Lavocatavis
| Lavocatavis | ||||||||||||
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| Temporal occurrence | ||||||||||||
| Lower to Middle Eocene | ||||||||||||
| 49 to 45 million years | ||||||||||||
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| Scientific name | ||||||||||||
| Lavocatavis | ||||||||||||
| Mourer-Chauviré , Tabuce , Mahboubi , Adaci , Bensalah , 2011 | ||||||||||||
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Lavocatavis is an extinct species of birds from the Phorusrhacidae family("terror birds"). In Algeria , a fossilized femur from the Eocene was found in the Glib-Zegdou formation in 2011and is the only fossil from Lavocatavistoday. The species has been described as Lavocatavis africana .
discovery
The holotype of Lavocatavis , UM HGL 51-55 , consists of an almost complete right femur. The middle section is well preserved, but the ends are damaged. The fossil comes from the HGL 51 layer of the Glib-Zegdou Formation. The genus name "Lavocats Vogel" was given in honor of René Lavocat , the first to describe the geological layer.
The fossil has a circumference of 79 mm in the middle and is 220 mm long. The bone is irregularly cylindrical and has a diameter of 26 mm at the greatest width and 22.3 mm at the narrowest point. Based on this data, conclusions can be drawn about the size of the species and the weight of the species is estimated to be between 32 and 45–50 kg, depending on the method. As with the other terror birds, the thigh was very straight. It is not curved in any direction and only bends slightly forward at the lower end. The popliteal fossa and the medial supracondylar crest are highly developed. The lateral condyle protrudes back and down. In addition, the thigh has a flattened anterior facies articularis antitrochanterica. There is also no developed femoral trochanter. The femoral head is faintly indicated, but the part of the bone is poorly preserved. However, the classification remains preliminary.
Like the Phorusrhacidae, Lavocatavis belongs to the Cariamiformes, but is otherwise not related to them. Common ancestors must have lived before the final collapse of Africa and South America.
Paleobiogeography
The authors of the first description suggest to place the species in the superfamily Phorusrhacoidea. Until then, this superfamily was mainly known from South America, with a genus in North America, Titanis , and some controversial finds from Antarctica . The earliest finds are only around 70 million years old, which means that the family arose after the disintegration of Africa and South America (around 100 million years ago).
The authors therefore propose two hypotheses for the occurrence of this genus in Africa. Both suggest that the birds originally came from South America and later spread to Africa. This was possible because the continents were not as far apart as they are today (about 1000 km). Although there are (controversial) finds of fossils from Antarctica, the possibility that the species reached Africa from there was ruled out, as the two continents were already much further apart (2600 km). Immigration by land is still excluded. Possibly the animals spread by means of driftwood or island hopping . Currents in the old South Atlantic in the early Paleocene flowed westward, making it unlikely that the Phorus Rhacoids came to Africa on floating islands. Perhaps the ancestors migrated Lavocatavis over larger islands along the defunct Rio Grande Rise and Walvis Ridge (Walvis Ridge). Perhaps the ancestors were also partially airworthy. If so, the flightless Lavocatavis would have evolved through convergent evolution.
Individual evidence
- ↑ a b c Cécile Mourer-Chauviré, Rodolphe Tabuce, M'hammed Mahboubi, Mohammed Adaci, Mustapha Bensalah: A phororhacoid bird from the Eocene of Africa. In: Natural Sciences. 2011, vol. 98, 10: 815-823. doi: 10.1007 / s00114-011-0829-5
- ↑ Cécile Mourer-Chauviré et al., 2011.