhere outside the characteristic forest that grows on the Chapada do Araripe soils formed ultimately from Romualdo Formation rocks.

Geology and dating

The Crato Formation was previously considered the lowest member of the then Santana Formation, but has been elevated to a formal formation. The Crato Formation is the product of a single phase, where complicated sequence of sediment strata reflect changeable conditions in the opening sea. The age of the Romualdo Formation, formerly known as the Romualdo Member of the Santana Formation, has been controversial, though most workers have agreed that it lies on or near the Aptian-Albian boundary, about 112 million years ago. Nevertheless, a Cenomanian age cannot be ruled out.^[2]^[3]

The extent of the Crato unit and its relationship to the Romualdo Formation had long been ill defined. It was not until a 2007 volume on the unit by Martill, Bechly and Loveridge that the Crato Formation was given a formal type locality, and was formally made a distinct formation separate from the Romualdo Formation, which is about 10 Ma younger.^[2]

Fossil content

Archosaurs

Indeterminate remains of non-avian theropods, avialans, ornithischians, and possibly oviraptorosaurs have been found in Estado do Ceara, Brazil.^[5] The oviraptorosaurian remains have been re-identified as megaraptoran fossils.^[4]

A more complete specimen, AMNH 24450, is at the American Museum of Natural History.

Pterosaurs

Turtles

Fish

See also

References

1. ^Maisey et al., 1991, pp.99-103
2. ^¹Martill et al., 2007
3. ^Martill, 2007
4. ^{{Cite journal|last=Aranciaga Rolando|first=Alexis M.|last2=Brissón Egli|first2=Federico|last3=Sales|first3=Marcos A.F.|last4=Martinelli|first4=Agustín G.|last5=Canale|first5=Juan I.|last6=Ezcurra|first6=Martín D.|date=2018|title=A supposed Gondwanan oviraptorosaur from the Albian of Brazil represents the oldest South American megaraptoran|url=https://www.sciencedirect.com/science/article/pii/S0195667117303051|journal=Cretaceous Research|language=en|volume=84|pages=107–119|doi=10.1016/j.cretres.2017.10.019|issn=0195-6671|via=}}
5. ^¹²³⁴⁵⁶⁷⁸⁹¹⁰¹¹¹²Weishampel, 2004, pp. 563–570
6. ^"Table 4.1," in Weishampel, et al. (2004). Page 73.
7. ^"Table 5.1," in Weishampel, et al. (2004). Page 114.
8. ^Elgin & Frey, 2011
9. ^Santanachelys gaffneyi at Fossilworks.org
10. ^Juazeiro do Norte at Fossilworks.org
11. ^Araripemys barretoi type locality at Fossilworks.org
12. ^Crato at Fossilworks.org
13. ^¹²³⁴⁵⁶Chapada do Araripe at Fossilworks.org
14. ^Casa de Pedra at Fossilworks.org
15. ^¹²³⁴⁵⁶Fara et al., 2005, p.152
16. ^Buxéxé, Santana do Cariri at Fossilworks.org
17. ^Enneles audax
18. ^Iemanja palma
19. ^Placidichthys type locality at Fossilworks.org
20. ^Ze Gomes at Fossilworks.org

Bibliography