Mahengechromis

from Wikipedia, the free encyclopedia
Mahengechromis
Temporal occurrence
Middle Eocene
46.3 to 45.7 million years
Locations
Systematics
without rank: Perch relatives (Percomorphaceae)
Ovalentaria
Order : Cichliformes
Family : Cichlids (Cichlidae)
Subfamily : Pseudocrenilabrinae
Genre : Mahengechromis
Scientific name
Mahengechromis
Murray , 2000

Mahengechromis is an extinct genus of cichlids , of which over 150 often very well preserved fossils have been found near the city of Mahenge in Tanzania . The fossils were dated to the Middle Eocene (46.3 to 45.7 million years ago), making them the oldest cichlidfossils. The site is an almost circular former crater lake with a diameter of 400 m, similar to the Barombi Mbo in Cameroon . The generic name is composed of the names of the type locality and Chromis together a Riffbarschgattung , formerly cichlids were classified under. A total of five species have been described. In addition to the type species M. plethos, there are also M. rotundus, M. brachycranium, M. ellipticus and M. curvifrons .

features

The fossils found have a standard length of 29 to 64 mm, with the head making up 28 to 39% of the standard length. This made the Mahengechromis species one of the smallest species of cichlids. The body height reaches 35 to 47% of the standard length. Since all specimens were fossilized in a lateral position , it is assumed that the animals were relatively flattened laterally. The tail stalk is short and approximately square. Its height is slightly greater than its length. Mahengechromis and all other African cichlids differ from Heterochromis , the basal sister genus of all other African cichlids, and from Tylochromis , another original African cichlid genus, by a single predorsal bone ( Heterochromis and Tylochromis have two). Mahengechromis's body was covered with comb scales. Round scales covered the gill cover , the gill cover , the throat and other parts of the head region and are found between the rays of the caudal fin. The jaw and palate teeth were single-pointed. The number of vertebrae is relatively low at 22 to 25. The upper sideline is not fully developed. Some of their scales only had a single pore.

literature