Youngolepis

  • Yunnan (China)

Youngolepis is an extinct genus of fish from the class of meat -finned fishes ( Sarcopterygii ) which occurred in the Lower Devonian. Fossils of the genus were found in the southern Chinese province of Yunnan. The genus was named in honor of Chinese paleontologist Young Chung Chien.

Features

Youngolepis is a small predator and was less than 30 cm long. The genus is primarily known skull fossils. The skull bones are heavy and thick, the body covered with thick, rhombic Kosmoidschuppen. Snout and outer nostrils point downward, as in Diabolepis. The posterior nares are at the rear end of the small premaxilla. Rostrum and lower jaw are covered with numerous tubes. The eyes were small. Rows of small bones surrounding the main paired cranial bones, a feature which is also found in lungfish ( Dipnoi ). The frontal is long, the parietal shortly. The neurocranium is not completely divided into two sections as in the crossopterygians. Be found on the side of the head a bone plate, consisting of those skull elements that correspond to the squamosal, Quadratojugale and Praeoperculare, and their pattern is reminiscent of the cheekbones of Osteolepiformes. The sutures remain always visible between premaxilla and the head plate formed from frontal and ethmoid. As for the lungs, the Jugale fish is greater than the lacrimal. The parasphenoid is big and long.

The scales are coated with a thick, smooth Cosmi layer and have small pores ( 25-60 microns ). On the lower jaw, the pores are larger ( 75-100 microns ). The pores of the scales are similar to the enamel lined with a Enameloidschicht, a substance, a feature which Youngolepis tells the Porolepiformes. Westoll - lines, more or less concentric lines in the Kosmoidschuppen the lungfish, which are interpreted as growth rings, are missing.

System

Youngolepis is assigned to the Dipnomorpha, the sister group of the Tetrapodomorpha ( tetrapods including their fishy Stammgruppenvetreter ), which also includes the modern lungfish. Youngolepis is the sister taxon of a clade from Diabolepis and the lungfish.

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