Trepassia
| Trepassia | ||||||||||||
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| Temporal occurrence | ||||||||||||
| 579 to 560 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Trepassia | ||||||||||||
| Narbonne et al., 2007 | ||||||||||||
Trepassia is an extinct genus from the geological age of the Ediacarium . The fossil iscounted among the sub-tribe of the Rangeomorpha . It represents the oldest known find of the Ediacaran fauna todate.
Etymology and first description
Trepassia was named after the Trepassey Formation in which the fossil occurs. The name of the formation is derived from the place Trepassey , located on the southeast coast of the Avalon Peninsula in Newfoundland . The word Trepassey in turn comes from the French Trépassé with the meaning of deceased, deceased, passed away, soul and refers in particular to the Baie des Trépassés in Brittany .
Trepassia was first scientifically described in 2007 by Guy M. Narbonne and colleagues. Another adaptation was made by Martin Brasier in 2012.
Occurrence and age
Trepassia is only known from its type locality in Newfoundland. The fossil appears for the first time in the Drook Formation from the Conception Group , it is also present in the following formations, Frecal Formation and Mistaken Point Formation, as well as in the eponymous Trepassey Formation , which already belongs to the St. John's Group .
The first appearance of Trepassia in the upper section of the Drook Formation has been determined to be 578.8 ± 0.3 million years BP . The last appearance in the lower third of the Trepassey Formation was not directly dated, but must be a little younger than 565 ± 3 million years BP.
Taxonomy
Trepassia was by Douglas Erwin and colleagues (2011) for the tribe rangeomorph asked. The genera Charnia and Vinlandia (Charnidae) as well as Beothukis are very close to the taxon belonging to the Avalon Fauna Community . Slightly more distant sister taxa are Avalofractus , Fractofusus , Frondophyllas , Hapsidophyllas , Khatyspytia , Protocharnia , Rangea and Vauzutsinia . The only previously known subtaxon is Trepassia wardae .
features
According to the classification scheme for Rangeomorpha by Brasier, Antcliffe and Liu (2012), Trepassia can be described as follows:
Trepassia was able to reach the proud height of at least 2 meters above the sea floor, but smaller embryonic forms in the millimeter range are also known.
A stalk emerged from a unipolar growth center above an adhesive disc or a bulbous anchorage (in contrast, for example, to the bipolar genus Fractofusus with two growth centers). To him sat a very slender, farnblattähnlicher Wedel ( English frond ) on. The stem ended in a single point. The narrow frond itself was in two rows, the two rows running almost parallel to one another and meeting in a straight line in the axis of the stem. Overall, the organism resembled a cypress .
The primary side branches branched off at an angle of about 45 ° on both sides, once to the right and then again to the left of the central stem ( glide mirror symmetry ), which, however, was mostly covered by the curling of the two rows of fronds. Trepassia was fractal organized and up into the third dimension self-similar , that is from the primary side branches to secondary branches with split secondary fronds (English frondlets ab), which in turn branched again and, moreover, were rolled up on the edges. The primary side branches were parallel and roughly the same length. The secondary and tertiary side branches were also predominantly oriented in parallel, but could also fan out slightly. Their length was slightly increased in the central area.
The secondary fronds ("rangeomorphic elements"), built like a quilted air mattress, were, in contrast to other Rangeomorpha such as Bradgatia , rotated by 90 ° in relation to the stem axis. However, the branching pattern of the third order remained mostly hidden and can only be seen in unusually oriented finds.
Individual evidence
- ^ A b c G. M. Narbonne, M. Laflamme, C. Greentree and P. Trusler: Reconstructing a lost world: Ediacaran rangeomorphs from Spaniard's Bay, Newfoundland . In: Journal of Paleontology . tape 83 (4) , 2007, pp. 503-523 .
- ^ A b M. D. Brasier, AD Antcliffe and AG Liu .: The architecture of Ediacaran fronds . In: Palaeontology . tape 55 (5) , 2012, p. 1105-1124 .
- ^ Van Kranendonk, MJ, Gehling, JG and Shields, GA: Precambrian . Ed .: Ogg, JG, Ogg, G. and Gradstein, FM, The Concise Geologic Time Scale. Cambridge University Press, Cambridge 2008, pp. 23-36 .
- ^ Erwin, D. et al.: The Cambrian conundrum: early divergence and later ecological success in the early history of animals . In: Science . tape 334 (6059) , 2011, pp. 1091-1097 .