Acrotretida

Acrotretida is an extinct order of linguliform brachiopods in the class Lingulata. They lived from the Lower Cambrian to the Middle Devonian, with their peak diversity from the Middle Cambrian to the Ordovician. Acrotretida contains the sole superfamily Acrotretoidea.[1][2]

Acrotretida
Temporal range:
Diagram of Eohadrotreta zhenbaensis, a Lower Cambrian member of the family Acrotretidae
Scientific classification e
Kingdom: Animalia
Phylum: Brachiopoda
Class: Lingulata
Order: †Acrotretida
Kuhn, 1949

Many acrotretides have a tall and conical ventral valve with a pedicle opening at the apex, while the dorsal valve was convex to a much lesser degree. Based on preserved muscle scars, the lateral muscles are shifted back and condensed into large bundles of tendons. These replace the stout, column-like central muscles, which are present in other linguliforms but apparently absent in acrotretides. The larval shell, which is retained near the pedicle opening, has a strongly pitted texture. The adult shell is smooth and has a rounded outline, and is phosphatic like other linguliforms.[1]

Subgroups
  • Incertae sedis
    • Craniotreta Termier & Monod, 1978
    • Dzhagdicus Sobolev, 1992
    • Schizotretoides Termier & Monod, 1978

References
  1. Williams, Alwyn; Brunton, C.H.C.; Carlson, S.J.; et al. (1997–2007). Roger L. Kaesler (1997–2006); Paul Selden (2007) (eds.). Part H, Brachiopoda (Revised). Treatise on Invertebrate Paleontology. Boulder, CO; Lawrence, KS: Geological Society of America.
  2. Holmer, L. (1991). "Phyletic relationships within the Brachiopoda". GFF. 113: 84. doi:10.1080/11035899109453832.


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