Taxonomy

Phylum:  Porifera Grant,1836

Class:    Demospongea Sollas,1875

Order： Protomonaxonida Finks and Rigby, 2004

Family:  Leptomitidae Laubenfels,1955

Genus：Leptomitella Rigby,1986

Specie: Leptomitella spiralis Chen et Hou,2019

Description:

The body gradually widens from bottom to top, and gradually becomes thin after reaching the maximum width in the middle, in a spindle shape. The body is 60mm high, the widest part is in the middle of the body, which width is 11mm.The  body has two contraction parts: one is located 17mm upward from the fixed end, with a width of 4.9mm，another is located 8.5mm away from the top of the sponge , 3.1mm wide.

The skeleton can be composed of three sets of uniaxial spicules of different sizes: one set is a thick diactines arranged in approximately parallel longitudinally. These spicules are overlapped up and down to form a bone rod structure. The length of the spicules is 6-8mm, the diameter is 0.07-0.08mm, and the spacing is 0.2-0.35mm. The spacing between these large spicules changes in the skeleton, the largest in the middle and gradually narrowed to both ends: the spacing near the top water outlet is 0.1-0.15mm, and the lower part gradually narrows from 0.3mm and is connected at the fixed end. Between these large spicules are filled with smaller longitudinal spicules, which are arranged parallel or approximately parallel to the large spicules, with a length of about 1mm and a diameter of about 0.02-0.03mm. Interlaced with the longitudinal spicules is the transverse diactines. There are two types of transverse spicules: one is clustered into bundles and arranged in two directions in a spiral: the one direction is a left spiral around the body and the other direction is a right spiral around the  body. The spicules bundle is about 5-8 in a bundle with a width of 0.1-0.15mm, which is interspersed with the longitudinal spicules.The spicules bundle generally spans 7-8 longitudinal large bone spicules.The distance between spicules bundles is 0.4-0.55mm, and the whole  spicules bundle is about 120 rows. Single spicules of spicules bundle is 1.2-1.7mm long and 0.025-0.03mm in diameter. The other kind of transverse spicules are evenly distributed, not in bundles, interspersed with longitudinal bone spicules, with a diameter of 0.03-0.04mm and an unobvious length.

The fixed end of the body is conical and has no prostalia basalia. The outlet end is straight, and the edge is formed by transverse spicules bundle without prostalia marginalia.

Age & Localities

Age: Cambrian Series2, Stage3

Principal localities: Chengjiang biota (Yu’anshan Member of the Chiungchussu Formation),eastern Yunan Province,China