Otavia
| Otavia | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Otavia antiqua |
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| Temporal occurrence | ||||||||||||
| Cryogenium to Ediacarium | ||||||||||||
| 760 to 550 million years | ||||||||||||
| Locations | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Otavia | ||||||||||||
| Brain , Prave , Hoffmann , Fallick , Botha , Herd , Sturrock , Young , Condon & Allison , 2012 | ||||||||||||
Otavia antiqua is a round to irregular, phosphatized microfossil that was found in Namibia in rocks 760 to 550 million years old. The oldest Otavia fossil comes from the Otavi Group (Ombombo Supergroup (Okakuyu Formation)), which lies between a layer formed from volcanic ash, which is dated to an age of 760 ± 1 million years, and which is about 710 million years ancient Chuos formation, which was deposited during an ice age. Middle-aged finds are from the Ombaatjie and Auros formations, phases of ice melt, which are dated to an age of 635.5 ± 1.2 million years. The stratigraphically youngest known Otavia fossils were found in rocks of the Nama group (Zaris formation) with layers below an ash layer dated to an age of 548.8 ± 1 million years.
Otavia developed before the glaciation known as snowball earth in the Neo Proterozoic and survived this period of climatic extremes. The oldest fossils from Otavia , which is regarded as a spongy organism, date the emergence of the multicellular animals ( Metazoa ), estimated to date from 600 to 650 million years ago, about 100 to 150 million years further in the past.
features
Otavia antiqua is spherical, oval to irregular in shape and has a diameter of 0.3 to 5 mm. The outer surface is perforated with numerous small to large openings. The size of these openings is in the micrometer range. The outer skin is thin (many to a few tens of micrometers thick) and typically contains calcium phosphate . The openings lead into an irregularly shaped and longitudinally extending inner cavity. These features are interpreted as ostia and gastric space.
criticism
As with all Proterozoic sponge fossils, the assignment is speculative and uncertain in this case. Definitive characteristics of the assignment to the Porifera (or the Metazoa in general) are missing and are based mainly on negative evidence (missing characteristics). Even the biogenic origin of the structures has by no means been proven. A more recent revision only classifies them as calcium phosphate grains whose surface has been roughened by sediment movement.
literature
- CK Brain, AR Prave, KH Hoffmann et al: The first animals: approx. 760 million-year-old sponge-like fossils from Namibia . In: South African Journal of Science. 108 (1/2), 2012, pp. 83-90. ISSN 1996-7489
- Robert W. Gess: The oldest animal fossils. In: South African Journal of Science. January / February 2012. doi: 10.4102 / sajs.v108i1 / 2.1064
Individual evidence
- ↑ JB Antcliffe, RHT Callow, MD Brasier: Giving the early fossil record of sponges a squeeze. In: Biological Reviews. 2014. doi: 10.1111 / brv.12090 (full text) .