Minchinellidae

Minchinellidae is a family of calcareous sponges, members of the class Calcarea.^[1] It is the only family in the monotypic order Lithonida. The families Petrobionidae (genus Petrobiona)^[2] and Lepidoleuconidae (genus Lepidoleucon)^[3] have also sometimes been placed within Lithonida, though more recently they have been moved to the order Baerida.^[4] Thanks to their hypercalcified structure, minchinellids have a fossil record reaching as far back as the Jurassic Period.^[3][4]

Minchinellidae Temporal range: Jurassic–recent PreꞒ Ꞓ O S D C P T J K Pg N
Porosphaera globularis fossil from the Cretaceous of Germany
Scientific classification
Kingdom:	Animalia
Phylum:	Porifera
Class:	Calcarea
Order:	Lithonida Vacelet, 1981
Family:	Minchinellidae Dendy & Row, 1913
Genera
see text.
Synonyms
Bactronellidae Laubenfels, 1955 Petrostomidae Laubenfels, 1936 Porosphaeridae Laubenfels, 1955

Description

Minchinellids are hypercalcified sponges. They have a robust skeleton of tetractine (four-rayed) calcareous spicules. The tetractine spicules are propeller-shaped, with three curved actines (rays) radiating perpendicular to a straight basal actine. These spicules may be linked by their basal actines or cemented together by calcite. The skeleton is reinforced with layers of loose diapason (tuning fork-shaped) spicules. Minchinellid sponges have a leuconoid canal system.^[3][4]

List of genera

• †Bactronella Hinde, 1884 [Jurassic–Miocene, Holocene?]^[3]
• Minchinella Kirkpatrick, 1908 [Holocene]
• Monoplectroninia Pouliquen & Vacelet, 1970 [Holocene]
• †Muellerithalmia Reitner, 1987 [Upper Jurassic]^[3]
• Petrostroma Döderlein, 1892 [Cretaceous–Holocene]
• Plectroninia Hinde, 1900 [Jurassic?, Cretaceous–Holocene]
• †Porosphaera Steinmann, 1878 [Cretaceous]^[3]
• †Porosphaerella Welter, 1911 [Cretaceous]^[3]
• †Retispinopora Brydone, 1912 [Cretaceous–Paleocene]^[3]
• †Sagittularia Welter, 1911 [Cretaceous]^[3]
• Tulearinia Vacelet, 1977 [Holocene]