Bachmannia chubutensis
| Bachmannia chubutensis | ||||||||||||
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| Temporal occurrence | ||||||||||||
| early Eocene | ||||||||||||
| 55.8 to 48.6 million years | ||||||||||||
| Locations | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name of the family | ||||||||||||
| Bachmanniidae | ||||||||||||
| Azpelicueta & Cione , 2011 | ||||||||||||
| Scientific name of the genus | ||||||||||||
| Bachmannia | ||||||||||||
| Dolgopol , 1941 | ||||||||||||
| Scientific name of the species | ||||||||||||
| Bachmannia chubutensis | ||||||||||||
| Dolgopol, 1941 | ||||||||||||
Bachmannia chubutensis ( Syn .: Arius argentinus Dolgopol 1941) is an extinct fish species from the order of the catfish (Siluriformes). Fossils of the type that are dated to the early Eocene were found in the Laguna del Hunco site, a caldera in the Argentine province of Chubut , whichis filledwith fine-grained, layered mudde and sandstones interspersed with pyroclastic deposits . The genus was named in honor of the German doctor and naturalist Franz Ewald Theodor Bachmann .
Bachmannia chubutensis lived during the climatic optimum of the early Eocene. The Laguna del Hunco was on the southern edge of the tropics, in a humid climate with a clear maritime influence. Volcanic activity with the release of gases into the water resulted in regular mass extinctions of fish.
features
Bachmannia chubutensis was a small species of catfish with a stocky body. The almost completely preserved holotype is 8 cm long (tail fin is missing), the maximum standard length of the species is given as less than 12.5 cm. The head and front body were relatively high. The head profile was convex and is reminiscent of the head shape of the armored catfish genus Corydoras . The neurocranium was severely ossified. In comparison with the mostly small teeth of recent catfish, the teeth of Bachmannia chubutensis were large. They were conical with wide tooth bases. The largest teeth were on the vomer . The maxillary was also toothed (two rows of teeth), a primitive feature for catfish-like, which is only found in the recent Diplomystidae and the extinct Hypsidoridae . The dorsal fin sat between the fifth and thirteenth vertebrae and was supported by a first, short fin spine with a triangular cross-section, a long, second fin spine with longitudinal grooves, and seven soft rays. The anal fin had ten fin rays.
Bachmannia chubutensis is the only known species of the genus Bachmannia and is part of the monotypical family Bachmanniidae, which is the sister group of the primitive catfish (Diplomystidae). A common feature ( synapomorphy ) of Bachmanniidae and Diplomystidae is a double, anterior joint head of the palatine .
literature
- MM Azpelicueta, AL Cione: Redescription of the Eocene Catfish Bachmannia chubutensis (Teleostei: Bachmanniidae) of Southern South America. In: Journal of Vertebrate Paleontology. 31, No. 2, 2011, pp. 258-269, doi: 10.1080 / 02724634.2011.550351 .